This study presents the temporal variation in K↓ and PAR at Lusaka, Zambia. A strong positive correlation between them is demonstrated. The mean daily PAR/K↓ ratio decreased during the cool-dry season, decreased then increased during the hot-dry season and increased in the warm-wet season. This variation was mainly due to trends in cloudiness and the associated atmospheric moisture associated with the movement of the Hadley cell circulation system. However, the role of pyrogenic aerosols is found to be unequivocal and considerable. Days that were classified as cloudy-bright and very cloudy had mean daily PAR/K↓ ratios considerably higher than days classified as near-cloudless and cloudless. Although the magnitude of the clearness index affects the PAR/K↓ ratio, it cannot be used as a predictive tool by itself. When present, pyrogenic aerosols tended to influence the PAR/K↓ ratio at all time scales, resulting in considerable decreases in the ratio, especially during the peak biomass burning period.