NO. 5 



FORECASTS OF SOLAR VARIATION ABBOT 



ocean currents, snow, clouds, humidity, wind, which affect locahties 

 differently. Yet I am firmly persuaded that the main part of the 

 departures from normal monthly mean temperatures at many localities 

 are produced by the 7 periodic variations of the sun above referred to. 

 There are, it is true, several additional periodic terms in the weather 

 changes, which seem to be at least indirectly of terrestrial causation. 

 The difficulty in long-range weather forecasting from periodicities lies 

 in the fact that though the periodicities of definite interval obviously 



Table 2. — Solar-coiistaiit zvlucs expressing a long-ranyc forecast of solar 

 7'ariaiio)i 



1933- 

 1934- 



1.940 

 1.938 



continually remain, their amplitudes and forms change, and they shift 

 in phase forward and backward from time to time owing to local ter- 

 restrial influences. In an effort to overcome these obstacles Mrs. Bond 

 and I are discussing the monthly mean values of temperature depar- 

 tures at several inland stations of the United States from 1875 to 

 1925. We hope to determine such controls of the variations of ampli- 

 tude, phase, and form of the periodicities as shall enable us to make 

 forecasts of temperature departures from 1926 to 1933 which may 

 immediately be tested against observation. We shall present these 

 results in a later paper. 



