关键词: 台风北折路径, 引导气流, 位涡倾向, 水平平流项

Abstract: In 2022, Typhoon "Chaba" entered Guangxi during the night of July 2nd. Its track suddenly turned northward, resulting in significant deviations in wind and rain forecasts and exerting a severe impact on the typhoon defense efforts.Using utilizes multi-source meteorological observation data such as upper-air, surface, and satellite data and E ERA-Interim reanalysis data, to analyze the main causes for the abnormal northward turn of Typhoon "Chaba" after its landfall.The results show that: (1) The superimposition and strengthening of the Western Pacific subtropical high pressure with a double-ridge line pattern and the Westerly ridge, which extended westward and formed a northward guiding airflow, was the primary reason for the sudden northward turn of the typhoon track of "Chaba". (2) The southwest airflow in front of the upper-level Westerly trough and on the north side of the South Asian high-pressure monomer was connected to the outflow of the typhoon, forming an upper-level northward outflow that facilitated the northward movement of Typhoon "Chaba". (3) The 850 hPa wind field exhibited an asymmetric structure. During the northward turn of the track, the strong wind speed area shifted to the east side of the typhoon center, while the northward component intensified. (4) Before the track turned, a turning signal of 0 m·s-1 appeared in the deep zonal average guiding airflow. The rapid enhancement of the westerly and southerly components led to the northward movement of Typhoon "Chaba". (5) The change in positive vorticity advection was indicative of the northward turn of the typhoon track of "Chaba", and the typhoon tended to move towards the area with a large value of positive vorticity advection. (6) Positive vorticity centers tend to indicate better the process of typhoon path northward bending. The turning of Typhoon "Chaba" was mainly influenced by the combined effects of the horizontal advection term and the vertical advection term, with the horizontal advection term playing a dominant role. The external large-scale circulation of the typhoon was the main reason for its path northward bending.

Key words: typhoon northward turning track, steering flow, potential vorticity tendency, horizontal advection