Relationship between Wind Speed and Wave Height at Ocean Station T

Empirical Wave Heights formulae are tested based on the visual wave observation data at Ocean Station T (29°N, 135°E) and also reported are the characteristics of the visual wave observation in this paper. Difficulty of the visual swell observation is much higher than the wind wave one. It is increased in the higher wind condition more than 10m/s. Visual composite wave heights tend to be constant, about 1.2m, at low wind conditions and increase to the 1.6th power of the wind speed at higher wind conditions more than 10m/s. There is estimated 3-hour wind leading time lag between winds and waves' development and decay. The empirical wave heights formula, using the wind speed 3 hours before, has the best result to the visual observation data. Generally Composite wave heights have higher wave heights in comparison with Scott's and Pierson-Moskowitz's formulae in high wind conditions. From the analysis of the visual wave observation data, it is proposed that it be better to observe one wave height and one wave period rather than to do wind wave and swell separately in the high wind condition when it becomes difficult to distinguish them except in the low wind condition.