322 CARNEGIE INSTITUTION OF WASHINGTON. 



METEOROLOGY. 



Bjerknes, V., Bergen, Nonvay. Preparation of a work on the application 

 of the methods of hydrodynamics and thermodytiamics to practical meteor- 

 ology and hydrography. (For previous reports see Year Books Nos. 5-15.) 



The investigations in dynamics and thermodynamics of the atmos- 

 phere have been continued. 



The aerological observations obtained from the region of the North 

 Atlantic trade-winds by the expeditions of A. Lawrence Rotch, Teis- 

 serenc de Bort, and Hergesell have been worked out by Mr. Sverdrup 

 in his paper "Der nordatlantische Passat." The investigation gives 

 a tolerably complete idea of the dynamics and thermodynamics of the 

 trade-winds of this region. This result is very encouraging, as it may 

 be concluded that it will be relatively easj'' to perform a complete 

 investigation of the meteorology of the tropics. A ship cruising for a 

 j^ear or two in the Atlantic, the Indian, and the Pacific Oceans, making 

 aerological observations, should be able to bring sufficient data for 

 working out the dynamics and thermodynamics of the atmosphere in 

 all the principal trade- wind and monsoon regions. This would be 

 a good advance toward a complete theory of the great atmospheric 

 circulations. 



Returning to the more complex meteorological phenomena of our 

 latitudes, the question of a rational dynamic prognosis has been made 

 the subject of investigations.^ The problem in its most elementary 

 form has been this: wind and pressure being given at 8 a. m., calculate 

 by use of the hydrodynamic equations the wind at 11 a. m., and so on. 

 For this investigation observations obtained from the U. S. Weather 

 Bureau have been used. Our efforts have had no direct success. The 

 differences between the calculated and the observed winds were always 

 great and irregular. This failure was not unexpected; careful exami- 

 nation indicated that its causes were: 



1. Meteorological observations as we get them at present give, on 

 account of the many local influences, very incorrect representations of 

 the true atmospheric states. 



2. Atmospheric friction in the neighborhood of the ground is an 

 exceedingly complex function both of the topographical configurations 

 and of the momentary atmospheric conditions. 



This statement allows us to draw with great probability an impor- 

 tant conclusion : the precalculations should have good prospect to suc- 

 ceed if based upon observations taken, not at the ground, but at a height 

 of, say, 1,000 meters above the ground, i. c, at a height where both 

 functional resistance and local influences from the ground have prac- 



*Cf. Sverdrup and Haltsmark's paper: Ueber die Reibung an der Erdoberflache iind die 

 direkte Vorausbercchnung des Windes mit Hilfe der hydrodynamischen Bewegungsgleichungen. 



