青藏高原积雪异常与大气环流异常间关系分析

在参考前人对青藏高原积雪异常年的划分成果的基础上,初步确定出1957—2003年的典型积雪异常年。采用NCEP提供的全球144×73个格点1957—2003年前一年12月至当年5月100 hPa和500 hPa的月平均高度场资料,分析了青藏高原积雪异常与大气环流异常的相互关系,提出了大气环流异常影响青藏高原积雪异常可能的天气气候成因机制;应用三因子最优子集二级判别,建立了判别青藏高原积雪多雪年/少雪年的判别方程,作为客观、定量判断高原积雪异常的指标;结合初步确定的典型青藏高原积雪异常年,用得到的最优判别方程进行划分,并经反复论证后,确定出1957—2003年青藏高原积雪正常略多年和正常略少年。

The Relationship Between the Anomalous Snow Cover on the Qinghai-Tibetan Plateau and Atmospheric Anomalous Circulation

Based on the previous researches,the longer time series about the typically anomalous snow cover years from 1957 to 2003 are confirmed initially.Using NCEP data of global monthly mean geopotential height (144×73) at 100 hPa and 500 hPa,the relationship between anomalous snow cover and atmospheric anomalous circulation at the Qinghai-Tibetan Plateau is analyzed from December to next May of 1957 to 2003.And the possible mechanisms in which the atmospheric anomalous circulation affects the anomalous snow cover at the Qinghai-Tibetan Plateau are propounded.It is found that the atmospheric circulation affects the weather and climate and lead to the snow cover anomaly first,and the abnormal snow cover affects the atmospheric circulation in slighter extent subsequently.The atmospheric pressure of key tropical areas changes in an opposite phase to that of key areas in the middle and high latitudes of Southern Hemisphere.Meridional circulation of two hemispheres is strengthened by this strong meridional atmospheric pressure gradient.Abnormal Antarctic Oscillation causes anomalous Mascarene high and Australia high by meridional circulation,and then they impact local meridional circulation of East Asia through meridional teleconnection which makes the anomalous climate of winter in East Asia,causing the abnormal snow cover at the Qinghai-Tibetan Plateau at last.On the basis of results,a statistical method to discriminate the anomalous years of snow cover at the Qinghai-Tibetan Plateau objectively and quantitatively is proposed,applying the 2 discriminant equation of the three-factor optimal subset.According to the typical anomalous snow cover years given,the discriminant equation is built and argued time and again.Finally,the abnormal snow cover years from 1957 to 2003 of the Qinghai-Tibetan Plateau are distinguished.