Diurnal and seasonal variations of surface water vapour density over some meteorological stations in Nigeria

Abstract

The diurnal and seasonal variations of Surface Water Vapour Density (SWVD) over seven Meteorological
stations in Nigeria during the decadal period 1987-1996 were investigated using daily mean temperature and relative humidity data. The data were obtained from the archives of the Nigerian Meteorological  Agency,   Oshodi, Lagos. The stations were so selected to show a South-North transect and were  representative of the regions to which they belong, namely: the Southern, the Midland and the Sahelian (Northern) regions. Results showed that the variations in each station and regions were influenced by the prevailing atmospheric conditions. These atmospheric conditions were controlled by the surface Inter-Tropical Discontinuity (ITD), and the topographical features of each of the stations and regions. Values of daily mean surface water vapour density were found to be higher at midnight than at midday at the  Southern stations of Ikeja, and Ibadan together with the Sahelian stations of Kaduna, Zaria, and Kano; whereas at the Midland stations of Ilorin and Minna, the reverse was the case. During the dry season, the daily mean value at Ikeja and Ibadan was 20.07±0.45, at Ilorin and Minna was 15.91±0.79, and at the three Sahelian stations, was 5.29±0.39; while during the rainy season, they were 21.72±1.22, 19.60±0.12 and 19.47±0.07 for the Southern, Midland and Northern regions respectively. The variations, diurnally and seasonally, were in synchronism with the north-south movement of the surface ITD.

Keywords: Diurnal, Inter-Tropical Discontinuity, Topographical Features, Midland Zone, Synchronism.