Sensitivity of Numerical Simulations of the Early Rapid Intensification of Hurricane Emily to Cumulus Parameterization Schemes in Different Model Horizontal Resolutions

Abstract

A series of numerical experiments are conducted to examine the sensitivity of the numerical simulation of Hurricane Emily’s (2005) early rapid intensification to the cumulus parameterization schemes in the advanced research version of Weather Research and Forecasting (WRF) model at different horizontal resolutions. Results indicate that the numerical simulations are very sensitive to the choices of cumulus schemes at 9 km grid spacings. Specifically, with different cumulus schemes, the simulated minimum central sea level pressure (SLP) varies by 41 hPa during the 54 h forecast period. In contrast, only about 10 hPa difference is produced in minimum central SLP by varying planetary boundary layer (PBL) parameterization schemes in the same simulation period. Physical and dynamic mechanisms associated with this sensitivity are investigated. It is found that the intensity of the simulated storm depends highly on the magnitude and structure of surface latent heat flux and convective heating rate over the storm eyewall. The use of cumulus schemes is helpful for the model to reproduce those favorable conditions that cause the storm deepening. However, at 3 km resolution, the cumulus schemes do not result in any notable difference in the storm intensity and track forecasts. Only a slight difference is found in the simulated storm precipitation structure. Compared with cumulus schemes, the PBL schemes have significant impacts on Emily’s intensity forecast at 3 km resolution; the minimum central SLP varies by 37 hPa with the use of a different PBL scheme in the WRF model.