ObservatioNs of Fire’s Impact on the southeast atlantic REgion (ONFIRE)

Scientific Program OverviewPrincipal Investigator Paquita Zuidema U of Miami/RSMAS, Miami, FL pzuidema@rsmas.miami.edu, tel: 305-421-4276, fax: 305-421-4696

and ONFIRE Scientific Working GroupJames Anderson, Arizona State U., Tempe; Elliot Atlas, U of Miami; Roya Bahreini , U. of California, Riverside; Byron Blomquist, U of Colorado, Boulder; Peter Bogenschultz, NCAR; Jerome Brioude, U. of Colorado, Boulder; Teresa Campos, NCAR; Patrick Chuang, U. of California, Santa Cruz; Chris Fairall, NOAA, Boulder, CO; Ian Faloona , U. of California, Davis; Graham Feingold, NOAA/ESRL, Boulder, CO; James Haywood, UK Met Office/Exeter; Gregoy Jenkins, Howard U.; Jorgen Jensen, NCAR; David Leon, U. of Wyoming, Laramie; Andreas Macke, IFT, Leipzig, Germany; Roberto Mechoso, UCLA; Brian Medeiros, NCAR; Patrick Minnis, NASA-Langley; Roberto Mechoso, UCLA; Daniel Murphy, NOAA/ESRL, Boulder, CO; Shane Murphy, U. of Wyoming, Laramie; David Noone, Oregon State University; David Rahn, U of Kansas; Jens Redemann, NASA-Ames; Greg Roberts, Scripps, La Jolla, CA; Sebastian Schmidt, U. of Colorado, Boulder; Joshua Schwarz, NOAA, Boulder, CO; James Smith, NCAR; Jeffrey Snider, U. of Wyoming, Laramie; Amy Solomon, U of Colorado; Darin Toohey, University of Colorado-Boulder; Cynthia Twohy, Northwest Research Associates; Zhien Wang, U of Wyoming, Laramie; Eric Wilcox, University of Nevada; Robert Wood, U. of Washington, Seattle.

January 14, 2015

ONFIRE

Space-based lidar aerosol ‘curtains’ overlaid on MODIS imagery

PROJECT SUMMARYSouthern Africa is the worlds largest emitter of biomass burning aerosols. Their westward transport over the remote southeast Atlantic ocean co-locates some of the largest planetary aerosol loadings with the least examined of the Earth’s major stratocumulus decks. While much of the aerosol resides above the boundary layer cloud, free-tropospheric subsidence and marine boundary layer deepening as sea surface temperatures warm imply that absorbing aerosol can also be entrained into the boundary layer. Model representations of the solar-absorbing aerosol-cloud-atmosphere-ocean system must consider not only the direct radiative effect, but also radiative changes arising from cloud adjustments to the atmospheric warming and from aerosol-cloud microphysical interactions. ONFIRE (ObservatioNs of Fire’s Impact on the southeast atlantic REgion) will study the key aerosol-cloud-radiation interactions within this natural laboratory towards improving model representations of globally-relevant processes. ONFIRE has as a focal point an intensive five-week (September 2017) deployment of the NSF C-130 plane on Sao Tome island (00 N, 6.50 E). This ideally and uniquely situates the aircraft near the latitude of maximum aerosol outflow located at 100 S and near the stratus-to-cumulus transition region yet able to access the heart of the stratocumulus region, allowing the detailed, comprehensive, and unprecedented sampling of a full range of aerosol-cloud interactions. The gathered datasets will support a wide range of modeling activities, including large-eddy-scale simulations, regional scale nested-WRF simulations and Lagrangian particle tracing, single-column models, and climate model parameterization testbeds. ONFIRE is part of a funded, coordinated, international and multi-agency effort that includes the June, 2016 - May, 2017 DOE AMF1 LASIC deployment to Ascension Island (14.50 W, 80 S), and the multi-year (2016-2018) NASA ORACLES and 2016 UK CLARIFY aircraft experiments based in Namibia. Further ONFIRE observations in 2017 include deployment-long 8X daily radiosonde launches from Ascension Island and St. Helena (50 W, 150 S). A coordinated set of hypotheses improves understanding of biomass burning aerosol composition and absorption, their relationship to cloud-top entrainment, and impact on cloud microphysics. The three primary hypotheses are: 1) The composition of African aerosol over the south Atlantic is highly variable but as the aerosol ages offshore its single-scattering albedo approaches a single consistent value.2) Low cloud properties over the south Atlantic are sensitive to warming aloft and surface dimming by absorbing aerosol. The magnitude of this sensitivity and the responsible mechanisms depend on the altitude and optical properties of the absorbing aerosol and can be distinguished from meteorological effects. 3) South Atlantic boundary layer CCN can be dominated by BB aerosols entrained from higher altitude plumes. These aerosols can significantly alter cloud microphysics, precipitation susceptibility, and cloud mesoscale organization. Intellectual Merit: The absorbing-aerosol-above-cloud regime remains poorly characterized and poorly understood, as demonstrated by the wide diversity in modeled effective radiative forcings for the southeast Atlantic. This emphasizes the most recent IPCC statement that aerosol-cloud interactions are the dominant uncertainty within estimates of future climate. The state-of-the-art ONFIRE datasets will support process studies and parameterization development that can accelerate coupled model improvement. The in-situ datasets further constrain satellite retrievals and promote retrieval development for a region with significant remote sensing challenges.Broader Impact: Field campaigns focusing on the marine boundary layer are critical for developing more realistic climate model parameterizations, and for maintaining a pathway for developing necessary expertise and collaborative skill, particularly for early-career scientists and graduate students. ONFIRE includes local/regional outreach efforts fostering involvement, and video documentation will communicate the excitement of the field project to a wide audience.

Section D: PROJECT DESCRIPTION1. Scientific Rationale and Background 1.1: Large-scale circulation and climate model representation

The southeast Atlantic is influenced by complex and myriad processes associated with the Atlantic basin and the African and American climates. At near-surface levels, winds rotate anticyclonically around the south Atlantic high, encouraging a coastal upwelling that supports one of the richest fisheries on the planet (Cury et al., 2000). The lower free-tropospheric winds, in contrast, are primarily driven by the deeper anticyclone based over southern Africa. Near-equatorial easterlies curve southward over the southeast Atlantic (SEA), combining with cool sea surface temperatures (SSTs) to encourage the formation of a large stratocumulus deck. The SEA net cloud radiative forcing is a global maximum, on par with that of the southeast Pacific (SEP) despite the SEA deck’s smaller total size (Lin et al., 2010). The SEA low cloud deck is much larger relative to its basin than the southeast Pacific (SEP) deck (Fig. 1a), with its transition into trade-wind cumulus reaching the American continent. The processes affecting the SEA stratocumulus deck are closely linked in myriad ways to both the African and South American monsoons, and to land, ocean, and atmosphere processes.

The low stratocumulus decks reduce the amount of sunlight reaching the cooler upwelling waters below, with almost all climate models produce too few low clouds (Pincus et al., 2008; de Szoeke et al., 2010, 2012 Kay et al., 2012; Lauer et al., 2013). The excess solar radiation at the ocean surface reinforces any SST bias regardless of the bias origin. The SST bias is such that coupled global climate models cannot reproduce the basic equatorial Atlantic climate (e.g., Toniazzo and Woolnough, 2013). Similarity between coupled and fixed-SST simulations suggest cloud model errors primarily reflect issues with the representation of cloud processes. In the NCAR climate model, improvements to the shallow boundary layer scheme have slightly improved the SST model bias (Fig. 1b), but the stratocumulus deck still transitions too quickly into cumulus (Medeiros, 2011). Interest in improving low cloud model representations is high also because improved low cloud representations will improve climate change predictions. Uncertainty in the sign and magnitude of the low cloud feedback is the prime uncertainty in the net radiative feedback from all cloud types (IPCC, 2013), with one estimate of the local cloud feedbacks showing the largest variation globally over the southeast Atlantic (Soden and Vechi, 2011).

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Fig 1: a) September-mean SST and cloud fraction highlight differences between the southeast Pacific and Atlantic climate. SST from 1998-2013 Thematic Microwave Imager (labeled colored contour lines) and low cloud fraction from 2000-2012 Moderate Resolution Imaging Spectroradiometer (MODIS; grey shading spans 0.6-1). Land topography in 1 km height increments. b) SST biases of the NCAR CCSM4 (top panel) and CESM1-CAM5 model (bottom panel) with respect to the Reynolds climatology (Neale et al., 2013) highlights incremental improvement in the subtropical stratocumulus regions.

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1.2: Biomass-burning aerosol-cloud interactionsThe largest uncertainty to total radiative forcing estimates in global models stems from

aerosols (IPCC, 2013). The largest consumption of biomass by fire in the world occurs in Africa (van der Werf et al., 2006; 2010; Granier et al., 2011). Remarkable and poorly-understood interactions with low clouds originate with the outflow of the biomass burning (BB) aerosol from Africa over the Atlantic ocean (Fig. 2). Africa thus contributes the global majority of absorbing aerosols overlying clouds (Waquet et al., 2013). The shortwave-absorbing outflow is accompanied with warm continental air, and, combined with the cool austral spring SSTs, a September annual maximum in the lower tropospheric stability is established (Richter and Mechoso, 2004). The BB aerosol center of mass is located approximately 50 to the north of the low-cloud-fraction center of mass, with the aerosol extending into the trade-wind cumulus region. 1.2.1: Direct radiative effect (DRE)

At the top of the atmosphere, the DRE of the biomass burning aerosol is positive (a warming) when the aerosol is located above a bright cloud deck, and negative (a cooling) when above a dark ocean surface (e.g., Remer, 2009). For an aerosol single-scattering albedo (SSA) of 0.9, the cloud fraction above which the aerosol exerts an overall warming is approximately 0.4 (Russell et al., 1997; Abel et al., 2005; Chand et al., 2009; Seidel and Popp, 2012). The aerosol radiative forcing is extremely sensitive to the BB aerosol SSA and the literature does not agree on representative values (Haywood et al., 2004; Leahy et al., 2007; Magi et al., 2008; Chand et al., 2009), in part because the SSA is also a function of the aerosol age and fuel type (Abel et al., 2003; Eck et al., 2013; Bond et al., 2013; Waquet et al., 2013) as well as particle size. Few measurements originate from the remote Atlantic where the smoke’s ability to warm climate occurs.

The DRE magnitude of the transported aerosol remains uncertain and poorly modeled. The few existing observationally-based estimates exceed modeled values (e.g., Yu et al., 2006). de Graaf (2012) used high spectral resolution satellite data to show that the instantaneous DRE of BB aerosol over clouds in the SE Atlantic region can exceed +130 W m-2 instantaneously, and +23 Wm-2 in the monthly mean (de Graaf, 2014). These values are far higher than those diagnosed in climate models, whose monthly-mean values reach only +5W m-2 (Fig. 3; Myrhe et al., 2013; Stier et al., 2013). This suggests a universal model underestimate, perhaps because the underlying low cloud albedo is not bright enough. Interest in assessing global model differences has led to the AeroCom project, an open call to aerosol modeling groups to compare their models using identical setups and, in Phase 2, with identically prescribed aerosol radiative properties (Schulz et al., 2006; Stier et al., 2013; Myrhe et al., 2013). AeroCom top-of-atmosphere (TOA) results to date highlight that, in the mean, the largest positive TOA forcing occurs in the southeast Atlantic, but, that this region also exhibits large differences in magnitude and sign between reputable models consistent with high

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Fig. 2: During September, 600 hPa winds escort the BB aerosol (optical depth in warm colors) from fires in continental Africa (green to red, firecounts) westward over the entire south Atlantic stratocumulus deck (cloud fraction in blue contours). The inset, a 4E-7E longitude slice, highlights the main aerosol outflow occurring at 10S, subsiding to the north where the boundary layer also deepens. Main figure is based on MODIS 2002-2012 data and the ERA-Interim Reanalysis, inset is based on the space-based Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) and CloudSat 2006-2010 data.

variability in the underlying model cloud distributions (Fig. 3). Regional forcings on the Atlantic equatorial sea surface temperature, wind patterns and precipitation can impact the global climate, contradicting the conclusion from the most recent IPCC report, that globally BB aerosol exerts a neutral global direct radiative forcing of -0.1 to +0.1 Wm-2 (Boucher et al., 2013; see also Ramanathan and Carmichael, 2008).

1.2.2: Cloud adjustments to aerosol shortwave absorption (semi-direct effect)Cloud adjustments to the aerosol have not yet been included into the AeroCom exercises,

with such an intercomparison currently being prepared. Cloud adjustments to aerosol-induced atmospheric warming depend crucially on the relative vertical location of the BB aerosol and the cloud deck. When the smoke is situated directly above the cloud field, the stabilization of the atmosphere through warming further supports the cloud field, thickening the cloud and increasing the cloud fraction (Johnson et al., 2004). Such a cloud adjustment appears to find observational support in satellite analyses (Loeb and Schuster, 2008; Wilcox 2010; 2012). The enhanced cloudiness constitutes a potentially substantial contribution to the net surface radiative forcing from that of the aerosol alone, capable of increasing the surface cooling from ~0.2K to 2K (Sakaeda et al., 2011). An almost-unexplored process issue, however, is the mechanism by which atmospheric warming and aerosol scattering that is maximized at the level of maximum aerosol density at ~650 hPa, is transmitted to the boundary layer cloud residing ~200 hPa below. To do so requires measurements of the cloud-top entrainment and turbulent kinetic energy and surface fluxes. The impact of shortwave attenuation by aerosol scattering upon the cloudy boundary layer, for example by discouraging decoupling within the boundary layer, should also be considered. If the BB aerosol is located within the cloudy boundary layer, the shortwave absorption warms the cloud and surrounding atmosphere, lowering the relative humidity and thereby the cloudiness (Ackerman et al., 2000; Johnson et al., 2004; Hill and Dobbie, 2008; Koch and Del Genio, 2010). Thus, how cloudiness responds to the presence of absorbing aerosol depends sensitively on where the aerosol is located, the magnitude of the aerosol loading, and the process mechanism. Aerosol-cloud adjustments are also tightly coupled to meteorology (e.g., Wang and McFarquhar, 2008; Painemal and Zuidema, 2010; George and Wood, 2010; Petters et al., 2013; Adebiyi et al., 2014), arguably even more so when large-scale free-tropospheric heating can influence regional circulation and precipitation patterns (Jones et al., 2009, Randles and Ramaswamy, 2009; Sakaeda et al., 2011).1.2.3: Cloud adjustments to aerosol-cloud microphysical interactions (indirect effects)

BB aerosols can become entrained into the cloudy boundary layer when cumulus clouds overshoot the trade-wind inversion or when subsidence drives the aerosol layers downward into

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Fig. 3: Estimates of the August-September top-of-atmosphere direct radiative forcing from 12 global aerosol models with prescribed radiative properties (Stier et al., 2013) highlight that a) the largest positive forcing is in the southeast Atlantic, but b) model results vary significantly, c) in part because of differences in cloud fraction.

contact with the lower cloud. If BB aerosol do become entrained, they can function as effective cloud condensation nuclei (CCN; Andreae and Rosenfeld, 2008) once the aging and mixing of black carbon (BC) with other aerosols has increased its hygroscopicity. Results from the Southern African Regional Science Initiative (SAFARI-2000) campaign indeed suggest that CCN increase in aged BB plumes (Ross et al., 2003). The activated aerosol can then provide a radiative forcing through their reduction of the mean dropsize, all else held constant (Twomey, 1977). The clearest evidence of altered microphysics from BB aerosol is provided within Constantino and Breon (2010; 2013) and Painemal et al., 2014. The activated aerosol can also ultimately affect the likelihood of precipitation (e.g., Feingold and Siebert, 2009; Wang et al., 2012; Terai et al., 2012). Precipitation susceptibility estimates are not yet known reliably for clouds impacted by long-range BB aerosol transport, in part because of remote sensing challenges (e.g., Sorooshian et al., 2009). Radiative compensations can reduce the impact from these indirect effects and include cloud thinning (Ackerman et al., 2004; Wood et al., 2011), reduction in cloud fraction (Xue et al., 2008; Small et al., 2009), and altered mesoscale organization (Berner et al., 2013; Kazil et al., 2013). There is some suggestion that more polluted coastal clouds in the southeast Atlantic are also thinner (Constantino and Breon, 2013), similar to the southeast Pacific (Bretherton et al., 2010; Painemal and Zuidema, 2010; Twohy et al., 2013). Such buffering effects (Stevens and Feingold, 2009) call further attention to the cloud-top entrainment and boundary layer processes, for which in-situ observations are key (e.g., Faloona et al., 2005; Carman et al., 2012) as well as adequate controls for meteorology. Indirect forcing estimates by global models are still evolving, with Carslaw et al. (2013) estimating a -1.1 W m-2

indirect forcing associated with a three-fold increase in BB aerosol emissions between 1750 to 2000. For BB aerosol, the indirect effects must be compared in relative magnitude against at times opposing semi-direct effects, for example if clouds are brightened as their dropsizes decrease, but overall cloud fractions decrease (McFarquhar et al., 2004b; Johnson, 2005; Zuidema et al., 2008). Lack of confidence in the amount of mixing of BB aerosol into the boundary layer provides a major challenge to large-scale modeling studies of BB aerosol-cloud interactions.1.3. Issues in Biomass Burning Aerosol Research

The comprehensive review of Bond et al. (2013) provides an effective summary of the state-of-the-art of research into the role of black carbon in the climate. Key points relevant to ONFIRE are: 1. Most of the black carbon (BC) emanating from Africa is released by the open burning of

grasslands, and is accompanied by large organic aerosol components that also contribute to shortwave absorption, with the fractional attribution poorly known. BC is by far the most strongly absorbing aerosol, with a mass absorption cross section of approximately 7.5 m2 g-1 at 550 nm, compared to 1 and 0.01 m2 g-1 for brown carbon and dust, respectively. The mass absorption cross-section for BC increases by approximately 50% as the BC becomes internally mixed with other aerosols. The other aerosols, particularly the organic aerosols, coalesce with the BC during transport, increasing its hygroscopicity and thereby BC’s effectiveness as CCN. Cloud processes such as activation and vapor condensation upon the particles in turn affect the aerosol mass, and feedback further into the ability of the aerosol to act as CCN.

2. The composition of emissions from southern Africa is poorly known, with incomplete combustion the norm and mineral dust also present.

3. The evolution (“aging”) of the net radiative properties of BB aerosol is poorly known.4. The transport and eventual deposition patterns of BB aerosol are poorly known, and are

influenced by the vertical location of the BB aerosol. Those properties of the BB aerosols needed to model the direct radiative forcing include the

mass absorption and scattering cross-sections and mass concentrations. Small changes in aerosol SSA have a disproportionate impact on the sign of the net TOA radiative forcing (e.g., Haywood and Shine, 1995), and the variable nature of the SEA aerosol SSA is worth highlighting, with surface-based sun photometer SSA measurements (AERONET; Holben et al., 2001) varying from 0.85 to near 0.9, thought to reflect changes in fuel load (Eck et al., 2013). Results from SAFARI indicate a

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large range of continental source regions contribute to the remote Atlantic CCN (Swap et al., 1996), with multiple stable layers (Garstang et al., 1996) discouraging vertical mixing.2. ONFIRE goals and testable hypotheses

The lack of understanding of the interactions between the south Atlantic low clouds and the biomass burning aerosol outflow from continental Africa is a fundamental issue affecting our ability to model the climate of our planet. In-situ datasets with which to characterize absorbing aerosol-cloud-SST interactions are almost non-existent, as is larger-scale thermodynamic information, as is a coordinated modeling program cutting across all scales. ObservationNs of Fire’s Impact on the southeast Atlantic Region (ONFIRE) thus concerns itself with understanding BB aerosol impacts after their initial transport to the southeast Atlantic has occurred, rather than with characterizing the aerosols at their emission sources. ONFIRE gathers observational datasets that support further process and parameterization testbed studies. The studies are organized around the following questions: 1) What is the composition of the aerosol over the southeast Atlantic and what are its absorption properties? 2) How does shortwave absorption by the aerosol influence low cloud properties and through what mechanisms? 3) What is the entrainment flux of the aerosol into the cloudy boundary layer, and what are the thermodynamical and microphysical consequences? 4) How does the boundary layer thermodynamic structure vary diurnally and can this knowledge help improve low cloud representations in climate models? We propose to address these questions through a combination of field work and modeling, with the roles of individual participants and ONFIRE partners detailed within the Supplementary Documents. The questions can be restated through the following hypotheses and objectives.Science Objectives1. To characterize the aerosol composition, size distribution, and absorption and scattering

properties.2. To characterize the cloudy boundary layer as a function of both aerosol and the larger-scale

meteorological environment.3. To quantify cloud-top entrainment and the free-tropospheric vertical velocity as a function of BB

aerosol loading.4. To characterize semi-direct and indirect effects.5. To acquire datasets that help improve modeled boundary-layer cloud representations.The first four science objectives address the following three hypotheses. The last objective is integral to the ONFIRE modeling plan and an important resource for global modeling centers.

