Time And Space Changing And Correlation Analysis Of High Mountain Asia's Snow And Frozen Soil Freeze-thaw Cycles

The response of High Mountain Asia that known as the the third pole in the warming climate has received increasing attention.Snow and frozen soils are important components of the cryosphere and they are particularly sensitive to climate change.In this study,High Mountain Asia was selected as the study area.Frozen soil freeze-thaw cycles and snow freeze-thaw cycles were selected as research objects.The passive microwave radiometer data SMMR and SSM/I were used as data sources,and the ground station monitored temperature data as auxiliary data.Firstly,1)using the decision tree algorithm and the time series threshold method to extract the freeze-thaw status of frozen soils and snow in High Mountain Asia.Secondly,2)based on this status information,a high-level freeze-thaw data set for Asian snow and frozen soils is formed.The accuracy was verified based on ground station temperature observation data.Endly,3)Using the data sets analyze space-time changes of snow and frozen soil freeze-thaw in High Mountian Asian.Focus on analyzing the inter-annual variation of the data sets and the changing trend of the long-term sequence.(1)During the period 1988-2008,the start of soil freezing in the High Mountian Asia was postponed by 31 days.In the eastern part of the study area,Qilian Mountain,Hengduan Mountain,Himalayas,and Kunlun Mountain,the freezing time of frozen soils is delayed.In the northern of the study area,the Tianshan Mountains and the Central Taklimakan Desert,the freezing time of frozen soils is ahead of schedule.The beginning of frozen soil melting started 29 days earlier.The freeze-frozen end time of the frozen soil in the vicinity of the Tianshan Mountains and the Himalayas ranges is earlier;the freezing time of frozen soils near the Qilian Mountains and Bayan Har Mountains is being postponed.The number of soil freezing days decreased by 24 days.The days of freezing in the west of the High Mountain Asia,the Himalayas,the Tianshan Mountains,and the Kunlun Mountain range have decreased;the number of days of freezing in the western part of the Tianshan Mountains has increased.(2)During the period from 1978 to 2016,the snow melting in the HighMountain Asia started 13 days earlier.The end of the snowmelt meltdown was delayed by 14 days.The number of melting days of melting snow has increased by 20 days.The area with the largest fluctuation is the seasonal snow area in the middle of the study area.In the northwestern part of the study area,Tianshan Mountains,the western part of Kunlun Mountains,Tanggula Mountain and Hengduan Mountain,the beginning of snow melting is ahead of schedule.The melting end time is delayed and the melting days are increasing.(3)During the period from 1988 to 2008,the snow and frozen soil melting of High Mountain Asia are all showed an increasing trend.Selecting point 1(43.5°N,80.5°E)in stable snow area and point 2(35°N,90°E)in non-stable snow area,the change rate of point 1 snow freeze-thaw is lower than point 2 frozen soil freeze-thaw.