Two-Dinmensional Wave Spectrum 

 REFERENCES 



A. Scott, J. R., A Darbyshire Type Spectrum Suitable as a Standard for Model 

 Tests and as a Basis for Long Term Ship Prediction. 



B. Hogben, N., Lumb, F. E. and Cartwright, D. E., The Presentation of Wave 

 Data from Voluntary Observing Ships. Ship Report 49, July 1964. 



REPLY TO THE DISCUSSION 



W. J. Pierson, Jr. 



New York University 

 New York, New York 



Mr. Silverleaf states that the formula I gave in my paper may not be the 

 best and proposes an alternate on the basis of work by Scott. It would be inter- 

 esting to see if the subsets obtained by Scott would pass the test applied by Mr. 

 Moskowitz to his data. On the other hand, it may be the best. For example, the 

 ITTC has adopted a form quite similar to the form we have obtained at N.Y.U. 

 It must be emphasized that the formula represents only fully developed wind 

 seas as a function of the wind velocity. The documentation for our results is 

 substantial and it forms a convincing total picture. Recent work of Kraus (1965) 

 provides added support. 



Partially developed seas, dead seas, and swell all have spectra that differ 

 from the form I gave. Whether meaningful averages of such spectra can be ob- 

 tained is questionable, and I have expressed certain doubts in this connection in 

 correspondence with Mr. Hogben. 



I believe that all of the examples given in my paper come within the domain 

 of the naval architect. It is his responsibility to see that the ships he builds are 

 so thoroughly understood that their performance in any given situation can be 

 correctly described. Other inputs are needed from meteorology and oceanog- 

 raphy, but in principle the problems posed differ only in degree and not in kind. 

 Although not stated explicitly in my paper, each ship captain who receives such 

 a warning should be thoroughly acquainted with the expected behavior of his ves- 

 sel for the predicted extreme condition. 



Our work on waves would never have reached its present stage without the 

 foresight of the National Institute of Oceanography in Great Britain. The routine 

 collection of wave data by means of British weather ships and the Tucker ship- 

 borne wave recorder has been the cornerstone of our work. 



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