GENERAL CIRCULATION OF THE LOWER STRATOSPHERE
401
cording to the mechanisms discussed by Eliassen and Palm® and
Van Mieghem,*” then there is some circumstantial evidence that it
changes with season and has a maximum in the early part of the year.™
Let us remember that the preceding paragraph is speculative (it
may be useful to guide us in further analysis) and return to the IGY
data. From these data various terms in the energy budget of the lower
stratosphere (100 to 30 mb) can be estimated. Data from 230 upper
air stations have been used. From individual-station data, threemonth seasonal averages are calculated for temperature, zonal and
meridional wind components, and geopotential in addition to variances
and covariances between the various quantities. The three-month
means are then plotted on maps, isolines are drawn, and grid-point
values are read for the calculation of zonal averages. The entire
procedure is carried out for the 00Z and 12Z observations independently. Vertical velocities are calculated by the adiabatic method
from
the
daily
station data; observations 24 hr apart are used.”!
Covariances between the vertical velocities and other quantities are
calculated and treated as above. Certain of the quantities in the energy
budget have already been published!’**' for portions of the IGY. One
of the authors of this paper (A. J. Miller) is presently engaged in a
study of the vertical-flux processes in the region for the entire IGY
period, and the values of quantities involving vertical velocity presented
in Table 3 represent preliminary results from this study. Values for
Table 3-—SEASONAL VARIATION OF THE ENERGY BUDGET OF THE LOWER
STRATOSPHERE [100 TO 30 MB (16 TO 24 KMD] IN TRANSIENT-EDDY TERMS
Ergs/cm2/sec
July—Sept.
1957
Convergence
of kinetic
energy
Convergence
of heat
energy
Convergence
of potential
energy
Conversion
of kinetic
to potential energy
Generation
of zonal available
potential energy®
Conversion of
mean zonal
available potential
energy to eddy
potential energy
(horizontal part)!
Oct.—Dec.
1957
Jan.-—Mar.
1958
Apr.—June
1958
July—Sept.
1958
Oct.—Dec.
1958
—0.23
0.16
~0.40
—0.30
0,18
0.98
—28.3
—23.9
—35,8
—33.3
1.1
—62.7
3.3
-1.3
13.4
12.0
9.7
4,2
4.7
7.0
5.2
10,2
3.2
13.3
—81t
-—77t
—17.0
—14.5
—37*
—10.4
—13.9
.
*July.
{ January.
TApril.
Le