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Connections betwen the Dominant Modes of Westerly over the Upstream Region of Qinghai-Xizang Plateau and the Regional Precipitation of China and NAO in Winter

Lookup NU author(s): Dr Xiaofeng Li

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Abstract

Based on the ERA40 reanalysis dataset and the observed precipitation data from Chinese stations, two major modes of wintertime westerly from Northern Atlantic to the upstream region of Qinghai-Xizang Plateau (QXP) were investigated through empirical orthogonal function (EOF) and their connections with the wintertime regional precipitation of China and the Northern Atlantic Oscillation (NAO). It reveals that the associated time series of the first two major modes of wintertime westerly (EOF1 and EOF2) over the upstream area of QXP are significantly correlated with the NAO, while their connections with the regional wintertime precipitation of China are totally different. The EOF1 is evidently correlated with the precipitation over the south-west of the QXP as well as the precipitation over the middle and lower reaches of Yangtze River. However, the EOF2 delineates no significant correlation with the wintertime precipitation over China. Further analysis suggests that the anomalous westerly in the low altitudes associated with EOF1 can reach to the upstream of QXP in the mid-south Asia-Europe continent, increases the creeping flow over the south-west of the QXP, enhances the precipitation over the south-west of the QXP, and vice versa. Due to the topography blocking, the detouring flow around the south side of QXP becomes stronger, converges with the anomalous south-easterly from the south side of anomalous west-Pacific subtropical high over the middle-lower reaches of Yangtze River, enhances the ascending movement, increases the anomalous precipitation over the middle and lower reaches of Yangtze River, and vice versa. While, the relationship between the EOF2 and the wintertime precipitation over China is not significant due to the anomalous zonal wind component in the low latitudes associated with EOF2 does not extend eastward. From this study, the extension of the westerly over the upstream region of QXP plays an important role in affecting the wintertime precipitation over China, and the westerly wave train associated with EOF1 in westerly is an important medium for NAO to influence the wintertime precipitation over China.

Publication metadata

Author(s): Yu J, Liu Y, Li X

Publication type: Article

Publication status: Published

Journal: Plateau Meteorology

Year: 2014

Volume: 33

Issue: 4

Pages: 877-886

Print publication date: 24/08/2014

Online publication date: 24/07/2013

Acceptance date: 22/08/2012

ISSN (print): 1000-0534

Publisher: Chinese Academy of Sciences

URL: http://www.gyqx.ac.cn/EN/10.7522/j.issn.1000-0534.2013.00108

DOI: 10.7522/j.issn.1000-0534.2013.00108

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