Improving methods for assessing reflectance due to whitecaps and foam from ocean color imagery

The standard ocean color atmospheric correction algorithms have a simplistic method for treating whitecaps and foam that relies upon wind speed. However, large variability exists in the relationship between wind speed and whitecap coverage, as well as the amount of reflectance associated with whitecap and foam features. Here, field measurements of the Lambertian Equivalent Reflectance (LER) of whitecaps and foam made from the visible into the short wave infrared (350-2500 nm) are presented. Distinct spectral features related to the liquid phase of water absorption can be observed and such unique features also provide the potential to differentiate whitecaps from the reflectance of other “white” features common to imagery such as clouds and sea ice. Improved methods are suggested for assessing whitecap features based on the enhanced spectral resolution in the next generation of ocean color satellites. In addition to removing the reflectance contribution of whitecaps and bubbles in atmospheric correction routines, remote assessments of whitecap coverage could be an important climate-relevant science parameter for those studying air-sea gas exchange, generation of sea spray aerosols and potentially applicable for estimating mixed layer depth for primary productivity models.