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GERB/CERES Meeting 2006 Exeter Evaluation of clouds and radiation in the Met Office global forecast model using GERB/SEVIRI data Richard Allan, Tony Slingo.

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Presentation on theme: "GERB/CERES Meeting 2006 Exeter Evaluation of clouds and radiation in the Met Office global forecast model using GERB/SEVIRI data Richard Allan, Tony Slingo."— Presentation transcript:

1 GERB/CERES Meeting 2006 Exeter Evaluation of clouds and radiation in the Met Office global forecast model using GERB/SEVIRI data Richard Allan, Tony Slingo Environmental Systems Science Centre University of Reading, UK Sean Milton, Malcolm Brooks Met Office, Exeter, UK With thanks to the GERB International Science Team including colleagues at Imperial College and the Royal Meteorological Institute of Belgium

2 GERB/CERES Meeting 2006 Exeter Objectives Validation of new datasets (GERB/SEVIRI) Timely Model Evaluation Understanding of physical processes

3 GERB/CERES Meeting 2006 Exeter Recent Comparison GERBModel OLR: SW Albedo: SEVIRI Channels: WV (top) and IR (bottom)

4 GERB/CERES Meeting 2006 Exeter Evaluation of clear-sky fluxes Allan et al. (2005) JGR, 110, D14111, /2004JD005698

5 GERB/CERES Meeting 2006 Exeter Model evaluation: near-real time Change in model minus GERB flux differences Relate to change in model physics implemented 13 th March | 14 th March Model SW albedo OLR ALB Model-GERB: tropical land

6 GERB/CERES Meeting 2006 Exeter Model evaluation: near-real time Change in model minus GERB flux differences Relate to change in model physics implemented 13 th March | 14 th March Model SW albedo Model-GERB: tropical land ΔOLR ΔALB

7 GERB/CERES Meeting 2006 Exeter Time-series: 1200 UTC data OLR (Wm -2 ) SW Albedo

8 GERB/CERES Meeting 2006 Exeter July 2006 mean ModelGERB (Edition 1) CERES OLRαOLRα

9 GERB/CERES Meeting 2006 Exeter Systematic biases All-sky: Clear -sky: Desert dust aerosol ITCZ Low cloud Surface albedo Convective cloud Water vapour LW Model minus GERB 1200 UTC SW

10 GERB/CERES Meeting 2006 Exeter Model Evaluation: Namibian Stratocumulus region 31 st March 2004 Model Level

11 GERB/CERES Meeting 2006 Exeter More recent example 5 th June 2006 Model Level

12 GERB/CERES Meeting 2006 Exeter Stratocumulus: composites (Edition 1 data) Model overestimates cloud albedo Reasonable simulation of cloud fraction

13 GERB/CERES Meeting 2006 Exeter Composites: April-July 2006 Sample only where stratocumulus identified Model: reasonable simulation of cloud cover and longwave radiative effects Underestimation of SW albedo LWCF (Wm -2 ) ALB CF: Frequency of Sc:

14 GERB/CERES Meeting 2006 Exeter Diurnal Cycle

15 GERB/CERES Meeting 2006 Exeter Time series

16 GERB/CERES Meeting 2006 Exeter Large error in model simulated clear-sky OLR over west Sahara identified in July 2003 also present in 2006 for Edition 1 GERB data Partially explained by large mineral dust aerosol optical depth See RADAGAST project: and also: Haywood, Allan, Slingo et al. (2005) J. Geophys. Res. 110http://radagast.nerc-essc.ac.uk

17 GERB/CERES Meeting 2006 Exeter Summary Ongoing near-real time comparisons of GERB/SEVIRI and Model Validation of new datasets –GERB/SEVIRI, surface observations Timely model evaluation –e.g. new physical parametrizations Process studies –e.g., stratocumulus, surface properties, mineral dust, radiative flux divergence…

18 GERB/CERES Meeting 2006 Exeter Time-series: Model-GERB OLR (Wm -2 ) SW Albedo

19 GERB/CERES Meeting 2006 Exeter


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