Understanding the Trend of NO2, SO2 and CO over East Africa from 2005 to 2020
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Date
2021
Journal Title
Journal ISSN
Volume Title
Publisher
Atmosphere
Abstract
The atmospheric chemistry constituents of nitrogen dioxide (NO2), sulphur dioxide (SO2)
and carbon monoxide (CO) are associated with air pollution and climate change. In sub-Saharan
Africa, a lack of sufficient ground-based and aircraft observations has, for a long time, limited
the study of these species. This study thus utilized satellite observations as an alternative source
of data to study the abundance of these species over the East African region. The instruments
used included the Ozone Monitoring Instrument (OMI), the Atmospheric InfraRed Sounder (AIRS),
and the TROPOspheric Monitoring Instrument (TROPOMI). An investigation of trends in the data
series from 2005 to 2020 was carried out using the sequential Mann-Kendall test while the Pearson
correlation coefficient was used to compare the data records of the instruments. The analysis revealed
no trend in NO2 (p > 0.05), a decreasing trend in SO2 (p < 0.05), a decreasing trend (p < 0.05) in CO
closer to the surface (850 hPa to 500 hPa) and an increasing trend (p < 0.05) in CO higher up in the
atmosphere (400 hPa to 1 hPa). There is likely a vertical ascent of CO. The correlation between the
instrument records was 0.54 and 0.77 for NO2 and CO, respectively. Furthermore, seasonal fires in
the savanna woodlands were identified as the major source of NO2 and CO over the region, while
cities such as Kampala, Nairobi, and Bujumbura and towns such as Dar es Salaam and Mombasa
were identified as important NO2 hotspots. Similarly, the active volcano at Mt. Nyiragongo near
Goma was identified as the most important SO2 hotspot.
Description
Keywords
Nitrogen dioxide, Sulphur dioxide, Carbon monoxide, OMI, TROPOMI
Citation
Opio, R.; Mugume, I.; Nakatumba-Nabende, J. Understanding the Trend of NO2, SO2 and CO over East Africa from 2005 to 2020. Atmosphere 2021, 12, 1283. https://doi.org/10.3390/atmos12101283