The Effects of Stochastic Rainfall Clustering on Radar Measurements

Rjh Scientific Incorporated, El Cajon CA

Investigators

Abstract

The concentrations of raindrops and cloud droplets in the atmosphere may be regarded as random variables that fluctuate with time and location. Recent work by Jameson and Kostinski has shown that these concentrations have probability distributions that deviate from the theoretical Poisson law that applies to purely random distributions. The deviations are caused by the tendency of drops to concentrate in clumps or patches. This clustering of drops has implications for precipitation development and for the propagation of radiation through clouds and precipitation. The objectives of this research are (1) to continue studies on quantitative characterization of clustering; (2) to evaluate the effects of clustering on the scattering of radar waves by raindrops; (3) to determine the significance of these effects on the estimation of rainfall rate from radar measurements. The work will also attempt to determine whether clustering can account for significant Bragg-type scattering by clouds and precipitation in addition to the well-understood Mie or Rayleigh scattering. The approach is a combination of (1) analysis of data from various instruments that measure drop sizes and concentrations and (2) theoretical investigations building on the earlier work on the characterization of clustering.