Time Histories of Horizontal Wind Velocity of Moving Thunderstorms and Pheno menological Model

Abstract:

A moving thunderstorm downburst is a sort of non stationary flow field. In order to study the effects of inlet velocity, translational velocity of a storm, jet height, and the angle of downburst flow with the ground to the field, an experiment was conducted by an impinging jet device. A phenomenon model was proposed based on the experimental results. Under different parameters of downburst, this model is capable of obtaining various time histories of horizontal wind velocity. Finally, according to the different wind speed profiles, time histories of horizontal wind speed produced by combining vector summation method, were compared with those by phenomenological model. In the duration before the arrival of the downbursts, the comparison states a good agreement between them except the Holmes & Oliver model, whereas it is found that the phenomenological model proposed herein has a stronger capacity of characterizing the variation of horizontal wind velocity in the duration of the departure of the downbursts.

Key words:thunderstorm downbursts; un stationary wind field; time history of horizontal wind speed; empirical model