Analysis of AMSR-E C & X-band Tb data dependencies with

wind & wave characteristics

Questions ?

• How is Roughness-induced sea surface emissivity in the low frequency microwave domain dependent with sea surface state & wave developement ?

• Impacts of swell, pure wind seas or mixed sea states on the emissivity at X, C & L -bands?

• Needs to get sea state parametrization & active/passive roughness effects consistency in the aquarius L-band SSS retrieval algorithm

How ?• Collect one month (aug 2010) of global L2A AMSR-E Tbs & L2

ocean products (sst, wind, water vapor, …) • Evaluate surface emissivity e surf residuals based on Wentz

algorithm for atmospheric & external sources corrections• Co-locate AMSR-E data with wave parameters (total significant

wave height Hs, significant wave height for wind sea Hsws ) from ECMWF-WAM model forecasts (3-hourly at 0.25° res) and ECMWF U10

• Estimate roughness-induced residuals Δerough using in situ SSS & AMSRE.SST to evaluate flat sea contribution

• Look @ statistical depedencies of Δerough with bins of Hs,U10 & Hsws

Déploiement, Collecte & Traitement des Données In situ de surface pour la Validation de SMOS

SSS field from in situ data

Projet GLOSCAL

Objectively analyzed in situ SSS

Exemple of the Data set over 1 month @ 25 km resolution

Objectively Analyzed Standardized in situ data+climatology

LPO

LPO

Dielectric constant model (Klein & swift, 76)

Estimating the Flat sea surface Tbs contributions

Estimated monthly mean-averagedFlat sea surface Tbs contributions for X & C, H-V AMSR-E channels

Estimated surface Tbs from X & C, H-V AMSR-E data

Wind & wave products

Co-localisation AMSR-ECMWF: |Δ t|<1.5 Hour & | Δ x|<25 km

Estimated monthly-averaged roughness induced emissivity residuals

Mean Roughness induced emissivity residuals as function of surface wind speed

Mean Roughness induced emissivity residuals as function of surface wind speed & total significant wave-height

Selection of data for ECMWF winds 4.5<U10<5.5 m/s

Illustration of the Mean Large Scale Wave impact on Roughness induced emissivity residuals at a fixed surface wind speed of ~5 m/s

Histograms of Hs for all waves and wind sea at U10~5m/s

Wind sea~0.5m

swells~0.5-3 m

Very distinct distributions

The Hs changes at U10~5m/s are dominated by swell impact

Selection of data for ECMWF winds 4.5<U10<5.5 m/s

Illustration of the Mean Large Scale Wave impact on Roughness induced emissivity residuals at a fixed surface wind speed of ~5 m/s

For wind speed ~5 m/s, swells affect surface emissivity at 55° incidence angle and H-pol, have a negligible impact in V-pol

Illustration of the Mean Large Scale Wave impact on Roughness induced emissivity residuals at a fixed surface wind speed of ~8 m/s

Monthly average signature of tropical freswaterpools in AMSR-E Tbs

Monthly average signature of Tropical Atlantic freshwaterpools in AMSR-E Tbs

Orrinoco River Amazon River

Niger River

Congo RiverSenegal &Geba Rivers

Mississipi Delta

Freshwater runoff into the Tehuantepec Gulf

Ganges and Brahmaputra RiversIrrawaddy Delta

Indus Delta

Yangtse River