Sensitivity of hurricane intensity and structure to boundary layer parameterizations in HWRF

Dr. Jun Zhang is a Scientist at the University of Miami. He is also associated with NOAA’s Hurricane Research Division. Dr. Zhang got his Ph. D. degree in Applied Marine Physics from the University of Miami in 2007. His research focus on hurricane structure and dynamics. Dr. Zhang has published over 90 peer-reviewed journal papers. Dr. Zhang has received CIMAS Gold Medal Award in recognition of his role in improving the operational Hurricane Weather Research and Forecasting (HWRF) model. He has also received AMS Banner I. Miller Award, NASA Award for Hurricane and Severe Storm Sentinel Group Achievement, and Aviation Laureate Award.
The planetary boundary layer (PBL) parameterization scheme in the Hurricane Weather Research and Forecasting (HWRF) model has been recently modified based on observations and numerical simulations. This study reviews the PBL schemes in all previous versions of the operational HWRF. How these different PBL schemes affect hurricane structure and intensity is evaluated using idealized HWRF simulations. The PBL scheme in the 2011 version of HWRF produces the weakest storm, while a modified scheme with a wind-speed dependent parameterization of vertical eddy diffusivity produces the strongest storm. The latest version of the PBL scheme with a mass flux configuration also produces a strong storm. The maximum storm intensity and intensification rate of the simulated storms vary with different PBL schemes. Reasons for these differences are discussed in the context of hurricane structure and dynamics. Further improvement in the current PBL scheme is recommended.