Surface reference normalized radar cross section over land for the improvement of the TRMM PR algorithm

The Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) standard algorithm 2A21 produces the surface normalized radar cross section (NRCS) values under no rain conditions as functions of the incidence angle and surface physical parameters which affect surface scattering. These NRCS values are used as the reference values to calculate the path integrated attenuation (PIA) values in the surface reference technique (SRT) to perform the rain attenuation correction. This paper shows the relation between the land surface NRCS values and the three land surface physical parameters which are NDVI (Normalized Differential Vegetation Index), the surface roughness, and the soil moisture over the land for each of the incidence angles and tries to improve the methods to calculate surface reference NRCS values over the land.