THE 



AMERICAN JOURNAL OF SCIENCE 



[FO URTH SERIES.] 



Art. XXII. — Studies on the General Circulation of the 

 Earttis Atmosphere ; by Frank H. Bigelow. 



A Discussion of the Departures and the Residuals of the 

 Temperature and Precipitation in Climatology. 



Meteorological and climatological observatories, at numer- 

 ous stations in all parts of the world, are turning out an 

 enormous mass of raw material every year, which is of only 

 moderate value unless it can be intelligently and thoroughly 

 discussed. This material consists of daily observations which, 

 when collected together in tables, produce the daily, monthly 

 and annual means, respectively, by the usual processes of 

 summation for the several time-terms. When these time- 

 terms or periods are repeated many times, a normal mean can 

 be computed as a reference value. The variations of each 

 time-term on the normal may be called its departure / the 

 variation of a time-term on its consecutive mean may be called 

 its residual. To illustrate these terms, take the following 

 examples derived from Bulletin S, U. S. Weather Bureau, as 

 given in table 1, 1909. The annual means from 1873 to 1905 

 for five stations are called t l9 t 2 , t 3 , t A , t„ and this notation can 

 be extended for n stations to t n . When the original observa- 

 tions are reduced to a strictly homogeneous series by eliminat- 

 ing the errors of observing and computing, the mean of a long 

 record, as of thirty-three years, is the normal, t . The differ- 

 ences t-t , t-t , . . . t r -t , for the several years, r in number, 

 give the departures, v 1 having r values for the first station, 

 v 2 having r values for the second station, and v n having r 

 values for the nth station. There are rn departures for n 

 stations and r time-terms. Since it is evident that in restricted 

 areas, as the Lake Region of the United States, the variations 



Am. Jour. Sci.— Fourth Series, Vol. XXIX, No. 172.— April, 1910. 

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