OZONE IN THE ATMOSPHERE* 
By F. W. PAUL GOTZ 
Lichtklimatisches Observatorium Arosa and University of Ziirich 
INTRODUCTION 
As early as 1845 the chemist Schénbein, discoverer 
of ozone, attempted to prove that traces of this gas 
are a constant constituent of the atmosphere. However 
the ozone problem in its entire scope was revealed only 
when Fabry and Buisson [82] recognized by spectro- 
graphic methods that the principal quantities of ozone 
are present in the upper strata of the atmosphere. Al- 
though the ozone amount, that is, the total quantity 
of ozone present when reduced to standard conditions, 
amounts to but a few millimeters of the 8-km height 
to which the homogeneous ocean of air rises, this small 
trace is nevertheless sufficient (because of the enormous 
absorption in the ultraviolet) for intercepting the entire 
extraterrestrial radiation below 2900 A, for heating the 
‘Warm layer” at a height of 50 km, and for protecting 
the biosphere against an excess of short-wave radiation. 
Only during recent years has it been possible to pass 
through the high ozone layer with the aid of V-2 rockets, 
a feat which opened an entirely new spectral range of 
solar radiation to astrophysical investigations. But how 
is it possible for such a relatively heavy component of 
air to maintain itself high in the atmosphere? Only if 
it 1s constantly being regenerated, if short-wave radi- 
ation from the sun is capable of transforming oxygen 
to ozone. The opposing effect of long-wave ultraviolet 
which is again absorbed by ozone thereby destroying 
it (H. Regener), produces a spontaneous chemical ozone 
equilibrium in the upper layers of the atmosphere; be- 
low 35 km, however, this latter process is so slow that 
ozone which, by some meteorological processes, has 
been transported to these altitudes is largely ‘“‘pro- 
tected.”’ In lower layers ozone becomes an important 
conservative property of the air until the stream from 
the high altitude ozone source is finally destroyed near 
ground level due to photochemical, chemical, and cata- 
lytic decomposition. In view of its intimate connection 
with weather processes (Dobson), the study of ozone 
provides methods of indirect aerology; there is an ever- 
imcreasing tendency to supplement a mere observation 
of total ozone amount with a detailed measurement of 
its vertical distribution and changes thereof. Only by 
investigation of this latter type will it be possible to 
understand the effect of ozone on the flux of radiation. 
An intriguing aspect of the ozone problem is that 
the most diverse scientific fields converge at it. Two 
international conferences [16, 31] and several national 
conferences [71] have so far been devoted to this prob- 
lem. The Meteorological Association of the Inter- 
national Union for Geodesy and Geophysics has a 
special commission on ozone. 
* Translated from the original German. 
METHODS OF OBSERVATION 
Absorption Coefficients. Ozone has its principal ab- 
sorption in the Hartley band [68] extending from 3200 
to 2000 A. At X = 2553 A the decadic absorption co- 
efficient is 145, that is, a layer as thin as 1445 cm re- 
duces the intensity of radiation to one tenth. On the 
short-wave side, in the region of the ozone-oxygen gap 
which is so important for the theory, Mme. A. Vassy 
[96] satisfactorily verified the older measurements of 
Edgar Meyer. The long-wave side of the Hartley band 
connects with the Huggins bands which extend up to 
3690 A, and these bands are temperature dependent. 
However, new determinations [4] yielded the opposite 
finding that the absorption maxima too are influenced 
by temperature. The Chappuis bands, although rela- 
tively weak, coincide with the region of maximal solar 
energy; because of the superposition of the vapor bands 
in the solar spectrum, they are not suitable for ozone de- 
termination, according to Mme. Vassy. Absorption in 
the long-wave region is important for the problem of 
heat balance; the absorption band between 9.0 and 
9.7 uw seems particularly significant because it hes in the 
otherwise very transparent atmospheric window be- 
tween 9 and 13.5 uw. According to Strong [92], and Adel 
and Lampland [1], absorption in the 9.6-» band exceeds 
all previous assumptions by a factor of about ten and 
is very dependent on pressure, approximately propor- 
tional to the fourth root of pressure, a fact which 
Strong uses for determining the average height of the 
ozone layer by simultaneous determination of the ozone 
absorption in the ultraviolet and the infrared. 
Oxygen has absorption properties which form the basis 
for the theory of the ozone layer. In this connection, the 
region of maximal absorption between 1300 and 1750 
A [56] is of less interest than the wave lengths around 
2000 A [96] which overlap the ozone absorption. De- 
viations from Beer’s law are significant. I am indebted 
to W. Heilpern and E. Meyer [51] for imformation 
regarding the current state of this question. If the 
absorption of light is given by J = Jo X 10-“’, where 
e denotes the extinction coefficient for a pressure P in 
kilograms per square centimeter, and if the thickness 
of the layer / = 1 cm, then e for pure oxygen is given by 
€(Oo) = «,P + @P?. (1) 
For an arbitrary mixture of O. and N»2, where c; denotes 
the volume concentration of Os and c that of Ne, € is 
given by 
e(@) = ePo “ eP2c? + €P°C1Co 5 (2) 
where P denotes the total pressure. The third term 
represents the effect of the “extraneous gas.” In the 
region investigated, the constants «, @, and e have 
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