利用澳大利亚气象局的RMM-MJO (Real-time Multivariate MJO) 指数, 分析研究了热带大气季节内振荡 (简称MJO) 对西北太平洋台风的调制作用及其机理, 结果表明MJO活动对西北太平洋台风的生成有比较明显调制作用。在MJO活跃期, 对流中心位于赤道东印度洋 (即MJO第2、3位相) 和对流中心越过海洋性大陆来到西太平洋地区 (即MJO 第5、6位相) 时台风生成的个数比例为2∶1。本文对西太平洋地区的大气环流场进行了多种气象要素的合成分析, 在MJO的不同位相, 西太平洋地区的动力因子分布形势有很明显不同。在第2、3位相, 各种因子均呈现出抑制西太平洋地区对流及台风发展的态势; 而在第5、6位相则明显有促进对流发生发展, 为台风生成和发展创造了有利条件的大尺度环流动力场。这说明MJO 在不断东移的过程中, 将改变大气环流形势, 最终影响了台风的生成和发展。接着， 我们从积云对流这个联系台风和MJO的重要因子出发, 研究了不同MJO位相时凝结加热的水平和垂直分布, 以及与台风环流、 水汽通量的配置情况。结果表明在MJO不同位相, 热源分布明显不同, 而这种水平和垂直方向的不同分布特征必然反映潜热释放和有效位能向有效动能转换的差异, 再与水汽的辐合辐散相配合, 就从台风获得的能量角度揭示了大气MJO调节台风的生成和发展, 造成不同位相时台风生成有根本差别的原因。
The RMM (Real-time Multivariate MJO) index from RMRC (bureau of meteorology research centre) of the Centre for Australian Weather and Climate Research is used to study the modulation of the Madden-Julian Oscillation (MJO) on the typhoon activity over the northwestern Pacific Ocean area and its possible mechanism. The RMM index serves as a proxy for the MJO. It not only can describe the strength of the MJO, but also can reveal the spatial distribution characteristics with the phase categories. It divides the MJO process into eight phases. The MJO modulation effect on typhoon genesis is quite significant. From June to October, the typhoon genesis cases during strong MJO period are 2 times of those during weak MJO period. In the strong MJO period, there are different typhoon genesis distribution patterns due to different MJO activity phases. The total genesis cases during phases 2 and 3, in which the convection centers are over the equatorial eastern Indian Ocean, are also 2 times of those druing phases 5 and 6, during which the convection centers are over the northwestern Pacific Ocean. After the statistic analysis, the composite method is used to study different atmospheric circulation patterns associated with different MJO phases. The result shows the dynamic typhoon-influencing factors are quite different between phases 2-3 and phases 5-6. During phases 2 and 3, the dynamical factors suppress the typhoon to happen, but during phases 5 and 6, they create a favorable environment circulation for typhoon genesis. It can be inferred that the large scale dynamical environment changes as the MJO convection propagates eastward, which plays an important role in the typhoon genesis. Convection is a very important factor to both the MJO and typhoons. The composites of the horizontal and vertical convective heating distributions according to different MJO phases are studied. The result shows that in different phases, the heating sources are quite different, which would definitely lead to different change from effective potential energy to effective kinetic energy. In combination with the convergence and divergence of the moisture transport fluxes, the modulation of typhoon genesis by MJO can be revealed from the energy aspect.