A linear radar reflectivity-rainrate relationship for steady tropical rain

Abstract

For equilibrium distributions, the present paper shows that the mass concentration M and the radar reflectivity Z are proportional to the rainfall rate R, with Z = CZR, and that N, M, R and Z are mutually proportional. Calculation provided CZ = 742μm3 (mm h-1)-1, which is suggested to be a universal constant for steady tropical rain. Data from a tropical rain experiment confirmed equilibrium peaks at diameters of ~0.3 (estimate), 0.9 and 1.9mm. Due to basic deficiencies of the disdrometer only steady state events could be used to assess radar reflectivities. The four available cases of steady rain consist of 112 one-minute spectra, with different types and origins of rain (warm clouds, clouds containing ice particles, convective or stratiform clouds). As in the model, the radar reflectivity Z, as calculated from measured drop spectra, was found to be proportional to rainfall rate. -from Author