Impacts of Thermodynamics Disturbances Induced by Tropical Cyclone on the East Asian Subtropical Westerly Jet

This research discusses the influence of tropical cyclone (TC) activities in the summer tropical northwest Pacific on the East Asian midlatitude westerly jet through statistical analysis and numerical experiments, and the mechanism is also analyzed.

The statistical results indicate that TC activities in the northwest Pacific can induce abnormal westerlies in the midlatitude region of East Asia, and the axis of the westerly jet shifts toward regions with larger anomalous westerlies induced by TCs.

Numerical research on the case of TC Maria shows that the thermal effects of the abnormal disturbances near Japan induced by TC activities in the tropical northwest Pacific can result in abnormal temperatures in the midlatitude region of East Asia. Under the constraint of thermal wind relation, the abnormal westerlies form and the position of the westerly jet changes, correspondingly. During this process, the abnormal phase of the P-J teleconnection induced by TC activities plays a major role in causing the subsidence motion in the midlatitude region of East Asia, leading to abnormal changes of the atmospheric temperatures, which affect the meridional temperature gradient in the midlatitude region. Due to the vertical variation of zonal winds and horizontal temperature gradients in the midlatitude region satisfying the thermal wind relationship overall, the zonal winds in the midlatitude region undergo abnormal vertical variations correspondingly, which further changes the position of area with maximum value of the East Asian westerly, and the meridional position of westerly jet axis changes as well.

Results of this study demonstrate that TC-induced remote disturbances have thermal effects and can also affect midlatitude systems.