An Assessment of Inter-Annual and Decadal Precipitable Water Vapour Variability and Trends Over North- East Nigeria (1991-2021)

Abstract

The availability of water for domestic, agricultural, and industrial usage in North-East Nigeria depends on the seasonal precipitation. The main reason for the region's crop failure and water scarcity over the past few decades has been the variability in the pattern of precipitation. This study assessed the variability of precipitable water vapour (PWV) over North-East Nigeria, from 1991 to 2021, using the ECMWF ERA5 reanalysis data sets. Mann Kendal, a monotonic trend test, the least square regression and Theil Sen slope estimator were used to analyze the trends and variation of PWV over the region within the period of study. The PWV peaked significantly twice within the duration of the study. The first peak was observed in the year 1997 and recently in the year 2019.   The results showed that negative trends existed at Jalingo, Yola and Bauchi, while positive trends existed in Maiduguri, Yobe and Gombe. The negative trends range between -0.0153 mm year^-1 and -0.247 mm year^-1, while the positive trends range between 0.043 mm year^-1  and 0.243 mm year^-1. The analysis of the PWV decadal trends showed decreasing trend in all the states in the first decade (1991– 2000) and an increasing trend in the second and third decades over all the states within the region with the trend magnitude ranging from 0.259 mm decade^-1 in Jalingo to 2.252 mm decade^-1 in Bauchi. Based on this PWV trend, PWV is expected to be in its increase in the next decade which will translate to an increase in rainfall across the states in the region. Therefore, it is recommended that Government Agencies responsible for the environment should make adequate preparations to mitigate the incidences of flooding in the area.