Improved explicit aerosol correction for OMI trace gas retrievals with aerosol-corrected cloud information using satellite observation

Abstract:

Atmospheric aerosols are significant sources of uncertainty in air mass factor (AMF) calculations for trace gas retrievals using satellite UV/visible measurements since aerosols can change the light path length and the total radiance observed by the satellite. The current Smithsonian Astrophysical Observatory (SAO) trace gas products (formaldehyde, water vapor, bromine monoxide, and glyoxal) do not explicitly consider aerosols as cloud retrieval products partially account for aerosol effects. As a result of using the aerosol optical properties and their amount from the Ozone Monitoring Instrument (OMI) aerosol products while still using the cloud fraction from the OMI cloud product, it was found that the aerosol-induced formaldehyde (HCHO) vertical column density (VCD) differences by smoke, dust and sulfate aerosols were 27 %, 6 %, -0.3 % on a global average (Jung et al., 2019). Since these effects may be influenced by cloud contamination even for using reliable aerosol information and can be compensated depending on cloud altitude and cloud fraction in the presence of clouds (Lin et al., 2014), it is required to examine aerosol-cloud interaction for more accurately quantifying the aerosol effects in the trace gas retrievals. In this study, we derive cloud fraction using observed radiance by satellite in the spectral region where the trace gas is retrieved and simultaneously account for aerosols. We first apply it to OMI HCHO retrievals, compare the corrected and previous cloud fraction and AMF and thus quantify the aerosol-induced VCD errors. This analysis will be performed for a variety of aerosol conditions, including biomass burning, urban aerosols, and desert dust, and be helpful to gain a better understanding of the retrieval uncertainty due to aerosols. We will also extend this improved aerosol correction to our OMI H₂O and glyoxal products.