Comparison of Turbulent Transport Schemes for Heavy Precipitation Associated with Typhoon Lan (2023)

On 15 August 2023, Typhoon Lan (2023) struck the Kinki region in western Japan, bringing record precipitation to the Kinki and Chugoku regions. This study investigates a turbulent transport scheme that can predict precipitation more accurately using the Weather Research and Forecasting model. The turbulent transport schemes compared are the Yonsei University scheme, the Mellor–Yamada–Nakanishi–Niino (MYNN) scheme, and the eddy-diffusivity mass-flux (EDMF) scheme, which is a blend of the MYNN scheme and a mass-flux scheme. Simulations are performed for a domain with a horizontal resolution of 5 km. The results show that the simulated track and central pressure of the typhoon over the Sea of Japan vary depending on the turbulent transport schemes, the MYNN scheme reasonably reproduces the distribution of heavy precipitation areas, the EDMF scheme even improves the quantitative prediction of precipitation, and the formulation of the turbulent length scale is also a key factor for the better prediction using the EDMF scheme. The EDMF scheme is expected to become a leading turbulent transport scheme in operational forecast models.