NO. 3 



SIXTY-YEAR WEATHER FORECASTS — ABBOT 



19 



22f years, as represented in Peoria precipitation. I select this because, 

 as I have said above, the periodicities run from 5 to 25 percent of 

 normal precipitation. As we shall see, the amplitude of this period, 

 for sunspots > 20 Wolf numbers, is 22 percent ; and for sunspots < 

 20 Wolf numbers, it is 25 percent, at Peoria. The curves are shown 

 in figure 11. At the left I plot results d, 02, for Wolf numbers > 20, 



Fig. 10. — The 3oi-month periodicity in Peoria precipitation as modified by 

 shorter periodicities, aliquot parts of 30;^ months. Left, Wolf numbers over 20; 

 right. Wolf numbers below 20. 



in full and dotted curves respectively. Treating a^ first, curve A is 

 what is found when the period of ^i^^=22| months is removed. A 



feeble period of ■ "'" ■ months is then removed, yielding curve B. 



Though not altogether smooth, no other period seems clearly included 

 in curve B. As only five repetitions of the 45^-month period were 



