Frequency of Various 7ifave Heights and States of the Sea 



Observed maximum values of wave dimensions are a matter of 

 contingency and represent singular values v^rhich occur relatively seldom., 

 Knowledge of the frequency at which different states of the sea occur 

 is required for craft of limited seaworthiness, such as seaplanes, etc. 

 For this reason the collected observation data from lightship 

 FEffiaRNBE:.!, .BDRKUIffilFF and AMEU^.^PArnv was used to construct diagrams 

 indicating the frequency of different states of the sea and vave 

 heighto 



All results are based upon cJata collected during the stormy 

 ■wdnter 1936-37 and must consequently be considered the most unfavor- 

 able conditions which could be expected over a period of 6 months o Ob- 

 servations were fairly regular (3 times daily) but were interrupted 

 several times so that instead of 546 possible entries there were 44.3 

 entries from lightship FEWmRNBELT, 345 entries from lightship 

 BDRKmmiFF and 348 entries from lightship AMBUMBA-NKo 



TJie frequencies are expressed in percentage of actual ob- 

 servations carried out at the respective stations „ Two type of 

 frequency curves are represented, type 1 and type 2 (figures 16-21), 

 Frequencies designated type 1 represent the number of occurrences of 

 values in a fixed range „ Type 2 represents the percentage of values 

 exceeding fixed limits (accumulative frequency) o Convenient ranges of 

 wave heights vr^re chosen for the evaluation of frequencies of type lo 

 In the case of the data from lightship FEMAEMBELT these ranges com- 

 prise the vj-ave heighits to IC cm, 20 to 30 cm, 40 to 50 cmo etco 

 The frequencies are plotted as the respective ordinates of the mean 

 values, i.e=, at 5s 25, 45, o«o cm. and represent the ranges 0-15, 

 15-35j 35-55 .ocm. in wave heighto In the case of data from, lightships 

 BDRKUMRIFF and A.MRMBANK the ranges were chosen somewhat larger, i = e., 

 0-25, 25-55, 55-85, o.ocmo 



Direct comparison of the plotted values for type 1 frequency 

 of wave heights at lightships in the Baltic and North Seas is not 

 practicable o The type 2 frequency curves for the three lightships 

 were used as a means of comparison. Figure 22 shows such a comparison 

 for the relative states of the soa and figure 23 for the wave heights. 

 The diagi^ams (figure 22) indicate the similarity of the frequency 

 curves for the relative states of the sea as observed at three widely 

 separated positions in the :^ltic and North Seas, Cn the other hand, 

 there is considerable variation among the curves (figure 23) represent- 

 ing the frequency of particular v;ave heights. High seas were observed 

 as frequently from the lightship FEIBtARNBELT anchored in the Baltic 

 Sea as from the other lightships in the North Sea but the waves were 

 not as high as those observed in the North Sea, The following table 

 can be constructed from the diagrams. 



