PRECIPITATION ON MOUNTAIN SLOPES POCKELS 



97 



also the determination of the cloudy region, that is to say, that 

 region in which the atmosphere is saturated and the distribution of 

 temperature therein, since the latter first gives us the value of F. 

 To this end we have to follow the adiabatic change of condition of 

 the air along each curve of flow, starting with the given tempera- 

 ture and humidity, in the vertical above the center of the valley 

 where x = —A/4, where the current is truly horizontal. 



By connecting together those points in the individual stream lines 

 at which saturation is just attained we find, first, the contour of the 

 cloudy region. 



Since the form of the cloud is also of interest in and of itself 9 

 therefore its determination will be carried through as a part of our 

 second example, in that above the center of the valley, where 

 x = — XI 4 first for the summer, then for the winter, we make some 

 assumption as to the mean distribution of temperature in accord- 

 ance with von Bezold's collected data, on page 21 of his memoir 

 above quoted. In accordance with this, we have: 



For y =-1500 -600 +400 +1400 



Valley above sea 

 level 100 m. 



Summer 



Winter 



17.7° 11.0° 

 8.2 6.69 

 0.2° 0.6° 

 2.92 2.17 



5.3° 

 4.59 

 5.1° 

 1.64 



+ 0.9° 



3.03 



-10.8° 



1.19 



+ 2400 meters. 



Height above sea 

 level, 4000 m. 



- 5.0° 



2.60* 



-14.6° 

 0.86 



F = 



t = 



\F- 



In place of the value of F, designated by a star, we will take that 

 value (2.2) that results from the smoothing out of the protuberant 

 corners which the curve for F (see von Bezold, fig. 11,) shows at 

 the altitude of 4000 meters. 



According to equation 5 the lines of flow have for their expression 



m 



e ny sin m x 



b qn 



+ Be qi 



or if r is the value of y when x = o, and y — y = t), there results, 



e -n n e ~ny gin m % = L (* «" - 1), 



b qn 



b n I / i^L - ojl\ 



_ e ~ ny ° e" rn sin m x = ( e 2 — e 

 m q 



9 It seems, for example, quite possible to argue from the observed bound- 

 ary of the clouds inversely to the percentage of moisture in the current of 

 air flowing toward the mountain slope. 