2.1 Observational approach and context Intensifying interest in the smoke-above-cloud regime has motivated a funded, international

and multi-agency (NASA, DOE and the UK Met Office) synergistic effort beginning in 2016. The UK CLARIFY (CLoud-Aerosol-Radiation Interactions and Forcing: Year 2016; PI James Haywood) experiment will use data gathered by the FAAM BAe-146 plane during August-September 2016 to improve smoke-cloud representations within the UK Met Office model. CLARIFY will also support additional radiosondes and instrumentation on St. Helena Island (50W, 150S), located to the west of

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Hypothesis 1 (H1): The composition of African aerosol over the south Atlantic is highly variable but as the aerosol ages offshore its single-scattering albedo approaches a single consistent value.Hypothesis 2 (H2): Low cloud properties over the south Atlantic are sensitive to warming aloft and surface dimming by absorbing aerosol. The magnitude of this sensitivity and the responsible mechanisms depend on the altitude and optical properties of the absorbing aerosol and can be distinguished from meteorological effects.Hypothesis 3 (H3): South Atlantic boundary layer CCN can be dominated by BB aerosols entrained from higher altitude plumes. These aerosols can significantly alter cloud microphysics, precipitation susceptibility, and cloud mesoscale organization.

the main stratocumulus deck. The NASA ORACLES (ObseRvations of Aerosols above CLouds and their interactions; PI Jens Redemann) experiment is a funded $30M multi-aircraft deployment studying intraseasonal variations (August to October) in aerosol-cloud interactions through three campaigns taking place in 2016, 2017 and 2018. ORACLES will also place a new AERONET station upon St. Helena. Both aircraft campaigns will be based out of Walvis Bay, Namibia (230S, 14.50E). Furthermore, the year-long (June, 2016-May, 2017) DOE LASIC (Layered Atlantic Smoke Interactions with Clouds; PI Zuidema) deployment of the ARM Mobile Facility to Ascension Island (14.50W, 80S) will focus on the response of marine trade-wind cumulus to the presence of smoke. LASIC will gather surface-based aerosol/cloud remote sensing and in-situ datasets and includes 4x/daily radiosonde launches, increasing to 8x/daily during a two-month Intensive Observation Period that overlaps with the coordinated CLARIFY and ORACLES-2016 campaigns.

The Namibia-based aircraft campaigns will sample the stratocumulus deck from the south. ONFIRE proposes a five-week-long deployment of the NSF C-130 aircraft to Boiko on Sao Tome Island (00 N, 6.50E) for September 2017, the month when the stratocumulus cloud deck achieves its maximum extent and when the smoke outflow is most pronounced (Fig. 2). The northerly location allows ONFIRE to characterize the main aerosol outflow as the aerosol leaves the continent and moves west towards Ascension Island. The measurement foci are regular surveying along latitude/longitude lines, and, unique amongst the aircraft campaigns, characterizing cloud-top entrainment fluxes when smoke is present. The C-130 will provide detailed in-situ measurements of stratocumulus and cumulus cloud and BB aerosol microphysics, aerosol absorption, boundary-layer turbulence, and dropsonde characterization of the lower tropospheric thermodynamic structure accompanied by ‘curtain’ profiling of the aerosol, cloud and precipitation structure using active remote sensing measurements. The comprehensive instrumentation suite, listed within Section I of the Facilities Section, is compatible with the C-130’s space capacity. The ORACLES-2017 campaign will deploy a P-3 plane and will extend the in-situ and cloud surveying datasets of the ONFIRE C-130 to the south. The ONFIRE and ORACLES-2017 campaigns will coordinate on instrument calibrations, flight patterns, forecasts, analyses, and modeling exercises. A request will be made to DOE to extend LASIC through the 2017 biomass-burning season (“LASIC2”) with 8x/daily radiosondes on Ascension during the aircraft campaigns. A redundant ONFIRE request will also be made to NSF (to be negotiated with DOE) and, in a PI proposal, to provide for additional radiosondes on St. Helena. Collaboration between all the campaigns will include a combined spring 2017 meeting to discuss optimization of the ONFIRE/ORACLES-2017 sampling based on the CLARIFY experience, and to coordinate on modeling plans. One post-deployment joint science meeting with CLARIFY, ORACLES and LASIC scientists is anticipated (see letters of commitment from PIs Jens Redemann and Jim Haywood). 2.1.1. Why is Sao Tome our preferred aircraft deployment location?

Sao Tome Island (00 N, 4.50 E) is located 50 downstream of the main stratocumulus deck and near the primary continental BB aerosol outflow located at approximately 100S (Fig. 2). The Sao Tome location is excellent for sampling arguably the highest loading of biomass burning aerosol over a remote ocean of anywhere in the world. The location is also excellent for sampling a wide range of low cloud types and aerosol-cloud interactions. North of 50S and more pronounced to the west of Sao Tome, the boundary layer deepens and clouds become more cumuliform in response to the warming ocean surface (see also Sandu et al., 2010). The stratus-to-cumulus transition region in the southeast Atlantic occurs over the most tightly-packed SST gradients of any of the major stratocumulus decks, decreasing the spatial range needed for varied sampling. Only in this region does the northward-directed evolution of the boundary layer occur beneath a persistent smoke layer. As the cloudy boundary layer deepens north of 100S, the peak in aerosol loading subsides (Fig. 2). This supports our a priori expectation that a full range of aerosol-cloud interactions can be easily sampled, from BB aerosols overlying clouds without making contact with the cloud, to BB aerosol embedded within both stratus-dominated and cumulus-dominated boundary layers. We note that chemical sources from oil and gas platforms are located north of our sampling region, with the

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regional circulation discouraging their advection, although trace gas measurements and satellite remote sensing will help distinguish different source types. Preliminary feedback from NCAR RAF has indicated that Sao Tome is a feasible deployment location, with further assessment requiring a site visit. Sao Tome/Principe is an independent, Portuguese-speaking, politically-stable democratic republic with a strong tourist economy and some previous scientific infrastructure (Bourles et al., 2007; 2008). Other choices if the Sao Tome airport does not pass merit upon the NCAR RAF visit may be St. Helena Island, which is anticipating a new airport in 2016, or Ascension Island, which possesses a large military airfield. Lodging possibilities may not be adequate on either island. Walvis Bay or Windhoek, Namibia, is also a reasonable choice that allows full coordination with ORACLES-2017 campaign but at the cost of a smaller combined geographical sampling. 2.1.2 C-130 Flight Planning Strategy

To first-order, the vertical distribution of the absorbing aerosol and low cloud and their spatial and temporal variability must be known before the radiative forcings and cloud adjustments can be adequately characterized. Regular flight patterns following longitude or latitude lines for long distances ease comparison to large-scale models (e.g., Wood et al., 2011; Mechoso et al., 2014) and this approach is a key component of the ONFIRE flight strategy (Fig. 4). North-south (N-S) survey flights along 50E cross the SST gradient, following the mean low-level flow pattern and reaching the heart of the stratocumulus deck at 150S. A smaller number of east-west (E-W) transects along 50S sample along the mean 800-600 hPa aerosol flow, allowing longitude to serve as a proxy for aerosol aging and mixing. The E-W flights parallel the SST isotherms, clarifying the regional free-tropospheric subsidence structure and sampling the stratus-to-cumulus transition region. The repeated N-S and E-W sampling reveal the robust features, with correlations established between the aerosol-cloud vertical separations, boundary layer depth and free-tropospheric subsidence. Lead-lag correlations can take the boundary layer evolution into account.

The N-S survey missions along 50E and E-W survey missions along 50S comprise four to six and three out of the fifteen flights, respectively. The remaining six to eight flights follow shorter segments of the survey patterns but further focus on the entrainment at cloud-top, heretofore an undocumented process within semi-direct effect studies. The entrainment fluxes in multiple tracers will be recorded, from which the entrainment of the biomass burning aerosol will be inferred. From these fluxes, connections can be made to the cloud droplet concentration number and cloud residue composition. Cases selected for these flights will range from aerosol layers that clearly overlie stratocumulus, to cumulus clearly interacting with the aerosol layer above. Two of these flights will be done at night, to isolate the influence of shortwave absorption, and to assess the impact of longwave radiation emitted by the moisture within the aerosol plume (smoke itself does not emit or scatter longwave radiation). Observational mission support (e.g., planning, flight guidance) will come from geostationary half-hourly Meteosat SEVIRI imagery and retrievals and from real-time chemical weather forecasting. The satellite datasets will be made available in near-real time both on site and to remote participants by NASA Langley scientists.2.1.2 Island-based thermodynamic profiling

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Fig. 4: North-south aerosol-cloud cross-section missions will occur along 5E to 15S and east-west along 5S to 5W (in pink and purple respectively), and entrainment flux profiling for stratocumulus and cumulus is shown in blue. The St. Helena and Ascension Islands are indicated with red stars. MODIS imagery is from Sept. 23, 2012, with all operationally-available aerosol optical depths shown (color scale varies from 0 to 0.3).

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Observations of the diurnal cycle in the boundary layer vertical thermodynamic structure are currently lacking for the southeast Atlantic. Such profiles are essential for model initialization and evaluation (e.g., Hannay et al., 2009). Enhanced monitoring of the diurnal cycle will be implemented at two UK Protectorate islands for the duration of the ONFIRE campaign. One site is St. Helena Island, where the UK Met Office has launched ~five radiosondes/week at 12 UTC for many decades (Adebiyi et al., 2014) and now operates a ceilometer (to infer cloud base height). Ascension Island lies along the approximate mean low-level flow downwind of St. Helena Island within the trade-wind-cumulus regime (Fig. 5). The two sites in tandem allow for a unique pseudo-Lagrangian evaluation of the boundary layer evolution over several days. The radiosondes combined with the AERONET aerosol optical depths allow further assessment as a function of the BB aerosol loading, with combined ORACLES and ONFIRE sampling determining aerosol flow as a function of altitude.

2.2 Modeling approach ONFIRE will connect modeling approaches occurring at different scales towards understanding and characterizing the climate-scale implications of absorbing-aerosol-cloud interactions (Table 1). These span large-eddy-scale simulations examining detailed cloud-aerosol processes within relatively small domains (Ackerman et al., 2000; Johnson, 2005; Feingold et al., 2005), mesoscale-to-synoptic scale modeling (Brioude et al., 2009; Solomon et al., 2011; Kazil et al., 2014), regional modeling studies able to capture synoptic and regional circulation patterns (Allen and Sherwood, 2010; Randles and Ramswamy, 2010; Sakaeda et al., 2011) and teleconnections (Jones et al., 2009) to the global aerosol models represented within AeroCom. These approaches explore the range of scales at which smoke-cloud interactions might occur, and generate scale-comprehensive frameworks for testing sensitivity to cloud and aerosol parameterizations. Directed efforts will connect the relationships between newly-observed sub-grid-scale, process-level variables such as vertical velocities and cloud-top entrainment to the model counterparts (e.g.,Yamaguchi et al., 2013). These, combined with the in-situ validation satellite retrievals, will be linked to the large-scale boundary layer variables used within climate models, through, e.g., joint probability distributions (Golaz et al., 2011). Boundary layer development (moistening through surface fluxes versus drying through entrainment) and their interactions with microphysical processes - autoconversion and collision-coalescence blending with condensational heating and evaporational cooling - will also be assessed at the process-level scale and support a further linking to the larger-scale models (e.g., Gettelman et al., 2013). The real-time regional modeling will also provide chemical weather forecasts that will be used for mission planning. Pre-deployment modeling activities encouraged by the already-funded CLARIFY, ORACLES and LASIC projects and possibly using their trial datasets will help sharpen criteria for accepting/rejecting ONFIRE hypotheses.

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Fig. 5, left-hand panel: Sept-Oct 1000 hPa climatological winds with an ensemble of Sept. 2013 HYSPLIT forward trajectories from St. Helena Island (superimposed) passing near Ascension Island. Right-hand panels depict the 2000-2012 September-mean thermodynamic profiles from ~daily IGRA radiosondes.

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Table 1: Models and relationship to ONFIRE

2.2.1 Large-eddy simulations (LES)High-resolution modeling will focus on ~25 km x 25 km domains with ~100 m grid sizes to

study (i) how the vertical distribution and spatial inhomogeneities of absorbing aerosol impact cloud cloud field properties (Wang and Feingold 2009; Lee et al. 2014); (ii) the contrasting influence of the absorbing aerosol on stratocumulus and cumulus cloud fields (e.g., Johnson et al., 2004; Johnson, 2005); and (iii) the transition from the stratocumulus to cumulus regime. SST-gradient studies consider surface flux effects (e.g., Kazil et al., 2014), and their response to the attenuation of solar radiation by the aerosol above (e.g., Koren et al., 2004; Feingold et al., 2005 done over land). Large-eddy simulations also characterize the respective strengths of meteorological and aerosol impacts on a dynamically adjusting cloud field (e.g., Wang and McFarquhar, 2008; Petters et al., 2013).2.2.2 Regional modeling: post-deployment and real-time

The sensitivity of aerosol-cloud interactions to meteorology will be explored using nested-Weather Research and Forecasting (WRF) simulations, wherein the innermost domain possesses the eddy-resolving scale of 50-100 m but the outermost domain is responsive to realistic (i.e., reanalysis) forcings (e.g., Solomon et al., 2011, Li et al., 2014). This allows the nested simulations to examine forcing assumptions needed for the LES studies, such as homogeneous free-tropospheric subsidence. Another approach will combine WRF meteorological fields with a Lagrangian particle dispersion model (FLEXPART-WRF) to calculate trajectories and estimate concentrations of tracers within the WRF domain (Brioude et al., 2013). Those tracers will correspond to terrestrial aerosol sources, including MODIS-derived point sources of southern African fires. The tracers are passive, but a wet deposition parameterisation based on meteorological fields from WRF can be applied.  Satellite-derived and ONFIRE cloud property datasets can then be correlated against the FLEXPART aerosol products for different meteorological situations (Brioude et al., 2009). The FLEXPART model (Stohl et al., 2005) will also provide the real-time chemical weather mission forecasting needed to define optimal flight strategies. FLEXPART will keep track of millions of passive tracer particles individually for ten days, towards visualizing and characterizing the aerosol transport pathways (e.g., Wood et al., 2011). These will complement real-time ECMWF forecasts. 2.2.3 Regional and global model testbeds and intercomparisons

ONFIRE observations will establish benchmarks for several parameterization testbed exercises. In one application, the WRF model will be set up for data-rich and meteorologically distinct days, after which physical parameterizations can be swapped in and out of the model (e.g., Fast et al. 2011). A similar approach with single-column models (SCMs) derived from climate models provides a direct link for climate model improvement. SCM modeling will explore the physics within

model & description investigator & funding

purpose

large-eddy simulations @ 50-100 m resolution, ~50km domains

Graham Feingold (NOAA ESRL)NOAA-AC4, TBS

process studies at resolution of in-situ obs; perturbation studies to examine dynamic adjustments to both aerosol and meteorology

FLEXPART Lagrangian particle tracer model

Jerome Brioude (U of C.) NSF, TBS

real-time mission support; assessment of direct & cloud adjustment effects

nested-WRF (50-100m resolution inner domain, outer domain ~ 30 degrees)

Amy Solomon (U C.) NSF, TBS

process studies transmitting large-scale forcing to eddy-resolving inner domain

NCAR CESM climate model Brian Medeiros (NCAR) N/A

cloud and aerosol parameterization testbed

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climate models (both with and without aerosol), perturbations to those physics, and the testing of different physical parameterizations (e.g., Neggers et al., 2012). SCM modeling of select case studies will be compared to further assess climate model parameterizations and their sensitivity to the sub-grid-scale (e.g., Moeng et al., 1996; Duynkerke et al., 2004; Stevens et al.,2005; Zhu et al., 2005; Wyant et al., 2007). At the largest scale, parameterization testbed (CAPT) forecasting exercises will examine the short-range forecasts of global climate models to assess their fast physics (e.g., Hannay et al., 2009; Medeiros et al., 2012). Additional comparisons of the cloud adjustment effects in the forecast framework will gain insight into the sensitivity of the clouds within NCAR’s coupled climate model to aerosol effects, and can contribute to establishing the framework for broader model participation.

A post-deployment model intercomparison project, similar to the successful PreVOCA assessment (Wyant et al., 2010), will be coordinated to assess the forecast skill of a diverse set of participating models. Satellite retrievals, validated with the in-situ observations, will serve as the large-scale observational validation. A more constrained post-deployment model intercomparison of the semi-direct aerosol radiative effect will also occur within the AeroCom framework (see letter of commitment from Philip Stier, AeroCom Co-chair of the radiative forcing working group) with participation from ONFIRE modelers. In-situ observations improve the model aerosol constraints and advise on the observed fast cloud response. The modeling intercomparison exercise will also examine the large-scale circulation response to the presence of absorbing aerosol. In so doing an idealized absorbing aerosol distribution can be established and merged with the “Easy Aerosol model intercomparison” protocol (Voigt et al., 2013) established for the World Climate Research Programme ‘Coupling Clouds to Circulation’ initiative.3. How will ONFIRE test the proposed hypotheses?

Testing Strategy: Regular flights of at least eight hour duration, with an anticipated 1500 km range, repeated along the same longitude and latitude lines provide systematic observation of a complete and characteristic range of aerosol conditions (Fig. 6), and establish robust statistical descriptions of aerosol composition and absorption along the dominant gradients in aerosol loading (N-S) and aging (E-W). All of the fifteen total flights contain level legs along 50E within the aerosol layer, with at least one-third reaching into the heart of the stratocumulus deck at 150S. Outgoing legs will use the downward-looking Multi-function Airborne Raman Lidar (MARLi) and the Wyoming Cloud Radar (WCR) to provide ‘curtain’ depictions of the aerosol and free-troposphere moisture vertical structure, with dropsondes profiling the lower tropospheric thermodynamic structure. At least three flights will survey along E-W flight paths at 50S reaching out to 50W. All returning legs use a comprehensive chemistry and aerosol sampling suite that includes redundancy in the important aerosol SSA measurement for the in-situ characterization. Measurements specifically aimed at characterizing the aerosol SSA include photoacoustic absorption and cavity ringdown (PAS-CRD) measurements capable of measuring the change in extinction with relative humidity. The PAS-CRD/SP2 pairing can assess how hygroscopic swelling of aerosol impacts its absorption, with further comprehensive humidity measurements made by the dropsondes and downward-looking Raman lidar. Closure studies link absorption to measurements of BC mass and mixing state, such as from the single-particle soot photometer (SP2). Size-resolved aerosol composition measurements will be made by a compact time-of-flight aerosol mass spectrometer characterizing the submicron non-refractory components of aerosol (e.g., organics, sulfate, nitrate, chloride, and ammonium) at 15-s intervals. Aerosol size measurements will be made by an ultra high sensitivity aerosol spectrometer (UHSAS) sizing over the 50-1000 nm, a DMT CCN counter, and, from NSF’s deployment pool, the TSI-3760, DMT-PCASP and DMT-FSSP300, with a Giant Nuclei Impactor (GNI) extending the sizing range out

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Hypothesis 1 (H1): The composition of African aerosol over the south Atlantic is highly variable but as the aerosol ages offshore its single-scattering albedo approaches a single consistent value.

to the coarsest aerosol sizes. Filter analyses will further assess the relative organic content of brown carbon (as well as possible dust). The in-situ linking of aerosol composition and shortwave absorption measurements will in combination determine how BB aerosol properties evolve offshore, and determine realistic mean and variability values of the SSA as a function of location, with aerosol SSA serving as the radiatively-important proxy for aerosol aging and mixing. Based on Dubovik et al. (2000) Table 4, we presume a standard deviation/uncertainty in SSA of 0.03 as acceptable for satisfying the hypothesis. The survey missions are daytime-only missions to connect aerosol properties to their shortwave absorption and radiative heating rates, and occur at approximately the same time of day to reduce diurnal aliasing.Hypothesis 1 will be refuted if offshore aerosol single-scattering albedo values from the different flights do not converge to within 0.03 as a function of location.

Testing Strategy: The survey flights detail the extent to which the BB aerosol and cloud intermingle. A second ‘entrainment’ flight pattern will focus on gathering datasets that support process studies on how low clouds adapt to the presence of absorbing aerosol aloft. Stratocumulus and cumulus (also needed to test H3) targets of opportunity will be sought within ~700 km range and arrived at following the survey latitude/longitude flight pattern. The ‘entrainment’ flight pattern will consist of stacked flight segments that also strengthen direct measurements of the aerosol radiative heating. These flights supply the first documentation of the semi-direct effect upon the cloud-top entrainment velocities, a key parameter for connecting aerosol absorption to the adjustment in the cloud properties.

