P1D.4 Air-sea enthalpy and momentum exchange at major hurricane wind speeds

Tuesday, 29 April 2008
Palms ABCD (Wyndham Orlando Resort)
Michael M. Bell, NPS, Monterey, CA; and M. T. Montgomery and K. A. Emanuel

Energy exchange at the air-sea interface is a crucial element in determining hurricane intensity. The ability to skillfully predict tropical cyclone intensity is critically dependent on meaningful and accurate parameterization of air-sea exchange of heat, moisture, and momentum in numerical models. Wind-speed dependent bulk aerodynamic formulas are often used to represent the turbulent fluxes associated with air-sea interactions; however, enthalpy and momentum exchange coefficients are largely unknown at major hurricane force wind speeds. Since direct measurements of turbulent fluxes in these conditions are extremely difficult, an alternate approach is proposed where the air-sea exchange is deduced from observational data using conservation of angular momentum and energy. The resulting formulation allows the use of remotely sensed and in situ measurements in and above the boundary layer to determine the air-sea exchange via a budget residual. Uncertainties and sensitivities using simulated hurricane data, and results from Hurricanes Isabel and Fabian (2003) will be presented.
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