Deriving the Vertical Variations in the Diffuse Attenuation Coefficient of Photosynthetically Available Radiation in the North Pacific Ocean from Remote Sensing

Abstract

Diffuse attenuation coefficient of photosynthetically available radiation (PAR), KPAR, is a key product of ocean color remote sensing. Current ocean color algorithms generally detect only the average KPAR within one optical depth, KPARRS. Due to the marked vertical variations of KPAR, knowledge of KPARRS is insufficient to accurately evaluate the submarine light field. By using field in situ observations, a two-step approach, based on the development of an ocean color algorithm for KPARRS and the relationships between KPARRS and the average KPAR from the surface down to depth Z (K¯PARZ), was developed to remotely estimate the vertical variations in K¯PARZ in the North Pacific from the MODerate-resolution Imaging Spectrometer (MODIS) imagery. The root mean square difference of log(K¯PARZ) in depths within the euphotic zone was around ±0.059 (in unit of m−1 for K¯PARZ), which corresponded to a deviation of ±15% for the estimated K¯PARZ and the penetration depths of PAR. Our study may provide a promising approach to detect the vertical variations of K¯PARZ and underwater PAR distributions in the North Pacific Ocean.