上边界条件对多年冻土地温场数值模拟结果的影响分析

Influence of upper boundary conditions on simulated ground temperature field in permafrost regions

以玛多地区多年冻土为背景,建立多年冻土地温场的数值计算模型,以不同的方式考虑近60 a来的气温变化构成不同的上边界条件,通过模型计算分析不同上边界条件下的不同时期温度场、未来冻土退化特征.结果表明:在上边界条件中采用气象站实测近60 a波动温度值和采用近60 a平均恒定值时,浅层冻土地温差异明显,且越浅层地温与越近时间的上边界条件相关.预测未来100 a冻土地温变化趋势发现,相同升温速率和升温初始温度条件下,上边界采用实测60 a波动温度值对冻土退化过程影响较小;升温初始温度值提高到与趋势线衔接后,冻土退化起始时间从约第45年提前到约第20年;60 a实测温度和升温初始温度值均提高到与其初始温度场上边界条件衔接后,冻土退化起始时间从约第20年提前到约第15年;冻土退化从开始到完全退化经历时间为25 a左右.

In this article, a numerical model is established in the background of permafrost in Madoi. Using the model, the initial temperature field and degradation characteristics of permafrost under different upper boundary conditions are simulated. It is found that the ground temperature of shallow layer permafrost simulated by using a 60-year averaged temperature is obviously different from that by using observed temperature series, k is predicted that within the next 100 years, under the same heating rate and initial temperature conditions, the permafrost deg- radation process will be less influenced by whether using the 60-year measured temperature. When the initial heating temperature value improves and meets the trend-line, the starting time of permafrost degradation will be in advance from the 45th year to the 20th year. When the 60-year measured temperature and initial heating temperature both improves and meets the upper boundary of initial temperature field, the starting time of the degrada- tion will be in advance form the 20th year to about 15th year. Permafrost degradation will last about 25 years from the beginning of decay to disappear entirely under the series of boundary conditions.