18 orbits in Eastern Pacific 10-22 August reprocessed by ARGANS using : -EAFFOV -only AFFOV

1. Comparison of SMOS SSS with ARGO SSS under various Tb measurement selections J. Boutin - N. Martin – X. Yin 18 orbits in Eastern Pacific 10-22 August reprocessed by ARGANS using : -EAFFOV -only AFFOV -measurements in a square with Xi, Eta <0.25 Colocation with ARGO SSS at distance: +/-5days +/-50km For each ARGO float, average colocated SMOS SSS weighted by the error of retrieved SSS and the resolution of the pixel: <SSS>=(SSS/R2)/(1/R2) Where R is the equivalent radius Discriminate Ascending and Descending orbits Compare EAFFOV and AFFOV SSS retrievals only on pixels common to AFFOV and EAFFOV retrievals (<=>compare only retrievals made in the central swath with more than 16 AFFOV meas. used in the retrieval)

2. TX-TXmodel std(TX-TXmodel) TY-TYmodel std(TY-TYmodel) Only SSS retrieved with more than 16 meas. in AFFOV are considered

3. Ascending orbits AFFOV 3 37 3 -3 -3 32 SSSsmos (psu) SSSsmos-SSSargo (psu) SSSsmos-SSSargo (psu) EAFFOV AFFOV

4. Ascending orbits AFFOV 3 37 3 -3 -3 32 SSSsmos (psu) SSSsmos-SSSargo (psu) SSSsmos-SSSargo (psu) EAFFOV AFFOV

5. Ascending orbits – 40S-20N to avoid spurious points – Model 1 AFFOVEAFFOV AFFOV: std(SSSsmos-SSSargo)=0.65psu EAFFOV: std(SSSsmos-SSSargo)=0.54psu AFFOV: r=0.80 EAFFOV: r=0.86

6. Ascending orbits – 40S-20N to avoid spurious points in the South Xi-Eta<0.25 Xi,Eta 0.25: r=0.84 AFFOV: r=0.80 EAFFOV: r=0.86 Xi, Eta 0.25: std(SSSsmos-SSSargo)=0.57psu AFOV: std(SSSsmos-SSSargo)=0.65psu EAFFOV: std(SSSsmos-SSSargo)=0.54psu

7. Descending orbits 3 37 3 -3 -3 32 SSSsmos (psu) SSSsmos-SSSargo (psu) SSSsmos-SSSargo (psu) EAFFOV AFFOV

8. Descending orbits 3 37 3 -3 -3 32 SSSsmos (psu) SSSsmos-SSSargo (psu) SSSsmos-SSSargo (psu) EAFFOV AFFOV

9. Descending orbits – 40S-10N to avoid spurious points in the North and South AFFOV: std(SSSsmos-SSSargo)=0.74psu EAFFOV: std(SSSsmos-SSSargo)=0.59psu AFFOV: r=0.76 EAFFOV: r=0.83

10. Descending orbits – 40S-20N to avoid spurious points in the North and South Xi-Eta<0.25 Xi,Eta 0.25 std(SSSsmos-SSSargo)=0.72psu AFFOV: std(SSSsmos-SSSargo)=0.74psu EAFFOV: std(SSSsmos-SSSargo)=0.59psu Xi,Eta 0.25 r=0.73 AFFOV: r=0.76 EAFFOV: r=0.83

11. CONCLUSION (1) Better correlation and smaller rms differences between ARGO and SMOS SSS when EAFFOV measurements in the center of the track are considered Similar behavior observed with models 2 and 3 Better results with Xi,Eta=0.25 than with AFFOV probably because spurious meas. in front of AFFOV are not considered => In the future, test a rectangular area of Xi Eta that include meas. in EAFFOV but exclude meas. at the far front and at the far back of EAFFOV TY-TYmodel std(TY-TYmodel) Comparisons less scattered on ascending than on descending orbits

12. INFLUENCE OF THE NUMBER OF MEASUREMENTS USED IN THE RETRIEVAL ONTO SSSsmos-SSSargo (look at non averaged SSS differences) Number of Tb used in the retrieval Ascending orbits – AFFOV - 40S-20N to avoid spurious points – Model 1 SSSsmos-SSSargo Number of colocations

13. INFLUENCE OF THE NUMBER OF MEASUREMENTS USED IN THE RETRIEVAL ONTO SSSsmos-SSSargo AFFOV - Model 1 Ascending orbits 50 Descending orbits Number of Tb used in the retrieval

14. INFLUENCE OF THE NUMBER OF MEASUREMENTS USED IN THE RETRIEVAL ONTO SSSsmos-SSSargo EAFFOV including Xi edges - Model 1 Ascending 50 Descending Number of Tb used in the retrieval

15. SSSsmos-SSSargo individual differences more scattered when the number of Tb used in the retrieval is small, especially when the EAFFOV measurements are used. A threshold of 50 measurements (instead of 16) as proposed by ARGANS seems reasonnable