EVALUATION OF PRECIPITABLE WATER VAPOUR OVER SOME STATIONS IN NIGERIA USING ERA-INTERIM AND SURFACE DATA

Abstract

In this research work, precipitable water vapour was investigated using air temperature and relative humidity data for the years 2000 to 2005 retrieved from ERA-interim. Eight selected weather stations which were grouped into three climatic regions (southern, midland and northern) over Nigeria were investigated. Two years in-situ data (2004, 2005) of temperature and Relative humidity were collected from Nigeria Metreological Agency (Nimet) Abuja from which PWV was also calculated. The objectives are to investigate the distribution of PWV over the selected stations and region in Nigeria, to compare the distribution obtained from satellite with that of radiosonde (in-situ) and to use ANOVA method to deduce linear, quadratic and cubic expressions from satellite observations useful for predicting precipitable water vapour over the selected stations and regions. Results show that PWV variation gave rise to two peaks at all the stations and regions with a dip in-between them that is in consonance with the little dry season (LDS) period which is a common occurrence in the coastal region of West Africa. Although the observed LDS in the northern region; is in contrast with the climatology of the area as found in literature which may be due to some of the limitations in satellite derived data. In the comparison of satellite with in-situ data it was observed that the R2 was relatively high for the selected stations showing good correlation. Using ANOVA technique, linear and quadratic models were obtained for precipitable water vapour for the selected stations, it was observed that the quadratic model perform better in the selected stations more than the linear model.