The relationship between total lightning and ice fluxes.

摘要

It is generally believed that a strong updraft in the mixed phase region of thunderstorms is required to produce lightning. This is the region where the non-inductive charging process is thought to generate most of the storm electrification. Analytic calculations, as well as model results predict that the total lightning frequency is roughly proportional to the product of the downward mass-flux of solid precipitation (graupel) and the upward mass-flux of small ice crystals. Thus far this hypothesis has not been tested observationally.; Herein we use dual polarimetric and dual Doppler radar observations in conjunction with total lightning data collected in northern Alabama and also in Colorado/Kansas during the STEPS and STERAO-A field campaigns. These data are utilized to investigate total lightning activity as a function of precipitation and non-precipitation ice masses, estimates of their mass fluxes and updraft characteristics for different storm types in different climate regions. A total of eleven storms, including ordinary single cell, multicell and supercell storms, were analyzed in the two different climate regions.; Time series of both precipitation ice mass and non-precipitation ice mass estimates above the melting level show a good relationship to total lightning activity for the eleven storms analyzed, and the correlation is particularly strong for severe storms. Furthermore, the relationships are relatively invariant between the two climate regions. The correlation coefficients exceed 0.9 and 0.8 respectively between precipitation ice and non-precipitation ice mass estimates and the mean total lightning amounts per radar volume time. Importantly, computing the product of the mass fluxes improves the correlation to total lightning activity, lending observational support to the flux hypothesis.