VERTICAL DISTRIBUTION OF TEMPERATURE. 



41 



experienced on the plateau by the two parties ; the following table has therefore been pre- 

 pared (see also figure 6) : — • 



Table 17. 

 Actual Teiiiperdtures on llie South Puhir Phtleau. 



Month. 



ObservtT Mean observed j Maximum observed j Minimum observed 



temperature. temperature. [ temperature. 



December 



January 



Ari.undsen _ 8-6'F= -22-6T \ +5o°F=-U-°C — 19-3°F=-28-r)°C 



Scott . . — lS-7'F = -28-2°C — 3-2°F = — 19'6°C ' — 29-7°F=— 34 S C 



Thus the mean actual temperature in December was — 8-6°F. It must be accounted 

 as one of the wonders of the Antarctic that it contains a vast area of the earth's surface 

 where the mean temperature during the warmest month is more than 8° below the Fahrenheit 

 zero, and where throughout the month the highest temperature was only 4-5'5°F. It should 

 also be noticed that the actual temperature on the plateau was lO^F. lower in January 

 than in December, indicating a very rapid lowering of the temperature immediately the solar 

 radiation commences to decrease. If this fall was not abnormal it indicates that the tem- 

 perature on tiie South Polar Plateau is influenced by changes in insolation much more than 

 any other place for which we have records. 



Vertic.vl Distribution of Temperature 



Having now used all the available data for discussing the geographical distribution of 

 temperature at ground level, we will turn to the question of its distribution in the upper 

 atmosphere.* 



In figure 13 are plotted all the observations made by the aid of balloons of the tem- 

 perature of the upper air over the frozen McMurdo Sound. In this diagram heights are 

 shown in metres and temperatures in centigrade degrees. 



It will be noticed that all the ascents made in November and December, summer months 

 (Nos. 5 to 10), show temperature decreasing with height and the mean gradient for the first 

 2\ kilometres is 6-8°C. per 1,000 metres. It is of great interest to notice that this is 

 practically the same gradient as tliat found in summer months in Europe and Ameiica 

 although the actual temperatures in the Antarctic summer are similar to those of winter 

 in those regions. 



The conditions are entirely different during the winter. On account of darkness upper 

 air observations could not be made before August. In this month, however, four successful 

 balloon ascents were made and the instruments recovered. The difficulties of the balloon 

 work in cold weather were so great that only moderate heights could then be reached. The 

 ascent on August 13, No. 1, was made on one of the coldest days of the year, the tem- 

 perature on the ground being — 39°C. at the time of the ascent. The temperature 

 record on this and on all other occasions in the winter revealed the temjjerature 

 inversion which is often met with on calm winter days in Europe and America. The inver- 

 sion extended higher on August 13 than on any of the other days, but it was not so 

 pronounced as on August 16. The curve for August 30, No. 4, is interesting as it was 



The upper air observations are discussed in detail in Chapter VIII. 



