Practical Methods for Observing and Forecasting Ocean Waves by Means of Wave Spectra and Statistics. (Reprinted 1971)

Abstract

Wave research has made great strides during the past 10 years. The spectrum of ocean waves was first studied in Britain by G. E. R. Deacon, N. F. Barber, and F. Ursell. The study of wave spectra was continued in the United States by A. A. Klebba, G. Birkhoff, and many others. The irregularities and the statistical properties of waves were also being studied, and an attempt was being made to fit the various pieces together in a consistent and logical pattern. During 1949, the members of the staff of the Department of Meteorology and Oceanography at New York University began the study of ocean waves under a contract with the Beach Erosion Board. The problem was to determine the effects of waves on the beaches of the east coast of the Uneitd States. Wave refraction theory and wave spectrum theory were studied in connection with these co.tracs in order to find newer and better techniques for describing the waves. As this research progressed, the Office of Naval Research became interested and supported work on wave generation, wave spectra, and wave propagation in deep water. The results of the research conducted for the Beach Erosion Board anu tne 'mce of Naval Research provide the basis for this -manual on ocean waves. The work done in 1949 and 1950 for the Beach Erosion Board was particularly important in the preparation of this manual since it helped to formulate the problems to be solved and provided information on tile questions which really needed answers in the problem of wave forecasting. The Bibliography lists the papers which were studied and used in the preparation of this manual. In addition to the papers referenced explicitly in the text, reading the papers by Barber and Ursell (1948), Cox and Munk (1954), James (1954), Longuet-Higgins (1952), Neumann (especially BEB Tech. Memo. No. 43, 1954), Pierson and Marks (1954), St. Denis and Pierson (1954), Rice (1945), and Watters (1953) will provide the person interested in the theory with an understanding of the foundation on which this manual is based. The derivation of the average "wave length", L, is not given in any of the references listed above; however, it has appeared in the transactions of the American Geophysical Union kPicrson, 1954). This manual is the result of mary years of work by many people. It is as up-to-date and as correct as it is possible to make it. However, as in any science, newer and more up-to-date results are continuously being obtained. Also some baffling theoretical problems, especially those connected with the effects of viscosity, still need to be solved. Those who use this manual should therefore not hesitate to apply new knowledge gained, by experience and by trial and error to the procedures given. Many people gave suggestions, knowledge, and skill in the preparation of this manual. Help was asked of the Coast Guard, the Hydrographic Office, the Navy, the Beach Erosion Board, and the Weather Bureau, and it was freely given. We-would like to thank all concerned for their help and cooperation. Lt. Comdr. Donald R. Jones, USN served as the liaison officer between New York University and Project AROWA. The many conferences which w, have had with him have helped very much in the preparation of this manual. The Atlantic Weather Patrol under the supervision, at the New York Port, of Mr. Clurles Nelson took wave observations according to the methods described in Chapter IV and sent many sheets of wave data to us. These data were analyzed and studied in order to make it possible to write Chapter IV. The suggestions which Mr. Nelson, Mr. Quintman, and Mr, Kirkman gave us as to the difficulties encountered in making the observations helped to clarify the presentation given in Chapter IV. During the preparation of this manual, the Search aiid Rescue Section of the U. S. Coast Guard based in New York City was extremely helpful with comments and advice. We would like to thank Chief Aerographer's Mates Black, Boerner, and Bridenstine, all of *whose suggestions were used in the preparation of this manual. In the beginning days of the preparation of this manual, a visit was made to Elizabeth City, N. C., and Capt. D. B. MacDiarmid, USCG talked with us about the problem of landing seaplanes on the open ocean. He showed motion pictures of the tests which were made and described his experiences in this connection. He also gave us the two wave photographs which were used in Chapter T. His help and suggestions are greatly appreciated. The staf of the Division of Oceanography at thf Hydrographic Office has read this manual and tested the methods presented. Their comments on the original manuscript were used in revising it for final form. The suggestion that the synoptic wave chart procedure, which has been developed and studied at the Hydrographic Office, be incorporated as part of the practical procedures was made by the authors of this manual. The Hydrographic Office willingly gave permission for this method to be described herein. It shows great promise as a method of preparing wave forecaGts in a simple and straightforward manner. The Beach Erosion Board, in connection with other contracts at New York University, has kept us supplied with wave data. These data were used in checking the forecasting methods and in the preparation of Chapter I and Chapter VIII. Dr. M. S. Longuet-Higgins visited New York University in 1952 and discussed wave theory with us. Dr. Longuet-Higgins read the original manual and made suggestions as to clarifications in the text. These were used in the preparation of this revised version. Correspondence with Robin A. Wooding and N. F. Barber of New Zealand provided additional checks of theory and observation. Their interesting letters were greatly appreciated. Conversations with Mr. S. 0. Rice and Prof. J. W. Tukey of Bell Telephone Laboratories were also most helpful. The original forecasting manual was prepared in 1953 under a contract sponsored by Bureau of Aeronautics, Project AROWA (contract No. N189s-86743). Major changes made in Chapter I, Chapter JI, Chapter III, Chapter VII, and Chapter VIII were carried out in 1954 under a contract sponsored by the Office of Naval Research (Nonr-285 (03).