Loop Current Mixed Layer Energy Response to Hurricane Lili (2002). Part II: Idealized Numerical Simulations

Abstract

n this second part of a two-part study, details of the upper-ocean response within an idealized baroclinic current to a translating tropical cyclone are examined in a series of nonlinear, reduced-gravity numerical simulations. Based on observations obtained as part of a joint NOAA?National Science Foundation (NSF) experiment in Hurricane Lili (2002), the preexisting ocean mass and momentum fields are initialized with a Gulf of Mexico Loop Current?like jet, which is subsequently forced by a vortex whose wind stress field approximates that observed in the Lili experiments. Because of 1) favorable coupling between the wind stress and preexisting current vectors, and 2) wind-driven currents flowing across the large horizontal pressure gradient, wind energy transfer to the mixed layer can be more efficient in such a regime as compared to the case of an initially horizontally homogeneous ocean. However, nearly all energy is removed by advection and wave flux by two local inertial periods after storm passage, consistent with the observational results. Experiments are performed to quantify differences in one-dimensional and three-dimensional linearized approximations to the full model equations. In addition, sensitivity experiments to variations in the initial geostrophic current structure are performed to develop a parameter space over which a significant energy response could optimally be observed.