Study On Precipitation Resources And Dynamic Characteristics On The East And West Sides Of Liupan Mountain In Summe

Liupan Mountain is an important scientific experiment base of cloud-seeding in northwest China.In-depth research on precipitation resources,cloud cover characteristics and precipitation formation mechanism in this area is helpful to improve the development efficiency of precipitation resources in this area.Based on ERA5 reanalysis data,this paper analyzed the distribution characteristics of cloud water resources in Liupanshan area in the past 15 years,and combined with NCEP reanalysis data for backward trajectory clustering,analyzed the spatio-temporal variation characteristics of cloud cover under different transport paths.On this basis,the temporal and spatial variations of precipitable water,water vapor flux and unstable energy on the eastern and western slopes of Liupan Mountain in summer were analyzed by using the data of surface meteorological stations and microwave radiometers.Finally,combined with X-band dual-polarization radar cloud data,three typical cloud precipitation processes in summer over Lipan Mountain were diagnosed and analyzed by means of multi-data fusion analysis,physical quantity diagnosis and weather situation analysis.The main conclusions are as follows:（1）The total column water content and water vapor content in Liupan Mountain have obvious seasonal variation characteristics.The spatial distribution characteristics are higher in the east and lower in the west,and the spatial distribution trend is decreasing from southeast to northwest.The spatial distribution characteristics of cloud cover（high cloud cover,medium cloud cover and low cloud cover）in mountainous areas showed that the probability of occurrence was higher in the east and lower in the west,and the medium cloud cover contributed the most to the total cloud cover,accounting for 42%.Under the influence of warm and humid air transport in the southwest and southeast direction,the probability of total cloud cover in mountainous areas is high,both of which are more than 80%.Precipitation and precipitation probability in mountainous areas have obvious seasonal variation characteristics,and the spatial distribution characteristics are high in the east and low in the west.（2）Compared with July and September,20.3%and 23.1%more southerly warm and wet air transported in August,which resulted in the precipitation of Liupan Mountain in August being 2.1 and 4.7 times of that in July and September,respectively.Precipitation of different intensity and accumulated precipitation duration of each station were closely related to the topographic conditions such as altitude and slope of the station.In 1h and 3 months before precipitation,the precipable water vapor flux Q of eastern slope site was higher than that of western slope site by 0.7mm,and the unstable energy E_kof eastern slope site was higher than that of western slope site by 28.0%(14.19 g·m^-1·s^-1),28.2%(28.4 J·kg^-1).Precipitation is more likely to occur on the eastern slope than on the western slope.Except ES2 site,the higher the altitude of other sites,the higher the water vapor flux Q value.The instability energy E_kof west slope and east slope stations under precipitation condition is 18.24 J·kg^-1lower than that under non-precipitation condition,and the instability energy E_kof west slope mountainside stations is higher than that of other stations.（3）The circulation background of continuous precipitation process is"a trough and a ridge".The cold air flow in the northwest is provided by 500 h Pa,and good water vapor and convergence conditions are provided by the section of 700 h Pa and the southerly warm and wet air transport.W,Q and E_kall show higher values on the eastern slope,W is 1mm,Q is 22g·m^-1·s^-1and E_kis 22 J·kg^-1.The local circulation background of convectional cloud precipitation process was"a trough and a ridge"and cyclonic circulation in the northeast direction（N40°,E115°）.The 800 h Pa section was uplifted by topography,and W,Q and E_kshowed higher values on the eastern slope,with W of 3mm,Q of 23 g·m^-1·s^-1and E_kof 20J·kg^-1.The circulation background of the stratified mixed cloud precipitation process was"two trough and one ridge",W,Q and E_kshowed higher values on the eastern slope,W was1mm,Q was 8 g·m^-1·s^-1,E_kwas 28 J·kg^-1,and W and E_kshowed higher values on the eastern side.However,the water vapor flux at WS3 station reached 139 g·m^-1·s^-1,showing more abundant water vapor conditions.1h before precipitation,the radar echoes of the cloud presented a massive distribution,and the average combined reflectance of the cloud reached35dBz.The combined reflectance of the stratified mixed cloud was greater than 35dBz.The size of the precipitation particles was large,and the uniformity of the particle scale was poor,which was conducive to promoting the formation of the precipitation process.