Numerical simulations of the wake of Kauai with implications for the Helios flights

High resolution numerical simulations of the wake of the Hawaiian island of Kauai are performed for various idealized and observed upstream atmospheric profiles. The wake is shown to extend very large distances downstream, and the wake geometry depends on the structure of the upstream wind profile, and to a lesser extent, the height of the trade wind inversion. In most cases, a sharp transition zone in velocity and temperature is observed at the wake boundaries; indeed this transition zone helps to define the wake boundary. The associated shears in the transition zones can be large enough to induce instabilities locally, and cause the wake lateral boundaries to be transitory and turbulent. The instabilities are not observed in the coarser model simulations, indicating the necessity for high resolution (of at least 200 m horizontally) in numerical studies of island wakes. Application of the simulation results will be discussed in the paper.