OZONE IN THE ATMOSPHERE 
hardly be denied. Méller [64] explains the stratospheric 
temperature differences between tropics and temperate 
latitudes on the basis of the variable protective action 
of the ozone located above the emitting carbon dioxide; 
Dobson [23] arrives at an identical result even more 
directly. For the lower stratosphere he estimates the 
temperature of radiative equilibrium of HO to be 200C, 
that of COs to be 200C, and that of O3; to be 260C, which, 
for equal portions of these three absorbers, would lead 
to the plausible mean value of 220C. In comparison 
with higher latitudes, the lower secondary advection 
layer is absent in the vicinity of the equator, and ozone 
has correspondingly less effect on temperature. But 
even considering only the indirect action due to ad- 
vection of air masses of different temperature, ozone 
has a significant effect on our weather. 
ADDITIONAL REMARKS CONCERNING THE 
SIGNIFICANCE OF ATMOSPHERIC 
OZONE 
Ozone and the Constitution of the Upper Atmosphere. 
The Warm Layer. Absorption of the short-wave radi- 
ation from the sun at the upper boundary of the ozone 
layer results in a temperature of +50 to +80C at an 
altitude of 55 km. This region is known as the warm 
layer [84]. This warm layer was first encountered in 
1922 by Lindemann and Dobson in connection with 
the determination of the altitude at which meteors be- 
come incandescent. The anomalous propagation of 
sound, which results when sound encounters the warm 
layer and is refracted back to the earth [101], leads 
to good temperature data for this high layer; taking 
an average of the values given by Duckert [26], Guten- 
berg [48], and Whipple [26], the temperature in summer 
is —50C at an altitude of 30 km, +28C at 40 km, and 
+70C at 50 km. If a gas, such as ozone at its upper 
boundary, absorbs mainly in the ultraviolet part of the 
spectrum but emits according to the laws of temper- 
ature radiation, then its temperature must rise to a 
rather high value before incident and emitted radiation 
will attaim equilibrium. This is even more applicable, 
incidentally, to the case of oxygen absorption in the 
ionosphere [88]. On the other hand, water vapor with 
its absorption in the infrared tends to lower the equilib- 
rium temperature. Considering the fact that the sun’s 
temperature is lower in the short-wave continuum, 
Gowan [46] finds that his calculations show satisfactory 
agreement between ozonosphere temperature and the 
data on record. According to his calculations [47], the 
warm layer persists even during the night. Barbier and 
Chalonge, EH. Vassy and Déjardin (for references see 
[19]) attempted to calculate the mean temperature of 
the ozone layer on the basis of the temperature de- 
pendence of absorption in the Huggins bands by 
methods of indirect aerology; they also attempted to 
calculate the mean temperature of ozone above 30 km 
on the basis of the temperature distribution up to 30 
km. In order to analyze the warm layer proper, Gétz 
suggests that, instead of measuring the ozone bands 
in sunlight as customary, the Umkehr effect should be 
used in zenith light at low elevation of the sun. In- 
287 
direct. conclusions concerning the vertical temperature 
distribution have recently been verified [66] quite satis- 
factorily by means of V-2 rockets.? 
Pekeris [74] has shown that on the basis of the warm 
layer it is possible to calculate a free oscillation of the 
atmosphere with a period of very nearly 12 hours, such 
as is necessary for the resonance theory of the migratory 
pressure wave of a half day’s duration. As a heat 
source at high altitudes, the warm layer is capable of 
damping the circulation currents in the troposphere 
and is thus of climatic significance [8]. Many years ago, 
Wegener [100] deduced the existence of a high altitude 
troposphere (Hochtroposphdre) above 60 km from the 
existence of noctilucent clouds at an altitude of 82 km; 
we now know that the heat source for this phenomenon 
is the warm layer caused by ozone. 
The Screening Effect of the Ozone Layer. The atmos- 
phere of the earth forms an opaque screen for short- 
wave ultraviolet, so that the shadow cone for this 
radiation is not tangent to the earth’s surface but rather 
to a sphere of enlarged radius. Gotz [37] has therefore 
suggested that the upper boundary of the ozone layer 
be determined from ultraviolet observations during 
lunar eclipses. Barbier, Chalonge, and Vigroux [6] have 
accomplished this up to an altitude of 16 km [71a]. 
According to Gétz this screening effect is of particular 
significance if the altitude of atmospheric dissociation, 
excitation, and ionization processes is to be calculated 
from the time of onset of these processes at dawn or the 
time at which they cease in the evening. When the 
altitude of sodium luminescence was given as 60 km 
on the basis of the dawn effect, it was pointed out [389] 
that the altitude of the ozone layer would have to be 
added to this figure if photoluminescence were assumed. 
And indeed, Vegard and Ténsberg [99], by simultaneous 
measurement of the intensity drop of the sodium line 
at the zenith and at the horizon, found the upper sodium 
boundary to be at 116 km and the altitude of the screen- 
ing layer at 56 km. Penndorf [75], rigorously defining 
the ozone shadow boundary, has carefully calculated 
the conditions in an effort to determine accurately the 
upper boundary of the ozone layer from such observa- 
tions. The ozone shadow boundary seems also to be 
significant in connection with certain delay processes 
observed in the E-layer by Lugeon and Mitra [89]. 
Stormer [90] found that noctilucent clouds always ap- 
pear only when the sunlight striking them is no closer 
to the earth’s surface than 30 to 45 km. It does not 
follow, of course, that it is the ozone shadow which is 
significant in all similar cases. In the case of the photo- 
luminescent effect of the red twilight line at 6300 A, 
it is the shadow of the oxygen sphere which is opaque 
up to an altitude of about 100 km [41]. 
Ozone and Bioclimatology. The biological significance 
of the ozone layer can be touched upon but. briefly 
within the scope of the present article. The ozone layer 
is of the greatest importance in controlling the ultra- 
2. Consult Fig. 8 in ‘‘Temperatures and Pressures in the 
Upper Atmosphere” by H. E. Newell, Jr., pp. 303 to 310 in 
this Compendium. 
