Modelling of thunderstorm outflows by means of the evolutionary power spectral density

This study proposes a model of time-modulating function for the evolutionary power spectral density (EPSD) of thunderstorm outflows, based on the slowly-varying wind speed and standard deviation records extracted from a database of 137 10-minutes thunderstorm time-histories. The analyses have been carried out under the hypothesis that the residual turbulent fluctuations can be considered an uniformly modulated process. Three different models have been proposed and provided with parameters characteristic of both the thunderstorm event and the background wind. Said models have been adopted to fit the ensemble value and its variation with the standard deviation of the dimensionless functions of both the slow-varying mean velocity and standard deviation records. Successively the relations between parameters have been provided and the procedure for the derivation of the EPSD have been outlined. The aim is to adopt this model for the derivation of the dynamic response of structures to thunderstorms outflows.