2007年南海夏季风季节内振荡的北传及影响因子

THE NORTHWARD PROPAGATION AND MECHANISMS OF THE INTRASEASONAL OSCILLATION OF SOUTH CHINA SEA SUMMER MONSOON IN 2007

利用2007年全球降水气候计划GPCP(the Global Precipitation Climatology Project)卫星红外窗口导出的全球降水指数GPI(the Global Precipitation Index)的日降水资料及频率-波数分析方法,分析2007年南海夏季风季节内振荡(Intraseasonal Oscillation,ISO)的传播特征,并使用美国国家环境预报中心(NCEP)/美国大气研究中心(NCAR)再分析的逐日资料,探讨影响其传播的主要因子。结果表明,南海夏季风ISO有明显的北传趋势,并且明显比南传分量占优。影响南海夏季风ISO北传的主要因子是平均纬向风垂直切变和平均经向风对异常水汽的输送。之所以异常经向风对平均水汽的输送及海-气相互作用的影响在南海地区不重要,而在印度季风区有一定的贡献,是因为平均水汽和纬向风分布在两个地区的差异。

The Global Precipitation Climatology Project（GPCP） Satellite-Derived（IR） GPI Daily Rainfall and frequency-wavenumber method are used to analyze the propagating features of the intraseasonal oscillation（ISO） associated with South China Sea summer monsoon（SCSSM） in 2007.Then,the NCEP（National Centers for Environmental Prediction）/NCAR（National Center for Atmospheric Research） daily reanalysis are employed to explore what drives the ISO propagate northwards.The results indicate that the ISO of SCSSM tends to move northwards greatly and the northward propagation is much larger than the southward one.Climatological mean zonal wind vertical shear and anomalous water vapor,transported by the mean meridional flow,play important roles in the northward propagation of ISO of SCSSM.However,because of differences in mean zonal flow and water vapor between the SCSSM and Indian summer monsoon region,mean water vapor transported by anomalous meridional wind and air-sea interaction plays a negligible role in the northward propagation of ISO over the SCSSM region,though with considerable contribution to the Indian summer monsoon region.