534 



H. MOHN. METEOROLOGY. 



[NORW. POL. EXP. 



We then have 

 the probability of precipitation 



T 



N the total duration of precipitation in hours 



r_N 

 n 



-j- the average duration (in hours) of precipitation in a day of precipitation. 



PI. IX (5 mm. = 1 hour). 



The duration of precipitation in a day of precipitation is, on an average, 

 7'38 hours. 1 There is an annual period with minima in November, July (and 

 March) and maxima in January, April (and August). Taking the means for 

 the seasons, we get 



Winter Spring Summer Autumn 



-$ 8-62 7-76 6-82 6'54 



n a 



Maximum in winter, minimum in autumn. 



1 Christiania has 7'1 hours, the west coast of Norway more than 13 hours. 



