It moves slowly up or down as it travels to conserve potential temperature; in other words, it clings to its "potential temperature surface" or isentropic surface
(assuming heat isn't being added or removed).
Screenshot of instructor's lecture video annotations on map of pressure contours on 300-K isentropic surface
PV cutoffs Structures of stratospheric air Wernli and ([absolute value of PV] > 2 PVU) Sprenger that are detached from the main (2007) stratospheric body on a specific isentropic surface
While not discussed in the abovementioned tropospheric vortex studies, the edge of the tropospheric vortex can (as in the stratosphere) be defined from potential vorticity contours on an isentropic surface
or (equivalently) potential temperature on a surface of constant potential vorticity (Hoskins et al.
We then derived the zonally integrated meridional mass flux above a specific isentropic surface [[THETA].
Below are details of the methods used to derive meridional mass circulation indices with various isentropic surfaces as the bottom level and the cold temperature area indices from these daily data.
Constant isentropic surfaces
are depicted within the successive profiles in 5-K intervals from 310 to 380 K.
The low ozone contents at lower levels result from the presence of high pressure at the upper troposphere in the surrounding of the polar edge, which leads to adiabatic vertical displacement of isentropic surfaces
, as it has been suggested by other authors (Koch et al.