Study On The Correlation Between Drought And Snow Disaster And Monsoon Circulation On The Qinghai-tibet Plateau

The impact of climate change on natural and social systems is strongest and most comprehensive.Since 1950,great changes have taken place in extreme weather and climate events around the world,especially drought,flood and snow disasters.The Qinghai-Tibet Plateau is known as China's "start area" of climate change and global climate change "driver and amplifier".Due to the complexity of terrain features and surface physical properties,it is highly susceptible to disturbance of external factors,and the change of micro climatic elements will cause drastic change in the overall pattern.Therefore,it is characterized by high sensitivity and vulnerability.In recent years,with the change of global climate,the sensitive body of the Qinghai-Tibet Plateau has been particularly prominent in its response to drought,snow disaster and flood disaster,among which the drought and snow disaster seriously threatened the sustainable development of agriculture and animal husbandry on the plateau.Regional climate change and extreme weather events are closely related to the atmospheric circulation system.The Qinghai-Tibet Plateau climate system is relatively complex,mainly affected by circulation systems such as west wind,east Asian monsoons and south Asian monsoons.Based on the 213 counties of 6 provinces(area)on the Qinghai-Tibet Plateau as the research object,using the drought disasters and snow disaster in the history of the data,combined with the monsoon circulation index data,analysis the spatial and temporal variations of drought and snow of the Qinghai-tibet Plateau,and explore the seasonal and spatial agglomeration of drought and snow disaster in time and space.Combined with atmospheric circulation index,the correlation analysis method was used to discuss the correlation between drought and snow disaster and atmospheric circulation,so as to clarify the circulation background of the occurrence of drought and snow disaster on the Qinghai-Tibet Plateau.The following conclusions are obtained:(1)There are drought and snow disasters in Qinghai-Tibet Plateau all the year.Spring is a season with high incidence of drought and snow disasters.Drought mainly occurred in spring and summer,and the growth rate was also fast.The occurrence rate of drought was 42.94% and 41.76%,respectively.The fastest growth rate of drought was 11.91 times/10 a and 9.43 times/10 a,respectively.Snow disasters are mainly concentrated in spring and winter,and the frequency ratio of snow disasters in spring and winter is 42.11% and 41.18%,respectively.The rate of spring and winter snow disaster are 8.32 times/10 a and 10.26 times/10 a,respectively.The occurrence frequency of drought and snow disasters showed an increasing trend,and the total frequency increased rapidly with an increase rate of more than 25 times /10 a.(2)Drought and snow disasters occur in all counties on the Qinghai-tibet Plateau,and the length of the recurrence period is different in space.According to the spatial distribution of the repetition cycle of drought and snow disaster,drought mainly occurred in the surrounding areas of Qinghai-Tibet Plateau and was closely related to human activities.The snow disaster mainly concentrated on the southern Plateau of Qinghai and the southwest region of Tibet.In addition,some areas on the plateau are prone to drought in spring and summer and snow in winter and spring.(3)Due to the uneven distribution of precipitation seasons,drought and snow disasters will occur in a year.From 1950 to 2016,more than 2,580 counties in the Qinghai-Tibet Plateau experienced both drought and snow disasters in the same year,with the annual change showing an upward trend with an increase rate of 18.4 times/10 a.More and more counties experienced both disasters in the same year,with the combination of spring drought-winter snow and summer drought-winter snow being the most.The counties in which the drought and snow disaster occurred at the same time in the year were in the form of spatial aggregation distribution,mainly concentrated in the Southern Qinghai-Tibet Plateau,Qiangtang plateau,northern Tibet plateau,the south Tibet valley and parts of it and Hehuang valley,indicating that the annual precipitation distribution in these areas was extremely uneven.mainly in the southern plateau.(4)The hypothesis that there is a significant correlation between the occurrence of drought and snow disasters on the Qinghai-tibet Plateau and atmospheric circulation is established.The occurrence of drought and snow disasters on the Qinghai-tibet Plateau is comprehensively influenced by various monsoon circulation patterns,which show seasonal and regional differences.Plateau monsoon has,as a relatively independent circulation situation,an important impact on the plateau climate.There was a significant positive correlation between winter plateau monsoon and winter snow,spring snow and spring drought.While there was a negative correlation between summer plateau monsoon and spring drought,summer drought and spring snow,but none of them passed the significance test.(5)The northern region of the Qinghai-tibet Plateau is affected by the westerly wind all year round.When the westerly wind is strong,the region is prone to drought,especially in spring and summer.In spring,the northeast part of the plateau will be affected by the westerly wind of the previous year,the East Asian Winter Wind,and the East Asian Summer Wind of this year.When the Westerly Wind is strong in the winter and the East Asian Winter Wind is weak in the East Asian Winter Wind,snow disasters will occur in this region.In the summer,the region is affected by the East Asian Summer Monsoon,which is prone to drought when the monsoon is weak.In the southern part of the plateau,when the South Asian Summer Monsoon is weak,it is prone to drought in spring and summer,and when the West wind is strong in winter,it is prone to snow disaster in spring.