Storm tracks in a warmer climate: sensitivity studies with a simplified global circulation model

Abstract

 A simplified global circulation model is used to analyse a greenhouse warming experiment simulated by a comprehensive general circulation model. The given GCM scenario and control climates are assimilated by the simplified model using a dynamical relaxation technique. Two sets of sensitivity experiments investigate the influence of upper and lower tropospheric changes in baroclinicity on the Northern Hemisphere winter storm tracks. The results show that the three-dimensional structure of both the background flow and the changes in baroclinicity are important for the behaviour of mid-latitude eddy activity in relation to modifications of the baroclinicity. In general, the mid-latitude eddy activity is more sensitive to lower than to upper level changes in baroclinicity. The results further suggest that the simulated storm track changes in the GCM scenario are dominated by local modes of baroclinic instability.