398
NEWELL AND MILLER
1
-.5
2
o
(¥V'] * [utV*])cos!
agoa
G _=~ Teas’
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Z=1- os G30 88 ?
The
symbol
T represents the rate of diabatic heating.
The other
symbols have their usual meteorological significance. Cross sections
of the eddy heat and momentum transports and mean zonal wind and
temperature were constructed from the data reported by Buch’® and
Peixoto'4
for
the
region below 100 mb and from data reported by
Murakami’ and Peng!* and other, unpublished data for the levels of
100 mb and above. The diabatic heating, T, was obtained from the work
of Davis® for the 5- to 10-km region and from the work of Kennedy’ for
the 10- to 30-km region.
The terms in the equation for V were then evaluated at grid points
2.5 km apart in height and 10 degrees apart in latitude. The final re-
sults appear in Fig. 2. It is immediately evident that a coherent threecell structure is present with small equatorward velocities in middle
latitudes in both seasons and a larger poleward flow in equatorial
regions. The magnitudes in the lower stratosphere are very much
lower than those given by Oort.*4 The possible error in the results
depends on the accuracy of the cross sections; therefore it is difficult
to specify the error quantitatively. Those involving wind velocities
are likely to be biased because of the selectivity introduced by the
early loss of balloons at high wind speeds (see Ref. 31). In addition,
values in the vicinity of the tropics are no doubt dependent on the
26-month oscillation. Latent heat is not included in the diabatic-heating
distributions used, but this does not affect the values calculated for the
lower stratosphere. In fact, a comparison of the magnitudes of the
two terms in the numerator of the equation for V showsthat, although
the heat-forcing function predominates or is very important in the
determination of V at 5 km, its importance decreases with height. In
the 12.5- to 17.5-km calculations, the momentum-forcing function is
predominant (in numerator and denominator); therefore thermal effects
play a secondary role. This pattern perhaps is to be expected since,
as we noted earlier, the tropospheric heat engine is driven by the
heating effects whereas the lower stratosphere appears to be dynamically coupled to the troposphere.
As far as trace substances are concerned, the preceding findings
seem to imply that the mean meridional circulations do not contribute
Significantly to the mass budget in the middle-latitude lower strato-