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)

Comparison of SMOS SSS with ARGO SSS under various Tb measurement selections

J. Boutin - N. Martin – X. Yin

TX-TXmodel

TY-TYmodel

std(TX-TXmodel)

std(TY-TYmodel)

Only SSS retrieved with more than 16 meas. in AFFOV are considered

EAFFOV

AFFOV

Ascending orbits

SSSsmos (psu) SSSsmos-SSSargo (psu) SSSsmos-SSSargo (psu)

32

37

-3

3

-3

3

AFFOV

EAFFOV

AFFOV

Ascending orbits

SSSsmos (psu) SSSsmos-SSSargo (psu) SSSsmos-SSSargo (psu)

32

37

-3

3

-3

3

AFFOV

Ascending orbits – 40S-20N to avoid spurious points – Model 1

AFFOV EAFFOV

AFFOV: std(SSSsmos-SSSargo)=0.65psuEAFFOV: std(SSSsmos-SSSargo)=0.54psu

AFFOV: r=0.80EAFFOV: r=0.86

Ascending orbits – 40S-20N to avoid spurious points in the South

Xi-Eta<0.25

Xi,Eta 0.25: r=0.84AFFOV: r=0.80EAFFOV: r=0.86

Xi, Eta 0.25: std(SSSsmos-SSSargo)=0.57psu AFOV: std(SSSsmos-SSSargo)=0.65psuEAFFOV: std(SSSsmos-SSSargo)=0.54psu

EAFFOV

Descending orbits

SSSsmos (psu) SSSsmos-SSSargo (psu) SSSsmos-SSSargo (psu)

32

37

-3

3

-3

3

AFFOV

EAFFOV

Descending orbits

SSSsmos (psu) SSSsmos-SSSargo (psu) SSSsmos-SSSargo (psu)

32

37

-3

3

-3

3

AFFOV

Descending orbits – 40S-10N to avoid spurious points in the North and South

AFFOV: std(SSSsmos-SSSargo)=0.74psuEAFFOV: std(SSSsmos-SSSargo)=0.59psu

AFFOV: r=0.76EAFFOV: r=0.83

Descending orbits – 40S-20N to avoid spurious points in the North and South

Xi-Eta<0.25

Xi,Eta 0.25 std(SSSsmos-SSSargo)=0.72psuAFFOV: std(SSSsmos-SSSargo)=0.74psuEAFFOV: std(SSSsmos-SSSargo)=0.59psu

Xi,Eta 0.25 r=0.73AFFOV: r=0.76EAFFOV: r=0.83

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

CONCLUSION (1)

Comparisons less scattered on ascending than on descending orbits

TY-TYmodel std(TY-TYmodel)

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

INFLUENCE OF THE NUMBER OF MEASUREMENTS USED IN THE RETRIEVAL ONTO SSSsmos-SSSargo

AFFOV - Model 1

Ascending orbits

Descending orbits

Number of Tb used in the retrieval

50

Descending

INFLUENCE OF THE NUMBER OF MEASUREMENTS USED IN THE RETRIEVAL ONTO SSSsmos-SSSargo

Number of Tb used in the retrieval

Ascending

EAFFOV including Xi edges - Model 1

50

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