Influence of Remote Thermal Disturbances Induced by Tropical Cyclones on the East Asian Subtropical Westerly Jet
摘要
Tropical cyclones (TCs) in the tropical western North Pacific and the east Asia subtropical westerly jet (EASWJ) are important circulation systems in the east Asia–western north Pacific region, and interactions exist between them. Through statistical analysis and numerical experiments, this study delved into the influence of thermal remote disturbances induced by TC on the EASWJ, and the mechanism has also been analyzed. Statistical results show that TC activities in the tropical western North Pacific can cause anomalous westerlies near Japan, and the EASWJ axis in the corresponding area shifts significantly toward the high-value area of anomalous westerlies caused by TCs. Results of numerical experiments with TC Maria verified the results of the statistical analysis, and further revealed that TC Maria, locating in the tropical western North Pacific, induced anomalous cold advection in the vicinity of mid-latitude Japan. This, in turn, caused anomalous descent, ultimately leading to both anomalous adiabatic heating and anomalous latent heat absorption. Consequently, these changes altered the temperature distribution in the East Asian mid-latitudes and resulted in anomalous meridional temperature gradients. Under the constraint of thermal wind balance, the zonal wind over East Asian mid-latitudes changed accordingly, causing a shift in the location of the high-value westerly, which corresponds to the anomalous meridional movement of the EASWJ axis. The findings of this study indicate that TCs can affect EASWJ by exciting remote thermal disturbances.