ATMOSPHERIC TRANSPORT PROCESSES
100
30 __—=Z8£
35
390
380
.
370
ib
360
45
a
00
LZ
5
<
60
VT
wo
~
a,
f
455
<
~
350
~ ‘
65 ™~
SX
. \
340
=-
770
300
=
330
400
500
3
55
25
600
30
GRB
30
310
700
800
40
320
35,
300
=
20
PLA
CBI
TOP
OKC
Fig. 4—Cross section through the troposphere and lowey stratosphere
from Green Bay (GRB), Wis., to Oklahoma City (OKC), Okla., at 00
GCT on Nov. 22, 1962. Thin lines are isotherms of potential temperature (°K). Heavy lines are isotachs (mps); these are dashed in regions
with missing data. Siable regions below 400 mb are shaded. Coded
tropopauses are indicated by heavy dots.
Splitting of the jet stream was observed in previous case studies
of radioactive fallout.’-4:’? This indicates that part of the upper tropoSpheric air that moves through the jet stream is caught in the anti-
cyclonic circulation of the lower troposphere. The dynamic causes for
this splitting are not yet certain. Conceivably, dynamic instabilities
in jet streams on an isentropic surface may play an important role.
Magnitude of Isentropic Transport
It is difficult to estimate the total amount of stratospheric air descending into tropospheric regions in a jet-stream system as shown in
Figs. 3a and 3b. The main problem is finding a suitable procedureto