The aerosol heating rate vertical profiles will be calculated in three different ways. One approach is an indirect calculation based on the vertical profiles of in-situ aerosol extinction and SSA and of the underlying broadband-radiometer-determined cloud albedo (Magi et al., 2008). Another approach with arguably lower uncertainties uses spectral measurements from the HIAPER Atmospheric Radiation Package (HARP, adapted for the C-130). HARP measures actinic fluxes (280-680 nm) and includes a Solar Spectral Flux Radiometer (SSFR; Pilewski et al., 2003), a moderate resolution irradiance spectrometer (360-2150 nm). The ramp legs within the ‘survey’ flight pattern provide a direct, layer-averaged radiative flux divergence from which an aerosol absorption can be inferred (Schmidt et al., 2010). The stacked legs within the ‘entrainment’ flight pattern determine the aerosol radiative forcing using a flux gradient approach (Pilewski et al., 2003; Redemann et al., 2006). The downwelling spectral irradiance measurements below aerosol-

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Hypothesis 2 (H2): Low cloud properties over the south Atlantic are sensitive to warming aloft and surface dimming by absorbing aerosol. The magnitude of this sensitivity and the responsible mechanisms depend on the altitude and optical properties of the absorbing aerosol and can be distinguished from meteorological effects.

Fig. 6: Survey flight pattern along 50E from equatorial Sao Tome to 150S. Four to six total flights will adopt this pattern, and three will turn westward at 50S and fly along 50S to 50W using the same flight plan. The entrainment-focused flights will also survey and sample along the same lat/lon lines, but over shorter ranges.

05S10S Latitude15S0

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outgoingreturning5E North-South Cross Section

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embedded broken cloud layers can be used to separate the effects from aerosols and clouds (Schmidt et al., 2009; Kindel et al., 2011), potentially aided by three-dimensional radiative transfer modeling (Schmidt et al., 2011). Three-dimensional radiative transfer modeling of large-eddy simulations initialized by the observations help elucidate differences between plane-parallel and measured irradiances (Zuidema et al., 2008; Schmidt et al., 2009).

The thermodynamic and turbulence properties of the cloud top inversion are also established during the survey flights, but the six to eight ‘entrainment’ flights additionally constrain the entrainment fluxes at cloud-top using a variety of tracers (CO, DMS, O3, CO2 and multiple other trace gases) and turbulent kinetic energy measurements. These flights intersperse along- and across-wind level legs above and below cloud top at three or four different levels with a porpoising pattern at cloud top. The DMS measurements are particularly valuable, as DMS primarily originates from ocean biogenic emissions, with little DMS present in biomass burning plumes (10-5 relative to CO; Sinha et al., 2003), and a ~day photochemical lifetime precluding much advection. High-rate (10-25 Hz) DMS measurements will be made using an Atmospheric Pressure Ionization Mass Spectrometer (APIMS). Comprehensive trace gas measurements made with NSF’s Trace Organic Gas Analyzer (TOGA) further discriminate BB aerosol source impact on entrainment, with acetronitrile in particular providing a unique biomass burning marker (de Gouw and Warneke, 2007).

Broadband radiometers provide the shortwave and longwave radiative flux divergence measurements at the cloud top. The clouds will be fully characterized using a variety of in situ cloud probes (Cloud Droplet Probe (CDP), Gerber, FSSP, King, 2D-C, 2DP and phase Doppler interferometer (PDI)) and remote sensing measurements by the Wyoming Cloud Radar (WCR). These will be combined with lidar-determined cloud boundaries, radiometer-derived liquid water paths and SSFR retrievals of cloud optical depth and near-cloud-top effective radius.

Cloud-aerosol interactions are intimately coupled with meteorology and difficult to separate (Stevens and Feingold, 2009; Wilcox, 2012; Adebiyi et al., 2014). We anticipate highly-variable aerosol loadings for similar meteorological situations (de Graaf et al., 2014) because the number and intensity of the fires vary spatially and daily. Although meteorological variability is typically less than in mid-latitude regions, variability in the southerly African Easterly Jet is hypothesized to result in substantial differences in the offshore aerosol transport (Magi et al., 2008; Adebiyi et al., 2014). Forward trajectories will help identify targets of opportunity for the entrainment flights that are subject to similar meteorological conditions, analyzed post-deployment using a passive tracer modeling analysis (Brioude et al., 2009). Dropsondes characterize the accompanying larger-scale atmospheric vertical thermodynamic and kinematic structure to great detail (Fig. 5). Other model cloud-aerosol relationships, using ONFIRE datasets for the model initialization, will be compared to the observed relationships. Process studies applying perturbations to imposed meteorological and aerosol forcings (Wang and McFarquhar, 2008; Petters et al., 2013) assess equivalences in the cloud dynamic response to meteorology and aerosol impacts. WRF-Chem simulations validated with ONFIRE datasets and run with and without BB emissions further help distinguish cloud responses to aerosol from meteorology. Pre-deployment, WRF-Chem simulations will be sampled as the aircraft will sample nature, to establish plausible ranges on cloud properties for varying aerosol loadings.Hypothesis 2 will be refuted if differences in low cloud properties existing in similar meteorological conditions, but with different overlying BB aerosol conditions, are statistically similar, corroborated by process model studies.

Testing Strategy: Elevated values of boundary layer CCN occur in the remote Atlantic but can originate from a wide range of source regions (Swap et al., 1996) and it is unclear if free-

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Hypothesis 3 (H3): South Atlantic boundary layer CCN can be dominated by BB aerosols entrained from higher altitude plumes. These aerosols can significantly alter cloud microphysics, precipitation susceptibility, and cloud mesoscale organization.

tropospheric BB aerosol can be a dominant source of boundary layer CCN. All fifteen flights contribute to testing H3. Boundary layer aerosol and BC composition are ascertained under H1, combined with CCN size distributions. Entrainment fluxes of BB aerosol will be derived through combining H2 entrainment estimates with BB aerosol concentrations immediately above and within the boundary layer. Water vapor isotope analyses will also be applied to assess air mass mixing and precipitation efficiency (Bailey et al., 2013). Aerosol residuals within cloud drops gathered by a Counterflow Virtual Impacter (CVI) and from filter samples will be analyzed for their similarity to above-cloud and interstitial aerosol composition also sampled through the CVI inlet. Cloud drop size distributions and concentrations will be assessed in concert with the aerosol measurements, to form an aerosol-CCN-cloud microphysical closure. Trace gas measurements combined with trajectory analyses help identify aerosol source regions, as will comparison of ORACLES-2017 and ONFIRE datasets.

Cloud modulation in response to enhanced CCN levels include precipitation susceptibility estimates based on drizzle rates retrieved from the WCR and in-situ probes, combined with cloud boundary and liquid water path information and independently-calculated cloud droplet number concentrations (e.g., Sorooshian et al., 2010; Terai et al., 2012). Statistics based on the observations and extended to satellite data will be used to search for correlations between cloud fraction and entrained aerosol. Large-eddy simulations initialized with ONFIRE soudings will examine cloud field changes resulting from perturbations applied to the aerosol and meteorology forcings. The LES fields used within radiative transfer simulations will distinguish the radiative consequences of the cloud microphysical and mesoscale changes. Hypothesis 3, that BB aerosol can modulate cloud microphysics, is falsified if BB concentrations correlate poorly with accumulation mode aerosol and if BB aerosol are not found within cloud drops with CCN and accumulation mode aerosol.4. Why aren’t currently-available satellite datasets enough? Arguably the best tools for global observational cloud-aerosol assessments are space-based active lidar and radar. While highly informative, these cannot say with confidence if aerosol-cloud layers touch. The aerosol layer base is optically very thin and reliant on an attenuated lidar signal. Daytime vertical sampling is further hampered by solar interference (Meyer et al., 2013). Thus, CALIOP cloud-aerosol separation statistics tend to suggest little cloud-aerosol overlap and therefore little aerosol entrainment into the cloudy boundary layer (Meyer et al., 2013), but, this is contradicted by studies of the cloud decks themselves (Constantino and Breon, 2013; Painemal et al., 2014). Space-based lidar can also not penetrate clouds, missing important information on the boundary layer aerosol. Satellite visible/near-infrared radiances typically provide much more extensive sampling of aerosol, but not in cloudy regions (e.g. Fig. 4). In addition passive aerosol retrievals from cloud-free areas are not necessarily representative of above-cloud aerosol and are also impacted by sunlight reflecting off of clouds kilometers away (e.g., Wen et al., 2007). New retrievals are rapidly developing for aerosols overlying clouds (e.g., de Graaf et al., 2012; Waquet et al., 2013; Meyer et al., 2013). Such efforts still depend on assumptions and models of the absorbing aerosol size distributions and refractive indices. When the same radiances are applied to cloud retrievals, they typically underestimate cloud optical depth and effective radius (Haywood et al., 2004; Meyer et al., 2013). These call into question similarly-derived retrievals of cloud droplet number concentration (Bennartz, 2007; Painemal and Zuidema, 2011), which could otherwise be used to spatially survey aerosol activation. Cloud fraction estimates can similarly be biased high if aerosol is confused for cloud.

ONFIRE in-situ information on the BB aerosol will be used to assess satellite-derived inferences, support bias characterization in existing retrievals and further retrieval improvements and development. Large differences in BB emission databases for Africa (Granier et al., 2011) have been attributed to satellite algorithms differences, and ONFIRE aircraft CO measurements provide one validation approach (Barret et al., 2010). Other in-situ data can assess if an E-W gradient in satellite-

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derived aerosol angstrom exponent (Waquet et al., 2013) is genuine, and provide insight into recent trend studies based on the decadal-plus time series of EOS-era satellites (Zhang et al., 2010). The N-S survey flights will be coordinated with nearby CALIOP and CloudSat overpasses to take full advantage of coincidences. ONFIRE aerosol datasets will inform AERONET retrievals, which have long been integral to satellite aerosol retrieval development and for climate model validation (Kinne et al., 2013). 5. Other ONFIRE Partners

The equatorial SST biases in coupled climate models have spurred two European-funded oceanographic campaigns that are currently underway. These use oceanographic fieldwork and climate modeling to address primarily oceanographic hypotheses. We anticipate linkages with the large EU-funded PREFACE project (Enhancing PREdiction oF tropical Atlantic ClimatE and its impact) taking place from 2013 to 2019. PREFACE funding supports a PredIction Research moored Array in the Tropical Atlantic (PIRATA; Bourles et al., 2008) buoy at 80S, 60E, that collects both solar and infrared radiation fluxes as well as surface meteorological data. This data provides context for ONFIRE measurements, and ONFIRE measurements help connect the surface energy budget to the atmosphere above. Coordination is also expected on climate model assessments.

There are no plans to extend the PIRATA buoy array southward of 80S, and PIRATA-buoy-tending cruises do not typically traverse the area of interest. The German R/V Polarstern does traverse the SEA on its typical route from Bremerhaven - Cape Town (boreal fall). A collaboration is already active between Chris Fairall (NOAA ESRL) and Andreas Macke at the Institute for Tropospheric Research in Leipzig, and the NOAA ESRL motion-stabilized Dopper W-band cloud radar (Moran et al., 2011) cloud radar was deployed upon the R/V Polarstern during the boreal spring of 2014 along with a ceilometer and microwave profiler. These complement the German instrumentation suite consisting of a Raman lidar, microwave radiometer, radiation and turbulent flux measurements, sun photometer and rain gauges. We will seek for US-provided instruments to again be coordinated with those of Prof. Andreas Macke during the boreal fall of 2017.6. ONFIRE Relationship to Previous Campaigns

The high degree of current interest in the southeast Atlantic is in part because the most recent significant SEA field experiment, SAFARI-2000 (Swap et al., 2003), occurred twenty-four years ago prior to the modern satellite era, with most measurements localized near the Namibian coast. The Indian Ocean Experiment (INDOEX; Ramanathan et al., 2001) examined shallow marine cumulus embedded within lower-lying smoky boundary layers off the Indian coast, and Smoke Aerosols, Clouds, Rainfall and Climate (SMOCC; Andreae et al., 2004) was located over land in the Amazon. The Transport and Atmospheric Chemistry near the Equator-Atlantic (TRACE-A; Fishman et al., 1994) examined southern hemisphere aerosol transport but not aerosol-cloud interactions. The Dynamics and Chemistry of Marine Stratocumulus (DYCOMS-II; Stevens et al., 2003) and the trade-wind cumulus Rain In Cumulus over Ocean (RICO; Rauber et al., 2007) experiment did not consider absorbing aerosols. The European African Monsoon Multidisciplinary (AMMA) project was focused north of the equator. The other major recent southern hemisphere experiment is the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx; Mechoso et al., 2014) held in the southeast Pacific. The southeast Pacific boundary layer CCN was dominated by sulfate aerosol (with trace amounts of absorbing aerosol) and comparative studies of the VOCALS-REx and ONFIRE campaigns promise to yield interesting insights. The UK CLARIFY and ORACLES campaigns, with which ONFIRE will be coordinated, are both interrogating the southeast Atlantic smoke+cloud regime from the south, with only ONFIRE focusing on the location with the main aerosol outflow and where the stratocumulus transitions into trade-wind cumulus. The complementary sampling by all three campaigns, when analyzed holistically, addresses the concern of the more limited sampling possible with only one ~month-long single-aircraft campaign.

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7. BudgetA small travel budget is included for a Sao Tome site visit, attendance to a planning meeting and to a Conference of the South African Society for Atmospheric Sciences.Broader Impact and Outreach

Field campaigns focusing on the marine boundary layer are critical for developing more realistic parameterizations, but perhaps more importantly, maintain a pathway for the development of the necessary expertise, particularly for early-career young scientists. ONFIRE will train young scientists and foster new international collaborations. Climate process team proposals will further the larger goal of using observational research to improve the large-scale models and help inform further IPCC Assessments. During the deployment itself, weekly presentations on the fundamentals in the field of the collected experts will be held and archived. These will target graduate students and researchers outside of the speaker’s expertise. Other activities elevate the visibility of the project, of the greater mission of NSF, and of the importance of observational climate research. A YouTube video of the deployment will be coordinated with NCAR’s Education and Outreach office and will include videocameras made available to the investigators themselves, also allowing investigators to tailor media content for use at their home institutions. A small budget will be included to fund a professional photographer/videographer, with the understanding that the raw footage be available to all investigators. A blog will be maintained during the experiment. Local outreach upon Portuguese-speaking Sao Tome, a poor country with little educational infrastructure beyond high school, will be facilitated through recruitment of a Brazilian student or postdoc and will also include NCAR’s Outreach office. Outreach to regional research networks, which will seek more direct involvement with African scientists, will follow good practices for science diplomacy (Annegarn and Swap, 2012), beginning with a short BAMS article already in preparation. We will present and network at an annual South African Society for Atmospheric Sciences Conference, the leading scientific conference upon the African continent, prior to ONFIRE, and outreach to the Dynamics-Aerosol-Chemistry-Cloud Interactions in West Africa (DACCIWA; PI Peter Knippertz) investigators and regional research partners. DACCIWA will study the West African monsoon with a June 2015 IOP.

Results from Prior NSF SupportATM-0745470: 2/1/2008-1/31/2010 $210,414, "Cloud remote sensing in support of VOCALS-REx: Linking cloud optical properties to aerosol and precipitation variability" (PI: P. Zuidema). This supported the inclusion of an airborne millimeter-wave radiometer and partially supported PhD graduate student David Painemal (Painemal, 2011). Products include Zuidema et al. 2012a, Painemal and Zuidema (2011), Painemal and Zuidema (2013), Wood et al. (2011), Terai et al. (2012), Twohy et al. (2013), and Mechoso et al., (2014), and an Integrated DataSet.ATM-0735955 1/1/2008-12/31/2010 $380,934 "From Fine-scale mixing to the mesoscale: Assessing the climatic impact of trade-wind Cumuli with RICO data and modeling" (PI: Zuidema, co-PI: Albrecht; Collaborative proposal with Dr. Ping Zhu at the Florida International University). Grant publications include Zuidema et al., (2012b), Li et al., (2014a, 2014b) and Zhu and Zuidema (2009). The grant supported PhD student Zhujun Li. ATM-0923217: 9/1/2009-8/31-2012 $822,473 “MRI: Acquisition of Instrumentation for an Integrated South Florida Cloud-Aerosol-Rain-Observing System (CAROb)” (PI: P. Zuidema). This Major Research Instrumentation grant supported the development of a cloud remote sensing laboratory http://carob.rsmas.miami.edu. Publications include Oktem et al., (2014) and Zuidema et al., (2014). AGS-1233874: 9/1/2012-8/31-2015 “Dynamical Influences on stratocumulus-aerosol interactions in the Southern Hemisphere” (PI: P. Zuidema). This is supporting PhD student Adeyemi Adebiyi. Grant publications include Adebiyi et al., (2014), Painemal and Zuidema (2013) and Mechoso et al., (2014). An REU supplement has supported two undergraduate researchers.

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References

Abel, S. J., J. M. Haywood, E. J. Highwood, J. Li, and P. R. Buseck, 2003: Evolution of biomass burning aerosol properties from an agricultural fire in southern Africa, Geophys. Res. Lett., 30(15), 1783, doi:10.1029/ 2003GL017342.

Abel,S. J., E. J. Highwood, J. M. Haywood, and M. A. Stringer, 2005: The direct radiative effect of biomass burning over southern Africa. Atmos. Chem. Phys., 5, 1999-2018. doi:1680-7324/acp/2005-5-1999.

Ackerman, A.S., O.B. Toon, D.E. Stevens, A.J. Heymsfield, V. Ramanathan, and E.J. Welton, 2000: Reduction of tropical cloudiness by soot. Science, 288, 1042-1047

Ackerman, A. S., Kirkpatrick, M. P., Stevens, D. E., and Toown, O. B., 2004: The impact of humidity above stratiform clouds on indirect aerosol climate forcing. Nature, 432, 1014–1017, doi:10.1038/nature03174.

Adebiyi, A., P. Zuidema and S. Abel, 2014: The convolution of dynamics and moisture with the personce of shortwave absorbing aerosols over the southeast Atlantic. J. Clim., doi:10.1175/JCLI-D-14-00352.1

Albrecht, B. A., 1989: Aerosols, Cloud Microphysics, and Fractional Cloudiness. Science, 245, 1227–1230.

Allen, R. J., and S. C. Sherwood, 2010: Aerosol‐cloud semi‐direct effect and land‐sea temperature contrast in a GCM, Geophys. Res. Lett., 37, L07702, doi:10.1029/2010GL042759

Allen, G., H. Coe, A. Clarke, et al. 2011: Southeast Pacific Atmospheric Composition and Variability Sampled Along 20S During VOCALS-Rex, Atmos. Chem. Phys., 11,5237-5262, 2011

Andreae, M. O.,J. Fishman, M. Garstang, J. Goldammer, C. Justice, J. Levine, R. Scholes, B. Stocks, A. Thompson, B. Wilgen and the STARE/TRACE-A/SAFARI-92 Science Team, Biomass burning in the global environment: First results from the IGAC/BIBEX field campaign STARE/TRACE-A/SAFARI-02, in Global Atmospheric-Biospheric Chemistry: The First IGAC Scientific Conference, edited by R. Prinn, Plenum, New York, 83-101. pp., 1994.

Andreae, M. O., et al., 2004:, Smoking rain clouds over the Amazon, Science, 303, 1337–1342Andreae, M. O. and Rosenfeld, D., 2008: Aerosol-cloud- precipitation interactions. Part 1: The nature and

sources of cloud-active aerosols, Earth Sci. Rev., 89, 13–41, doi:10.1016/j.earscirev.2008.03.001.Annegarn, H., and R. Swap, 2012: SAFARI 2000: A Southern African example of science diplomacy.

Science & Diplomacy, 1, 47-69.Bailey, A. D. Toohey and D. Noone, 2013: Characterizing moisture exchange between the Hawaiian

convective boundary layer and free troposphere using stable isotopes in water. J. Geophys. Res., 118, 8208.8221, doi:10.1002/jgrd.50639

Barret B, Williams JE, Bouarar I, Yang X, Josse B, Law K, Pham M, Le Flochmoën E, Liousse C, Peuch VH, Carver GD, Pyle JA, Sauvage B, van Velthoven P, Schlager H, Mari C, Cammas J-P,2010:Impact of West African Monsoon convective transport and lightning NOx production upon the upper tropospheric composition: a multi-model study. Atmos Chem Phys 10:5719–5738. doi:10.5194/acp-10-5719-2010

Bennartz, R., 2007:, Global assessment of marine boundary layer cloud droplet number concentration from satellite, J. Geophys. Res., 112, D02201, doi:10.1029/2006JD007547

Berner, A. H., Bretherton, C. S., Wood, R., and Muhlbauer, A., 2013: Marine boundary layer cloud regimes and POC formation in an LES coupled to a bulk aerosol scheme, Atmos. Chem. Phys. Discuss., 13, 18143-18203, doi:10.5194/acpd-13-18143-2013

Bond, T. et al., 2013: Bounding the role of black carbon in the climate system: A scientific assessment. J. Geophys. Res., 118, p. 1-173. doi:10.1002/jgrd.50171.

