Meteorological Drivers of Solar Resource Variability and Solar Energy Applications: Evidence from Eight Sites in Zambia

This study investigated the meteorological factors influencing solar irradiance variability across eight sites in Zambia, using a 10-year monthly dataset covering 2014 to 2024. Ground-based solar irradiance and meteorological data from the Southern African Science Service Centre for Climate Change and Adaptive Land Management (SASSCAL) network, complemented by NASA POWER satellite data and Meteonorm sunshine duration data were used. Physical plausibility tests were performed on the SASSCAL records prior to analysis, after which temporal, spatial, worst-month, and correlation-based methods were used to characterise irradiance behaviour and its atmospheric controls. The results show a consistent annual irradiance cycle which reaches its peak in September-October and declines during the rainy season or cool-dry season depending on a specific location. Kalabo and Samfya showed the highest mean irradiance and seasonal stability, whereas Mpulungu and Mwinilunga recorded lower solar irradiance values and deeper wet-season minima. Worst-month analysis identified January as the critical low-resource month for northern and lake-proximate sites, and June-July for plateau, western, and southern locations. Cloud amount, precipitation and relative humidity emerged as the main suppressors of irradiance, while temperature showed a positive relation and wind speed exhibited site-dependent effects. Atmospheric transparency, as reflected in sunshine duration contrasts, rather than minor differences in astronomical day length, explained the observed spatial differences. These results demonstrate that Zambia's solar resource cannot be characterised by a single national baseline, and that site-specific meteorological conditions should be the basis for solar resource assessment and photovoltaic planning across the country.