冻土温度状况研究方法和应用分析

Permafrost Temperature Regime: Study Method and Applied Analysis

分析讨论了冻土温度状况研究中相关问题,包括构成多年冻土层的岩性、含水量、结构和构造,决定多年冻土温度状况动态变化的地面温度与气温间的关系,地中热流,研究区域的确定以及取决于地层的岩性、含水量、结构和构造、容重的热量在地层内传播过程的热物理参数.在分析物理学、地学和气候学等学科研究结果的基础上,笔者认为:1)在研究冻土温度状况问题中,研究区域应根据所研究问题的时间尺度确定,由于多年冻土层内不同深度上的温度和热流(或温度梯度)随时间的不同影响深度也不同,研究数十年时间尺度的多年冻土温度状况问题,一般应取多年冻土下限处的地中热流(或温度梯度)作为问题的下边界条件;2)以气温积温(或气温)与地面温度积温(或地面温度)比值所定义的N系数不仅存在年变化、季节变化和日变化,并在求解时必须已知地面冻结(或融化)的持续时间,而在目前对于不同地面条件缺乏定量描述气温与地面温度间关系的实验基础.因此,在缺乏比较严格的地面条件定量描述的情况下,应用气温与地面温度之差描述二者间的关系可能更为简单;3)在青藏高原地区,由于不同区域地形、地面条件、地层岩性以及地中热流等存在着很大差异,因而,不同区域多年冻土的热状况也不同.所以,不能简单地以气温等值线进行多年冻土制图。

Some problems relevant to the permafrost temperature regime research were analyzed and discussed in this paper, including the lithology of permafrost, water content, configuration and structure, the relationship between surface temperature and air temperature, the heat flow under ground, the determination of research area and some parameters about the lithology, water content, configuration and structure. Based on the research result of some subjects such as analytical physics, geosciences and climatology, some conclusions were drawn as follows: Firstly, in the case of permafrost temperature regime research, the determination of study area should be based on the time scale of research. Because the influence of temperature and heat flow on permafrost in different depths changes with time, the heat flow of permafrost base should be used as the lower boundary condition to solve the problem of permafrost temperature regime. Secondly, Coefficient N, which reflects the relationship between surface temperature and air temperature, changes annually, seasonally and daily. The duration of ground freezing is essential to get the value of the coefficient. Therefore, it is simple to use the value of air temperature minus surface temperature to describe the relationship between them. Thirdly, on account of the diversity of terrain, surface condition, lithology of stratum and heat flow on the Tibetan Plateau, isotherm cannot be used to map permafrost as a single index, and it is unreasonable to forecast permafrost change in accordance with it.