Bourlès, B., Brandt, P., Caniaux, G., Dengler, M., Gouriou, Y., Key, E., Lumpkin, R., Marin, F., Molinari, R. L. & Schmid, C. 2007: African Monsoon Multidisciplinary Analysis (AMMA) : Special measurements in the Tropical Atlantic. In: CLIVAR Newsletter Exchanges, Nr. 12 n°2, 4–6

Bourlès, Bernard, and Coauthors, 2008: The Pirata Program: History, Accomplishments, and Future Directions. Bull. Amer. Meteor. Soc., 89, 1111–1125. doi: http://dx.doi.org/10.1175/2008BAMS2462.1

Boyer, D. C., H. J. Boyer, I. Fossen, and A. Kreiner, 2001: Changes in abundance of the northern Benguela sardine stock during the decade 1990 – 2000, with comments on the relative importance of fishing and the environment, S. Afr. J. Mar. Sci., 23, 76–84.

Bretherton, C.S., R. Wood, R. C. George, D. Leon, G. Allen, and X. Zheng, 2010: Southeast Pacific stratocumulus clouds, precipitation and boundary layer structure sampled along 20° S during VOCALS-REx. Atmos. Chem. Phys., 10, 10639-10654.

Brioude, J. et al., 2009: Biomass burning on marine stratocumulus clouds off of the Californian coast. Atmos. Chem. Phys., 9, pp. 8841-8856. doi:10.5194/acp-10-8841-2010.

Brioude, J., et al., 2013: Top-down surface flux in the Los Angeles Basin using the inverse modeling technique: assessing anthropogenic NOx and CO2 and their impacts. Atmos. Chem. Phys., 13, 3661-3677, doi:10.5194/acp-13-3661-2013.

Boucher, O., D. Randall, P. Artaxo, C. Bretherton, G. Feingold, P. Forster, V.-M. Kerminen, Y. Kondo, H. Liao, U. Lohmann, P. Rasch, S. K. Satheesh, S. Sherwood, B. Stevens and X. Y. Zhang, 2013: Clouds and Aerosols. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T. F., D. Qin, G.-K. Plattner, M. Tignor, S. K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P. M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, in press

Cahoon, D., B. Stocks, J. Levine, W. Cofer and K. O’Neill, 1992: Seasonal distribution of African savanna fires. Nature, 359, p. 812-815.

Carman, J. K., D.L. Rossiter, D. Khelif, H. H. Jonsoon, I. C. Faloona and P. Chuang, 2012: Observational constraints on entrainment and the entrainment interface layer in stratocumulus. Atmos. Chem. Phys., 12, p. 11135-11152. doi:10.5194/acp-12-11135-2012

Carslaw, K. S., et al., 2013: Large contribution of natural aerosols to uncertainty in indirect forcing. Nature, 503, doi:10.1038/nature12674.

Chand, D.,R. Wood, T. L. Anderson, S. K. Satheesh and R. J. Charlso, 2009: Satellite-derived direct radiative effect of aerosols dependent on cloud cover. Nature Geo., doi:10.1038/ngeo0437

Chuang, P. Y., J. D. Small, E. W. Saw, R. A. Shaw, C. M. Sipperley, G. A. Payne, and W. D. Bachalo, 2008: Airborne phase Doppler interferometry for cloud microphysical measurements. Aerosol Sci. Technol.,

Costantino, L. and Bre on, F.-M., 2010: Analysis of aerosol-cloud interaction from multi-sensor satellite observations, Geophys. Res. Lett., 37, L11801, doi:10.1029/2009GL041828.

Costantino, L. and Bre on, F.-M , 2013: Aerosol indirect effect on warm clouds over South-East Atlantic, from co-located MODIS and CALIPSO observations. Atmos. Chem. Phys., 13, 69–88, doi:10.5194/acp-13-69-2013

Cury, P., Bakun, A., Crawford, R. J. M., Jarre, A., Quin ones, R. A., Shannon, L. J., and Verheye, H. M. 2000. Small pelagics in upwelling systems: patterns of interaction and structural changes in ‘‘wasp-waist’’ ecosystems. – ICES Journal of Marine Science, 57: 603–618

de Graaf, M., L. G. Tilstra, P. Wang, and P. Stammes, 2012:, Retrieval of the aerosol direct radiative effect over clouds from spaceborne spectrometry, J. Geophys. Res., 117, D07207, doi:10.1029/2011JD017160.

de Graaf, M., N. Bellouin, L. G. Tilstra, J. Haywood, and P. Stammes, 2014: Aerosol direct radiative effect of smoke over clouds over the south- east Atlantic Ocean from 2006 to 2009, Geophys. Res. Lett., 41, 7723–7730, doi:10.1002/2014GL061103.

de Gouw, J. and C. Warneke, 2007: Measurements of volatile organic compounds in the Earth’s atmosphere using photon-transfer-reaction mass spectrometry. Mass Spec. Rev., 26, 223-257.

De Szoeke, C. Fairall, D. Wolfe, L. Bariteau, and P. Zuidema, 2010: Surface fluxobservations on the southeastern tropical Pacific Ocean and attribution of SST errors in coupled ocean-atmosphere models. J. Climate, 23, pp. 4152-4174.

De Szoeke, S. Yuter, D. Mechem, C. W. Fairall, C. Burleyson and P. Zuidema, 2012: Observations ofstratocumulus clouds and their effect on the eastern Pacific surface heat budget along 20S. J. Climate, 25, pp. 8542-8567. doi:10.1175/JCLI-D-11-00681.1

�2

Deser, C., A. Phillips, and M. Alexander, 2010: Twentieth century tropical sea surface temperature trends revisited. Geophys. Res. Lett., 37, L10701, doi:10.1029/2010GL043321

Dubovik, O., A. Smirnov, B. N. Holben, M. D. King, Y. J. Kaufman, T. F. Eck, and I. Slutsker, 2000: Accuracy assessments of aerosol optical properties retrieved from Aerosol Robotic Network (AERONET) sun and sky radiance measurements. J. Geophys. Res., 105, 9791–9806

Duynkerke, P. G. and Coauthors, 2004: Observations and numerical simula- tions of the diurnal cycle of the EUROCS stratocumulus case. Quart. J. Roy. Meteor. Soc., 130, 3269–3296.

Eck, T. F., et al., 2013: A seasonal trend of single scattering albedo in southern African biomass-burning particles: Implications for satellite products and estimates of emissions for the world’s largest biomass-burning source, J. Geophys. Res.., 118, doi:10.1002/jgrd.50500.

Faloona, I., Lenschow, D. H., Campos, T., Stevens, B., van Zanten, M., Blomquist, B., Thornton, D., Bandy, A., and Gerber, H.,2005: Observations of entrainment in eastern Pacific marine stratocumulus using three conserved scalars, J. Atmos. Sci., 62, 3268–3285, 2005

Fast, JD, WI Gustafson Jr., EG Chapman, RC Easter, JP Rishel, RA Zaveri, GA Grell, and MC Barth. 2011. The Aerosol Modeling Testbed: A Community Tool to Objectively Evaluate Aerosol Process Modules, Bulletin of the American Meteorological Society, 92, 343-360.

DOI:10.1175/2010BAMS2868.1Feingold, G., H. Jiang, and J. Y. Harrington, 2005: On smoke suppression of clouds in Amazonia.

Geophys. Res. Lett., 32, No. 2, L02804, 10.1029/2004GL021369.Feingold, G., and H. Siebert, 2009: Cloud-aerosol interactions from the micro to the cloud scale. Chapter

14 in Strungmann Forum report, vol. 2. Cambridge, MA: The MIT press. Fishman, J., K. Fakhruzzaman, B. Cros, and D. Mganga, 1991: Identification of widespread pollution in

the southern hemisphere deduced from satellite analyses. Science, 252, 1693-1696.Fishman, J., 1994: Experiment probes elevated ozone levels over the tropical south Atlantic Ocean.

Eos Trans. AGU, 75 (33), 380. Florenchie, P., J. Lutjeharms, C. Reason, S. Masson and M. Rouault, 2003: The source of Benguela

Ninos in the South Atlantic Ocean. Geophys. Res. Lett., 30, doi:10.1029/2003GL017172.

Gammelsrød, T., C. H. Batholomae, D. C. Boyer, V. L. L. Filipe, and M. J. O’Toole, 1998: Intrusion of warm surface water along the Angolan-Namibian coast in February–March 1995: The 1995 Benguela Nin o, S. Afr. J. Mar. Sci., 19, 51–56.

Garstang, M., P. D. Tyson, R. Swap, M. Edwards, P. Kållberg, and J. A. Lindesay, 1996: Horizontal and vertical transport of air over southern Africa, J. Geophys. Res., 101(D19), 23,721–23,736, doi:10.1029/ 95JD00844.

Golaz, J.-C., M. Salzmann, L. Donner, L. Horowitz, Y. Ming and M. Zhao, 2011: Sensitivity of the aerosol indirect effect to subgrid variability in the parameterization of the GFDL atmosphere general circulation model. J. Clim., 24, doi:10.1175/2010JCLI3945.1

Granier et al., 2011: Evolution of anthropogenic and biomass burning emissions of air pollutants at global and regional scales during the 1980–2010 period. Climatic Change. 109, p. 163-190. doi: 10.1007/s10584-011-0154-1

Grassl (1975): Albedo reduction and radioactive heating of clouds by absorbing aerosol particles. Beitr. Z. Phys. Atmos. 48, 199-210.

Hannay, C., D. L Williamson, J. J Hack, J. T Kiehl, J. G Olson, S. A Klein, C. S Bretherton, and M. Koehler ,2009: Evaluation of Forecasted Southeast Pacific Stratocumulus in the NCAR, GFDL and ECMWF Models. J. Climate, 22, 2871-2889 Haywood, J. M., S. R. Osborne, and S. J. Abel, 2004: The effect of overlying absorbing aerosol layers

on remote sensing retrievals of cloud effective radius and cloud optical depth. Q. J. R. Meteorol. Soc., 130, 779-800.

Haywood, J. M., and K. P. Shine, The effect of anthropogenic sulfate and soot on the clear-sky planetary radiation budget, Geophys. Res. Lett., 22, 603–606, 1995.

Hill, A., and S. Dobie, 2008: The impact of aerosols on non-precipitating stratocumulus. II: The semi-direct effect. Q. J. R. M. S., 134, 155-165, doi:10.1002/qj.277.

�3

Holben, B. N., et al., 2001: An emerging ground-based aerosol climatology: Aerosol optical depth from AERONET, J. Geophys. Res.,106(D11), 12,067–12,097, doi:10.1029/2001JD900014

Hu, Z.-Z., et al., 2011: Sensitivity of tropical climate to low-level clouds in the NCEP climate forecast system. Clim. Dyn., 36, p. 1795-1811, doi:10.1007/s00382-010-0797-z

Jiang, H., and G. Feingold, 2006: Effect of aerosol on warm convective clouds: Aerosol- cloud-surface flux feedbacks in a new coupled large eddy model. J. Geophys. Res., 111, D01202, doi:10.1029/2005JD006138.

Jones, A., Haywood, J., and Boucher, O., 2009: Climate impacts of geoengineering marine stratocumulus clouds, J. Geophys. Res., 114, D10106, doi:10.1029/2008JD011450.

Johnson, B., K. Shine and P. M. Forster, 2004: The semi-direct aerosol effect: Impact of absorbing aerosols on marine stratocumulus. Q. J. R. Meteorol. Soc., 130, pp. 1407-1422.

Johnson, B. T., 2005: Large-eddy simulations of the semidirect aerosol effect in shallow cumulus regimes, J. Geophys. Res., 110, D14206, doi:10.1029/2004JD005601.

IPCC, 2013: Climate Change 2013: The Physical Science Basis. Contribution of Working GroupI to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T. F., D. Qin, G.-K. Plattner, M. Tignor, S. K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P. M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, in press.

Kay, J.E., B.R. Hillman, S.A. Klein, Y. Zhang, B. Medeiros, R. Pincus, A. Gettelman, B.E. Eaton, J. Boyle, R. Marchand, and T.P. Ackerman, 2012: Exposing global cloud biases in the Community Atmosphere Model (CAM) using satellite observations and their corresponding instrument simulators. Journal of Climate, 25, 5190-5207, DOI: 10.1175/JCLI-D-11-00469.1.

Kazil, J., H. Wang, G. Feingold, A.D. Clarke, J.R. Snider, and A.R. Bandy, Chemical and aerosol processes in the transition from closed to open cells during VOCALS-Rex, Atmos. Chem. Phys. 11, 7491-7514, 2011.

Kazil, J., G. Feingold, H. Wang and T. Yamaguchi, 2014: On the interaction between marine boundary layer cellular cloudiness and surface heat fluxes. Atmos. Chem. Phys., 14, doi:10.5194/acp-14-18855-2014.

Kindel, B. C., P. Pilewskie, K. S. Schmidt, O. Coddington, and M. D. King, 2011: Solar spectral absorption by marine stratus clouds: Measurements and modeling, J. Geophys. Res., 116, D10203, doi:10.1029/2010JD015071

Kinne, S., D. O’Donnel, P. Stier, S. Kloster, K. Zhang, H. Schmidt, S. Rast, M. Giorgetta, T. F. Eck, and B. Stevens, 2013:, MAC-v1: A new global aerosol climatology for climate studies, J. Adv. Model. Earth Syst., 5, doi:10.1002/jame.20035

Klein, S.A. and Hartmann, D.L., 1993: The seasonal cycle of low stratiform clouds. Journal of Climate, 6, pp. 1587–1606

Koch, D., and A. D. Del Genio, 2010:, Black carbon semi-direct effects on cloud cover: Review andsynthesis, Atmos. Chem. Phys., 10, 7685–7696

Koffi, B., et al., 2012:, Application of the CALIOP layer product to evaluate the vertical distribution of aerosols estimated by global models: AeroCom Phase I results, J. Geophys. Res., 117, D10201, doi:10.1029/2011JD016858.

Koren, I., Y. J. Kaufman, L. A. Remer, J. V. Martins, 2004: Measurement of the effect of Amazon smoke on inhibition of cloud formation. Science 303: 1342 – 1345, doi: 10.1126/science.1089424.

Lauer, A. and K. Hamilton, 2013: Simulating Clouds with Global Climate Models: A Comparison of CMIP5 results with CMIP3 and satellite data. J. Clim., 26, doi:10.1175/jcli-d-12-00451.1, p. 3823-

Lee, S.-S., G. Feingold, A. McComiskey, T. Yamaguchi, I. Koren, J. V. Martins and H. Yu, 2014: Effect of gradients in biomass burning aerosol on circulations and clouds. J. Geophys. Res., doi:10.1002/2014JD021819.

Li, Z., P. Zuidema, and P. Zhu, 2014: Simulated convective invigoration processes at trade-wind cumulus cold pool boundaries. J. Atmos.Sci., 71, p. 2823-2841. doi:10.1175/jas-d-13-0184.

Li, Z., P. Zuidema, and P. Zhu, under review: On the sensitivity of shallow cloud cold pool convection to microphysics. J. Atmos. Sci.

�4

Lin, B., Patrick Minnis , Tai-Fang Fan, Yongxiang Hu and Wenbo Sun, 2010: Radiation characteristics of low and high clouds in different oceanic regions observed by CERES and MODIS, Int. J. Remote Sens., 31:24, 6473-6492, DOI: 10.1080/01431160903548005

Loeb, N. G., and G. L. Schuster, 2008: An observational study of the relationship between cloud, aerosol and meteorology in broken low-level cloud conditions, J. Geophys. Res., 113, D14214, doi: 10.1029/2007JD009763

Loeb, Norman G., Wenying Su, 2010: Direct Aerosol Radiative Forcing Uncertainty Based on a Radiative Perturbation Analysis. J. Climate, 23, 5288–5293.

Magi, B. I., Q. Fu, J. Redemann, and B. Schmid, 2008: Using aircraft measurements to estimate the magnitude and uncertainty of the shortwave direct radiative forcing of southern African biomass burning aerosol, J. Geophys. Res., 113, D05213, doi:10.1029/2007JD009258

Mari, C., G. Cailley, L. Corre, M. Saunois, J. Attie, V. Thouret and A. Stohl, 2008: Tracing biomass burning plumes from the Southern Hemisphere during the AMMA 2006 wet season experiment. Atmos. Chem. Whys., 8, 3951-3961, doi:atmos-chem-phys.net/8/3951/2008/

McFarquhar, G.M., S. Platnick, L. Di Girolamo, H. Wang, G. Wind, and G. Zhao, 2004a: Remotely sensed observations of aerosol indirect effects in the Indian Ocean.Geophys. Res. Lett., 31, L21105, doi:10.1029/2004GL020412.

McFarquhar, G. M., S. Platnick, L. D. Di Girolamo, H. Wang, G. Wind, and G. Zhao, 2004b: Trade wind cumuli statistics in clean and polluted air over the Indian Ocean from in situ and remote sensing measurements. Geophys. Res. Lett., 31, L21105, doi:10.1029/2004GL020412

Mechoso, R., et al., 2014: Ocean-Cloud-Atmosphere-Land interactions in the Southeastern Pacific: The VOCALS program. Bull. Am. Meteor. Soc., 94, doi:10.1175/BAMS-D-11-00246.1

Medeiros, B., 2011: Comparing the southern hemisphere stratocumulus decks in the Community Atmosphere Model. Newsletter, U.S. CLIVAR Variations, 9, World Climate Research Programme, 5-7.

Medeiros, B. D L Williamson, C Hannay, J Olson., 2012: Southeast Pacific stratocumulus in the Community Atmosphere Model. J. Climate, 25, 6175-6192 Menon, S., J. Hansen, L. Nazareno, and Y. Luo, 2002: Climate effect of black carbon aerosols in China

and India. Science, 297, 2250-2253.Meyer, K., S. Platnick, L. Oreopoulos, D. Lee, 2013: Estimating the direct radiative forcing of ab- sorbing

aerosols overlying marine boundary layer clouds in the southeast Atlantic using MO- DIS and CALIOP. J. Geophys. Res., DOI: 10.1002/jgrd.50449

Moeng, C.-H., and Coauthors, 1996: Simulation of a stratocumulus- topped planetary boundary layer: Intercomparison among different numerical codes. Bull. Amer. Meteor. Soc., 77, 261–278.

Mohrholz, V., M. Schmidt, and J. R. E. Lutjeharms, 2001: The hydrography and dynamics of the Angola-Benguela Frontal Zone and environment in April 1999, S. Afr. J. Mar. Res., 97, 199–208

Moran, K., S. Pezoa, C. Fairall, C. Williams, T. Ayers, A. Brewer, S. de Szoeke, and V. Ghate, 2011: A motion-stabilitzed W-band radar for shipboard observations of marine boundary-layer clouds. Boun. Layer Meteorol. doi: 10.1007/s10546-011-9674-5.

Myrhe, G. et al., 2013: Radiative forcing of the direct aerosol effect from AeroCom Phase II simulations. Atmos. Chem. Phys, 13, p. 1853-1877, doi:10.5194/ acp-13/1853-2013.

