Preliminary Study On Diffuse Attenuation Property In Winter Season And Its Remote-sensing Retrieval In Yangtze Estuarine And Coastal Ocean

According to the situ data in Yangtze River Estuary’s Adjacent sea area in March2012and March2013, the spectral characteristics of the diffuse attenuation coefficient (Kd), spatial distribution and dominant factors of Kd(490), as well as the relationship between Kd(490) and chlorophyll, CDOM, total suspended particulate matters and the relationship between Kd(490) and photosynthetically active radiation attenuation coefficient (Kd(PAR)) were analyzed. The results indicate that the Kd(490) in Yangtze River Estuary’s adjacent area were increased with decreasing distance from the shore, the maximum value of Kd(490) reached1.8m-1, the Kd(490) in Hangzhou Bay’s adjacent area were similar to this result, the maximum value of Kd(490) appeared near the Zhoushan island, which reached2.8m-1. The dominant factor of diffuse attenuation coefficient was total suspended matter, the correlation was more than0.86, the CDOM and Chla have a little influence on the Kd(490), the correlation was less than0.25. the relationship between Kd(490) and Kd(PAR) was Kd(PAR)=0.495exp (0.8602Kd(490))-0.2217, comparing situ data with the calculated Kd (PAR) shows that the root mean square error is0.102m-1, the absolute percentage difference is14.62%, the coefficient of correlation’s square is0.927. the relationship between Kd(490) and total suspended particulate matters(TSM) was Kd(490)=1.988+3.61*TSM+3.198*TSM2, comparing situ data with the calculated Kd(490) shows that the root mean square error is0.103m-1, the absolute percentage difference is25.6%, the coefficient of correlation’s square is0.895.Based on the others’ research and the dominant factor of diffuse attenuation coefficient, a new model to calculate Kd(490) was established.The new model to calculate Kd(490) which was lg[Kd(490)]=a[Rrs(590)/Rrs(510)]+btRr(670)/Rrs(510)], comparing situ data with the calculated Kd(490) shows that the root mean square error is0.098m-1, the absolute percentage difference is12.43%, the coefficient of correlate- on’s square is0.916; At the same time, the relationship between Kd(490) and Kd(λ) could be parameterized with wavelength by multiplying formuls in400nm-700nm. Comparing situ data with the calculated Kd(λ) shows that the root mean square error is0.032～0.074m-1, the absolute percentage difference is0.024～0.0985, the coefficient of correlation’s square is0.947-0.988.The PAR intensity, the normalized PAR intensity and the regression equations of quadratic function could ideally fit the relationship between the normalized PAR intensity and the euphotic depth, and on the basis of the study above, primary produc-tivity was calculated, the primary productivity was influenced mainly by the euphotic depth.