| The frontal precipitation of the monsoon rain belt is an important part of the summer precipitation in Anhui Province.With the North jump and stagnation of the subtropical high,the period of Anhui Province located in the monsoon rain belt is mainly divided into the plum rains period and the Huanghuai rainy season.During the Meiyu period,the precipitation in Anhui Province is mainly between the south of the Yangtze River and the Jianghuai river.During the Yellow Sea rainy season,the precipitation in Anhui Province is mainly in the north of the Huaihe River.According to the moving characteristics of the monsoon rain belt,Anhui Province was divided into three regions:the region of south of Yangtze River(Jiangnan),Yangtze-Huai River(Jianghuai)and the region of north of Huai River(Huaibei).The plum rains process from 1957 to 2016 in three regions of Anhui Province was identified by the subtropical ridge line position,temperature and rainy day.Then the time characteristics of plum rains in different regions were analysed.Z index was adopted to divide the subtropical ridge line position and the western ridge point during the period of Anhui Province.Characteristics of plum rains in different types of sub high were analysed.Z index was adopted to divide the precipitation level of Huaibei and Jiangnan during the plum rains period of Jiangnan and the rainy seasons in Huanghuai area.Preceding influencing factors were found by t distribution.The plum rains amount and its related data from 1957 to 2016 in three regions of Anhui Province were training samples,the plum rains amount from 2007 to2016 was the validation sample.The research results shows:(1)the average plum rains period of Jiangnan Jianghuai and Huaibei are June 16 through July 11,June 19 through July 11,June 25 through July 14 respectively.Correspondingly,the average precipitation of plum rains period over three sub-regions are 344.1,234.7 and 207.8 mm.There are respectively 7,5,and 4 years during the dual plum rains period over three sub-regions,and the void plum rains period are 5,6,and 9years.(2)There are differences in the decadal features,periodic and return period characteristics of plum rains in Jiangnan,Jianghuai and Huaibei of Anhui Province.The maximum value of plum rains in Jiangnan and Jianghuai was in the 1990 s,while the maximum value in Huaibei was in the beginning of 2000.The plum rains in Jiangnan shows a periodic fluctuation of about 4,10 and 21 years,the plum rains in Jianghuaishows a periodic fluctuation of about 6,9 and 17 years,and the plum rains in Huaibei shows a periodic fluctuation of about 6,13 and 18 years.The years that exceed a certain return period value in 60 years are also different.The maximum 3d precipitation of plum rains of Jiangnan in 1996 and 1999 exceeded the 20-year return period,and exceeded the 50-year return period.The maximum 5d precipitation of plum rains of Jiangnan in 1996,1999 and 2016 exceeded the 20-year return period,and the maximum5 d precipitation of plum rain in 1999 exceeded the 50-year return period.The maximum3 d precipitation of plum rains of Jianghuai in 1991 and 2003 exceeded the 20-year return period,the maximum 3d and 5d precipitation of plum rains of Jianghuai in 1991 and 2016 exceeded the 20-year return period,and the maximum 3d and 5d precipitation of plum rains of Jianghuai in 1991 exceeded the 50 year return period;the maximum 3d and 5d precipitation of plum rains of Huanbei in 1965,2000 and 2007 exceeded the20-year return period.In addition,in 1991,the maximum 3d precipitation of plum rains also exceeded the 20-year return period.The maximum 3d and 5d precipitation of plum rains of Huaibei did not exceed the 50-year return period.(3)During the period of plum rains in Anhui Province,when the subtropical high ridge line is more to the south,the precipitation of plum rains in Jiangnan is more to the mean value.When the subtropical high ridge line is more to the north,the precipitation of plum rains in Huaibei is more to the mean value.When the western ridge point extends westward,it is beneficial to the precipitation of three regions in Anhui Province,and when western ridge point extends eastward,it is unfavorable to the precipitation of three regions in Anhui Province.During the plum rains period of Jiangnan,the precipitation in Anhui Province can be divided into five types: the precipitation of Huaibei and Jiangnan is both normal(11.0%),abundant(7.2%)or scarce(20.0%),abundant in Jiangnan and scarce in Huaibei(34.5%),abundant in Huaibei and scarce in Jiangnan(27.3%).When the precipitation is normal in Jiangnan and Huaibei,the subtropical high ridge,subtropical high pressure intensity,subtropical high pressure area index and western ridge point index are closed to their average value.When the precipitation is abundant in two regions,or precipitation is abundant in Jiangnan and scarce in Huaibei,the position of subtropical high ridge line is southward.The high ridge line is northward when the precipitation is abundant in Huaibei and scarce in Jiangnan.When the precipitation of Huaibei and Jiangnan is both scarce,the subtropical high pressure intensity,area index are abnormally small,and the western ridge point are abnormally eastward.During the rainy season period of Huanghuai,the precipitation inAnhui Province can be divided into five types: the precipitation of Huaibei and Jiangnan is both normal(13.3%),abundant(11.7%)or scarce(15.0%),abundant in Jiangnan and scarce in Huaibei(26.7%),abundant in Huaibei and scarce in Jiangnan(33.3%).When the precipitation is normal in Jiangnan and Huaibei,the subtropical high ridge,subtropical high pressure intensity,subtropical high pressure area index and western ridge point index are closed to their average value.When the precipitation is abundant in two regions,or precipitation is abundant in Huaibei and scarce in Jiangnan,the subtropical high pressure intensity is abnormally large.When the precipitation is abundant in Jiangnan and scarce in Huaibei or is both scarce,the subtropical high pressure intensity is abnormally small.(4)Based on SPA-SF model,The prediction results of plum rains in Jiangnan from2007 to 2016 are good.The absolute value of the average relative error predicted by the model is 12.2% except 2012 and 2016.The prediction of plum rains in Jianghuai from2007 to 2016 are good,The absolute value of the average relative error predicted by the model is 13.8% except 2009,2012 and 2016.The prediction results of plum rains in Huaibei from 2007 to 2016 are not good,there are only 6 years of plum rains precipitation level in Huaibei area are correct. |
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