Abstract
Abstract. Quantifying aerosol absorption at ultraviolet (UV) wavelengths is important for monitoring air pollution and aerosol amounts using current (e.g., Aura/OMI) and future (e.g., TROPOMI, TEMPO, GEMS, and Sentinel-4) satellite measurements. Measurements of column average atmospheric aerosol single scattering albedo (SSA) are performed on the ground by the NASA AERONET in the visible (VIS) and near-infrared (NIR) wavelengths and in the UV-VIS-NIR by the SKYNET networks. Previous comparison studies have focused on VIS and NIR wavelengths due to the lack of co-incident measurements of aerosol and gaseous absorption properties in the UV. This study compares the SKYNET-retrieved SSA in the UV with the SSA derived from a combination of AERONET, MFRSR, and Pandora (AMP) retrievals in Seoul, South Korea, in spring and summer 2016. The results show that the spectrally invariant surface albedo assumed in the SKYNET SSA retrievals leads to underestimated SSA compared to AMP values at near UV wavelengths. Re-processed SKYNET inversions using spectrally varying surface albedo, consistent with the AERONET retrieval improve agreement with AMP SSA. The combined AMP inversions allow for separating aerosol and gaseous (NO2 and O3) absorption and provide aerosol retrievals from the shortest UVB (305 nm) through VIS to NIR wavelengths (870 nm).
Highlights
Aerosols affect both the surface and outgoing radiation affecting Earth’s radiative balance
Hammer et al (2016) showed that carbonaceous aerosol absorption over most biomass burning regions is underestimated if organic carbon (OC) is regarded as purely scattering in a global 3-D chemistry transport model (CTM) GEOS-Chem, while a better agreement is obtained with satellite observations from the Ozone Monitoring Instrument (OMI) on board NASA’s Aura satellite after implementing the brown carbon” (BrC) absorption parameterization
Where Vdirn (λ, t) is the Multifilter Rotating Shadowband Radiometer (MFRSR)-measured direct normal voltage, τa (λ, t) is gaseous corrected and spectrally interpolated or extrapolated aerosol optical depth (AOD) to the MFRSR wavelengths applying a fit of the equation (ln τa = a0 + a1 ln λ + a2(ln λ)2) (Eck et al, 1999) using AERONET spectral level 2 AOD, τR (λ, t) is the Rayleigh optical depth inferred from the measured surface pressure, and τNO2 (λ, t) and τO3 (λ, t) are NO2 and ozone optical depths, calculated using Pandora column NO2 and ozone measurements, interpolated to MFRSR 1 min measurements (Herman et al, 2009; Tzortziou et al, 2012)
Summary
Aerosols affect both the surface and outgoing radiation affecting Earth’s radiative balance. Hammer et al (2016) showed that carbonaceous aerosol absorption over most biomass burning regions is underestimated if OC is regarded as purely scattering in a global 3-D CTM GEOS-Chem, while a better agreement is obtained with satellite observations from the Ozone Monitoring Instrument (OMI) on board NASA’s Aura satellite after implementing the BrC absorption parameterization. The shadowband technique for aerosol absorption retrievals does not require separate calibrations for direct and diffuse measurements and allows more frequent (up to one minute) measurements This technique is more accurate at small solar zenith angles (SZA) (Krotkov et al, 2005a, b) complementing AERONET standard almucantar inversions, which are less sensitive for small SZAs (Dubovik et al, 2002). It facilitates future comparisons of independent satellite SSA retrievals in the UV from the OMI (Torres et al, 1998, 2007, 2013; Jethva and Torres, 2011; Jethva et al, 2014)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
