Global Oceanic Precipitation from the MSU during 1979—91 and Comparisons to Other Climatologies

Abstract Oceanic precipitation is estimated on a 2.5° grid for the period 1979–1991 from Microwave Sounding Unit (MSU) channels 1, 2, and 3 data gathered by seven separate TIROS-N satellites. Precipitation is diagnosed when cloud water and rainwater-induced radiometric warming of the channel 1 brightness temperatures (Tb) exceeds a cumulative frequency distribution threshold of 15% after correction for airmass temperature determined from the channel 2 and 3 measurements. After intercalibration between satellites, the 13-year gridpoint field of average Tb warming is calibrated in precipitation units with data from five to ten years of globally distributed low-elevation island and coastal rain accumulation measurements from 132 gauges. The calibration involves a single scale factor, and has a dependence on air temperature that is estimated from an MSU climatology. Comparisons between the satellite and raingage measurements of the average annual cycle in monthly precipitation are presented for 75 raingage lo...