Using GERB and CERES data to evaluate NWP and Climate models over the Africa/Atlantic region

1. 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

2. 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

4. 60S-60N clear ocean Time series (Global, 1200, Model-GERB) ΔAlbedoc ΔOLRc 2003 2004 2005 2006 2007 2008

5. 60S-60N clear ocean Time series (Global, 1200, Model-GERB) Major model updates MS7 SEV2;V004/5 Edition 1 ΔAlbedoc ΔOLRc 2003 2004 2005 2006 2007 2008

6. All-sky Clear-sky Shortwave Longwave Biases 2006 Allan et al. (2007) QJRMS

7. All-sky Clear-sky Mineral dust aerosol Cirrus outflow Marine stratocumulus Shortwave Longwave Surface albedo Biases 2006 Convective cloud Allan et al. (2007) QJRMS

8. Model evaluation: near-real time • Change in model minus GERB flux differences • Relate to change in model physics implementation Model SW albedo 2005 2006 13th March | 14th March 2006

9. 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

10. 60S-60N land Time series (Global, 1200, Model-GERB) Major model updates MS7 SEV2;V004/5 Edition 1 ΔAlbedo ΔOLR Convective decay time-scale parametrization Changes in boundary layer and convection scheme

11. 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?

12. Gulf of Guinea Model CloudSat 5th July 2006 19th July 2006 Allan et al. (2007) QJRMS

13. Namibian Stratocumulus

14. Namibian Stratocumulus

15. 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

16. 2004 JJA JJA 12:00

17. 2005 JJA JJA 12:00

18. 2006 JJA JJA 12:00

19. 2007 JJA JJA 12:00

20. 2008 JJA 12:00

21. 60S-60N clear land Time series (Global, 1200, Model-GERB) Major model updates MS7 SEV2;V004/5 Edition 1 ΔAlbedoc ΔOLRc 2003 2004 2005 2006 2007 2008 Increased Sahara albedo Improved Sahara albedo

22. 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

23. OLR bias • OLR bias present for clear-sky also • Smaller for EBAF (MODIS enhanced)

24. OLR bias • OLR bias present for clear-sky also • Smaller for EBAF (MODIS enhanced) • Bias present for ERBE-like processing

27. 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

28. Development of HadGEM3:Use of CERES SW cloud forcing, impact of removing new cloud scheme. EXPERIMENT minus CONTROL EXPERIMENT CONTROL minus CERES EXPERIMENT minus CERES

29. Comparison of GERB with HadGEM1: Model forced with climatological SSTs OLR RSW GERB HadGEM1

30. Simulating radiative fluxes using ground-based retrievalsNicky Chalmers, Robin Hogan Lindenberg Ice Water Content Liquid Water Content retrieval GERB TOA LW up TOA SW up 0 3 6 9 12 15 18 21 24 Time [Hours]

31. Lindenberg Clear Cloudy High cloud CERES clear SURFACE TOA

32. Using methodology to evaluate NWP clouds -40°C 0°C -40°C 0°C

33. ECMWF: surface LW comparison Clear Cloudy Cloud at all levels

34. Comparison of radiance and flux: Edwards/Slingo vs GERB N. Ali Bharmal (ESSC) Angular conversion factor for the Niamey GERB ARG pixel shows that aerosol alone cannot explain the discrepancy between ES96 & GERB.

35. Ali Bharmal in collaboration with Helen Brindley Skin T > sfc T Time of agreement 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.

36. 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