Assessment of GPS-Derived Precipitable Water Vapour for Meteorological Applications in Nigeria

GPS-derived precipitable water vapour constitutes an emerging atmospheric sensing capability with significant potential for improving weather forecasting and climate monitoring in data-sparse tropical environments such as Nigeria. This study assesses the accuracy and meteorological utility of GPS-derived precipitable water vapour estimated from CORS network data in Nigeria, addressing an identified gap in the application of geodetic GPS infrastructure for atmospheric science in West Africa. Zenith wet delay and precipitable water vapour estimates are computed from three years of RINEX data from six CORS stations distributed across Nigeria's six geopolitical zones, using the BERNESE precise point positioning software. GPS-PWV estimates are compared with radiosonde-derived PWV measurements from the Abuja and Lagos upper-air stations and with ERA5 reanalysis data, using bias, root mean square error, and Pearson correlation as evaluation metrics. GPS-PWV shows strong correlation with radiosonde observations, with RMSE values of 3.1 to 4.8 mm, comparable to performance reported for similar networks in East Africa. Analysis of temporal PWV anomalies in relation to extreme rainfall events recorded by the Nigerian Meteorological Agency demonstrates statistically significant GPS-PWV surge signals twelve to twenty-four hours before rainfall exceeding fifty millimetres. The study establishes a methodological foundation for integrating GPS-PWV into the NiMet numerical weather prediction assimilation pipeline. Keywords: GPS precipitable water vapour, CORS network, Nigeria, weather prediction, atmospheric sensing.