宁夏季节性最大冻土深度的分布和变化特征

Distribution and Variation Characteristics of the Seasonal Maximum Permafrost Depth in Ningxia

利用宁夏全区23个冻土观测气象站资料及对应气象数据,运用线性倾向估计、M-K突变分析、Morlet小波分析等方法,采用自然邻近点插值法进行等值面推算,分析了宁夏最大冻土深度的分布状况及变化特征.结果表明,宁夏多年极端最大冻土深度为1～1.6m,多年平均最大冻土深度仅中部干旱带的兴仁、麻黄山和海原3个气象观测站在1m以上.近50a来,宁夏最大冻土深度呈逐年下降趋势.≥1m最大冻土深度出现频率20世纪以前呈依次降低趋势,但进入21世纪后又有增加趋势.分析了宁夏各地最大冻土深度年际变异系数介于13.5%～25.6%,说明对气候变化的响应比较敏感.通过周期分析说明多数站点在1968—1975年和1978—1985年间存在一个3a左右的周期.通过对典型代表站最大冻土深度与相关因子的相关性分析得出,影响灌区最大冻土深度的主要因素是日平均气温和日照时数;影响中南部山区的主要因素是日平均气温和日均地温.

Materials from 23 permafrost observation stations and corresponding meteorological data in Ningxia are used, and then the linear tendency estimate, M-K mutation analysis, wavelet analysis method of Morlet, natural adjacent point interpolation method are used, to analyze the distribution of the maximum permafrost depth and its variation characteristics. The results show that the extreme permafrost depth is between 1 and 1.6 meters, and the average maximum permafrost depth is more than 1 meter only in Xingren, Mahuang mountain and Haiyuan located in the drought middle zone in Ningxia. The maximum permafrost depth reduces year by year over the past 50 years. The appearing frequency of the maximum permafrost depth greater than and equal to 1 meter reduces orderly before the 20th century, and which increases after the 21st century. The interannual variable coefficient of the maximum permafrost depth is between 13.5% and 25. 6% in Ningxia, which means it is more sensitive to climate change. In addition, it shows that most regions in Ningxia occurred the means mutations by using the M-K mutation analysis during 1979 to 1986, and most of sites have a about three years^eycle in 1968 to 1975 and 1978 to 1985 by using the cyclical analysis. It can be concluded that the first factor which affects the maximum permafrost depth in irrigation district is the average temperature, and the second is the sunshine hours, while in the southern of Ningxia the first factor is also the average temperature, but the second is the average daily temperature.