青藏高原季节性冻土年际变化的异常特征

The Feature of Seasonal Frozen Soil in Qinghai Tibet Plateau

对 1 961～ 1 999年 46个站点最大冻土深度的年际变化采用旋转主成份 ( REOF)分析 ,发现存在 4个变化敏感区 :青藏高原东北区 ,青藏高原东南区 ,柴达木盆地区 ,青藏高原南部区。4个变化异常敏感区的最大冻土深度随时间变化有不同的趋势。其中 ,进入 2 0世纪 90年代 ,高原东北部、高原东南部和高原南部区冻土厚度表现出变薄趋势 ,其代表站的最大冻土深度平均比 80年代变浅 0 .0 2、 0 .0 5、 0 .1 4m,反映了对气候变暖的响应 ,呈现出与全球气候增暖的趋势 ;柴达木盆地和高原中部则表现为与前 2个区域相反的变化趋势 ,即进入 2 0世纪 90年代 ,冻土深度有所增加。其代表站的最大冻土深度较之 80年代加厚 0 .5 7m。由于土壤质地和溶质的差异 ,4个敏感区最大冻土深度在高频段上具有不同的周期 :柴达木盆地和高原南部具有 2年的周期 ;在较低频段上 ,均表现为 1 4年左右的周期。

The seasonal frozen soil in the Qinghai Tibet Plateau has strong response to climate change, and it effects the climate change at the same time. In this paper, the frozen soil maximum depth of 46 stations covering 1961～1999 in the Qinghai Tibet Plateau are analyzed by rotated experience orthogonality function (REOF). The results show that there are 4 main frozen anomaly regions in the Qinghai Tibet Plateau, i.e., northeast Qinghai Tibet Plateau, southeast plateau, south plateau and Qaidam Basin pattern. The frozen soil depth annual anomaly in the above representative areas shows different change trends. But the main trend, except for the Qaidam Basin, has been in decrease since the 1980s, which shows climate warming. On the average, the maximum soil depth has decreased by about 0.02, 0.05, 0.14 m over northeast, southeast and south of the Qinghai Tibet Plateau, but increased by about 0.57 m over the Qaidam basin during the 1990s. It shows different responses to the above areas in climate system and the Qinghai Tibet Plateau has dynamical effects on atmospheric circulation. The spectral analysis shows: there are different variance cycles in high frequency in four areas, i.e., there is a cycle of about 2 year length in the Qaidam Basin and south of Qinghai Tibet Plateau; there is a cycle of about 14 year length over all the four areas in lower frequency. It shows different soil texture and solutes over the four areas.