Simulation of an intense tropical cyclone in the conformal cubic atmospheric model and its sensitivity to horizontal resolution

Abstract

In this study, we evaluated the Conformal Cubic Atmospheric Model's (CCAM) ability to simulate the characteristics of severe Tropical Cyclone (TC) Hina, which occurred in the Southwest Pacific in 1985. We compared the model's performance using both a quasi-uniform grid and a variable-resolution grid to investigate differences in the representation of TC Hina's properties, such as tracks and intensity. We further examined the impact of horizontal resolutions (50 km, 25 km, and 12.5 km) on the wind structure, surface fluxes, and precipitation. Our findings indicate that CCAM reasonably reproduces the TC Hina's track, aligning with IBTrACS and ERA5 data. Higher resolutions in both quasi-uniform and variable resolution configurations result in improved representation of Hina's intensity, with the 12.5 km resolution showing the best performance. Both grid configurations show similar time series of maximum wind speed (V_max) and minimum sea level pressure (SLP_min). The model is able to accurately represent a range of synoptic meteorological phenomena surrounding the TC centre, as well as the moisture sources feeding into the inner-core of the TC at higher resolutions. Furthermore, we find that the simulated structures of the TC, including primary and secondary circulations, surface fluxes, and precipitation are strongly influenced by horizontal resolution. Our findings suggest that higher resolutions promote greater precipitation and larger latent heat fluxes near the TC centre (facilitating TC intensification). While challenges remain in simulating TCs over the entire Australasian CORDEX domain, the study demonstrates CCAM's capability to simulate intense TCs at high resolution. These findings provide valuable insights into the understanding of how CCAM can be effectively utilised for regional climate projections of TCs.