Empirical Modeling of Layered Integrated Water Vapor Using Surface Mixing Ratio in Nigeria

Abstract

Using the available upper-air data for three stations in Nigeria (Lagos, a coastal station; Minna, an inland station; and Kano, a sub-Sahelian station), an intensive examination has been carried out on the linkage between surface mixing ratio rs and layered integrated water vapor W (g cm?2) over Nigeria. The goal was to identify the seasonal distribution of the parameter and to develop models that can best be used to estimate W from surface mixing ratio. To achieve these objectives, integrated water vapor at the low level (WL), midlevel (Wm), and upper level (Wu) and total column integrated water WT have been calculated using daily values of upper-air data spanning over a decade from the above three radiosonde stations. A relationship of the form W = αrs + ? (where α and ? are constants) has been established between W and rs using the analysis-of-variance (ANOVA) technique. Tests carried out on the models, using daily soundings made in 1990 for Lagos, 1983 for Minna, and 1991 for Kano, respectively, gave encouraging results as established by the use of Kolmogorov?Smirnov tests. Owing to the difference in the climatological patterns of precipitation among the different regions in Nigeria (i.e., southern, midland, and northern regions) as represented by the three stations, no single relationship was found to be suitable for the entire country of Nigeria. Earlier models, generally of the form W = αqb (where α and b are constants and q is specific humidity), were found to be less adequate over the stations.