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Abstract
The sensitivities of oxygen-dimer (O4) slant column densities (SCDs) to changes in aerosol layer height are investigated using the simulated radiances by a radiative transfer model, the Linearlized pseudo-spherical vector discrete ordinate radiative transfer (VLIDORT), and the Differential Optical Absorption Spectroscopy (DOAS) technique. The sensitivities of the O4 index (O4I), which is defined as dividing O4 SCD by 1040 molecules2cm-5, to aerosol types and optical properties are also evaluated and compared. Among the O4 absorption bands at 340, 360, 380, and 477 nm, the O4 absorption band at 477 nm is found to be the most suitable to retrieve the aerosol effective height. However, the O4I at 477 nm is significantly influenced not only by the aerosol layer effective height but also by aerosol vertical profiles, optical properties including single scattering albedo (SSA), aerosol optical depth (AOD), particle size, and surface albedo. Overall, the error of the retrieved aerosol effective height is estimated to be 1276, 846, and 739 m for dust, non-absorbing, and absorbing aerosol, respectively, assuming knowledge on the aerosol vertical distribution shape. Using radiance data from the Ozone Monitoring Instrument (OMI), a new algorithm is developed to derive the aerosol effective height over East Asia after the determination of the aerosol type and AOD from the MODerate resolution Imaging Spectroradiometer (MODIS). About 80% of retrieved aerosol effective heights are within the error range of 1 km compared to those obtained from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) measurements on thick aerosol layer cases.
Highlights
Aerosol is one of the key atmospheric constituents in understanding climate changes with its effects on direct and diffuse solar radiation (e.g., Haywood and Shine, 1995; Kaufman et al, 2002) and plays an important role in air quality near the surface (e.g., Watson et al, 1994; Prospero, 1999)
We proposed an improved differential optical absorption spectroscopy (DOAS) algorithm for the O4 absorption bands to retrieve aerosol height information from the O4 slant column densities (SCDs) based on the sensitivity studies
The sensitivities of the O4 index (O4I) at 340, 360, 380, and 477 nm bands are investigated with radiative transfer model (RTM) calculations to derive the aerosol effective height (AEH) using the space-borne hyperspectral data
Summary
Aerosol is one of the key atmospheric constituents in understanding climate changes with its effects on direct and diffuse solar radiation (e.g., Haywood and Shine, 1995; Kaufman et al, 2002) and plays an important role in air quality near the surface (e.g., Watson et al, 1994; Prospero, 1999) For these reasons, observations from satellite remote sensing have been carried out to investigate aerosol properties at regional and global scale, including aerosol optical depth (AOD) (e.g., Curier et al, 2008; Levy et al, 2007; Torres et al, 2007; Ahn et al, 2014; Veefkind et al, 1999; Zhang et al, 2011), fine-mode fraction (FMF) or Ångström exponent (AE) (e.g., Jones and Christopher, 2007; Lee et al, 2010; Nakajima and Higurashi, 1998; Remer et al, 2008), single scattering albedo (SSA) (e.g., Dubovik et al, 2002; Levy et al, 2007; Jeong and Hsu, 2008; Torres et al, 1998, 2005, 2007; Jethva et al, 2014), and aerosol types (e.g., Higurashi and Nakajima, 2002; Kim et al, 2007; Lee et al, 2010). This new algorithm is applied to the O4 SCD from the OMI to retrieve the aerosol effective height (AEH) for a real case over East Asia, including error estimates
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