A Novel Near-Land Radiometer Wet Path-Delay Retrieval Algorithm: Application to the Jason-2/OSTM Advanced Microwave Radiometer

An algorithm is developed to retrieve wet tropospheric path delay (PD) near land from a satellite microwave radiometer to improve coastal altimetry studies. Microwave radiometers are included on ocean altimetry missions to retrieve the wet PD, but their performance has been optimized for retrievals in the open ocean. Near land, the radiometer footprint contains a mixture of radiometrically warm land and radiometrically cold ocean. Currently, the radiometer retrievals in the coastal region are flagged as invalid since large errors result when the open-ocean retrieval algorithm is applied to mixed land/ocean scenes. The PD retrieval algorithm developed in this paper is applicable to both open-ocean and mixed land-ocean scenes, thus enabling retrievals in the coastal zone. The performance of the algorithm is demonstrated with detailed simulations and application to measurements from the Advanced Microwave Radiometer on the Jason-2/Ocean Surface Topography Mission. The algorithm error is estimated to be less than 0.8 cm up to 15 km from land, less than 1.0 cm within 10 km from land, less than 1.2 cm within 5 km from land, and less than 1.5 cm up to the coastline.