Solar Ultraviolet Radiation and Geographical Parameters in Some Selected States in Nigeria

Abstract

Solar ultraviolet (UV) radiation is an important environmental factor with significant implications for human health and ecosystems; however, its spatial variability across Nigeria remains insufficiently characterised. This study investigated the spatial distribution of solar ultraviolet radiation and its relationship with selected geographic parameters across Nigeria. Twenty years (2002–2022) of satellite-derived hourly ultraviolet index (UVI) data obtained from the National Aeronautics and Space Administration (NASA), 8765 data points were collected for each year for the selected 12 states, which are Kebbi, Niger, Kaduna, Kogi, Edo, Oyo, Osun, Anambra, Abia, Bayelsa, Gombe, and Adamawa. UVI data were fitted to the hour 10 AM to 4 PM, which represents peak solar exposure. Descriptive statistics, spatial analysis, scatter-plot anaslysis, and linear regression were employed to assess variations in mean UVI and its relationships with latitude, longitude, and elevation. The results demonstrated substantial spatial variation in mean UVI across the selected states, with generally higher values in northern locations than in southern locations. In general, UVI is usually strongest at the equator and decreases towards the pole. Therefore, the increase in UVI in the northern locations reported in this study is a local phenomenon. Regression analysis revealed strong positive relationships between mean UVI and latitude (R² = 0.7574, B = 0.2728, p < 0.001) and elevation (R² = 0.7420, B = 0.00320, p < 0.001). Longitude exhibit a weaker positive relationship with mean UVI (R² = 0.3153), which was not statistically significant at the 5% level (p = 0.0575). These findings indicate that geographic factors, particularly latitude and elevation, are strongly associated with the spatial variability of solar UV radiation across the selected Nigerian states. The results provide valuable baseline information for identifying areas of elevated UV exposure, and support public health planning, environmental monitoring, and future assessments of UV-related health risks in Nigeria.