Simulation of intensity and structure of hurricane Irene: effects of microphysics, aerosols and model resolution

The intensity of Hurricane Irene (2011) was incorrectly predicted by most of operative TC forecast models. Specific feature of this hurricane was an increase in the maximum wind during a substantial time after reaching of minimum surface pressure. No model with bulk-parameterization schemes were managed to predict the increase in the wind speed along with the increase in the minimum surface pressure. In this study evolution of Irene is simulated using WRF model with a new version of the spectral bin microphysics (SBM) developed in the Hebrew University of Jerusalem. The model resolution of the fine innermost grid was about 1 km. It is shown that increase in model resolution leads to better representation of dynamics and microphysics of clouds and of the related latent heat release and leads to increase in the TC intensity. The accounting for ocean coupling becomes absolutely necessary to get realistic intensity of TC in high resolution simulations. The simulations indicate that WRF/SBM is able to reproduce the time changes of both minimum pressure and maximum wind. Effects of aerosols (including sea spray effects) on cloud microphysical composition, cloudiness structure and TC intensity are discussed.