Aerosol climatology over South Africa based on 10 years of Multiangle Imaging Spectroradiometer (MISR) data

Abstract

[1] In this paper, we present a detailed study of the spatial and seasonal aerosol climatology over South Africa (SA), based on Multiangle Imaging Spectroradiometer (MISR) data. We have used 10 years (2000-2009) of MISR monthly mean aerosol extinction (t ext ), absorption (t a ) optical depths at 558 nm, Angstrom exponents in visible (VIS; 446-672 nm) and near-infrared (NIR; 672-866 nm) spectral bands, and the extracted spectral curvature. The study has shown that, in terms of aerosol load level spatial variation, SA can be classified into three parts: the upper, central, and lower, which illustrate high, medium, and low aerosol loadings, respectively. The results for the three parts of SA are presented in detail. The prevailing sources of aerosols are different in each part of SA. The lower part is dominated by the air mass transport from the surrounding marine environment and other SA or neighboring regions, while the central and upper parts are loaded through windablated mineral dust and local anthropogenic activities. During the biomass burning seasons (July-September), the central part of SA is more affected than the rest of SA by the biomassburning aerosols (based on t a , ∼20% higher than the rest of SA). In alignment with the observed higher values of t ext , aerosol size distributions were found to be highly variable in the upper part of SA, which is due to the high population and the industrial/mining/ agricultural activities in this area.

Optical and microphysical characterization of aerosol layers over South Africa by means of multi-wavelength depolarization and Raman lidar measurements

“…Previous studies have indicated that South Africa is one of the countries in the world that is largely affected by aerosol load, due to various natural and anthropogenic sources (Piketh et al, 2000Formenti et al, 2002Formenti et al, , 2003Campbell et al, 2003;Eck et al, 2003;Freiman and Piketh, 2003;Ichoku et al, 2003;Ross et al, 2003;Winkler et al, 2008;Queface et al, 2011;Tesfaye et al, 2011;Venter et al, 2012;Tiitta et al, 2014). Intensive efforts have been undertaken during recent years to characterize aerosol pollution in South Africa.…”

“…Laakso et al, 2012) and satellite observations (e.g. Tesfaye et al, 2011) in these studies, which are based on columnar aerosol optical properties. Groundbased Raman lidars provide vertically resolved information on the distribution and optical properties of aerosols.…”

Evaluation of climate model aerosol seasonal and spatial variability over Africa using AERONET

“…Mongu and Skukuza in southern Africa have the highest observed α ext , indicating little influence from coarse aerosols and confirming the importance of biomass burning as an aerosol source in this region. Previous studies have shown AOD is highest in this region during the biomass burning season, from AERONET AOD through the year 2007 at Mongu and Skukuza (Queface et al, 2011) and MISR satellite data over South Africa (Tesfaye et al, 2011). Mongu is situated in Zambia in the middle of the biomass burning source region in southern Africa (e.g., Edwards et al, 2006;Queface et al, 2011).…”

“…Biomass burning emissions in southern Africa contribute an estimated 86 % of total carbonaceous aerosols emitted in Africa, which is a higher percentage than other regions worldwide (Bond et al, 2004). In many places, biomass burning aerosols dominate the seasonal cycle of the aerosol column in the region (Tesfaye et al, 2011;Queface et al, 2011;Sivakumar et al, 2010;, which in turn can have a significant impact on the regional climate (Abel et al, 2005;Winkler et al, 2008;Tummon et al, 2010). Although these two sources dominate total column aerosol in Africa, fine anthropogenic aerosols are also observed, including at sites in the Sahara desert and off the coast of northern Africa (Rodríguez et al, 2011;Guirado et al, 2014).…”

Identification and Classification of Different Aerosol Types over a Subtropical Rural Site in Mpumalanga, South Africa: Seasonal Variations as Retrieved from the AERONET Sunphotometer

“…The SA region has been recognized as a major source of aerosols in the southern hemisphere and it is known to be significant in the production and transportation of aerosols with urban and industrial areas as major sources (Siversten et al, 1995;Piketh et al, 1999). Besides these, emissions from biomass burning also contribute relatively significant fraction to the total aerosol loading and is also impacted by airmasses associated with anthropogenic and natural sources, making the region an aerosol hotspot (Piketh et al, 1999;Eck et al, 2001bEck et al, , 2003aQueface et al, 2011;Tesfaye et al, 2011;Kumar et al, 2013a, b).…”