A Simulation Study Of Short-term Heavy Precipitation At The Foothills Of Mount Taihang

Due to the influence of southeast or eastward low-level jets,the Taihang Mountains are conducive to the emergence of two strong precipitation centers distributed along the topographic alignment near the mountains on the side of the plain.One is located near about37°N in the central Taihang Mountains and the other is located near about 35.5°N in the southern Taihang Mountains.Based on the hourly precipitation observation data of Chinese stations and the reanalysis,this paper provides insight into the role of complex topography in the development of short-term heavy rainfall in the central and southern Taihang Mountains under different weather backgrounds through actual and simulated analysis of two individual cases.The main conclusions are as follows:(1)The results also show that the convective clusters moved along the orientation of local topography,where the local slope are larger.The ‘5·22' heavy precipitation process was mainly influenced by two groups of convective monomer groups.The first group of convective monomer moved from northwest-southeast direction to northeast-southwest direction with the topography,and the second group of convective monomer moved downhill to near 400 m,and then continued to move southwest along the terrain.(2)The results show that a climatic topographic convergence zone is formed under the influence of solar radiation on the mountain-plain land surface.Then the cold front strengthened this topographic convergence zone and triggered the convective clusters from the convergence zone.(3)The intensity of convective clusters was closely related to the mountain-plains solenoid(MPS)on the east side of Taihang Mountains.Firstly,the low-level easterly anomaly of MPS coupled with the local terrain enhanced the uplift near the foot of Taihang Mountains.Secondly,the easterly flow intensified the water vapor transport from the eastern plain.The large amount of water vapor carried by the MPS-induced easterly wind was forced to ascend by topographic obstruction,and therefore the convective cells developed.(4)The trumpet-like topography in the southern Taihang Mountains serves to gather water vapor,accumulate energy,and increase the thickness of the Moist Absolutely Unstable Layer(MAUL),thus enhancing the intensity of precipitation.When the continuous easterly warm and humid jets reach the foot of the mountains,it will produce a continuous strong upward movement under the blocking and lifting effect of the topography.On the one hand,the upward motion will raise the height of MAUL,thus increasing the thickness of the wet layer over the local area;on the other hand,the MAUL remains stable for a long time,which is conducive to the triggering of convection and the repeated formation of convective monomers.