tures it was decided to name them differently; cP air was the 

 name given that on the plateau, and the air along the coastal area 

 and ice pack was called, continental antarctic (cA). 



"The above discussion has been concerned with cA air along 

 the coast and over solid pack where there are no areas of open 

 water. If, however, this cA air does pass over water, a rapid 

 modification takes place similar to that occurring over the Great 

 Lakes in winter, and to the formation of polar Atlantic air. Since 

 this process occurs continuously with the production of large areas 

 of an air mass intermediate between cP and that normally termed 

 mP, and the name maritime antarctic (mA) was applied to it. 

 The term mA is used to describe cA air that has been modified by 

 a relatively short water trajectory, usually from 50 to 100 miles 

 minimum and up to 500 miles maximum, beyond which it assumes 

 properties similar to fresh mP air. The Antarctic Front is the 

 northern boundary of this cA or mA air mass. 



"The production of mA air can proceed rapidly as in the case of 

 the direct advection from solid ice to open water or slowly through 

 the advection of the air over open water present in the ice pack. 

 In the latter case, this water may be open water between the fast 

 ice and the pack, rotten pack ice, openings, and small bays. The 

 addition of moisture from this water gradually increases the mois- 

 ture content below the inversion. This continues with fracto- 

 cumulus forming first, then gradually thickening into a layer of 

 strato-cumulus which then develops vertically. The exact stage 

 of development depends on the total amount of previous water 

 travel. In estimating the total water travel of the air only the 

 trajectory of the air in the lower 500 to 1,000 feet should be con- 

 sidered, which involves considerable cross-isobar movement. It 

 is emphasized that this procedure must be considered in all cases 

 where the trajectory of the antarctic air must be estimated. 



Fisure A-2. — Admiral Byrd's Tenf Ciry, Little America IV. 



_g%L. t Jilt- iihi -"^V" ^^ ... .^i. j^i lift .it -'-^ -^ ' 



