ON THE DYNAMICS OF A STORM TRACK

An idealized primitive equation model is used to determine the factors controlling the dynamics and maintenance of eddy activity in a storm track. The results show that localized regions of enhanced baroclinici ty do not necessarily lead to localization of eddy activity. By studyi ng the energetics of the storm track, it is shown that while baroclini c conversion does indeed correlate with the region of maximum baroclin icity, it is the downstream radiation of energy through the ageostroph ic geopotential fluxes which acts as a trigger for the development and maintenance of eddy activity over less baroclinic regions, extending the region of eddy activity much further downstream from the region of high baroclinicity. Examples of eddy life cycles are given that show that convergence and divergence of ageostrophic fluxes can dominate ba roclinic and barotropic conversion, especially in regions with weak ba roclinicity. Factors that may limit the zonal extent of a storm track are discussed. Evidence of downstream development over the wintertime Pacific storm track based on analyses of ECMWF data is also shown.