XV 



ON THE REDUCTION OF THE HUMIDITY DATA 

 OBTAINED IN BALLOON ASCENSIONS 



BY PROF. DR. W. VON BEZOLD 



[Zeitschrift far Luftschiffahrt und Physik der Atmosphdre. Vol. 13, pp. 1-9, 

 1884.. Translated from Gesammelte Abhandlimgen, W. von Bezold, igo6, 

 pp. 264.-273] 



Ordinarily we use the vapor pressure, the absolute humidity and 

 the relative humidity as the measure of the moisture in the atmos- 

 phere. 



The determination of these three quantities, or any two of them, 

 suffices in general to define the condition as to moisture. This 

 is especially true when one has a definite portion of the atmosphere 

 under consideration no matter whether one wishes to present its 

 condition as to moisture at a given moment, or to present the 

 chronological changes of condition, especially as in climatological 

 investigations. 



It is different when the problem is to follow a mass of air in its 

 path through the atmosphere and to take into consideration the 

 increase or decrease of the amount of water. 



In order to handle these latter problems a knowledge of the 

 above-mentioned quantities does not suffice, at least not directly, 

 rather must we from these deduce still other quantities if we would 

 attain a correct idea. 



If, for instance, we consider a quantity of air with given constant 

 mixing ratio of aqueous vapor and dry air, and we wish to investi- 

 gate the changes that this undergoes as it rises higher in the atmos- 

 phere, then in spite of the constant mixing ratio both the vapor 

 pressure and also the absolute humidity will in general vary. 



The very important circumstance that during these processes 

 the composition of the air has not experienced any changes cannot 

 be deduced from the data ordinarily employed. 



Inversely, the relative humidity can remain constant, whereas 

 in fact water is steadily being precipitated, as, for instance, in 

 case an ascending current of air has exceeded the limit of saturation. 



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