摘要
使用国家气象信息中心整理的逐日降水资料和NCEP/NCAR逐日再分析资料,创建了江南春雨建立时间指数和南海副热带高压(副高)减弱时间指数,研究了江南春雨各要素的相互关系及其与东亚夏季风环流和降水的关系。分析表明,当江南春雨建立较晚时,夏季江南地区的降水也较少,这是由于东亚夏季风加强,高原近侧气旋性环流加强,使江南地区出现异常反气旋性环流(气旋性辐合环流减弱)所致;当南海副高减弱较晚时,长江中下游至江南地区降水偏多,易发洪涝,这主要是由于东亚夏季风减弱,南海副高偏强,华南的异常西南风与围绕高原的异常反气旋环流的偏北风在长江中下游流域形成异常气旋性环流所致。江南春雨的建立时间和南海副高减弱时间之间又具有线性无关性,可以为东亚夏季风环流和降水异常的预报提供重要线索。两指数与3月ENSO综合指数MEI关系密切,表明东亚的气候异常与ENSO全球气候异常紧密联系,因此在分析预测东亚气候异常时必须同时关注全球气候异常背景。
National Meteorological Information Center （NMIC） rainfall data and NCEP/NCAR daily circulation reanalysis data are employed to establish onset-pentad index of SPR （Spring persistent rain） and the drop-pentad index of the South China Sea Sub-High （SCSSH）. These indexes are used to study the relationship between the factors in SPR period and their relations to the circulation and precipitation of the East Asia summer monsoon （EASM）. Results show that, the summer rainfall over southeastern China decreases when SPR onset is late. For then EASM strengthens and the cyclonic circulation around the Tibet Plateau （TP） strengthens, which makes abnormal anti-cyclonic circulation （cyclonic convergent circulation weakens） appear over southeastern China. When the drop of SCSSH delays, abnormal flood prevail on the south of the middle and lower reaches of the Yangtze river. That is mainly caused by EASM weakening while SCSSH strengthening. The anomalous southwesterly over South China and the northerlies of abnormal anti- cyclonic circulation around TP converge over the Yangtze valley. The onset-pentad index and the drop-pentad index are independent with each other, which is favorable to the prediction of the anomalies of the circulation and precipitation of EASM. The two indexes have high correlations with Multivariate ENSO Index （MEI） in March, indicating that the climate abnormity in East Asia correlates with global climate abnormity tightly. From this point of view, we must take the global climate background into account when we analyse and predict the East Asia summer circulation and precipitation.
出处
《气象学报》
CAS
CSCD
北大核心
2008年第5期800-807,共8页
Acta Meteorologica Sinica
基金
国家973项目(2006CB403600)
国家自然科学基金项目(40475027
40220503和40523001)
关键词
江南春雨
东亚夏季风
南海副高
相关分析
时间指数
Spring persistent rains, EASM, SCS subtropical high, Correlation analysis, Time indexes
