A climatological analysis of northward-moving typhoon in environments of the Northeast China cold vortex

This study investigates the influence of the Northeast China cold vortex (NCCV) on the northward-moving typhoons (NTCs) over the western North Pacific (WNP). There is a significant inverse relationship between the NCCV during June-September and simultaneous NTCs during 1981-2021. Fewer (more) NTCs are observed during NCCV active (inactive) year a combination of less (more) NTC genesis, particularly over the central Pacific region of 10 degrees-30 degrees N and 130 degrees-150 degrees E, and fewer (more) NTCs moving northwestward and making landfall in coastal regions of the Yellow Sea and Bohai Sea. These regions are characterized by significantly decreased low-level vorticity and mid-level humidity, which impedes NTC genesis and notably enhances the deep-layer subtropical straight westerly steering flow, thus blocking the northward movement of NTCs. These remarkable environmental changes during different NCCV years are clearly linked with the changes of an anomalous anticyclone in the subtropics (20 degrees-30 degrees N, 120 degrees-160 degrees E). In short, more (less) NCCV activity strengthens (weakens) the anomalous anticyclone, resulting in fewer (more) NTCs. Annual frequency of NTCs during June-September from 1981 to 2021 as well as simultaneous NCCV occurrence days. Correlation coefficient and its significance level based on a Student's t-test are shown in the panel. A significant inverse relationship between the Northeast China cold vortex (NCCV) and the simultaneous northward-moving typhoon (NTC) is revealed by climatic statistics. Their inverse relationship can be explained by a combination of less NTCs genesis over the central Pacific and less NTCs moving northwestward and landfalling at coastal regions of the Yellow Sea and the Bohai Sea during the active NCCV years. image