Interpretation of CAROLS L-band Measurements in the Gulf of Biscay (September 2007)

摘要

The L-band Cooperative Airborne Radiometer for Ocean and Land Studies (CAROLS) radiometer flew four times over the Gulf of Biscay between September 24 to September 28, 2007 around 20UTC. These flights were the first ones over the ocean of this new instrument. Concomitant ship campaign and drifter deployments provide in situ ground truths for sea surface salinity (between 34.6 and 35.8 pss) and temperature (between f5°C and 17°C). Wind speed (between 2 and 10 m/s) and direction are estimated from the QSCAT scatterometer. Observed variations of CAROLS brightness temperatures in horizontal polarization are very consistent with the ones simulated using a direct modeling of L-band radiometric signals over the ocean, demonstrating a good sensitivity of CAROLS instrument and the realism of the modeling. During circle flights during which variations of the galactic signal scattered by the sea surface was moderate (less than 0.5 K), observed azimuth variations at 15° incidence angle are consistent with the galactic noise signal scattered by the sea surface plus a small signal due to rough sea asymmetry as simulated by a two-scale model. On September 28, a more than 1 K increase of Tb over 2° longitude is observed, linked to an increase of wind speed from 3 to 8 m/s.