NO. 15 



WEATHER AND SOLAR ACTIVITY CLAYTON 



almost exactly parallel with the sun-spot curve. This similarity indi- 

 cates clearly a relation between the two. 



No such parallel relation prevails between the smoothed annual 

 means of pressure in high latitudes and the sun-spot curve. In com- 

 paring plots of the two. decade by decade, it is evident that in high 

 latitudes the centers of action in the atmosphere varied in position 

 over wide distances with variations of intensity of solar activity. 



Fig. 7. — Comparison of mean pressures in Tropics with sun spots and 

 solar radiation. 



(i) Mean annual pressures at Quixeramobim and Antananarivo, corrected for 

 trend. (2) Mean annual number of sun spots, inverted. (3) Mean annual values 

 of solar radiation, in calories per minute, inverted. 



This shifting of centers of action in high latitudes causes discon- 

 tinuities and changes of phase in the sun-spot period and confuses 

 relations that might otherwise appear. 



The relative sun-spot numbers at successive sun-spot maxima diiter 

 greatly, as will be seen by the numbers in table 2. 



Table 2. — Relative Sun-spot Numbers at Different Epochs 

 Yearly means 



I«70. 

 1883. 

 1893. 

 1905. 

 1917. 



Number 



139.I 



637 



84.9 



63.5 



103.9 



77.8 



Year 



1867. 



1878. 



1889. 



19OI . 



1913. 



1923. 



Number 

 • • 7-2> 

 ■■ 3-4 

 .. 6.3 



1.4 



5.8 



The highest sun-spot numbers were in 1870, 1893, and 191 7, and 

 lesser maxima were observed in 1883, (905, and 1928. The first 



