ABSTRACTS 



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METEOROLOGY, — The total radiation received on a horizontal surface 

 from the sun and sky at Mount Weather, Va. Herbert H. Kimball. 

 'Monthly Weather Review, 42: 474-487. August, 1914. 



At this station a Marvin pyrheliometer was employed to measure 

 the intensity of direct solar radiation at normal incidence, and a Cal- 

 lendar horizontal recording pyrheliometer for measuring the total 

 radiation received on a horizontal surface from the sun and sky. By 

 employing a screen to eclipse the sun at intervals throughout the day, 

 the Callendar pyrheliometer was also utilized to measure the total 

 radiation from the sky alone. The bright receiving grids of this pyrheli- 

 ometer are selectively absorptive of radiation of different wave lengths 

 and it was therefore necessary to standardize the instrument for measure- 

 ments of radiation of different degrees of blueness, varying from the 

 color of sunlight to that of skyhght. This was accomplished by com- 

 paring measurements by Callendar and Marvin pyrheliometers of the 

 intensity of solar radiation transmitted by color screens. 



The summary of measurements made between May, 1912, and 

 September, 1914, inclusive, shows that during this period with the 

 clearest sky the total radiation per square centimeter of horizontal 

 surface varied from 250 calories per day on December 20 to 765 calo- 

 ries on June 10. On March 20 it was 605 calories, and on September 

 20, 515 calories. In general, the radiation received on a clear day 

 during the half-year, December 21 to June 20, averaged about 8 per 

 per cent more than that received during the remaining half year. 



The average daily radiation in summer, hicluding rainy and cloudy 

 as well as clear days, was about 68 per cent of that received on the 

 clearest days, and in winter about 63 per cent. 



At noon, with a clear sky, the total radiation per minute per square 

 centimeter of horizontal surface varied from 0.77 calorie in December 



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