Variations of ocean colour parameters with nonuniform vertical profiles of chlorophyll concentration

Abstract

Abstract Based on radiative transfer simulations, the effects of nonuniform chlorophyll profiles in case 1 waters on the penetration depth, the above‐surface spectral remote‐sensing reflectance, and the optically weighted chlorophyll concentration are investigated. The simulations for nonuniform chlorophyll profiles are compared with those for homogeneous ocean whose chlorophyll concentrations are identical to the surface chlorophyll concentrations in the inhomogeneous ocean. Due to influence of the nonuniformity of chlorophyll profile, the maximum relative error for the penetration depth at 445 nm is more than 60%, the spectral remote‐sensing reflectance is about 40% and the optically weighted chlorophyll concentration is about 40% within the range of our simulations. However, the simulation shows that there is always a spectral band where the value of above‐surface remote‐sensing reflectance is not influenced by the nonuniformity. Depending on this band, a new model for retrieving sea surface chlorophyll concentration is designed by adding a compensation term into the variable in SeaWiFS OC2V4 algorithm. By using an iterative method with this new model, sea surface chlorophyll concentration can be well retrieved even in an area where the vertical chlorophyll distribution is unknown. Acknowledgements This study was supported by the National High Technology Development Project of China under Grant 863‐2006AA09Z140.