Determination of precipitation rates and yields from lightning measurements

This paper is concerned with the determination of relationships between precipitation rates p and lightning flash-rates in thunderstorms. Previous calculations predicting that the lightning frequency f is proportional to the product of the downflux of solid precipitation p and the mass upflux I of ice crystals, have been extended in order to derive direct relationships between f and p. The form of the f/p relationship depends upon the dominant glaciation mechanism. If primary nucleation is dominant f is proportional to the first power of p, but if Hallett–Mossop nucleation prevails the exponent is roughly 1.5. In order to test these predictions adequately, significant additional field-data analysis is required. The estimated values of precipitation yield per lightning flash, Y, are 107 and 2×106 kg/flash, respectively. These predictions are in reasonable agreement with field data. Improved predictions of Y should further increase the reported important role of lightning data—when assimilated into mesoscale models—in improving the accuracy of quantitative precipitation forecasting and shortterm forecasts of flooding.