Characteristics Analysis Of Precipitation During Flood Season In Anhui Province

Anhui Province is located in the East Asia significant monsoon climate zone,bounded to the Huaihe River and Yangtze River,and located in the transition of warm temperate and subtropical monsoon climate zone with three landforms of plains,hills and mountains.The precipitation has obvious zonality regulation.Using the method of principal component analysis and system clustering,Anhui province is divided into several regions.Based on the results of precipitation zoning,this paper make a preliminary study on the time variation regulation of different levels of precipitation in each region and its contribution rate to the total precipitation using statistical methods such as sliding t-test,wavelet analysis technique and rescaled range analysis;and the response of precipitation during flood season to El Ni?o and La Ni?a events in each region is analyzed.The major research results show:(1)Based on the first three principal component of the contribution of 67.6% with the precipitation during flood season of 14 precipitation station in Anhui Province from 1957 to 2016,Anhui Province was divided into four rigions: the region north of the Huaihe River,the region near the Huaihe River,the region betweent the Huaihe River and the Yangtze River,and the region south of the Yangtze River.The mean annual precipitation during flood season of each region was 596.1 mm,617.0 mm,695.0 mm and 883.2 mm,the mean annual rainy days during flood season of each region were 48.7 d,51.8 d,58.5 d and 66.0 d.The precipitation and rainy days during flood season of the region north of the Huaihe River were less than the region near the Huaihe River,and less than the region betweent the Huaihe River and the Yangtze River,and less than the region south of the Yangtze River.(2)In recent 60 a,the time characteristic analysis of precipitation during flood season in each region was different.There was a non-significant decrease trend in the total precipitation during the flood season in the region north of the Huaihe River,and there was a non-significant increase trend in the region near the Huaihe River,and there was no mutation in other region,and the total precipitation during the flood season in the region between the Hauihe River and Yangtze River and the region south of the Yangtze River show a significant increase trend,and 1968 and 2007 respectively were the abrupt change point of annual precipitation during the flood season reduction.The current trend of precipitation during flood season of each region will retain in the future except the region near the Huaihe River.The precipitation during flood season in four regions had the periodic fluctuations of 10-14 a,4-6a and 20-22 a,in addition,there was a periodic fluctuation of 28 a in the region south of the Yangtze River.The time characteristics analysis of different grades of precipitation during flood season in each region were different.The region north of the Huaihe River: except for the moderate rainfall,other levels of precipitation had a downward trend;The light rainfall mutated in 1964,heavy rainfall mutated in 2007,all levels of rainfall had the periodic fluctuation of 10 a and 4a,and rainstorm had the periodic fluctuation of 18-22 a.The region near the Huaihe River: except the light and heavy rainfall,other levels of precipitation had an increasing trend.Heavy rainfall mutated in 2009,other levels of precipitation didn't mutate,all levels of precipitation had the periodic fluctuation of 18-22 a and 10-12 a,and other levels of precipitation have the periodic fluctuation of 4-6 a except the light rainfall.The region betweent the Huaihe River and the Yangtze River: there was a weak decline of light rainfall,and other levels of precipitation rise;heavy rainfall mutated in 1968,with no mutations in other levels of precipitation.All levels of precipitation had the periodic fluctuation of 18-22 a,10a and 4-6a,in addition,the light and moderate rainfall had the periodic fluctuation of 28 a.The region south of the Yangtze River: the precipitation during flood season had a significant increase trend.And the light rainfall and heavy rainfall had a weak reduction.The other levels of precipitation had an increase trend.And moderate rainfall and rainstorm had a mutation in 2007,and all levels of precipitation had the periodic fluctuation of 28-30 a and 10-14 a.And the light and heavy rainfall had the periodic fluctuation of 4-6a,the heavy rainfall and rainstorm had the periodic fluctuation of 22 a.And in the future,all levels of precipitation during flood season of each region in Anhui Province will maintain the current trend.The quantity and distribution of precipitation during flood season observe the regulation that light rainfall was less than moderate rainfall,less than heavy rainfall,less than rainstorm.The time characteristic analysis of the different grades of rainy days of heavy rain and rainstorm during flood season in each region was different.The two kinds of rainy days during flood season in various regions were consistent with the trend of weak increase trend.And in the future,the two kinds of rainy days during flood season of each region in Anhui Province will maintain the current increase trend.The rainy days of heavy rain in the region north of the Huaihe River mutated in 2007;the rainy days of heavy rain in the region near the Huaihe River mutated in 2009,and the rainy days of rainstorm mutated in 1972;the mutation of rainy days in the region between the Huaihe River and Yangtze River occurred in 1968;and there was no mutation on the rainy days of heavy rain and rainstorm in the region south of the Yangtze River.There was the periodic fluctuation of 10-14 a and 4-6a of rainy days of heavy rain and rainstorm in each region,and in addition,there was the periodic fluctuation of 18-22 a in rainy days of heavy rain and rainstorm during flood season in other regions except the rainy days of rainstorm in the region north of the Huaihe River.(3)The responses of precipitation during flood season of four regions in Anhui Province to the ENSO events were different.The precipitation during flood season was less in the following year of El Ni?o and more in the following year of La Ni?a in the region north of and near the Huaihe River from 1957 to 1992 and 2010 to 2016;the precipitation during flood season was more in the following year of El Ni?o and less in the following year of La Ni?a in the region north of and near the Huaihe River from 1993 to 2009.The precipitation during flood season was less in the following year of El Ni?o and more in the following year of La Ni?a in the region betweent the Huaihe River and the Yangtze River from 1957 to 1978 and 1988 to 1998;the precipitation during flood season was more in the following year of El Ni?o and less in the following year of La Ni?a in the region betweent the Huaihe River and the Yangtze River from 1979 to 1987 and 1999 to 2016.The precipitation during flood season was less in the following year of El Ni?o and more in the following year of La Ni?a in the region south of the Yangtze River from 1957 to 1961 and 1993 to 2009;and it was more in the following year of El Ni?o and less in the following year of La Ni?a in the region south of the Yangtze River from 1962 to 1992 and 2010 to 2016.The correlation of cumulative ONI(the Ocean Ni?o Index)value of El Ni?o and La Ni?a with the precipitation anomaly during flood season in the following year in four regions in Anhui Province was different.The cumulative ONI value of El Ni?o in the region north of Huaihe River was significantly negatively correlated with the precipitation anomaly during flood season in the following year,and the cumulative ONI value of La Ni?a was positively correlated with the precipitation anomaly during flood season in the following year.There was a non-significant correlation between the cumulative ONI value of El Ni?o in the region near the Huaihe River and the precipitation anomaly during flood season in the following year,but there was a significant positive correlation between the cumulative ONI value of La Ni?a in the region near the Huaihe River and the precipitation anomaly during flood season in the following year.The cumulative ONI value of El Ni?o in the region south of the Yangtze River was positively correlated with the precipitation anomaly during flood season in the following year,and the cumulative ONI value of La Ni?a was significantly negatively correlated with the precipitation anomaly during flood season in the following year.The cumulative ONI value of El Ni?o and La Ni?a in the region between the Huaihe River and Yangtze River had a weak positive correlation with the precipitation anomaly during flood season in the following year.