1985—2020年呼伦贝尔市冻土气候变化特征

利用1985—2021年呼伦贝尔市15个国家气象站各层地温、第一冻土层下限、最大冻土深度资料，研究呼伦贝尔市冻土气候演变特征，同时采用重标极差（R/S）和非周期循环分析，统计最大冻土深度等气象要素时间序列的Hurst指数、分维数和非周期循环的平均循环长度，分析最大冻土深度等气象要素变化趋势和记忆周期。研究表明：（1）0cm地温、40cm平均地温、80cm平均地温都呈现出增大趋势，且0cm地温增大趋势最显著，特别是0cm地温最小值增大更加明显。（2）冻结持续日数呈缓慢减小趋势，其中中部偏北海拔超过600 m山区持续时间最长，西南部和东南部地区持续时间最短。（3）7月中旬冻土在北部地区开始，9月开始到10月下旬向西南和东南地区扩展，次年5月上旬至6月下旬自西南和东南地区向北部地区开始消失。（4）最大冻土深度呈现逐年减小趋势，突变年份出现在1988年，最大冻土深度在7－9月最浅，次年2－4月最深，10月－次年1月是最大冻土深度不断加深的过程，5－6月是最大冻土深度显著减小的时段，其中最大冻土深度最大值出现在西部偏南地区。（5）R/S和非周期循环分析表明，冻结持续日数和最大冻土深度未来减小趋势仍将持续，持续时间分别为10 a和8 a；0cm地温、40cm平均地温、80cm平均地温未来增大趋势仍将持续，持续时间都为12 a。

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 statisting Hurst parameter H, 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 research were drawn as follow. (1) The average 80cm ground temperature, the average 40cm ground temperature and the average 0cm ground temperature all showed an upward trend.The increasing trend of 0cm ground temperature was the most significant, especially the minimum value of 0cm ground temperature 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 600m, while the shortest in the southwest and southeast. (3) The frozen ground began to appear in the northern region in mid-July, expand 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 mutation occurred in 1988.The shallowest of maximum depth of frozen ground was in July to September, while the deepest in February to April of the next year. During October to January of the next year, the maximum depth of frozen ground unceasingly deepened, while reduced during 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 will continue in the future, with the duration of 10 years and 8 years respectively. The increasing trend of the average 0cm ground temperature, the average 40cm ground temperature and 80cm ground temperature in the future will rise continuously for 12 years.