Abstract:

Because of its unique geographic location and landform, Aksu Prefecture, located in the midwest of southern Xinjiang, is prone to gale weather when the surface cold air is forceful. For better knowledge of its mechanism, the fine characteristics and its effect system, and dynamic and thermal conditions of the rare gale over the Tianshan Mountains over Aksu Prefecture from August 15^th to 18^th, 2019 are assessed, based on conventional and intensive detecting, radiosonde observation, and the National Center for Environmental Prediction reanalysis data. The outcomes are as follows. This gale is known as a persistent gale. The blocking high over Eastern Europe has developed to strengthen against the circulation background, and the Central Asia low vortex has been maintained for a long time, with three short waves split and moving east. It is caused by movement energy converted from cold air potential energy when the upper-level jet stream and low-level cold advection work perfectly together. There are three gale waves, all of which are caused by cold air being guided over the Tianshan Mountains by the upper trough. The gale lasted only a few minutes for the first two times, triggered by a short-wave trough. The gale last time lasted for a long time, triggered by the main trough moving east. For the first time, the gale wave was composed of convective thunderstorm winds with instantaneous wind speeds reaching the grade 12. It benefits the strengthening and preservation of the strong vertical motion and secondary circulation caused by the high-level jet, middle-level convergence, and low-level divergence.

Key words: cross over mountain gale, thunderstorm wind, dynamic conditions, thermal conditions, Aksu Prefecture