Trends in extreme temperature over Nigeria from percentile‐based threshold indices

Abstract

This study analyses spatial and temporal trends in extreme temperature indices over Nigeria. The percentile indices were calculated from newly homogenized daily minimum and maximum temperature data for the period 1971-2012 for 21 stations in Nigeria. Indices describing the characteristics of hot extremes and cold extremes are calculated with the RClimDex software. The annual and seasonal trends in these indices are obtained using the ordinary least square fit and the statistical significance tested using the R-based modified Mann-Kendall test. We examine characteristics of these indices for the entire country and separately for the three geographical zones in Nigeria: Guinea, Savanna, and Sahel. The spatial and temporal patterns of trends in the indices indicate that Nigeria has experienced statistically significant increase in the frequency of hot extreme and decrease in cold extreme events. Although majority of the stations have significant trends in warm days and warm nights, the annual trend is greatest in warm nights. In addition, the rate of warming in minimum temperature ('warm nights') is stronger (MAM). As for the trends in cold days and cold nights, the trends in cold nights are larger than for cold days at both the annual and seasonal scales. The regional analysis indicates that trends in warm nights and cold nights are most pronounced in Guinea and Sahel regions.

<strong>Changes in Diurnal Temperature and Precipitation Extremes in North Central Region of Nigeria</strong>

“…The precipitation indices, consisting of annual total precipitation, number of wet days, monthly maximum 1-day precipitation, monthly maximum consecutive 5-day precipitation, annual number of days when precipitation is greater than 10 mm, annual number of days when precipitation is greater than 20 mm increased while consecutive wet days decreased. These findings correspond with other observed climate extremes reported in similar studies [38,[45][46][47]. The use of renewable energy tools to reduce the amount of greenhouse gases in the atmosphere and a means of dissipating water bodies.…”

“…Regional studies have shown similar trends in temperature indices with this study. A general warming trend was found throughout the Guinea, Savanna, and Sahel region of Nigeria from 1971-2012 [45,47,51] as there were more frequent warm nights and days and less cool nights and days. Also the precipitation trend increased but not as significant as temperature indices.…”

“…Thus, this study was needed to evaluate the long-term variability in ambient surface temperature and precipitation in north central region, situated in the Sahelian region of Nigeria. Although a few studies on changes in precipitation and temperature extremes have been reported in Nigeria, most reports considered meteorological data that were restricted to very limited local weather stations [45][46][47][48]. Research on climate changes in extremes across different geographic regions and timescales in the country is sparse.…”

Trends and variability in absolute indices of temperature extremes over Nigeria: linkage with NAO

“…Several studies have applied one or a combination of the indices to examine trends in extreme temperature events in different regions of the world including Africa in general, and Nigeria in particular (e.g. Alexander et al, 2006;Fontaine et al, 2013;Kruger and Sekele, 2013;Mackellar et al, 2014;Abatan et al, 2016). These indices have produced robust statistical information.…”

“…The spatial and temporal characteristics study of daily temperature extremes over Southern and West Africa show patterns consistent with warming over most of the regions . In Nigeria, Abatan et al (2016) used only percentile-based threshold indices to examine trends in extreme temperature. Their work reported that all the regions in Nigeria were characterized by significant increases in annual frequency of warm days and night, while annual frequency of cold days and nights have similar proportions of significant decreases.…”