1. Eumetsat conference 2004, Praha
SINERGEE: simulation and exploitation of data from MSG using an NWP model Richard Allan and Tony Slingo ESSC, Reading University, UK Sean Milton and Ian Culverwell Met Office, Exeter, UK
THANKS ALSO TO:
The GERB International Science Team (GIST)
Members of the SINERGEE project at the Met Office
Eumetsat conference 2004, Praha

2. INTRODUCTION OVERVIEW OF PROJECT DATA ISSUES AND VALIDATION
MODEL EVALUATION: Recent results
CONCLUSIONS AND FUTURE WORK

3. 1) The SINERGEE project: OVERVIEW
Near real-time (within ~24 hours) comparisons of Met Office NWP model with GERB and SEVIRI
Calibration and validation of GERB and SEVIRI
Evaluate and improve Met Office Unified Model
Studies of radiative processes involving clouds, water vapour, aerosols, etc
Results so far just use GERB broad-band fluxes
future work to include simulation of SEVIRI narrow-band radiances

4. METHODOLOGY GERB fluxes (RMIB) NWP model (Met Office)
Transferred by ftp to ESSC (Reading University)
HDF files read Data interpolated to NWP grid
Comparison of GERB and NWP at model analysis time
Displayed online:
Data stored: NetCDF/PP

5. Recent Comparison 12 May 2004 1200 UTC
OLR
ALBEDO
Recent Comparison
12 May 2004
1200 UTC

6. 2) DATA ISSUES & VALIDATION
Current data are preliminary and are being validated
Data Issues:
geolocation,
radiance to flux processing
Missing/bad data
Spectral response/calibration
Recent data (2004) use SEVIRI for radiance to flux processing, have improved geolocation and reduced missing data compared to earlier data

7. OLR
DJF means
Using SEVIRI
processing
Albedo

8. GERB minus Model Albedo
GERB minus Model OLR
Left: MJJA
Right: DJF
GERB minus Model Albedo

9. Clear-sky Flux Comparison
Compare GERB and the Model where the model fluxes are likely to be most accurate
e.g. Clear-sky OLR over the ocean
Perform comparisons where both GERB/SEVIRI and the model find clear-skies
Consistent sampling

10. Scatter plot of GERB clear-sky values versus model
May to August 2003: MS7A processing
OLR
Albedo

11. Scatter plot of GERB clear-sky values versus model
December 2003 to February 2004: SEVIRI processing
OLR
Albedo

12. Clear-sky sampled OLR and Albedo
Left:MJJA 2003
Right:DJF 2003/04
Lots of green (~0 difference) over ocean
Larger differences over Sahara: albedo, emissivity and aerosol

13. 3) MODEL EVALUATION
Example comparison:
31st March 2004, 12h00

14. Example comparison (Albedo):
31st March 2004, 12h00
MODEL ALBEDO

15. Namibian Stratocumulus region 31st March 2004

16. Shading: Albedo Contours: Cloud Fraction
Errors in the representation of sub-tropical marine stratocumulus in the model
GERB/Meteosat
Model
Shading: Albedo Contours: Cloud Fraction
July mean (1200z data)

17. Errors in the representation of tropical convection in the model
GERB/NCEP
MODEL

18. Time-series for 1200z means for 30S-30N, 40W-20E
Atlantic ITCZ region
Time-series for 1200z means for 30S-30N, 40W-20E

19. Occasional large differences in OLR seem to be due to excess cloud in the ITCZ
OLR for 1200z 1 July 2003 (shading)
Contours show vertical motion (solid=ascent, dashed=descent)
GERB
Model

20. CONCLUSIONS
Broad-band fluxes from the Met Office NWP model have been compared with GERB fluxes from RMIB in near-real time
DATA VALIDATION
data quality improving (geolocation, radiance to flux conversion, …)
clear-sky OLR over the ocean
MODEL EVALUATION
overall radiation budget is close to the observed
good representation of cloud structures in mid-latitudes
diurnal cycle of convection and grid point noise in the tropics
albedo over the Sahara
marine stratocumulus: unrealistic spatial structure and reflectivity
convection and cirrus outflow over Atlantic ITCZ

21. ADDITIONAL/FUTURE WORK
ADDITIONAL STUDIES
Radiative signature of Saharan dust
Combining GERB with model clear-sky fluxes to produce hybrid cloud forcing diagnostics
FUTURE WORK
comparisons between simulated radiances and data from SEVIRI
versions of model with higher resolution and new parametrizations
combine with surface stations to investigate atmospheric radiative divergence