Modelling Earth System And Environment

 Journal

 A Predictive Study Of Heat Wave Characteristics And Their Spatio-temporal Trends In Climatic Zones Of Nigeria

 D. Saberma Ragatoa, K. O. Ogunjobi, A. A. Okhimamhe, Nana Ama Browne Klutse, Benjamin L. Lamptey

 2018

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. 

 International Journal Of Climatology

 Journal

 Dust Induced Changes On The West African Summer Monsoon Features

 N'Datchoh, E. T., Diallo, I., Konaré, A., Silué, S., Ogunjobi, K. O, Diedhiou, A. And Doumbia, M.

 2018

Dust generation and transportation from North Africa are thought to modulate the West African Monsoon (WAM) features. In this study, we investigated the relationship between the Saharan Air Layer located above Atlantic Ocean (OSAL) and WAM features, including Monsoon flow, African Easterly Jet (AEJ) and Tropical Easterly Jet (TEJ) over West Africa using the RegCM4 regional model at 30 km grid resolution. Two sets of experiments with and without dust load were performed between 2007 and 2013 over the simulation domain, encompassing the whole of West Africa and a large part of the adjacent Atlantic Ocean. An intercomparison of the two simulations shows that dust load into the atmosphere greatly influences both the wind and temperature structure at different levels, resulting in the observed changes in the main features of the WAM system during summer. These changes lead to a westward shift with a slight strengthening of AEJ core over tropical Atlantic and weakening of both TEJ and monsoon flux penetration over land. In addition, despite running the RegCM4 with prescribed sea surface temperature, a correlation has been found between Aerosol Optical Depths in OSAL and WAM dynamics suggesting a mechanistic link between dust and WAM well reproduced by RegCM4. 

 Royal Society Open Science

 Journal

 Spatio-temporal Analysis Of Land Use Dynamics And Its Potential Indications On Land Surface Temperature In Sokoto Metropolis, Nigeria

 K.O Ogunjobi, Y Adamu, AA Akinsaola And I R Orimoloye

 2018

Land use change is the main driving force of global environmental change and is considered as most central to various debates on sustainable development. Even though a large volume of literature materials is available on land use/land cover change for many areas, very little work has been done on land use and its implications on land surface thermal characteristics over the Sokoto area of Nigeria, despite the strategic importance of the zone, including urbanization, increased population as well as the climate in the area, which is dominated by warm harmattan wind blowing Sahara dust inland. Thus, this study aimed at investigating the implications of urban growth on temporal variations of land surface temperature (LST) using remote sensing and geographic information system (GIS) techniques over Sokoto Metropolis, Nigeria between 1986 and 2016. The change detection of each land use class was carried out for each period using Landsat images obtained from the archives of the United States Geological Survey (USGS). The results revealed that the area has undergone a drastic transformation where built-up area witnessed changes at 10.77%, farmland and vegetation increased at the rate of 0.72% and 2.15%, respectively, for the period of study (1986–2016). While bare soil and water body decreased at the rate of 0.56% and 1.11%, respectively, during the study period. This shows that there exists a transformation from bare surface (desert) to vegetated surface especially between years 2009 and 2016. The LST of Sokoto Metropolis was calculated from the satellite data, and the land surface temperature of each land use class was assessed for the study period. The maximum LST of Sokoto was 30.6°C, 32.8°C and 34.6°C for 1986, 1999 and 2016, respectively. This study has revealed the existence of a positive relationship between built-up area and LST over the area. This development might be as a result of anthropogenic activities through urban growth coupled with its potential impacts on urban climate. These are intensified by constant changes of the space, causing imbalance in the interactions between surface and atmosphere which may be extensively influenced or modified by various forms of land use. 

 Open Access Library Journal

 Journal

 A Trend Analysis Of Temperature In Selected Stations In Nigeria Using Three Different Approaches

 Dakéga Saberma Ragatoa, Kehinde Olufunso Ogunjobi, Appollonia Aimiosino Okhimamhe , Sabastine Dekaa Francis, Lucette Adet

 2018

This study used daily observation data obtained from the Nigerian Meteorological Agency (NiMet) to investigate the temperature trend of Nigeria from 1981-2015. The data were homogenised using the Quantile Matching (QM) method and Quality Controlled. The data have been transformed into three sets of data with different periods: daily, monthly and yearly. The datasets (daily, monthly and yearly) were checked for autocorrelation and if they were found auto correlated, the Modified Mann Kendall (MMK) and the Pre- Whitening (PW) methods were used and compared, if not the normal Mann Kendall (MK) test was applied. The results showed for the different methods, variations in the trend from one station to another and for the minimum and maximum temperature. These variations were observed in the different methods and data screening the performance of each of the methods in the datasets. The general trend was found to be increasing. The variations in the temperature increase the Diurnal Temperature Range (DTR) that impact human health and increase the probability of occurrence of extreme events. 

