Analysis of the Peripheral Characteristics of Tropical Storm Sinlaku (2020) Based on Dropsonde Data

This study investigates the wind field structure and thermodynamic characteristics in the peripheral region of Tropical Storm Sinlaku (2020) through an integrated analysis of airborne dropsonde data, ERA5 reanalysis data, and China Meteorological Administration (CMA) best track dataset. The results indicate that the structure of the wind field varies with altitude, and dropsonde observations capture key features consistent with the dissipating stage of the tropical cyclone. Southwesterly winds are predominant in the middle and lower troposphere (500–975 hPa), which constitute the primary outflow layer and exhibits cyclonic motion. The tangential wind reaches its maximum speed (>17 m s^–1) at an altitude of 3–4 km in the middle troposphere, coinciding with the region of the strongest cyclonic motion. Within the same group, as the dropsonde moves closer to the tropical storm center, the intensity of the cyclonic motion in the middle troposphere intensifies. In addition, the southeasterly winds dominate in the upper troposphere, which, along with the near-surface area, constitute the inflow layers. When the dropsonde is closer to the tropical storm center, the top of the near-surface inflow layer is observed at a lower altitude. Horizontal temperature gradients at different positions are relatively weak, but the vertical temperature lapse rate exhibits localized changes at different heights. The typhoon′s peripheral cloud system exists in an atmospheric environment characterized by instability in the lower levels and relative stability in the middle to upper levels.