青藏高原积雪和季节冻融层的突变特征及其对中国降水的影响

The Abrupt Changing Characteristics of Snow Cover and Seasonal Freezing-Thawing Layer in the Tibetan Plateau and Their Impact on Summer Precipitation in China

利用青藏高原气象台站观测的积雪和冻土资料,建立了高原积雪和季节冻融层1965—2004年的变化序列,通过滑动T平均、M-K检验、动力学分割算法(BG算法)等方法检验出高原积雪没有发生明显的突变过程,而高原季节冻融层在1987年前后有一次明显的突变,冻结深度减少比较显著.当高原积雪偏少时,华南和西南降水偏多,而当高原冻结较厚时,全国的降水几乎都偏少.通过计算高原积雪和季节冻融层与全国夏季降水的单因子相关和复相关发现,积雪和季节性冻土对中国夏季降水都有一定的可预测性,但是如果共同考虑两个因子的影响,则能够提高夏季降水预测的准确率.考虑两个因子的共同影响,有3个明显的相关带,分别是北部沿大兴安岭经太行山北部到陕北最后到河西走廊,中部在长江中下游地区,南部则是沿武夷山经南岭到云贵高原中部.

In this paper,the change series of snow cover and seasonal freezing-thawing layer from 1965 to 2004 in the Tibetan Plateau have been established by using the observation data of meteorological stations.The overlapping T average,M-K test and B-G algorithm have been used to test the abrupt change of snow cover and seasonal freezing-thawing layer in the Tibetan Plateau.The results show that no obvious abrupt change in snow cover can be seen,but an obvious abrupt change in seasonal freezing-thawing layer occurred in 1987,with a decreasing depth of about 15 cm.When the snow cover in the Tibetan Plateau is little,precipitation in South China and Southwest China is much.When the frozen soil is deep,precipitation in most China is little.Both the snow cover and the seasonal freezing-thawing layer in the Tibetan Plateau can be used to predict the summer precipitation in China.When the impact of snow cover and seasonal freezing-thawing layer is considered synchronously,the predictability of summer precipitation can advance very much.Considering the synchronous effects of the two factors,there are three significant correlation zones from north to south.The north zone extends from the Daxing＇an Mountains to the Hexi corridor through the northern Taihang Mountains and the northern Shaanxi province,the central zone is in the middle and lower reaches of Yangtze River,and the south zone is from Wuyi Mountain to Yunnan-Guizhou Plateau through Nanling Mountains.