MOVEMENTS OF ATMOSPHERE GULDBERG AND MOHN 



177 



the height z. We shall call 77 the pressure reduced to the surface of 

 the earth. We call the horizontal lines that correspond to the values 

 of 77, the reduced vertical isobars.' We call the difference of two 

 values of 77 expressed in millimeters divided by their distance ex- 

 pressed in degrees of the meridian the vertical gradient. Denoting 

 the vertical gradient by 77, the coefficient of reduction by /x (see §7) 

 we have 



- uH 



d 77 dp da dp , 



= — — + — - = — + gp 



dz dz dz dz 



(2) 



The sign minus is taken, because Ave consider the vertical gradient 

 positive upward in the direction in which the pressure 77 diminishes. 

 As regards the rectilinear motion we find from §15 



ft H = p .w 



dw 

 dz 



(3) 



Introducing d IJ we find by integration 



n = p - p w (w - w ) 



If in the formulae of §15 we substitute 



T = 290°; m = 6; p = 760 ,nm ; w = 20 m 

 we shall find the results contained in the following table: 



(4) 



By constructing the curve of 77 as a function of z we shall find the 

 reduced vertical isobars as we see in fig. 1 66. The difference between 

 p and 77 we shall call the vertical depression. In the same way that 



the horizontal gradient G produces a horizontal force - G (see §7) 



9 P- 

 so does the vertical gradient 77 produce a vertical force - 77, which 



