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《Chinese Journal of Atmospheric Sciences》 2018-05
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Differences in Intraseasonal Activity of Eurasian Subtropical Zonal Wave Train and Associated Indian Summer Rainfall in Two Opposite AMO Phases

SUN Xueqian;LI Shuanglin;SUN Jilin;HONG Xiaowei;Climate Change Research Center,Institute of Atmospheric Physics,Chinese Academy of Sciences;College of Ocean and Atmosphere,Ocean University of China;College of Earth and Planetary Science,University of Chinese Academy of Sciences;Department of Atmospheric Science,China University of Geosciences;  
By using daily variables extracted from the NCEP/NCAR reanalysis, this study compares the intraseasonal activities of the Eurasian summer subtropical wave train during the two opposite phases of the Atlantic Multidecadal Oscillation(AMO). Significant difference is found based on pentadic mean 200-h Pa meridional wind component. The associated intraseasonal variability of Indian summer precipitation is also different during the two AMO phases. Lead-lag regressions of 500-h Pa wind field and vertical motion are then conducted to illustrate the AMO's modulation on the subtropical wave train and the Indian summer rainfall. The results suggest that during the AMO negative phase, the intraseasonal evolution of the positive-phase subtropical wave train has positive centers over the Great Britain and the Black-Caspian Sea but negative centers over the North Atlantic south of Greenland, the Mediterranean and north of South Asia in 200-h Pa height. This pattern of wave train induces anomalous subsidence and reduced rainfall in central and northwestern India. It is opposite for the negative-phase subtropical wave train. In contrast, during the positive AMO phase, positive-phase subtropical wave train originates from the North Atlantic south of Iceland and propagates toward northeastern South Asia via southern Denmark, western Russia and central Asia. The intraseasonal evolution of this wave train leads to anomalous convergence and increased rainfall in most areas of India. It is opposite for the negative-phase subtropical wave train. This study highlights the AMO's modulation on intraseasonal variability of Indian summer rainfall through influencing the Eurasian summer subtropical wave train.
【Fund】: 国家重点基础研究发展计划(973)项目2015CB453202~~
【CateGory Index】: P461.2
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