Relationship between cyclone tracks, anticyclone tracks and baroclinic waveguides

Abstract

The disturbances assume the form of waves, elongated in the meridional direction, with a mean wavelength of 4000 km, a westward tilt with height, and a mean eastward phase propagation of 12-15 m s-1. Over the continents, and especially along the eastern slopes of the Rockies and the Tibetan Plateau, the waves show marked departures in structure and evolution from those over the oceans. In particular, we find evidence of a systematic influence of the terrain in steering the disturbances at the 1000 mb level relative to those in the middle and upper troposphere. The disturbances propagate along distinct, zonally oriented waveguides. Paths of positive and negative 1000 mb height anomalies propagating through the baroclinic waveguides are compared and found to be very similar. However, the paths of the corresponding cyclones and anticyclones on conventional synoptic charts exhibit a sharply contrasting behavior; the former being oriented from southwest to northeast and the latter from northwest to southeast, in agreement with synoptic experience. Differences in the orientation of cyclone tracks, anticyclone tracks and baroclinic waveguides are explained on kinematic grounds, as a reflection of the changes in the climatological mean basic state that the waves encounter as they propagate eastward through the baroclinic waveguides from the eastern continents toward the midoceans. -from Authors