COMBINED BACKSCATTER AND DOPPLER SHIFTS FROM SAR IMAGES: OBSERVATIONS, SYNERGIES AND SIMULATIONS

摘要

The Advanced Synthetic Aperture Radar (ASAR) instrument on ESA's Envisat has recently demonstrated a new and very valuable source of information, namely, the line-of-sight velocity of the moving ocean surface. This velocity triggers the measured Doppler frequency shift and is composed of the combined action of near surface wind speed on shorter waves, longer wave motion and wave breaking and finally surface current. It complements the normalized radar cross-section measurements so that both kinematic and dynamic properties of the surface roughness can be derived from SAR observations. In this paper we first demonstrate the value of regular Doppler velocity estimates from ASAR wide swath data for the Agulhas Current. Then new and promising results are presented from a comparison of the observed and simulated Doppler frequency shift using ASAR wave mode data and a radar imaging model extended with a Doppler shift module.