Water Vapor Corrections for Radar Altimeter and Its Variability over the Indian Ocean

Abstract

Abstract A new regional relationship is derived for wet tropospheric range correction h for radar altimeter and precipitable water (W) over the Indian Ocean using ship observations for the period 1982–91. The W varied over the range of 20–80 mm, thus providing total variability expected over tropical oceans. A fifth-order polynomial between h and W gave an rms error of 2.3 mm when compared with h computed using direct relation. Model results have also been compared with an earlier relation over the Indian Ocean and with the global relation, and it has been found that the present model yields the lowest rms error in h values over the Indian Ocean. Comparisons with earlier models show a factor of 2 improvement in the accuracy of the correction over this region. The W values have also been derived using the NOAA High-Resolution Infrared Sounder data for the years 1980, 1981, and 1984. These monthly mean W (3-yr averaged) values have been used to study the variabilities in W. The Indian Ocean depicts large va...