2010年南方持续暴雨期大气环流异常及其低频特征研究

Abnormality of General Circulation with LFO During the Torrential Rainstorms over Southern China in 2010

利用NCEP/NCAR逐日再分析资料以及国家气候中心台站降水资料等,应用多变量经验正交函数展开(MV-EOF)等方法,对2010年南方持续暴雨期大气环流异常及其低频特征进行了分析。结果表明;2010年东亚夏季风异常偏弱、西太平洋副热带高压位置异常偏南、三次季风涌的出现和高空急流与散度场活动异常及其相互配合,是南方降水异常的主要影响系统;对风场和降水场MV-EOF空间型分布的分析显示,低频降水中心与200 hPa的气流辐散中心和850 hPa辐合中心相关联;降水的第一模态反映了东亚夏季风的气候态演变,第二、三模态反映了夏季风在季节性推进过程中不同尺度的低频振荡,7月前半月和6月中下旬,第二、三模态分别处于低频振荡的正位相,使长江中下游梅雨和华南前汛期延迟结束,并且增强了江南的梅雨降水,夏季风的气候态演变和低频振荡相叠加导致2010年我国南方暴雨频发。

By using NCEP/NCAR daily reanalysis data and NCC station precipitation data, the authors ana- lyze the abnormality of general circulation with LFO during the torrential rainstorms over southern China in 2010 with the application of multivariate empirical orthogonal function （MV-EOF）. Results show that： the East Asian summer monsoon to be exceptionally weak, the West Pacific subtropical anticyclone to be exceptionally southerly, the emergence of three monsoon surges, the abnormal activities of upper level westerly jet and divergence field and their interactions with one another, are the main affecting systems of precipitation abnormality over southern China in 2010. To the MV-EOF spatial distributions of wind and precipitation fields, the centers of low-frequency precipitation always correspond to those of 200 hPa flow divergence and 850 hPa convergence. The first MV-EOF mode of precipitation field reflects the climatic evolution of East Asian summer monsoon, while the second and third modes reflect the LFOs on different time scales of summer monsoon during the seasonal advancing process. The second mode is in positive phase of LFO during the first half of July while the third mode during the middle and later part of June, so that the ends of Jiang huai Meiyu season and early flood season of southern China are put off and Meiyu precipitation in the middle and lower reaches of the Yangtze River is enhanced. The climatic evolution of summer monsoon coincided with LFO ultimately leads to the frequent rainstorms over southern China in 2010.