Estimation of Convective Rainfall from Lightning Observations

Abstract

The objective of this study is to develop a technique to use lightning observations for estimating convective rainfall. A framework for rainfall estimation is developed in which key elements are 1) the rainfall–lightning ratio, that is, the convective rainfall mass per cloud-to-ground lightning flash; 2) the spatial distribution of rainfall relative to flash locations; and 3) the temporal distribution of rainfall relative to the time of lightning occurrence. These three elements are examined through a study of 22 summer thunderstorms in the domain covered by the Melbourne, Florida, WSR-88D radar during August of 1992 and 1993. The analyses are carried out by combining lightning observations from the National Lightning Detection Network with storm parameters computed from 3D reflectivity observations using the Thunderstorm Identification Tracking and Nowcasting storm-tracking and analysis algorithms. The effect of the prevailing convective regime on the variability of lightning–rainfall relationships is investigated. The rainfall estimation procedure is implemented and tested for a thunderstorm that occurred on 20 August 1992. Striking similarities in the spatial distribution of rainfall estimates are observed for the rainfall maps derived from lightning observations and those derived from WSR-88D reflectivity observations. Rainfall estimates derived from lightning observations are of potential use for short-term prediction of flash floods, especially in regions of poor radar coverage. Potential uses of this method also include correction of radar-estimated rainfall for range effects.