Spatio-Temporal Variation of Rainfall Erosivity of Different Magnitudes Based on the REOF Method——Take Chongqing as an Example
This study explored the spatio-temporal variation of rainfall erosivity in different zones of Chongqing,in order to provide a theoretical basis for more precise soil erosion control.The daily rainfall data of 31 meteorological stations in Chongqing from 1981 to 2020 were selected to analyze the spatio-tem-poral variation of rainfall erosivity of different magnitudes in each zone,with the method of R/S analysis,moving average,and MK trend test.The results indicate:① Rainfall erosivity can be divided into six geo-graphical zones(Ⅰ-Ⅵ)based on the method of Rotated Empirical Orthogonal Function(REOF).② The average annual rainfall erosivity is 5 784.04 MJ·mm·hm-2·h-1·a-1,with the order of reducing as heavy rain,rainstorm,moderate rain,downpour.③ Heavy rain erosivity played dominant role in zoneⅠ-Ⅲ and Ⅴ-Ⅵ,while rainstorm erosivity was dominate in zone Ⅳ.Moderate rain,heavy rain,and rain-storm erosivity of each zone were mainly distributed from May to September,while downpour erosivity mainly concentrated from J une to August.④ The yearly variation of rainfall erosivity of different magni-tudes in each zone was rising as moderate rain,heavy rain,rainstorm,downpour.The overall change trend of rainfall erosivity of same magnitude was not significant.The Hurst index showed a strong upward trend for moderate rain erosivity in zones Ⅰ and V,heavy rain in zone Ⅱ and V,and downpour in zoneⅠ and Ⅲ.⑤ The erosivity of moderate rain,heavy rain and downpour mainly concentrated in southeast and northeast,while the erosivity of rainstorm was dominant in west and central Chongqing.The rainfall erosivity of different magnitudes showed a decreasing trend from east to west.Youyang and Xiushan of zone Ⅰ,Kaizhou of Zone Ⅱ,Beibei and Tongliang of zone Ⅲ,Bishan and Yongchuan of zone Ⅳ,Wuxi and Yun-yang of Zone V,and Zhongxian of zone Ⅵ were the peak centers of the rainfall erosivity of different magnitudes.This study clarifies the main rainfall types,periods and areas with high possibility of soil erosion,dynamic monito-ring and protective measures are supposed to control regional soil erosion according to local conditions.
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