| The rainy climatic conditions in the Yangtze River Basin and the topographical conditions of the low hills have aggravated the ability of regional rainfall to erode the soil.Studying the extreme precipitation and rainfall erosivity in the Yangtze River Basin is conducive to the development of soil and water conservation work and the prevention and control of flood disasters.In this paper.based on the Zhang Wenbo daily rainfall model,based on the daily rainfall data of the long-term sequence of 127 meteorological stations in the Yangtze River Basin from 1960 to 2017,and using linear trend,space Kriging interpolation,Mann-Mendal mutation test,etc.To analysis of temporal and spatial variation characteristics of extreme precipitation and rainfall erosivity in the Yangtze River Basin during the past 58 years.Research indicates:(1)The annual rainfall in the Yangtze River Basin in 1960-2017 showed a slight downward trend.Among them,the annual rainfall in the upper reaches of the Yangtze River showed a slight decline,and the middle and lower reaches of the Yangtze River showed an upward change;the rainfall in the whole basin changed strongly after 2000.In space,the areas where annual rainfall shows a downward trend are mainly concentrated in the Sichuan Basin and Wujiang River Basin,and the areas showing an upward trend are mainly distributed in the lower reaches of the Yangtze River.The interannual variation of rainfall days in the upper reaches of the Yangtze River and the middle and lower reaches of the Yangtze River showed a significant downward trend.In the four seasons,the rainfall in the upper reaches of the Yangtze River showed a downward change.The rainfall in the middle and lower reaches of the Yangtze River increased in summer and winter,and decreased in spring and autumn.In the past 58 years,the annual average annual rainfall percentage of the erosive rainfall in the Yangtze River Basin was 69.62%,showing a significant increase trend.Among them,the medium rainfall accounted for a significant decrease in the annual rainfall percentage,and the heavy rainfall accounted for the increase in the annual rainfall percentage.The amount of heavy rainfall accounted for a significant increase in the percentage of annual rainfall.From 1960 to 2017,the erosive rainfall in the Yangtze River Basin increased at a rate of 3.79 mm/10a.The erosive rainfall-rich areas are mainly concentrated in the hilly and river junctions of the eastern plains of the Yangtze River Basin,and most of them are growing.Among them,the amount of moderate rainfall showed a downward trend,and the amount of heavy rainfall showed a downward trend in the upper reaches of the Yangtze River.The amount of heavy rainfall showed an upward trend in the middle and lower reaches of the Yangtze River.and storm rainfall showed an upward trend.In the spring and autumn,the annual average erosive rainfall showed a downward trend,and the annual average erosive rainfall in the summer and winter seasons showed an upward trend.(2)The extreme precipitation indicators of the Yangtze River Basin in 1960-2017 showed different trends.The annual precipitation intensity(SDII),the maximum precipitation on the 5th(R5day),the total amount of extreme precipitation(R99P),and the total number of abnormal precipitation(R95day)in the Yangtze River Basin showed an upward trend.Among them,the rising trend of SDll and R99P passed the significance test;the number of consecutive rainy days(CWD)showed a significant downward trend.There are three high-value centers with large increase in precipitation intensity in the basin.They are the plain in the middle and lower reaches of the Yangtze River,the upper reaches of the Hanjiang River,and the junction of the Jinsha River and the Yangtze River.The high-value areas with extreme precipitation are mainly distributed in low hilly areas,and the areas with rising R99P are also distributed in plain hilly areas;the area with a large decline in CWD is mainly concentrated in the upper reaches of the Yangtze River,especially in the karst landforms where the Wujiang River flows.(3)The average annual rainfall erosivity of the Yangtze River Basin in 1960-2017 is on the rise,and the larger uptrend is mainly distributed in the middle and lower reaches of the Yangtze River,parts of the Poyang Lake Basin,and the northeast of the Dongting Lake Basin;among them,the erosive force of the middle rain is declining,and the area with a large downward trend is mainly distributed around the Wuling Mountain in the Yangtze River Basin,the southwest mountainous area of Daba Mountain,the Sichuan Basin and the Dagu Mountain Area;heavy rain erosive force and storm rain erosive force showed an upward trend,and their rising trend is mainly distributed in the Poyang Lake basin,the middle reaches of the Yangtze River and the Dongting Lake.In the four seasons,the rainfall erosivity generated by heavy rain in spring in different areas of the Yangtze River Basin is the largest,and the rainfall erosivity generated by heavy rain in summer is the largest.The erosivity generated by different magnitudes of rainfall in autumn is roughly equivalent,and the erosive force generated by moderate rain in winter.Mainly.In spring and autumn,the annual average rainfall erosivity in the Yangtze River Basin is decreasing,and the annual rainfall erosivity is increasing in summer and winter.In the four seasons,the rainfall erosivity of different magnitudes showed an increasing trend in the south bank of the Yangtze River in the middle and lower reaches of the Yangtze River.The rainfall erosivity of different magnitudes in the mountainous areas such as Xuefeng Mountain,Wuling Mountain and Bawu Valley showed obvious fluctuations.(4)The extreme precipitation intensity index(SDII,R5day)and extreme precipitation relative index(R99P,R95P)in the Yangtze River Basin are significantly positively correlated with rainfall erosivity of different magnitudes,and have a weak positive effect with continuous rain days CWD.There was a significant negative correlation with the continuous rain-free days CDD. |
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