Characters of Sea Swell Observation in the North Pacific Ocean

The wind wave and the swell in the North Pacific Ocean have been visually observed by a voluntary ship on which the composite wave height of wind wave and swell using the micro wave height meter simultaneously measured for more than three years. The composed wave heights from visual data of wind waves and swell are mostly consistent with the measured data. This consistency suggest that the wave height data by visual observation is cosiderably reliable. This report focuses on the character of swell in the North Pacific Ocean. The results of analysis are that (1) the swell always remains in the ocean regardless of wind force at that time, (2) the average height of the swell is 2.7 m and the average period is 8.8 sec, (3) the heights and periods of the swell are mostly larger than thats of the wind wave, (4) the direction of the swell comes to coincide with the main direction of wind in proportion to the wind force, (5) the more the height of swell becomes larger, the more the ship has a tendency to expose her quater side to the swell.