The Feature of Seasonal Frozen Soil in Qinghai Tibet Plateau

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.