no. 3 



RADIATION OF THE ATMOSPHERE ANGSTROM 



147 



During the day there was a moderate breeze from the north blowing down 

 the valley. This became very light toward evening, and at about the same 

 time the temperature began to fluctuate, sudden changes of 2° to 5 C. 

 occurring frequently between 6 p. m. and the time of minimum temperature. 

 These fluctuations are well shown in the thermograph records at Inde- 

 pendence, Cal. (fig. 15), and in table 15, which contains observed temperatures 

 and humidities at Lone Pine, Cal. These observations have been referred to 

 by Dr. Wm. R. Blair in his discussion of mountain and valley temperatures 

 (Bulletin Mount Weather Observatory, Washington, 1914, 6:122) and are 

 in accord with the conclusion there reached that " there is not a stream of 

 cool air past the slope station, but a direct convective interchange between 



Table 15. — Fluctuations in surface temperature and humidity at Lone Pine, 

 Cal., August 2 and 3, 1913 



the cool air on the slope and the free air over the valley at the same or 

 slightly lower levels." In general, as shown in table 15, the lower tempera- 

 tures were accompanied by the higher absolute humidities. 



Between 8 and 10.30 p. m. it was necessary to bring the balloon down 

 because of southerly or southeasterly winds aloft. These winds gradually 

 extended toward the surface and were warm and dry (table 13). The mixing 

 of the upper southerly and the lower northerly currents seems to account for 

 the variations in surface temperature and humidity already referred to. 



The fact that the upper southerly wind is warm and dry suggests the 

 probability that it originates over the Mohave Desert, which is about 150 kilo- 

 meters south of Lone Pine. The heating and consequent rising of air over 

 the desert in the daytime, which gives rise to the southerly current aloft, at 

 the same time causes the surface northerly current down the valley. 



