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Using GERB and CERES data to evaluate NWP and Climate models over the Africa/Atlantic region. Richard Allan, Tony Slingo, Ali Bharmal Environmental Systems Science Centre, University of Reading Sean Milton, Malcolm Brooks, Mark Ringer Met Office, Exeter. Outline. - PowerPoint PPT Presentation
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Using GERB and CERES data to evaluate NWP and Climate models
over the Africa/Atlantic region
Richard Allan, Tony Slingo, Ali Bharmal
Environmental Systems Science Centre, University of Reading
Sean Milton, Malcolm Brooks, Mark Ringer
Met Office, Exeter
Outline
• Use of GERB/CERES in model evaluation– Evaluation of cloud in NWP model– OLR anomaly over the W Sahara– Current activities at the Hadley Centre
• Combining surface ARM data and top of atmosphere radiation data to evaluate models
Time series (Global, 1200, Model-GERB)60S-60N clear ocean
ΔA
lbed
ocΔ
OLR
c
2003 2004 2005 2006 2007 2008
Time series (Global, 1200, Model-GERB)Δ
Alb
edoc
ΔO
LRc
Major model updatesMS7
Edition 1
SEV2;V004/5
60S-60N clear ocean
2003 2004 2005 2006 2007 2008
All-sky Clear-sky
Sh
ort
wav
eL
on
gw
ave
Biases 2006
Allan et al. (2007) QJRMS
All-sky Clear-sky
Sh
ort
wav
eL
on
gw
ave
Convective cloud
Surface albedo
Mineral dust aerosol
Marine stratocumulus
Cirrus outflow
Biases 2006
Allan et al. (2007) QJRMS
Model evaluation: near-real time
• Change in model minus GERB flux differences
• Relate to change in model physics implementation
13th March | 14th March 2006
Model SW albedo
2005 2006
• Modified convective parametrization
Increased convective cloud cover
Tropical land: model-GERB albedo difference
• Comparisons with GERB and CloudSat show improved simulation of tropical convective cloud
Allan et al. (2007) QJRMS
Time series (Global, 1200, Model-GERB)60S-60N land
ΔA
lbed
oΔ
OLR
Major model updatesMS7
Edition 1
SEV2;V004/5
Changes in boundary layer and convection schemeConvective decay time-scale parametrization
Diurnal cycle of convection
6.3um BT < 225 K
- Diagnosing convective cloud fraction: (OLRc-OLR)/cloud fraction
- Comparable to narrowband method from SEVIRI
- Model delay in convective cloud? Peak in SEVIRI total cloud at midday – spurious?
Gulf of Guinea
Model CloudSat
19th July 2006
5th July 2006
Allan et al. (2007) QJRMS
Namibian Stratocumulus
Namibian Stratocumulus
Cloud liquid water path
Bias: model minus GERB; SSM/I; SEVIRI
Albedo Liquid Water Path Cloud
Reduction in model bias from June to July 2006 - relates to cloud liquid water?
Allan et al. (2007) QJRMS
2004JJAJJA 12:00
2005JJAJJA 12:00
2006JJAJJA 12:00
2007JJAJJA 12:00
2008JJA 12:00
Time series (Global, 1200, Model-GERB)60S-60N clear land
ΔA
lbed
ocΔ
OLR
c
Major model updatesMS7
Edition 1
SEV2;V004/5
Increased Sahara albedo Improved Sahara albedo 2003 2004 2005 2006 2007 2008
Multi-model ensemble mean minus CERES EBAF 2000
LW difference SW difference
• Compare AMIP climate model ensemble– CCSM3, INMCM3, MIROC high/low, CGCM2.3, CNRM_CM3, HadGEM1
• Biases due to cloud and surface albedo• Also models overestimate OLR over W. Sahara
OLR bias
• OLR bias present for clear-sky also
• Smaller for EBAF (MODIS enhanced)
OLR bias
• OLR bias present for clear-sky also
• Smaller for EBAF (MODIS enhanced)
• Bias present for ERBE-like processing
Use of CERES/GERB at the Met Office/Hadley Centre (Mark Ringer)
• HadGEM1 was model used for IPCC AR4• HadGEM2 will be submitted to AR5
– Basic physics as HadGEM1 but will include many ‘Earth System’ processes such as C-cycle, chemistry, etc
• HadGEM3 is currently being developed– Focus on regional climate and decadal prediction– Includes completely new prognostic cloud scheme
• CERES data fully integrated into model development and evaluation– Evolving model versions and tests of parameterizations are
systematically evaluated using CERES products• GERB: Monthly mean and monthly mean diurnal cycle
would be of most use initially• Also note that these data are an important part of our work
on feedbacks and attempts to constrain climate sensitivity
EXPERIMENTEXPERIMENT
minus
CONTROL
CONTROL
minus
CERES
EXPERIMENT
minus
CERES
Development of HadGEM3:Use of CERES SW cloud forcing, impact of removing new cloud scheme.
Comparison of GERB with HadGEM1:Model forced with climatological SSTs
GERB
HadGEM1
OLR RSW
Liquid Water Content
TOA LW up
TOA SW up
Ice Water Content
retrieval
0 3 6 9 12 15 18 21 24 Time [Hours]
GERB
Lindenberg
Simulating radiative fluxes using ground-based retrievals Nicky Chalmers, Robin Hogan
LindenbergClearCloudyHigh cloud
SU
RF
AC
E
TO
A
CERES clear
-40°C
0°C
-40°C
0°C
Using methodology to evaluate NWP clouds
ClearCloudy
Cloud at all levels
ECMWF: surface LW comparison
Angular conversion factor for the Niamey GERB ARG pixel shows thataerosol alone cannot explain the discrepancy between ES96 & GERB.
Comparison of radiance and flux: Edwards/Slingo vs GERB
N. Ali Bharmal (ESSC)
Ali Bharmal in collaboration with Helen Brindley
Preliminary results comparing SBDART and ES96 RT radiances at TOAusing aerosol-free profiles suggests a disagreement in relation to thesurface/skin temperature difference.
Skin T > sfc T
Time of agreement
Conclusions• Continued near-real time comparisons between
GERB-1/SEV2 and Met Office forecast model• Large model biases have been reduced
– Surface albedo (MODIS bare soil and seasonal vegetation)– Convective cloud (convective decay time-scale)– Seasonal dust climatology likely
• Remaining problems– Marine stratocumulus too reflective
• Appears to relates to bulk water properties– Detrainment of cirrus cloud over Gulf of Guinea– Continued monitoring using GERB data
• www.nerc-essc.ac.uk/~rpa/GERB• Paper detailing previous Edition 1 comparisons published in QJRMS• www.nerc-essc.ac.uk/~rpa/PAPERS/allan_et_al07QJ.pdf• Initial comparisons between GERB/CERES and climate models• Combining surface and top of atmosphere radiation data to evaluate
models