108 



RADIATION HIOLOGY 



calculated I'loni \\\v integral 



/^' - fr 



i(i\ 



(3-7) 



and the / \'s. X cur\"c.s lor the se\eral xaiues of Z. The resulting values 

 of E are plotted against Z in the 4-mm curve of Fig. 3-8. Families of 

 i vs. X curves similai' to those of Fig. 3-7 were calculated for other ozone 

 thicknesses, and from these curves and Ei\. (3-7) the E vs. / curx'es of 



2900 3000 3100 3200 3300 3400 

 WAVE LENGTH, A 



Fig. 3-7. Observed solar-spectral-energy curve ?n above atmosphere and calculated 

 curves of i after passing through 4 cm of ozone at various zenith angles. 



Fig. 3-8 for 1, 2, and 3 mm of ozone were calculated. The curves illus- 

 trate the manner in which E decreases with increasing ozone thickness 

 and increasing zenith angle. Curves for integrals to wave lengths less 

 than 3200 A were similar to those of Fig. 3-7 but descended more rapidly 

 to low values. 



The effect of the atmosphere, in addition to the ozone, is shown by the 

 dotted curve of Fig. 3-8, which refers to a "fairly clear" atmosphere with 

 1 mm of ozone. It was calculated from Eqs. (3-6) and (3-7) with «„ from 

 curve III, Fig. 3-5. The dotted curve of Fig. 3-8 brings out the almost 

 obvious fact that a relatively small amount of atmospheric haze is more 

 effective in reducing the ultraviolet energy of the direct rays of the sun 

 than, for example, doubling the ozone thickness of the upper atmosphere. 

 However, we must hasten to remark that haze reduces the total ultravio- 



