Tue 3/15/2016Briefly discuss last question on exam

• Project hypothesis presentations• Please complete evaluation forms (I’ll discuss shortly)• Resolution terminology (if time)

Reminders/announcements:• Take-home exam due Thur 3/17

• Any questions? Are things going well so far?• Paper presentation grading rubric posted on www page

Journal Paper Rubric

Hypothesis PresentationsEvaluation criteria:1.) Scientific merit: Are the scientific arguments well-

reasoned, clearly explained, and sensible from the standpoint of physical processes and previous research?

2.) Proposed method: Is it sound and well defended? Will the investigator actually be able to do what they propose (is the project “tractable”) in the time available?

3.) Value of work: To what extent will the proposed research benefit society, and potentially lead to larger implications and impacts, if successfully completed?

4.) Q&A: How well did PI respond to any audience questions/concerns?

Evaluations

Diabatic Rossby Waves as a Model for Convectively-

Coupled African

Easterly Waves

James RussellMEA716

African Easterly Waves (AEWs) and Diabatic Rossby Waves (DRWs)

DRWs1. Mid-latitude vortices/waves driven by

convective growth/propagation mechanism2. Convection ahead of PV maxima generates

low-level PV 3. New PV ultimately propagates and grows

wave

Fig: 2PVU iso-surface and 850hPa winds associated with a DRW (Winterstorm Lothar) approaching Europe.

Hypothesis:The DRW mechanism advects the AEW through convective generation of PV ahead of the AEW trough

Original AEW PV Anomalies

AEWs as DRWsConvection and diabatic heating generated ahead of AEW trough

Wave advected westward by convective generation of PV

New Convectively Generated PV

Case Study: AEW that led to Hurricane Earl19 - 26 Aug 2010

WRF Specs:Shin-Hong PBLTiedtke CumulusWSM-6 MicrophysicsNoah LSMRRTM and Dudhia Radiation

36km

12km4km

Method/Simulation

Sensitivity Study: Decrease moisture in IC’s and BC’s.Analysis: Examine PV budget.Expectation: Diabatic PV tendency weaker in sensitivity test.

TroughRidge

Wave moves westward with

time

Observed: ERA-Interim 650hPa Meridional Winds (m/s, color-shaded) & TRMM 3B42 Rainrate (mm/hr, contoured) averaged between 5-20N

Simulated: WRF 650hPa Meridional Winds (m/s color-shaded) & WRF Total Rainrate (mm/hr, contoured) averaged between 5-20N

RecapH

ypot

hesi

s The DRW mechanism has some role to play in the growth and propagation of AEWs.

Met

hod WRF control

simulation to resolve convection.Sensitivity study reducing moisture. Ex

pect

atio

n Diabatic PV tendency lower/ insignificant in sensitivity study when compared to control.

Questions?

OROGRAPHIC INFLUENCE ON AFRICAN EASTERLY WAVE 

EVOLUTIONDYLAN WHITE

03/15/2016

PROJECT PROPOSAL

AFRICAN EASTERLY WAVES (AEWS) Westward propagating synoptic scale disturbances

Precursor to many Atlantic hurricanes

Heavily modulates West African weather

Unsolved problem in atmospheric sciences

AEW EVOLUTION Barotropic‐baroclinic instabilities

Mesoscale convective triggers (latent heating)

Upstream Energy Dispersion

Orographic Forcing

OROGRAPHIC FORCING  Lin et al., 2005

23/34 (’90‐’01) tropical cyclones began as MCCs near the Ethiopian Highlands (EH)

Concluded that pre‐Hurricane Alberto AEW linked with orographic forcing

Convection generated over EH and disturbance forms in the lee of EH

HYPOTHESIS African easterly waves can exist independent of orography African Easterly Jet exists due to the surface meridional temperature gradient, not orography

Hydrodynamic instability has been shown to be a major contributor to AEW (citations)

EXPERIMENTAL DESIGNHypothesis: African easterly waves can exist independent of orography

Simulations CONTROL: Default simulation with 

original, observed orography

FLAT: Experimental simulation with completely flattened orography, all else same as CONTROL

Physics options (for both simulations) Kain‐Fritsch CP, WRF single moment 

6‐class MP, and YSU PBL schemes 

EXPERIMENTAL DESIGNHypothesis: African easterly waves can exist independent of orography

Analysis Longitude‐Time (Hovmoller) diagrams to analyze wave structure

Eddy kinetic energy (EKE) maps

EKE budget analysis

African Easterly Jet (AEJ) profile

PREDICTIONSHypothesis: African easterly waves can exist independent of orography

In the FLAT simulation, we will see less AEW activity in regions adjacent to and westward of mountainous regions, such as in Algeria (5 ◦E, 25 ◦N)

Everywhere else, in the FLAT simulation, other mechanisms with continue to produce AEW similarly to the CONTROL, but with minor differences

PRELIMINARY RESULTSHypothesis: African easterly waves can exist independent of orography

Wave Comparison

V windsFilteredV winds

PRELIMINARY RESULTSHypothesis: African easterly waves can exist independent of orography

Wave Comparison

V windsFilteredV winds

PRELIMINARY RESULTSHypothesis: African easterly waves can exist independent of orography

Wave Comparison

FilteredV winds

FilteredV winds

PRELIMINARY RESULTSHypothesis: African easterly waves can exist independent of orography

Mean AEJ profile (lines) and mean EKE (shaded)

CONTROL

FLAT

FURTHER EXPERIMENTATIONHypothesis: African easterly waves can exist independent of orography

Is 50 km grid spacing too coarse? AEWs are synoptic scale disturbances (L ≈ 1000 km) but could significant orographic effects that are perhaps unresolved by 50 km grid spacing affect AEW development?

