Profiling of atmospheric water vapor from the SSM/T-2 radiometric measurements

Data acquired over a period of January-March 1993 from the Special Sensor Microwave/Temperature-2 (SSM/T-2) over the region of TOGA/COARE (Tropical Ocean Global Atmosphere/Coupled Ocean Atmosphere Response Experiment) mission in the western Pacific Ocean are used to retrieve water vapor profiles under both clear and cloudy conditions. The SSM/T-2 measures millimeter-wave radiation at the frequencies of 91, 150, 183.3±1, 183.3±3, 183.3±7 GHz. Large-area (bounded by 30°S to 30°N latitudes and 120°E to 180°E longitudes) water vapor fields at different altitude layers were derived from the SSM/T-2 measurements. These results showed the capability of SSM/T-2 in providing both temporal and spatial variations of layered precipitable water (300-500, 500-700, and 700-1000 mbar). The retrieved layered precipitable water (LPR) was found to compare favorably with that derived from a few rawsonde stations in the area. Total precipitable water (TPW) was also derived from the SSM/T-2 retrieval results and compared with that estimated from the SSM/I (Special Sensor Microwave/Imager) on board the same satellite. Generally, values of the SSM/T-2 retrieved TPW are slightly higher than those derived from the SSM/I. Factors that cause this slight bias are explored and discussed