Heat and turbulent kinetic energy budgets for surface layer cooling induced by the passage of Hurricane Frances (2004)

Heat and turbulent kinetic energy budgets of the ocean surface layer during thepassage of Hurricane Frances were examined using a three-dimensional hydrodynamicmodel. In situ data obtained with the Electromagnetic-Autonomous Profiling Explorer(EM-APEX) floats were used to set up the initial conditions of the model simulation andto compare to the simulation results. The spatial heat budgets reveal that during thehurricane passage, not only the entrainment in the bottom of surface mixed layer but alsothe horizontal water advection were important factors determining the spatial pattern ofsea surface temperature. At the free surface, the hurricane-brought precipitationcontributed a negligible amount to the air-sea heat exchange, but the precipitationproduced a negative buoyancy flux in the surface layer that overwhelmed the instabilityinduced by the heat loss to the atmosphere. Integrated over the domain within 400 kmof the hurricane eye on day 245.71 of 2004, the rate of heat anomaly in the surfacewater was estimated to be about 0.45 PW (1 PW = 1015 W), with about 20% (0.09 PWin total) of this was due to the heat exchange at the air-sea interface, and almost all theremainder (0.36 PW) was downward transported by oceanic vertical mixing. Shearproduction was the major source of turbulent kinetic energy amounting 88.5% of thesource of turbulent kinetic energy, while the rest (11.5%) was attributed to the wind stirringat sea surface. The increase of ocean potential energy due to vertical mixing represented7.3% of the energy deposited by wind stress.