Standard Deviation of Spatially Averaged Surface Cross Section Data From the TRMM Precipitation Radar

We investigate the spatial variability of the normalized radar cross section of the surface (NRCS or σ
⁰
) derived from measurements of the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) for the period from 1998 to 2009. The purpose of this letter is to understand the way in which the sample standard deviation (SSD) of the σ
⁰
data changes as a function of spatial resolution, incidence angle, and surface type (land/ocean). The results have implications regarding the accuracy by which the path-integrated attenuation (PIA) from precipitation can be inferred by the use of surface-scattering properties.