Analysis On Characteristics Of Typhoon-Induced Precipitation In Anhui Province

The flood season in the Yangtze River and Huai Rivers in Anhui Province generally begins in plum rains,and ends in typhoon-induced precipitation.As an important component of annual precipitation and flood season precipitation in Anhui Province,typhoon-induced precipitation is affected by geographical and topographical factors.Therefore,the paper divides Anhui into three regions,south of the Yangtze River,Yangtze-Huai River,and north of the Huai River,and analyze the characteristics of typhoon-induced precipitation,typhoon-induced precipitation and plum rain events,and the interaction mechanism between typhoon-induced precipitation and ENSO events.The main results are as follows:Typhoon-induced precipitation event was identified,at the same time,the characteristics of typhoon-induced precipitation such as annual precipitation and frequency of each station and region were extracted,and the temporal and spatial distribution of typhoon-induced precipitation characteristics in Anhui Province were analyzed.The results show that the inter annual and inter decadal differences of typhoon-induced precipitation are significant.In recent 60 years,the average annual typhoon-induced precipitation of Anhui Province was 165 mm,and the regions of south of the Yangtze River,the Yangtze-Huai River,and north of the Huai River were 216 mm,154 mm and 137 mm,respectively,displaying a gradually decreasing trend from the south to north in Anhui.The average annual typhoon-induced precipitation at 15 stations were 125-347 mm,and the average annual occurrence number of typhoon-induced precipitation were 3.2-4.7 at each station.The typhoon-induced precipitation in the period from July to September was 128 mm,accounting for 78% of the annual precipitation.There was more typhoon-induced precipitation in mountain area and less in plain area,as well more in windward slopes and less in leeward slopes.The characteristic indicators of the plum rains during the strong and weak years of typhoon-induced precipitation show different characteristics in the regions of south of the Yangtze River,the Yangtze-Huai River,and north of the Huai River.Compared with the 60-year average plum rain feature,during the strong typhoon-induced precipitation period,the average beginning of the plum rains period of the regions of south of the Yangtze River and the Yangtze-Huai River were 3 days and 2 days eariler,and the end of the plum rains period were 5 days and 4 days eariler,respectively.The lengths of the plum rains period were reduced by 2 days.The average annual amounts of plum rains was reduced by 49 mm,and the average annual amounts of plum rains of the latter was increased by 16 mm.The average beginning of the plum rains period and the end of the plum rains period of the region of north of the Huai River were postponed for 2 days,the lengths of plum rains period was unchanged,and the lengths of plum rains period increased by 27 mm.During the weak period of typhoon-induced precipitation,the average beginning of the plum rains period of the regions of south of the Yangtze River and the Yangtze-Huai River were 4 days and 1 day eariler,and the end of the plum rains period were postponed 6 days and 3 days,respectively.The lengths of the plum rains period were increased by 10 days and 4 days.The average annual amounts of plum rains were increased by 86 mm and 48 mm.The average beginning of the plum rains period and the end of the plum rains period of the region of north of the Huai River were 1 day and 2 days,the lengths of plum rains period was reduced by 1 day,and the lengths of plum rains period was reduced by 27 mm.There are differences in the occurrence number of typhoon-induced precipitation and typhoon-induced precipitation between the regions of south of the Yangtze River,the Yangtze-Huai River and north of the Huai River in the year of more plum rain and in the year of less plum rain from July to September.Compared with the 60-year average occurrence number of typhoon-induced precipitation and typhoon-induced precipitation from July to September,the average occurrence number of typhoon-induced precipitation and typhoon-induced precipitation in the region of south of the Yangtze River from July to September decreased by 1.1 times and 52 mm in the year of more plum rain,respectively and increase by 0.5 times and 12 mm in the year of less plum rain,respectively.The average occurrence number of typhoon-induced precipitation and typhoon-induced precipitation from July to September in the region of the Yangtze-Huai River decreased by 0.5 times and 13 mm respectively in the year of more plum rain,and decreased by 0.4 times and 32 mm in the year of less plum rain.The average occurrence number of typhoon-induced precipitation and typhoon-induced precipitation in the region of north of the Huai River from July to September increased by 0.8 times and 57 mm respectively in the year of more plum rain,and decreased by 0.2 times and 31 mm in the year of less plum rain.The annual occurrence number of typhoon-induced precipitation and annual typhoon-induced precipitation in three regions of south of the Yangtze River,the Yangtze-Huai River,and north of the Huai River in the year and the next year of the La Ni?a event are more than that in the year and the next year of the El Ni?o event in general.The annual occurrence number of typhoon-induced precipitation and annual typhoon-induced precipitation in each region were reduced by 0.1-0.6 times and 3-48 mm respectively in which the year and the next year of the El Ni?o event,less than their 60-year average.In the year of the La Ni?a event and the next year,the annual occurrence number of typhoon-induced precipitation in each region increased by 0.2 to 0.5 times than its 60-year average.The annual typhoon-induced precipitation in regions of the Yangtze-Huai River and north of the Huai River increased by 1-42 mm than its 60-year average of each region,The annual typhoon-induced precipitation in region of south of the Yangtze River was 20 mm less than its 60-year average in the year of the La Ni?a event.In the next year,the typhoon-induced precipitation was 58 mm more than its 60-year average.