Effect of high atmospheric Nitrogen Dioxide (NO2) concentration on GOCI ocean color products

Abstract

This study investigates the effect of atmospheric NO2 on Geostationary Ocean Color Imager (GOCI) ocean color products over the seas around Korean Peninsula. For ocean color remote sensing, absorption and scattering contributions by ocean components (phytoplankton, Colored Dissolved Organic Matter (CDOM), Non-Algal Particles (NAP), etc.) tend to be much weaker than those from the atmosphere (e.g., gas and aerosol). Thus, the contribution from atmospheric components has to be properly removed to retrieve more accurate ocean color products. Whereas the current GOCI atmospheric correction considers absorption by ozone and water vapor, the absorption effect by NO2 is not applied. Recently, some previous studies have shown that high NO2 conditions can cause serious errors in the Top of Atmosphere (TOA) reflectance especially in the blue channel. We are developing NO2 absorption correction technique in GOCI ocean color algorithm. Currently, we examinewhether there is any notable spatial pattern in GOCI remote sensing reflectances (Rrs) and Chlorophyll-a (Chl-a) for high NO2 absorption cases using Ozone Monitoring Instrument (OMI) NO2 data. 6S radiative transfer model was used to calculate transmittance with and without NO2 absorption in the high NO2 conditions. The GOCI-II will be on loaded on Geo-Kompsat-2B(GK-2B) together with Geostationary Environmental Monitoring Satellite (GEMS). Through the combination with GEMS da