The Change Characteristics Of Drought And Wet Conditions And Its Impact On Landslides Over East Asia In The Early 21st Century

Although the concentration of greenhouse gases has been rising,the increase in the global average surface atmosphere temperature has almost stagnated in the early 21 st century,and this special phenomenon is referred to by academics as "warming hiatus".The current research mainly focuses on the explanation of the causes of the warming hiatus,and there is still a lack of research on a series of changes in the ecological environment caused by the warming slowdown.The fragile ecological environment in East Asia is very sensitive to climate change.During the period of warming hiatus,there has been significant cooling in East Asia.This cooling will bring uncertainty to the long-term drying trend in East Asia,which may change the risk of landslide disasters,threatening the lives and property of local people.In this paper,we study the changes in dry and wet conditions in East Asia in the early 21 st century by analyzing the changes in soil moisture,investigate the causes of change in soil moisture and explore the impact of the changes in dry and wet conditions on fatal landslides.The main conclusions are as follows:(1)Different from the previous continuous drying,the soil moisture in East Asia turned wet after mid-2000 s,and the drought was alleviated.Soil wetting mainly occurs in the northeast and southeast region of China where consist of drylands and humid region of 1.40?AI <1.80.Soil wetting in these areas is closely related to changes in precipitation and temperature.Through multivariate linear regression quantitative analysis,it is found that the soil wetting is mainly dominated by the increase in precipitation.The warming slowdown has strengthened the soil wetting on the basis of increase of precipitation,which caused the soil wetting not occurring simultaneously with warming hiatus.However,the temperature has a different degree of effect on the wet and dry changes in drylands and humid region.In drylands,the effect of slowing temperature on soil moisture is stronger than in humid region,and the interdecadal response of soil moisture is more sensitive in drylands.In the humid region,temperature has little effect on soil wetting.Soil moisture in drylands can effectively interrupt the positive feedback of drying-warming and reduce the risk of desertification.(2)Due to the characteristics of loess,the Loess Plateau has become a susceptible area for landslide disasters in China.With the wetting of East Asia in the early 21 st century,the risk of landslides in the Loess Plateau,which is a semi-arid region,is increasing.This paper uses the precipitation observation data of China from 2004 to 2016 and the collected landslide monitoring data to study the effect of the turning wet phenomenon on landslides on the Loess Plateau.The study found that during 2004-2016,along with the wetting in East Asia,precipitation over the Loess Plateau showed an upward trend.At the same time,the fatal landslide events on the Loess Plateau also increased,with a growth rate of 0.6 times per year.The analysis of extreme precipitation events and continuous precipitation events separately shows that although the temporal and spatial variation between extreme precipitation and fatal landslide events is similar.In addition,the continuous precipitation event with a duration of 8-9 days and a total precipitation of more than 120 mm has the most closely relation with the time series of the fatal landslide event on the Loess Plateau.The correlation coefficient of them is 0.87,and it is closely related to the occurrence of fatal landslide events in the Loess Plateau in 2013.