150 



CLOUD AND PRECIPITATION. 



It therefore appears that 63 is probably the mean value of the cloud amount for the 

 whole of the Ross Sea area. This is a very low value compared with that of other Antarctic 

 .stations as is shown in the following table. 



T.\13LE 79. 



As stated above, the mean value of the cloud amount does not give the most satisfactory 



indication of the cloud conditions. It is much better to count the number of times each 



grade of cloud 0, 1, 2 10 was recorded and express the result in percentages of all 



the observations. 



Table 80. 



Percenta.ge freqiiencij of each Cloud Ainount at Cape Evans fi/earli/ mean; obtained from March 



til October two years, November to February one year). 



We see here the usual feature of cloud observations, that clear skies and overca.st skies 

 are observed more frequently than any other cloud number. That the frequency decreases 

 from each of these maxima towards the centre of the scale shows a strong tendency for the 

 sky to be either entirely clear or entirely overcast. 



The following table gives similar data for Cape Adare. 



Table 81. 

 Percentage frequency of each Cloud Amount at Cape Adare (yearhj mmn). (Observations, March 

 io December. Janmry and February, taken the same as December and March respectively J. 



Cloud amount 



Cape Adare 



lo-4 



79 



50 



3-4 



4-6 



3-7 * 



3-2 



43 I 61 



11 7 



33 6 



* It is well known that in all estimations there is a natural tendency for the group 5 to be increased at 

 the expense of groups 4 and 6- This is clearly shown in the tlble, and therefore the three groups 4, 5 and 

 6 should be considered together- 



