NO. 6 



SOLAR RADIATION AND WEATHER CLAYTON 



29 



The monthly means are given in table 9, and include all the months 

 during which observations have been obtained since the beginning of 

 observations on Mount Wilson in 1905. They are made up from 

 observations at Mt. Wilson and at Calama, Chile, in 1918; from 

 Calama alone from October, 1919, to September, 1920; and after 

 October, 1920, from simultaneous observations at Montezuma, Chile, 

 and Mt. Harqua Hala, Arizona. 



In order to study the effects of the changes in the monthly means 

 of solar radiation on the weather of the world, the months of 



Table 9. — -Monthly and Atmual Means of Observed Values of Solar Radiation in 



Calories Per Sq. Cm. Per Minute. Made by The Astrophysical 



Observatory of the Smithsonian Institution. 



January and July were selected as representing opposite seasonal 

 conditions. Departures from the normal pressure, temperature, and 

 precipitation were taken as being the best means of studying the 

 influence of the solar changes. There are only five Januaries avail- 

 able for study. The mean solar radiation of January, 1919, was 

 normal, that of 1920 was i per cent above normal, and that of 1923 

 was I per cent below normal. Data for these months were available 

 for study partly because I had already contrasted January, 1920, 

 with January, 1919.^ 



The data for 1923 were obtained from the Canadian, United States, 

 and Mexican weather services. By adding February, 1920, a winter 



' See " Boletln mensual de la Oficina Meteorologica Nacional," Buenos Aires, 

 1919, published in 1922. 



