Wave Shape
Wind had a substantial effect on shoaling wave shape, which appears to be stronger in shallower water.
![Picture](/uploads/2/3/9/2/23922486/2626852.png?426)
As common scientifically-accepted ideas of the behavior of wind waves, a rapid increase of wind force tends to reduce the height of the waves for the following reasons:
(i) the wave height in a wind sea is a strictly increasing function of wind speed;
(ii) the rate of wave growth increases with wind stress and with sea-surface roughness; and
(iii) wave breaking, which can be expected to increase during severe wind conditions, tends to increase the hydrodynamic roughness of the water surface.
A rapid increase of wind force tends to reduce the height of the waves, in other words 'violent winds blow the waves flat'. A vertically- sheared current reduces the maximum steepness a water wave can have before breaking, since the shear in the surface current will respond more rapidly than the wave height to a sudden increase in wind speed, an increase in the intensity of wave breaking should then occur, leading to a temporary decrease in wave height until the sheared current distributes itself through the water column.
(i) the wave height in a wind sea is a strictly increasing function of wind speed;
(ii) the rate of wave growth increases with wind stress and with sea-surface roughness; and
(iii) wave breaking, which can be expected to increase during severe wind conditions, tends to increase the hydrodynamic roughness of the water surface.
A rapid increase of wind force tends to reduce the height of the waves, in other words 'violent winds blow the waves flat'. A vertically- sheared current reduces the maximum steepness a water wave can have before breaking, since the shear in the surface current will respond more rapidly than the wave height to a sudden increase in wind speed, an increase in the intensity of wave breaking should then occur, leading to a temporary decrease in wave height until the sheared current distributes itself through the water column.
![图片](/uploads/2/3/9/2/23922486/8601654.jpg?416)
There is a research by Australian Maritime Safety Authority (AU). When wind reaches 2.5 km/hr, gravity takes over from surface tension as the dominant force on wave form. The crests become more pointed, the trough rounded. The wind reinforces the wave shaped by pressing down on the windward side and eddying over the crest to reduce pressure on the leeward side. As wind increases further to around 13 km/hr, the crests of the waves steepen until they become unstable and break, producing whitecaps.
Shoaling
Wave shoaling reduces the wave age, suggesting increased coupling between wind and the waves, and increases the wave nonlinearity. Wind increased the shoaling wave height (by 10%) by putting energy into discrete multiples of the peak frequency. Wind also affected the shoaling wave shape. At the deeper location, only the asymmetry was affected; at the shallower location near the break point, both the skewness and asymmetry were changed.