Structure of Environmental Turbulence and its Relation to Turbulent Elementary Vortices

点击翻译按钮获取中文摘要

The structure and generation mechanism of large-scale elementary vortices such as tornadoes and polar lows in the atmosphere are clarified by high-resolution numerical simulations. A tornado spawned by a supercell storm is shown to develop along a gust front where verticity associated with the horizontal shear is concentrated and is further stretched by the storm updraft. Polar lows are shown to develop through baroclinic instability and latent heat release. When the baroclinicity is small a nearly axisymmetric vortex similar to a typhoon develops. When the baroclinicity is large, on the other hand, a meso-scale low accompanied with a comma-shaped cloud pattern develops. A laboratory experiment on a bathtub vortex show that the radial profile of the tangential velocity depends significantly on the characteristics of the botton boundary layer, which explains a wide variety of velocity distribution in atmospheric vorticesAlso studied are statistical characteristics of turbulence under the effect of density stratification and earth's rotation with the beta-effect by a theoretical consideration and a numerical experiment. It is shown that the density stratification tends to suppress the Rhines effect to generate zonal mean flows. A self-similar solution for a decaying divergent rotating turbulence was foundFinally, turbulent transport processes of carbon dioxide through the air-sea interface are studied by laboratory and numerical experiments. It is found that the transport is dominated by large-scale elementary vortices called surface renewal vortices and the exchange coefficient is proportional to a square root of the generation frequency of the surface renewal vortices