Intercomparison and assessment of long-term (2004–2013) multiple satellite aerosol products over two contrasting sites in South Africa. (October 2016)

• Record Type: Journal Article
• Authors: Adesina, A. Joseph; Kumar, K. Raghavendra; Sivakumar, V.; Piketh, Stuart J.
• Is Part Of: Journal of atmospheric and solar-terrestrial physics. Volume 148(2016)
• Page Start: 82
• Page End: 95
• Publication Date: 2016-10
• Subjects: MODIS -- MISR -- Aerosol optical depth -- Aerosol index -- Trend analysis -- South Africa; Geophysics -- Periodicals; Atmospheric physics -- Periodicals; Géophysique -- Périodiques; Météorologie physique -- Périodiques; Electronic journals; 551.51
• DOI: 10.1016/j.jastp.2016.09.001
• Languages: English
• ISSNs: 1364-6826

Abstract

Abstract: To build a long-term database and improve the accuracy of the satellite products used for aerosol studies, there is a need to carry out intercomparison and validation of these satellite observations with ground-based measurements. With this objective, we estimated the long-term inter-annual variations and percentage change in trends of aerosol optical depth (AOD) retrieved from MODerate resolution Imaging Spectroradiometer (MODIS) and Multi-angle Imaging Spectro-Radiometer (MISR) sensors for a 10-year period during 2004–2013 over two distinct sites namely, Skukuza (SKZ; 24.99°S, 31.58°E) and Richards Bay (RBAY; 28.8°S, 21.1°E) in South Africa. The validation performed over SKZ site shows that MISR was better correlated with AErosol RObotic NETwork (AERONET) when compared to Terra and Aqua satellites of MODIS. Later both the MODIS products (Terra and Aqua) were compared on the annual and seasonal basis to derive the relationship between them through scattering plot. The long-term regression analysis performed at these sites shows that the annual trends were decreasing, with the MODIS products underestimating MISR. This is due to difficulties of the MODIS algorithm when dealing with highly complex surface reflectance conditions and aerosol model assumptions. Also, the temporal variations of AOD derived from the two sensors noticed maximum in spring (September/October) and minimum in winter (June). Further, the Ultra-Violet Aerosol Index (UVAI) retrieved from the Ozone Monitoring Instrument (OMI) at the two locations for 9 years (2005–2013) showed a significant increasing trend with a high value of +0.009 yr −1 at SKZ than +0.006 yr −1 at RBAY during the study period, which is due to the transport of dust and smoke particles. Highlights: Validation results showed that MISR is better correlated with AERONET than MODIS. MODIS products found good correlation at coastland than at hinterland. High aerosol loading noticed during spring attributed to biomass burning and forest fires. Analysis showed that MISR overestimated MODIS AOD with decreasing trends. Results revealed that aerosol index increased significantly during the recent years.