Spatio-temporal Variation Of Hourly Rainfall Intensity And Its Affecting Factors Of Xinjiang In Summer Based On CMORPH-Gauge Merged Data

The distribution of meteorological stations is sparse and unevenly in Xinjiang,and high-precision temporal and spatial meteorological data are lacking,the high-resolution grid data sets can be an effective way to solve this problem.Based on the 0.1°×0.1° gridded hourly precipitation dataset merged from automatic weather stations in China and the Climate Precipitation Center Morphing(CMORPH)precipitation product,the five minute rainfall intensity under different probability,the credibility of gridded precipitation datasets in Xinjiang is evaluated,and the temporal and spatial distribution characteristics of summer rainfall intensity in Xinjiang are analyzed from the frequency,extreme value and contribution rate of hourly rainfall intensity at different levels,further combined with the NCEP/NCAR reanalysis grid data and data of meteorological stations to analyse the influencing factors of hourly rainfall intensity in Xinjiang.The main conclusions are as follows:(1)The spatial distribution of gridded rainfall intensity is similar to that of probability rainfall,but the precision of the former is higher and its distribution is fragmented,and it can reflect more detailed spatial information.This gridded datasets can make up for the defects of sparse site in Xinjiang.in addition,it can effectively combine the advantages of terrestrial observations with satellite inversion precipitation,resulting in higher data accuracy,better quality and reliability.(2)The interannual fluctuation of the hourly rainfall intensity varies significantly at different brackets in Xinjiang,the frequency of 0.1-1 mm/h is the hight,and the frequency of more than 4 mm/h is the least.The interannual fluctuation of extreme value of the rainfall intensity is significant in the other six areas except that it is relatively stable on the Tianshan Mountains.The spatial distribution of the frequency of the hourly rain intensity is closely related to the distribution of topography,the Tianshan Mountains as the boundary,the northern areas is more frequents than southern in Xinjiang,the western more than eastern,the mountainou areas have a high incidence of rainfall,with rainfall frequency twice more than that of the basin areas.The contribution of moderate-intensity precipitation is the largest in Xinjiang,followed by mild precipitation,while the contribution of heavy precipitation is small.(3)According to the time characteristics of the monthly change of the average rainfall intensity and frequency in different regions in Xinjiang,no matter in June,July or August,the average rainfall intensity of different partitions is small,but the frequency of rainfall varies greatly;In terms of the spatial distribution,regardless of each month or average,all areas show obvious differences.The northern parts of Tianshan Mountain is the falling area of high rainfall intensity,the southern parts of Xinjiang is the falling area of low rainfall intensity and the most widely distribution of high rainfall intensity is in July.(4)The average rainfall intensity at each moment in a day is greater than 0.4 mm/h in Xinjiang,the difference of average rain intensity is small between basin and mountain area.The diurnal variation characteristics of hourly rainfall intensity is different from the rainfall intensity and the extreme value in Xinjiang,its high value areas are distributed in mountains and basins,the spatial distribution of rain intensity is more dispersed in the morning and the first half of the night,the spatial distribution is more scattered in the afternoon and latter half of the night,and there are obvious differences in the distribution from east to west.The spatial distribution of rain strong day accumulation shows a distinct distribution difference between Northwest and Southeast,the distribution of the high rainfall intensity area is also wide in the afternoon and the first half of the night.In terms of the stability of hourly rainfall intensity in Xinjiang,the precipitation is more stable in the northern of Xinjiang,and the precipitation is easy to fluctuate in southern of Xinjiang,which will cause events.(5)Xinjiang is mainly controlled by the westerlies in summer,and its water vapor mainly comes from the Atlantic Ocean and the recirculating water vapor during transmission.During its heavy rains,the stronger north wind flow from West Siberia to Xinjiang,and the Low Level East Jet(LLEJ)from Inner Mongolia and the Hexi Corridor play an important role.In summer,the hourly rainfall intensity of all regions is positively temperature and relative humidity in Xinjiang,it shows that the rain intensity is increasing with the increase of temperature and relative humidity.Elevation and aspect are important topographical factors that affect the spatial distribution of precipitation in Xinjiang,in a certain range,the intensity of rain is increasing with the elevation of altitude,when it reaches a certain height,as the elevation rises,the rain intensity is decreasing;in different slope directions,the difference of precipitation is very large,such as the rainfall of the windward slope is greater than the leeward slope.The summer rainfall is also affected by various climate systems in Xinjiang,the Tibet Plateau,the Northern Hemisphere subtropical high and the Northern Hemisphere polar vortex have an inhibiting effect,but the Asian polar vortex has a promoting effect for precipitation of summer in Xinjiang.In addition,the rainfall of Xinjiang is also affected by SST,among them,the SST of Indian Ocean have a greater impact on rainfall changes in Xinjiang.