30 



POLAR PROBLEMS 



40OO 



m. 



3000 



2000 



1000 



-50 



-40 



The computations of W. H. Dines ^ based on careful physical 

 measurements and observations in the free air show that in the lower 

 atmosphere in high latitudes, as well as near the equator, heat is 

 being radiated away more rapidly than it is absorbed from solar or 

 earth radiation, so that the air below 8ooo meters is continually 

 losing heat which has to be supplied in some other form, as by con- 

 vection or otherwise. On the other hand the highest strata above 

 10 kilometers are gaining heat which must be dissipated in some way. 



There are hence two causes for 

 the cooling of the air in high lati- 

 tudes in winter. One is the radia- 

 tion of heat into space from the 

 earth's surface and the other is ra- 

 diation from the air itself. This 

 cooling of the atmosphere is the 

 result chiefly of radiation from 

 water vapor. The lowest tempera- 

 tures are found in the upper part 

 of the vapor stratum, in the polar 

 area at an elevation of about 8 kilo- 

 meters, because there the amount 

 of heat lost to space is not com- 

 pensated for in part by heat radi- 

 ated back from higher strata. The 

 resulting distribution of tempera- 

 ture from these two causes is a 

 marked cooling of the air near the 

 earth's surface in high latitudes in winter and a still more marked 

 cooling at a height of 4 to 8 kilometers. 



Observations of conditions in the free air on the edge of the 

 Antarctic Continent made by Dr. G. C. Simpson^ on the polar side 

 of McMurdo Sound, in the southwestern corner of Ross Sea in 

 about 78° S., show that the mean temperature during quiet weather 

 in winter, on days when it was possible to launch small sounding 

 balloons, was about -35° C. at the earth's surface. At 800 meters 

 the temperature was higher, being but slightly below — 30° C. Above 

 1000 meters the temperature fell with increasing height and was 

 — 43° C. at 4000 meters. (See the continuous curve in Figure 4.) 

 Observations were obtained in the Arctic Sea between the New 

 Siberian Islands and Wrangel Island by Dr. H. U. Sverdrup^ at latitude 



2 W. H. Dines: Atmospheric and Terrestrial Radiation, Quart. Journ. Royal Meteorol. Soc, 

 Vol. 46, 1920, pp. 163-173. 



^G. C. Simpson: Meteorology, Vol. I: Discussion, [Scientific Results of the] British Antarctic 

 Expedition, 1910-1913, Calcutta, 1919. p. 45. 



< H. U. Sverdrup: The North- Polar Cover of Cold Air: Preliminary Results from the Maud 

 Expedition, Monthly Weather Rev., Vol. S3> 1925. PP- 471-475; reference on p. 471. 



-30 -20 -lO-C 



Fig. 4 — -The temperatures at different 

 heights on the edge of the Antarctic Continent 

 in winter observed by G. C. Simpson with 

 captive balloons (shown by the full curve at 

 the left). For comparison the curve of Fig. 5, 

 Arctic winter temperatures on windy days, is 

 added as a broken curve. (Antarctic curve 

 from Fig. 15 of work cited in footnote 3 as 

 reproduced in paper cited in footnote 4.) 



