simulation of the aerosol indirect effect in gcm
DESCRIPTION
1 st. and. 2 nd. Aerosol Indirect Effect. Simulation of the Aerosol Indirect Effect in GCM. Radiative Transfer. Microphysics. Onset of Précipitation. CCN Activation. Précipitation Evaporation. Cloud Dynamics. CLOUDNET J. L. Brenguier Météo-France. - PowerPoint PPT PresentationTRANSCRIPT
Simulation of the Aerosol Indirect Effect in GCM
CLOUDNET J. L. Brenguier Météo-France
Cloud Dynamics PrécipitationEvaporation
Microphysics
Onset ofPrécipitation
2ndand
1st Aerosol Indirect Effect
CCN Activation
RadiativeTransfer
ACE-2 Field Campaign June-July 1997
CLOUDNET J. L. Brenguier Météo-France
Morocco
SurfaceSite
Tenerife
Experimental StrategyTo select cloud systemswith similar LWP andmorphology, but withdifferent aerosol prop.To sample an area of60 km, about the GCMspatial resolutionTo synchronize in situand remote sensingfor column closureexperiments
Nact=50 cm-3 Nact=250 cm-3
ACE-2 Field Campaign June-July 1997
CLOUDNET J. L. Brenguier Météo-France
Multi-disciplinary: aerosol chemistry and physics, cloud microphysics cloud radiative transfer First experiment with detailed characterization of aerosols and simultaneous measurements of cloud microphysics in situ and radiative properties from above Observation area of 60 km side sampled during 4 hours: robust statistics BUT Measurements at noon local time No radar/lidar No vertical profile, No diurnal cycle
ACE-2 Special Issue of Tellus 2000
JLB et al. JAS 2000
ACE-2 Field Campaign June-July 1997
CLOUDNET J. L. Brenguier Météo-FranceJLB et al. 2003
Meteo-France: J.L. Brenguier FUBerlin: L. Schüller
U Warsaw: H. Pawlowska U Wyoming: J. Snider
MPI: J. Feichter Hadley: D. Roberts
U Dalhousie: U. Lohmann U Columbia: S. Menon
PNNL: S. Ghan U Michigan: J. Penner LMD: J. Quaas
CLOUDNET J. L. Brenguier Météo-France
PACECooperative Study between
ACE-2 Experimentalists and GCM Modellersfor Testing/Developing GCM Parameterizations
on the ACE-2 data set
PACE Special Issue of JGR August 2003 (Data Analysis
Menon et al. JGR 2004 (Model Parameterizations)
Series of Closure experiments at a scale relevant to GCM (60 km) on - aerosol activation
- radiative transfer- precipitation formation
Identify variables relevant to GCM parameterization of AIE and establish relationship with physical variables Build a data base for initialisation and validation of SCM versions of the GCMs (8 ACE-2 case studies) Examine the predictability of the selected variables Test parameterizations and examine feedback processes
CLOUDNET J. L. Brenguier Météo-France
PACE METHODOLOGY
CLOUDNET J. L. Brenguier Météo-France
Microphysics
1st Aerosol Indirect Effect
CCN Activation
Well known since 50 yearsWell known since 50 yearsfrom from - in situ measurements- in situ measurements- & 1D to 3D modelling- & 1D to 3D modelling
51
208 256
134
178
114
134
Droplet Mean Volume Diameter versus Height above Cloud Base(Pawlowska et al. 2000)
N=75cm-3
CLOUDNET J. L. Brenguier Météo-France
CLOUDNET J. L. Brenguier Météo-France
Can we predict CDNC at the GCM resolution scale from predicted aerosol properties and a diagnostic of updraft intensity
qc(h)>0.9 qcad(h)
Ndrizzle< 2cm-3
0.4H < h < 0.6H
Pawlowska et al. 2000
CLOUDNET J. L. Brenguier Météo-France
MicrophysicsCCN Activation
Closure Experiments State of the ArtClosure Experiments State of the Art
