Simulation-Based Analysis of Dependence of the Mean Storm Height Measured by a Spaceborne Radar on Its Angle from the Nadir

Abstract

The Tropical Rainfall Measuring Mission (TRMM) is a joint project between the United States and Japan on rain measurement from space. The first spaceborne rain radar was carried aboard the TRMM satellite. To achieve a 200-km swath for its measurements, the TRMM radar scans between 17.0° and ?17.0° from the nadir using 49 angle bins. The volume of resolution of the radar is not oblique at the nadir, but it is oblique at an angle from the nadir. The TRMM radar measures the height of storms. Results calculated from actual TRMM data show that the mean storm heights, as measured at an angle from the nadir of ±17.0° are greater by about 1 km than those measured at the nadir. It can be explained qualitatively that the obliqueness of the resolution volume causes the storm height to be overestimated. Simulation-based analysis using ground-based radar data has explained quantitatively how the 1-km overestimation of mean storm heights measured at an angle from the nadir of ±17.0° is caused by the obliqueness of the resolution volume.