522 



H. MOHN. METEOROLOGY. 



[nORW. POL. EXP. 



ANNUAL PERIOD. 



The following Table gives the average monthly number of cases in which 

 the different forms of cloud are found by bi-hourly observations during the 

 24 hours. 



The different forms of cloud have their maximum of frequency in the 

 warmer part of the year, and their minimum in the colder part, as is the 

 case with the amount of cloud in general. We find an exception in the 

 cirro-stratus cloud, which has a chief maximum in January, and only a 

 secondary maximum in July. Stratus has the largest range, and cumulo- 

 stratus comes next. 



The total frequency in the whole year ranges thus — stratus, cirro-stratus, 

 cirrus, strato-cumulus, cirro-cumulus and cumulus. True cumulus clouds are 

 rather scarce even in the summer, and it is a question whether this form 

 really occurs after all in its typical form. 



The expedition started in 1893, and the International Cloud-Atlas was 

 published in 1896. 



CLOUD MOTION. 



The following Tables show the number of cases in which the different 

 forms of clouds have been noted moving from the respective points of the 

 compass (true direction) during the drift of the Fram. The higher forms of 

 clouds are treated separately, the lower clouds comprise cumulo-stratus, 



