JOUllNAL OF THE COLLEGE OF SClENeF, TuKYO IMPERIAL UNIVERSITY. 



VOL. XLT., ART. 1. 



On Diurnal Variation of Barometric Pressure. 



(Contribution II. from the Geophysical Seminary 

 in the Physical Institute, Co!lege of Science}. 



By 

 Torahiko TeRADA, 



Eg ikiihakusJii, 



Masazô KlUTl, , Jyun TUKAMOTO, 



Eigakmh f, Eigakushi. 



1. While the amplitudes and phases of the semidiurnal wave 

 of barometric pressure show a very regular distribution over the 

 entire surface of the earth, those of the diurnal component depend 

 remarkably on secondary local conditions, as was fully illustrated 

 by the classical investigations of A. Angot'^ and J. Hann.^^ 



According to the recent aerological investigations/^ the diurnal 

 component of the daily variation of temperature is conspicuous 

 chiefly in the lowest kilometer of the atmosphere, and it seems 

 quite natural that the corresponding diurnal component of the 

 barometric pressure is influenced by the variety of the nature of 

 the underlying earth's surface within comparatively narrow extent. 

 Imagine for a moment the picture of the isobaric surface at about 

 2 km, over a land with irregular patches of water, desert etc., 

 while the earth's surface is rapidly heated up by the solar radia- 

 tion. The isobaric surface will be scattered over with numerous 

 hills and dales, according to the nature of the substratum, and the 

 resulting horizontal gradient of pressure cannot subsist without 

 the flow of air tending to annul the gradient. When the heating 



1.) A. Angot, Annales du Bureau Central Météorologique de France, 1887. 



2.) J. Hann, Denkschriften d. kais. Akad. d. Wiss., uiath.-naturwis?. Kl., 55, pp. 49-121. 



3.) Eeger, Arbeiten d. kon. preuss. aeronautischen Observatoriums bei Lindenberg, 8, p. 

 229. 