Neale, R. B. C. Hannay, G. Danabasoglu, M. Holland, D. Lawrence, A. Gettelman, S. -S. Park and P. J. Rasch, 2013: Coupled simulations from CESM1 using the Community Atmosphere Model version 5 (CAM5). J. Climate, under review

Neggers, R. A. J., A. P. Siebesma, T. Heus, 2012: Continuous Single-Column Model Evaluation at a Permanent Meteorological Supersite. Bull. Amer. Meteor. Soc., 93, 1389–1400. doi: http://dx.doi.org/10.1175/BAMS-D-11-00162.1

Oktem, R., Prabhat, J. Lee, A. Thomas, P. Zuidema, and D. Romps, 2014: Stereo photogrammetry of oceanic clouds. J. Atmos. Ocean. Tech., 31, p.1482-1501. doi:10.1175/jtech-d-13-00224

Painemal, D., 2011: Microphysical and radiative properties of the southeast Pacific stratocumulus cloud

�5

deck. Ph.D. Thesis, University of Miami.Painemal, D., and P. Zuidema, 2011: Assessment of MODIS cloud effective radius and optical thickness retrievals over the Southeast Pacific with VOCALS-REx in situ measurements, J. Geophys. Res., 116, D24206, doi:10.1029/2011JD016155. Painemal, D., and P. Minnis, 2012: On the dependence of albedo on cloud microphysics over marine stratocumulus clouds regimes determined from Clouds and the Earth’s Radiant Energy System (CERES) data, J. Geophys. Res., 117, D06203, doi:10.1029/2011JD017120. Painemal D., P. Minnis, K. Ayers, and L. O’Neill, 2012: GOES-10 microphysical retrievals in marine warm clouds: Multi-instrument validation and daytime cycle over the Southeast Pacific. J. Geophys. Res. 117, D19212, doi:10.1029/2012JD017822. Painemal D., and P. Zuidema, 2013: The first aerosol indirect effect quantified through airborne remote sensing during VOCALS-REx, Atmos. Chem. Phys.., 13, 917-931 Painemal D., S. Kato, and P. Minnis, 2014: Biomass burning and boundary layer regulation in the southeast Atlantic warm cloud microphysics, J. Geophys. Res. Petters, J. L., H. Jiang, G. Feingold, D. L. Rossiter, D. Khelif, L. C. Sloan, and P. Y. Chuang, 2013:

A comparative study of the response of modeled non-drizzling stratocumulus to meteorological and aerosol perturbations. Atmos. Chem. Phys., 13, 2507-2529, doi:10.5194/acp-13-2507-2013

Pilewskie, P., J. Pommier, R. Bergstrom, W. Gore, S. Howard, M. Rabbette, B. Schmid, P. V. Hobbs, and S. C. Tsay, 2003: Solar spectral radiative forcing during the Southern African Regional Science Initiative, J. Geophys. Res., 108(D13), 8486, doi:10.1029/2002JD002411.

Pincus, R., C. P. Batstone, R. J. P. Hofmann, K. E. Taylor, and P. J. Glecker, 2008:, Evaluating the present-day simulation of clouds, precipitation, and radiation in climate models, J. Geophys. Res., 113, D14209, doi:10.1029/2007JD009334

Ramanathan, V., et al., 2001: Indian Ocean Experiment: An integrated assessment of climate forcing and effects of the great Indo-Asian haze, J. Geophys. Res., 106, 28,371–28,398.

Ramanathan , V., G. Carmichael, 2008: Global and regional climate changes due to black carbon, Nature Geoscience, 1, 221-227.

Randles, C. and V. Ramaswamy, 2010: Direct and semi-direct impacts of absorbing biomass burning aerosol on the climate of southern Africa: A Geophysical Fluid Dynamics Laboratory GCM sensitivity study. Atmos. Chem. Phys., 10, p. 9819-9831, doi:10.5194/acp-10-9819-2010.

Rauber, R. M., and Coauthors, 2007: Rain in shallow cumulus over the ocean: The RICO campaign. Bull. Amer. Meteor. Soc., 88, 1912–1928

Remer, L., 2009: Smoke above clouds. Nature Geo., 2, p. 167-168.Richter, I., and C. R. Mechoso, 2004:, Orographic influences on the annual cycle of Namibian

stratocumulus clouds, Geophys. Res. Lett., 31, L24108, doi:10.1029/2004GL020814 Ross, K. E., S. J. Piketh, R. T. Bruintjes, R. P. Burger, R. J. Swap, and H. J. Annegarn, 2003:, Spatial and

seasonal variations in CCN distribution and the aerosol-CCN relationship over Southern Africa,J. Geophys. Res., 108, 8481. Rouault, M., P. Florenchie, N. Fauchereau, and C. J. C. Reason, 2003: South east tropical Atlantic warm

events and southern African rainfall, Geophys. Res. Lett., 30(5). Russell, P. B., S. Kinne and R. Bergstrom, 1997: Aerosol climate effects: Local radiative forcing and

column closure experiments, J. Geophys. Res., 102, 9397-9407. Saide, P. E. and Coauthors, 2012: Evaluating WRF-Chem aerosol indirect effects in Southeast Pacific

marine stratocumulus during VOCALS-REx. Atmos Chem Phys, 12, 3045–3064, doi:10.5194/acp-12-3045-2012.

Sakaeda, N., R. Wood, and P. Rasch, 2011: Direct and semidirect aerosol effects of southern African biomass-burning aerosol, J. Geophys. Res., 116, D12205, doi:10.1029/2010JD015540.

Sandu, I., B. Stevens and R. Pincus, 2010: On the transitions in marine boundary layer clouds. Atmos. Chem. Phys., 10, p. 2377-2391, doi:10.5194/acp-10-2377-2010.

Schmidt, K. S., G. Feingold, P. Pilewskie, H. Jiang, O. Coddington, and M. Wendisch, 2009: Irradiance in polluted cumulus fields: Measured and modeled cloud-aerosol effects, Geophys. Res. Lett., 36, L07804, doi:10.1029/2008GL036848.

Schmidt, K. S., Bierwirth, E., Coddington, O., Pilewskie, P., Wendisch, M., Bergstrom, R., Gore, W., Redemann, J., Livingston, J., and Russel, P., 2010: A new method for deriving aerosol solar

�6

radiative forcing and its first application within MILAGRO/INTEX-B, Atmos. Chem. Phys., 10, 7829–7843, doi:10.5194/acp- 10-7829-2010, 10, 2731-2767

Schulz, M., et al., 2006: Radiative forcing by aerosols as derived from the AeroCom present-day and pre-industrial simulations. Atmos. Chem. Phys, 6, 5225-5246.

Schwarz, J. P., et al., 2006: Single-particle measurements of midlatitude black carbon and light-scattering aerosols from the boundary layer to the lower stratosphere, J. Geophys. Res., 111(D16), 207, doi:10.1029/ 2006JD007076.

Schwarz, J. P., et al., 2008a: Coatings and their enhancement of black carbon light absorption in the tropical atmosphere, J. Geophys. Res., 113(D3), 203, doi:10.1029/2007JD009042.

Schwarz, J. P., et al., 2008b:, Measurement of the mixing state, mass, and optical size of individual black carbon particles in urban and biomass burning emissions, Geophys. Res. Lett., 35(13), 810, doi: 10.1029/ 2008GL033968.

Seidel, F. C. and Popp, C.2012: Critical surface albedo and its implications to aerosol remote sensing, Atmos. Meas. Tech., 5, 1653-1665, doi:10.5194/amt-5-1653-2012.

Shannon, L. V., A. J. Boyd, G. B. Brundrit, and J. Taunton-Clark, On the existence of an El Nin o-type phenomenon in the Benguela system, J. Mar. Res., 44, 495–520, 1986.

Sinha, P., P. V. Hobbs, R. J. Yokelson, I. T. Bertschi, D. R. Blake, I. J. Simpson, S. Gao, T. W. Kirchstetter, and T. Novakov, 2003: Emissions of trace gases and particles from savanna fires in southern Africa, J. Geophys. Res., 108(D13), 8487, doi:10.1029/2002JD002325.

Small, J. D., and P. Y. Chuang, 2009: New observations of precipitation initiation in warm cumulus. J. Atmos. Sci., 65, p. 2972-2982. doi:10.1175/2008/JAS2600.1

Small, J. D., P. Y. Chuang, G. Feingold, and H. Jiang. 2009:, Can aerosol decrease cloud lifetime? Geophys. Res. Lett., 36, L16806, doi:10.1029/2009GL038888.

Soden, B. J., and G. A. Vecchi, 2011:, The vertical distribution of cloud feedback in coupled ocean‐atmosphere models, Geophys. Res. Lett., 38, L12704, doi:10.1029/2011GL047632.

Solomon, A., M.D. Shupe, P.O.G. Persson, and H. Morrison, 2011: Moisture and dynamical interactions maintainining decoupled Arctic mixed-phase stratocumulus in the presence of a humidity inversion. Atmos. Chem. Phys., 11, 10127-10148, doi:10.5194/acp-11-10127-2011.

Sorooshian, A., G. Feingold, M. D. Lebsock, H. Jiang, and G. Stephens, 2009:, On the precipitation susceptibility of clouds to aerosol perturbations, Geophys. Res. Lett., 36, L13803, doi:10.1029/2009GL038993.

Sorooshian, A., G. Feingold, M. D. Lebsock, H. Jiang, and G. L. Stephens, 2010:, Deconstructing the precipitation susceptibility construct: Improving methodology for aerosol‐cloud precipitation studies, J. Geophys. Res., 115, D17201,doi:10.1029/2009JD013426.

Stevens, B., and Coauthors, 2005: Evaluation of large-eddy simulations via observations of nocturnal marine stratocumulus. Mon. Wea. Rev., 133, 1443–1462.

Stevens, B. and G. Feingold, 2009: Untangling aerosol effects on clouds and precipitation in a buffered system. Nature, 46, 607-613.

Stier P.,, N. A. J. Schutgens, N. Bellouin, H. Bian, O. Boucher, M. Chin, S. Ghan, N. Huneeus, S. Kinne, G. Lin, X. Ma, G. Myhre, J. E. Penner, C. A. Randles, B. Samset, M. Schulz, T. Takemura, F.

Yu, H. Yu, and C. Zhou, 2013: Host model uncertainties in aerosol radiative forcing estimates: Results from the AeroCom Prescribed intercomparison study Atmos. Chem. Phys., 13, 3245–3270, 2013,doi:10.5194/acp-13-3245-2013

Stohl, A., Forster, C., Frank, A., Seibert, P., and Wotawa, G. 2005: Technical note: The Lagrangian particle dispersion model FLEXPART version 6.2, Atmos. Chem. Phys., 5, 2461–2474, doi:10.5194/acp-5-2461-2005.

Swap, R. et al., 2003: Africa burning: A thematic analysis of the Southern African Regional Science Initiative (SAFARI 2000). J. Geophys. Res., 108, doi:10.1029/2003JD003747.

Ten Hoeve, J. E., M. Z. Jacobson, and L. A. Remer, 2012: Comparing results from a physical model with satellite and in situ observations to determine whether biomass burning aerosols over the Amazon brighten or burn off clouds. J. Geophys. Res., 117, D08203. Terai, C., R. Wood, D. C. Leon, and P. Zuidema, 2012: Does precipitation susceptibility vary with

increasing cloud thickness in marine stratocumulus? Atmos Chem Phys. 12, 4567-4583.

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Tokinaga, H. and S.-P. Xie, 2011: Weakening of the equatorial Atlantic cold tongue over the past six decades. Nature Geo., 4, doi:10.1038/ngeo1078.

Toniazzo, T. and S. Woolnough, 2013: Development of warm SST errors in the southern tropical Atlantic in CMIP5 decadal hindcasts, Clim. Dyn., doi:10.1007/s00382-013-1691-2

Twohy, C. H., J. Anderson, D. Toohey, M. Andrejczuk, A. Adams, M. Lytle, R. George, R. Wood, P. Saide, S. Spak, P. Zuidema and D. Leon, 2013: Impacts of aerosol particles on the microphysical and radiative properties of stratocumulus clouds over the Southeast Pacific ocean. Atmos. Chem. Phys., 13, doi:10.5194/acp-13-2541-2013

Twomey, S.: The influence of pollution on the shortwave albedo of clouds, J. Atmos. Sci., 34, 1149–1152, 1977.

van der Werf, G. R., Randerson, J. T., Giglio, L., Collatz, G. J., Kasibhatla, P. S., and Arellano Jr., A. F., 2006: Interannual variability in global biomass burning emissions from 1997 to 2004,Atmos. Chem. Phys., 6, 3423–3441, 2006, 3648,

van der Werf, et al., 2010: Global fire emissions and the contribution of deforestation, savanna, forest, agricultural and peat fires (1997-2009), Atmos. Chem. Phys., 10, 11707–11735, 2010 doi:10.5194/acp-10-11707-2010

Voigt, B. Stevens, S. Bony, O. Boucher, 2013 : Easy Aerosol - a modeling framework to study robustness and sources of uncertainties in aerosol-induced changes of the large-scale atmospheric circulation. available through http://www.wcrp-climate.org/index.php/gc-clouds-circulation-

activities/gc4-clouds-initiatives/368-gc-clouds-inititative3-easy-aerosol

Wang, H., and G.M. McFarquhar, 2008: Modeling aerosol effects on shallow cumulus convection under various meteorological conditions observed over the Indian Ocean. J. Geophys. Res., 113, D20201, doi:10.1029/2008JD009914.

Wang H., and G. Feingold, 2009: Modeling mesoscale cellular structure and drizzle in marine stratocumulus. Part II: The microphysics and dynamics of the boundary region between open and closed cells. J. Atmos. Sci., 66, 3257 - 3275.

Wang, X., P. Zuidema, and P. Zhu, 2012: What environmental conditions encourage shallow mesoscale organization? AGU Conf. Abstract A51C-0072, Dec. 3-7, 2012, San Fran., CA

Waquet, F., F. Peers, F. Ducos, P. Goloub, S. Platnick, J. Riedi, D. Tanre and F. Thieuleux, 2013: Global analysis of aerosol properties above clouds. Geophys. Res. Lett., doi:10.1002/2013GL057482.

Wen, G., A. Marshak, R. F. Cahalan, L. A. Remer, and R. G. Kleidman, 2007:, 3-D aerosol-cloud radiative interaction observed in collocated MODIS and ASTER images of cumulus cloud fields, J. Geophys. Res., 112, D13204, doi:10.1029/2006JD008267

Wilcox, 2010: Stratocumulus cloud thickening beneath layers of absorbing smoke aerosol. Atmos. Chem. Phys., 10, pp. 11769-11777.

Wilcox, E. M.,2012: Direct and semi-direct radiative forcing of smoke aerosols over clouds, Atmos. Chem. Phys., 12, 139-149, doi:10.5194/acp-12-139-2012, 2012

Wood, R. ,2007: Cancellation of aerosol indirect effects in marine strato- cumulus through cloud thinning, J. Atmos. Sci., 64, 2657–2669, doi:10.1175/JAS3942.1

Wood, R., C. S. Bretherton, D. Leon, A. D. Clarke, P. Zuidema, G. Allen, and H. Coe, 2011: An aircraft case study of the spatial transition from closed to open mesoscale cellular convection over the Southeast Pacific. Atmos. Chem. Phys., 11, 2341-2370, 2011.

Wood, R., C. R. Mechoso, C. S. Bretherton, R. A. Weller, B. Huebert, F. Straneo, B. A. Albrecht, H. Coe, G. Allen, G. Vaughan, P. Daum, C. Fairall, D. Chand, L. Gallardo Klenner, R. Garreaud, C. Grados Quispe, D. S. Covert, T. S. Bates, R. Krejci, L. M. Russell, S. de Szoeke, A. Brewer, S. E. Yuter, S. R. Springston, A. Chaigneau, T. Toniazzo, P. Minnis, R. Palikonda, S. J. Abel, W. O. J. Brown, S. Williams, J. Fochesatto, J. Brioude, 2011b: The VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx): goals, platforms, and field operations. Atmos. Chem. Phys., 11, 627-654

Wood. R., D. Leon, M. Lebsock, J. R. Snider, and A. D. Clarke, 2014: Precipitation driving of droplet concentration variability in marine low clouds, J. Geophys. Res.

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Wyant, M. C., and Coauthors, 2007: A single-column model intercomparison of a heavily drizzling stratocumulus-topped boundary layer. J. Geophys. Res., 112, D24204, doi:10.1029/ 2007JD008536.

Wyant, M. C., R. Wood, C. S. Bretherton, C. R. Mechoso, J. Bacmeister, M. A. Balmaseda, B. Barrett, F. Codron, P. Earnshaw, J. Fast, C. Hannay, J. W. Kaiser, H. Kitagawa, S. A. Klein, M. Köhler, J. Manganello, H. –L. Pan, F. Sun, S. Wang, and Y. Wang, 2010: The PreVOCA experiment: modeling the lower troposphere in the Southeast Pacific. Atmos. Chem. Phys., 10, 4757-4774, doi:10.5194/acp-10-4757-2010

Xue, H., G. Feingold, and B. Stevens, 2008:, Aerosol effects on cloud,precipitation, and the organization of shallow cumulus convection, J. Atmos. Sci., 65, 392–406, doi:10.1175/2007JAS2428.1.

Yamaguchi, T.,W. A. Brewer and G. Feingold, 2013: Evaluation of modeled stratocumulus-capped boundary layer with shipborne data. J. Atmos. Sci., 70, p. 3985-3919, doi:10.1175/JAS-D-13-050.1

Yu, H., Y.J. Kaufman, M. Chin, G. Feingold, L. Remer, T. Anderson, Y. Balkanski, N. Bellouin, O. Boucher, S. Christopher, P. DeCola, R. Kahn, D. Koch, N. Loeb, M.S. Reddy, M. Schulz, T. Takemura, and M. Zhou, 2006:. A review of measurement-based assessments of the aerosol direct radiative effect and forcing Atmos. Chem. Phys, 6, 613-666, 2006

Zhang, J. and J. S. Reid, 2010: A decadal regional and global trend analysis of the aerosol optical depth using data-assimilation grade over-water MODIS and Level 2 MISR aerosol products Atmos. Chem. Phys., 10, 10949–10963, doi:10.5194/acp-10-10949-2010

Zhu, P., and Coauthors, 2005: Intercomparison and interpretation of single-column model simulations of a nocturnal stratocumulus- topped marine boundary layer. Mon. Wea. Rev., 133, 2741– 2758.

Zhu, P. and P. Zuidema, 2009: On the use of PDF schemes to parameterize sub-grid clouds. Geophys. Res. Lett.,36, L05807, doi: 10.1029/2008GL036817.

Zuidema, P., H. Xue, and G. Feingold, 2008: Shortwave radiative impacts from aerosol effects on shallow marine cumuli. J. Atmos. Sci., 65, pp. 1979-1990.

Zuidema, 2011: Coupled ocean-land-atmosphere processes in the tropical Atlantic, Exchanges, 16 #1, p. 12-13.

Zuidema, P., Z. Li, R. Hill, L. Bariteau, B. Rilling, C. Fairall, W. A. Brewer, B. Albrecht and J. Hare, 2012a: On trade-wind cumulus cold pools. J. Atmos. Sci., 69, pp. 258-277, doi:10.1175/jas-d-11-0143.

Zuidema, P., D. Leon, A. Pazmany, and M. Cadeddu, 2012: Aircraft millimeter-wave retrievals of cloud liquid water path during VOCALS-REx. Atmos. Chem. Phys., 12, 355–369, doi:10.5194/acp-12-355-2012.

Zuidema, P., S. Kramer, S. Purdue, R. Delgadillo, J. Prospero, B. Albrecht, K. Voss, manuscript in prep: New observations of Saharan dust events over Miami.

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Facilities, Equipment and Other Resources

Table 2: Field facilities requested, sponsors, stratus, cost estimates, personnel. Further description of NCAR C-130 instruments is provided in Table 3.

Facility/Instrument Sponsor & (Status)

TBS: To Be Submitted

Cost Estimate

(NSF only)

Contact

NCAR C-130Base facility (cloud and aerosol

microphysics, dynamics, turbulence)Counterflow Virtual Impacter (CVI)

flight hours (120 hours research time)

NSF Deployment

(TBS)

2,039,338 Paquita Zuidema (U Miami)

Cindy Twohy (CVI; NWRA)

NCAR C-130Hiaper Airborne Radiation Package (HARP)

to adapt for C-130

NSF Deployment

(TBS)

92,445 Sebastian Schmidt (CU)/

Sam Hall (NCAR)

NCAR C-130Trace Organic Gas Analyzer (TOGA)

NSF Deployment

(TBS)

156,001 Elliot Atlas (U Miami)

NCAR C-130Fast Ozone, CO, CO2, CH4

NSF Deployment

(TBS)

165,763 Teresa Campos (NCAR)

NCAR C-130Airborne Vertical Atmospheric Profiling

System (AVAPS; 200 dropsondes)

NSF Deployment

(TBS)

250,312 Paquita Zuidema(U Miami)

NCAR C-130Wyoming Cloud RadarWyoming Cloud Lidar

NSF(TBS)

81.4K Jeffrey French(U Wyoming)

NCAR1 GPS Advanced Upper-Air Sounding System (GAUS) @ Ascension Island325 sondes, materials&shipping only

NSF Deployment

(TBS)

164,043 Paquita Zuidema

(U Miami)

Logistical support (NCAR FPS)Field Catalog, Data Management, limited

Project Management & Operations Support, Education and Outreach

NSF Special (TBS)

400,000 Brigitte Baeuerle(NCAR)

Facility/Instrument Sponsor & (Status)

TBS: To Be Submitted

Cost Estimate

(NSF only)

Contact

R/V Polarstern*motion-stabilized Doppler cloud radar &

radiosondes*if cruise timing is advantageous

NOAA(TBS)

N/A Chris Fairall(NOAA ESRL-

PSD)

NASA P-3 and ER-2* (ORACLES)*year of ER-2 deployment not finalized; P-3

deployments in 2016, 2017, 2018

NASAFunded

$30M Jens Redemann(NASA-Ames)

AERONET sun photometers@ St. Helena, Angola, Ascension

NASAFunded

N/A Brent Holben(NASA)

UK BAE-146 (CLARIFY)

August-September 2016 only

UK-NERCFunded

$7M Jim Haywood (UK Met Office/

Exeter)

DOE AMF1 (LASIC)June 1, 2016-May 31, 2017 only

Ascension Island

DOE ARMFunded

$30M P. Zuidema (U Miami)

DOE AMF1 (LASIC2)June 1, 2017 - October 31, 2017

Ascension Island

DOE ARMTBS

N/A P Zuidema (U Miami)

Surface-based Instrumentation on St. Helena (CLARIFY)

August-September 2016 onlyDoppler lidar, microwave radiometer, 94 GHz cloud radar, radiosondes, LW&SW

broadband radiometers, UAV, Grimm spectrometer

UK-NERCFunded

N/A Jim Haywood/ Eleanor Highwood

(UK Met Office Meteorological Research Unit,

Cardington)

Radio&Ozonesondes, St. HelenaSeptember, 2017

NSF-ChemTBS

N/A Gregory Jenkins(Howard U.)

