Geoscience Reference
In-Depth Information
Figure 4.1.
The meridional structure of the tropopause. The potential vorticity
discontinuity tropopause is shown by heavy solid lines, with the stratosphere shaded.
The primary frontal zones are bounded by heavy dotted lines. The 40 m s
−1
isotach
(thin dashed line) encircles the cores of the primary jet streams (Ja, Arctic; Jp, Polar;
Js, Subtropical). The secondary (thermal) tropopause is indicated by the heavy dashed
line. Major tropospheric and stratospheric airmasses, tropopause surfaces, and selected
wind systems are labeled. Cross sections at any given time along any given longitude
may differ greatly from this idealized model (from Shapiro et al.,
1987b
, by permission
of AMS).
Boville, and McClellen,
1955
; Penner,
1955
; Galloway,
1958
; McIntyre,
1958
).
Operational analyses were made by frontal contour charts showing the location of
fronts at the 1,000-, 700- and 500-hPa levels. The northernmost fronts represented
“Arctic fronts.” These analyses served as the basis for numerous climate studies.
M. Serreze, A. Lynch, and M. Clark (
2001
) provide a summary of some of
the evolving thought regarding high latitude fronts. Arctic fronts were very much
evident in vertical cross sections presented in early synoptic atlases (Boville,
MacFarlane, and Steiner,
1959
). More modern studies using aircraft data collected
during the winter season under the Arctic Gas and Aerosol Program (Shapiro et al.,
1984
; Shapiro,
1985
; Raatz et al.,
1985
; Shapiro, Hampel, and Krueger,
1987b
)
left little doubt regarding the reality of separate Arctic jet streams. These and other
observations were used by Shapiro et al. (
1987b
) in a “revised” three-front model
(
Figure 4.1
), which harks back to the Canadian scheme.
