eumetsat 2006 helsinki exploitation of gerb/seviri data for evaluation of the met office global...
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EUMETSAT 2006 Helsinki
Exploitation of GERB/SEVIRI data for evaluation of the Met Office
global forecast modelRichard 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
EUMETSAT 2006 Helsinki
Objectives
• Validation of new datasets (GERB/SEVIRI)
• Timely Model Evaluation• Understanding of physical processes
EUMETSAT 2006 Helsinki
Recent ComparisonGERB Model
OLR:
SW Albedo:
SEVIRI Channels: 5 (left) and 10 (right)
EUMETSAT 2006 Helsinki
GERB May 2006 OLR Animation Model
EUMETSAT 2006 Helsinki
Evaluation of clear-sky fluxes
Allan et al. (2005) JGR, 110, D14111, 10.1029/2004JD005698
EUMETSAT 2006 Helsinki
Model evaluation: near-real time
• Change in model minus GERB flux differences
• Relate to change in model physics implemented
13th March | 14th March
Model SW albedo
2005 2006
EUMETSAT 2006 Helsinki
Time-series: 1200 UTC data
OLR
(Wm-2)
SW Albedo
EUMETSAT 2006 Helsinki
Systematic biases
Desert dust aerosol
ITCZ
Low cloud
Surface albedo
All-sky:
Clear-sky:
LW Model minus GERB 1200 UTC SW
Convective
cloud
Water vapour
EUMETSAT 2006 Helsinki
Model Evaluation: Namibian Stratocumulus region
31st March 2004
Mod
el
Leve
l
EUMETSAT 2006 Helsinki
Stratocumulus: composites
Model overestimates cloud albedo
Reasonable simulation of cloud fraction
EUMETSAT 2006 Helsinki
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, doi:10.1029/2004JD005232
EUMETSAT 2006 Helsinki
Dust product (upper) and GERB OLR (lower) for 1200UT on 8 March 2006
Cloud
Lake Chad
Dust
Longwave radiative effect of desert dust from GERB/SEVIRI
RADAGAST project: http://radagast.nerc-essc.ac.uk
EUMETSAT 2006 Helsinki
March 2006 dust outbreak:
Niamey, Niger
Units: (Wm-2)
TOA
SFC
ATM
Combine GERB, SEVIRI & CERES top of atmosphere measurements with ARM surface observations…
Atmospheric divergence
EUMETSAT 2006 Helsinki
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…
EUMETSAT 2006 Helsinki
Time-series: Model-GERB∆OLR
(Wm-2)
∆SW Albedo
EUMETSAT 2006 Helsinki
Model Evaluation: Namibian Stratocumulus region
31st March 2004
Mod
el
Leve
l
Lock (2001)
Local time