MOVEMENTS OF ATMOSPHERE— GULDBERG AND MOHN 



Therefore in the northern hemisphere the cyclone moves around 

 the alimentary stratum against the sun and inversely in the south- 

 ern hemisphere (see fig. 37). When the cyclone passes by any point, 

 the temperature is lowered at first and then increases, and during 

 the passage of the center it is lowered again to finally increase 

 (see fig. 38). 



r, 



r 



FIG. 38 



The cyclones of the inter-tropical regions, at least certain of them 

 described by the meteorologists of the East Indies, seem to belong 

 to the last class. However, the thermometric and hygrometric 

 observations in the cyclones of low latitudes are unfortunately 

 still too rare for it to be possible to determine the position of the 

 alimentary stratum and the extent of the arc traversed by the ali- 

 mentary air before it commences to ascend in the anterior portion of 

 the interior circle. 



§32. Isobars of a variable cyclone 



We shall distinguish three cases: 



(1) Stationary cyclone. 



The isobars of a stationary cyclone are concentric circles that 

 change their size at the same time that the barometric minimum 

 varies. Consequently, the curves of equal variation of pressure are 

 also concentric circles. The variation of the pressure d is a func- 

 tion of the distance r. We can approximately determine this vari- 

 ation by calculating two cyclones whose parameters are different. 

 For example, suppose that the radius r be the same in each and that 

 the maximum velocity U diminishes during a certain time. By 

 the formulae of § 13 and § 14 we have calculated the following tables, 

 assuming 8 = 50 and k = 0.00010: 



