Abstract:

Based on the observed snow depth data from more than 70 weather stations in the Tibetan Plateau, as well as spring and summer precipitation over Northwest China from 1971 to 2010, the relations between the abnormal snow depth in the Tibetan Plateau from November to next March and spring, summer precipitation in Northwest China were studied by using the singular value decomposition (SVD) analysis. The results show that the abnormal snow depth in winter and spring in the Tibetan Plateau had significant correlation with spring and summer precipitation in Northwest China. Change of winter and spring snow depth in the Tibetan Plateau was a prognostic factor to the late spring and summer precipitation in Northwest China. The abnormal snow depth in winter and spring in the Tibetan Plateau had a positive feedback to the spring and summer precipitation in Northwest China, but the key influencing areas were different. When winter-spring snow depth in the central of the Tibetan Plateau was more (less) than the average, then spring precipitation in the eastem and southem of Gansu, Ningxia and Shaanxi significantly increased(decreased), and summer precipitation in the east and south of Gansu and the western of Ningxia increased(decreased). When winter-spring snow depth in the Tibetan Plateau was much, spring precipitation in most part of Northwest China was much too, but it was less in the northern of Xinjiang, and summer precipitation was much in the southern of Xinjiang, the central of Gansu, the most part of Qinghai and Shaanxi, especially in south Shaanxi precipitation increased significantly, while it was less in the northern of Xinjiang, the northern and eastern of Gansu.

Key words: snow depth in winter and spring, Tibetan Plateau, singular value decomposition (SVD), precipitation in Northwest China

摘要：

基于1971～ 2010年青藏高原70余个气象台站逐日积雪深度资料和西北地区春、 夏季降水日资料，利用奇异值分解(SVD）方法分析了高原冬春积雪深度分别与西北地区春季、 夏季降水的关系。结果表明： 高原冬春积雪异常与西北地区春、 夏季降水存在显著相关， 冬春积雪深度的变化对后期春、 夏季西北地区降水有指示和预测意义。高原冬春积雪深度异常对西北地区春、 夏季降水主要以正反馈为主，但影响的关键区有所不同。高原冬春积雪中部偏多时， 春季降水在陇东南、 宁夏及陕西地区显著偏多；夏季降水在陇东南及宁夏西部显著偏多。从高原多雪年与少雪年的角度出发， 分析了西北地区降水的差异， 表明高原冬春积雪偏多， 春季西北大部地区降水偏多， 北疆偏少； 夏季在南疆、 甘肃中部、 青海大部及陕西降水偏多， 尤其陕西南部地区增多显著， 北疆、 肃北及陇东部分地区降水偏少。

关键词: 冬春积雪深度, 青藏高原, 奇异值分解（SVD） , 西北地区降水