Assessment of the Use of Lightning Information in Satellite Infrared Rainfall Estimation

Abstract

In this paper, the combined use of cloud-to-ground lightning and satellite infrared (IR) data for rainfall estimation is investigated. Based on analysis of the correlation between satellite microwave and IR rainfall estimates and on the number of strikes in ‘‘contiguous’’ areas with lightning, where the contiguity is defined as a function of the distance between strikes, an empirical algorithm is developed for convective rainfall estimation. The rainfall in areas not associated with lightning is determined using a modified version of an existing IRbased rainfall estimation technique. The combined lightning and IR-based technique is evaluated based on 15 days of data in July 1997 provided by geostationary and polar-orbiting satellites and the National Lightning Detection Network. The general conclusion is that lightning data contain useful information for IR rainfall estimation. Results show a reduction of about 15% in the root-mean-square error of the estimates of rain volumes defined by convective areas associated with lightning. It is shown that the benefit of using lightning information extends to the whole rain domain, because the error caused by missing convective areas because of the absence of lightning is smaller than that caused by overestimating the convective rain areas because of cirrus that obscure underlying convective storms when only satellite IR data are used.