44 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



VII. THE USE OF WEATHER CYCLES IN FORECASTING 



Having" developed methods of separating and studying various 

 conditions which make up the weather, it seemed important that a 

 test be made of the possibihty of using them in practical forecasting. 

 Forecasting future weather conditions in the present state of knowl- 

 edge may be undertaken in at least three different ways : ( i ) By 

 tracing out the results which follow the increase or decrease in the 

 general circulation of the air with changes in solar activity. (2) 

 By analyzing and following weather waves of different classes. (3) 

 By computing the amplitudes and phases of different cycles found 

 in solar and weather changes and projecting these forward into the 

 future. 



In regard to the use of the first method, since increased solar 

 activity is attended by a fall of pressure in equatorial regions and 

 by increased contrasts of pressure in higher latitudes, there is brought 

 about an increased atmospheric circulation and certain general con- 

 ditions follow : 



( 1 ) The cloudy and clear belts of the world are intensified and 

 thus alter the incoming and outgoing radiation. 



(2) The increased air circulation means an increased flow of ocean 

 waters which brings an increased northward flow of warm water 

 along the east coast of the United States and Japan and an accumula- 

 tion of warmer water in the North Atlantic and North Pacific. The 

 accumulation of warmer waters in these regions especially in autumn 

 brings increased cloudiness and increased rainfall. The increased 

 cloudiness reacts by diminishing radiation losses from the earth and 

 thus further modifying weather conditions. On the other hand 

 the increased oceanic circulation brings increased cold water to the 

 shores of North Africa and southern California, and produces a 

 chain of atmospheric conditions which affect the northern shores of 

 South America and the West Indies and extend well out into the 

 Pacific. A parallel set of changes is produced in the Southern Hemis- 

 phere in an opposite way on the east and west sides of the con- 

 tinents. When solar activity diminishes the reverse conditions 

 prevail. 



(3) Increased solar activity brings also an increased flow of air 

 over the continents and with it an increased rainfall in certain regions 

 and a decreased rainfall in other regions. The distribution of pres- 

 sure and attendant conditions is to a large degree influenced by the 

 seasons. 



