Comparison of GERB L2 fluxes (V002 and V999) with CERES and the Met Office global forecast model

1. 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

2. Recent comparison: 12th December 2005 1200 UTC

3. November 2005 animation. GERB (BARG) Model

4. Spot the difference…

5. 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

6. Diurnal animations of V999 and V002 OLR, July 2004 V999 V002

7. 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)

8. Comparison with CERES monthly-mean ERBE-like data Use combined Aqua-Terra FM1+FM4 ES4 product

9. July 2004 monthly-diurnal mean GERB (BARG, V999) CERES FM1+FM4 OLR Albedo

10. 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

11. July 2004 monthly-diurnal mean differences GERB (BARG, V002) minus CERES FM1+FM4 ∆OLR~ -5 Wm-2 ∆RSW~ -2 Wm-2 ∆Albedo~ -0.01 ∆ISW~ 0 Wm-2

12. December 2004 monthly-diurnal mean diffs GERB (BARG, V999) minus CERES FM1+FM4 ∆OLR~ -6 Wm-2 ∆RSW~ 10Wm-2 ∆ISW~ 0 Wm-2 ∆Albedo~0.03

13. 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

14. Comparison with Met Office global model simulations: SINERGEE

15. July 2004 1200 UTC Model minus GERB ∆OLR ∆Albedo V002 V999

16. OLR OLRc AOD 0.55um

17. Daytime clear-sky OLR: model minus GERB (Jun/Jul/Dec)V002 V999

18. Daytime clear-sky άSW: model minus GERB (Jun/Jul/Dec)V002 V999

19. Model minus GERB, December 2004. V002(top); V999 (bottom) 0000 0600 1200 1800

20. ∆OLR ∆Albedo December 2004 1200 UTC Model minus GERB V002 V999

21. ∆OLR ∆Albedo November 2005 1200 UTC Model minus GERB V002 Clear-sky

22. 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

23. “Global” Ocean, 1200 UTC data

24. Differences (model minus GERB) “Global” Ocean, 1200 UTC data

25. CLEAR-SKY differences (model minus GERB) “Global” Ocean, 1200 UTC data

26. Clear-sky Mediterranean 1200 UTC

27. Stray Light: evident in 0000 UTC comparisons

29. Continuing model evaluation Composites

30. Model-GERB OLR (0, 6, 12, 18 UTC) Model-GERB RSW (6, 12, 18 UTC)

31. Clear-sky LW clear-sky SW Clear-sky composites 2003-2005 MODEL GERB

32. Analysis of model marine strato-cumulus

33. Cloud radiative effect and fraction composites:Model (left) GERB(right)

34. Diurnal & daily variation in stratocumulus (July 2004): Model MPEF RMIB

35. PLANS • SINERGEE • Continued near-real time comparisons • July 2004 model experiments • SEVIRI simulations? • DABEX • RADAGAST

36. Model simulations… Proving problematic!

37. DABEX/RADAGAST