JOURNAL 



OF THE ^"^^ * 



WASHINGTON ACADEMY OF SCIENCES 



Vol. Ill AUGUST 19, 1913 No. 14 



METEOROLOGY. — Evaporation in the great plains and inter- 

 rnountain districts as influenced by the haze of 1912. Lyman 

 J. Briggs and J. O. Belz, Bureau of Plant Industry. 



It has recently been shown by Abbot and Fowle^ and by Kim- 

 ball, ^ that the haze of 1912, presumably due to the eruption of 

 Mt. Katmai on June 6 and 7, 1912, gave rise to a marked dimin- 

 ution in the intensity of the solar radiation at the earth's surface. 

 Abbot and Fowle found that the total direct radiation of the 

 sun was reduced about 20 per cent at Bassour, Algeria, and also 

 at Mt. Wilson, California, when the effect reached its maximum 

 in August. Kimball reports an average reduction of 17 per cent 

 in the intensity of the solar radiation received at Mt. Weather, 

 Va., during the last half of 1912, while at Madison, Wis., an av- 

 erage reduction of 14 per cent was observed for the same period. 



During the past five years the writers have been engaged in a 

 series of evaporation measurements^ in the great plains and in- 

 tennountain districts, and it has seemed desirable to determine 

 to what extent the reduction in the solar intensity during 1912 

 affected the evaporation. In making such a comparison, it 

 must of course be recognized that evaporation is profoundly in- 



1 Smithsonian Miscellaneous Collections, 60: 29. 1913. 



2 This Journal, 3: 269. 1913. Also, Bull. Mt. Weather Observatory, 5: 295. 

 1913. / 



' In cooperation with the Office of Dry Land Agriculture, and the Office of 

 Western Irrigation Agriculture, of the Bureau of Plant Industry. 



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