Experiment Reduce grid spacing from 50 km to 36 km  Add 12 km nested grids to current domain  Examine smaller window of time to reduce computational expense

FURTHER EXPERIMENTATIONHypothesis: African easterly waves can exist independent of orography

Various orography removal Perhaps only some regions 

contribute AEW development, or perhaps there is some dependency on orographic height

Experiments Reduce heights in various 

locations, such as the Ethiopian highlands

Reduce heights and slopes by 50% and increase by 150% and examine AEW development

FURTHER EXPERIMENTATIONHypothesis: African easterly waves can exist independent of orography

Eddy kinetic energy (EKE) budget How does orography effect barotropic, baroclinic, and upstream dispersion EKE tendencies?

Experiment Examine different EKE tendency contributions in the different proposed experiments

The fields needed for this are already in the model output, so this is just a call for further analysis, not further simulations

QUESTIONS? ReferencesLin, Y.‐L., K. E. Robertson, and C. M. Hill, 2005: Origin and Propagation of a Disturbance Associated with an African Easterly Wave as a Precursor of Hurricane Alberto (2000). Mon. Wea. Rev., 133, 3276‐3298.

Lindsay R. BlankMarch 15, 2016

Motivation: Low instability convection poses a high risk to public safety!

Scientific Question: Are low instability convective environments sensitive to microphysics parameterization scheme choices?

Hypothesis: There is a microphysics parameterization scheme that is most favorable for simulating low instability convective environments.WSM6 = 31.8 mm  Lin = 35.8 mm

mm

Predictive skill will improve by determining the most favorable microphysics scheme.

Better predictability means a reduction of public risk!

Real‐data case: February 18, 2009 Run a WRF ensemble of different microphysics parameterization schemes

Compare results to observations: Quantitative Precipitation Estimation Spatial coverage of precipitation Equitable Threat Score

Sensitivity of turbulent fluxes and precipitation pattern to terrain data 

resolution in WRFMasih EghdamiMarch 15, 2016

Introduction

• Nastrom‐Gage (1985)

• Stronger precipitation has larger sensitivity and uncertainty. Smith et. al (2004)• Orographic clouds produce localized extreme values of rainfall that are associated 

with natural hazards such as landslides, debris flows and flash floods. Nogueira et. al (2014)

• Deficiencies in the global angular momentum budgets. Kain et. al (2008)

Hypothesis

• If the terrain resolution is increased, turbulent fluxes also increase.

• How does the model know about the subgridscale topography statistics?

• Is there a scale invariance?

• In general, the total resolved plusparameterized variables in the modelshould be independent of theresolution.

• Accuracy of parameterizations can beused to improve the model.

‐5/3

‐3

Test and ComparisonStation Disdrometer Location Elevation (m)

P 02 University of North Carolina‐Asheville (UNCA) 646

P 03 Purchase Knob (Great Smoky Mountains) 1493

P 09 Haywood Community College 794

P 11 Mount Mitchell 1897

Rainfall data Wilson and Barros (2015)

Preliminary results

Arc Length scale

30 second 0.93 km

2 minutes 3.71 km

5 minutes 9.27 km

10 minutes 18.6 km

Resolution=12 km Resolution=3 km Resolution=1 km

May 12‐16, 2014 – (IPHEx) IntegratedPrecipitation and Hydrology Experiment

Res Do1 Do2 Do3

30 s 1.8151 2.3564  3.4586

10 min 0.5338  0.8012  1.0018

P2 – Valley (646 m)

Res Do1 Do2 Do3

30 s 0.5499 1.7269  4.3881

10 min 1.7133  1.5416  1.6015

P11 – Ridge (1493 m)

Not consistant

Understandingtheimportanceofincludingoceanicmesoscalecold‐coreandwarm‐coreeddiesintropicalcyclonesimulations

Motive: Improve hurricane simulations/forecasts by determining importance of inclusion of mesoscale eddies

Problems: Lack of ocean/atmosphere coupling leads to inaccurate estimations of tropical cyclone intensityUse of climatological profiles for SST does not take into account mesoscale eddiesMany variables: translation speed and thermocline depth! 

Laura McGeeMEA 7163/15/2016

HurricaneKenneth(2005)

Pasch, Richard J. , 2006. Tropical Cyclone Report Hurricane Kenneth, 14‐30 September 2005: National Hurricane Center.  Available from http://www.nhc.noaa.gov/data/tcr/EP112005_Kenneth.pdf [Access 15 March 2016]. 

