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Identification of sources and sinks of atmospheric aerosols and their impact on east African rainfall

Mmame Bernard, Sunitha Pilli, Samatha Kurimella

Acta Geophysica

2023

Vol. 71, no. 3

1335--1346

Aerosols play a crucial role in climate change by providing a radiation balance between the Earth and atmosphere. In the present study, aerosol sources and sinks have been identified over African region using the Modern-Era Retrospective analysis for Research and Applications, Version 2 reanalysis data from 1985 to 2015. The study mainly focused on climatological and seasonal changes in aerosol distribution and concentrations over African continent and their impact on east African rainfall. Western Africa shows high concentrations of aerosol optical depth (AOD) of greater than 0.3 due to localized pressure changes and diverging winds from the Sahara desert. The highest amount of AOD ( ̴0.8) has been observed in winter season due to strong surface winds and high production of sea salt. When temperature is high in summer season ( ̴306 K), it has been observed that aerosol area distribution increases but their concentration decreases. The highest amount of rainfall ( ̴295 mm) was recorded in the winter season between 1997 and 1998. A strong inverse relationship was observed between aerosol and the east African rainfall. In 2015, the lowest amount of rainfall was observed in the summer season ̴100 mm due to the observed high presence of aerosols. On average, the correlation coefficient between aerosols and precipitation over east Africa has been found to be negative. The increase in rainfall is associated with an increase in relative humidity. However, during the east African monsoon season, the presence of some aerosols cause the development of convective clouds and hence more rainfall.