CDNC predicted CDNC predicted with detailed process modelswith detailed process models initialised with measured initialised with measured
aerosol physico-chemical aerosol physico-chemical properties and wproperties and w
OVERESTIMATESOVERESTIMATES
measured CDNCmeasured CDNC 0
200
400
600
CD
NC
, cm
-3
18-July
Snider et al. 2003
State of the art in GCM simulation of AIE
CLOUDNET J. L. Brenguier Météo-France
Menon et al. 2004
CLOUDNET J. L. Brenguier Météo-France
MicrophysicsCCN Activation
CONCLUSIONS : NOT SO BADCONCLUSIONS : NOT SO BAD
Discrepancies attributed to Discrepancies attributed to - incomplete characterization of aerosol propertiesincomplete characterization of aerosol properties- and biased vertical velocityand biased vertical velocity
GCM Parameterization of activation is NOT AN ISSUEGCM Parameterization of activation is NOT AN ISSUE except subgrid scheme to derive local w from grid TKEexcept subgrid scheme to derive local w from grid TKEand better representation of aerosol physico-chemical propertiesand better representation of aerosol physico-chemical properties
CLOUDNET J. L. Brenguier Météo-France
Microphysics
1st Aerosol Indirect Effect
Numerous experimental evidencesNumerous experimental evidencesfrom multispectral radiancesfrom multispectral radiances- satellites- satellites- close remote sensingclose remote sensing BUTBUT- Very few that discriminate betweenVery few that discriminate between impact of microphysicsimpact of microphysics and impact of LWPand impact of LWP
Radiative Transfer
CLOUDNET J. L. Brenguier Météo-France
Measured reflectances in VIS and NIR, with H-N gridN remotely retrieved values versus Nact
Microphysics
1st Aerosol Indirect Effect
Radiative Transfer
CLOUDNET J. L. Brenguier Météo-France
CLOUDNET J. L. Brenguier Météo-France
CLOUDNET J. L. Brenguier Météo-France
Microphysics
Closure Experiments State of the ArtClosure Experiments State of the Art
CDNC predicted CDNC predicted with detailed radiative with detailed radiative
(inverse) transfer models(inverse) transfer models initialised with measured initialised with measured
multispectral radiancesmultispectral radiances
AGREE withAGREE with
measured CDNCmeasured CDNC
Radiative Transfer
Schüller et al. 2003
CLOUDNET J. L. Brenguier Météo-France
Satellite Monitoring of the AIE Correlation between Cloud Optical Thickness and Droplet Effective Radius
- 1
CLOUDNET J. L. Brenguier Météo-France
CONCLUSIONS : QUITE GOODCONCLUSIONS : QUITE GOOD
Discrepancies attributed to Discrepancies attributed to - heterogeneities of the microphysical fieldsheterogeneities of the microphysical fields- optical properties of aerosols and dropletsoptical properties of aerosols and droplets
GCM Parameterization of radiative transfer is AN ISSUEGCM Parameterization of radiative transfer is AN ISSUE because of the poor representation of clouds in GCM,because of the poor representation of clouds in GCM,not because of the susceptibility to CDNCnot because of the susceptibility to CDNC
Microphysics Radiative Transfer
Measurements of the Aerosol Indirect Effect
CLOUDNET J. L. Brenguier Météo-France
Microphysics
Aerosol Indirect Effect
Well known since 50 yearsWell known since 50 yearsfrom from - in situ measurements- in situ measurements- & 1D to 3D modelling& 1D to 3D modellinghas been carefully explored for weather has been carefully explored for weather
modification, without success though!!! modification, without success though!!!
