The microwave radiometer (MWR) provides time-series measurements of column-integrated amounts of water vapor and liquid water. The instrument itself is a sensitive microwave receiver that detects the microwave emissions of the vapor and liquid water molecules in the atmosphere at two frequencies: 23.8 and 31.4 GHz.
Integrated water vapor and liquid water path are derived from radiance measurements with a statistical retrieval algorithm that uses monthly derived and location-dependent linear regression coefficients.