Held, Isaac M. and Schneider, Tapio (1999) The Surface Branch of the Zonally Averaged Mass Transport Circulation in the Troposphere. Journal of the Atmospheric Sciences, 56 (11). pp. 1688-1697. ISSN 0022-4928 http://resolver.caltech.edu/CaltechAUTHORS:HELjas99
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The near-surface branch of the overturning mass transport circulation in the troposphere, containing the equatorward flow, is examined in isentropic and geometric coordinates. A discussion of the zonal momentum balance within isentropic layers shows that the equatorward flow at a given latitude is confined to isentropic layers that typically intersect the surface at that latitude. As a consequence of mass transport within the surface mixed layer, much of the equatorward flow occurs in layers with potential temperatures below the mean surface potential temperature. In the conventional transformed Eulerian mean formulation for geometric coordinates, the surface branch of the overturning circulation is represented in an unrealistic manner: streamlines of the residual circulation do not close above the surface. A modified residual circulation is introduced that is free from this defect and has the additional advantage that its computation, unlike that of the conventional residual circulation, does not require division by the static stability, which may approach zero in the planetary boundary layer. It is then argued that cold air advection by the residual circulation is responsible for the formation of surface inversions at all latitudes in idealized GCMs with weak thermal damping. Also included is a discussion of how a general circulation theory for the troposphere must be built upon a theory for the near-surface meridional mass fluxes.
|Additional Information:||© Copyright by American Meteorological Society 1999 (Manuscript received February 10, 1998, in final form July 23, 1998) We wish to express our thanks to Robert Hallberg, Paul Kushner, and an anonymous reviewer, whose comments on an earlier draft of this paper led to significant improvements in the final version.|
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|Deposited On:||20 Jul 2006|
|Last Modified:||26 Dec 2012 08:57|
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