Modelling Surface Ozone Concentration and Its Radiative Effects Over the Niger Delta Region

Surface ozone in the Niger Delta region of South South Nigeria is produced by photochemical reactions between nitrogen oxides and volatile organic compounds emitted by gas flaring, petroleum processing, and vehicular traffic. Elevated surface ozone damages vegetation, respiratory health, and reduces solar energy availability through increased aerosol optical depth. This study develops and validates a photochemical box model for simulating diurnal and seasonal surface ozone concentrations over the Niger Delta, using gas flaring activity data from the World Bank Global Gas Flaring Tracker and meteorological inputs from ERA5 reanalysis. Measured ozone concentrations from two ground-based UV photometric ozone monitors deployed at Warri and Port Harcourt are used for model validation. The radiative forcing contribution of the simulated ozone field is estimated using the SBDART radiative transfer model. Results indicate simulated peak ozone concentrations of 68 to 112 ppb during the dry season at Warri, driven by high NOx emissions from gas flaring combined with low boundary layer height and intense solar radiation. Ozone concentrations exceed the WHO 8-hour guideline of 60 ppb for 35 to 60 percent of dry season hours. The modelled direct radiative forcing of surface ozone reaches minus 2.1 W per square metre at peak ozone conditions. Keywords: surface ozone, gas flaring, Niger Delta, photochemical modelling, radiative forcing