近红外波段二类水体悬浮物生物光学反演模型研究

Bio-Optical Model of Total Suspended Matter Based on Reflectance in the Near Infrared Wave Band for Case-Ⅱ Waters

通过野外高光谱仪对二类混浊水体进行光谱测量,分析了400～1200nm范围内的水体光谱特性。显示高浓度悬浮物含量对水体总的反射率贡献较大,在近红外波段处的808和1067nm存在较为明显的悬浮物反射峰。基于对水体固有光学特性参数在近红外波段范围内的简化条件,建立了反演悬浮物浓度的生物光学模型经验公式,并通过与线性和指数反演公式的对比,进行了模型反演精度评价。分析结果表明,基于近红外波段的生物光学模型反演精度较高,可有效地提取二类混浊水体的悬浮物浓度信息。

From August to October, 2006, reflectance spectra were measured in a turbid Case-Ⅱ waters condition with an ASD FieldSpee spectrometer for a total of 58 samples. Based on the observation of reflectance curves, spectral analysis was carried out over 400-1 200 nm. Showing the typical character of Case- Ⅱ waters, the reflectance values were generally higher than those in other similar studies. Strong backscattering of high concentration total suspended matter （TSM） contributed considerably to the total reflectance spectra in water. Two obvious TSM reflectance peaks were observed in the near infrared wave bands, i.e. 808 and 1 067 ran, especially the latter one that was never reported before. The highest correlation coefficient between reflectance and concentrations of TSM existed at 873 nm. Based on the simplification of water inherent optical parameters in the near-infrared wave band, including absorption of TSM, Chlorophyll-a （Chl-a） and chromophoric dissolved organic matter （CDOM）, and backscattering of pure water, Chl-a and CDOM, three empirical equations of the bio-optical model using reflectance at 808, 873 and 1 067 nm respectively were established to estimate the concentrations of TSM. Compared with linear and exponential mod- els, the bio-optical model showed fairly good performance with comparatively high determination coefficient （r^2 ） and low root mean squared error （RMSE）, which confirmed the applicability of the bio-optical model to retrieve concentrations of TSM effectively in turbid Case-Ⅱ waters.