Complex Methodology Investigation of Aerosol-Cloud-Radiation Interactions Over the West African Monsoon Region Using Satellite and Reanalysis Data

Aerosol-cloud-radiation interactions in the West African Monsoon system represent a scientifically contested and methodologically complex frontier in tropical meteorology, with significant implications for understanding rainfall variability and future climate projections over Nigeria and the broader region. This study investigates aerosol-cloud-radiation interactions during the West African Monsoon season using an integrated satellite remote sensing and reanalysis diagnostic methodology, providing original empirical contributions for the Nigerian sector of the monsoon system. A multi-sensor dataset combining MODIS aerosol and cloud properties, CERES radiative flux measurements, CloudSat cloud vertical structure profiles, and ERA5 atmospheric dynamics was assembled for the monsoon seasons of 2015 to 2022. A novel compositing methodology stratifying cloud scenes by aerosol type (dust, biomass burning, marine), cloud regime, and dynamical state was developed to disentangle thermodynamic from microphysical aerosol effects on clouds. Results reveal a systematic suppression of shallow convective cloud fraction in dust-laden conditions over northern Nigeria's Guinea Savanna, associated with dust-induced stabilization of the lower troposphere. Over southern Nigeria, biomass burning aerosols from March to April are associated with a first aerosol indirect effect signature in cloud droplet effective radius retrievals, with potential implications for early rainy season onset timing. An original aerosol-convection inhibition index specifically calibrated for the Nigerian monsoon environment is derived and validated against independent radiosonde stability indices. Keywords: aerosol, cloud-radiation interaction, West African Monsoon, MODIS, convection inhibition.