Geography Reference
In-Depth Information
Fig. 10.5
Schematic Eulerian mean meridional circulation forced by a vertical gradient in eddy
momentum flux convergence.
Thus, this term is proportional to the vertical derivative of the meridional vorticity
flux. To interpret this eddy forcing physically, we suppose as shown in Fig. 10.5 that
the momentum flux convergence (or the vorticity flux) is positive and increasing
with height. This will be true
in th
e Northern Hemisphere troposphere poleward of
the core of the jet stream, as u
v
tends to be poleward and to reach its maximum
near the tropopause at about 30
◦
(at the core of the me
an je
tstream) as shown
in Fig. 10.6. For this configuration of momentum flux ∂
2
u
v
∂y∂z <
0
in the
midlatitude troposphere, which again drives a mean meridional cell with χ<0.
From (10.11) it is clear that the Coriolis force of this induced indirect meridional
Observed northward eddy momentum flux distribution (m
2
s
−
2
) for Northern Hemisphere
winter. (Adapted from Schubert et al., 1990.)
Fig. 10.6
