Evaluation of Swedish lake water quality modelling from remote sensing

摘要

A simple bio-optical model has been developed and used together with historical water quality measurements from Lake Malaren, Sweden, to construct an algorithm for retrieval of chlorophyll concentrations from remote sensing data. The algorithm has previously been applied to CASI data from Lake Malaren and the result was promising, but the model needed further validation on data from other lakes in order to investigate its generality. CASI data was also collected over the nearby Lake Erken and in this paper the same algorithm was applied to that data set and evaluated using ground truth measurements. The estimated chlorophyll concentrations were in average twice as high as the ground truth measurements. The CASI spectra were therefore compared to the reflectance spectra measured at lake level at all sampling stations in Erken during the campaign, and the correspondence was good. The overestimation of chlorophyll by the model derived algorithm can be explained by the fact that ground truth samples were taken below the surface, while the CASI measurements reflect the state on the surface, where accumulations were evident in the whole lake.