Retrieval of UV-Visible aerosol absorption using AERONET and OMI-MODIS synergy: Spatial and temporal variability across major aerosol environments

Abstract

Abstract. Measuring spectral aerosol absorption remains a challenging task in aerosol studies, especially in the UV region, where the ground and airborne measurements are sparse. In this research, we introduce an algorithm that synergizes ground measurements with satellite observations for the derivation of spectral single scattering albedo (SSA, ωo) of aerosols in the UV to visible range (340–670 nm). The approach consists in explaining satellite measured near-UV radiances (340, 354 and 388 nm) by the Ozone Monitoring Instrument (OMI), and visible radiances (466 and 646 nm) by MODerate Imaging Spectrometer (MODIS), in terms of ground-based Aerosol Robotic Network (AERONET) measurements of total column extinction aerosol optical depth (AOD, τ), and retrieved total column wavelength dependent SSA using radiative transfer calculations. Required information on aerosol particle size distribution is taken from an AERONET-based climatology specifically developed for this project. This inversion procedure is applied over 110 AERONET sites distributed worldwide, for which continuous, long-term AERONET measurements are available. Using the derived data set we present seasonal and regional climatology of ωo(λ) for carbonaceous, dust and urban/industrial aerosol types. The UV-Visible spectral dependence of ωo obtained for the three major aerosol types from the synergy algorithm is found to be consistent with the in situ measurements reported in the literature. A comparison to standard AERONET SSA product at 646 nm shows absolute differences within 0.03 (0.05) for 40 % (59 %) of the compared observations. The derived aerosol ωo(λ) data set provides a valuable addition to the existing aerosol absorption record from AERONET by extending the absorption retrieval capability to the near-UV region. The combined UV-Visible data set, in addition to improving our understanding of spectral aerosol absorption properties, also offers wavelength-dependent dynamic aerosol absorption models for use in the satellite-based aerosol retrieval algorithms.