Research On The Climate Characteristics Of Tropical Cyclone Precipitation In China From 1960 To 2017

Based on the daily precipitation data of more than 2,000 meteorological stations from 1960to 2017 and the tropical cyclone(TC)best-track data of the China Meteorological Administration,the TC precipitation(TCP)was identified by the Objective Synoptic Analysis Technique(OSAT)and uses the separation results to study the basic climatic characteristics and climate change characteristics of tropical cyclone precipitation affecting China from 1960 to2017,and analyzes the causes of tropical cyclone precipitation climate change.From 1960 to 2017,there were 1020 TCs affecting China,including 514 landing TCs,and506 TCs that did not land but bring precipitation.The TCP in China is mainly concentrated from May to November,especially from July to September,and peaked in August.In space,the TCP in China shows a decreasing pattern from south to north and from southeast coast to northwest inland.The annual TCP in coastal areas accounts for more than 20%of the annual precipitation,and the maximum is in the southeast of Taiwan,which can reach more than 50%.The total amount of TCP in China showed a downward trend(1.3 km~3/year)from 1960 to2017.From the spatial distribution of TCP climate trends,China's TCP is mainly reduced,from south to north,showing a“reduction-increasing-decreasing”distribution,with the most significant reductions being in Guangdong and Hainan and increases being in East China,Fujian Coast and Taiwan.From the changes of TCP in different seasons,it showed a significant downward trend in both the peak period(July-September)and the non-prevalence period,but the decrease in the total amount of TCP was mainly due to the decrease in precipitation during the peak period.The number of TCP days showed a decreasing trend.The spatial distribution of TCP days and TCP trend were more consistent,from south to north,the“reduction-increase-reduction”distribution type,and the reduction center and the increase center also appeared respectively.South China and East China.The maximum intensity of the impact period is used as an indicator to define the intensity of TC,and the TC intensity is divided into three levels:weak TCs(tropical depression and below),medium-intensity TCs(tropical storms and strong tropical storms)and strong TCs(Typhoons,strong typhoons and super typhoons)are used to study the climatic characteristics of tropical cyclone precipitation at each level.The analysis shows that except for the strong TC frequency of double peaks of 8 and 9 months,the TC frequency of other grades and the precipitation of all grades of TC are all single peaks in August.From the perspective of the influence of TCs and the linear trend of volume TCP,strong tropical cyclones play a major role in the contribution of TCP and its changes.The change of TCP in China is mainly related to the change of TCP days.The change of TCP days depends on the variation of TC frequency affecting China.From 1960 to 2017,the frequency of TCs affecting China showed a downward trend,and there was a abrupt change in1995,which was reduced from the average of 18.9 in the previous period(P1:1960-1994)to15.6 in the latter period(P2:1995-2017).From the frequency of TC generation,TC affecting China are mainly concentrated in the region of 5-20°N,110-160°E.The P2 period is significantly reduced in the D region of 5-12.5°N and 137.5°-155°E compared to the P1 period.Among them,the increase of the thermal factor of sea temperature and the decrease of the dynamic factor of vorticity are not conducive to the formation of TC,and the change of sea temperature has the greatest contribution to the reduction of TC genesis potential index.From the perspective of the moving path,the southerly airflow in the southern part of the P2 period is weakened,which is not conducive to the movement of TCs to the south China region;The northerly airflow in the East China Sea is enhanced,and the easterly anomaly in the middle and lower reaches of the Yangtze River is opposite to the average westerly wind,which is conducive to the movement of TCs to the East China and Yangtze River basins,thus increasing the number of TCP days and increasing the TCP.