MOVEMENTS OF ATMOSPHERE GULDBERG AND MOHN 



217 



§31. Velocity of propagation of a cyclone 



As we shall now explain, the movement of the barometric min- 

 mum is due to the heterogeneity of the air. At the front of a cyclone 



the alimentary air whose tem- 

 perature is r, enters and pro- 

 duces a lowering of the pres- 

 ''° * sure that we denote by d v At 



. ^_ jpr the rear of the cyclone the sup- 



\(?2 £° '/ plementary air (see §24) whose 



temperature is r 2 , enters and 

 produces an increase of pressure 

 whose value is d 2 . The air of 

 fig. 33 the central part of the cyclone 



has the temperature r and we 

 have Tj > t > t 2 . In accord with equation (4) of §27 we write 



J,_0.18^i±«(r-r,) (1) 



■ ^o.lS^i^r-r,) (2) 



Designating the variation of the pressure at the center by d 2 and 

 assuming that this variation occurs at all points, we can substitute 

 successively y = it and y = o in equation (3) of §30, then we shall 

 have 



d x = d 6 - 0.0324 G W (3) 



d 2 = d + 0.0324 G W (4) 



Eliminating between these four equations we shall find 



J.-0JL8 y *^*'(r-?L±*) (5) 



W = 2.78 — ° cos ^ . Tl ^l^ (6) 



Go r o 



If we have r = ^(x l + t 2 ), the pressure at the center remains 

 constant ; if t is greater than the mean of z x and r 2 , the pressure at 

 the center increases; if r is less than this mean, the pressure at the 

 center diminishes. 



