Drag and enthalpy coefficients at major hurricane wind speeds

Wind-speed dependent bulk aerodynamic formulas are often used to represent the turbulent transfer of enthalpy and momentum at the air-sea interface. However, enthalpy and momentum exchange coefficients are largely unknown at major hurricane force wind speeds. Because direct measurements of turbulent fluxes in these conditions are extremely difficult, an alternative method for deducing these fluxes and the corresponding coefficients of transfer may be carried out using a budget residual method for angular momentum and total energy. The methodology is first validated using both axisymmetric and three-dimensional high resolution hurricane simulations. The method is then applied to real observational data using a new spline-based, variational analysis tool that incorporates both remotely sensed and in situ measurements in order to furnish a maximum likelihood estimate of the axisymmetric hurricane structure. Results from six research flights into Hurricanes Isabel and Fabian (2003) during the CBLAST program will be presented along with a discussion of the sensitivities and uncertainties of this methodology.