Table 39 (concluded) 

 GEOSTROPHIC WIND, CONSTANT LEVEL SURFACE 

 Three millibar isobars, air density 1 kg. m.~ 3 



125 



where Am is the isobar spacing measured in degrees of latitude (i.e., one unit of Aw has 

 the length of one degree of latitude at the place for which the isobar spacing is measured). 

 Table 39 gives values of V , in knots as a function of An with auxiliary columns giving 

 equivalents of An in kilometers, statute miles, and nautical miles. If the latter are measured 

 by a map scale true at some other latitude the value should be corrected to the latitude at 

 which the measurements are taken (see Table 165). 



Since the geostrophic wind is inversely proportional to the isobar spacing and the 

 density p, and directly proportional to the isobaric interval (A/> mb.), values of V B for 

 1/10 of the indicated spacing may be found by multiplying the tabular values by 10, etc., 

 and for isobaric intervals other than 3 mb. by multiplying the tabular values by Ap/3. 

 The density p of 1 kg. m." 3 (0.001 gm. cm." 3 ) used in the computations is the average 

 density at about 2 km. above sea level ; for V a at other levels multiply the tabular values 

 by po/p (if the density is expressed in kg. m."" 8 , simply divide the tabular value by the 

 density). 



(To convert knots to other measures of speed see Table 35.) 



SMITHSONIAN METEOROLOGICAL TABLES 



