热带太平洋经向风应力异常与El Nino的发生——(Ⅰ)资料诊断

摘要

By using correlation analysis and singular value decomposition (SVD) methods, diagnostic studies are made to investigate the relationship between the meridional wind stress anomalies over the tropical Pacific and El Nino events. The correlation of the sea surface temperature anomalies (SSTA) in the NINO3 region (150°-90°W, 5°S-5°N) and the leading meridional wind stress anomalies shows that the NINO3 SSTA is significantly correlated with the anomalous meridional wind stress convergence in the equatorial eastern Pacific at the leading time of more than six months. With the reduction of the leading time, the correlation becomes stronger and the convergence area with statistical significance enlarges and extends to the west. The coupling patterns between SSTA in tropic Pacificand the leading meridional wind stress anomalies revealed by SVD show the similar feature to that revealed by the correlation analysis. The converging meridional wind stress about the equator in the eastern equatorial Pacific precedes the increasing of SSTA in the central and eastern equatorial Pacific as early as half a year or more. Compared to the leading zonal wind stress anomalies in the tropical western Pacific, it seems that the increasing of the NINO3 SSTA is more related to the convergence of the leading meridional wind stress anomalies in the eastern equatorial Pacific. It is suggested that preceding meridional wind stress anomalies may play an important role in the occurrence of El Nino events.%对热带太平洋海表经向风应力异常与EI Nino事件之间的关系进行了诊断分析。结果表明，超前的经向风应力距平场与NINO3区(150°-90°W，5°S-5°N)的海面温度异常(SSTA)有显著的超前相关，这种相关性在超前6个月甚至更早一些就有显示。利用奇异值分解方法分析超前的经向风应力距平场与太平洋海表温度异常场之间的耦合模，结果表明对应于赤道中东太平洋的海面温度异常升高，大气风应力场在超前6个月甚至更早的时候，在赤道中东太平洋表现为辐合的经向异常风应力场，即赤道以北为北风异常应力，赤道以南为南风异常应力。这种耦合模的时间系数与NINO3 SSTA指数所表示的El Nino事件有很好的对应关系，表明这种耦合模反映的正是超前的经向风应力异常与El Nino事件所对应的海表温度异常之间的相关模态。通过与热带西太平洋纬向风应力异常的比较，赤道中东太平洋辐合的经向风应力异常与El Nino事件发生的同样具有重要的联系。