Inversion Study On Chlorophyll-a Concentration Of Turbid Water And Study On Sun Glint Effects

With high suspended water in the Yellow River Estuary as the research object,several inversion models of chlorophyll-a concentration were established,using measured hyperspectral reflectance data of sea water and the data of chlorophyll-a concentration,and hyperspectral satellite images and measured hyperspectral reflectance data of water were used to explore the effects of sun glint on the inverison of chlorophyll-a concentration.The main findings are as followed:Based on measured hyperspectral reflectance data of water body and the data of chlorophyll-a concentration,several inversion models of chlorophyll-a concentration were established to inverse the chlorophyll-a concentration with the suspended solids concentration from 16 to 2435mg/L in the Yellow River Estuary.The results show that,with the comparisons to the bands ratio algorithm,the three-band algorithm,the maximum chlorophyll index algorithm and the OC3 algorithm,the trough depth index algorithm has the highest accuracy in inversing chlorophyll-a concentration,the corresponding determination coefficient is 0.59,and the root mean square error(RMSE)of it is 3.22 ?g/L.As shown by the hyperspectral satellite images(HICO)and measured hyperspectral reflectance data of water,the intensity of sun glint varied to the angle of elevation,azimuth,water wave and wind;The reflectance curve shapes of water with and without sun glint were consistent,showing that sun glint didn't affect the position of surface water characteristic bands;The reflectance curve of sun glint were nearly straight lines;The intensity of sun glint coming into the sensor accounted from 2.11% to 98.93% in hyperspectral images,and in the measured data,the maximum intensity of sun glint accounted for 96.84%,while the maximum intensity of air glint accounted for 96.0%,which greatly affected the reflection of surface water.In order to analyze the effects of sun glint on models inversing chlorophyll-a concentration,different intensity of sun glint were added to the reflectance curve of water.The results show that the effects of sun glint on different modes were different.With the increase of sun glint intensity from 10% to 40%,the estimated chlorophyll-a concentration reduced by 1.17 mg/L to 4.47 mg/L;When the increased intensity of sun glint was up to 40%,the relative error of the trough depth index model was 93.20%,showing that the applicability need to be further verified.