ion 



RADIATION BIOLOGY 



phore of puii' air calculated from the Rayleigh scattering theory with 

 polarization dofoct. and curve III is a per atmosphere observed by Vassy 

 (1941) for what may be termed a "fairly clear atmosphere at sea level." 

 The observed (Buisson el al., 1930, 1932) absorption coefficient a of the 

 molecular oxygen gas contained in 1 atm, from which the Rayleigh term 

 has been subtracted, is plotted in cur\e IV, Fig. 3-5. There are no avail- 

 able data on the attenuation of ultraviolet radiation passing down through 

 a hazy or cloudy atmosphere. 



ATMOSPHERIC OZONE 



Ozone exists in the upper atmosphere of the earth for the most part 

 in the region between 15 and 35 km above sea level; it extends in rapidly 



T3 



Uj" 

 O 



3 



o 



I 



0. 



< 



O 



UJ 



o 



Fig 

 NTP 



JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC 



3-6. Average contours of equal thickness of ozone. Unit, I0~' cm of ozone at 

 (Gotz, 1944.) 



decreasing concentration as high as 50 km and down to sea Jexel whcMv 

 there are often traces amounting to as much as 0.05 mm of ozone at NTP 

 per kilometer of air (or 5 X 10^'' by volume of air). The total thickness 

 of ozone in a vertical column of air from sea level to space varies from 

 about 1.5 to 5 mm at NTP depending on the latitude and the season. 

 This is brought out in P'ig. 3-6 which gi\-es an axcrage world-wide distribu- 

 tion of ozone derived by Gotz (1944) from a summary of nearly all avail- 

 able observations. Figure 3-(i shows the increase of ozone thickness with 

 increasing latitude up to about (50° foi- all seasons of the year and the 

 spring maximum and autumn minimunv for latitudes greater than 20°. 

 Whether there is a diurnal variation in the ozone thickness above any 

 station is not known with certainty; a few data mentioned by Dobson 



