Table 1: The GPS coordinates and the NCEP Reanalysis II coordinates used for this study. Figure 1: The Nigerian NIGNET stations used in this work. The GNSS data for Zaria (ABUZ), Abuja OSGF) and Lagos ( ULAG) were obtained from the Nigerian GNSS Reference Network (NIGNET) (Figure 1). The NIGNET was established by the Office of the OSGoF) in collaboration with SEGAL and Reference Frame, solution 2005 (ITRF2005 is equipped with Trimble CORS, and NetR8 University of ype TRM59800.00. Each of the station has a Surveyor General of t Beira he Federation Interior and Institute Geophysical Infante D. Luiz, Portugal.!! The International Terrestrial , and the GPS coord ABUZ, OSGF and ULAG stations are shown in Table 1. Eac USB modem and inates of the h NIGNET station receivers with choke-ring antenna, a router to enable hem to communicate data to the control centre, where the data is eventually made available for public download at NIGNET website (www.nignet.net). The PWV for the year 2012 had been estimated using combinations of GPS/GNSS data from the NIGNET network of antennae, the NCEP/DOE Reanalysis II data, and surface meteorological data (via the use of Butler’s equation). I that the GPS/GNSS PWV does not have good correlation with the NCEP/DOE Reanalysis II data, nor with the surface data PWV (see Table 2 This is in contrast to other researchers’ results and the weak correlation could be explained from the fact not established to provid weather prediction mode hat the NIGNET network of GPS/GNSS e meteorological information that is vita was observed for summary). stations were in numerical ling, hence the lack of pressure and temperature sensors at the antenna sites. Considering the importance of PWV in weather prediction and climate studies, it is highly recommended by the authors that the government of Nigeria considers the upgrade of the NIGNET network to include pressure and temperature sensors, so hat the GPS/GNSS network could be used for a real- time monitoring of PWV and also facilitate the use of GPS PWV as an important ingredient in numerical weather prediction data assimilation processes. The authors wish to express their gratitude to the Nigerian GNSS network (NIGNET) for the GPS data used in this study. The authors also wish to express their gratitude to the reviewers for their suggestions and comments that has significantly improved the content of the paper. Much appreciation is extended to the Physical Science Division (PSD), Earth System, Research Laboratory (ESRL), Oceanic and Atmospheric Research (OAR), National Oceanic and Atmospheric Administration (NOAA), Boulder, Colorado, USA, for making the NCEP Reanalysis data available through their website (http://www.esrl.noaa.gov/psd/).
