Lightning and precipitation

Abstract

Lightning flashes and surface rainfall are two manifestations of thunderstorms, both consequences of physical processes in the cloud involving hydrometeors of different sizes and types. For several decades, observations using various techniques have shown the general trend for both activities to be tightly related and to quantify the relationship. In several regions of the world, rainfall produced by convective systems has been estimated from surface detection, from ground radar scans or from space observations, and the rate of lightning flashes generated by the same systems was determined in parallel using various detection systems. Among the parameters used to quantify the relationship between rainfall and lightning, the Rain-yield Per Flash (RPF) which is the rainfall volume or mass divided by the lightning frequency, has been estimated in different regions and in several convection regimes. The values obtained from many studies can range from less than 1 × 10 7 kg fl-1 in continental and arid regimes to about 3000 × 107 kg fl-1 in oceanic regime. The variation of the RPF has been attributed to various causes in the literature, according to the techniques of rainfall estimation, the region of the storm activity, the type and the phase of the storms involved, and the type of flash considered. Surface-detected rainfall can provide larger RPF values than rainfall detected at altitude because of evaporation. The RPF values are obviously lower when considering total lightning activity and higher when the storm systems cover an extended stratiform zone. A large difference is observed between oceanic and continental storms. The RPF is much larger in oceanic convective clouds, especially in warm pool. The main reason for this contrast is the weakness of the updrafts over the ocean compared to over the land. In ocean storms, the width and the height of the mixed-phase cloud region, where the non-inductive charging processes occur, are too small for the development of electrification. © Springer Science+Business Media B.V. 2009.