Challenges in Coupled Air-Sea-Land Modeling of Hurricanes and Applications in Coastal and Urban Environment

Landfall hurricanes post a great challenge in forecasting winds, rain, waves and storm surge for coastal and urban hazard planning. The extreme active Atlantic hurricane seasons in 2004-2005 have highlighted the urgent need for a better understanding of the factors that contribute to hurricane structure and intensity and for development of the corresponding advanced hurricane prediction models to improve hurricane forecasts. This talk will provide an overview of the challenges and recent advances in state-of-the-art of the next-generation hurricane prediction models. The extreme high winds, intense rainfall, large ocean waves, and copious sea spray in hurricanes push the surface-exchange parameters for temperature, water vapor, and momentum into untested regimes. The most recent modeling effort is to develop and test a fully coupled atmosphere-wave-ocean modeling system that is capable of resolving the eye, eyewall, and rainbands in a hurricane at ~1 km grid resolution. The new challenges for these very high resolution models are the corresponding physical representations at 1-km scale, including microphysics, sub-grid turbulence parameterization, atmospheric and ocean boundary layers, physical processes at the air-sea interface with surface waves, land surface property among others. The lack of accurate initial conditions for high-resolution hurricane modeling presents another major challenge. Improvements in initial conditions rest on the use of more airborne and remotely sensed observations in high-resolution assimilation systems and on the application of advanced assimilation schemes to hurricanes. This study will address some of these new challenges using high-resolution model simulations of hurricanes that were observed extensively by two recent field programs, namely, the Coupled Boundary Layer Air-Sea Transfer (CBLAST)-Hurricane in 2003-2004 and the Hurricane Rainbands and Intensity Change Experiment (RAINEX) in 2005. Potential applications for coastal and urban environment will be discussed.