Seasonal climatology and relationship between AOD and cloud properties inferred from the MODIS over Malawi, Southeast Africa

The studies related to aerosol and cloud properties are rare over the South Eastern African continent despite their significant influence on the regional climate. The present work is aimed at analyzing the spatiotemporal correlations between aerosol and cloud properties during 2008–2017 derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) over the Republic of Malawi, Southeast Africa. The annual mean aerosol optical depth at 550 nm (AOD550) was found high (>0.23) around the Lake Malawi and its environments, and in the southern parts of the study domain, characterized by dense population and increased anthropogenic activities. Whereas, low AOD centers were noticed over the high-altitude locations of central Malawi. The seasonal mean AOD550 was found high during September-October-November (SON) (0.32) and June-July-August (JJA) (0.24) December-January-February (DJF) (0.2), and lowest in March-April-May (MAM) (0.16). The Angstrom exponent (AE412-470) sensitive to fine-mode particles was found high (>1.2) in most of the regions during the study period. The trend analysis from the linear regression technique found a general increase in AOD, except during SON was characterized by decreasing AOD. Besides, we investigated on understanding the relationship between AOD and cloud microphysical properties over the domain. The AOD550 exhibited a negative correlation with cloud fraction (CF) and the cloud effective radius (CER). However, it showed a positive correlation with cloud top temperature (CTT) in areas of high AOD. Finally, the results from the backward trajectory analysis revealed that aerosols over Malawi were associated with long-range transport from the Arabian Deserts, Madagascar Island, Central Africa, and the Indian Ocean, along with locally produced aerosols during different seasons. The findings may be useful to better understand the sources and climatic effects of atmospheric aerosols in southeast Africa.