144 



WIND. 



Tahlk 7(1. 

 Wiiul oil Soiil/i Polar Phdeaii f S.=j)iinill<'l In l<iO° E. iiicridiai/.J 



Frequency. — It \\'ill be seen that in essentials Scott's and Amundsen's observations give 

 the same results. The most frequent winds were the S.S.E., S. and 8.S.W. these three direc- 

 tions containing 73 per cent, of Scott's observations and 54 per cent, of Amundsen's or 63 

 per cent, of all the observations, no other direction has 4 per cent, of the total \\inds. 

 The mean direction as determined from Scott's observations was S. 3 E. and from Amundsen's 

 S. 19 E. and combined S. 10 E. 



The frequences of the combined observations are shown in fioure 47(12). 



Velocity. — The mean velocity according to Scott's observations was 11-8 miles an horn 

 and according to Amundsen's 10-7 miles an hour. This is a very close agreement and the 

 combined velocity 11-2 miles an hour is probably very near to the velocity during December 

 and January, 1911-12. The average velocity during the same two months at Cape Evans 

 was 12-8 miles an hour and at Framheim 94 miles an hour. Thus, there was little difference 

 in the velocity on tlie plateau and on the Barrier nearly 10,000 feet l^elow. The mean 

 velocities for the different directions do not show any very pronounced features, but in the 

 next section it will be shown that the majority of high winds blew from the S.S.W., S- 

 and S.S.E. The resultant directioit is, Scott S. 3 E., Amundsen S. 30 E. This is a larger 

 difference than was found in the case of the mean direction and is mainly duo to a period 

 of three days, during which a high wind blew from directions between S.E. and E.N.E. 

 shortly after Amundsen reached the plateau. This period will be discussed below. 



Total IFw(fZ.— The air motion from all directions except S.S.E., S. and S.S.W. is practically 

 insignificant, these three directions together take 75 per cent, of all the air motion. This 

 result combined with the high frequency of the winds from these directions points to an 

 almost constant pressure gradient driving the air along the resultant direction, i.e., along 

 S. 14 E. or parallel to the 146° E. meridian. A glance at tlte map, which forms the frontis- 

 piece of this volume on which the probable edge of the plateau is indicated, shows that this 

 direction is very nearly parallel to the main trend of the plateau escarpment. As the wind 

 friction must be small on the plateau the air motion is probably very nearly along the 

 isobars, hence the wind observations on the Polar Plateau indicate isobars rmming more or 

 less parallel to the edge of the plateau, with the high pressure over the plateau and the 

 low pressure over the Barrier. 



Plateau Winds and Blizzards. 



Until the meteorological observations made b\- the Sh.ackleton and Mawson expeditions 

 are published, we have not suthcient data to discuss the blizzards on the plateau near the 

 magnetic pole ; we nuist, therefore, limit our discussion to the observations made on the 

 Western Plateau and Polar Plateau. 



Western Plateau.— Dnimg the period that Captain Scott was on the Western Plateau he 

 experienced several periods of high winds.' In order to investigate whether these high winds 



