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Abstract:
The question of parameterizing lightning flash rates (LFR) in weather and climate models has been widely discussed over the past few decades. In view of the growing understanding of the links between the Earth’s climate system and lightning (as well as the global electric circuit), a realistic parameterization of LFR is important for both forecasting thunderstorms and modelling the Earth system.The first sufficiently successful parameterization of lightning by Price and Rind, proposed about three decades ago, linked LFR with the height of the convective cloud, but the exponent in the formula was significantly different for clouds over land and ocean. More recent LFR parameterizations employed thermohydrodynamic factors (convective available potential energy, precipitation, wind shear), cloud condensation nuclei and aerosols. It is interesting to note that some ideas in this direction are similar to those used in estimating contributions of electrified clouds to the ionospheric potential of the global electric circuit.Analysis shows that thermohydrodynamic factors alone are sufficient to achieve a rather good correlation of simulated and observed LFR distributions over land. At the same time over the oceans they yield a much poorer match between simulations and observations, suggesting that other factors (aerosols in particular) also play an important role in this case. Recent studies on the influence of aerosols on electrical processes in clouds give us hope that it will soon be possible to develop from first principles an LFR parameterization that would be suitable for both land and oceanic regions.
