One-Dimensional Variational Retrieval of the Wet Tropospheric Correction for Altimetry in Coastal Regions

The altimeter range is corrected for tropospheric humidity by means of microwave radiometer measurements (Envisat/MWR, Jason-1/JMR, Jason-2/AMR). Over an open ocean, the altimeter/radiometer combination is satisfactory. However, in coastal areas, radiometer measurements are contaminated by the surrounding land surfaces, and the humidity retrieval method is not appropriate anymore. In this paper, a variational assimilation technique is proposed to retrieve the wet tropospheric correction near coasts. The method is first developed on simulations using the data from a meteorological model. A performance assessment is performed, as well as a comparison with a standard algorithm. The method is then applied on actual measurements, thus evaluating its feasibility.