The structure and energetics of transient disturbances in the Northern Hemisphere wintertime circulation.

The hemispheric distributions of wintertime circulation statistics derived from the forecast fields of vertical motion are presented. The dominant features in the pattern for time-mean vertical velocity are consistent with the existence of thermally direct meridonial circulations over the entrance regions of the principle jet streams, and thermally indirect circulations over the jet exit regions. Rising motions in the transient disturbances are seen to display positive temporal correlations with temperature and geopotential height over the major oceanic storm track regions. On the other hand, the western portion of the continents and the adjacent oceanic areas are characterized by downward eddy transports of geopotential energy at 850 and 500 mb, as well as much reduced temporal correlations between the vertical motion and temperature fields. The regional character of the transient eddy statistics presented in this and earlier papers is interpreted in the light of the results from a recent modeling study by Simmons and Hoskins (1978) on the life cycle of nonlinear baroclinic waves. - from Author