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The Connection between the Sea Surface Height Anomaly Preceding the Indian Ocean Dipole and Summer Rainfall in China |
DUAN Xin-Yu1,2, LIU Na2,3,4, LI Shuanglin2,3 |
1College of Atmospheric Science, Plateau Atmosphere and Environment Key Laboratory of Sichuan Province, Chengdu University of Information Technology, Chengdu 610225, China
2Nansen-Zhu International Research Centre, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
3Climate Change Research Center, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
4University of Chinese Academy of Sciences, Beijing 100049, China |
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Abstract The sea surface height anomaly (SSHA) signals leading the fall Indian Ocean Dipole (IOD) are investigated. The results suggest that, prior to the IOD by one year, a positive SSHA emerges over the western-central tropical Pacific (WCTP), which peaks during winter (January-February-March, JFM), persists into late spring and early summer (April-May-June, AMJ), and becomes weakened later on. An SSHA index, referred as to SSHA_WCTP, is defined as the averaged SSHA over the WCTP during JFM. The index is not only significantly positively correlated with the following-fall (September-October-November, SON) IOD index, but also is higher than the autocorrelation of the IOD index crossing the two different seasons. The connection of SSHA_WCTP with following-summer rainfall in China is then explored. The results suggest that higher (lower) SSHA_WCTP corresponds to increased (reduced) rainfall over southern coastal China, along with suppressed (increased) rainfall over the middle–lower reaches of the Yangtze River, North China, and the Xinjiang region of northwestern China. Mechanistically, following the preceding-winter higher (lower) SSHA_WCTP, the South Asia High and the Western Pacific Subtropical High are weakened (intensified), which results in the East Asian summer monsoon weakening (intensifying). Finally, the connection between SSHA_WCTP and El Ni?o-Southern Oscillation (ENSO) is analyzed. Despite a significant correlation, SSHA_WCTP is more closely connected with summer rainfall. This implies that the SSHA_WCTP index in the preceding winter is a more effective predictor of summer rainfall in comparison with ENSO.
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Received: 23 January 2015
Revised: 14 April 2015
Accepted: 15 April 2015
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Corresponding Author:
LIU Na
E-mail: liuna0209@mails.ucas.ac.cn
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