Influences of Tropical Cyclone Fullness on Secondary Eyewall Formation in Idealized Numerical Simulations

Four idealized TC experiments using version 3.9.1 of the Weather Research and Forecasting (WRF-ARW) model (Skamarock et al., 2008) are conducted. The model domain utilizes a triple-nested configuration (361 × 361, 301 × 301, 361 × 361), with horizontal grid resolutions of 18 km, 6 km, and 2 km, respectively. The outermost domain employs symmetric boundary conditions, while the inner domains utilize vortex-following. The model consists of 45 layers vertically with the height of the lowest 10 layers below 1.5 km to enhance the vertical resolution in the boundary layer for the boundary layer response is a critical factor influencing SEF. Taking into account the potential influence of β-effect on SEF, all experiments are conducted on the -plane at 20°N. The initial sea surface temperature (SST) is set to 29°C over a quiescent ocean, and the initial large-scale thermodynamic conditions are based on Dunion et al. (2011). The physical parameterization schemes employed include the Thompson scheme (Thompson, 2004, 2008) for cloud microphysics, Rapid Radiative Transfer Model scheme (Mlawer et al., 1997) and the Dudhia scheme (Dudhia, 1989) for longwave and shortwave radiation with the cloud-radiation feedback mechanism activated to promote the formation and development of spiral rainbands in the outer eyewall region (Wang and Li, 2024), Monin-Obukhov scheme (Janjić, 1996) for surface fluxes, and Mellor-Yamada-Janjic scheme (Janjić, 2002) for planetary boundary layer parameterization. The Kain-Fritsch cumulus parameterization scheme (Kain, 2004) is applied exclusively in the outermost grid.