NO. 3 



SOLAR VARIATION AND WEATHER ABBOT 



period in the precipitation at Vienna, Austria. Jonathan Wexler 

 computed electronically for us the 39-month period in Vienna pre- 

 cipitation in terms of average percentage departures from the normal 

 for all months between 1910 and 1950. I select the months when 

 Wolf sunspot numbers exceeded 20. In our adopted nomenclature 

 this group as presented from 1910 to 1950 is Category 2, Division 2. 

 This means that the Wolf sunspot number was above 20 and the 

 time interval was the second half of the years spanning 1870 to 1950. 

 When one scans line A, figure 18, it naturally divides into halves. 

 The average half, line B', is computed and subtracted, leaving line B. 

 From this the average third, line C, is removed, leaving line C. From 

 this, successive removals are D', one-fifth, leaving line D ; then E', 

 one-eleventh, leaving line E; and finally F', one-thirteenth, leaving 

 line F. The line F shows a nearly smooth sine curve. The small 

 indentations may all be traced to accidental irregularities of pre- 

 cipitation in the original observations. The amplitude of sine curve F 

 is 17 percent of normal precipitation, which is 17/0.28, or about 60 



ZS 27 29 H 33 31 37 3i 



Fig. 18. — Thirty-nine-month period in Vienna precipitation, cleared of 

 shorter harmonics. 



