157 / 2023-10-19 15:18:56

Sea Surface Temperature Retrieval Method of China Ocean Color and Temperature Scanner (COCTS) on the HY-1C and HY-1D satellites

Sea Surface Temperature, Retrieval Method, COCTS, HY-1C, HY-1D

The Chinese Haiyang-1C (HY-1C) and Haiyang-1D (HY-1D) satellites were launched in September 2018 and June 2020, respectively. This satellites are both equipped with the COCTS, a moderate-resolution imaging scanner with a nadir spatial resolution of 1.1 km and a viewing swath width of more than 2900 km. The satellite measures signals in 8 visible and near-infrared (VNIR) bands and 2 thermal infrared (TIR) bands (10.3~11.3μm，11.5~12.5μm). By using the non-linear algorithm for SST (NLSST) of split window, we retrieve SST from the two thermal infrared spectrum channels of 11 and 12 µm of COCTS. The Multiple Channel Sea Surface Temperature (MCSST) is used to be as the first guess of NLSST equation. The coefficients of both NLSST and MCSST are regression to ocean buoys and ship measurements. The retrieval SSTs from Jan. 1, 2019 to Mar. 31, 2020 were evaluated by the in situ measurements from iQuam with root mean square errors (RMSEs) of 0.84 °C for daytime and 0.97 °C for nighttime and robust standard deviations (RSDs) of 0.73 °C for daytime and 0.72 °C for nighttime, respectively. RMSEs of 0.65 °C and 0.71 °C and RSDs of 0.51 °C and 0.47 °C were obtained for the daytime and nighttime SSTs of the COCTS/HY-1D recorded from April 26 to August 31, 2021, using a spatiotemporal matching window of 4 hours and 2.5 km. Daily gridded retrieval SSTs from COCTS on both HY-1C and HY-1D were compared with SSTs from the moderate-resolution imaging spectroradiometer (MODIS) on Terra satellite and the visible infrared imaging radiometer (VIIRS) on the Suomi National Polar-orbiting Partnership (S-NPP) satellite. Both daytime and nighttime SSTs from COCTS are consistent with those from MODIS and VIIRS.