A change comparison of heat wave aspects in climatic zones of Nigeria

Studies have shown an increase in the frequency and severity of heat waves during the last decades under climate change. This study employs four temperature-based definitions, the percentile based TN90th—the 90th percentile of minimum temperature, and TX90th—the 90th percentile of maximum temperature, the Excess Heat Factor (EHF) and the Heat Wave Magnitude Index daily (HWMId), to investigate the present occurrence of heat waves (1981–2016) in five climatic zones of Nigeria. ERA-INTERIM reanalysis daily minimum and maximum temperature data were retrieved from ECMWF database for the purpose. Five characteristics were studied, the heat wave number, duration, frequency, amplitude and the magnitude. The study of heat wave characteristics in different climatic zones revealed that, from 1981 to 2016, heat waves occurred and covered more zones in the last decades. The first heat wave definitions (TN90, TX90 and EHF) revealed almost the same pattern of heat wave number (HWN) in Nigeria from 1981 to 2016 showing that of 1983, 1987, 1997, 2006 and 2007 where the latter had the highest number of events. The general coverage of the number of events increased from 1999. The Sahel was seriously affected by the highest number of events and the highest number of days for the duration and the frequency. The HWMId was used to quantify and compare the intensity of heat waves in the present time and revealed super extreme heat waves (HWMId > 32) in the Sahel and extreme heat waves in the south.