Relationship between the Late Spring NAO and Summer Extreme Precipitation Frequency in the Middle and Lower Reaches of the Yangtze River

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• 作者：TIAN Bao-QiangFAN Ke
• 会议时间：2014-11-03
• 关键词：North Atlantic Oscillation ; summer extreme precipitation frequency ; the middle and lower reaches of the Yangtze River Valley ; East Asian westerly jet
• 作者单位：TIAN Bao-Qiang(Nansen-Zhu International Research Centre, Institute of Atmospheric Physics,Chinese Academy of Sciences, Beijing 100029, China ;University of Chinese Academy of Sciences, Beijing 100049, China)FAN Ke(Nansen-Zhu International Research Centre, Institute of Atmospheric Physics,Chinese Academy of Sciences, Beijing 100029, China ;Key Laboratory of Regional Climate-Environment for East Asia, Chinese Academy of Sciences Beijing 100029, China)
• 会议名称：第31届中国气象学会年会
• 会议地点：北京
• 主办单位：中国气象学会
• 语种：chi

摘要

The relationship between the late spring North Atlantic Oscillation (NAO)and the summer extreme precipitation frequency (EPF) in the middle and lower reaches of the Yangtze River Valley (MLYRV) is examined using an NECP/NCAR reanalysis dataset and daily precipitation data from 74 stations in the MLYRV.The results show a significant negative correlation between the May NAO index and the EPF over the MLYRV in the subsequent summer.In positive EPF index years, the East Asian westerly jet shifts farther southward, and two blocking high positive anomalies appear over the Sea of Okhotsk and the Ural Mountains.These anomalies are favorable to the cold air from the mid-high latitudes invading the Yangtze River Valley (YRV).The moisture convergence and the ascending motion dominate the MLYRV.The above patterns are reversed in negative EPF index years.A wave train pattern that originates from the North Atlantic extends eastward to the Mediterranean and then moves to the Tibetan Plateau and from there to the YRV, which is an important link in the May NAO and the summer extreme precipitation in the MLYRV.The wave train may be aroused by the tripole pattern of the SST, which can explain why the May NAO affects the summer EPF in the MLYRV.