Radar cross-section of Earth surfaces measured by spaceborne precipitation radar (TRMM PR)

Normalized radar cross section of Earth´s surfaces are investigated using surface reflectivity data measured by a spaceborne radar, the Precipitation Radar boarded on the Tropical Rainfall Measuring Mission (TRMM PR). Homogeneous surfaces larger than 220 km of the PR´s observation swath are selected for the investigation site, including rain forests, oceans, and some land areas. `Surface Sigma-O´ products of the TRMM PR are collected when it observes the sites over a month, in different seasons a year. From the collected data, mean and standard deviation are calculated in each observation angle bin corresponding to nadir to ±17° of the incidence angle. Surface sigma-0 of rain forests in Amazon (South America) and oceans show little variation in seasons and little dependence on incidence angles (except around the nadir) as expected. That suggests those kind of surfaces could be used to calibrate the radar or to validate its products as the authors can predict their `true´ reflectivities accurately beforehand