Structural characteristics of the subtropical jet stream and certain lower-stratospheric wind systems

Open Access
Publisher Website
Google Scholar
Abstract
Analyses of the wind field are presented for several caws, which illustrate the considerable variability in structure of the subtropical jet stream. Two cores of strongest wind are common, one lying in the break between the middle and subtropical tropopause and the other often lying above the subtropical tropopause. The layer of strongest wind on the cyclonic flank slopes upward toward north and is often identifiable as a discrete wind-speed maximum several kilometers above the polar-front jet stream. On the anticyclonic flank, the lower subtropical jet slopes downward toward south and is sometimes stronger than the higher-level layer of maximum wind. Although the broad-scale structure of the wind fields is qualitatively in accord with the solenoid field, large deviations from the thermal wind relationship are found in layers of restricted depth. Measured vertical shears are often double or triple the size of the thermal shear, and in certain regions the thermal and actual shears are of opposite sign. These deviations are shown to be associated with inertial effects arising from curvature of the flow, and from variations of curvature with height. An example is given illustrating the shallow filaments of strong wind sometimes found in the lower stratosphere above the tropospheric jet streams. These are not indicated by the thermal field, and are evidence of strong domination by inertial effects.

This publication has 0 references indexed in Scilit: