Analysis of Surface Cross-Sectional Data Taken During the 90° Yaw Experiment of the TRMM Precipitation Radar

During the descent of the Tropical Rainfall Measuring Mission satellite at the end of its mission, three types of special experiments were conducted; wide swath, 90° yaw (90Y: along-track scanning), and dense sampling. In this article, the results from the analysis of 90° yaw experimental data are shown in terms of a normalized radar cross section (NRCS) of the surface. The advantage of the 90Y experiment is that obtaining the incident angle dependency of the NRCS enables deduction of the conditions at the surface, especially over the ocean. The slope and intercept are calculated from the NRCS-incident angle plot except for angles near nadir. The slope correlates well with the sea-surface wind speed and therefore the rain attenuation can be estimated from the intercept and compared with the attenuation estimated from the radar reflectivity factor of the rain profile. The effect of the rain drops striking the sea surface is also examined by comparing the wind speed-slope relationship.