Establishing Whitecap Coverage Observation Techniques using Video Image of Ieodo Ocean Research Station

Abstract

Result from the global environmental changes represented by global warming, environmental variables including the sea temperature and sea surface height rise, ocean acidification, etc are reported to being in progress rapidly. Many studies have been carried out to understand the cause of the environmental changes and to deal with the impact. The environmental changes are closely related to the interaction between the ocean and atmosphere, especially in the boundary layer between them. So many studies on the energy and material, such as carbon dioxides, exchanges between the ocean and atmosphere are under going. In recent years, whitecap is recognized as the important parameters for the interaction between the ocean and atmosphere. There have been many efforts to observe and qualifying variables related to whitecap. Whitecap is the direct result from the wave breaking which have large temporal and spatial variability, and it is very hard to do quantitative observation. Previous studies have suggested the analytical solution, which defined the whitecap coverage, calculated from the wind, as a primary variable. Recently, owing to development in the image processing technologies, videos and still images are being used to observe whitecap coverage. But it has been very hard to obtain the continuous, precise wave images in the ocean. In this study, wave image obtained in the Ieodo Ocean Research Station were used to reduce the error of the conversion from image to whitecap coverage, and the formula which suggested by Sugihara et al. (2007). Specifically, it presented Pixel intensity threshold determination method and criteria image sampling frequency of Whitecap.