Articles | Volume 15, issue 8
Atmos. Chem. Phys., 15, 4259–4278, 2015
Atmos. Chem. Phys., 15, 4259–4278, 2015

Research article 24 Apr 2015

Research article | 24 Apr 2015

An overview of regional and local characteristics of aerosols in South Africa using satellite, ground, and modeling data

S. P. Hersey1,2, R. M. Garland2,3, E. Crosbie4, T. Shingler4, A. Sorooshian4,5, S. Piketh1, and R. Burger1 S. P. Hersey et al.
  • 1Department of Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
  • 2Now at Franklin W. Olin College of Engineering, Needham, MA, USA
  • 3Council for Scientific and Industrial Research (CSIR), Pretoria, South Africa
  • 4Department of Atmospheric Sciences, University of Arizona, Tucson, AZ, USA
  • 5Department of Chemical and Environmental Engineering, University of Arizona, Tucson, AZ, USA

Abstract. We present a comprehensive overview of particulate air quality across the five major metropolitan areas of South Africa (Cape Town, Bloemfontein, Johannesburg and Tshwane (Gauteng Province), the Industrial Highveld Air Quality Priority Area (HVAPA), and Durban), based on a decadal (1 January 2000 to 31 December 2009) aerosol climatology from multiple satellite platforms and detailed analysis of ground-based data from 19 sites throughout Gauteng Province. Satellite analysis was based on aerosol optical depth (AOD) from MODIS Aqua and Terra (550 nm) and MISR (555 nm) platforms, Ångström Exponent (α) from MODIS Aqua (550/865 nm) and Terra (470/660 nm), ultraviolet aerosol index (UVAI) from TOMS, and results from the Goddard Ozone Chemistry Aerosol Radiation and Transport (GOCART) model. At continentally influenced sites, AOD, α, and UVAI reach maxima (0.12–0.20, 1.0–1.8, and 1.0–1.2, respectively) during austral spring (September–October), coinciding with a period of enhanced dust generation and the maximum integrated intensity of close-proximity and subtropical fires identified by MODIS Fire Information for Resource Management System (FIRMS). Minima in AOD, α, and UVAI occur during winter. Results from ground monitoring indicate that low-income township sites experience by far the worst particulate air quality in South Africa, with seasonally averaged PM10 concentrations as much as 136% higher in townships that in industrial areas.

We report poor agreement between satellite and ground aerosol measurements, with maximum surface aerosol concentrations coinciding with minima in AOD, α, and UVAI. This result suggests that remotely sensed data are not an appropriate surrogate for ground air quality in metropolitan South Africa.

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Short summary
A decadal aerosol climatology of South Africa's major metropolitan areas is presented, utilizing data from multiple satellite platforms and 19 ground-monitoring sites. Remotely sensed data are dominated by a seasonal signal corresponding to transported biomass burning during austral spring, while ground data are dominated by domestic burning in low-income areas during austral winter. We report poor agreement between satellite- and ground-based aerosol measurements.
Final-revised paper