PIRATA radiation and flux buoy @ 8E, 6S EU/S. Africa Funded

N/A Noel Keenlyside (U Bergen)/

Matthieu Rouault (U S. Africa)

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Table 3: NCAR C-130 Remote Sensing, Cloud and Chemistry InstrumentationInstrument/home Function Funding

SourceInvestigator

Aerosol Mass Spectrometer(UCRiverside)

aerosol sizing and composition

NSF-Chem Roya Bahreini (UC Riverside)

cavity-attenuated phase-shift spectrometer (UCRiverside)

optical extinction and scattering at 450 nm

NSF-Chem Roya Bahreini (UC Riverside)

Scanning Mobility Particle Sizer (SMPS/NCAR)

8-120 nm aerosol sizing

Deployment Pool James Smith (NCAR)

TSI-3025 (Wyoming) aerosol sizing and calibration

NSF-Chem Jeff Snider (UWyoming)

DMT cloud condensation nuclei counter

CCN as a function of supersaturation

NSF-PDM Greg Roberts(Scripps)

Hiaper Airborne Radiation Package (NCAR; to adapt for the C-130)

spectral irradiance measurements 280-2400 nm

Deployment Pool Sebastian Schmidt(CU)/Sam Hall (NCAR)

Wyoming Cloud Radar (Wyoming/NCAR)

cloud microphysics and macrophysics

Deployment Pool David Leon (UWyoming)

Wyoming Cloud Lidar (Wyoming/NCAR)

aerosol and cloud vertical structure

Deployment Pool Jeffrey Snider (UWyoming)

Muti-function Airborne Raman Lidar (MARLi)

aerosol and moisture layer remote sensing

NSF-PDM Zhien Wang (UWyoming)

CDP, King, FSSP, Gerber cloud probes

in-situ drop size distribution, LWC

Deployment Pool NCAR RAF

Giant Nuclei Impactor (GNI) 1-1000 micron aerosol sampling

NCAR base Jorgen Jensen (NCAR)

Phased Doppler Interferometer

in-situ drop size distribution

NSF-ATM Patrick Chuang (UC-Santa Cruz)

TSI-3760, DMT-PCASP, DMT-FSSP300, UHSAS wing tip probe

in-situ aerosol sizing Deployment Pool NCAR RAF

Streaker for SEM, 3-stage micro-impactor for TEM & NanoSIMS

sized ambient and cloud residue aerosol images

NSF-Chem Jim Anderson (ASU)

Photoacoustic Absorption/Cavity RingDown (PAS-CRD@NOAA)

aerosol absorption/scattering

NSF-Chem or NOAA

Daniel Murphy (NOAA)/Shane Murphy (U Wyoming)

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Single-Particle Soot Photometer (SP2)

black carbon mass and mixing state

NSF-Chem or NOAA

Joshua Schwarz (NOAA)

Trace Organic Gas Analyzer (TOGA)

trace gases; emission characterization

Deployment Pool Eliott Atlas (UMiami)/Eric Apel (NCAR)

Atmospheric Pressure Ionization Mass Spectrometer (APIMS)

DMS measurements for entrainment studies

NSF-Chem Byron Blomquist (CIRES)

UV Resonance fluorescence CO emissions Deployment Pool Teresa Campos NCAR)

Cavity Output Spectrometer (OA-ICOS)

CO fluxes+emissions NSF-Chem Byron Blomquist (CIRES)

Picarro cavity ring-down spectroscopy (CRDS)

CO2 + CH4 fluxes+emissions

Deployment Pool Teresa Campos (NCAR)

NO chemiluminescence Fast O3 concentration & flux

Deployment Pool Teresa Campos (NCAR)

Picarro cavity-enhanced tunable diode laser abs. spec.

water vapor isotope analysis

NSF-ATM David Noone(Oregon State U)

Counterflow Virtual Impactor cloud composition and residual sizes

Deployment Pool/NSF-ATM

Cynthia Twohy (NWRA)

Airborne Vertical Atmospheric Profiling System (AVAPS; NCAR)

thermodynamic profile characterization

Deployment Pool Zuidema (UMiami)

Miilli/microwave radiometer (lease)

cloud liquid water path and water vapor path

NSF-PDM Zuidema (UMiami)

Wideband Integrated Bioaerosol Sensor (WIBS)

biological particle detection

NSF-ATM Cynthia Twohy (NWRA)

Instrument/home Function Funding Source

Investigator

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Section J:Supplementary Documents: Participants, Roles, Anticipated Sponsors

Cloud-smoke-radiations interactions during ONFIRE

Paquita Zuidema, U of MiamiAnticipated Sponsor - NSF

PI Zuidema will have overall responsibility for the field management of the NCAR C-130 deployment during ONFIRE, of the radiosonde launching from Ascension Island (be it funded through NSF or DOE), and for the public outreach and broader impact ONFIRE contribution. This will be done in coordination with the broader ONFIRE science team, the NSF C-130 aircraft manager, NCAR EOL, and the NSF project office. Zuidema will also liase with the NASA ORACLES, UK CLARIFY, and DOE LASIC (and LASIC2 if funded) campaigns and its mission scientists. Mission planning for the C-130 plane will be done in coordination with the ONFIRE investigator team, of whom others will also serve as mission scientists (e.g., I. Faloona for the entrainment missions; Atlas and Schwarz for some of the survey missions). Following the field phase, Zuidema and a postdoctoral research associate will work on data synthesis and analysis. This will focus on testing aerosol-cloud interaction hypotheses (H2-H3) using the C-130 datasets from both the survey and entrainment flights within analyses that distinguish the aerosol impact from the meteorological effects. The robust features of the cloud behavior include consideration of cloud microphysics, precipitation, boundary layer and free tropospheric thermodynamics (stability and moisture profiles) and dynamics (vertical velocity profiles and connection to turbulent kinetic energy at cloud top), the aerosol vertical structure (i.e. within and above the boundary layer) and surface fluxes. The island data will be coordinated with the island AERONET data and satellite data as well as trajectories to characterize cloudy boundary layer evolution under varying aerosol loadings. Datasets useful for model initialization (large eddy simulations and single column models) and model intercomparison (large-scale models including AEROCOM) will be constructed.

Collaborative Research: Field Measurements of Aerosol-Cloud Interactions Involving Biomass Burning and Other Aerosols in the Southeast Atlantic.

James Anderson (Arizona State University) and Cynthia Twohy (NorthWest Research Associates)

Anticipated Sponsor: NSF-ATM, Estimated Budget:~ $100K/year/PI, or $600K total.

This region of the southeast Atlantic involves the interaction between biomass burning aerosols and marine stratiform clouds, with the added complexity of light-absorbing carbon (LAC) aerosols above the boundary layer altering the temperature profile of the free troposphere. Our interest is to examine both the role of biomass burning and related aerosols as nuclei of cloud droplets and also the range of chemical and physical properties that might relate to a range of aerosol optical properties. A counterflow virtual impactor will be used to separate hydrometeors from interstitial aerosol, and the droplet residual particles will be measured by a variety of methods. This includes in-situ measurements of particle number, size, and LAC and post-experiment individual particle analysis by electron microscopy and ion beam techniques for physical and chemical characteristics. If space is available upon the C-130, we will also pursue collaborations to measure fluorescent bioaerosol particles with a Wideband Integrated Bioaerosol Sensor (WIBS), since these particles may be important for ice nucleation in convective clouds to the north of the study region.

Collection of ambient (below and above cloud) and cloud residual particles, with subsequent automated SEM and high resolution imaging and chemical analysis by electron microprobe will be the focus of this proposal. We will examine individual particles with regard to chemical speciation, composition, mixing state, and size distributions, and determine their relationship to the properties of stratocumulus clouds. The internal structure and physical/chemical characteristics of submicron black and brown carbon will be examined by transmission electron microscope (TEM). This work will supplement information on light absorbing carbon provided by the real-time SP-2 instrument, as well as generate size distributions of non-volatile organic, sulfate, sea-salt, and mineral dust aerosols. In addition, mixing state and shape of individual particles can be observed for more information on aerosol processing and radiative properties.

Our recent TEM work on single-particle black and brown carbon have shown that the ratio of C-C bonding to C-H bonding is related to the imaginary refractive index and can be measured with electron energy loss spectroscopy (EELS). NanoSIMS analysis will be employed to address the ratio of carbon to hydrogen in LAC, similarly related to the imaginary refractive index. The experiment provides an opportunity to expand our work on individual particle optical properties of East Asian LAC of mostly industrial origin to a very different region with biomass burning LAC. The characteristics affecting optical properties may also affect CCN properties.

NAME:  Elliot  Atlas  

INSTITUTION:  Rosenstiel  School  of  Marine  and  Atmospheric  Sciences  

POTENTIAL  SPONSOR:  NSF  

 

Scientific  Interests:    

•  Emissions  of  trace  gases  from  biomass  burning  •  Chemical  processing  and  impacts  of  biomass  burning  emissions    •  Use  of  chemical  tracers  to  evaluate  mixing/entrainment  processes  in  MBL  •  Emissions  of  reactive  trace  gases  from  the  surface  ocean  

Role  during  the  field  campaign/Instrument  description/etc.:  

•  Help  coordinate  chemical  instrument  payload  and  operations  •  Assist  in  flight  planning  •  In-­‐field  evaluation  and  integration  of  chemistry  measurements  

Planned  activity  post  campaign  

• Data  analysis,  integration  with  others  in  science  team.      Focus  on  chemical  tracers  of  biomass  burning  and  marine  emissions.  

Estimated  Budget:    

• 3  year  budget  estimate  approximately  $100  -­‐  $125K;  to  include  nominal  salary  coverage,  travel  for  payload  integration/field  deployment,  science  team  meetings,  publication  cost.  

Airborne Aerosol Composition and Optical Properties in Southeast Atlantic during ONFIRE

Roya Bahreini, Assistant Professor of Atmospheric Science, UC- RiversideAnticipated Sponsor - NSF-ACD

During ONFIRE, the Co-PI proposes to measure size-dependent composition and optical properties of aerosol particles on-board the NSF C-130 aircraft to

•Understand primary and secondary aerosol formation processes in the region•Determine how fresh vs. aged aerosol particles affect CCN formation •Provide constraints on enhancement ratios (with respect to CO) of summertime non-refractory aerosol species originating from biomass burning, urban, and industrial sources •as a secondary objective, determine the direct radiative impacts of aerosol particles at λ=450 nm, especially in the poorly- characterized biomass burning plumes

The PI proposes to measure size-dependent, non-refractory composition of submicron aerosol particles (clear sky and interstitial) in the aerosol outflow off of the west coast of Africa, using a compact time-of-flight aerosol mass spectrometer (mAMS, Aerodyne Research, Inc.). Size dependent aerosol composition measurements will be used to not only determine the sources of non-refractory aerosol particles and characterize aerosol vertical distributions in the region [e.g.,Warneke et al., 2009], but also to investigate how transport and aging of aerosols change their chemical properties [e.g., Bahreini et al., 2012] and cloud activation potential. To achieve the latter, composition of in-cloud interstitial aerosols will be compared with those measured in air masses with similar transport history but under a clear-sky. Furthermore, enhanced mixing ratios of the non-refractory aerosol concentrations with respect to CO will be calculated to put constraints on emission factors of aerosol species in air masses with an influence from biomass burning, urban, and industrial emissions in the area. Measurements of volatile organic compounds (VOCs) aboard the aircraft will be used to identify aerosol sources.

If space permits on the C-130, we will further gain an understanding of aerosol radiative effects by measuring aerosol extinction and scattering at λ=450 nm (1 Hz) using a cavity attenuated phase-shift spectrometer , equipped with an integrating sphere (CAPS-SSA, Aerodyne Research, Inc.). Given aerosol extinction and scattering, aerosol absorption and single scattering albedo can readily be calculated. Clear-sky, non-refractory aerosol composition and optical properties will be used along with black carbon (BC) measurements and Mie-theory to assess the influence of different aerosol absorption sources (BC, brown carbon (BrC), and lensing on the BC cores) in fresh and aged biomass burning plumes.. Mass spectral characteristics of aerosols will be analyzed to explain evolution of BrC absorption, total extinction, and single scattering albedo of aerosols upon transport and aging of air masses [e.g., Lack et al., 2013]. In addition, since dust particles contribute significantly to optical extinction but are undetected by mAMS, ratios of total extinction to mass of non-refractory aerosol and BC (measured by SP2) will be investigated to identify the extent of the influence of refractory dust particles in the region. Bahreini, R., et al. (2012), Mass Spectral Analysis of Organic Aerosol Formed Downwind of the

Deepwater Horizon Oil Spill: Field Studies and Laboratory Confirmations, Environ. Sci. Technol., 46(15), 8025-8034, doi:10.1021/es301691k.

Lack, D. A., R. Bahreini, J. M. Langridge, G. B. Gilman, and A. M. Middlebrook (2013), Brown carbon absorption linked to organic mass tracers in biomass burning particles, Atmos. Chem. Phys., 13, 2415-2422, doi:doi:10.5194/acp-13-2415-2013.

Warneke, C., R. Bahreini, et al., 2009:, Biomass burning in Siberia and Kazakhstan as the main source for Arctic Haze over the Alaskan Arctic in April 2008, Geophys. Res. Lett, 36, L02813, doi: 02810.01029/02008GL036194.

Airborne Measurements of DMS and CO flux for Determination of the Entrainment Rate during ONFIRE

Byron Blomquist, Research Scientist, CU-CIRESAnticipated Sponsor - NSF-ACD

The PI proposes to make high-rate (10-25 Hz) measurements dimethyl sulfide (DMS) with an Atmospheric Pressure Ionization Mass Spectrometer (APIMS) and carbon monoxide (CO) with an Off-Axis Integrated Cavity Output Spectrometer (OA-ICOS). In the context of a properly designed entrainment flight plan, these measurements, together with C-130 motion-corrected wind, fast water vapor and fast ozone, will yield multiple, independent determinations of cloud-top entrainment rate.

Among this suite of entrainment tracers, DMS is perhaps the most useful. DMS is solely derived from surface ocean biogenic emissions and, under conditions of atmospheric subsidence, has a near-zero concentration in the overlying free troposphere. The concentration jump at the inversion is large and well defined. The lifetime (~2 days) is sufficiently short that advection from distant sources is negligible, and sufficiently long that entrainment, surface flux and mixing dynamics within the marine boundary layer (MBL) largely determine the vertical concentration gradient. The APIMS has high sensitivity for DMS (>100 cps/pptv, Blomquist 2010). These factors make DMS an ideal tracer for boundary layer entrainment and we have successfully employed it for this purpose in prior field campaigns (Stevens et al., 2003; Faloona et al., 2005; Conley et al. 2009).

The APIMS instrument proposed for this work has been used successfully for ship-based DMS flux measurements over the past 12 years, exhibiting sensitivity of ~150 cps/pptv in the most recent deployment. Funds will be requested to upgrade selected components and convert the instrument for aircraft deployment.

CO is a relatively long-lived trace gas and an important tracer of biomass burning plumes. The S. Hemisphere background CO concentration (~50 ppb) is about half the N. Hemisphere value. As such, CO is an important diagnostic parameter for ONFIRE. In the past, CO flux measurements were difficult due to instrumental limitations. Entrainment rate estimates with this scalar have not been previously reported. The CO concentration jump at the inversion (10-15 ppb) is less well defined compared to DMS, but is perhaps less variable than ozone.

We recently demonstrated eddy covariance CO flux measurements from a ship using the Los Gatos Research OA-ICOS analyzer (Blomquist et al., 2012). This instrument has the best signal-to-noise (S/N) performance among currently available commercial CO analyzers with a noise level of ~0.015 ppb2 and exhibits minimal motion sensitivity. Working with the manufacturer, additional improvements in S/N are possible in a CO-only configuration with specially selected optics. Integration of the fast-CO measurement in the ONFIRE C-130 instrument payload adds a potentially valuable additional tracer of MBL entrainment.

Conley, S.A., I.Faloona, G.H. Miller, B. Blomquist, D.Lenschow, A.Bandy, Closing the dimethyl sulfide budget in the tropical marine boundary layer during the Pacific Atmospheric Sulfur Experiment, Atmos. Chem. Phys., 9, 8745–8756, www.atmos-chem-phys.net/9/8745/2009/ , 2009.

Blomquist, B.W., C.W. Fairall, B.J. Huebert, and S.T. Wilson, Direct measurement of the oceanic carbon monoxide flux by eddy correlation, Atmos. Meas. Tech., 5, 3069–3075, www.atmos-meas-tech.net/5/3069/2012/ , 2012.

Lagrangian tracer modeling for mission planning and semi-direct effect estimation

Jerome Brioude, CIRES/U of Colorado, BoulderAnticipated sponsor: NSF

! J. Brioude will be responsible for the real time forecasts of biomass burning plumes during the ONFIRE experiment using the FLEXPART Lagrangian particle dispersion model with NCEP/GFS forecasts. This tool has been used successfully in previous intensive campaigns (ARCPAC, VOCALS, CALNEX, DC3, SENEX).  Those forecasts will help design the flight plans during ONFIRE. J. Brioude will also provide FLEXPART model output as a post analysis tool to help estimating semi-direct effects.

Cloud microphysical structure and its response to meteorology and aerosol during ONFIRE

Patrick Chuang, University of California Santa CruzAnticipated Sponsor: NSF

PI Chuang proposes to deploy a phase Doppler interferometer to measure stratocumulus drop size distributions in the range of 3 to 100 μm diameter. This characterizes both the cloud drop distribution (up to 30 μm) where condensation and evaporation are dominant, as well as the auto-conversion regime (30 to 100 μm) where collision-coalescence is dominant and produces the incipient drops for any drizzle that occurs. We will further blend our measurements with those at larger drop sizes from C-130 facility cloud microphysical probes to generate a single, consistent drop size distribution spanning the full range of drop sizes (up to 6 mm diameter). This product addresses a number of key scientific objectives of ONFIRE, including characterization of: (i) the cloudy boundary layer; (ii) cloud-top entrainment; and (iii) aerosol semi-direct and indirect effects. It is also relevant to the acquisition of data sets to improve boundary-layer cloud representation in models.

Our analysis will focus on the response of the cloud properties (cloud geometric thickness, cloud drop number concentration and effective radius, cloud liquid water path, and cloud radiative forcing) to changes in the larger-scale environment, i.e. changes in both meteorology and aerosol, during ONFIRE. We will specifically address:

(a) changes due to cloud-top entrainment fluxes of moisture, energy and (potentially) biomass burning aerosol

(b) changes due to cloud-top radiative heating and cooling (both shortwave and longwave) caused by variations in free-troposphere moisture and biomass burning aerosol, which in turn affects the production of turbulent kinetic energy throughout the stratocumulus-topped boundary layer.

The potential for co-variance of important meteorological parameters (such as the vertical temperature and moisture profile) with biomass burning aerosol in this region is very high since fire and meteorology over the continent are correlated. One of our primary goals will be to apportion changes in the cloud between the meteorological and aerosol changes. This will be achieved using LES simulations of this region in a manner very similar to a recently-published study by the Chuang research group (Petters et al., Atmos. Chem. Phys., v. 13, pp. 2507--2529, 2013; hereafter P13) wherein aerosol and meteorological parameters from an observationally-constrained base case are altered one at a time to evaluate the individual parameter sensitivities of relevant cloud properties. One implication of P13 is that these individual sensitivities are strongly dependent on the base case considered, and thus we are interested in studying a stratocumulus case with very different environmental conditions, namely the presence of the overlying biomass burning aerosol plume. We plan to further extend P13 by also examining changes in multiple parameters simultaneously, which was not previously considered. The degree to which the stratocumulus response to perturbations can be linearly added is not well-understood. Deviations from linear additivity describe the strength of internal interactions and feedbacks in the stratocumulus-topped boundary layer that buffer the cloud from changes (Stevens and Feingold, Nature, 2009). The strength of this buffering and its dependence on the boundary layer properties is another outstanding question that we would seek to address using these measurements.