Hypothesis: Using a climatological profile, we will see a radical difference in Kenneth’s intensity—namely, intensity will not decrease.  Inclusion of mesoscale eddies in models of hurricanes with slower translation speeds (such as Hurricane Kenneth) will more accurately represent real‐life hurricane intensity.

WRF‐ARWRunGFS Analysis DataDomain: 10 to 20N, 112 to 140W12 km grid spacing3D PWP ocean model activatedNamelist options:

Microphysics scheme: WRF SM6CSLong‐ and short‐wave physics : RRTMGSurface layer physics: MM5LSM: NOAHPBL: YSUCumulus Parameterization: Tiedtke (old)

WorthinessHurricane translation speed can change due to unforeseen factorsSlow translation speed over colder/warmer waters can decrease/increase hurricane intensityKnowing intensity = vital for evacuation, damage estimates, insurance purposes

Keith SherburnMEA 716 Hypothesis Assignment

Wednesday, March 16, 2016

Overview

• High-shear, low-CAPE* (HSLC) convection represents a serious forecasting problem over portions of the U.S.

Sherburn et al. (2016, in prep.)CAPE

0-6

km s

hear

Tornado Watch Missed Tornadoes

Dean and Schneider (2008, 2012)

Tornado Watch False Alarms

Dean et al. (2009) *SBCAPE ≤ 500 J kg-1

MUCAPE ≤ 1000 J kg-1

0-6 km SVM ≥ 18 m s-1

Overview

• HSLC environments encompass a large fraction of EF1 or greater tornadoes and significant wind reports in the cool season and overnight

Sherburn et al. (2016, in prep.)

Overview

• Until recently, research on HSLC environments has primarily been limited to case studies, with little investigation into dynamics governing the evolution and strength of HSLC convection

Sherburn et al. (2016, in prep.)

• Typically associated with strong synoptic forcing for ascent, intense flow throughout the depth of the troposphere, and moist lower troposphere

• Instability, albeit limited, tends to be focused over the lowest 3 km, while low-level shear tends to be stronger in severe events

Initial Question

How is severe convection initiated and maintained in an environment with limited buoyancy?

Surface θ’ (K)

Sherburn and Parker (2015, AMS Mesoscale Conference)

Reflectivity (dBZ)

Homogeneous environment

Two approaches…

Heterogeneous environment

Reflectivity (dBZ) Courtesy: Jessica King

Initial Question

How is severe convection initiated and maintained in an environment with limited buoyancy?

Homogeneous environment

Two approaches…

Heterogeneous environment

• Initialized by a single sounding

• Initialized with cold block to mimic cold front or, perhaps more appropriately, a gust front

• i.e., need some artificial forcing to initiate convection

• Convection eventually organizes along this initial cold block or a separate, storm-generated cold pool

• Realistic?

• Pre-convective environment modulated only by convection itself

• Full four-dimensional heterogeneity

• Convection develops “naturally”, with a realistic treatment of synoptic and mesoscale influences

• Recent work has highlighted importance of low-level θe advection and potential instability in rapid environmental evolution preceding convection

• Pre-convective environment evolves due to convection and by continued synoptic and mesoscale influences

My Research Question(s)

How much of the pre-convective environmental evolution is attributable to the convection itself, and is a single-sounding approach ever sufficient to determine potential severity of an

HSLC environment?

Hypotheses: A relatively small percentage of environmental evolution is explained by the influence of the convection itself.

However, a single-sounding approach will be sufficient to provide a reasonable depiction of convection evolution and its potential severity (measured by lowest model level wind speeds and low-

level rotation tracks), assuming it is representative of the convection’s immediate environment (i.e., within ~1 hour of

convection’s arrival at a given location).

Methodology

Heterogeneous: WRF• 12-km parent domain, 4-km and 1.333-km

one-way nests

• Tiedtke CP scheme on 12-km domain, explicit otherwise

• WSM6 microphysics scheme (consistent with work by Jessica King; may experiment with others)

• YSU PBL scheme (consistent with results from Cohen et al. 2015)

• NARR initial/boundary conditions

• Plan on at least two simulations• February 26, 2008• February 24-25, 2011• Represent cases where potential instability and low-

level advection were especially important, respectively (Jessica King)

Homogeneous: CM1• 250-m grid spacing

• Previous experiments have revealed substantial changes in strength of convection between 500-m and 250-m; relatively small change between 250-m and 125-m runs

• Initialized with single sounding taken from WRF simulations 120, 90, 60, and 30 minutes prior to arrival of convection

• NSSL double-moment microphysics scheme (may change to keep consistent with WRF)

• No surface fluxes, radiation, Coriolis

• Initialized with line of warm bubbles (may use cold block if warm bubbles proves insufficient)

Preliminary Control Run and Next Steps

February 24-25, 2011Example Simulated Reflectivity

Approximate sounding locations

Comparisons:• Rotation tracks• Maximum 10-m wind

speeds• Convective mode

Next steps:• Initialize CM1

simulations with WRF soundings

• Compare CM1/WRF output