Publications

Qi, L; Lee, Z; Hu, CM; Wang, MH (2017). Requirement of minimal signal-to-noise ratios of ocean color sensors and uncertainties of ocean color products. JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 122(3), 2595-2611.

Abstract
Using simulations, error propagation theory, and measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS), we determined the minimal signal-to-noise ratio (SNR) required for ocean color measurements and product uncertainties at different spatial and temporal scales. First, based on typical top-of-atmosphere (TOA) radiance over the ocean, we evaluate the uncertainties in satellite-derived R-rs in the visible wavelengths (Delta R-rs(vis)) due to sensor noise in both the near-infrared (NIR) and the visible bands. While the former induces noise in R-rs(vis) through atmospheric correction, the latter has a direct impact on R-rs(vis). Such estimated uncertainties are compared with inherent Delta R-rs(vis) uncertainties from in situ measurements and from the operational atmosphere correction algorithm. The comparison leads to a conclusion that once SNR(NIR) is above 600: 1, an SNR(vis) better than 400: 1 will not make a significant reduction in product uncertainties at pixel level under typical conditions for a solar zenith angle of 458. Then, such uncertainties are found to decrease significantly in data products of oceanic waters when the 1 km pixels from individual images are binned to lower spatial resolution (e.g., 4 km) or temporal resolution (e.g., monthly). Although these findings do not suggest that passive ocean color sensors should have SNR(vis) around 400: 1, they do support the argument for more trade space in higher spatial and/or spectral resolutions once this minimal 400: 1 SNR(vis) requirement is met.

DOI:
10.1002/2016JC012558

ISSN:
2169-9275