88 



ANNTJAL KEPOET SMITHSONIAN INSTfrUTION, 1940 



times in the same phase. It was, therefore, possible to obtain from the 

 meteorological records more accurate determinations of the solar 

 periodicities than could be obtained from our solar-constant work of 

 the past 20 years. The three stations mentioned agreed perfectly as 

 to these determinations. In this way we have established the follow- 

 ing corrected values for solar periodicities expressed in months : 



8.12; 9.79; 11.29; 21.0; 25.3; 39.5; 451/4. 



It now became of importance to see whether the average results in 

 departures from normal temperatures and precipitation, correspond- 

 ing to these corrected periods, could be used synthetically as a means of 

 long-range prediction for the future. In order to investigate this 

 interesting possibility, it was clear that if the courses of the meteor- 

 ological periodicities used should be determined from records all ante- 



PeRCeATTAGS OF NORMAL PREOPtTAT/ON AT P£OR/A, /ll/NO/S. 

 PIV£- MONTH RC/NMNG MEAN l/AiOfS. 



FiaUBK 1. 



dating 1935, for instance, then it would be honest to regard a synthetic 

 assembly of them, covering the years 1935 to 1940, as a true 5-year 

 prediction, which could be fairly compared with the event. This 

 procedure was undertaken for numerous stations, and for both tem- 

 perature and precipitation. The resulting forecasts were not all 

 equally successful. But in all cases there was a marked correlation 

 between the forecast and the event. The agreement turned out to be 

 quite as likely to be good in 1940 as in 1935. As an illustration of very 

 good correspondence, though in this instance failing somewhat in 1939, 

 the 5-year forecast and event for the precipitation at Peoria, 111., is 

 given here. In this case a correlation coefficient of 70^5 percent is 

 found between prediction and event for 58 months. It is hoped that 

 further study may improve the 5-year synthetic forecasts generally. 

 At present they average satisfactory in two-thirds of the months. 



