OZONE IN THE ATMOSPHERE 
During the summer season there are no great meridional 
differences in the interdiurnal variability. In July and 
August, in India it is 0.005 em, at Troms6 0.010 cm, 
at Spitsbergen 0.007 cm; in December it rises to 0.056 
em at Troms6. The fluctuations frequently become 
manifest even during a single measuring day, in the 
form of an ‘ozone cloud” [55]. In one case in which 
ozone was determined by sighting on stars in various 
directions of the sky, it was possible to delineate such 
279 
of ozone amount is revealed by an increase from 0.17 cm 
at the equator to an “ozone belt”? (Gotz) of 0.26 em 
at latitude 60°N; the ozone amount again decreases 
toward higher latitudes. In the Southern Hemisphere, 
the gradient is more pronounced, and here again it is 
the maxima rather than the minima that are significant. 
The variation is best described by an isoplethic repre- 
sentation (Fig. 7), in which the ozone belt is shown by 
means of a dot-dash line. 
FEB 
MAR APR MAY JUN 
JUL 
AUG SEP OCT NOV 
Fie. 6.—Annual variation of the ozone amount at Arosa and Tromsé. 
an ozone cloud in space [3] as a forerunner of a con- 
siderable increase in ozone. A regular, slight daily vari- 
ation of ozone has so far been reported only from Delhi 
[53]; at Arosa, a change in the temperature correction 
of the Dobson spectrophotometer simulated a diurnal 
variation for some time. Differences between day and 
night have not yet been confirmed. Frequently ozone 
fluctuations are of periodic nature [43] with periods up 
to 36 days, as has been found for the barometric pressure 
at the ground. 
Concerning the annual variation of ozone amount, 
we are quite well informed by the extensive observa- 
tional network of Dobson [21]. The representation as 
a yearly sine curve, with an amplitude which increases 
with latitude from a value of zero at the equator, is a 
considerable simplification even at middle latitudes. 
Figure 6 represents the overlapping five-day averages 
of the extensive measurements at Arosa (1926-1946) 
and Tromsé (1939-1948). At Troms6 an almost sud- 
den linear increase in January and February is followed 
by a gradual decrease terminating in an “ozone gap” 
at the end of December. It seems doubtful that all 
the peaks in the Arosa curve, such as those found at 
the end of April or the end of October, will be smoothed 
out by averaging more extensive observational ma- 
terial [43]. 
The latitudinal dependence of the annual averages 
As regards the secular variation, that is, ozone vari- 
ation from year to year, Fowle’s hypothesis concerning 
the correlation with the relative sunspot number was 
UNIT: 107° CM 03 
S38 eel & ; 
(2 & oo SS uN a] wv a oo. 
yl Oe ei aig pope Ta oo 
>) ° x 
= +60 = = 
2 noe 260 220 
| 240 300 
220 
a ° I, 
a +20 200 180 
Ss) 180 i 
a op 160 
a 160 Ie 
(to es ° l 
ar nee IS 200 
< 200 220 
© -—40° 220 = 240. 
i ee | 28 Onl kSOO 260 
-60° 240 =i n | 
ark Saar eat 
JAN FEB MAR APR MAY JUN: JUL’ AUG SEP OCT NOV DEC 
Fic. 7.—Isopleths of the average ozone amount. The ozone 
belt is indicated by dot-dash lines. 
untenable. Figure 8 shows the secular variation for the 
twenty-year series at Arosa, which reveals waves of 
several years’ length. For our further conclusions we 
might wish to have such figures back to ice ages! The 
mean monthly fluctuation about the over-all monthly 
