論文ID: 2022-049
Typhoon Hagibis (2019) was a large and intense tropical cyclone that had significant societal impacts in Japan. It went through a period of explosive rapid intensification (RI), with an increase of maximum wind speed from 60 kt to 160 kt in 24 h, immediately followed by a secondary eyewall formation (SEF) and an eyewall replacement cycle (ERC). Operational forecasts from COAMPS-TC (Coupled Ocean/Atmosphere Mesoscale Prediction System – Tropical Cyclone) failed to capture Hagibis' explosive RI, peak intensity, and the associated inner-core structural evolution. Four COAMPS-TC sensitivity experiments, initialized at 1200 UTC 5 Oct. 2019, were conducted to study the impact of horizontal resolution on prediction of Typhoon Hagibis' RI and structure. Results indicate that rapid intensification of the storm to Category 4 intensity can be simulated with the finest grid spacing at 4-km, but use of 1.33-km for the finest grid spacing facilitates more realistic prediction of the explosive intensification rate, Category 5 peak intensity, and small inner core accompanying the RI. Our sensitivity experiments indicate that realistic simulation of Hagibis' SEF/ERC requires a very intense storm with a small inner core as a prerequisite for its occurrence; therefore the finest grid spacing at 1.33-km is a necessary but not sufficient to capture the SEF/ERC. The simulation of the RI and SEF/ERC is also sensitive to the resolution of the outermost grid, which has impacts on the storm's moisture distribution by modulating the flow of moist air from the deep tropics into the TC. While these results have implications for the grid configuration of operational models like COAMPS-TC, additional work is needed to gain systematic understanding of the physical processes associated with simulation of explosive RI and SEF/ERC.
