Browsing by Author "Okhimamhe, A.A."
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Item A change comparison of heat wave aspects in climatic zones of Nigeria.(Environmental Earth Sciences, 2019) Ragatoa, D.S.; Ogunjobi, K.O.; Klutse, N.A.B.; Okhimamhe, A.A.; Eichie, J.O.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 southItem A predictive study of heat wave characteristics and their spatiotemporal trends in climatic zones of Nigeria(Modeling Earth Systems and Environment, 2018) Ragatoa, D.S.,; Ogunjobi, K.O.; Okhimamhe, A.A.; Klutse, N.A.B.; Lamptey, B.L.Heat waves (HWs) have always been the silent natural disaster but the most impactful, especially concerning health and agriculture. A crucial question is being asked after the evidence has shown increases in the climate extreme events especially the temperature: how will the future climate conditions be? The present investigation examines and analyzes the future occurrence and trend of HWs in the five climatic zones of Nigeria. WRF model output extracted from CORDEX-Africa for the period 2018–2100 was compiled using maximum and minimum temperatures under RCP4.5 and RCP8.5. Different HW characteristics were studied: the heat wave number, the duration, the frequency, the amplitude and the magnitude exploiting four different definitions, the temperature based 90th percentile thresholds (TN90 and TX90), the Excess Heat Factor (EHF) and the Heat Wave Magnitude Index daily (HWMId). The prediction under the two scenarios RCP4.5 and RCP8.5 has shown a spatial increase in the frequency and magnitude of HWs during different periods. In the 2050s, there will be a spatial increase and also an increase in the duration of HWs in the study area. The HWMId revealed Ultra extreme HWs when the Coastal zone will be having Super extreme HWs. The RCP8.5 revealed more dramatic and dreadful HWs from 2073. The trend showed significant increasing trends in the major parts of the country