Remote sensing estimation of carbon fractions in the Chinese Yellow River estuary

Reliable and consistent carbon fraction estimates are crucial in studying the role of coasts in the global carbon cycle. Remote sensing offers the potential to estimate carbon fractions with its advantages of large spatial coverage and real-time surveys. Colored dissolved organic matter (CDOM) absorption was generally used as a proxy to estimate dissolved organic carbon (DOC). However, the CDOM-DOC relationship varies by region and remains inconstant. Thus, the correlation between the reflectivity of visible band and DOC concentration was directly adopted in DOC estimation and performed well in former studies. Atomic groups of the various components of carbon fractions produce electronic transition by absorbing photons, and this process occurs both in the visible bands and in the near-infrared bands. Thus, the wide range of absorption band provides an approach to estimate carbon fractions using the correlation between the reflectivity of the whole visible/near-infrared bands of optical satellite sensors and carbon fractions. A new ratio band combination was developed and performed well in carbon fraction concentration retrievals, and the yielded estimation accuracies (R-2>0.77, RPD >2.02) were sufficient to map the spatial distributions of carbon fractions with the moderate resolution imaging spectroradiometer image.