Abstract: A heavy precipitation process in the Hetao area of Inner Mongolia on 13 August 2022 was studied using radar,surface observations,sounding data and ERA5 reanalysis data in this paper.The results indicate that the precipitation was mainly caused by a quasi-static mesoscale convective system,which was characterized by the continuous formation of east-west linear convections in the south of the Yin Mountain and the movement to the northeast,resulting in long-lasting heavy precipitation in the Hetao area.The subtropical high extended westward to inland,forming a persistent southerly airflow in the southern Hetao area.This low-level water vapor could be continuously transported from the south or southeast channels to the Hetao area,forming a stable water vapor supply.The blocking effect of the Yin Mountains caused the water vapor to accumulate on the southern slopes of the mountain,leading to high convective available potential energy,which was conducive to the initiation and development of deep convection.Deflected by the trend of the Yin mountain,the easterly airflow turned to a northeasterly airflow.The convergence line formed by the northeasterly airflow and the southerly airflow provided uplifting for the initial convection.After the convection triggered,the northward diffusion of the cold pool was constrained by the mountains,which strengthened the cold pool and enhanced the cold pool to lift the southerly airflow with moisture,resulting in subsequent convections.Due to the stable water vapor transport of the southerly airflow,after the convection generated by the convergence in the southern mountain moving to the northeast,the warm and humid airflow could continue to be lifted by the cold pool,which is generated by the previous convection and trigger new convections,thereby generating the quasi-stationary organized mesoscale convective system and ultimately resulting in heavy rainfall.

Key words: Mesoscale convective system, Organizational mode, Back-building, Heavy precipitation, Mountain