Consistency evaluation of landsat-7 and landsat-8 for improved monitoring of colored dissolved organic matter in complex water

A series of Landsat satellites has been widely used to monitor water quality in coastal and inland complex water, but a solo Landsat satellite may not provide enough information because of its long revisit time (16-day) and frequent cloud cover, and hence sometimes it is necessary to fuse or combine the images from two or more satellites, for example, Landsat-7 and Landsat-8. However, the consistency of the two satellites has not been fully evaluated when they are used to estimate the colored dissolved organic matter (CDOM), an important water quality indicator. In this study, we used 210 Landsat-7 images and 185 neighboring Landsat-8 images from April 8, 2013 to December 26, 2018 in Sacramento River and Northern San Francisco Bay, USA, and extracted 225,265 paired samples to make the evaluation. A new Landsat-7 CDOM remote sensing model was established using these samples. The results show that the two satellites have good consistency for estimating low-level CDOM (R-2 = 0.79, RMSE = 0.05 m(-1), and MRE = 11.8%). This study shows that by combining Landsat-7 and Landsat-8 data, the available cloud-free observation frequency can be doubled compared with the frequency of using solo Landsat-8, and hence provide more detailed information for monitoring quality of complex water.