48 Variations of Pressure, Temperature, and Wind. 



of the barometer. The changes in the variation with in- 

 creasing height must be taken into account. 



In order to proceed to a further approximation put 



gj 2 — kTx sin 2 <£ -^-r + gr 2 \ 



Then 



1 + 4 cos 2 $ 



™1 — 4cos 2 <£>' 



gr 2 '=2¥' 



n sim 



and this will be approximately correct except in the neigh- 

 bourhood of lat. 30°, where the effect of viscosity will add 

 to the denominator a term which will remain finite while 

 l_4cos 2 <£ decreases to zero. The value of Ci is still zero 

 to this order of approximation and consequently t x is also zero. 



But 



A 2 =-F / sin0(l-f4cos 2 <#,)/(l--4cos 2 ^), 



B 1 = 4F / sin $ cos0/(l— 4 cos 2 </>). 



Thus near the earth's surface A 2 is negative in the equatorial 

 regions and positive between lat. 30° and the pole : ~B 1 is 

 positive near the equator, negative between lat. 30° and 

 the pole. 



The nature of the horizontal motion in the two cases is 

 shown in the accompanying diagram. 



Motion in Diurnal Pressure- Wave. 



1. Lat. 0-30°. 2. Lat. 30°-90°. 



The arrows fly with the wind. 



