MOTION OF THE UPPEE ATMOSPHERE. 



Table 71. 

 Cape Adare wind. 



131 



Tlie outstandiuf; feature of the Cape Adare wind is tiie large imniber of caliiis and the 

 consequent small mean velocity. It is remarkable to find 36-8 per cent, of calms and a 

 mean velocity of only 7-.'? miles an hour at a place situated on the coast of the stormiest 

 ocean 'in the world. It is possible however that the surrounding land masses are largely 

 responsible for the large number of calms. Robeitson Bay in which the .station was situated 

 is nearly surrounded by high masses of land except on the north (see figure 3, page 7 ) ; it 

 may have been that the air was calm within the bay while moderate winds blew outside. 

 On the otlier hand Cape Adare shows the storminess of its situation by the relatively large 

 number of high winds. During the 10 months 31 per cent, of ti\e time the wind was blowing 

 with a mnd strength of 10, 11 or 12 on the Beaufort Scale, or reduced to miles per hour 

 3 pn- cent, of the time the wind was over 60 miles per hour. 



The mean direction was S.E. but the direction with the greatest total wind and also the 

 greatest mean velocity was E.S.E. It is likely however tliat the wind direction was affected 

 by the surrounding mountains, but there can be no doubt that even with a free exposure 

 the chief wind direction would have been between 8. and E. 



As far as it is possible to judge the yearly variation of the wind is very diiierent at 

 Cape Adare and Cape Evans. Tlie two winter months, June and July, were the most 

 calm of the ten, while May and September were the most windy. During eleven months in 

 1899-1900 August had the least wind and March the uKJst. Two years are too few to give 

 the true yearly variation, but there can be little doubt that there is less wind in the winter 

 months than at any other time of the year. 



Motion of the upper atmosphere. 



The winter stations of the British Antarctic Expeditions in McMurdo Sound have been 

 fortunate in having within sight the active volcano Mount Erebus the smoke cloud from which, 

 issuing at 13,000 feet (4,000 metres), gives a ready inde.x of tlie air motion at and above 

 this height. It must, however, be pointed out that it is not at all easy to judge the direc- 

 tion in which smoke is moving especially when, as often happened, the smoke cloud is small 

 and has disappeared at a small distance from the top of the mountain. I believe however, 

 from my personal experience, that after a little practice the direction of the cloud when 

 visible can be judged with accuracy to one of eight points of the compass. But it often 

 iiappened that little or no smoke could be seen. This was due to two causes, first because 

 no smoke was issuing, and secondly because the smoke as it issued was going directly away 

 and w^as therefore hidden by the mountain. A small amount ot cloud like a small knob 

 could often be seen just at the position of the crateT-. At first I thought this indicated that 

 only a very small quantity of smoke w-as issuing and I entered in the register ' knob ' 

 to record it. I afterwards recognised that this knob was in all probability the stem of the 

 smoke column up to the point reached by the cloud before being blown directly away by 

 a S.W. wind, Erebus being due N.E. from Cape Evans. It was impossible to be certain 

 of the point from the appearance of the cloud itself, but on working up the results it was 



