Table 144 



TRANSMISSION OF RADIATION THROUGH PURE, DRY AIR 



431 



Fowle 1 has shown that on high mountains above the dust of the lower levels, atmos- 

 pheric transmission by dry air a a \ agrees closely with the theoretical equation developed 

 by King 3 from Rayleigh's 3 classical equations for molecular scattering. 



King's equations are 



a A -e-^ (1) 



and 



where 



h =rb' (M - ir w +bH ]h +D - 



(2) 



Mx = index of refraction of air for wave length X, 

 H = height of the homogeneous atmosphere, cm., 

 p = standard sea-level pressure, 



p = observed pressure, 



X = wave length of the radiation, cm., 

 N = number of molecules per cm. 3 in the homogeneous atmosphere, 



b — energy absorbed by the permanent gases, 

 D = depletion by dust. 



Here a a \ represents the transmission factor for optical air mass unity when p = po. 



Linke 4 has computed k\ and ct a \ for dust-free air (D = 0) assuming N = 2.70 X 10 19 , 

 H = 799100 cm., p = p , and using values of n, given by Traub. 5 The absorption by 

 permanent gases was considered to be negligible (6 = 0). 



Table 144 gives values of k\ and a a \ for various wave lengths. 



1 Fowle, F. E., Astrophys. Journ., vol. 38, p. 392, 1913. 



2 King, L. V., Philos. Trans. Roy. Soc. London, A, vol. 212, p. 375, 1913. 

 3 Rayleigh, Lord, Philos. Mag., vol. 47, p. 375, 1899. 



4 Linke, F., Meteorologisches Taschenbuch, vol. 4, Leipzig, 1939. 

 Traub, W., Ann. Phys., vol. 61, 1920. 



TRANSMISSION OF RADIATION THROUGH PURE, DRY AIR 



SMITHSONIAN METEOROLOGICAL TABLES 



