TEMPERATURE AND WIND. 



45 



During a higli wind there is so mucb forced vertical mixing of the air that the temperature 

 gradient becomes roughly adiabatic in the air layers affected. We have no upper air tem- 

 perature observations during high winds in the Antarctic, but from general considerations 

 we know that the gradient must then be between 6°C. and 7°C. per 1,000 metres. ]n 

 figure 15 the thick curve represents the vertical temperature distribution during cold calm 



-50°c -45°c -40c -35c -30c -25c -20c -15c 

 Temperature 



Fig. 1.5. Effect of removing inversion Layer. 



weather as found by the balloon observations. The inversion up to 1,000 metres is shown, 

 and from there upwards the temperature falls 4°C. per 1,000 metres. If now a wind springs 

 up the lower cold layers are swept away, and if it disturbs the air up to 2,000 metres 

 a temperature gradient of about 65°C. is set up in this region. The temperature of the 

 air above 2,000 metres will not be materially affected but from this point downwards the 

 temperature rises 6'5°C. for each 1,000 metres. The new temperature conditions are shown 

 by the line (a) in the diagram. 



Before the wind sprang up the ground temperature was — 35°C. and by the time the 

 wind has produced the gradient the temperature has risen to — 22°C., i.e., the wind has 

 produced a rise of 13°C. = 23°F. If the Avind had disturbed the air to 4 kilometres 

 the temperature would be indicated by the line {h) which represents a rise of the ground 

 temperature of 18°C. = 32°F. 



