OZONE IN THE ATMOSPHERE 281 
processes. It is not impossible that, on the one hand, the 
primary layer moves to slightly higher altitudes; on the 
other hand, it is principally of meteorological signifi- 
cance that a lower secondary layer [89] appears which 
swells with increasing ozone amount, so that the original 
separation of the two layers becomes more and more 
indefinite. Representation by the direct stepwise distri- 
bution according to the Umkehr method may be most 
instructive in this connection [89]. Figure 9 shows 
smoothed curves for several examples, including the 
result of the first vertical ozone determination with 
V-2 rockets in which the lower secondary layer was 
also found.! Table I summarizes in customary manner 
Tasie [. AutitupE or THE Mass CEenTER OF OzONE (in km) 
Ozone amount (cm Q3) 
Station Lat. |Method | Ref. 
0.160 | 0.220 | 0.280 | 0.340 | 0.400 
IRoona........ 18°] B [54]) 28.1 
Dalit eee 29°| B (54]) 26.2 | 25.1 
White Sands...| 35° | V-2 | [66] 22.5 
PATOSAS osc. os AT? || AL [45] 23.4) 21.5} 21.3 
PATOSAle. 22. oa... 47° | B [45] 22.6 | 21.4 
Troms6........ 70° | B [62] 21 21 
BRFOMISON 4: =. .\- 70°| A (94]| 26.7 | 25.7] 24.7 | 23.0} 20.8 
the mass center of ozone; there A denotes the analyti- 
cal, B the synthetic evaluation of the Umkehr curve. 
The variation of the center of mass of ozone with lati- 
tude evidently requires additional measurements. 
The lowest portion of the vertical ozone distribution 
may be determined by direct measurement of the ozone 
content near ground level. Whereas in the lowlands 
the ozone near ground level is subject to considerable 
S 
2° y 
S I 
E5 ! 
x= i 
© 1 
x4 \ 
3 I 
| 
1 
) 
10° 2 CM O3 PER KM 
10-8 OZONE /AIR 
Fie. 10.—Tropospheric ozone distribution. 
fluctuation [2], it shows considerable constancy at 
Arosa which is situated at an altitude of 2 km; thus 
1. The reality of this lower-altitude maximum has been 
questioned in a recent paper: ‘‘Upper Air Research by Rock- 
ets,” by H. E. Newell, Jr., in Trans. Amer. geophys. Un., 31: 
25-34 (1950). (See p. 31) 
there appears to be a weak tertiary ozone layer at this 
altitude. As shown by aircraft measurements by Ehmert 
[28] the altitude of this tertiary tropospheric layer may 
vary in individual cases, depending on meteorological 
conditions (Fig. 10). 
THE THEORY OF ATMOSPHERIC OZONE 
The Ozone in Undisturbed Photochemical Equilib- 
rium. The existence of a layer of a heavy gas in the 
upper atmosphere necessitates the assumption of con- 
tinuous regeneration and destruction with consequent 
equilibrium. As early as 1906, E. Regener demonstrated 
by means of laboratory experiments the photochemical 
equilibrium of ozone under the influence of the short- 
wave ultraviolet radiation which, when absorbed by 
oxygen, generates ozone, and also under the influence 
of a radiation that is then again absorbed by the ozone. 
This clearly provides a basis for a photochemical equi- 
librium in the atmosphere under the action of solar 
radiation. No other theory provides an equally adequate 
explanation even though it cannot be denied that oc- 
casionally electrical storms and cosmic radiation might 
contribute some ozone. At the altitude of the equi- 
librium layer, radiation in the wave length region be- 
tween the Schumann-Runge and Herzberg bands pro- 
duces ozone, whereas the wave length of the Hartley 
band particularly, but also those of the Chappuis band, 
destroy ozone. The various wave lengths involved are 
absorbed very differently and therefore penetrate the 
atmosphere to different depths. 
We are indebted to S. Chapman for the first theory 
of atmospheric ozone based on these considerations. 
Wulf and Deming, to whom more extensive data were 
available [103], worked on the basis of Chapman’s 
fundamental reactions. There are two primary photo- 
chemical reactions, namely, 
Or + hv(d < 2420) > 0 + O, (10) 
involving the number Q» of oxygen-dissociating quanta 
hy, and 
(11) 
involving the corresponding number @3 of ozone-des- 
troying quanta. The quantities Q. and Q; are the num- 
bers of quanta absorbed by oxygen and ozone, respec- 
tively, in a given unit volume of air. For example, Q2 
is given by 
One yas 0) One ao 
Q = [oetst0s dx, 
where a», is the absorption coefficient of oxygen, J is 
the number of quanta incident on the volume, and the 
brackets about O» indicate (here and in subsequent dis- 
cussion) the concentration of oxygen. In addition to 
(10) and (11) there are the secondary reactions. 
0.+0+ M—0;,+ M, (12) 
which requires a triple collision with an arbitrary colli- 
sion partner J for conserving energy and momentum, 
and for which kts represents the coefficient of the reaction 
rate, and finally, 
One O20: (13) 
