C, Meteorology 



The period covering tho ATKA^s operations in the Antarctic area 

 (12 January to 21 February) fell withdn the summer season when climatic 

 conditions were most favorable. The Ross Sea, Cape Colbeck to Palrr.er 

 Peninsula, and Weddell Sea areas showed a general seasonal trend in 

 temperatures j the temperatures gradually deci'easlng until the lovrest 

 air temperatures were observed in the latter area. Temperatures were 

 observed hourly at the weatherscreen which was located hh feet above 

 normal load line and v/hich was obstructed by the bridge when the wind 

 was from the starboard side. Temperatures taken with a sling psychrome- 

 ter at the quarter deck level 15 feet above noimal load line showed 

 somewhat lower values when the wind was from the starboard side and 

 over 20 knots velocity, Aerologists also made hourly temperature 

 observations at the quarterdeck level, between 13 Janxiary and lit 

 February as a special accomodation, to obtain values more representa- 

 tive of the temperatures near the ice surface. Quarterdeck temperatures 

 varied with the wind direction and velocity and showed values which were, 

 at most, 2° F. lower than those obseinred at the weatherscreen. 



The maxLmiua temperature observed on the ship was it2° F,, at Brans- 

 field Straitj the minimum temperature observed on the ship was 7° F,, at 

 Atka Bay, Temperatures on tho shelf ico were somewhat lovxer, the minimum 

 observed being slightly below 0° F., at Atka Bay, Surface wind speeds 

 showed a slight increase as the season progressed^ the maximum id.nd 

 speed observed in the Ross Sea area was 31 Imots and in the other two 

 areas 38 and 1x3 Icnots, The average daily majcimum iv-ind speed was 21.9 

 knots. The predomimmt wind direction in the Ross Sea area was east, 

 in the area from Cape Colbeck to Palmer Penins\ila southwest, and in 

 the Weddell Sea south-southwest. Calms prevailed h percent of the 

 time in the Ross Sea area and less than 1 percent of the time in the 

 two other areas. 



The first few days in the Antarctic v;ere spent in the Little America 

 area and were unusualD.y clear and sunny, a condition which was rarely 

 encountered during the remainder of the ATKA's stay in the operational 

 area. The last day in the Antarctic, at Admira3. Byrd Bay, also was 

 bright and clear, but during the greater part of the Antarctic portion 

 of the cruise, Eid.es vje re overcast and the sun seldom seen. In all 

 three areas lovr overcast skies were the dominant feature, occurring 

 7U,3 percent of the tijr.e in the Ross Sea area, S3»h percent in the Cape 

 Colbeck to Palmer Peninsula area, and 5i|.,3 percent in the ¥edde31 Sea 

 area. While at Kainan Bay, the sky to the north shoived a very '-ark, 

 stoiTiiy appearance during the 3 days tho ship v-as tied up to tho fast 

 ice of the bay (see p].ate VIII), Veterans of pi^evious expeditions 

 stated that this sky was typical for the area during the summer, but 

 to the nevj-comers it appeared as though a treinendous stoim vrere about 

 to occur any irdnute. On tho shelf ice and fast ice of the bay, "white- 

 out" conditions xijere conaon, especia3.1y in the Ross Sea area. Visibility 



It6 



