Download - Comparison of GERB L2 fluxes (V002 and V999) with CERES and the Met Office global forecast model
![Page 1: Comparison of GERB L2 fluxes (V002 and V999) with CERES and the Met Office global forecast model](https://reader035.vdocument.in/reader035/viewer/2022062803/5681478c550346895db4bb3d/html5/thumbnails/1.jpg)
Comparison of GERB L2 fluxes (V002 and V999) with CERES
and the Met Office global forecast model
Richard Allan
Environmental Systems Science Centre, University of Reading
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Recent comparison:
12th December 2005 1200 UTC
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November 2005 animation.
GERB (BARG) Model
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Spot the difference…
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Comparison of V002 and V999 L2 GERB fluxes
- Diurnal cycle- Monthly mean comparison with CERES- Comparison with Met Office global model- Time-series including latest data
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V999 V002
Diurnal animations of V999 and V002 OLR, July 2004
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V999 Improvements
• Dawn/Dusk “wobble” and artifacts• Line of anomalously high OLR ~ equator• Hot spots removed (N. Sahara)
• ?problem with sun-glint
• Also note: Gulf of Guinea, Brazil convection, mid-latitude “noise” (see Ruth’s talk)
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Comparison with CERES monthly-mean ERBE-like data
Use combined Aqua-Terra FM1+FM4 ES4 product
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July 2004 monthly-diurnal mean
GERB (BARG, V999) CERES FM1+FM4
OLR
Albedo
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July 2004 monthly-diurnal mean differences GERB (BARG, V999) minus CERES FM1+FM4
∆OLR~ -6 Wm-2
∆RSW~ -8 Wm-2
∆Albedo~ 0.02
∆ISW ~ .2 Wm-2
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July 2004 monthly-diurnal mean differences GERB (BARG, V002) minus CERES FM1+FM4
∆OLR~ -5 Wm-2
∆RSW~ -2 Wm-2
∆ISW~ 0 Wm-2
∆Albedo~ -0.01
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December 2004 monthly-diurnal mean diffs GERB (BARG, V999) minus CERES FM1+FM4
∆Albedo~0.03
∆OLR~ -6 Wm-2
∆RSW~ 10 Wm-2
∆ISW~ 0 Wm-2
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CERES comparison: summary
• LW: GERB is 2.5% < CERES (~ 6 Wm-2)– V999 has removed view-angle dependence
• SW: GERB(V999) ~10% > CERES– ~10 Wm-2 RSW or 0.02-0.03 albedo – V002: smaller differences
• Differences apply for July and December 2004
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Comparison with Met Office global model simulations:
SINERGEE
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∆OLR ∆AlbedoJuly 2004 1200 UTC
Model minus GERB
V002
V999
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OLR
OLRc
AOD
0.55um
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Daytime clear-sky OLR: model minus GERB (Jun/Jul/Dec) V002 V999
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Daytime clear-sky άSW: model minus GERB (Jun/Jul/Dec)
V002 V999
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0000 0600 1200 1800
Model minus GERB, December 2004. V002(top); V999 (bottom)
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December 2004
1200 UTC
Model minus GERB
∆OLR ∆Albedo
V002
V999
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November 2005
1200 UTC
Model minus GERB
Clear-sky
V002
∆OLR ∆Albedo
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Summary: V002-V999
• Improved diurnal cycle of OLR (sunglint?)• Monthly-diurnal mean vs CERES
– GERB LW ~2.5% < CERES (V002 similar)– GERB SW ~10% > CERES (V002 less)
• Sahara: increase in model-GERB diffs in LW and SW– but regions of known error (mineral dust, surface albedo)
• Oceans: reduction in model-GERB SW difference– Model low-clouds are too reflective
• Clear-sky fluxes over ocean: agreement with model remains– some improvement although GERB is now more reflective over
Mediterranean and Canaries
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“Global” Ocean, 1200 UTC data
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Differences (model minus GERB)
“Global” Ocean, 1200 UTC data
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CLEAR-SKY differences (model minus GERB)
“Global” Ocean, 1200 UTC data
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Clear-sky Mediterranean 1200 UTC
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Stray Light: evident in 0000 UTC comparisons
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Continuing model evaluationComposites
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Model-GERB OLR (0, 6, 12, 18 UTC)
Model-GERB RSW (6, 12, 18 UTC)
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Clear-sky composites 2003-2005
MODEL
GERB
Clear-sky LW clear-sky SW
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Analysis of model marine strato-
cumulus
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Cloud radiative effect and fraction
composites:
Model (left) GERB(right)
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Diurnal & daily variation in stratocumulus (July 2004):
Model
MPEF
RMIB
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PLANS
• SINERGEE– Continued near-real time comparisons– July 2004 model experiments– SEVIRI simulations?
• DABEX
• RADAGAST
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Model simulations…
Proving problematic!
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DABEX/RADAGAST