IMPACT OF CLIMATE VARIABILITY ON THE CONTRIBUTION OF MESOSCALE CONVECTIVE SYSTEMS TO PRECIPITATION IN NORTHERN NIGERIA

Abstract

Mesoscale Convective Systems (MCSs) form an important component of meteorology in West Africa, and in particular, contribute substantially to precipitation totals. Several authors focused majorly on the contribution of these systems to precipitation and the damages that accompanied it. But in the event of current climate change, it is expected that storm occurrences especially over the tropics will also be impacted due to variability or changing in climate especially in Northern Nigeria that depend on precipitation from these systems majorly for farming. The study was carried out on eight (8) states in the savannah region that spans through the Guinea savannah to sahel savannah; and they include Ilorin, Abuja, Jos, Yola, Sokoto, Gusau, Potiskum and Maiduguri. This study was done using monthly total rainfall; mean monthly temperature and relative humidity data of 31 years (1980-2010) and thirty (30) years daily Mesoscale Convective Systems (thunderstorms and line squalls) data to investigate the trend in the climate of the three (3) earlier stated variables and the rate of occurrences of Mesoscale Convective Systems respectively over the period of study. Statistical analysis such as Man-Kendall method, Coefficient of variation (CV), averaging and summation of the daily and monthly data were carried out using Microsoft excel majorly while the Golden surfer software 9.8 was used to produce the spatio-temporal occurrence of Mesoscale Convective Systems over each stations as well as the distribution in coefficient of variation. The coefficient of variation showed that highest variation was recorded between the north-eastern states of Maiduguri and Yola to central north while the variation in relative humidity spanned across the northern extremes (east and west) and the precipitation variation also followed same region as relative humidity over the period of thirty (30) years. There was an increasing trend in the precipitation from (1980-2010) for virtually all the stations except Yola which had a negative trend due to the decrease in the number of occurrences of the storms experienced in the region as shown in figures 4.15a-c . The correlation of the contribution of Mesoscale Convective Systems precipitation to the total precipitation was high on an average for all the stations; but the occurrences of these systems showed that its number decreases by almost one-third with an increasing latitude especially for stations north of 100N. Thus; it can be concluded from the available information provided in this work, that monsoon type of precipitation may be contributing more to the total annual rainfall in the northern part of Nigeria as regards to earlier studies which revealed that the systems contributes as high as 95% of total precipitation in the area.