D. Peters et Dw. Waugh, INFLUENCE OF BAROTROPIC SHEAR ON THE POLEWARD ADVECTION OF UPPER-TROPOSPHERIC AIR, Journal of the atmospheric sciences, 53(21), 1996, pp. 3013-3031
The characteristics of the poleward advection of upper-tropospheric ai
r are investigated using meteorological analyses and idealized numeric
al models. Isentropic deformations of the tropopause during Northern H
emisphere winter are examined using maps of Ertel's potential vorticit
y together with contour advection calculations. Large poleward excursi
ons of upper-tropospheric air are observed during Rossby wave breaking
events. These ''pole-ward'' breaking events occur in regions of diffl
uence (over the eastern Atlantic Ocean-Europe region, and over the eas
tern Pacific Ocean-North America region), and the evolution of the tro
pospheric air depends on the local, meridional shear: in anticyclonic
(or weak cyclonic) shear the tropospheric air tilts downstream, broade
ns, and wraps up anticyclonically, whereas in cyclonic shear the tropo
spheric air tilts upstream, thins, and is advected cyclonically. The r
ole of ambient barotropic flow is further examined by considering the
how in two numerical models: a planar, equivalent-barotropic, contour
dynamics model and a simplified general circulation model. In both mod
els, the variation of the poleward wave breaking with the zonal and me
ridional shear is consistent with that in the analyses.