Interpretation of CAROLS L-Band measurements in the Gulf of Biscaye

Adrien Martin (1) , Jacqueline Boutin (1) , Danièle Hauser (2) , Gilles Reverdin (1) , Mickaël Pardé (2) , Mehrez Zribi (3) , Pascal Fanise (4) , Joseph Tenerelli (5) , Nicolas Reul (6)

1 LOCEAN - Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques
2 ESTER - LATMOS
3 CESBIO - Centre d'études spatiales de la biosphère
4 LATMOS - Laboratoire Atmosphères, Milieux, Observations Spatiales
5 CLS - Collecte Localisation Satellites [Toulouse]
6 LOS - Laboratoire d'Océanographie Spatiale

The L-band Cooperative Airborne Radiometer for Ocean and Land Studies (CAROLS) radiometer (Zribi et al., IGARSS 2008) flew seven times over the Gulf of Biscay between May 04 and May 26, 2009 around 20UTC. These flights followed two airborne campaigns with the same instrument in September 2007 and November 2008. Brightness temperatures (Tb) of the surface were measured by one antenna looking at 33° on the right hand side of the aircraft and optionally by a nadir antenna. The nadir antenna is sometimes exchanged with the radar scatterometer STORM in order to get a measurement of surface roughness, related to wind, coincident in space and time with the radiometric measurement. Measurements are compared with simulations conducted with the Terrestrial Radiometry Analysis Package (TRAP) (Tenerelli et al., 2008) software run for CAROLS geometry and different observed geophysical conditions. Concomitant ship campaign and drifter deployments provide in situ ground truths for sea surface salinity and temperature. Wind speed and direction are either estimated from the QSCAT scatterometer or from the STORM scatterometer and complemented with in situ observation TRAP uses the physical modeling of atmospheric radiative transfer, sea surface emissivity and galactic glint foreseen for the processing of the Soil Moisture and Ocean Salinity satellite data. The circle flights and wing-wags movements of the CAROLS aircraft (The French research ATR42 aircraft) allow to explore a wide range of incidence angles (from 0° to about 60°) and of galactic signals reflected by the sea surface. Previous flights in 2008 and 2009 have demonstrated that on a whole, simulated and observed variations of Tb with incidence angle are very consistent, demonstrating a good sensitivity of CAROLS instrument. In this presentation we will focus on the correlation between L-band radiometer measurements and scatterometer measurements, especially in a case of strong spatial gradient of wind speed (1 to 10m/s) observed in 2007 and on the signature of coastal salinity gradients on the L-band radiometer observed in 2009 during which we observed SSS variations between roughly 32 and 35.6 pss. New CAROLS flights in the Gulf of Biscay are foreseen in April and May 2010 under the track of the SMOS satellite.

Domaines: Océan, Atmosphère; Océanographie

Adrien Martin, Jacqueline Boutin, Danièle Hauser, Gilles Reverdin, Mickaël Pardé, et al.. Interpretation of CAROLS L-Band measurements in the Gulf of Biscaye. Edited by H. Lacoste-Francis. Proceedings of the ESA Living Planet Symposium 2010, ESA-SP 686, Jun 2010, Bergen, Norway. ESA, ESA-SP 686, pp.id.425, 2010. ⟨hal-00517983⟩