Study On Rainstorm In Northwestern Mountainous Area Of Zhejiang

Zhejiang Province in china as coastal areas is located in mid-latitude,the mainly mountainous and hilly terrain of its northwest often suffered from the rainstorm,which caused severe economic losses and casualties in this region.In this paper,we made use of the precipitation data of Linan national basic meteorological station for nearly 52 years and 66 automatic meteorological stations in the mountainous areas of northwest Zhejiang to analyze the spatial and temporal distribution characteristics of rainstorm in the mountainous areas.The results showed that the rainfall in northwest Zhejiang was more in the southwest and northeast part and less in the east part as a whole,there were two rainstorm centers,one was the meiyu rainstorm center located in the Qingliang Peak to Darning Mountain area,and the other was the typhoon rainstorm center in the north of the Tianmu Mountain.MICAPS historical data and NCEP/NCAR reanalysis data was used to gather statistics about circulation situation and physical quantity characteristics of rainstorm process since 2000.We found that the low-level shear line and ground inverted trough in spring were the most important influencing systems to trigger rainstorm.The most common weather system configuration in June was the eastward movement of the upper-level trough,the shear or jet cooperation in the middle and lower layer,and the existence of inverted trough or low pressure on the ground.The rainstorm process in July was mainly affected by subtropical high and typhoon.The rainstorm weather process caused by typhoon in August increased significantly.Autumn rainstorms were mainly caused by autumn typhoons.Finally,typical typhoon cases are used to analyze the interaction between mountain areas and typhoon rain in Shiling area,the center of typhoon rain.The results showed that The topography of Shiling area in Tianmu Mountain was northeast-southwest Valley type.Affected by narrow tube effect and topographic uplift,when typhoon was located in the southeast part of Tianmu Mountains,northeast wind in Tianmu Mountain had the most obvious increase in precipitation.