PRECIPITATION ON MOUNTAIN SLOPES POCKELS 



87 



These equations show that when x — o, that is to say above the 

 center of the slope of the mountain, u is a constant = a at all alti- 

 tudes; above the valley where x is* less than o, u is smaller than a; 

 and above the mountain, or plateau, where x is greater than o, 

 u is larger than, a; the constant a can also be considered the mean 

 horizontal velocity at any given altitude. 



For different altitudes H above the center of the valley we have 

 the following values: 



Therefore, up to the altitude of 5000 meters, the horizontal 

 velocity is sensibly constant and the vertical velocity o ; and, accord- 

 ing to what is said in reference to equation (5') our solution holds 

 good for the case when the profile is continued as a horizontal 

 straight line indefinitely toward the negative side from the point 

 x = — A/ 4, and above this there flows a truly horizontal current of 

 air whose velocity is sensibly constant, namely, 0.93 a up to an alti- 

 tude of 5000 meters and increases in the strata above that until 

 it attains the value a. 



Above the mountain, as at the point where x = + i/4, the velo- 

 cities, u, are greater than a by nearly as much as they are smaller 

 above the valley. 



The distribution of the vertical velocity component which deter- 

 mines the condensation of aqueous vapor is a more complicated 

 matter. In order to represent it, let the values of v/a for different 

 values of the coordinates x and y be as given in the following table: 



Therefore, whereas there is a steady decrease of v with altitude 

 above the center of the slope of the mountain, on the other hand 

 these vertical velocities increase with the altitude in the neighbor- 

 hood of the foot of the mountain as well as on the plateau at the 



