Influence of Topography on Tropical Cyclone Track - Idealized Simulations

Both observational and numerical studies have shown that a tropical cyclone (TC) tends to deflect when approaching and passing over a mesoscale mountain range. In this study, the orographic effect on TC track deflection during the passage is investigated by conducting idealized experiments with specific designs in a full-physics model with 3-km horizontal resolution. Different parameters describing the idealized vortex and mountain, including TC intensity, strength, size, radius of maximum wind, translation speed, mountain height, slope and range, are used in our investigation. These idealized experiments provide information on how TC movement is influenced by topography, as well as an opportunity to investigate the key mechanisms causing the topographic deflection of TC track.

Consistent with the results presented in previous studies, we find that a westward-moving TC approaching the central topography deflects to the north before encountering the mountain, to the south when crossing over the mountain, and to the north again after passing the mountain. Sensitive experiments to the aforementioned parameters are conducted to find which key variable(s) determine the left or right track deflection and the magnitude of track deflection. The results suggest that some parameters (such as the TC translation speed and mountain slope) are playing more important roles in causing the track deflection, while others (such as the mountain height and TC size) in determining the deflected direction of TC movement. This implies that the direction and magnitude of the deflected track are affected by different flow and parameter regimes. These sensitive experiments shed some lights on key dynamical mechanisms corresponding to different topography-induced deflection of TC tracks.