Impact of the atmospheric boundary layer on eyewall mesovortices of hurricanes

In this study, the multiple nested state-of-the-art Weather Research and Forecast (WRF) model is used to investigate the impact of the planetary boundary layer (PBL) processes on the formation and development of eyewall mesovortices of hurricanes. Hurricane Isabel (2003) was simulated by a series of numerical experiments with different PBL schemes including the Yonsei University (YSU), Mellor-Yamada-Janjic (MYJ), Mellor-Yamada-Nakanishi-Niino 2.5 level (MYNN 2.5), and Mellor-Yamada-Nakanishi-Niino 3 level (MYNN 3) schemes. The simulations show that the PBL scheme has an important bearing on mesovortices and other organized structures in the vicinity of eyewall. The impact of PBL schemes on hurricane intensity is realized through a combined effect from the direct parameterized turbulent fluxes and from the indirect fluxes resulted from the resolved processes. The analyses show that the PBL processes can demolish the instability for generation of mesovortices through broadening eyewall potential vorticity ring due to the strong mixing and generating high wavenumber of vortex Rossby waves.