初夏亚洲季风区环流低频振荡与长江下游持续暴雨

利用主成份分析和非整数波功率谱分析研究了1991年初夏亚洲季风区逐日500 hPa环流的时空分布特征。结果表明，主成份分析得到的前5个特征向量的空间分布与各个季风系统的活动有关，其时间系数存在显著的12—22天准周期振荡和28—31，43—65天的低频振荡周期，它们与长江下游暴雨形成有密切联系。当第一主成份从谷点上升且第二主成份稳定地增大（减小）时，长江下游出现持续暴雨。亚洲副热带海洋加热异常和海陆热力差异产生的不均匀加热分布激发的各种低频波及其相互作用导致向热带外能量频散的异常，是引起长江下游持续暴雨的

The Relationship Between Low Frequency Oscillation over Asia Monsoon Region and Continuous Heavy Rain in the Lower Reaches of Yangtze River Valley

By using the principal component analysis and the power spectral analysis with nonintegral waves, the characteristics of the spatial distribution and low frequency oscillation for 500 hPa circulation over Asia monsoon region during the early summer in 1991 are investigated. The results show that the first five major spatial patterns from the principal component analysis respond to the influence of different monsoon systems, respectively, and time coefficients have the remarkable periods of 12―22, 28―31, 43―65 days. The variation of oscillations is related to the heavy rain in the lower reaches of Yangtze River valley. It is important to the occurrence of continuous heavy rain that interactions between the low frequency waves which are forced by the diabatic heating anomalies and the continent-ocean heat contrast at the low latitude in Asia will lead to the anomalies of energy dispersions toward extratropical atmosphere