On the structure of concentrated atmospheric vortices in a gradient wind regime and its motion on synoptic scales

Abstract

Three-dimensional concentrated atmospheric vortices with vertical extensions throughout the whole troposphere and diameters corresponding to the sub-synoptic gradient wind regime are studied in this work. Hurricane-like vortices are representative examples for this type of atmospheric flow phenomena. Research in recent years have shown that the complex interplay between atmospheric processes acting on different time and length scales strongly affect the motion, structure and development of hurricane-like vortices. It is well known that these interacting processes arise among others from the earth rotation, the environmental flow and small scale convective systems. It is against this background that this dissertation aims to derive reduced model equations that elucidate how scale interactions influence the motion and structure of concentrated atmospheric vortices. In particular, reduced model equations are derived that describe how the mesoscale structure of the vortex itself affects the synoptic scale vortex motion and vice versa, while taking the influence of a vertically sheared environmental flow and diabatic effects due to moisture conversion processes into account. For the derivation of such reduced model equations multiple scales asymptotic analysis based on matched asymptotic expansions are used. For various reasons a better understanding of the mechanisms determining the motion and structure of atmospheric vortices is of great interest. In operational use, for instance, an accurate forecast of the vortex trajectory is needed to avoid potential disasters caused by a landfalling storm systems. The reduced model equations derived in this work can be used to design hurricane track models that might contribute to improvements of hurricane track forecasts.