402 KIMBALL : HAZE OF JUNE, 1912 



METEOROLOGY.— The dense haze of June 10-11, 1912. H. H. 

 Kimball. To appear in full in the Bulletin of the Mount 

 Weather Observatory. 



General meteorological conditions. From June 8 to 12, 1912, 

 the atmospheric conditions at Mount Weather were dominated 

 by an area of high pressure that slowly advanced during the five 

 days from the upper Mississippi valley to the South Atlantic 

 Coast, and was nearly central over Mount Weather on the 10th 

 and 11th. 



Temperature and humidity conditions. Kite observations show 

 that a decided fall in temperature occurred on the 7th and 8th, 

 which extended to a height of at least 3 kilometers above sea level ; 

 and that the low temperature of the 8th was accompanied by a 

 low water vapor content of the atmosphere. On the 9th the 

 temperature of the air up to a height of at least 3 kilometers was 

 rising. There was not sufficient surface wind for kite flights on 

 the 10th and 11th, but the flight on the 12th showed considerably 

 higher temperatures than on the 9th to a height of at least 4 kilo- 

 meters, and also a considerable increase in the absolute humidity 

 of the atmosphere. 



Haze and clouds. On the 8th and 9th the atmosphere was un- 

 usually clear for June, but cumulus clouds formed before oon non 

 both days. There were practically no clouds from the morning 

 of the 10th to noon of the 11th, and the lower atmosphere was 

 still clear, so that mountains 30 miles distant were distinctly visi- 

 ble; but the upper atmosphere was filled with a dense white haze. 

 A cirrus cloud sheet covered the sky during the afternoon of the 

 11th. On the morning of the 12th the haze in the upper atmos- 

 phere had become light, but in the lower atmosphere it was dense, 

 so that mountains 16 miles distant were completely obscured. 

 Clouds covered the sky before noon. 



Pyrheliometer observations. From pyrheliometric measurements 

 of the intensity of solar radiation it appears that the atmospheric 

 transmission coefficient, a, decreased in value from 0.756 shortly 

 before noon of the 9th *to 0.586 at the same hour on the 10th. 

 Its value increased to 0.751 at 5.10 p.m. on the 10th, but was 



