930 
response to the thorough publication of the more ex- 
tensive Highjump data, whose use has just begun 
[60, 91]. At Macquarie and Heard Islands, the Aus- 
tralians [69] began daily radiosonde observations early 
in 1948, and at Marion Island, the South Africans [92] 
began regular radiosonde ascents in May 1949. During 
February 1949, twenty-five flights were made from the 
Commandant Charcot |71] off the Adélie Land coast, 
south of Australia between 136°EH and 164°H, as it un- 
successfully tried to land a French expedition which did 
establish a base a year later. 
MILLIBARS 
—--- OPERATION HIGHJUMP 
—-— ARCTIC BAY 
Fig. 1.—Antarctic and arctic summertime soundings. The 
curve for Little America III (78°30/S, 163°50’W) is based on 
thirteen soundings during the period 1-15 January 1941 [47]. 
The curve for Operation Highjump (70°-75°S, 160°W-165°E) 
is based on thirty-four soundings from 14 January to 8 Feb- 
ruary 1947 [8]. The data for Arctic Bay, Canada (73°16’N, 
84°17’W) are from 152 soundings during July, 1943-47 [134]. 
The tropopause at Arctic Bay was computed separately. 
Despite these extensive summertime soundings, the 
1940-41 series provides the only information to date on 
the entire troposphere and lower stratosphere through- 
out the year. The 265 days covered by the 1940-41 data 
can be extended another twenty-two days by the 13 
Highjump flights made from ships in the Bay of Whales 
and 21 others made in the Ross Sea south of 75°S. 
Close agreement between the averages of these 34 
shipboard ascents and the 13 at Little America six 
POLAR METEOROLOGY 
years earlier is shown in Fig. 1; also plotted for com- 
parison are the average temperatures of the warmest 
month, July, at North America’s coldest aerological 
station: Arctic Bay, Canada (73°16’N, 84°17’W, 11 m 
m.s.l.), the only station on the continent at which the 
mean monthly temperature at 850 mb is never above 
freezing [134]. 
Wintertime. The Little America soundings show the 
tropopause in summer at roughly 9 km, —50C, and 
slightly higher and much colder in winter, at 10 km, 
—70C. The annual variation in stratosphere tempera- 
tures and lapse rates is so great that in summer it is 
warmer than —40C above 14 km, while in winter the 
stratosphere lapse rate approaches that of the tropo- 
sphere and the tropopause tends to disappear [45]. 
Interpretation of the wintertime soundings is difficult 
because the extreme cold imposed an effective ceiling on 
the balloons, so that the higher soundings were all in 
warmer-than-average air. This tendency is shown by a 
diagram (Fig. 2) of the extreme temperatures at each 
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TEMPERATURE (°C) 
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Fic. 2.—Observed temperature extremes and absolute range 
| A7'| at standard levels over Little America III [47]. Dates 
are those of individual soundings. A dry-adiabatic (@ = const) 
is drawn for comparison. 
kilometer level, with portions of the soundings in which 
they occurred. The envelope thus formed is smooth for 
both extremes in the troposphere and for the warmest 
values in the stratosphere, but shows that the coldest 
stratosphere temperatures always occurred in soundings 
which terminated soon thereafter. 
From June through September, none of eighty-eight 
soundings (one with a 700-gram balloon) rose to 18 
km, only two to 17 km, three to 16 km, and five to 15 
km. At 17 km, temperatures were —70.8C on 5 June 
and —75.8C on 14 September. At 16 km, these same 
soundings gave —69.2C and —75.0C, but the third 
