Statistical study on existing grouping factors in ocean waves

There have been more than 10 factors to be used to characterize the intensity of wave groups since the spectral peakness parameter,Q_P,was proposed by Yoshimi Uoda in 1970.As to 11 factors more currently employed,i.e.,hereafter called existing grouping factors,mentioned in the paper,each of the authors puts emphasis on the advantage of his own.Which of the existing grouping factors is better? Nobody made an objective appraisement as yet.New a trial examination of the existing grouping factors has been made on the basis of 111 data sets obtained from three observation points in the paper.If one of the existing grouping factorn which has the maximum and minimum value among three values in succession within a shorter record satisfying that maximum value minus-minimun value is not greater than 0.005,then it is called the steady grouping factor.If this factor satisfies the other three conditions:the most frequency in an arbitrary ordinal number,the most total frequency in the whole record,and the largest occurrence probability within initial 1 280 s of the whole record,then it is called better grouping factor.So far as the cases are examined,to this factor belong the mean length of runs [of wave heights (L₁)and correlation coefficient between wave heights and periods [R_HT (0)];the two factors are connected which are hereafter called a united grouping factor.Therefore,we suggest that the united grouping factor characterized the intensity of wave groups shows better than single one adopted by forerunners.