WIND VELOCITY AND SURFACE PRESSURE GOLD 117 



The pressure at a height z above B the point of intersection of p , 

 T , is p e ~ z,k T m, and above A, the point of intersection of p + dp , 

 T - dT , is 1 



{p + dp,)e-* /k(T m- dT m>- 



If we assume the vertical temperature gradient to be the same 

 over all the region considered, d T will be the same for every element 

 of the above integral, and we can put dT m = dT . 



If these two pressures at height z are equal, we must have 



or 



dPo = z _ dT o or d Po 



N\p +rfp 

 FIG. 4 



In this case A B is the direction of the upper isobar and its incli- 

 nation <j> to the lower isobar is given by 



ydpo 



tan<i = 



xd T Q cosec </» + ydy cot </» 



where xdT and y dp are the distances between the isotherms and 

 isobars. 



Substituting for dT and dividing out by dp we get 



x T 2 

 cot <f> = cot (J) + ^— cosec (p. 



ygpozT« 



Taking y and x for millimeter isobars and i° C. isotherms and 



putting z = 1000 meters and T„?/T = 2T m — T = 270 C. say, 



we find 



x 

 cot 4> = cot i[> -|- 2 '8 - cosec <p. 



y 



x ln. this and subsequent formulas the reader will understand that the 

 erms following the / belong to the exponents of e. 



