本研究使用觀測資料及高解析度大氣模式(High-Resolution Atmospheric Model, HiRAM) 的模擬結果，探究Madden-Julian oscillation (MJO)對西北太平洋颱風活動的影響，尤其聚焦於颱風季(六至九月)時之南海盆地。觀測分析顯示，MJO顯著地影響位於南海盆地生成的颱風，較多(少)的颱風會在MJO處於增強(抑制)對流相位時形成。此外MJO也在控制南海盆地上西行與東行颱風路徑方面扮演了重要角色。HiRAM的模擬顯示，當大氣具有較快傳播速度之MJO時，模式將能適當地重現南海盆地上，和MJO變異有關之颱風活動整體特徵變化(包含其生成與路徑)。 於RCP8.5暖化情境下，HiRAM推估在21世紀末（2075-2099），MJO八相異相位的颱風生成數量皆會顯著地下降。此外，若與模擬現今氣候狀態（1980-2004年）之模式結果相比，藉由比較增強對流相位和抑制對流相位之間的颱風日平均生成率，HiRAM還預測出MJO對南海盆地生成的颱風影響將會更大，對於颱風移動軌跡也有較強的調節作用。 ;This study investigated the impacts of Madden-Julian Oscillation (MJO) on tropical cyclone (TC) activity over the western North Pacific (WNP), with a focus on the South China Sea (SCS), based on results from observations and high-resolution atmospheric model (HiRAM) simulations. Observational analyses showed that MJO imposes marked impacts on TC genesis over the SCS, with more (less) TC formations during the enhanced (suppressed) convection phases of MJO. Besides, MJO also plays an important role in modulating the tracks of both westward-moving and eastward-moving TCs in the SCS. Results from HiRAM simulations demonstrated that, while the model generates an MJO of faster propagation, the general features of TC activity (including genesis and track) changes over the SCS associated with MJO variability have been properly produced by HiRAM. During the late 21th century period (2075-2099), TC genesis numbers in eight different MJO phases are expected to decrease significantly as projected by HiRAM under the RCP 8.5 warming scenario. Furthermore, HiRAM also projects a greater impact of MJO on TC genesis over the SCS, with a larger contrast of averaged daily genesis rate (DGR) between enhanced and suppressed convection phases as well as a greater modulation of MJO on TC moving trajectories compared to those in present climate state simulations (1980-2004).
