28 METEOROLOGY 



We may return to the subject of the winds of the Magnetic Pole Plateau and the 

 snow supply. It would appear that little snow falls on the centre of the plateau in 

 summer time. During the five weeks that we were on the plateau, from December 25 

 to January 30, probably not more than one quarter of an inch of snow fell. The 

 winds and their relation to snow supply on the Antarctic Plateau of the South 

 Magnetic Pole Region may be summed up, very tentatively, as follows : 



1. Anticyclonic winds, surface winds, mostly dry and cold, of two types : 



(a) The local surface plateau wind which parts at the summit of the Magnetic 

 Pole Plateau into two air currents : 



(i) The W. by N. curi'ent blowing into Ross Sea. This is mostly a 



cold dry wind which does not produce snow on the plateau, but acts 



as a condenser and snow producer along the coast, where it meets 



the relatively warm, moist air over Ross Sea. 



(ii) The S. to S.E. plateau wind blowing from oft' the summit of the 



plateau towards the Southern Ocean in the direction of Adelie 



Land. This brought a little snow with it, and probably represented 



the high-level N.W. cyclonic cuirent which had dived as it became 



chilled inland, and then, after reaching the surface, became 



reversed. 



(J)) The blizzard wind which forms part of a larger intermittent atmospheric 



circulation blowing spirally outwards from the " Temperature Pole," 



or poles. Whereas on the west coast of Ross Sea the direction of the 



blizzard is nearly N. and S., on the edge of the plateau nearest the great 



horst it is about W. 30 S. This, it may be pointed out, agrees with 



Scott's observation as to the direction of the blizzard wind on the plateau 



at the back of the Ferrar Glacier, viz. that it had more southing in it 



than the normal plateau wind. Although we experienced a plateau wind 



of the violence of a mild blizzard (about 25 miles an hour) on January 8, 



1909, we did not encounter any violent blizzards at all on the Magnetic 



Pole Plateau on our journey between Dec. 24, 1908, and Jan. 30, 1909. 



2. Cyclonic winds : 



(a) The local high level N.E. air current from off" Ross Sea. This carries 



open water. Later the same clay immense cloud pillars covered the top of Mount Larsen. On January 4, 

 1909, rolled cumulus spread fast over the Magnetic Pole Plateau coming from the N.W. towards the S.E., 

 that is from the direction of the Southern Ocean near Ad61ie Land. This was over 100 miles inland from 

 the Ross Sea. 



On January 5, 110 miles inland, the sky except to the S. and S.E., was thickly overcast with snow- 

 clouds. The air at the surface was calm. These den.se snow-clouds had evidently come in from the N.W., 

 but, as this day was comparatively warm, they may have been added to by vapour derived from the 

 sublimation of the snow surf.ace of the plateau. On January 8 we experienced a blizzard with much 

 low drift. It was of a mild order, and slackened towards evening. We have no record of fre.sh snow 

 falling on this occasion— apparently the drift snow was all old snow, but this is not certain. This was UO 

 miles inland. 