 Environ Earth Sci

 Journal

 Evaluation Of Present-day Rainfall Simulations Over West Africa In CORDEX Regional Climate Models

 A. Akinsanola And K. O. Ogunjobi,

 2017

The objective of this study is to evaluate the ability of seven CORDEX regional climate models (RCMs), driven by ERA-Interim reanalysis dataset tosimulate the observed rainfall characteristics over West Africa during the period of 1990–2008. The seasonal climatology, annual rainfall cycles, interannual variability 850 hPa specific humidity, and wind fields of the RCMs outputs were assessed over a number of spatial scales covering three climatically homogenous subregions (Guinea Coast, Savannah, and Sahel) and the entire West Africa domain. The ability of the RCMs to simulate the response to El Nino and La Nina events were further assessed. Results indicate that the RCMs captured the spatial pattern of rainfall and the three distinctive phases of the West African monsoon reasonably. It is worth noting that RCA and CRCM5 failed to distinctively reproduce the monsoon jump while CCLM, HIRHAM, and REMO largely overestimated the amount of the pre- and the post-monsoon rainfall. The analysis also showed significant biases in individual models depending on the subregion and season under consideration. These biases appear to be linked to the model’s failure to resolve convective processes and topography accurately. The majority of the RCMs used were consistent with the ground observation in capturing the dry (wet) conditions associated with the El Nino (La Nina) events. Statistical analysis conclusively revealed that the RCMs performance varies over the subregions andseasons, implying that no single model is best at all time. In general, REGCM3 was found to be the most outstanding of all the RCMs and is therefore recommended for use in rainfall assessment over West Africa.

 

 Springer-Verlag Wien

 Journal

 Evaluation Of Rainfall Simulations Over West Africa In Dynamically Downscaled CMIP5 Global Circulation Models

 A.A Akinsanola, V.O Ajayi, A.T Adejare, O.E Adeyeri, I.E Gbode, K.O Ogunjobi, G Nikulin And A.T. Abolude

 2017

This study presents evaluation of the ability of Rossby Centre Regional Climate Model (RCA4) driven by nine global circulation models (GCMs), to skillfully reproduce the key features of rainfall climatology over West Africa for the period of 1980-2005. The seasonal climatology and annual cycle of the RCA4 simulations were assessed over three homogenous subregions of West Africa (Guinea coast, Savannah, and Sahel) and evaluated using observed precipitation data from the Global Precipitation Climatology Project (GPCP). Furthermore, the model output was evaluated using a wide range of statistical measures. The interseasonal and interannual variability of the RCA4 were further assessed over the subregions and the whole of the West Africa domain. Results indicate that the RCA4 captures the spatial and interseasonal rainfall pattern adequately but exhibits a weak performance over the Guinea coast. Findings from the interannual rainfall variability indicate that the model performance is better over the larger West Africa domain than the subregions. The largest difference across the RCA4 simulated annual rainfall was found in the Sahel. Result from the Mann– Kendall test showed no significant trend for the 1980–2005 period in annual rainfall either in GPCP observation data or in the model simulations over West Africa. In many aspects, the RCA4 simulation driven by the HadGEM2-ES perform best over the region. The use of the multimodel ensemble mean has resulted to the improved representation of rainfall characteristics over the study domain

 

 Akinsanola Et Al., J Fundam Renewable Energy Appl 2017, 7:2

 Journal

 Assessment Of Wind Energy Potential For Small Communities In South-South Nigeria: Case Study Of Koluama, Bayelsa State

 Akintomide Afolayan Akinsanola, Kehinde Olufunso Ogunjobi, Akintayo T Abolude, Stefano C Sarris And Kehinde O Ladipo

 2017

Although the concept of wind energy potential assessments has matured considerably, there is only limited application and adoption in regions of energy crisis where electricity demand far exceeds supply. For Nigeria, seeking alternate sources of energy to meet its energy demand is essential and must be met in a sustainable practice. This study analyzed the electricity generation potential from wind at Koluama, Bayelsa State, Nigeria using a combination of 10-m monthly mean wind speed and direction data (1984-2013) and five year daily wind speed data (2009-2013). The data were subjected to different statistical tests and also compared with the two-parameter Weibull probability density function. Maximum mean day of year (DOY) wind speed recorded was 5.25 m/s and minimum wind speed was 0.92 m/s, while seasonal mean wind speed during the dry months (DJF) is estimated to be 4.05 m/s and 4.32 m/s during the wet months of June, July August and September (JJAS) for the 30-year period considered. Wind power density (WPD) ranged from 82 W/m2 to 145 W/m2 in November and August respectively. Lastly, small scale wind-to-electricity power generation was assessed using six (6) practical wind turbines. The AV 928 turbine had the maximum energy yield, despite relatively low capacity factor of less than 10%

