Radiative transfer equation with surface scattering for ocean and atmospheric parameters retrieval from radiometric measurements

Abstract

Microwave radiometers have been used with success in the past for the retrieval of ocean surface and atmospheric parameters. However,for the most effective use of the measurements provided by these instruments, it is neeessary that performant inversion algorithms be available. Existing algorithms have already proved their usefulness but are often based on statistical regressions on the measurements from some particular experiment or on artifical data sets. Progress towards better performances still remains possible. We have developed an iterative retrieval procedure based on a physical scattering and propagation model for observing the ocean surface and the intervening atmosphere. A correction for scattering by the roughened sea surface is proposed and introduced in a previouslydeveloped contracted form of the radiative transfer equation. This correction is modelled for a range of frequencies from 5 to 40GHz, and represented in the form of a polynomial expansion depending on two parameters only: the total atmospheric attenuation, and the wind friction velocity. Results of inversions on simulated measurements obtained with this approximate model are presented and discussed.