Assessment of aerosols over five cities of Angola based on MERRA-2 reanalysis data

The use of Aerosol Optical Depth (AOD) has been proven as an alternative to the traditional ground-level monitoring of air quality in many countries across the world. Therefore, this study based on MERRA-2 data aims: (i) to characterize the spatiotemporal and component variations of aerosols in the atmosphere over the capital cities (Luanda, Sumbe, Benguela, Huambo and Lubango) of the five most densely populated provinces of Angola from 2010 to 2020; (ii) to analyze the relationship between the monthly mean variation of the total AOD and the meteorological parameters (precipitation, temperature, wind speed, and relative humidity) in those five cities; and (iii) to assess the influence of emissions from the Nyamuragira volcano, located in the Democratic Republic of Congo, on the air quality at the five cities. The most significant contribution to the total AOD was derived from organic carbon, in all the cities, whereby the highest values (0.19-0.23) were in Luanda. Ranges of sulphates across the coastal cities were higher when compared to the interior cities caused by the emissions inventory data. The value of AOD in all the cities increased and reached the peak during the dry season. The HYSPLIT model showed that air masses from Nyamuragira at various heights in November 2011 reached Luanda and Sumbe, and CALIPSO could confirm the existence of volcanic aerosols in this same period. This study allowed to conclude that the variability of AOD loading depends on seasons and regions, thus providing a little more information about the matter.

Automated summary

This study characterized the spatiotemporal and component variations of aerosols in five capital cities of Angola and analyzed the relationship between total AOD and meteorological parameters. It also assessed the influence of emissions from the Nyamuragira volcano on air quality. The study found that organic carbon contributed the most to total AOD, sulphate ranges were higher in coastal cities, and AOD values peaked during the dry season.