不同风场结构下贺兰山地形降水的理想数值试验OA北大核心CSTPCD

Topographic precipitation is one of the main types of precipitation in northwest China.It is therefore of great significance to achieve a deeper understanding of the mechanism of topographic precipitation formation to improve forecasting ability.In this study,the vertical distribution structure of different types of wind fields was constructed based on the high-altitude environmental parameters during 20 heavy rains around the eastern foot-hills of Helan Mountain,and the em_hill2d_x module of WRF model was used to conduct ideal numerical experi-ments on the influence of different types of wind field on precipitation distribution.The results show that:(1)The dry air flow of two different types of wind fields(with/without wind shear)on the windward slope of the moun-tain range has an uplift effect of terrain on the windward slope air flow.The leeward slope fluctuation showed dif-ferent characteristics;under the condition of single layer uniform flow,the leeward slope is mainly represented by a mountain wave propagating in the vertical direction.Under the wind field with low-level wind shear,the lee-ward side mainly reflects the characteristics of the dorsal wave,and the gravity wave has the characteristics of co-existing horizontal and vertical propagation.With the increase in low-level wind shear,the characteristics of the horizontal propagation of the dorsal wave become increasingly obvious.(2)The simulated precipitation under the condition of a single layer of uniform wet airflow is mainly located on the windward side,and the precipitation in-tensity is relatively weak on the leeward side under the influence of strong downhill wind.When the wind speed increases to more than 10 m·s-1,the large cloud water content area on the windward side converges to the top of the mountain,and the precipitation intensity increases significantly.In the presence of low-level wind shear flow moving over the mountains,the test result shows that both the windward and leeward side there is a strong rain-fall center,with a deep convective system on the leeward slope,and the precipitation on both sides increases with the increase in wind speed.(3)The simulation results under the condition of low-altitude east wind and high-alti-tude west wind show that the appearance of high-altitude west wind strengthens the updraft on the windward slope and is not conducive to the transport of water vapor downstream;the precipitation on the leeward side is sig-nificantly weakened;the precipitation is more concentrated near the upper reaches of the mountain peak;and the intensity also increases to a certain extent.This is one of the main reasons for the significant difference in precipi-tation characteristics between the two sides of the Helan Mountain.