National Oceanic and
Atmospheric Administration
United States Department of Commerce


FY 2015

Bering Sea optical and biological properties from MODIS

Naik, P., M. Wang, E.J. D'Sa, and C.W. Mordy

Remote Sens. Environ., 163, 240–252, doi: 10.1016/j.rse.2015.03.020 (2015)

The Bering Sea is characterized by unique bio-optical properties, which cause unsatisfactory performance of global ocean color algorithms for retrieval of chlorophyll-a (Chl-a). This study evaluates the normalized water-leaving radiance nLw(λ) and Chl-a in the eastern Bering Sea that are derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the satellite Aqua by comparing them to in situ data. MODIS-Aqua ocean color products were derived using the NOAA Multi-Sensor Level-1 to Level-2 (MSL12) ocean color data processing system. The MODIS-derived nLw(λ) showed good agreement with in situ-measured nLw(λ). The mean ratios between them for wavelengths 412, 443, 488, and 551 nm ranged from 1.097 to 1.280, with reasonably accurate blue-green radiance ratios in nLw(λ) that were used as input for deriving Chl-a. However, compared to in situ data, existing global and regional Chl-a algorithms either overestimate or underestimate Chl-a in the eastern Bering Sea. Therefore, we propose a new algorithm for estimating Chl-a using a blended approach that was tested and applied to MODIS-Aqua images. The histogram distributions of MODIS-Aqua-derived and in situ-measured Chl-a data show that Chl-a data derived using the new algorithm agree reasonably well to in situ measurements. Annual, seasonal, and monthly composite nLw(λ) and Chl-a images are produced for the period of 2003 to 2013 in order to interpret the long-term spatial and temporal patterns of nLw(λ) and Chl-a. The nLw(λ) spectra show strong spectral dependence on seasonal variability with distinct spatial patterns. Although strong seasonal and interannual variability has been observed in Chl-a, there is no apparent trend of either increase or decrease in phytoplankton biomass associated with variability in the physical environment for the 11 years of the study period.

Feature Publications | Outstanding Scientific Publications

Contact Sandra Bigley |