Abstract:Using dynamic synthesis method, this paper comparatively analyzes the reasons for heavy rainfall induced by tropical cyclones passing through Jiangsu Province with and without the influence of cold air. A meteorological model of heavy rainfall associated with tropical cyclones in Jiangsu is established. The results are that, regardless of the influence of cold air, tropical cyclones having moved into Jiangsu Province can induce heavy rainfall. The key reasons include the evolution of tropical cyclone’s asymmetric structure, the continuous water vapor transport by low-level jet streams, and the sustained strong upward motion near the tropical cyclone. The differences between the situations with and without the influence of cold air mainly lie in the maintenance mechanisms of dynamic uplift and the developing means of atmospheric instability. When cold air is present, baroclinicity and conditional instability within the peripheral circulation of tropical cyclone intensify rapidly. Slantwise ascending motion in the baroclinic zone promotes the sustained lifting of warm-moist air and enhances convective development, with heavy rainfall primarily located on the northern to northeastern side of tropical cyclone. When cold air is absent, continuous transport of warm-moist air by low-level and ultra-low-level jets significantly enhances the conditional instability near and around the center of tropical cyclone. The deep vertical updraft, which is maintained by convergence within the warm sector and further enhanced by latent heat release, favors the development of convective precipitation, with heavy rainfall mainly existing on the eastern to northeastern side of tropical cyclone.