| In this paper,we use the daily precipitation data onto 114 stations over a long period of time of 1961 to 2014 and the general circulation data to study the overall characteristics of precipitation in Yunnan.Then divided the precipitation into general precipitation(<25mm of daily precipitation)and heavy precipitation(? 25 mm of daily precipitation),using of climate statistics method to analyze the spatial distribution and change characteristics of the two types of precipitation,and discuss the causes of general precipitation and heavy precipitation changes in Yunnan region.The main conclusions are summarized as follows:(1)Total precipitation and the rainy days showed a clear decreasing trend from 1961 to 2014.The spatial difference was evident as the precipitation decreased from south to north.The areas with the highest annual precipitation were in the south and west edges.The areas with the least annual precipitation were in high altitude areas as well as in the Hot Valley area.The spatial distribution of rainfall on rainy days is roughly the same as the precipitation,and the trend of change is that most areas are obviously decreasing.The rainy season(May-Oct)rains showed a significant decrease in most areas,and the rainy days of the rainy season reduced the days of rain.(2)The general precipitation decreases from south to north.The overall trend is to reduce the trend,the springs are getting wetter,the summers and autumns and winters are getting drier.The daily precipitation change trend of the general precipitation is relatively gentle,and the summer,autumn and winter seasons are obviously reduced.Among them,the summer has the largest decrease trend and the autumn has the fastest rate.The reduction in general precipitation(days)plays a major role in the decreasing trend of total precipitation(days).(3)The change trend of heavy rainfall in Yunnan is not synchronized,and the reduction is mainly in most parts of eastern and western Yunnan,while the increase is mainly in central and southern parts,and the spatial difference is obvious.The overall trend of heavy precipitation has changed more slowly,with obvious decadal changes.The ratio of heavy precipitation to total precipitation has increased significantly in the past 54 years.In general,since 1961,rainfall in Yunnan has changed to-1.78mm/(10a).(4)General precipitation accounts for 61.6% of the total precipitation;general precipitation days are 137.6 days,accounting for 92.3% of the total days of precipitation;general precipitation intensity is 4.9mm/d.The average annual precipitation of heavy precipitation is 420.2mm,the number of precipitation days is 10.5d,and the precipitation intensity is 39.94mm/d.(5)The possible causes of general precipitation changes are discussed in terms of circulation background and air-sea interactions.The summer and autumn's amount of general precipitation accounts for more than 75% of the total precipitation.The anomalies of general precipitation in summer and autumn dominate the general precipitation anomaly.There is an important relationship between the South Asian summer monsoon activity,the water vapor transport in the Bay of Bengal and the South China Sea,and the anomalies of the SST in the Indian Ocean and the tropical West Pacific,as well as general precipitation anomalies in the two seasons.Heavy precipitation anomaly may be related to the abnormal warming of the western Pacific SST.The warming of the SST may cause anomalous subtropical highs and may affect the precipitation in Yunnan.At the same time,one reason for the heavy precipitation is the stronger equatorial flow in the lower Somali region may also be responsible for the heavy precipitation. |
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