INTERNATIONAL SYMPOSIUM ON TRACE GASES AND RADIOACTIVITY
3805
40
~~—~—--— SSN
—
a —~ NNN
35/-|
ee 27/28. 8.56
|
22-3h
Experimental (WEXLER et al., 1955):
o—— 25.10. Pet Ohio
w——* 26.10. 1950
Calculated
2 JWN
20.5.56
NS
22-0h
12 7 56
0-4h
40
SSN, NNN, WNN
Relative Rn- concentration (cpm/g)
K-profile
50
~~
40
~~
50
WNW 7
r ground level under inve
rsion
2
{
4
1
6
!
8
i
10
12km
Altitude
ERNELAE:«te,
the NNW case (normal tur
buupper troposphere. The
mean
flights agrees rather well
with
orofile NNN for which the
Rn™
t an altitude of 2 km is
about
ncentration near ground
level,
onsistent with observati
ons of
tk [1928] and Wilkening
[1953].
on indicates that it is poss
ible
ertical profile of the tur
bulent
*nt from measurements
of the
an™ distribution. The avai
lable
thin the troposphere giv
e some
the K profile NNN, giv
en in
represents average turbul
ence
0
0
Fig. 4.
Comparison of observed and calculated relative Rn profiles in the troposphere.
conditions in the troposphere. If we assume
normal conditions of turbulence in the tropo-
sphere, i., the profile NNN in Figure 1, a
rather rapid decrease of the Rn™ concentration
should be expected in the tropopause. In this
case the part of the total activity in a vertical
column of air which reaches the layer above
12 to 13 km (mean altitude of the tropopause
in the temperate zone) is only about 1 to 2 per
cent. If we assume the K profile SSN (strong
tropospheric turbulence), however, this part in-
creases to about 10 to 15 per cent. This suggests
that considerable amounts of Rn™ can penetrate
through the tropopause into the lower stratosphere only during periods of strong vertical
turbulent mixing or convection, e.g. in case of
cumulonimbus formation.
Machta and Lucas [1962] recently reported
the first results of Rn™ measurements in the
tropopause and lower stratosphere which indicate new aspects of the exchange process
through the tropopause (Figure 5). The air