International Journal of Physics | Vol. 2, No. 2, February 2011 | pp. 10–17
DOI: 10.46882/2011/IJP/000014
Article Type: Original Research Paper
Title: Atmospheric Aerosol Optical Depth and Angstrom Exponent Anomalies over Sub-Saharan West Africa
Names of Authors: V. A. Ezenwa¹, G. M. Jenkins²
Authors’ Affiliations: ¹Department of Physics, Nnamdi Azikiwe University, Awka, Nigeria; ²Department of Physics and Astronomy, Howard University, Washington DC, USA
Abstract: Characterizing atmospheric aerosols over West Africa is essential for understanding regional climate variation, radiative forcing, and dust transport patterns across the Atlantic. This paper analyzes variations in aerosol optical depth (AOD at 500 nm) and the Angstrom exponent (alpha at 440-870 nm) collected via multi-wavelength AERONET sun photometers over a five-year window, focusing on sub-Saharan monitoring stations. The dataset reveals a strong seasonal cycle dominated by the influx of mineral dust during the Harmattan season (December to March) and biomass burning plumes during the dry season. The mean AOD peaks dramatically in March at 1.42 ± 0.25, coinciding with a drop in the Angstrom exponent to 0.15 ± 0.04, which indicates the dominant presence of coarse-mode desert dust particles from the Bodélé Depression. In contrast, the wet season (June to September) displays a reduced mean AOD of 0.35 ± 0.12 and an elevated Angstrom exponent of 0.85 ± 0.18, signaling a shift toward fine-mode maritime and anthropogenic aerosols. Ground-based observations were validated against MODIS satellite data, yielding an 89% linear correlation coefficient. These empirical trends provide refined optical constraints for reducing uncertainty in regional climate projection models and atmospheric correction algorithms.
Keywords: Aerosol optical depth; Angstrom exponent; Sun photometer; Mineral dust; Radiative forcing; Sub-Saharan climate; Remote sensing; Atmospheric aerosols.
Manuscript Timeline: Received: November 02, 2010; Revised: December 14, 2010; Accepted: January 11, 2011; Published: February 03, 2011.
Citation: Ezenwa, V. A., & Jenkins, G. M. (2011). Atmospheric Aerosol Optical Depth and Angstrom Exponent Anomalies over Sub-Saharan West Africa. International Journal of Physics, 2(2), 10–17.
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