Spatial And Temporal Characteristics Of Rainfallerosionin Qilian Mountains And Scenario Prediction

Rainfall erosion refers to the potential capacity of soil erosion triggered by rainfall reaching a certain magnitude.China is one of the countries with the most serious soil erosion,and the land degradation and other disasters caused by soil erosion have caused incalculable losses to our ecological environment and economic and social development.Relevant research shows that soil erosion is mainly caused by four kinds of effects:hydraulic、wind,、freeze-thaw and gravity,among which,soil erosion caused by hydraulic effects is the most significant in China,and at the same time,relevant research shows that the main cause of hydraulic erosion is rainfall.The Qilian Mountains area is an important ecological security barrier in northwest China.In recent years,the soil erosion problem in the Qilian Mountains area has gradually become the focus of attention from community,due to climate change,over-exploitation and other factors.Therefore,studying the changes of rainfall erosion in the Qilian Mountains area under the background of climate change can help quantitative forecasting of soil erosion in the area and provide theoretical guidance for preventing soil erosion and improving ecological environment.This paper explores the interannual and seasonal spatial and temporal variations of rainfall erosion in the Qilian Mountains region of different magnitudes and their atmospheric circulation influences by using daily rainfall models,Fourier power spectra,sliding T mutation tests,and multi-model averaging using daily rainfall data from 13 meteorological stations in the Qilian Mountains region from 1960-2017.Meanwhile,33 climate models were used to predict the changes of rainfall erosion under SSP119 and SSP585 scenarios.The main conclusions are as follows.(1)In the past 58 a,the average annual rainfall erosion,medium and heavy rainfall erosion in Qilian Mountain area have shown an increasing trend,among which,the average annual rainfall erosion has the most obvious increasing trend but the rainstorm erosion has a decreasing trend.Medium and heavy rainfall erosion force occur in spring,summer and autumn,rainstorm erosion only occurs in summer.Medium rainfall erosion has an increasing trend in all seasons,heavy rainfall erosion force has an increasing trend in spring and autumn.The heavy rainfall erosion increases in spring and autumn,and decreases in summer.On the whole,the rainfall erosion was the largest in summer,the second largest in autumn and the smallest in spring,and the medium and heavy rainfall erosion was the fastest in spring,the second largest in autumn and the slowest in summer.(2)In terms of spatial variation,the annual average rainfall erosion,medium rainfall and heavy rainfall erosion as a whole gradually decrease from east to west.The spatial distribution of medium and heavy rainfall erosion in spring is basically consistent with the rainfall,with high values in the east and low values in the west,decreasing from east to west.The spatial variation of medium and heavy rainfall erosion in summer is basically the same,with an overall decreasing trend from east to west,but the heavy rainfall erosion in Qilian Mountains in the west of summer is relatively high.No significant spatial variation in rainstorm erosion.The medium and heavy rainfall decreases from east to west in autumn.(3)The mutation analysis showed that the rainfall erosion in the Qilian Mountains area changed abruptly in 1996,the spring and summer rainfall erosion changed abruptly in 1997,and the autumn rainfall erosion force changed abruptly later,in 2010.The rainfall erosion in the study area is mainly characterized by short cycles.The annual average rainfall erosion spring and autumn rainfall erosion force have cycles of 4.3a、4a and 3.8a,、respectively,and the summer rainfall erosion has cycles of 7.2a and 11.6a,indicating that the rainfall force in the Qilian Mountains is mainly influenced by the atmospheric circulation and El Ni(?)o.(4)The analysis of the factors influencing rainfall erosion shows that the WSHII,the WPSHNI,and the WCI are the main circulation factors affecting the rainfall erosion in the Qilian Mountains region.Meanwhile,the increase of precipitation water and erosive rainfall in the Qilian Mountains region are also the main influencing factors of erosion.(5)The CMIP6 climate model analysis shows that the rainfall erosion under different emission scenarios will increase in the next 33 a,and the SSP585 rainfall erosion scenario will increase more significantly.Under the SSP585 scenario,the rainfall erosion will increase significantly,and the increasing trend is slightly lower than that of the previous 58 a.The spatial distribution of rainfall erosion force is basically consistent with the SSP119 scenario,and the eastern region will be the region with the highest increase in rainfall erosion.In terms of seasonal changes,rainfall erosion force will also occur in winter under both scenarios,with a later year of occurrence,around 2025.As for the spatial variation,the rainfall erosion force shows a decreasing trend from east to west in the four seasons.