近岸二类水体生物光学模型参数优化

为了优化生物光学模型中的悬浮物后向散射模型系数（b^_bx）和双向反射因子（f/Q），基于珠江口、韩江河口、徐闻珊瑚礁保护区实测数据（遥感反射率、叶绿素a质量浓度、悬浮物质量浓度、CDOM吸收系数），采用模拟退火算法同时优化了b_bx以及f/Q（N＝43），并开发了生物光学正演模型（N＝22）。文章优化的f/Q为0.104 9，悬浮物在参考波长531 nm处后向散射系数b_bx为0.268×[TSS]^0.295。通过输入实测的水质数据模拟出531 nm处的遥感反射率，并外推到其他波段（412、443、490、551、667 nm）。模拟得到的531 nm处遥感反射率与实测值的均方根误差RMSE＝0.000 8，N＝22，除了模拟的667 nm处遥感反射率误差较大外（RMSE＝0.003 6，N＝22），其他波段都具有较好的精度（RMSE＜0.002 3）。结果表明，该研究区与其他研究区（如黄、东海）的bbx和f/Q不一致，这2个参数需要根据研究区的数据进行优化。验证结果说明迭代优化的b_bx以及f/Q能够适用于广东近岸河口生物光学参数模拟。

Optimization of Bio-Optical Algorithm Parameters in Coastal CASE-II Waters

The optimization of bio-optical algorithm parameters in remote sensing of CASE-II water is a necessary step before they can be applied, because these parameters vary with the changes of study area. Biochemical parameters (Chlorophyll a, Total suspended solids, CDOM absorption coefficient) and above-water surface reflectance collected in the Pearl River Estuary, Hanjiang Estuary and Xuwen Coral Reef Zone were used to iterate the back scattering coefficient model of total suspended solids (b_bx) and the bidirectional reflectance (f/Q) by simulated annealing algorithm (N=43). The calibration results indicated that the f/Q was 0.104 9, and the b_bx at the wave length of 531 nm was 0.268×[TSS]^0.295. Then, the forward model was developed to test the optimized results, i.e. the remote sensing reflectance was simulated by inputting water quality parameters (N=22). The validation results showed that reflectance obtained from the optimized algorithm agreed well with field observations(RMSE=0.000 8, N=22). The remote sensing reflectance at the wavelength of 667 nm extrapolated from the Bio-optical Algorithm had poor accuracy (RMSE=0.0036, N=22) compared with the field data , while all the other band (412, 443, 490, 551 nm)had good precision (RMSE<0.002 3, N=22). It showed that bbx and f/Q varied with different study areas, and they should be optimized according to the measured data. The b_bx and f/Q values obtained from the optimized algorithm can be applied to bio-optical algorithm.