Quantification of Observed Electrical Effect on the Raindrop Size Distribution in Tropical Clouds

Abstract

In the backdrop of extensive laboratory and theoretical evidence of broadening of the drop size distribution (DSD) of raindrops in the presence of electric field, quantification of the same in observed tropical clouds is lacking. Here this is quantified using the DSD measured by a microrain radar at 2,400-, 1,200-, and 600-m heights from the surface in six strongly electrified and six weakly electrified stratiform rain events together with the DSD of raindrops at the surface measured by a disdrometer for the same cases. The presence/absence of lightning is used to distinguish between strongly and weakly electrified events. The vertical profile of Median Volume Diameter below the melting layer and DSDs at all three heights for strongly electrified events and weakly electrified events are significantly different from each other, consistent with previous laboratory and numerical studies (Rayleigh, 1879; Davis, 1964; Moore et al., 1964, https://doi.org/10.1175/1520-0469(1964)021<0646:GORAMA>2.0.CO;2). Our results indicate that the electric field and surface charge of raindrops can affect the collision-coalescence process and breakup characteristics of raindrops. Our study suggests that the parameterization of electrical processes in weather/climate models can possibly improve the simulation of tropical rainfall in numerical models as well as a proper representation of DSD will improve the estimation of tropical rainfall in airborne measurements.