 

 Model. Earth Syst. Environ. (2017) 3:34

 Journal

 Radiative Effects Of Dust Aerosol On West African Climate Using Simulations From RegCM4

 K. B. Raji, K. O. Ogunjobi And A. A. Akinsanola.

 2017

A regional climate model (RegCM4.4) has been used to investigate the dynamical effect of dust aerosol radiative forcing and its impact on West African climate. The simulations was performed with the non-dust aerosol version of the model (control) and a dust aerosol module for the year 2010. The spatial and temporal distribution of the aerosol optical depth (AOD) derived from the dust run was compared with observed aerosol data from Aerosol Robotic Network (AERONET) and other satellite products. The results from the simulations show that dust aerosol has a significant impact on West Africa Monsoon (WAM) system. The dust particles induced shortwave (SW) radiative forcing exerted a heating effect at the top of the atmosphere (TOA) over the study area during the DJF season and cooling in MAM. In contrast, the dust induced longwave (LW) radiative forcing exerted an atmospheric cooling during dry season of DJF. The LW radiative forcing at the TOA is maximum during JJA season with the core of 4.3 Wm− 2 over the source region (Bodele). The highest degrees of correlation (r > 0.7) between modeled AOD and (AERONET, MODIS, OMI, and MISR) were observed over Cape Verde. Moderate (0.5 < r < 0.7) to poor correlations (r < 0.5) were also observed over Ilorin, Zinder, Dakar, Ouagadougou, Agoufou, and Banizoumbou. Further results over all the stations revealed that, RegCM4.4 underestimates AOD over Ilorin, Zinder, Cape Verde, Ouagadugou, Agoufou, and Banizoumbou when compared with AERONET and satellite observations except in Dakar where it overestimated AOD from MODIS. All the experiments exhibited a remarkable performance over Guinea and whole West Africa with low RMSE and high positive correlation.

 

 Journal Of Fundamentals Of Renewable Energy And Applications

 Journal

 Assessment Of Wind Energy Potential For Small Communities In South- South Nigeria: Case Study Of Koluama, Bayelsa State

 Akintomide Afolayan Akinsanola, Kehinde Olufunso Ogunjobi, Akintayo T Abolude, Stefano C Sarris And Kehinde O Ladipo

 2017

Although the concept of wind energy potential assessments has matured considerably, there is only limited application and adoption in regions of energy crisis where electricity demand far exceeds supply. For Nigeria, seeking alternate sources of energy to meet its energy demand is essential and must be met in a sustainable practice. This study analyzed the electricity generation potential from wind at Koluama, Bayelsa State, Nigeria using a combination of 10-m monthly mean wind speed and direction data (1984-2013) and five year daily wind speed data (2009-2013). The data were subjected to different statistical tests and also compared with the two-parameter Weibull probability density function. Maximum mean day of year (DOY) wind speed recorded was 5.25 m/s and minimum wind speed was 0.92 m/s, while seasonal mean wind speed during the dry months (DJF) is estimated to be 4.05 m/s and 4.32 m/s during the wet months of June, July August and September (JJAS) for the 30-year period considered. Wind power density (WPD) ranged from 82 W/m2 to 145 W/m2 in November and August respectively. Lastly, small scale wind-to-electricity power generation was assessed using six (6) practical wind turbines. The AV 928 turbine had the maximum energy yield, despite relatively low capacity factor of less than 10%. 

 Springer

 Journal

 Estimation Of Surface Energy Fluxes From Remotely Sensed Data Over Akure, Nigeria

 K. O. Ogunjobi, M. T. Daramola., A. A. Akinsanola

 2017

The spatial variation and composition of surface energy fluxes across different land use over Akure, Nigeria has been investigated using the Surface Energy Balance Algorithm for Land (SEBAL) approach. In 1984, built up area had the lowest net radiation with a mean value of 472.56 W/m2, while the highest net radiation was over the forested area (mean value of 528.93 W/m2). For sensible heat flux, the highest values were observed over the built-up areas with a mean of 245.5 W/m2 and the lowest values over the forested areas (mean value of 160.5 W/m2). Latent heat flux was highest over the forested area with a mean value of 304.1 W/m2 while the built-up area had the lowest latent heat (mean value of 164.3 W/m2). Similar spatial distribution of the surface energy fluxes was observed in 2014. This shows that the distribution of the surface energy fluxes across Akure varies based on the features of the different land covers. Error analysis showed poor estimation of soil heat flux from SEBAL. SEBAL model can be applied for the estimation of surface energy fluxes in areas of sparse ground station data and can also reveal the spatial variation of the energy fluxes.