The sensitivity of millimeter and sub-millimeter frequencies to atmospheric temperature and water vapor variations

Abstract

In order to determine optimal sounding strategies for future high resolution passive microwave instruments from space a study of the potential sounding capabilities of all significant microwave oxygen and water vapor absorption lines in the frequency range from approximately 10 to 1000 GHz has been undertaken. The study uses a second-order statistical climatological model covering four seasons and three latitudinal zones: low (30/spl deg/S to 30/spl deg/N), middle (30/spl deg/ to 60/spl deg/) and high (60/spl deg/ to 90/spl deg/) latitudes, and a wide range of altitudes (up to /spl sim/70 km). The climatological model was developed using data from three sources: the UARS HALOE instrument, the TOVS Initial Guess Retrieval (TIGR) radiosonde set and the NOAA AMSU radiosonde set. Variations in the vertical sensitivities of brightness temperature due to statistical variations of water vapor and temperature with latitude and season around each line are considered and useful channel sets for geostationary microwave vertical sounding are suggested.