IDEALIZED SIMULATIONS OF THE INNER CORE BOUNDARY LAYER STRUCTURE IN A LANDFALLING TROPICAL CYCLONE. PART Ⅰ: KINEMATIC STRUCTURE

作者：GABRIEL J.WILLIAMS JR.

摘要：The effects of coastal topography and coastal location in the distribution of boundary layer winds in the inner core of mature tropical cyclones are examined using a high-resolution multi-level model. In these numerical simulations, the evolution of the tropical cyclone boundary layer(TCBL) is studied in storm-relative coordinates, and in lieu of an actual steering current moving the model vortex, the position of the land-sea interface was shifted through the grid domain at a constant speed with separate surface boundary conditions specified over the land and ocean areas. It is shown that the presence of a coastal boundary produces land-induced asymmetries(along with an internal boundary layer) due to the asymmetric structure of surface drag. This land-induced asymmetry is found in both the azimuthal and radial wind field at landfall. For a moving storm, nonlinear advective interactions between storm-induced asymmetries and land-induced asymmetries can generate a lowlevel vorticity band ahead of the hurricane. When the storm motion vector has a component that is perpendicular to the coastal boundary, the interaction between this band and the mean vortex leads to a temporary weakening and re-intensification cycle. Furthermore, it is shown that the relative magnitude of the land-induced asymmetry depends upon the terrain slope and the terrain height such that the land-induced asymmetry dominates over the motion-induced asymmetry for elevated terrain. These results underscore the specific differences in boundary layer evolution and intensity evolution for hurricanes interacting with complex topographical features.

發文機構：Department of Physics and Astronomy

關鍵詞：HURRICANETROPICALCYCLONElandfallingHURRICANETROPICALCYCLONEBOUNDARYlayer

分類號： P444[天文地球—大氣科學及氣象學]