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应用中国境内845个气象台站的地表日最低温度资料,计算分析了近地表土壤冻结天数在1971—2000年的气候平均值;探讨了其空间的分布特征及其与冻土分布的关系;构建并分析了1956—2006年地表土壤冻结天数的时间序列及其与气侯变化的关系。结果表明,中国境内近地表土壤冻结天数的气候平均值随纬度增加、海拔升高而增加。青藏高原、新疆北部和东北地区北部多年平均冻结天数均超过200天。多年冻土区的边界与冻结天数(220±10)天的等值线高度吻合。按冻结天数大于15天为季节冻土区的定义,中国季节冻土的最南界约为25°N,22°N以南地区基本为非冻结区。自1956年以来,中国境内近地表土壤冻结天数呈显著的下降趋势,变化速率为-0.22 d/a,但20世纪90年代以后,其减少速率可达-1.02 d/a。近地表土壤冻结天数的变化与气温变化呈负相关关系,即随气温升高近地表土壤冻结天数减少。
Based on the minimum surface temperature data of 845 meteorological stations in China, the average climatic values of the near-surface soils frozen during 1971-2000 are calculated and analyzed. The spatial distribution of the soil surface and the relationship with the distribution of frozen soil are discussed. The time series of surface soil freezing days from 1956 to 2006 and its relationship with climate change were analyzed. The results show that the average climatic value of the freezing days of near-surface soils in China increases with latitude and elevation. The average number of frozen days in the Qinghai-Tibet Plateau, northern Xinjiang and northern part of Northeast China exceeded 200 days in average. The permafrost boundary is highly consistent with the contours of the frozen days (220 ± 10) days. According to the definition of seasonally frozen terrain with a freezing period of more than 15 days, the southern boundary of the seasonal frozen soil in China is about 25 ° N, and the area south of 22 ° N is basically a non-freezing area. Since 1956, the freezing days of near-surface soils in China have shown a significant downward trend with a rate of -0.22 d / a. However, after the 1990s, the rate of decrease reached -1.02 d / a. The change of freezing days of near-surface soil was negatively correlated with the change of temperature, that is, the number of frozen days of surface soil decreased with the increase of temperature.