This study evaluates the optical and microphysical properties of atmospheric aerosols over Chad using satellite data from the MODIS, MISR, SeaWIFS, and OMI sensors, as well as the MERRA-2 reanalysis, with the aim of identifying the most suitable instrument for their monitoring. A comparison of aerosol optical depth (AOD) values reveals a systematic underestimation by MERRA-2, while MODIS, MISR, SeaWIFS, and OMI tend to overestimate them. Linear correlation analysis shows that MODIS exhibits the strongest correlation with MERRA-2 (R = 0.62), followed by MISR (R = 0.61), SeaWIFS (R = 0.55), and OMI (R = 0.41). The spatio-temporal analysis of monthly variations reveals a high aerosol load during spring and summer, as confirmed by the annual cycles of AOD at 550 nm and the ？ngstr？m exponent (412 - 470 nm), indicating the predominance of desert dust. Conversely, the concentrations of other aerosol types remain low during both summer and winter. The aerosol index (AI), measured by OMI and TOMS, also highlights a strong presence of absorbing aerosols, with a maximum observed in May and respective minima in September and November. Analysis of the seasonal variability in the distribution of the ？ngstr？m exponent (AE) as a function of AOD shows the predominance of accumulation and coarse modes, mainly associated with mineral dust. These results confirm the reliability of the MODIS sensor for aerosol monitoring over Chad, where accumulation and coarse modes dominate the atmosphere.
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