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 ΔAlbedocΔOLRc

Time series (Global, 1200, Model-GERB) ΔAlbedocΔOLRc Major model updates MS7 Edition 1 SEV2;V004/5 60S-60N clear ocean

All-sky Clear-sky ShortwaveLongwave Biases 2006 Allan et al. (2007) QJRMS

All-sky Clear-sky ShortwaveLongwave 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 13 th March | 14 th March 2006 Model SW albedo

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 ΔAlbedoΔOLR Major model updates MS7 Edition 1 SEV2;V004/5 Changes in boundary layer and convection scheme Convective 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 ModelCloudSat 19 th July th July 2006 Allan et al. (2007) QJRMS

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 relates to cloud liquid water? Allan et al. (2007) QJRMS

2004 JJAJJA 12:00

2005 JJAJJA 12:00

2006 JJAJJA 12:00

2007 JJAJJA 12:00

2008 JJA 12:00

Time series (Global, 1200, Model-GERB) 60S-60N clear land ΔAlbedocΔOLRc Major model updates MS7 Edition 1 SEV2;V004/5 Increased Sahara albedoImproved Sahara albedo

Multi-model ensemble mean minus CERES EBAF 2000 LW differenceSW 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

EXPERIMENT minus 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 Time [Hours] GERB Lindenberg Simulating radiative fluxes using ground-based retrievals Nicky Chalmers, Robin Hogan

Lindenberg Clear Cloudy High cloud SURFACE TOA CERES clear

-40°C 0°C0°C 0°C0°C Using methodology to evaluate NWP clouds

Clear Cloudy Cloud at all levels ECMWF: surface LW comparison

Angular conversion factor for the Niamey GERB ARG pixel shows that aerosol 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 TOA using aerosol-free profiles suggests a disagreement in relation to the surface/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 Paper detailing previous Edition 1 comparisons published in QJRMS Initial comparisons between GERB/CERES and climate models Combining surface and top of atmosphere radiation data to evaluate models