Retrieval Algorithm of Chlorophyll-a Concentration in Turbid Waters from Satellite HY-1C Coastal Zone Imager Data

Chen, X.-Y.; Zhang, J.; Tong, C.; Liu, R.-J.; Mu, B., and Ding, J., 2019. Retrieval algorithm of chlorophyll-a concentration in turbid waters from satellite HY-1C coastal zone imager data. In: Jung, H.-S.; Lee, S.; Ryu, J.-H., and Cui, T. (eds.), Advances in Remote Sensing and Geoscience Information Systems of Coastal Environments. Journal of Coastal Research, Special Issue No. 90, pp. 146-155. Coconut Creek (Florida), ISSN 0749-0208.The satellite HY-1C was successfully launched in September 2018 with the Coastal Zone Imager (CZI) onboard, which can provide optical images of 50-m resolution at four broad bands (blue, green, red and near-infrared). In this study, 305 sets of in-situ measurements collected between 2005 and 2015 in the Bohai, Yellow and East China seas were used to assess the performance of HY-1C in retrieving chlorophyll-a concentration in the coastal waters. The results showed that two algorithms based on blue-green band ratios (OC3 and OC3L) performed well. The median of the ratio of retrieved to in-situ values was about 1.1, and the median absolute percentage difference was about 40 %. After applying the two algorithms to HY-1C CZI data of Jiaozhou Bay (Qingdao, China), the spatial distribution of retrieved Chl-a data was found to be in good agreement with results based on data from another satellite (Landsat-8 OLI) with a median absolute percentage difference less than 15 %. The results showed that the broadband channels of the HY-1C CZI can retrieve Chl-a concentration in turbid waters, which indicates potential for its application in coastal water quality and eutrophication monitoring.