The mean length of runs of wave heights and the mean number of waves between the exceedance of a certain level by a group of waves and the next exceedance of the same level by the succeeding group of waves have been investigated for data from the March 1968 North Atlantic storm. These quantities are compared with corresponding results obtained from the numerical simulation of waves in a computer for both wide and narrow band spectra.

Theoretical and experimental results for gravity wave interaction with a hemispherical object resting on the ocean floor are presented. The hydrodynamic problem of wave interaction with large submerged objects such as submerged oil storage tanks is approached by means of diffraction theory. Numerical results for horizontal and vertical force coefficients and corresponding phase shift angles are presented. These results are compared with results, obtained from a simpler approach to show'where the effects due to the proximity of the free surface and the relative size of the object become significant. Also, corresponding experimental results are presented for comparison with the theory. CAT2RTSONSF!RTUARAMA RA(I ANTI SNTl)ER

The Ocean Weather Ship Weather Adviser, underway from the United Kingdom to assume her station at position J (near 53°N, 18°W) on the North Atlantic, encountered very heavy seas over a 5‐day period from March 15, 0900 GMT, to March 19, 2100 GMT, 1968. The ship measured the sea state during this stormy period with a shipborne wave recorder at 3‐hour intervals. From these wave records‐the wave energy spectra are computed and are represented in tabular form. Also, selected spectra from these tables are graphically represented. Two peak energy values calculated from wave records taken on March 17, 0300 and 0900 GMT, were found to occur between the wave periods of 15 and 16.5 sec. Wave heights measured from the above two wave records reached maximums between 60 and 65 feet.

No abstract

Marine Research and Development, Chicago Bridge and Iron Company, Plainfield, Illinois 60544A recent 1968 North Atlantic storm is investigated. The statistics of the wave parameters, namely, wave height and period, are studied. The wave data are analyzed in the time domain to obtain wave parameters by Tucker's method. Spectrum analysis is undertaken to obtain the same statistical quantities. The parameters calculated by the two methods are compared with each other. Overall, the two methods are found to agree within acceptable limits. The statistical distribution, e.g., Rayleigh, of the individual wave heights and wave periods in a record is studied with reference to the spectral width parameter. The theoretical correlation of the distribution of height is found to be mostly poor, whereas the Rayleigh distribution of the square of the period yielded better correlation coefficients. It is argued that the significant wave height varies either with the square of the mean wave period or with both the period and its square in a linear fashion. The joint distribution of these two quantities for this storm is discussed.