Sensitivity Analysis of Polarimetric Variables at a 5-cm Wavelength in Rain

Abstract

Sensitivity of 5-cm-wavelength polarimetric radar measurements to raindrop size and distribution is investigated. At this wavelength, resonance occurs for sizes larger than about 5 mm, and therefore several polarimetric variables exhibit nonmonotone dependence on the drop diameter. The resonance effect is examined for temperatures of 0°, 10°, 20°, and 30°C. Through use of truncated gamma distributions (parameterized as a function of rain rate from the Maritime Continent Thunderstorm Experiment), and truncated Marshall?Palmer distributions, the influence of the upper tail of the drop size distribution is brought out. This poorly documented region of sizes can have a significant effect on some polarimetric variables. These simulations are extended further to include estimates of rain rate from the reflectivity factor Z, the specific differential phase KDP, the combined use of KDP and differential reflectivity ZDR, and the combined use of Z and ZDR.