Blizzards are very common in the Antarctic, but usually do not 

 extend far out over the sea. They are rare during the smnmer 

 period of November, December, and January, but are frequent 

 during the oMtiimn and ivinter months. The duration of a bliz- 

 zard may be anything from a few hours to several days. The 

 early indication of an approaching blizzard is the covering of the 

 sky by light cirrus clouds which progressively become thicker, 

 darker, and lower. Existing winds may steadily increase in force, 

 or the blizzard may be preceded by a period of calm suddenly re- 

 placed by strong winds of 40 m.p.h. During the blizzard the wind 

 holds steady in direction and carries large quantities of drift snow. 

 Gusts of high velocity may be experienced, particularly towards 

 the end of the disturbance. A period of calm usually follows a 

 blizzard, after which the direction of the wind suddenly changes 

 180° and continues to blow with great force. This is character- 

 istic of the passing of a cyclonic storm center. 



Most blizzards are associated with northerly winds ; that is, the 

 blizzards are preceded by winds from that quarter. This is not 

 always the case. Often a blizzard will commence without previous 

 northerly winds and it is not until after the blizzard ceases that 

 the wind shifts to that direction. 



Large temperature increases have been noted with southeasterly 

 blizzards, especially during the winter months; in the summer 

 months the rise is not so marked owing to the less frequent tem- 

 perature inversions. This phenomenon suggests foehn winds, and 

 is due to adiabatic heating, the air descending from the plateau 

 being compressed in striking terrestrial obstacles. The effect of 

 this temperature rise is conspicuous at the mouth of the glaciers 

 descending through the Queen Maud range. 



The weather is extremely variable. Usually it changes in 

 cycles, with the period of southerly winds lasting longer than 

 northerly winds. 



Fog is not infrequent in the region of icebergs and pack ice, 

 and along the coasts of Antarctica. Frost smoke is common over 

 open water areas during the autumn months. 



Rain occurs frequently in the northern part and along the west 

 coast of the Palmer Peninsula. It is rare in other parts of the 

 continent. Precipitation is almost invariably in the form of snow 

 or hoarfrost but the quantity deposited varies in different areas. 

 Measurements have been of little value due to the great amount 

 of drift swept by the winds. 



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