祁连山北麓春季冻土深度对气温变化的响应

Response of Frozen Soil Depth to the Variation of Air Temperature in North Piedmont of the Qilian Mountains in Spring

利用1961-2004年祁连山北麓11个站点的春季季节性冻土资料和9个站点的月平均气温资料,分析祁连山北麓冻土深度的空间和时间变化规律,并分析冻土深度对气温变化的响应特征。结果表明：祁连山北麓春季冻土以祁连站为最大值,向高纬度和高经度方向逐渐减小,武威附近为春季冻土最小值,靠近东南方向的乌鞘岭站出现次大值区域,冻土的空间分布特征与海拔高度关系密切;春季多年平均冻土深度为53.5 cm,年际最大值与最小值深度差为73.2 cm,随年际变化总体呈明显的减小趋势,其变化倾向率为11.3 cm/10 a,年代际变化呈阶梯状逐渐减小,20世纪90年代比80年代减小近20 cm;春季冻土深度减小主要受1～2月和春季平均气温升高的影响,特别是2月份气温每升高1℃,冻土深度减小7.05 cm;冻土深度大的地区,对气温变化的响应越敏感;冻土深度小的地区,对气温变化的响应相对较小。

In this paper, the spatial and temporal change of frozen soil depth and its response to the change of air temperature in the north piedmont of the Qilian Mountains are analyzed using the seasonal frozen soil depth data measured by 11 meteorological stations in spring and the monthly air temperature data observed by 9 stations during the period of 1961 -2004. The results show that the frozen soil depth was the thickest at Qilian Meteorological Station, it reduced gradually with the increase of latitudes and longitudes and was the thinnest near Wuwei Meteorological Station, the second thickest frozen soil depth occurred at Wushaoling Meteorological Station, and the spatial distribution of frozen soil depth was closely related to the altitudes. The average frozen soil depth in spring was 53.5 cm, and the difference between the maximum and minimum depths was 73.2 cm. The frozen soil depth in the study area was decreased by 11.3 cm per decade, and the inter-decadal change was gradually decreased in a step way, especially in the 1990s. The reduction of frozen soil depth was mainly related to the temperature increase in January and February, especially in February, and the frozen soil depth was decreased by 7.05 cm whenever the monthly temperature in February was increased by 1 ℃. The response of frozen soil depth to the air temperature increase was more sensitive in the regions with thicker frozen soil depth than that in the regions with thinner frozen soil depth.