兰州马衔山多年冻土活动层厚度估算及影响因素分析

马衔山残存的多年冻土被誉为黄土高原地区多年冻土的"活化石".自1986年发现多年冻土存在至今,多年冻土发生了严重的退化,活动层厚度增大,面积由原来的0.16 km2减少到现在的0.134 km2.本文基于马衔山多年冻土区的实际监测资料分析了气温、地表温度和N系数随时间变化特征以及活动层温度、土壤含水量的时空特征.根据2010-2013年马衔山多年冻土区的日平均地表温度和土壤参数实测及实验室分析资料,利用X-G算法模拟了马衔山多年冻土的冻融过程,并模拟得到4年的活动层厚度均比实测值小,这可能与活动层底部较高的未冻水含量有关.然后进一步探讨了泥炭层和含水量对活动层厚度的影响,泥炭层越厚,其隔热作用越强,活动层厚度越小;反之,活动层厚度越大;含水量越高,土壤的容积热容量越大,活动层厚度越小;反之,活动层厚度越大.

Simulating the active layer depth and analyzing its influence factors in permafrost of the Mahan Mountain,Lanzhou

The remnants of permafrost in the Mahan Mountain is known as a“living fossil”in the Loess Plateau. Since it was found in 1986,permafrost has degraded heavily,including the activity layer depth increase,perma-frost area shrinkage from the original size of 0.16 km2 to approximately 0.134 km2 now.In this paper,the annual variation of air temperature,surface temperature,coefficient N and spatial-temporal characteristics of the active layer ground temperature,soil water content are analyzed.X-G algorithm is applied to simulate the freez-ing and thawing processes based on the daily mean ground surface temperature and soil thermal parameter,meas-ured and lab analyzed,from 2010 to 2013.Simulated active layer depth was smaller than that measured in the four years,which may have something to do with the higher unfrozen water at the bottom of the active layer. Afterwards,the influence of water content and peat layer on the active layer depth was further discussed.The thicker the peat layer,the stronger the heat insulating effect and the thinner the activity layer,and vice versa. Soil water content influences soil heat capacity,so the higher the soil water content,the thinner the activity layer,and vice versa.