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Zonal mean circulations for two conserved meridional coordinates
Author(s) -
Egger Joseph,
Hoinka KlausPeter
Publication year - 2014
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.2373
Subject(s) - zonal and meridional , mean flow , potential vorticity , circulation (fluid dynamics) , troposphere , latitude , adiabatic process , atmospheric circulation , meridional flow , climatology , zonal flow (plasma) , geology , vorticity , stream function , atmospheric sciences , potential temperature , flow (mathematics) , mechanics , physics , geodesy , thermodynamics , turbulence , vortex , plasma , quantum mechanics , tokamak
While many investigations of the atmospheric zonal mean circulation have been published using various vertical coordinates, this article concentrates on meridional coordinates other than latitude. Potential vorticity q and potential temperature θ are selected, with height as the vertical coordinate. Both q and θ are conserved in adiabatic frictionless flow. Although this helps in the interpretation of the results, both choices are problematic because of contortions in the contours. The related problems are solved by integrating over suitable zonal tubes. The isertelic mean circulation exhibits global cells in the upper troposphere and separate shallow hemispheric cells near the ground. Mean q fluxes are derived from the mass circulation. The mean circulation in ( θ , z ) coordinates is similar to that in ( ϕ , θ ) coordinates and has hemispheric direct cells. Mean θ fluxes follow from that. Both circulations are forced, in the sense that they can be derived and understood if the zonal mean heating is known. This is demonstrated by explaining, for example, the equatorward surface flow in ( θ , z ) coordinates and the shallow boundary‐layer circulation in the isertelic system.