104 



WIND. 



Yarmouth (Eng/and ). 

 Jubfeulpors ( India ). 



The frequency curves for Yarmouth and Jubbmlpore are ^ood examples of two distinct 



types of frequency curves, and before pro- 

 ceeding further we must consider what is their 

 meaning. There can be little doubt that they 

 indicate two different types of weather, namely, 

 the types associated with anticyclonic and 

 cyclonic pressure distribution. It is well known 

 that while air motion is essential to a cyclone 

 it is destructive of an anticyclone. It is 

 therefore clear that a place generally under anti- 

 cyclonic conditions will have more calms and 

 light winds than high winds, on the other hand 

 a place which is frequently visited by cyclones 

 can have very few calms, and there must, there- 

 fore, be some wind velocity which has a maxi- 

 mum frequency. 



The interior of India during the winter 

 is subject to strongly anticyclonic conditions, 

 and cahas are the most frequent wind values 

 experienced. On the other hand England 

 throughout the year is subjected to a succession 

 Fig. .S4 Frequencie.s of wind velocities. of cyclones, and calms are seldom experienced. 



Thus the pressure types in these two cases agree with the type of wind frequency. 



That the frequency type changes with the pressure type is shown by the summer 

 observations at Jubbulpore. In June, July, and August the mterior of India becomes an area 

 of low pressure. This is a cyclone which although of great extension is of little depth and 

 the gradients on the average are very small. Nevertheless the most frequent wind is no 

 longer in the first group but falls in the second group, the values being :^ 



Table .59. 

 Wiwl frequency at Jubhdpore During the Monsoon. 



Thus during these months Jubbulpore has the same type of frequency curve as Yarmouth 

 and both are subject to a cyclonic distribution of pressure. 



We have thus been introduced to two types of frequency curves. In one the relative 

 frequency increases as the velocity decreases right down to calnis ; this type is associated with 

 anticyclonic pressure conditions and therefore will be called the anticyclonic type. In the 

 other the frequency increases as the wind decreases down to a certain velocity after which 

 the frequency decreases as the velocity decreases and calms may have a very small frequency ; 

 this type is associated with cyclonic pressure distribution and therefore will be called the 

 cyclonic type. 



The v\ind observations at Cape Evans, Framheim, Cape Adare, Gauss Station and Snow 

 Hill have been investigated to find the type of their frequency curves, with the result that 

 all prove to be of the anticyclonic type. The data are contained in table 60 and the curves 



