Variation Characteristic Of Extreme Precipitation In Loess Plateau Of Gansu Province Region In Recent52Years

Extreme precipitation is an important part of extreme weather events, from thevarious reports of view, the threat of extreme precipitation events is very alarming. Inrecent decades, large-scale heavy rainfall activities around the world seems to begetting worse. The IPCC report claimed, based on climate model results show that, inthe cause of global warming due to greenhouse gas increases future, most of theprecipitation intensity has increased, and increased extreme precipitation magnitudebetter than average precipitation. Climate models forecast that the human impact willcause an increase in the number of extreme events, including extreme precipitation,and there is evidence to show that some areas of extreme precipitation has increasedin recent decades, and attracted a large number of flood the meteorological disastersbrought by extreme precipitation is not only affect the sustainable development of thenational economy, is more a threat to the safety of life and property of the people.Gansu Loess Plateau is an ecologically fragile zone. Landform types in the region iscomplex and diverse, serious soil erosion, soil erosion strongly into gullies,fragmented, belongs to the eastern Eurasia temperate warm and humid with acontinental monsoon climate, climate is a type of northwest arid and semi-arid climate,rain and heat in the same period, the average years precipitation below400mm,inter-annual and annual distribution is very uneven, frequent sandstorms, drought,heavy rains, floods and other disasters, climate change. Clarify the temporal variationof Gansu Loess Plateau in extreme precipitation events, will improve its predictiveability, provide the basis for disaster prevention and mitigation decisions. Studyextreme precipitation events, environmental and social harm caused, to some extentreduce extreme precipitation events is of great significance.Based on daily precipitation data provided by the National Weather ServiceGansu Loess Plateau Area32meteorological stations and four surrounding weatherstations from1960to2011, using the percentile method one site per year for eachseason of extreme threshold of extreme precipitation temporal and spatial variationcharacteristics analysis, the conclusions obtained in this study are as follows:(1) The interannual variability of the Gansu Loess Plateau in the past52years ofextreme precipitation vary. Overall, radiate downward trend; tended to decrease in frequency of extreme precipitation; annual extreme precipitation intensity upwardtrend in summer, tended to decrease in the other three seasons.(2)From the point of view of spatial distribution, space distribution of GansuLoess Plateau nearly52years extreme precipitation significant differences, LongdongLoess Plateau and Longxi Loess Plateau of extreme precipitation frequency andintensity are showing different distribution patterns.(3) Winter extreme precipitation and extreme precipitation was negativelycorrelated, spring, summer, autumn extreme precipitation and extreme precipitationwas positively correlated; extreme winter precipitation frequency and extremeprecipitation frequency was negatively correlated, spring, summer and autumnextreme precipitation frequency of extreme precipitation and annual frequency waspositively correlated negatively related; spring and winter extreme precipitationintensity and extreme precipitation intensity, summer and autumn extremeprecipitation intensity and extreme precipitation intensity was positively correlated.(4) In Gansu Loess Plateau near52years extreme precipitation frequency andintensity in different time sequence length cycle shocks, the most obvious shock cycleof about25years.(5) Extreme precipitation in the entire time series, only during the summer a realmutation; truly mutation frequency of extreme precipitation occurred in the year andthe summer of the whole time series; extreme precipitation intensity throughout thetime series of real mutations occurred in spring and winter.(6) R/S analysis results show: future trends in extreme precipitation in summerand in the past the opposite outside, the other three seasons of extreme precipitationtrends are consistent and in the past; years and each season the number of futurechanges in extreme precipitation frequency trends and consistent with the past; thefuture trends of the year and the season extreme precipitation intensity and past.