342 



H. MOHN. METEOROLOGY. 



[2nd arc. EXP. FRAM 



DURATION OF PRECIPITATION IN ONE DAY OF 

 PRECIPITATION. 



The following Table has been computed by Koppens Method'. 

 For a certain period (e. g. a month), let 

 n be the total number of observations made 

 r - ■ — — - — of precipitation 



N - - — — - hours in the period 

 d - - the number of days with precipitation (rain or snow). 



We then have 

 r 



n 



the probability of precipitation, 



- N the total duration of precipitation in hours. 



n 



r_N 



nd 



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

 cipitation. 



The circumstance that the observations are bi-hourly or that we 



T 



have 12 observations in 24 hours, makes iV equall to 2n and ~iV to 2r. 



For the months November to June, we have complete bi-hourly obser- 

 vations for 4 years, and the value of d, or the mean number of days 



' Oesterreicliische Zeitschrift fiir Meteorologie f. 1880, p. 362 and Meteorologisctie 

 Zeitsctirift f. 1885, p. 10. 



