[Surface spectral measurement and characteristics analysis of turbid water in Hangzhou Bay].
Suspended sediment is one of the major optically active substances in coastal waters. The knowledge of its spectral characteristics is the basis for developing precise remote sensing inversion algorithms. Two separate continuous monitoring stations were set near the northern and southern coast of Hangzhou Bay separately, which is typically turbid area in China coastal waters. The above-water measurement method and the American ASD portable spectroscope were adopted to measure the water surface reflectance spectrum. The sediment concentrations of surface water were synchronously acquired when measuring water-leaving radiance. Results show that the sediments concentration is comparatively high and changes dramatically according to tide cycle. The reflectance spectrum at different wavelengths rises corresponding to the increase in sediments concentrations with different extent. When using first derivative method to analysis the spectral characteristic, it can be found that the first reflectance peaks of reflectance spectra appear to shift to long wavelength. There are different correlations between sediment concentrations and each MODIS channel reflectance, which are above 0.5 in 650 nm or longer wavelengths channels and below 0.5 in 400-550 nm channels. The fitting result of regression analysis is preferable with MODIS channel 2 (841-876 nm) and in situ sediment concentrations using least square method, with R2 of exponential above 0.8, which indicated that the MODIS channel 2 can be used for surface water suspended sediments remote sensing inversion, particularly in turbid waters such as bays and estuaries.
Wang
Fan
F
College of Environmental and Resources Science, Zhejiang University, Hangzhou 310029, China. wangfan@zju.edu.cn
Zhou
Bin
B
Xu
Jian-Ming
JM
Ling
Zai-Ying
ZY
Zhuo
Gen-Di
GD
D002681:China; D019015:Geologic Sediments / Q000737:chemistry; D009391:Nephelometry and Turbidimetry; D012623:Seawater / Q000737:chemistry*; D013499:Surface Properties