Eddy Correlation Measurements of Multiple Scalar Fluxes Throughout the Marine Boundary Layer to Quantify Entrainment and Scalar Budgets

Ian Faloona, Associate Professor, University of California DavisAnticipated Sponsor - NSF-ACD

I propose to serve as flight scientist on the entrainment flights, and to work closely with the science team in the field in order to perform rapid data analyses to assess the instrumental success in measuring airborne eddy covariance fluxes and scalar budgets of DMS, CO, O3, enthalpy, and water vapor. These flux measurements are central to the investigation of entrainment rates and thus the mixing of the aerosol layer down into the cloud layer. My group has over a dozen years of experience in making these measurements by aircraft and using the fast scalar measurements to study both the turbulent (Faloona et al., 2005) and photochemical characteristics (Conley et al., 2009; Faloona et al., 2010) of the marine boundary layer.

The use of as many different scalars as possible in implementing the flux/jump method for measuring entrainment is critical to obtaining the greatest accuracy because of the many complications that arise during individual flights for some of the scalars. For example, often high variability in the free troposphere of O3 and (quite possibly for CO in biomass burning outflows) can make the determination of an average jump across the inversion very noisy. Additionally, carefully closing the budgets of the photochemically active scalars O3 and DMS in the marine boundary layer will provide important insights into the vital oxidation rates that drive the photochemical processing in the aerosol environment (Conley et al., 2011). We will work to critically analyze the high-rate airborne data to quantify the turbulent mixing and photochemical state of the study region.

References

Faloona, I., D. Lenschow, T. Campos, et al. Observations of Entrainment in Eastern Pacific Marine Stratocumulus Using Three Conserved Scalars. Journal of the Atmospheric Sciences, 62, 3268-3285, 2005.

Conley, Stephen A., I. Faloona, G.H. Miller, B. Blomquist, D. Lenschow, A. Bandy, Closing the Dimethyl Sulfide Budget in the Tropical Marine Boundary Layer during the Pacific Atmospheric Sulfur Experiment, Atmospheric Chemistry and Physics, 9, 8745-8756, 2009.

Faloona, I.C., S.A. Conley, B. Blomquist, A. Clarke, S. Howell, V. Kapustin, and A. Bandy, Sulfur dioxide in the tropical marine boundary layer: dry deposition and heterogeneous oxidation observed during the Pacific Atmospheric Sulfur Experiment, Journal of Atmospheric Chemistry, 63(1), 13-32, 2010.

Conley, S. A., Faloona, I. C., Lenschow, D. H., Campos, T., Heizer, C., Weinheimer, A., Cantrell, C. A., Mauldin, R. L., Hornbrook, R. S., Pollack, I., Bandy, A. A complete dynamical ozone budget measured in the tropical marine boundary layer during PASE. Journal of Atmospheric Chemistry, DOI 10.1007/s10874-011-9195-0, 2011.

Large Eddy Simulation of Smoke-Cloud-Interactions and Influence on Boundary Layer Structure

Graham Feingold, NOAA ESRLAnticipated Sponsor - NOAA

! G. Feingold will use LES to investigate process-level interactions between absorbing aerosol, boundary layer dynamics, cloud microphysics, and radiation. Model domains will be on the order of 25 km x 25 km with grid sizes on the order of 100 m. We will extend our current and past work that has studied these interactions in continental cumulus cloud fields over land (Feingold et al. 2005; Jiang and Feingold 2006; Lee et al. 2014). Simulations will directly address hypotheses H2 and H3 in the stratocumulus regime, the cumulus regime, and the transition between them (SPO 2.2.1). We will work closely with modelers working at larger scales to help elucidate physical processes, benefit from their simulation of larger scale features (2.2.2), and assist with parameterization (2.2.4).

The ONFIRE field campaign provides opportunity to deepen our knowledge of factors (biomass burning, lightning, transport) that are responsible for September-October-November South Tropical Atlantic ozone maximum through ground based in situ vertical profiles from St. Helena and Ascension Island. The ground-based measurements of tropospheric ozone profiles are proposed and will be compared directly to upstream C-130 trace-gas and aerosol measurements along coastal Central Africa. The ONFIRE aircraft measurements, which is deployed from Sao Tome (0.33° N, 6.73° E), provides sampling which is much further north of the 2016 CLARIFY/ORACLES field campaign, which will deploy from Walvis Bay, Namibia (22.95° S, 14.5° E); the northerly deployment of ONFIRE provides additional insights on cross-equatorial flow, the African Easterly Jet South (AEJ-S) and LNOX produced ozone from continental West Africa that is transported to the Southern Hemisphere. The proposed ONFIRE aircraft N-S transect from the Equator to 15° S will take measurements associated with biomass burning aerosols and ozone precursors that can be used for trajectory and chemical modeling evaluation; C-130 drop-sondes will provide important details about the AEJ-S and its connections to long-range transport of biomass burning aerosols, ozone precursors and ozone.

We anticipate weekly measurements beginning in early August 2017 from Ascension Island and St. Helena. The frequency of ozonesonde measurements will increase with the start of the ONFIRE campaign, with measurements being time-lagged 2-4 days behind aircraft measurements based on real-time WRF-CHEM forecast and HYSPLIT forward trajectory for Ascension and St. Helena. We expect to launch a total of 40-50 ozonesondes for the period of August and September 2017 at both locations (25 each). The ozonesonde measurements will be archived on the SHADOZ network for the general community. This work will support student research experiences (4 in total) with an effort to recruit underrepresented groups in the field campaign. Support for 1 postdoctoral fellow will be sought for the 2 years. The objectives of our measurements for ONFIRE are:

• Sample the lower, upper and middle troposphere during September and Octoberfor determining vertical profiles of ozone mixing ratios, thermodynamic anddynamic variables for comparison to upstream aircraft measurements; assist withradiosonde measurements;

• Examine vertical distributions of biomass burning aerosols and its relationship tothe vertical distribution of ozone mixing ratios in the lower to middle troposphere;

• Identify distinct layers where ozone mixing ratios increases occur in relationshipto aerosols concentrations and size distributions;

• Identify the sources (West Africa, Central Africa, South America) of middle andupper troposphere ozone enhancements associated with LNOX through trajectoryanalysis.

• Compare upstream O3 mixing ratios, water vapor mixing ratios from aircraft tothose in Ascension Island (and possibly St. Helena) for determining ozoneenhancement and dehydration of continental outflow.

• Work with the ONFIRE team to determine CO/O3 correlations along with NOXmixing ratios in the lower and middle troposphere for examining anthropogenicversus natural sources of ozone.

• Undertake daily HYSPLIT WRF-CHEM forecast with biomass burning emissionsand trace gas options for coherence of aircraft and ground-based ozonesondemeasurements.

Gregory JenkinsHoward University

Anticipated Sponsor - NSF-Chem

Analyses of Satellite Imager Data David Painemal (SSAI) and Patrick Minnis (NASA-Langley)

Anticipated Sponsor – NASA

Algorithms adapted from those used to analyze MODIS observations for the Clouds and Earth’s Radiant Energy System (CERES) will be used to analyze imager data from Meteosat SEVIRI and GERB, MODIS on Aqua and Terra, and VIIRS and AtMS on the NPP Suomi satellite. The cloud algorithms simultaneously retrieve cloud temperature (TT), optical thickness (COD), and effective radius (re) using the 11, 0.65, and 3.9 µm channels on all 3 types of imagers. At night, the 3.8, 11, and 12-µm channels are used to retrieve the same parameters for optically thin clouds and account for semitransparency of both low and high clouds in the estimation of TT. SEVIRI 3-km and GERB broadband radiation data are taken and analyzed every 15 min, while the MODIS 1-km and VIIRS 0.75-km are taken at ~1030 and 1330 LT each day along with CERES broadband radiation data. COD and re are used to compute liquid water path (LWP). AtMS microwave data provide an independent measurement of LWP. CALIPSO data will be used as a source of aerosol layer heights and concentration. Retrievals of cloud top TT and cloud fraction are further used to derive cloud top heights (HT) using the technique of Sun-Mack et al. (2014) and Painemal et al. (2013), which have shown excellent agreement with the actual cloud top height and accurately reproduces large-scale patterns and diurnal cycle features (e.g., Painemal et al., 2013). These retrievals have been recently utilized to document the diurnal cycle of cloud fraction and HT over the S. Atlantic and its connection with the inversion strength and stability during spring as well as to evaluate numerical model performance (Painemal et al., 2015). In addition, HT combined with meteorological reanalysis fields will provide regional estimates of entrainment rates by means of a mixed layer equation that relates temporal variation in HT to subsidence, HT advection, and entrainment rate (e.g., Wood and Bretherton, 2006). Satellite-derived estimates of entrainment rate will be essential to determine the flux of aerosols into the cloud top and for understanding the aerosol indirect effect. In addition Meteosat cloud microphysics will be valuable for investigating whether smoke aerosols modulate the cloud diurnal cycle. The MODIS and VIIRS retrievals provide additional valuable spectral information that can be related to the vertical variation of re and aerosol effects. The GERB and CERES data provide accurate large-scale estimates of TOA radiative forcing for both pristine and aerosol-affected clouds. Although significant biases in COD retrievals can be induced by absorbing aerosols that overlie the cloud deck, the bias is modest for retrievals of re derived from the 3.9-µm wavelength (e.g. Cattani et al. 2006). This enables the use of re for research applications without correcting for the aerosol absorption. The re and HT diurnal cycle differences for episodic offshore smoke transport will be studied in detail with the purpose of determining the roles of regional circulation, boundary layer height, and aerosol modulation in the controlling cloud microphysics variability.

Cattani, E., M.J. Costa, F. Torricella, V. Levizzani, A.M. Silva, 2006: Influence of aerosol particles

from biomass burning on cloud microphysical properties and radiative forcing, Atmospheric Research, 82, 1-2, 310.

Painemal, D., K-M Xu, A. Cheng, P. Minnis, and R. Palikonda, 2015: Mean Structure and Diurnal Cycle of Southeast Atlantic Boundary Layer Clouds: Insights from Satellite Observations and Multiscale Modeling Framework Simulations. J. Climate, 28, 324–341.

Sun-Mack, S., P. Minnis, et al., 2014: Regional apparent boundary layer lapse rates determined from CALIPSO and MODIS data for cloud height determination. J. Appl. Meteor. Climatol., 53, 990–1011.

Wood, R., and C. S. Bretherton, 2006: Boundary layer depth, entrainment, and decoupling in the cloud-capped subtropical and tropical marine boundary layer. J. Climate, 17, 3576–3588

Aerosol  Influences  on  Processes  that  Determine  the  SST  in  the  Southeastern  Atlantic  

 C,  Roberto  Mechoso  

Department  of  Atmospheric  Sciences,  UCLA  Anticipated  Sponsor  –  NOAA  

   C.  R.  Mechoso  will  investigate  the  influence  of  aerosols  on  the  components  of  the  heat  flux  budget  in  the  southeastern  Atlantic  Ocean.    The  better  understanding  of  these  fluxes  will  provide  guidance  on  improvements  required  by  coupled  atmosphere-­‐ocean  general  circulation  models  (CGCMs)  in  order  to  reduce  their  systematic  errors  in  the  region.  In  most  contemporary  CGCMs,  simulated  marine  clouds  coverage  tends  to  be  too  low  and  SSTs  too  high.    This  is  a  coupled  atmosphere-­‐ocean  problem,  in  which  errors  in  one  system  feedback  on  the  other.    Aerosol  should  influence  the  vertical  structure  of  the  atmosphere  and  the  heat  fluxes  at  the  ocean  surface.  We  have  been  analyzing  these  balances  in  several  versions  of  the  NCAR  ESM,  including  one  in  which  a  high-­‐resolution  regional  ocean  model  is  embedded  in  the  global  ocean  component.    The  sensitivity  of  the  atmosphere-­‐ocean  heat  budget  in  the  southeastern  Atlantic  to  the  aerosol  will  by  comparing  simulations  with  and  without  prescribed  aerosol  distributions  in  close  coordination  with  those  obtaining  in-­‐situ  data.  Models  to  be  used  are  the  NCAR  ESM  and  UCLA  CGCM,  the  latter  of  which  clearly  separates  boundary  layer  from  free  atmosphere.    The  research  will  directly  address  hypotheses  H2.    Mechoso  will  also  contribute  to  coordination  between  ONFIRE  and  PREFACE,  of  which  he  is  member  of  the  External  Scientific  Panel.  

National Center for Atmospheric Research NCAR Earth System Laboratory Climate & Global Dynamics Division P.O. Box 3000 Boulder, CO 80307-3000

Tel: 303-497-1000 Web: http://www.cgd.ucar.edu/

The National Center for Atmospheric Research is operated by the University Corporation for Atmospheric Research under sponsorship of the National Science Foundation.

An Equal Opportunity/Affirmative Action Employer

January 15, 2014 Dr. Paquita Zuidema RSMAS/MPO University of Miami 4600 Rickenbacker Causeway Miami, FL 33149 Dear Dr. Zuidema, This letter is to confirm my intent to collaborate with you on your proposal “Observations of Fire’s Impact on the Southeast Atlantic Region (ONFIRE) Study.” As a collaborator of this field project, I will perform a series of simulations with the Communty Atmosphere Model (CAM) with high-frequency output saved over the southeast Atlantic. Numerical experiments will be designed that focus on evaluating the cloud and boundary layer structure over the southeast Atlantic including the effects of aerosol. The simulations will be initialized from operational analyses from the ONFIRE campaign period (likely from ECMWF), providing a large-scale flow that is initially constrained to be realistic. Each simulation will be run for only a few days, during which the simulated atmosphere will diverge from the observationally-constrained analyses and evolve toward the model's preferred climatology. Comparison with the ONFIRE observations will help to evaluate the model's verisimilitude. Sensitivity experiments related to entrainment, precipitation, and other boundary layer processes will help to evaluate the role of these processes in the formation of the fast errors. Additional experiments will investigate the role of aerosol emissions originating from the continent to assess the sensitivity of cloud and boundary layer structure (such as the strength of the inversion and optical properties of the clouds) to aerosol perturbations. This work will not be funded through ONFIRE, but will be synergistic with previous funding from the Department of Energy. I look forward to collaborating with you on this effort. Sincerely,

Dr. Brian Medeiros NCAR Earth System Laboratory Climate & Global Dynamics Division Atmospheric Modeling & Predictability Section

Mixing  processes  and  cloud  microphysics  derived  from  stable  isotopes  during  ONFIRE  

David  Noone  (Oregon  State  University)    Anticipated  Sponsor  -­‐    NSF-­‐ATM  (~550k  anticipated)  

The  stable  isotope  ratios  of  cloud  condensate  and  water  vapor  provide  insight  into  both  air  mass  mixing  and  microphysical  processes.  Bailey  et  al.  (2013)  identified  transition  layers  at  the  top  of  stratiform  cloud  that  arise  from  the  interplay  between  evaporative  cooling  at  the  cloud  top,  entrainment  and  shallow  convective  detrainment.  The  isotopic  signature  of  evaporated  cloud  differs  from  that  of  the  cloud-­‐free  air  nearby  and  exchange  can  be  identified  via  a  mixing-­‐line  analysis.  This  approach  is  very  powerful  because  of  the  large  gradients  in  water  vapor  in  the  atmosphere  and  because  the  isotope  ratios  identify  the  processes  which  set  those  variations  over  a  wide  range  of  space  and  time  scales.  In  particular,  since  isotope  ratios  distinguish  free  tropospheric  air  masses  with  distinct  hydrological  histories,  the  relative  importance  of  these  air  masses  in  mixing  aerosol  into  the  marine  boundary  layer  and  its  cloud  layer  can  be  readily  detected.  Within  clouds,  the  fraction  of  total  water  that  falls  as  precipitation  imprints  a  distinct  isotopic  fingerprint  on  the  cloud  condensate;  and  this  fingerprint  has  been  measured  previously  on  the  NCAR  C130  by  coupling  an  isotopic  laser  absorption  spectrometer  to  a  CVI  inlet  (e.g.,  Noone  et  al.,  2011,  2013).  Using  equivalent  fingerprints  in  vapor,  Bailey  et  al.  (2013)  identified  correlations  between  aerosol  distributions  (50-­‐1000  nm)  and  precipitation  efficiency.  We  have  observed  similar  isotopic  relationships  at  cloud  boundaries,  where  evaporation  of  cloud  liquid  is  correlated  with  downward  velocity  in  the  region  of  the  latent  cooling.  These  markers  for  cloud  dynamics  and  microphysics  will  be  used  aerosol  measurements  to  test  the  dependence  of  cloud  evaporation  and  mixing  (at  cloud  boundaries  and  associated  with  bulk  entrainment/detrainment  between  distinct  atmospheric  layers)  on  different  aerosol  populations  observed  during  the  ONFIRE  flights.    

Because  isotope  ratios  are  strong  tracers  of  air  mass  transport,  they  are  ideal  for  comparing  field  observations  with  dynamical  process  models.  In  collaboration  with  Amy  Solomon,  a  series  of  cloud-­‐resolving  simulations  will  be  performed  in  a  model  that  has  been  fitted  with  water  “tags”  and  stable  isotope  tracers.  Changes  in  water  transport  pathways  in  and  near  clouds  in  cases  with  differing  smoke  and  other  aerosols  will  be  evaluated.  The  stable  isotopic  simulations  will  provide  a  critical  link  between  specific  processes  identified  from  the  field  measurements  and  transport  processes  that  can  be  otherwise  overlooked  to  be  exposed.  The  analysis  also  provides  a  basis  against  which  to  test  new  boundary  layer  parameterization  schemes.    

Bailey,  A.  D.  Toohey  and  D.  Noone,  2013:  Characterizing  moisture  exchange  between  the  Hawaiian  convective  boundary  layer  and  free  troposphere  using  stable  isotopes  in  water.  Journal  of  Geophysical  Research-­‐  Atmospheres,  118,  8208.8221,  doi:10.1002/jgrd.50639.  

Noone,  D.  ,  A  practical  constraint  on  entrainment  and  condensate  evaporation  and  from  aircraft  and  satellite  observations  of  isotope  ratios  of  water.23rdth  Goldschmidt  Conference  of  the  European  Association  of  Geochemistry,  Florance,  Italy,  25-­‐30  August.  

Noone,  D.  C.,  A.  Bailey,  D.  W.  Toohey,  C.  H.  Twohy,  A.  Heymsfield,  C.  Rella,  A.  D.  Van  Pelt,  2011:  Aircraft  profile  measurements  of  18O/16O  and  D/H  isotope  ratios  of  cloud  condensate  and  water  vapor  constrain  precipitation  efficiency  and  entrainment  rates  in  tropical  clouds.  EOS  Trans.  AGU,  90(52),  Fall  Meet.  Suppl,  Abstract  A24B-­‐07  

Forcing mechanisms and variability of the low-level and mid-level winds that influence the Namibia-Angola stratocumulus

David A. Rahn

University of Kansas Anticipated Sponsor: NSF-AGS

Overview Examining the microphysics of the Namibia-Angola stratocumulus including any aerosol-cloud interaction from biomass burning requires an understanding of the regional dynamics. Issues driven by the dynamics, such as aerosol transport and strength of the subsidence inversion, play a key role in any effort to separate the impacts of meteorology from microphysical processes. There are a sparse number of studies that examine the Namibia-Angola marine boundary layer cloud system, and there is very limited work that directly examines the dynamics on a synoptic scale or diurnally. This is partly due to the lack of systematic, long-term monitoring of the region. Scarcity of information about the region motivates several key questions. While the day-to-day variability is not as large as it is farther south, the region is still impacted by transient synoptic features. The average frequency and duration of particularly strong offshore flow aloft (~600 hPa) will be a major factor that influences the offshore transport of aerosol. The southerly low-level jet along the Benguela Coast and the easterly wind aloft are likely linked, but do these evolve simultaneously or is there a lead-lag relationship? A clear conceptual model of the system must be created to provide a framework for understanding other processes. Measurements collected during the field project will be valuable in identifying many aspects of the system. Regional modeling must also be conducted to provide a broader context. The observations will serve as a hard test for the ability of any regional model to correctly simulate the salient features. Other data, such as from satellite scatterometers, will be used to understand the near-surface wind and provide additional observational support. In other regions, coastal low-level jets can be interrupted by transient features. Examples include coastally trapped wind reversals along the coast of California, coastal lows along the coast of Chile, and strong Paracas wind events along the coast of Peru. Each of these have their own dynamics influenced primarily by the topography and can significantly alter the local conditions. It is likely that similar interruptions may occur to the Benguela jet, which must be documented. Objectives

• Classify the variability and characteristic synoptic patterns using different methods including self-organizing maps.

