Toward modeling the spatial pressure field of tropical cyclones: Insights from Typhoon Hato (1713)

Information about the pressure field of tropical cyclones (TCs) is of crucial importance for determining a TC's wind structure. However, despite the fact that TC pressure deficit (ΔP) decreases with increasing height below a TC's outflow layer, most existing models focus only on the radial distribution of TC pressure. Quantitative studies on the spatial pressure field of TCs are considerably limited. This study presents a field study on the vertical pressure profiles of Typhoon Hato which is one of the few strongest sampled TCs in Hong Kong. Meteorological observations from eight radiosonde balloons released at different storm-relative positions during Hato's passage are investigated. Results show that the vertical profiles of ΔP below the outflow layer are distributed linearly with respect to altitude, with the slope increasing almost linearly with the increase of surface pressure deficit. Based on the above observation, an empirical model of the typhoon's spatial pressure field is established. Budget analysis of ΔP is then conducted. Both the dry-air component and water-vapor component are found to be evident. This study further presents an analytical model of TC pressure deficit. Comparison of results with various values of key input model parameters show that the model prediction is highly sensitive to the lapse rate of atmospheric temperature and surface air temperature. It is believed that both the empirical model and the analytical model have the potential to facilitate the development of TC spatial wind-field models.