Numerical experiments on cyclone development by interaction of convective heating and baroclinic instability

Abstract

``Polar lows'' are cyclones with the horizontal scale of 200-1000 kmthat develop over high-latitude oceans in winter.Since they exhibit a wide variety of cloud patterns such as quasi-axisymmetric spiral shape and comma shape,their development mechansim have attracted a number of meteorologists.Previous studies, using linear analysis,pointed out that one of the possible candidates isan interaction of convective heating and baroclinic instability.In order to understand this mechanism with respectto the detailed structure and dynamics of the vortex,we have performed a high-resolution numerical experiment on polar low developments within simplified environments, where the convective heating is incorporated in a much more reliable manner than in the previous studies.Our result shows that a spiral cloud pattern is formed in an environment without baroclinicity, while a comma cloud pattern, in a strong baroclinic environment.The relationship among their growth rate, structure and development mechanismis also clarified.When the baroclinicity is weak, for example, a vortex has the tendency to move northward.