Characteristics of Frozen Ground Climatic Change in Hulun Buir from 1985 to 2020
The climate revolution of frozen ground was researched,using the data of 15 national stations including ground temperature,lower boundary of the first permafrost and the maximum depth of frozen ground in Hulun Buir from 1985 to 2021.Simultaneously using R/S analysis and aperiodic cycle analysis,through analyzing Hurst parameter,fractal dimension and non-cycle average cycle length of the maximum depth of frozen ground,the memory period of the trend about meteorological elements such as the maximum depth of frozen ground were analyzed.The conclusions of the research were drawn as follow:(1)The average ground temperature at the depthes of 80 cm,40 cm and 0 cm all showed upward trends.The increasing trend of ground temperature at depth of 0 cm was the most significant,especially the minimum value of ground temperature at the depth of 0 cm increased more significantly.(2)The duration of freeze decreased slowly.The spatial distribution showed that the longest duration was in the north central mountainous areas with an altitude of more than 600 m,while the shortest duration in the southwest and southeast.(3)The frozen ground began to appear in the northern region in mid-July,expanded to the southwest and southeast from September to late October,and began to disappear from the southwest and southeast to the north from early May to late June of the next year.(4)The maximum depth of frozen ground showed a decreasing trend year by year.The abrupt change occurred in 1988.The shallowest of maximum depth of frozen ground was from July to September,while the deepest from February to April of the next year.From October to January of the next year,the maximum depth of frozen ground unceasingly deepened,while reduced from May to June.The maximum value of maximum depth of frozen ground appeared in the western southern region.(5)R/S analysis and aperiodic cycle analysis showed that the decreasing trend of the lower boundary duration of the first permafrost and the maximum depth of frozen ground would continue in the future,with the duration of 10 years and 8 years,respectively.The increasing trend of the average ground temperature at the depth of 0 cm,the average ground temperatures at the depths of 40cm and 80cm in the future would rise continuously for 12 years.
maximum depth of frozen groundR/S analysisaperiodic cycle analysisM-K mutation test
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