NO. 5 



SOLAR VARIATION AND FORECASTIN( 



-ABBOT 



25 



The question arises whether increase of the solar constant implies 

 increase of intensity in equal proportion over the whole spectrum. 

 To test this, we have used a number of the best determinations made 

 by the fundamental method of Langley. We separated these into 

 groups of high, medium, and low solar constants, and took mean 

 values of the spectrum distribution outside the atmosphere. We 

 divided the numbers representing the distribution curve for low 

 solar constants into the corresponding numbers representing higher 

 ones, first having reduced the curves to such a scale of ordinates as 



lATioNS or the: 

 H|ala. Solar cha 



SHORT- 1 



Sun 



NGLS, c?.3and 

 NTER\AL CHANGES, 1.4 



IX; o^ 

 50/0 



^^^ ^^ ^:/- . ,r^ , u^ - 



C\bO f\70 a^ 



00'" 



'■po 



ZOO' 150' 100' 50' 0' 



Fig. 18. — Solar variation localized in the violet and ultra-violet. 



to represent the change in solar constant by the change of area 

 included under them. Figure i8 shows the result. Curves A and B 

 are for Harqua Hala values of high and medium solar constant as 

 compared to low. These represent what happened in the big swing 

 in solar-radiation level from 1921 to 1923. The 1921 values were 

 high because the blue, violet, and ultra-violet were high. The green, 

 yellow, red and infra-red were almost unchanged. 



Curve C is from recent Montezuma values of 1924. It represents, 

 therefore, nothing but short-period solar fluctuations. No care was 

 used in computing Curve C to reduce the areas under the curves to 

 proportionality with the solar constant. However, it will be seen 



