Dynamic Investigations of Track and Intensity Evolution Associated with Typhoon Nepartak (2016) Approaching Taiwan with Ocean-coupled Model HWRF

• Main Authors: Yun-Yuan Liu, 劉允元
• Other Authors: Ching-Yuang Huang
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/tr5nhw

碩士 === 國立中央大學 === 大氣科學學系 === 107 === In past researches, operational coupled model Hurricane Weather Research and Forecasting (HWRF) have been demonstrated its capability of typhoon simulation. In this research, we applied HWRF to simulated invaded typhoon Nepartak (2016). Investigating the dynamic factors within difference in intensity and track between different experiments. At first, 8 different physics scheme combinations have been selected to demonstrate the capability of typhoon (tc) simulation. The result shows that the predictions of HWRF are overall captured tc activity. According to the result, the most accurate simulation will be chosen to be CTRL experiment, and as the comparative experiments, different westbound track and intensity simulation will be chosen. For the intensity difference part, we applied the momentum and angular momentum (AM) budget analysis. Through the budget analysis and the 3-dimension wind speed difference in different experiments, the amounts of larger angular momentum inward transportation will also be different, this effect will influence the wind speed intensification inside the bottom layer. Strong inward motion in the bottom will further enhance vertical convection near RMW, therefore, the upward transportation of angular momentum will be different; For the track difference part, we applied the potential vorticity (PV) budget to analyze it. While tc is moving upon the open ocean, horizontal advection will dominate the translation speed and direction of each experiment, which can be understood as composition of background steering and typhoon circulation. Once the typhoon approach Taiwan, vertical advection and diabetic heating then become more important for typhoon translation speed and toward direction. This research has further analyzed the coupled and uncoupled model comparison and the effect of Taiwan topography. As coupled model could provide the sst contains the typhoon induced sst cooling, it will get more accuracy simulation of intensity. Trough the PV budget analysis, The track difference between coupled and uncoupled model have been proved that is also induced by horizontal advection. For the effect of Taiwan topography, once the height of terrain replaced to 0, PV budget analysis demonstrated that the speed of steering flow will grow while the deflection will reduced. This phenomenon will let Typhoon penetrate Taiwan without deflection and deceleration.