46 



TEMPERATURE. 



From these con.siderations wo should expect the temperature in winter during winds to 

 be considerably higher than during the calms. 



The first effect of a wind under such conditions is to raise the temperature cjuite 

 independently of the direction from which it comes. But when the wind has removed the 

 cold surface layers the temperature it produces will depend on the direction from which 

 it comes. Thus we should e.xpect both southerly and northerly winds to be warmer than 

 calms, but the former to be themselves colder than the latter. This is clearly shown to be 

 the case during the months from June to September by the mean temperatures entered in 

 the first four lines of the follovring table : — ■ 



Table 18. 

 Temperature and Wind at Cape Evans. 



During these four months the temperature during calms (column II) was considerably 

 lower than during either northerly or southerly winds (columns III, IV and V). The differ- 

 ence in temperature between northerly wind.s having velocities between 11 and oO miles per 

 hour and calms is shown in column VI and for similar southerly winds in column VII. 

 It will be seen that both northerly and southerly winds raise the temperature by over 10°F. 

 It was stated above that the more violent winds as they disturb the atmosphere to a 

 greater height should be warmer than the less violent winds [curves (6) and («) in figure 

 15]. This is clearly seen to be the case by comparing columns IV and V, which give data 

 for winds from the south having velocities of 11 to 30 and greater than 30 miles an hour. 

 The higher winds, although from the same direction, are nearly 8°F. warmer than the less 

 violent winds. The same was found to hold for northerly winds, but they occurred too 



