In the light of these considerations, the percent cumulative frequency 

 (H2 vs H) is the most convenient form for the preparation of the frequencv 

 distribution of wave action. For the plotting of H2 vs H, probability paper 

 (5) has shown itself to be advantageous „ The normal distribution, in accord- 

 ance with the Gaussian Probability Law, appears as a straight line (frequency 

 distribution) on this paper „ Since the investigated distribution of wave 

 heights and periods on the probability paper likewise showed a greater range 

 over rectilinear coordinates, it was natural that this method of preparation 

 be referred to for the estimation of wave action „ The rfiproduction of a fre- 

 quency distribution on probability paper (figure 2) replaces, in part, the 

 otherwise customary mean values and deviations for the estimation of a frequency 

 distribution (-4). 



From the stated mean values, according to Czuber (/+), the median value 

 C for a given distribution can be read immediately from the frequency curve 

 (50$ vs H) on probability paper „ 



The calculation of a deviation is not necessary, since the curve on 

 the probability paper permits immediately the reading of the deviation which 

 appears as a percentage of the total occurrences „ Thus, for example, the 

 deviation range of 50$ of the distribution (known as quartile deviation) on 

 either side of the median values is included between 25$ N and 75$ No A 

 further, not to be underrated, advantage of this method is its relationship 

 to the probability of the occurrence of given wave sizes „ Tne median value 

 C indicates the value which will be exceeded (or not exceeded) with the proba- 

 bility of 0.5. Waves with measurements which fall within the specified limit- 

 ing value of those of the range of deviation, occur with the probability 0.5 

 since the deviation embraces 50$ vs H of all the measured waves . With the 

 statement of this value, it still will not be possible to obtain the expression 

 with what probability an aircraft taking off or landing will encounter a 

 definite wave heighto The probability of the single exceedance of a given 

 wave height in a take-off or landing, depends not only upon the wave action, 

 but also upon the number of waves which would be met in the take-off or land- 

 ing. Closer investigation of this still should be conducted. 



For the evaluation of wave action, suitable key values of the median 

 value C and the deviation are prepared for 50$ vs H of all investigated waves. 

 These key values as the example showed will indicate the wave length and the 

 steepness H/L from the wave height, H]_ and the period, T, and thus the wave 

 action can be determined numerically. 



How completely the proposed key values of measured wave action by means 

 of the median value and deviation can generally be employed is not to be 

 overlooked. The use of these values is not necessarily unlimited since the 

 frequency distribution as such, if it originates on the basis of uniform 

 values and comes in uniform form for the "preparation", clearly determin* 1 ' 

 the measured wave action. From this method, the corresponding quantities can 

 be taken; for example, it showed with all values that the specified heights 

 which would be exceeded by 10 or 20 waves in the hour fell approximately in 

 1$ vs H of the total frequency (figure 2). The somewhat troublesome deter- 

 mination of the frequency distribution of H/L can be eliminated if one is 

 only concerned with the determination of the median value for H/L, which, 



34 



