A new satellite retrieval method for precipitable water vapor over land and ocean

A fundamentally new method is presented for retrieving precipitable water vapor (PWV) using observations from the Advanced Microwave Scanning Radiometer for EOS (AMSR‐E) satellite instrument. Unlike all existing passive satellite methods, the new technique is applicable both day and night, over ocean and land surfaces, and with little sensitivity to clouds. The method relies on a simple but accurate parameterization for AMSR‐E polarization‐difference signals at 18.7 and 23.8 GHz. Over land, validation is based on comparisons with the SuomiNet network of ground‐based GPS receivers. With quality control measures applied, RMS retrieval errors over land are limited to approximately six mm with a linear correlation coefficient of 0.89. Differences with the operational AMSR‐E oceanic PWV product are typically less than two mm. Products based on the new method should prove valuable in weather and climate research.