SystematicSMOS ErrorThere:Roughness ?SST ?

From N. Reul talk at EGU 2011

From Boutin, Lorant et al. at PM20:Example of wind speed difference

WSssmi : 1.8 m/sWSecmwf : 6.85 m/sWSsmos: 4.23m/sSSSsmos-SSSargo : 1.578 psu(Ecart temporel : -0.306 h)

From Xiaobin analysis (August, ascending orbits, S. Pacific, new model)

<300km >300km ECMWF-SMOS WS

Edge of the swath : Origin of systematic bias on the not understood (not seen north of the equator.. Galactic noise???)

Equator SSS anomaly corresponds to a SMOS retrieved wind speed lower than ECMWF

SSS1(<300km)-WOA05 SSS1(<300km)-ARGO/ISAS

WS diff <300km WS diff >300km

-Monthly averaged August 2010-

SSMI WS: much lower than ECMWF WS

SMOS WS <300km ECMWF

SMOS retrieval not able to correct for WS at the swath edge (not enough incidence angle)

In situ TAO wind speed at 2S 110W:On 6 August, ECMWF ~5m/s TAO <3m/s

New analysis over 1 orbit on 6 August:(without averaging over 0.1° latitudinal bin)

Monthly average over 0.5° latitudinal bin

New analysis: error 2m/s New analysis: error 5m/s

SSS retrieved using EAFFOV and only +/-250km centered swath

SSS bias reduced with increasing error on WS

New analysis: error 2m/s New analysis: error 5m/s

Wind speed retrieved using EAFFOV and only +/-250km centered swath

More correction on WS when WS error increased

Use of EAFFOV Use of AFFOV(square in Xi, Eta of 0.25°)

SSS retrieved with 5m/s error on WS (only +/-250km centered swath)

Better correction on SSS when using AFFOV

Use of EAFFOV Use of AFFOV (square in Xi, Eta of 0.25°)

Wind speed retrieved with 5m/s error on WS (only +/-250km centered swath)

Larger correction on WS when using AFFOV

Use of AFFOV(square in Xi, Eta of 0.25°)

(5m/s error on WS)

SSS anomaly (only centered swath)

Use of EAFFOV (2m/s error on WS)

Less bias on SSS when putting an error of 5m/s on WS but larger noise!

Summary• SMOS SSS anomaly in equatorial Pacific seems to

be due to a roughness effect not enough corrected• SMOS retrieved wind speed lower than ECMWF

but not enough low• If the error on ECMWF WS is increased, SMOS

retrieved WS lower and bias on SSS removed (when using AFFOV), but larger noise on retrieved SSS!

• Not clear whether it is a problem in ECMWF wind speed or in roughness effect on microwave radiometer (SSMI wind speed very close to SMOS WS but TAO?)

ECMWF versus TAO wind speed (Jean Bidot, ECMWF)

2S-110W

East of 140W, S. Eq.

No systematic bias of ECMWF analysis although monthly SSMI wind speed lower than SMOS-ECMWF wind speed

ECMWF versus TAO wind speed (Jean Bidot, ECMWF)0S-110W

Real bias or Pb of TAO?