中文摘要：

利用美国气象环境预报中心/美国国家大气研究中心（NCEP/NCAR）再分析资料以及局地纬向平均的经圈环流线性诊断方程，诊断了1979-2010年6-8月南海夏季风期间经圈环流变化，定量讨论了影响南海夏季风经向环流异常的主要物理过程。结果表明，强南海夏季风年南海地区（10°-15°N）低层（900hPa）存在异常偏南风，弱南海夏季风年南海地区低层存在异常偏北风。定量分析表明，在强南海夏季风年对距平经圈环流低层经向分量起主要作用的是凝结潜热加热（68%）、体现越赤道气流影响的边界作用（14%）和潜热通量（12%）；对弱南海夏季风年距平经圈环流低层经向分量起主要作用的是凝结潜热加热（46%）、边界作用（38%）和热量垂直输送（13%）。分析对应的环流形势可知，反映凝结潜热加热异常作用的副热带高压与反映边界作用的澳大利亚高压在强弱季风年表现出相反的特征。与海洋强迫有关的潜热通量对南海夏季风的强弱起了重要作用，其在强、弱南海夏季风年的分布也存在明显差异：强南海夏季风年异常潜热通量在南海分布为南正、北负，弱夏季风年则相反。

英文摘要：

Based on the National Centers for Environmental Prediction/the National Center for Atmospheric Research （NCEP/NCAR） reanalysis dataset, the meridional circulation of the South China Sea Summer Monsoon （SCSSM） in June-August from 1979 to 2010 is diagnosed using the linear diagnostic equation. The major processes that affect the meridional circulation of the SCSSM are discussed quantitatively. The anomalous meridional circulation indicates that the low-level （900-hPa） southerly over the SCS （10°？15°N） is stronger in strong SCSSM years than in normal years, and that in weak SCSSM years there exists stronger northerly in the SCS. The quantitative analysis shows that the contributions to the anomalous meridional component of the meridional circulation in the lower level over the SCS in anomalous strong SCSSM years are mainly from the processes related to latent heating （68%）, boundary effect （or the effect of cross-equatorial flow） （14%）, and air-sea latent-heat flux （12%）. In weak SCSSM years, the contributions are mainly from the processes related to latent heat （46%）, boundary effect （38%）, and vertical transport of heat （13%）. The general circulation associated with the major processes shows that the western Pacific Subtropical High （WPSH） related to latent heating and the Australia High （AH） associated with boundary effect have the opposite characteristics in strong/weak SCSSM years. Latent-heat flux also contributes to monsoon intensity. The distribution of latent-heat flux over the SCS is opposite in strong/weak SCSSM years. In the strong （weak） SCSSM years, the latent-heat flux anomalies is positive （negative） over the southern SCS and negative （positive） over the northern SCS.