Oceanic Rain and other Collaborations with Al Chang

Tom Wilheit
Dept of Atmospheric Science
Texas A&M University
College Station, TX 77843-3150

The Nimbus-5 satellite, carrying the Electrically Scanned Microwave Radiometer (ESMR) was launched in December of 1972. Oceanic rain features were very obvious in the initial images. The brightness temperatures that were observed in these features could not be accounted for with realistic values of wind speed, water vapor and non-precipitating cloud; rain-sized drops were necessary. Ed. Rodgers had put rain rates from the Miami radar together with ESMR data and showed a reasonably quantitative relationship between the two. However, arriving at a quantitatively reasonable theory was proving difficult. Al and I could write down the equations but it wasn’t clear how to solve them. He then came across a program that solved a similar problem in the short wave portion of the spectrum. He was able to modify that program so that we could integrate the equation of radiative transfer in the presence of scattering. This work served as the basis for the Tropical Rainfall Measurement Mission (TRMM), an outstanding success that is still churning out data. Al was also able to modify the theory to understand the passive microwave remote sensing of snow and has provided the basis for the snow cover product from AMSR-E on Aqua.