Detection Of Hourly Variability Of Bio-optical Properties In The Yellow River Estuary By Geostationary Satellite Ocean Color Images

The turbid water of the Yellow River Estuary was taken as the study area in this paper. Theresearch on hourly variability of water component concentrations and optical properties and theirdriving mechanism was carried out using the data collected during wet （water and sedimentregulation period） and dry season. Then we used the radiative transfer model to study theinfluence of atmospheric optical properties as well as observation geometry on the world’s firstgeostationary satellite ocean color Images （GOCI） data. Based on these the hourly variability ofthe water component concentration and optical properties were monitored and the impact of windsand tides was studied.The results of in situ continuous observation data analysis indicate that the hourly variabilityof the optical properties of Yellow River Estuary have different degrees which contribute to thevariation of the river discharge, winds and tides.（1） The hourly variability of total absorptioncoefficient focus at blue and green bands of which the absorption of particulate matter is the mainresource.（2） The particulate matter absorption spectra show natural exponential trend. The reasonis that the total absorption of water dominated by the non-algae particulate matter （about80%atmost bands）.（3） The hourly variability of the spectra slope of absorption coefficient of thenon-algae particulate matter was in the range of2.7-3.7%（0.0011-0.0016）. ad（440） changedbetween56.3^-108.5%(0.9-20.6m^-1). Absorption of non-algal particulate matter and suspendedparticulate matter concentration has a significant positive correlation （>0.75）.（4） The spectraslope of the absorption coefficient of yellow substance changed about11.8-23.1%with the hourlyrange between0.008-0.010nm. ag（440） changed about38.8-67.9%with the hourly variability of0.183-0.633m^-1. In the river discharge waters, ag（440） negatively correlated with salinity.（5） Thediffuse attenuation coefficient changed about10.6-39.5%with the hourly variability of1.66-4.39m^-1. The diffuse attenuation coefficient and the absorption of particulate matter, as wellas the backscattering coefficient, has a higher correlation. However it was poor for yellowsubstance.（6） The hourly variability of remote sensing reflectance is the most complex in theoptical properties of the water body. The main driving factor is the suspended particulate matterconcentration.The research on the influencing factors of geostationary orbit satellite ocean color data foundthat:（1） in the sediment suspended matter dominant water, the water signal to the satellite is lowerthan12%at412nm band, higher than50%at660nm and680nm bands （up to80%）, and between15-80%at at745nm and865nm bands. The GOCI data can detect the most hourly variability of above-water spectral information.（2） The satellite signal changes linearly with the hourlyvariability of aerosol optical thickness. At the clean atmospheric conditions （AOT≤0.1）, theerrors between the retrieved Rrs（555）, Rrs（660） and Rrs（680） from Rayleigh scattering correctionand their measured values were14%,14%and15%.（3） When the solar zenith angle was less than50°, the satellite signal is not sensitive to the changes of solar zenith angle （the relative differenceis less than5%at most bands besides745nm and865nm）. When the zenith angle is greater than50°, the sensitivity was significantly increased. GOCI satellite solar zenith angle （solar zenithangle range:13.7⁷8.4°） is small in summer and large in winter. So its influence on the opticalproperties is of importance and can not be ignored.（4） When the satellite zenith angle less than40°, the satellite signal is not sensitive to the changes of satellite zenith angle. However, itincreased significantly when the satellite zenith angle was greater than40°. GOCI satellite zenithangle does not exceed5°, so its influence on hourly variability of the optical properties isrelatively small. The differences at45nm and865nm bands were less than2.1%, and less than1%at other bands.Through the study of the optical properties and hourly variability of CSPMwithin the YellowRiver Estuary based on the GOCI images, it is found that:（1） bands of660nm and680nmpresentthe most significant hourly variability of spectral property for SPM-dominant turbid water;（2） according to the regression model based on single band values and band ratios of555nm,680nm and745nm, the precision of the model achieves30%within the range of change ofconcentration of spm of4magnitudes;（3） the spatial distributions of hourly variability of Rrs（680）and CSPMcoincide with turbidity, which is higher onshore and lower offshore;（4） storm will causedramatic rise of Rrs（680）, CSPMand extent of hourly variability in shallow areas, such as LaizhouBay and Bohai Bay, while the deep sea is less affected;（5） it is also found that tide and hourlyvariability of CSPMdo not change concurrently base on the analysis of their relation. One possiblereason is the incapability of the current from weak-tide areas to raise the bottom sand and to affectCSPM。...