The rayleigh effects on the atmospheric correction of the ultraviolet imager on HY-1C and HY-1D satellites

Ultraviolet (UV) light is a key component of solar radiation, significantly impacting marine ecosystems. It is necessary to measure the ultraviolet light on the ocean which is now available from the Ultraviolet Imager (UVI) on the two ocean color satellites (HY-1C and HY-1D). The atmospheric correction (AC) procedure of the UVI data is based on the Layer Removal Scheme for Atmospheric Correction (LRSAC). Evaluation with Marine Optical Buoy in-situ data shows water-leaving reflectance (Rrs) accuracy with mean relative error (MRE) of 0.84 % (high sensitivity) and 0.13 % (low sensitivity) at Band 1 of HY-1C, and 6.79 % (high sensitivity) and −5.55 % (low sensitivity) at Band 2 of HY-1C, respectively. The mean absolute error (MAE) values are 0.0023 sr −1 (high sensitivity) and 0.0034 sr −1 (low sensitivity) at Band 1 of HY-1C, and 0.0021 sr −1 (high sensitivity) and −0.0028 sr −1 (low sensitivity) at Band 2 of HY-1C, respectively. The MRE values are 13.96 % (high sensitivity) and 20.27 % (low sensitivity) at Band 1 of HY-1D, and 8.09 % (high sensitivity) and 6.99 % (low sensitivity) at Band 2 of HY-1D, respectively. The MAE values are 0.0021 sr −1 (high sensitivity) and 0.0022 sr −1 (low sensitivity) at Band 1 of HY-1D, and 0.0023 sr −1 (high sensitivity) and 0.0022 sr −1 (low sensitivity) at Band 2 of HY-1D, respectively. The global daily and the 8-day composite images of the UVI demonstrate the spatial patterns of Rrs in the ultraviolet region, similar to the Rrs products of the Chinese Ocean Color and Temperature Scanner at blue bands. The accuracy of the Rayleigh can affect the performance of the AC mainly due to the largest part in the satellite-received radiance of the UVI. The selection of different volume scattering phases can cause about 1 % of MRE in the generation of the lookup table of Rayleigh varying with the solar and viewing angles. The ozone concentrations, sea surface winds, and atmospheric pressure of the global daily climatology have been generated and used to estimate the Rayleigh scattering at the ultraviolet bands. The ozone concentrations can cause about −0.6 % of MRE with about −0.8 % for winds and −0.4 % for pressure on the global Rayleigh distributions. The products are now available on the website for the oceanography study. • The LRSAC is used for the atmospheric correction of the ultraviolet imager on HY1C/1D. • The Rrs at MOBY was used to evaluate the accuracy of HY1C/1D Rrs at UV bands. • A Rayleigh LUT was generated from the VSF of the Rayleigh scattering for the AC of UV. • The effects of ozone, wind, and atmospheric pressure are evaluated on the Rayleigh.