By using a radiative transfer model for simulation of microwave brightness temperatures over land surface

the effects of canopy and roughness on passive microwave soil moisture retrieval results have been analyzed. In order to reduce the influence of atmosphere

surface temperature

roughness and canopy

microwave polarization ratio of TRMM/TMI was employed and we got a good result when put the polarization ratio of TRMM/TMI into the use of surface flood area detection and classification. When practied our method over Dongting and Boyang lake area of China in the summer of 1998

the classification results of Radarsat SAR and L SAR surface flood area were used

and we got a Vol./Cal. over 75 0%. Low frequency channels of TRMM/TMI at 10GHz and 19GHz

were effectual in surface flood area detection and classification.