CHAPTER VIII - 

 APPLICATIONS TO SOME METEOROLOGICAL PROBLEMS 

 A. NOCTURNAL RADIATION AT VARIOUS ALTITUDES 



The number of investigations contributing to our knowledge of 

 this special question is not large. When we have mentioned the 

 simultaneous observations of Pernter 1 at Rauris and on Sonnblick, 

 and the observations of Lo Surdo 2 at Naples and Vesuvius we have 

 exhausted the previous work on this subject. The observations that 

 have been described above seem now to give a basis for forming a 

 general view upon the question of the influence of altitude upon the 

 effective radiation. In several cases observations have been carried 

 out simultaneously at different altitudes, but before we enter upon a 

 comparison between them, we shall treat the subject in a more general 

 way. As has been emphasized on several occasions, our observations 

 indicate that the atmospheric radiation in the lower layers of the 

 atmosphere is dependent chiefly on two variables : temperature and 

 humidity. Hence it is obvious that if we know the temperature and 

 the integral humidity as functions of the altitude, we can calculate 

 the radiation of the atmosphere at different altitudes, provided that 

 the relation between radiation, temperature, and humidity is also 

 known. It has been the object of my previous investigations to find 

 this relation ; hence, if the temperature and humidity at the earth's 

 surface are known, together with the temperature gradient and the 

 humidity gradient, I can from these data calculate the radiation at 

 different altitudes. The radiation of the atmosphere will evidently 

 always decrease with increasing altitude. But the effective radia- 

 tion, which is dependent also on the temperature of the radiating 

 surface, will behave very differently under different conditions. If 

 no radiating atmosphere existed, the effective radiation would de- 

 crease with a rise in altitude owing to the decreasing temperature. 

 If the temperature of the atmosphere were constant, the effective ra- 

 diation would always increase, when we moved to higher levels, 

 owing to the fact that the atmosphere (which is now assumed to 

 radiate) gets thinner the higher the altitude. 



1 Loc. cit. (Histor. Survey). 

 2 Nuovo Cimento, 1900. 



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