Analysis of Atmospheric Pressure Patterns and Surface Wind Circulation Over Nigeria

Mean sea level pressure and associated surface wind circulation patterns form the fundamental atmospheric background against which all weather phenomena in Nigeria operate, yet comprehensive national-scale descriptive analyses remain sparse in Nigerian meteorological literature. This study analyzes the seasonal and inter-annual variability of mean sea level pressure (MSLP) and surface wind patterns over Nigeria using ERA5 reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF) for the period 2015 to 2023. Synoptic composites for the four canonical seasonal periods (early dry season, late dry season, first rainy season, second rainy season) were constructed and analyzed using standard meteorological diagnostic techniques. Streamline analysis of 10-metre wind fields confirms the dominant southwesterly monsoon flow during the rainy season and the contrasting northeasterly harmattan winds of the dry season. The Inter-Tropical Discontinuity (ITD) position, derived from NiMet operational analysis products, is cross-validated against reanalysis-derived moisture flux divergence fields, revealing a mean latitudinal bias of less than one degree. Anomalous pressure configurations associated with exceptional rainfall years are identified using composite difference analysis. The study contributes a consolidated descriptive reference document on Nigerian atmospheric circulation suitable for undergraduate meteorology courses and NiMet operational meteorologist training programs. Keywords: atmospheric pressure, surface wind, ERA5, Inter-Tropical Discontinuity, Nigeria.