MOVEMENTS OF ATMOSPHERE GULDBERG AND MOHN 179 



Writing 



du dv dw 9 . 



dx dy dz 



the equation of continuity assumes the form 



- P + P J =0 (3) 



dt 



In the preceding equations 



du dv , dw 

 — , — and — 

 dt dt dt 



represent the components of the whole force; the forces produced 

 by the variation of the pressure are represented by 



I dp t 1 dp 



— — and — — 



p dx p dy 



P 



which are the components of the horizontal force - G 



P 



and by — — — 



p dz 



which is included in the vertical force - H . 



P 



The components A', V, and Z are the components of the exterior 

 and interior forces. 



The exterior forces are the two following: 



Gravity. This is the resultant of the attraction of the globe and 

 of the centrifugal force produced by the rotation of the earth. 

 The direction of gravity is normal to the surface of the earth and 

 is represented by the axis Z. 



Gravity has therefore only one component — g, and by introduc- 

 ing the vertical gradient H, we have 



tH= -g- l J-l. 



p p dz 



We consider the force of gravity as constant, because the winds that 

 we are studying are located in the lower strata of the atmosphere. 

 The dejiecting force of the rotation of the earth. This compound cen- 

 trifugal force is the force that we must add to the exterior forces 



