Declining particulate organic carbon flux to estuary yet rising oceanic flux over the past 20 years: A case study of the Pearl River Estuary.

A substantial amount of particulate organic carbon (POC) is transported by the Pearl River to the Pearl River Estuary (PRE) and the northern South China Sea (NSCS) via its dense river network and eight outlets. The basin's high-intensity human activities and the estuary's complex hydrodynamic environment result in spatiotemporal variability in the POC flux entering both the estuary and the sea. Utilizing 30-meter spatial resolution Landsat-7/8 satellite data with the Finite Volume Community Ocean Model (FVCOM), this study estimated the monthly POC fluxes entering the PRE and the NSCS from 2001 to 2020.

High-frequency monitoring of Secchi-disk depth in Taihu Lake using Himawari-8/AHI data.

Diurnal monitoring of the Secchi-disk depth (SDD) of eutrophic lakes is the basic requirement to ensure domestic, industrial, and agricultural water use in surrounding cities. The retrieval of SDD in high frequency and longer observation period is the basic monitoring requirement to guarantee water environmental quality. Taking Lake Taihu as an example, the diurnal high-frequency observation (10 mins) data of the geostationary meteorological satellite sensor AHI/Himawari-8 were examined in this study.

Atmospheric correction algorithm based on the interpolation of ultraviolet and shortwave infrared bands.

Traditional atmospheric correction algorithms of ocean color remote sensing are mostly based on the extrapolation of aerosol scattering radiance from a reference band (near infrared, shortwave infrared, or ultraviolet bands), which inevitably leads to the problem of extrapolation error amplification with the increase of extrapolation spectral distance. In this study, we propose a practical interpolation-based algorithm (named the UV-SWIR-AC algorithm) using three reference bands (one ultraviolet and two shortwave infrared bands) for turbid waters. According to 6SV radiative transfer simulations with 15 customized aerosol types, we establish a fitting function framework for the aerosol scattering radiance in the wavelength range of 322-1643 nm.

Characteristics of water leaving reflectance at ultraviolet wavelengths: radiative transfer simulations.

Ultraviolet (UV) bands have attracted considerable attention in regard to satellite ocean color remote sensing due to their potential application in atmospheric correction, oil spill detection, and water organic matter retrieval. However, the characteristics of the water spectrum in the UV bands are still poorly understood. In this study, by extending the bio-optical model from traditional visible light wavelengths to UV light wavelengths, the water spectrum in UV bands under different water types was simulated by using the HydroLight water radiative transfer model, and influences of ocean color components on the water spectrum in UV bands were investigated.