Onset ofPrécipitation
PrécipitationEvaporation
2nd
CLOUDNET J. L. Brenguier Météo-France
Microphysics
Closure Experiments State of the ArtClosure Experiments State of the Art
Measured drizzle Measured drizzle concentration depends concentration depends on the maximum radius on the maximum radius droplets can reach in a droplets can reach in a cloud layer and the cloud layer and the threshold (10µm) threshold (10µm) corresponds to the corresponds to the value derived from value derived from detailed modelling of detailed modelling of droplet coalescencedroplet coalescence
Onset of Précipitation
Pawlowska et al. 2003
Aerosol-CNES September 2003 J. L. Brenguier Météo-France
CONCLUSIONS : Very badCONCLUSIONS : Very bad
Microphysics Précipitation Evaporation
Pawlowska et al. 2003
Menon et al. 2003
Parameterization of precipitation in GCM
EGS 7 April 2003 Nice J. L. Brenguier Météo-France
Detailed microphysics 1 to 3-D (50 to 200 variables)
3-D CRM Runs (diverse conditions)Tripoli-Cotton, Beheng, Khairoutdinov-Kogan
Bulk microphysics for CRM (3 variables: N, qc, qr)Auto-conversion (N, qc) and Accretion (N, qc, qr)
Tuning bulk coefficients to accountfor GCM grid smoothing effects
Bulk microphysics for GCM (2 variables : N, qc)Auto-conversion (N, qc) (Accretion diagnosed)
3-D bulk CRM Runs (meso-scale)
Bulk microphysics for GCM (2 variables : N, H)Average precipitation rate from multi-cells in stationary state
CLOUDNET J. L. Brenguier Météo-France
CRM versus GCM PARAMETERIZATIONCRM versus GCM PARAMETERIZATIONOF PRECIPITATIONOF PRECIPITATION
H. PawlowskaH. Pawlowska
CLOUDNET J. L. Brenguier Météo-France
Model variability attributed toModel variability attributed tothe use of CRM bulkthe use of CRM bulkparameterizations ofparameterizations ofauto-conversion and accretionauto-conversion and accretionin GCM.in GCM.
New bulk parameterizationsNew bulk parameterizationsare tested (ACE2, DYCOMS),are tested (ACE2, DYCOMS),where precipitation rate onlywhere precipitation rate onlydepends on LWP and CDNCdepends on LWP and CDNC
Microphysics Précipitation Evaporation
Pawlowska et al. 2003
CLOUDNET J. L. Brenguier Météo-France
Microphysics Cloud Life Cycle
Experimental strategy for BL cloudsExperimental strategy for BL cloudsAerosols have a strong impact on the onset of precipitationAerosols have a strong impact on the onset of precipitationand precipitation rate, but it is not obvious that they have anand precipitation rate, but it is not obvious that they have animpact on the cloud life cycle.impact on the cloud life cycle.
In BL clouds, the contribution of precipitation to the water budgetIn BL clouds, the contribution of precipitation to the water budgetis comparable to the contributions of radiative & turbulent fluxes.is comparable to the contributions of radiative & turbulent fluxes.
The uncertainty in measurements of these fluxes are still higherThe uncertainty in measurements of these fluxes are still higherthan the fluxes themselve.than the fluxes themselve.
Requires long term monitoring of the cloud life cycle at a super siteRequires long term monitoring of the cloud life cycle at a super siteequipped with surface fluxes, radar and lidar remote sensingequipped with surface fluxes, radar and lidar remote sensingand concomitant aerosol characterizationand concomitant aerosol characterization
State of the art in GCM simulation of AIE
EGS 7 April 2003 Nice J. L. Brenguier Météo-France
CONCLUSIONMost of the uncertainty comes from the coarse representation
of thin BL clouds in GCMsMVDR at cloud top H1/3, Optical depth H5/3, Precipitation rate H4
Priorities- Finer vertical resolution and sub-grid vertical schemes - « GCM Bulk » parameterization of rain formation - Reduce the bias in the prediction of Nact - Better understand the heterogenous bias in relation with
the second AIE - Parameterizations of the aerosol processing in clouds
Turbulent Fluxes
Entrainment-Mixing
rv=20 g kg-1
rl=0.2 g kg-1
PrécipitationEvaporation
A=0.05
A=0.50
Microphysics
Trv
Onset ofPrécipitation
1st 2ndand
CLOUDNET J. L. Brenguier Météo-France
Aerosol Indirect Effect
Boundary Layer Clouds
CCN Activation
RadiativeTransfer