Geography Reference
In-Depth Information
Fig. 5.7
Streamlines of the secondary circulation forced by frictional convergence in the planetary
boundary layer for a cyclonic vortex in a barotropic atmosphere. The circulation extends
throughout the full depth of the vortex.
denser than the environmental air. As a result the interior secondary circulation will
decrease with altitude at a rate proportional to the static stability. This vertically
varying secondary flow, shown in Fig. 5.8, will rather quickly spin down the vor-
ticity at the top of the Ekman layer without appreciably affecting the higher levels.
When the geostrophic vorticity at the top of the boundary layer is reduced to zero,
Fig. 5.8
Streamlines of the secondary circulation forced by frictional convergence in the planetary
boundary layer for a cyclonic vortex in a stably stratified baroclinic atmosphere. The circu-
lation decays with height in the interior.
