DAILY VARIATION— SEPTEMBER TO MARCH. 



57 



isimultamious teiuperatureB at Cape Evans, while the minimum temperatures are very umch 

 lower. It is therefore not abnormally high temperatures, but abnormally low temperaturec 

 which cause the large temperature amplitude. 



Fig. 22b. Simultaneous temperature on Barrier and at Cape Evans. 

 Daily Tem/perature Variation at Frnmheim. — ^It has been stated that the temperatures at 

 Framheim were similar to those of the Barrier. It would therefore have been interesting 

 to compare the daily variations at that station with the observations made on sledging 

 journeys. Unfortunately temperature observations are only available at Framheim for the three 

 hours of observations, 8 a.m., 2 p.m. and 8 p.m. These observations, however, show that the 

 amplitude at Framheim was very nearly that measured on the open Barrier. 



The relationship is clearly shown in the following table in which the same days have 

 been used in each case for calculating the means :— 



Table 22. 



The large daily amplitude on the Barrier is therefore supported by the observations 

 made at Framheim, and it is the largest amplitude yet measured in any polar region. 



That the daily amplitude of temperature on the Barrier should be between two and three 

 times greater than in McMurdo Somid points to some essential difference in the thermal 

 conditions of the two places. The effect of solar radiation will be considered later, but it 

 may be stated here that the variations of solar energy during the day were less on the 

 Barrier than at Cape Evans, and therefore they are unable to account for the large difference 

 in temperature variations. Under the same conditions of solar radiation the temperature 

 of the air vnW depend entirely on the nature of the ground upon which the radiation falls, 

 for the radiation does not warm the air directly, but only by first warming up the ground 

 on which it falls. Now the Barrier is composed entirely of snow, which is never closely 



8 



