33-° 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 51 



the diminution of humidity in respect to the mixing ratio. Whereas 

 according to Suring's formula, the vapor pressure (e) at an altitude 

 of scarcely 1000 meters is reduced to one-half of that observed at 

 the earth's surface, we must rise to 2000 meters before finding the 

 mixing ratio (x) or the specific humidity (y) diminished to the same 

 extent. But at an altitude of 6000 meters the vapor pressure is only 

 1/20 of that in the lowest stratum, whereas the mixing ratio and the 

 specific humidity are somewhat less than \ of those in the lowest 

 stratum. 



The slight increase of the relative humidity (i?) in the highest 

 stratum, as expressed by the numbers (52 and 60), can hardly have 

 any general importance for we should not overlook the fact that it 

 needs only very slight changes in the course of the temperatures to 

 greatly change the values of the relative humidity and the course 

 of the corresponding curve. 



I omit any further remarks that are suggested by figure 52 and 

 turn rather to another example that shall relate to the behavior of 

 ascending air without experiencing any mixture with other air or 

 any decrease or diminution of heat. 



Let this air at its start have the altitude of o meter, pressure 

 76o mm , temperature 25 C, vapor pressure 9.25 mm . If this air ascend 

 adiabatically, then at the altitude 1800 meters 'condensation will 

 begin and at 3070 meters it will have attained the snow stage. 



In detail we have the series of values given in table 2. 



table $ 



Fig. 53, which needs no further elucidation, shows the peculiar 

 course of these values. 



On the other hand this diagram shows clearly how important it is 

 to take into account the mixing ratio, or if one prefers it the specific 

 humidity, together with the vapor pressure and the relative humid- 

 ity, in the reduction of the humidity data for various altitudes. 



This is especially important if we keep in mind the fact that the 

 change of x for any given change of altitude gives directly the quan- 

 tity of water that is precipitated in the ascent of the air through this 

 vertical distance. 