• Quantify synoptic and diurnal changes in the momentum budget near the surface and aloft to determine and understand the forcing mechanisms that drive the flow.

• Understand the interactions between the low-level jet with the offshore flow aloft through representative case studies and provide a conceptual model.

• Identify and explain any situations that interrupt the normal conditions.

Gregory RobertsScripps Institution of Oceanography/Centre National de Recherché Scientifique

Anticipated funding source: NSF Chem

One of the main ONFIRE hypotheses is that South Atlantic boundary layer CCN can be dominated by BB aerosols as the boundary layer deepens, and entrained BB aerosols can significantly alter cloud microphysics, precipitation susceptibility and cloud mesoscale organization.  To test this hypothesis, in situ measurements of aerosol physicochemical properties, their vertical structure and their CCN activity are needed.  In a previous study, Roberts et al. (JGR, 2003) used a one-dimensional (1-D) cloud parcel model to assess the impact of BB aerosol on cloud properties in the Amazon Basin.  During the dry season in the Amazon, cloud droplet concentrations may increase by up to seven times, which leads to a model predicted decrease in cloud effective radius by a factor of 2, which implies a maximum indirect radiative forcing due to aerosol as high as ca. 27 W m^2. Yet, light-absorbing substances in BB aerosol darken the Amazonian clouds and reduce the net radiative forcing -- a comparison of the Advanced Very High Resolution Radiometer (AVHRR) analysis and the 1-D model suggests that absorption of sunlight due to BB aerosol may compensate for about half of the maximum aerosol effect.  We propose to extend such an analysis to the aerosol-cloud interactions over the Southern Atlantic Ocean during ONFIRE.   This proposed project addresses the following science objectives: 1.  Identify sources and sinks of BB aerosol and CCN properties of the South Atlantic boundary layer and free troposphere.2.  Characterize vertical structure of the atmosphere to assess entrainment of the BB aerosol / CCN in the marine boundary layer.3.  Use aerosol hygroscopicity to study the ageing of the BB aerosol (and effects of clouds on the processing of BB aerosol).4.  Quantify aerosol indirected effect due to BB-related CCN.  We propose to deploy a miniaturized CCN counter on the NCAR’s C130 to resolve the horizontal and vertical structure of the lower free troposphere and with particular focus on the entrainment of CCN from the free troposphere into the boundary layer, where the BB aerosol may serves as seeds for cloud formation.  Roberts has miniaturized a streamwise CCN instrument [Roberts and Nenes, AS&T, 2005] to a total weight of 1.5 kg and a foot print of 20x10 cm, which can easily be accommodated in the C130 – leaving room for additional critical measurements.  A total of three years will be requested to support the PI and a post-doctoral scholar.

ONFIRE Spectral Irradiance Measurements and Data Analysis Sebastian Schmidt, U of Colorado, Laboratory for Atmospheric and Space Physics

Anticipated Sponsor - NSF

! Sebastian Schmidt (University of Colorado, Laboratory for Atmospheric and Space Physics) will process the shortwave spectral irradiance data from the HIAPER Atmospheric Radiation Package (HARP, PI Samuel Hall, NCAR) from the NCAR C-130 flights after the experiment in 2016. The HARP includes a Solar Spectral Flux Radiometer (SSFR; Pilewski et al., 2003), which is a moderate resolution irradiance spectrometer covering 360-2150 nm in wavelength, and Kipp and Zonen broadband radiometers.This involves applying spectral and radiometric calibration to the raw data, and correcting for various effects such as the changing aircraft attitude angles. The quality-checked data will then be archived and used for subsequent science analysis.

The data from the ONFIRE study region lends itself for similar types of analyses performed previously in Mexico City (Schmidt et al., 2010) for characterizing the radiative effects (absorption, forcing, optical properties) and Houston, TX (Schmidt et al., 2009) for characterizing the combined radiative effects of clouds and aerosols. Specifically, we will use downwelling spectral irradiance measurements below aerosol-embedded broken cloud layers to separate the effects from aerosols and clouds (Schmidt et al., 2009), and upwelling spectral irradiance measurements above clouds with overlying aerosol layers (Coddington et al., 2010) to study the relationship between passive remote sensing of cloud-aerosol layers and their radiative effects. Some of these activities will involve three-dimensional radiative transfer calculations. We will thereby make use not only of the radiation data, but also use in-situ aerosol and cloud measurements on the C-130. We will also provide cloud retrievals based on reflected or transmitted spectral irradiance (Kindel et al., 2010; Coddington et al., 2010).

Sebastian Schmidt is also the investigator responsible for the SSFR on the ORACLES deployment, and as such will take the lead on cross-calibration exercises, and developing synergistic analyses from both deployments, including select coordinated flight plans.

References

Coddington, O. M., P. Pilewskie, J. Redemann, S. Platnick, P. B. Russell, K. S. Schmidt, W. J. Gore, J. Livingston, G. Wind, and T. Vukicevic, 2010: Examining the impact of overlying aerosols on the retrieval of cloud optical properties from passive remote sensing, J. Geophys. Res., 115, D10211, doi:10.1029/2009JD012829.

Kindel, B. C., K. S. Schmidt, P. Pilewskie, B. A. Baum, P. Yang, and S. Platnick, 2010: Observations and modeling of ice cloud shortwave spectral albedo during the Tropical Composition, Cloud and Climate Coupling Experiment (TC4), J. Geophys. Res., 115, D00J18, doi:10.1029/2009JD013127.

Pilewskie, P., J. Pommier, R. Bergstrom, W. Gore, S. Howard, M. Rabbette, B. Schmid, P. V. Hobbs, and S. C. Tsay (2003), Solar spectral radiative forcing during the Southern African Regional Science Initiative, J. Geo- phys. Res., 108(D13), 8486, doi:10.1029/2002JD002411.

Schmidt, K. S., G. Feingold, P. Pilewskie, H. Jiang, O. Coddington, and M. Wendisch, 2009: Irradiance in polluted cumulus fields: Measured and modeled cloud-aerosol effects, Geophys. Res. Lett., 36, L07804, doi:10.1029/2008GL036848.

Schmidt, K. S., Pilewskie, P., Bergstrom, R., Coddington, O., Redemann, J., Livingston, J., Russell, P., Bierwirth, E., Wendisch, M., Gore, W., Dubey, M. K., and Mazzoleni, C., 2010a: A new method for deriving aerosol solar radiative forcing and its first application within MILAGRO/INTEX-B, Atmos. Chem. Phys., 10, 7829-7843, doi:10.5194/acp-10-7829-2010.

Measurement  of  Black  Carbon  and  Aerosol  Absorption  during  ONFIRE  Joshua  Schwarz  and  Dan  Murphy,  NOAA/CIRES  

  Anticipated  Sponsor:  NOAA,  with  in-­kind  support  from  NSF  Shane  Murphy,  University  of  Wyoming  

Anticipated  Sponsor:  NSF    

A  NOAA  Single-­‐Particle  Soot  Photometer  (SP2)  and  Photo-­‐Acoustic/Cavity  Ringdown  Spectroscopes  (PAS-­‐CRD)  will  be  integrated  onto  the  NSF-­‐NCAR  C-­‐130  research  aircraft  for  the  ONFIRE  mission.  This  instrumentation  is  critical  to  achieving  ONFIRE  goals  of  exploring  aerosol  emissions  from  southern  Africa,  their  evolving  climate-­‐relevant  optical  properties,  and  their  interactions  with  the  large  stratocumulous  deck  off  the  coast.    The  NOAA  SP2  provides  unambiguous  black  carbon  (BC)  aerosol  accumulation  mode  mass  mixing  ratio,  size  distribution,  and  microphysical  state  (i.e.  degree  of  internal  mixing  with  non-­‐BC  materials).  The  PAS-­‐CRD  provides  total  aerosol  absorption  and  extinction  at  three  wavelengths,  providing  single-­‐scatter  albedo  and  a  fundamental  link  to  in-­‐situ  heating.  The  PAS-­‐CRD  is  the  only  instrument  available  that  measures  the  actual  light  absorption  rather  than  a  surrogate  such  as  filter  darkening.  The  PAS-­‐CRD  also  has  thermal  desorption  channels  to  study  enhanced  light  absorption  by  BC  internal  mixtures  and/or  brown  carbon.  Finally,  the  PAS-­‐CRD  measures  the  change  in  extinction  with  relative  humidity.    The  PAS-­‐CRD/SP2  pairing  is  a  powerful  tool  for  attributing  and  tracking  aerosol  absorption.    In  conjunction  with  gas  phase  measurements  of  CO  and  CO2,  and  aerosol  composition  also  located  on  the  NSF/NCAR  C130,  these  instruments  will  provide  emission  factors  of  primary  and  secondary  aerosol  species  from  the  African  biomass  burning.  Measurements  of  BC  and  light  absorption  are  required  to  attribute  changes  in  the  thermal  structure  of  the  atmosphere  to  aerosol  absorption.  These  data,  in  conjunction  with  cloud-­‐residual  and  interstitial  probes,  also  constrain  the  direct  and  semi-­‐direct  impacts  of  biomass  burning  aerosol  on  clouds.    The  SP2  and  the  PAS-­‐CRD  have  both  flown  previously  on  the  NOAA  P-­‐3  and  the  NASA  DC-­‐8.  Integration  onto  the  C-­‐130  will  require  effort  but  should  be  straightforward  for  these  proven  flight  instruments.  The  African  biomass  burning  plumes  should  provide  strong  signal  levels  for  both  instruments.    Specific  goals  for  this  instrument  suite  in  ONFIRE  are  to:  

1) Determine  emission  factors  for  BC  with  respect  to  CO  and  CO2  for  biomass  burning  in  southern  Africa.  

2) Generate  a  climatology  of  biomass  burning  aerosol  single  scatter  albedo  as  a  function  of  aging  since  emission  and  transport  over  the  ocean    

3) Quantify  the  impact  of  African  biomass  burning  emissions  on  the  vertical  structure  of  the  atmosphere  in  the  region  of  the  stratocumulus  decks.  

4) Identify  the  proportion  of  biomass  burning  BC  entrained  as  CCN  in  the  stratocumulus  decks.    5) Determine  the  export  efficiency  of  African  BB  emissions.    6) Determine  the  influence  of  internal  mixtures  on  BC  absorption  and  the  fraction  of  absorption  

due  to  brown  carbon  in  the  African  BB  emissions.    

Nested Large Eddy Simulations of the Impact of Smoke-Cloud Interactions on the Maintenance of Stratocumulus-topped Boundary Layers

Amy Solomon, University of Colorado and NOAA ERSL

Anticipated Sponsor – NOAA/NSF

Amy Solomon will use nested large eddy simulations (LES) to investigate the sensitivity of low cloud properties to aerosols emanating from Africa over the south Atlantic. Simulations will address hypotheses H2-3 and will be coordinated with idealized LES simulations performed by G. Feingold. The nested simulations will be used to study the influences of both meteorology and aerosols on the evolution of low cloud systems. The specific model set up is described in depth by Solomon et al. (2009, 2011), and includes a cascade of nested model domains from an outer 25-km resolution mesoscale domain down to an inner domain with 50-m horizontal resolution and 10-m vertical resolution to study detailed cloud processes. Forcing at lateral and surface boundaries will be derived from the ERA-Interim dataset. References: Solomon, A., M.D. Shupe, P.O.G. Persson, and H. Morrison, 2011: Moisture and dynamical interactions maintaining decoupled Arctic mixed-phase stratocumulus in the presence of a humidity inversion. ACP, 11, 10127-10148, doi:10.5194/acp-11-10127-2011. Solomon, A., H. Morrison, P.O.G. Persson, M.D. Shupe, and J.-W. Bao, 2009: Investigation of microphysical parameterizations of snow and ice in Arctic clouds during M-PACE through model-observation comparisons. Monthly Weather Review, 137, 3110-3128, doi:10.1175/2009MWR2688.1.

Analysis of in-situ and satellite observations for evaluating the semi-direct effect of African smoke on Southeast Atlantic clouds. Eric M. Wilcox Division of Atmospheric Sciences Desert Research Institute Anticipated Funding Sources – NASA, NSF The study documented in Wilcox (2010)1 presents evidence that stratocumulus clouds exhibit greater condensed liquid water when biomass burning aerosols reside in the layer above the cloud. The observed increase in vertically integrated cloud liquid water is similar in magnitude to the amount predicted in the large-eddy simulation experiment presented in Johnson et al. (2004)2 where smoke above clouds was found to inhibit entrainment mixing that would otherwise act to dry the boundary layer and reduce cloud cover. Nevertheless, the Wilcox (2010) empirical study could not eliminate the possibility that the observed relationship was a result of changes in boundary layer dynamics and thermodynamics coincident with smoke transport. Furthermore, this study did not explore the detailed vertical distribution of smoke and clouds to determine the observed vertical profiles most suitable to yielding a semi-direct cloud response. Progress on these unresolved issues is required to further verify that the observed relationship is truly an aerosol effect, and to advance remote sensing techniques to assess the magnitude of semi-direct effects globally. This will be achieved through a combination of analysis of in-situ observations from ONFIRE, ORACLES, and CLARIFY together with remote sensing observations from Meteosat and NASA datasets. Meteorological co-variation of smoke and clouds will be evaluated on a variety of time scales from the daily history of cloudy air masses revealed in geostationary imagery to the intraseasonal variations in smoke and cloud revealed in the combined sampling of the three field campaigns and the multi-year satellite datasets. The work will also evaluate the ability of CALIOP space-borne lidar to adequately resolve the vertical distribution of smoke required for semi-direct radiative effects. Proposals will be submitted to NASA and NSF seeking to exploit ONFIRE and ORACLES data to further test the hypothesis that semi-direct effects are responsible for the Wilcox (2010) results and advance techniques to identify similar cloud responses to aerosols in other regions.

1 Wilcox, E. M., Stratocumulus cloud thickening beneath layers of absorbing smoke aerosol. Atmos.

Chem. Phys., 10, 11769-11777, doi:10.5194/acp-10-11769-2010, 2010. 2 Johnson, B. T., K. P. Shine, P. M. Forster: The semi-direct aerosol effect: Impact of absorbing aerosols

on marine stratocumulus, Q. J. R. Meteorol. Soc., 130, 1407-1422, 2004.

Aerosol Physics, Wyoming Cloud Radar (WCR), Lidar (WCL), and Raman Lidar (MARLi) observations of aerosol, cloud and precipitation structures

David Leon, Jefferson R. Snider and Zhien Wang, University of WyomingAnticipated Sponsor - NSF

Collective U of Wyoming Total Budget – $600K Estimated

Given the importance of the thermodynamic structure in and above the boundary layer in driving the transition from stratocumulus to trade wind cumulus we propose to deploy the Wyoming Cloud Radar along with a pair of lidars (one upward- one downward-looking) on the C130. Basic instrument specifications are given in Table 1. These instruments will provide high-resolution profiles of key quantities as enumerated in Table 1.

Table 1. Proposed remote sensors for ONFIRE.Instrument Description Con/iguration Sampling

(time/vertical)Measurements

WCR 95  GHz  cloud  Radar

2  downward-­‐  1  upward-­‐looking  beam

20  Hz15m    

Re/lectivityDoppler  velocity

WCL 355  nm  elastic  backscatter  lidar

Upward-­‐looking 5  Hz3.75  m

Attenuated  Backscatter,  Depolarization  ratio

MARLi Raman  +  elastic  scatter  lidar

Downward-­‐looking

5-­‐30  Hz1.5  –  3  m

TemperatureHumidityAerosol/Cloud  Backscatter  &  Extinction

The Wyoming Cloud Radar (WCR) will be deployed in the 3-beam configuration used in VOCALS, PLOWS, and ICE-T. As in VOCALS the WCR will be used to determine cloud fraction, cloud-top height, detect and quantify drizzle. Upgrades to the WCR since 2008 have improved its sensitivity by > 10 dB. These improvements will enable radar detection of cloud and cloud boundaries even for thin, precipitation-free clouds and will be particularly important for flight legs at altitude when the C130 is sampling aerosol layers. As in VOCALS, the WCR will be used to document the occurrence and strength of drizzle and to estimate the fraction that evaporates before reaching the surface.

The Wyoming Cloud Lidar (WCL) will be used for upward-looking measurements. The WCL has a vertical/temporal resolution of 3.75m/5 Hz and will be used to provide measurements of backscatter and depolarization ratio, with the latter assessed for its ability to identify dust.

The Multi Function Airborne Raman lidar (MARLi) will be deployed on the C130 looking downward from the aircraft. This lidar, currently under development, will be initially deployed onboard the UW King Air for PECAN in 2015. MARLi will provide profiles of temperature and humidity as well as high-resolution (< 1m) observations of aerosol layers including improved measurements of aerosol backscatter and extinction and cloud-top height/structure. Given the importance of stability and conditional instability to the Sc-Trade Cu transition the ability of the TQ Raman lidar to determine profiles of temperature and humidity will be key to understanding the the St – trade Cu transition. ! We also propose to make measurements of the dried aerosol size distribution on the NCAR C-130 during ONFIRE. Measurements will be acquired over a range of particle diameter

(D), extending from approximately 3 nm to approximately 10000 nm. The proposed measurement systems are capable of resolving the concentrations of nucleation mode, Aitken mode, accumulation mode and coarse mode particles on time scales as short as one second. The data set will be acquired using two condensation particle counters, operated with their minimum detection diameter set at 3 and 15 nm, and with three optical particle counters operated with minimum detectable diameters at 55, 120 and 400 nm. These instruments are, respectively, the TSI-3025, TSI-3760, DMT-UHSAS, DMT-PCASP and DMT-FSSP300. Two of these will be supplied by University of Wyoming (TSI-3025 and DMT-UHSAS); the TSI-3760, DMT-PCASP and DMT-FSSP300 are NCAR-owned instruments and are available for deployment on the NCAR C-130. Our prior involvement in airborne investigations involving the NCAR C-130 (DYCOMS-II, VOCALS and ICE-T) has demonstrated the need for laboratory calibration of particle sizing thresholds and aerosol flow rates (Cai et al., 2013). We plan to conduct these calibrations in the Keck Aerosol Laboratory at the University of Wyoming. Our DMT-UHSAS is the lab-bench version (Cai et al., 2008), and will therefore be operated inside the cabin of the C-130, with the CPCs and mobility sizing systems. The PCASP and the FSSP300 are operated externally.

Observations from the WCR, WCL and MARLi and aerosol in situ will be used in a number of analyses: CDNC Closure studies: Lidar-retrieved cloud droplet concentrations will be analyzed with in-cloud droplet and above- and below-cloud aerosol/CCN measurements in studies of activation, entrainment/mixing and precipitation scavenging. Vertically-stacked flight legs are proposed for these investigations . Assessment of the BL mixing state: The WCL and MARLi will be important in helping to assess the BL mixing state. This will be done both directly, by observing increases in backscatter with decreasing altitude within the BL (MARLi and WCL) and increases in humidity/ decreases in temperature (MARLi), and indirectly by comparing the in situ derived LCL with cloud-base from low-level legs (WCL). This assessment will be particularly valuable in understanding the Sc – trade Cu transition as well as the more complex structure expected in the trade Cu region. Aerosol forcing in smoke layers: for flight legs above and in smoke layers, extinction and temperature profiles provided by MARLi will be used to understand the forcing exerted by aerosol layers on the thermal structure of the lower troposphere and in turn understand how the modified thermal structure and reduced shortwave radiation impinging on the top of the BL impact its evolution. Entrainment: MARLi, in conjunction with the WCR, will be used to investigate entrainment. Key observations here include profiles of temperature and humidity just above cloud top. In cases where aerosol layers intersect the cloud-top the downward-looking lidar will allow us to visualize entrainment into the Sc layer (e.g., Fig. 5 in main text). Finally, vertical-plane velocity fields from the WCR will be used to investigate the interaction between mesoscale circulations and entrainment. Similarly, in the trade cumulus region, MARLi will allow us to document the injection of humidity (and humidified aerosol) into the buffer layer by individual Cu. Cai, Y., J.R.Snider and P. Wechsler, Calibration of the Passive Cavity Aerosol Spectrometer Probe for

airborne determination of the size distribution, Atmos. Meas. Tech. Discuss., 6, 4123-4152, doi:10.5194/amtd-6-4123-2013, 2013

Cai, Y., D.C.Montague, W.Mooiweer-Bryan and T.Deshler, Performance characteristics of the ultra high sensitivity aerosol spectrometer for particles between 55 and 800 nm: Laboratory and field studies, Aerosol Sci., 39, 759-769, 2008