7. CALCULATIONS OF THE BIDIRECTIONAL REFLECTANCE DISTRIBUTION FUNCTION (BRDF) OF A PLANETARY SURFACE Snorre Stamnes Author： Affiliation： Stevens Institute of Technology Current passive microwave rain retrievals over land are known to contain large uncertainties. A major setback for over land rain retrieval is its reliance on ice scattering information. The relation between ice aloft has variable relations with rainfall at the surface. In some cases, problems arise since rainfall is not directly proportional to ice. By analyzing TRMM data and performing radiative transfer modeling, here we argue that a combination of TMI channels does contain liquid information. Additionally, it is found that land surface type and 2-meter air temperature have significant skills in characterizing rain cloud types. An effective use of such information can lead to significant improvement for land rain retrieval.