Exploitation of GERB/SEVIRI data for evaluation of the Met Office global forecast model

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Exploitation of GERB/SEVIRI data for evaluation
of the Met Office global forecast model
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
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Objectives

• Validation of new datasets (GERB/SEVIRI)
• Timely Model Evaluation
• Understanding of physical processes

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Recent Comparison
GERB Model
SEVIRI Channels 5 (left) and 10 (right)
OLR
SW Albedo
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GERB May 2006 OLR Animation
Model
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Evaluation of clear-sky fluxes
Allan et al. (2005) JGR, 110, D14111,
10.1029/2004JD005698
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Model evaluation near-real time

• Change in model minus GERB flux differences
• Relate to change in model physics implemented

Model SW albedo
2005 2006
13th March 14th March
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Time-series 1200 UTC data
OLR (Wm-2)
SW Albedo
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Systematic biases
LW Model minus GERB 1200 UTC SW
All-sky
ITCZ
Convective cloud
Low cloud
Desert dust aerosol
Clear-sky
Surface albedo
Water vapour
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Model Evaluation Namibian Stratocumulus
region31st March 2004
Model Level
10
Stratocumulus composites
Model overestimates cloud albedo Reasonable
simulation of cloud fraction
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Large clear-sky greenhouse effect over west
Sahara measured by GERB/Meteosat (July 2003) not
reproduced by Met Office model
Explained by large mineral dust aerosol optical
depth
Haywood, Allan, Slingo et al. (2005) JGR 110
D05105, doi10.1029/2004JD005232
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RADAGAST project http//radagast.nerc-essc.ac.uk
Cloud
Dust
Longwave radiative effect of desert dust from
GERB/SEVIRI
Dust product (upper) and GERB OLR (lower) for
1200UT on 8 March 2006
Lake Chad
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March 2006 dust outbreak Niamey, Niger
Units (Wm-2) TOA SFC ATM
Combine GERB, SEVIRI CERES top of atmosphere
measurements with ARM surface observations Atmosp
heric divergence
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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

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Time-series Model-GERB
?OLR (Wm-2)
?SW Albedo
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Model Evaluation Namibian Stratocumulus
region31st March 2004
Lock (2001)
Model Level

• Local time