Mountain Sites for Meteorological Observatories. g 



tories, giving as they must results obtained after the 

 passage of the radiant energy through a considerable 

 stratum of atmosphere, can only be completely verified by 

 comparison with the results obtained at levels approxi- 

 mately above the sensible atmosphere. 



Again, in connection with the radio-activity of air, it 

 is beheved that conditions are very favorable for experi- 

 ments on the ionization of the upper air strata and the 

 part played by electrons as nuclei for condensation. 



But chiefly in connection with the practical question 

 of improving the forecasts over the western half of the 

 country is it important that observatories should be estab- 

 lished on these peaks. The Pacific Coast is essentially a 

 region of marked climatic contrasts. Within short dis- 

 tances great dififerences are found. In other words, local 

 climates are prevalent to a marked degree in this Western 

 country, and there is little of the general uniformity of 

 temperature and other conditions prevailing east of the 

 one hundredth meridian. It is believed that dynamic 

 compression of the air forced down mountain-sides and 

 into long narrow valleys plays an important role in 

 determining local climates. 



Foehn " or Chinook "^conditions must be studied 

 from the vantage-ground of high-level stations. Perhaps 

 the most destructive single condition in California (not 

 excepting a severe frost, or an exceptionally severe storm) 

 is the norther of the Great Valley, or the kindred wind 

 known as the Santa Ana of the region south of the 

 Sierra Madre. Handicapped as the forecaster is on 

 the Pacific Coast by a paucity of reports from the west, 

 it is all the more necessary to obtain reports in other 

 wa}^. Mountain winds play no inconsiderable part in 

 the meteorology of the coast. We have the action of the 

 wind in its general easterly drift, the air circulation due 

 to the procession of passing disturbances, and, more 

 pronounced still, the localized wind-currents or forced 

 draughts up and down the mountain-flanks and through 

 the numerous valleys. It is well known that many sta- 



