1. Assessment of one year of Medspiration L4 fields J. Tournadre, J.F. Piollé and E. Autret

2. Since January 2006 we have stabilized the OA configuration of the Medspiration L4 processing –Daily, 2km resolution, night-time data only –NAR17-18, Seviri, AATSR, AMSRE, TMI, AVHRR 17-18 Gac and LAc More than one year of homogeneous data are now available Analysis of this data set L2P and L4 processing geophysical applications

3. L4 works even if not perfectly Strong Mistral event at the beginning of August 2006 cooled down the French Riviera by more than 5K !! SST  SST Qscat wind

4. Which L2P do we use?? L4 = OA of L2P

5. Area covered Number of days sampled /year AMSRE AATSR SEVIRI NAR17 NAR18 SEVIRI has the largest temporal and spatial coverage and constitutes the base of the L4 analysis even if the number of samples /day is 10 times smaller than the AVHRR ones.

6. How do these L2P data feeding the L4 OA compare to each other? Difference between collated and L4 SST for April 2006 NAR17 (AVHRR17) no bias (first choice in data selection after AATSR) Large biases for NAR18 Strong regional biases for SEVIRI AATSR strong local biases (not enough samples)

7. Strong temporal and spatial variability of inter-sensor biases For July 2006 from –0.5 to 0.5K Especially strong in upwelling regions.

8. The regional biases are partially due to the SST local variability SST RMS in 0.5° boxes Feb SST RMS in 0.5° boxes Aug

9. Related to strong surface SST gradients

10. Strong temporal variability of the inter-sensor biases Comparison of collated data with NAR17 collated

11. Most of the problems we encountered during this year of operation are related to large biases between sensors (sometimes more than 1.5K) These biases are highly variable in time and space. Improvement of the L4 fields can only come from an improvement of the intercalibration of sensors.

12. What can we do with the L4 products? Annual variation of SST for 3 location Near Atlantic Gulf of Lions Eastern Med SST RMS in 0.5°boxe SST Mistral event

13. Seasonal Cycle in the Med Amplitude Day of maximum SST Max at end of summer Max at early August Max at early september Weak cycleStrong cycleMedium cycle

14. Mean change of SST over the meddspiration zone Western Bassin an central bassin cooling heating Mistral

15. Detail of the Mistral event which seems to condition the SST evolution in at least the western and central med basins Intense heating in the Gulf of Lions July Intense cooling in the Gulf of Lions July Low winds Mistral

16. L4 : good data base to study the evolution and variability of SST at fine temporal and spatial scale More studies needed and more validation

17. Spectral analysis of Western, Central and Eastern Med. Basins. Daily spectra Both for validation and geophysical studies purposes Both short scale ans seasonnal variations

18. Latitudinalzonal 10km Seviri spectral peak Mean spectral behaviour of SST in the 3 basins Different spectral slopes Difference of slope

19. Westen basin zonal spectra Seasonal variation Short period variations associated with weather patern spectraSpectra anomalies

20. Spectral slope Change associated to Mistral event

21. Temporal spectra Western (black) and Central (green) basins 10 days 3 days Western Central

22. A look at the diurnal cycle? Seviri –L4 every3 hours DC=Max -Min DW GradSST  SST/  t Wind DC  SST/  t

23. Number of days with DW greater than 0.5, 1 and 2K

24. Perspective Still work to do to improve the L4 products Mainly in the inter-calibration of L2P SST SSES can certainly improve but not everything. Dynamical inter-calibration method necessary More validation work to be conducted As it is L4 fields gives a very easy to use data base to better study/understand the dynamics of the Mediterranean Sea.