Sensitivity of numerical simulations of Typhoon Nuri (2008) to horizontal resolution and microphysical schemes: Implication for the role of adiabatic heating and upper-level processes in rapid intensification

Sensitivity experiments are conducted to examine the impact of model horizontal resolution, cloud microphysics schemes, and forecast leading time on numerical simulations of the genesis and early rapid intensification of Typhoon Nuri (2008) using an advanced research version of the Weather Research and Forecasting (WRF) model. With a single moment microphysical scheme, it is found that the simulation at coarse resolution (e.g., 12 km) better predicts Nuri's rapid intensification than that at a higher resolution (e.g., 4 km). Specifically, the simulation at the coarser resolution produces strong convective bursts and diabatic heating in the inner core region and also stronger warming in the upper atmosphere, leading to to a lower minimum sea level pressure.

Further diagnoses of the adiabatic heating indicate that the microphysical processes contribute the most to diabatic heating in the inner core region. Thus, an addition set of numerical simulations is conducted using a two-moment Morrison scheme. Results show a significant improvement in the simulations of Nuri's early rapid intensification at the 4-km resolution. In addition, later initialization (after genesis) also helps the model better forecast the early rapid intensification of Typhoon Nuri.

Given the complicated issues involve model resolution, cloud microphysics, and forecast leading time, detailed diagnoses are conducted to investigate the dynamic and thermodynamic processes that influence Nuri's rapid intensification. The roles of upper-level atmosphere and outflow layer processes are specifically addressed.