NO. 4 PERIODIC SOLAR VARIATION ABBOT 1 9 



tion, the solar-constant values beginning with December 1900 will 

 be the same as those beginning September 1923. In my recent paper 

 on precipitation at St. Louis, Mo. (Smithsonian Misc. Coll., vol. 128, 

 No. 3, 1955), I showed that synthesis by 22 periods, identical with 

 22 periods in solar variation, represented the precipitation at St. 

 Louis well for 70 out of 100 years. The other 30 years appeared to 

 be disturbed by great volcanic eruptions and great wars. 



But it does not follow that, apart from these cataclysms, the 

 weather, though controlled by solar variation, should repeat in 273- 

 month cycles. For the quality of the atmosphere changes (a) with 

 the time of the year; (b) with the prevalence of sunspots; (c) with 

 the change of population, of forestation, and other variable features 

 of the locality. Changes in the quality of the atmosphere alter the 

 phases of weather responses to solar periods. Hence it is that, even 

 apart from cataclysmic events, the weather only roughly repeats itself 

 at intervals of 273 months. For 273 months is not commensurable 

 with 12 months, and sunspot frequency is not sharply periodic at 

 ii| years. Hence two variable agents, (a) and (b) above, somewhat 

 confuse the tendency toward regular weather cycles of 22f years. 

 The element (c) above, is quite unpredictable in its effect on the 

 weather. 



SUMMARY 



Reference is made to 30 years of daily measurements of the solar 

 constant of radiation, at a plurality of stations on arid mountains, 

 6,000 to 10,000 feet in altitude, and in both hemispheres. Comparison 

 of many pairs of northern and southern daily results give a probable 

 error of ^ percent. Tabulations containing 30 to 100 repetitions of 

 lo-day mean results are therefore subject to mean probable error of 

 less than 1/60 percent. 



A family of regular periods in solar variation is disclosed, contain- 

 ing 64 members, all, to within i percent, exact submultiples of 273 

 months. Many members of this family are also found in temperature 

 and precipitation at several cities in the United States. In solar varia- 

 tion, ranges from 0.05 to 0.21 percent are found in over 20 of these 

 periods which figure in weather. In the precipitation at St. Louis, 

 Mo., these identical 20 and more periods have ranges from 5 to 25 

 percent. 



Dr. F. P. Marshall found a period of 212 days, and also more than 

 a dozen submultiples of it, in basal pulse rates. Seven months, a solar 

 and weather period, is nearly the same, 213.07 days. A period pub- 

 lished by the author in 1949, found in the weather of Washington and 



