Observational analysis of the structure of Typhoon Haitang (0505) over the western North Pacific by using the GPS Dropsonde data.

On the basis of the global positioning system (GPS) dropsondes data collected in the Dropsonde Observations for Typhoon Surveillance near the Taiwan Region (DOTSTAR), the vertical kinetic and thermodynamic structures of the strong typhoon named Haitang (0505) over the western North Pacific are analyzed and compared for its different development stages. The results show that not only the kinetic structure but also the thermodynamic structure of Haitang’s is more robust in the second surveillance than the first surveillance, which is manifested by the stronger and larger scope of cyclonic inflow and the upperlevel warm core, as well as the developed anticyclonic outflow. Besides, Haitang was moving to the high SST region and situated in a favorable environment with weak vertical wind shear, and it therefore intensified during the second stage. The same data are also used to validate the published related numerical simulation results (Frank and Ritchie 1999， 2001), which show that the vertical wind shear can induce a wavenumber one asymmetry in the eyewall structure and has strong effect on the asymmetric structure of the tropical cyclone. The presented observational results are well consistent with their modeling results and explain how the vertical wind shear possibly produces a pronounced asymmetric structure in Haitang.