The Abnormal Weather and Its Circulation in Summer of 2009
摘要: 简要讨论了2009 年夏季的异常天气过程和环流形势演变，主要涉及南海夏季风、华南、江淮、东北降雨等情况。该年夏季未发生区域或流域性的洪涝，而干旱的面积较大。2009年南海夏季风在5月第4候爆发，爆发后季风的推进出现了异常，同时，印度季风的推进出现了异常。华南前汛期降雨时间长、降水范围广。江淮梅雨期典型梅雨形势没有建立，为空梅年，但西风槽和登陆台风带来了几次降雨过程。华北降水偏弱，东北低涡活动频繁，使东北北部地区降水偏多,出现了低温冷害。此外，7月8～24日和8月15日至9月14日两段时期长江中下游及其以南地区在副热带高压的控制下，出现了大范围持续高温，加剧了南方地区干旱。
Abstract: The main weather processes and their related circulations in summer 2009, including the South China Sea monsoon and the precipitation features over South China, the YangtzeHuaihe River basin, and northeast China, are discussed. There were not widearea floods, but serious heat wave and drought were reported over southern China. The South China Sea monsoon began at the fourth pentad of May. The Indian Monsoon was extremely abnormal than usual which may influenced the variation of rainband in China. The typical circulation and the related strong precipitation during the Meiyu period over the Yangtze River basin did not appeared, however, the westerlies troughs and landing typhoons brought several rainfall processes to the YangtzeHuaihe River basin. The total precipitation over North China was below normal. The vortices over northeastern China were very active in the summer of 2009, which resulted in the more precipitation and low temperature in that area. In addition, the heat wave and drought occurred in southern China during 8 to 24 July and 15 August to 14 September, and both of the periods were associated with the western Pacific subtropical high.
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