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AJAYI VINCENT OLANREWAJU

Publication

Publisher:
 Meteorlogical Applications
Publication Type:
 Journal
Publication Title:
 Observed Changes In Climate Extremes In Nigeria
Publication Authors:
 Imoleayo Ezekiel Gbode, Oluwafemi Adeyeri, Kaah P. Menang, Akintomide Afolayan AkinsanolaA
Year Published:
 2019
Abstract:
This study presents observed changes in climate extremes using daily precipitation and temperature data over twenty?four (24) stations, covering the three climatic zones (Guinea coast, Savannah and Sahel) of Nigeria for the period of 1971?2013. The data was homogenized with the Expert Team on Climate Change Detection Indices (ETCCDI) RHtests version 4 software. RClimDex version 1.0 was used to calculate seventeen (17) of the ETCCDI recommended precipitation and temperature extreme indices. The spatio?temporal variation in the observed trends was analysed over each of the climatic zones. Results show significant increase in the frequencies of warm spell, warm days and nights and decreasing cold spell, cold days and nights over the three climatic zones. Significant increase in annual total precipitation was found in some stations across the Guinea coast and Sahel zones. Changes in consecutive dry days and consecutive wet days are non?significant in most stations. Also, significant increase in extremely wet days was observed in few stations across the three climatic zones. Implication of the observed warming could, however, result to thermal discomfort of lives in areas with significant positive trends. This could also exert pressure on the economy’s power sector, as energy demand for cooling will increase. The increase in total annual precipitation will potentially be favorable for hydropower generation and increase the availability of potable water supply for both industrial and domestic uses in the country. However, the increase in consecutive dry days and decrease in consecutive wet days are dangerous for agricultural practices and hence food security. 
Publisher:
 Springer
Publication Type:
 Journal
Publication Title:
 Temperature Extremes Over Selected Stations In Nigeria
Publication Authors:
 Emmanuel Olaoluwa Eresanya, Ajayi Vincent, Mojolaoluwa Daramola, Ayodeji Balogun
Year Published:
 2018
Abstract:
This research aims to determine the temperature extremes for Ikeja (Lagos), Osogbo (Osun) and Maiduguri (Borno), Nigeria, West Africa using Statistica analytical tool. Thirty (30) years daily maximum and minimum temperature data for Lagos, Osogbo and Maiduguri used for this study were collected from Nigeria Meteorological Agency (NIMET), Oshodi, Nigeria. Analysis of extreme temperature trend indicated that in Ikeja the percentage occurrence of warm days (TX90P) in which the maximum temperature is above 34°C (90 th percentile value) is increasing and the percentage occurrence of cold days (TX10P) in which the maximum temperature is below 28°C [10 th percentile value] is decreasing, in Osogbo the percentage occurrence of warm days (TX90P) in which the maximum temperature is above 35°C [90 th percentile value) is increasing at a slower rate whereas the percentage occurrence of cold days (TX10P, number of days) in which the maximum temperature is below 27°C [10 th percentile value] is constant while in Maiduguri the percentage occurrence of warm days (TX90P, number of days) in which the maximum temperature is above 41°C [90 th percentile value] is constant whereas the percentage occurrence of cold days (TX10P, Original Research Article Eresanya et al.; PSIJ, 20(1): 1-10, 2018; Article no.PSIJ.34637 2 number of days) in which the maximum temperature is below 30°C [10 th percentile value] is slightly increasing. Percentage of warm days indicate constant value at around 13-15% during the three (3) decades under investigation across the study areas while day time cooling increases slightly by 2% in Ikeja, 1% in Osogbo and 3% in Maiduguri significant level and Cold night decrease at 1% in Ikeja and remain constant in Osogbo but decrease by 5% in Maiduguri significant level. 
Publisher:
 Environmental Research Letters
Publication Type:
 Journal
Publication Title:
 Potential Impact Of 1.5°C And 2°C Global Warming On Consecutive Dry And Wet Days Over West Africa
Publication Authors:
 Nana Ama Browne Klutse, Vincent O. Ajayi, Emiola Olabode Gbobaniyi, Temitope S. Egbebiyi Kouakou Kouadio, Francis Nkrumah, Kwesi Akumenyi Quagraine, Christiana Olusegun, Ulrich Diasso, Babatunde J. Abiodun, Kamoru Lawal, Grigory Nikulin, Christopher Lennard, Alessandro Dosio
Year Published:
 2018
Abstract:
We examine the impact of +1.5oC and +2oC global warming levels above pre-industrial levels on Consecutive dry days (CDD) and Consecutive wet days (CWD), two key indicators for extreme precipitation and seasonal drought. This is done using climate projections from a multi-model ensemble of 25 regional climate model (RCM) simulations. The RCMs take boundary conditions from ten global climate models (GCMs) under the RCP8.5 scenario. We define CDD as the maximum number of consecutive days with rainfall amount less than 1 mm and CWD as the maximum number of consecutive days with rainfall amount more than 1 mm. The differences in model representations of the change in CDD and CWD, at 1.5oC and 2oC global warming, and based on the control period 1971-2000 are reported. The models agree on a noticeable response to both 1.5oC and 2oC warming for each index. Enhanced warming results in a reduction in mean rainfall across the region. More than 80% of ensemble members agree that CDD will increase over the Guinea Coast, in tandem with a projected decrease in CWD at both 1.5oC and 2oC global warming levels. These projected changes may influence already fragile ecosystems and agriculture in the region, both of which are strongly affected by mean rainfall and the length of wet and dry periods. 
Publisher:
 Center For Atmospheric Research
Publication Type:
 Journal
Publication Title:
 On The Understanding And Estimates Of Dust Deposition In The West Africa Region
Publication Authors:
 Julius Akinyoola, Ajayi Vincent, Ayodeji Oluleye, Emmanuel Olaoluwa Eresanya
Year Published:
 2018
Abstract:
Rainout and washout deposition are important features of dust investiagtion in the West Africa region. In this work, International Centre for Theoretical Physics (ICTP), Regional climate model version 4 (RegCM4.6) was employed to simulate seasonal cycle of dust deposition in the West africa region with special focus on Sahara dust storm during 2005. An experiment was performed with the activated dust module while the dust deposition were analysed along with other atmospheric responses. The results were compared to satellite data from MERRA-2 and it was discovered that the annual mean wet deposition peaks was found in the coast and inland part of Nigeria. The 0.01-10/2.5-5.0 micron metre dust has peak value range between 1.45 – 1.85 mg m-2 day-1 and decreases Northward (i.e from the coast to Savanah and Sahel region) with minimum values of 0.25 – 0.55 mg m-2 day-1 driven by dynamics of ITD/ITCZ while there were Southward migration of mineral dust dry deposition from the Sahel to the Guinea coast with deposition velocity vary between 0.001-0.01 m/s across the region from Winter to Summer. It was concluded that the spatial distribution and seasonality of deposition of dust vary greatly according to dust size and also influenced by precipitation amount and seasonal distribution and as well as wind velocity increase in the winter 
Publisher:
 Springer
Publication Type:
 Journal
Publication Title:
 Assessing Remotely Sensed Temperature Humidity Index As Human Comfort Indicator Relative To Landuse Landcover Change In Abuja, Nigeria
Publication Authors:
 Ige S. O.Ige S. O.Ajayi VincentAjayi VincentOluwafemi AdeyeriOluwafemi AdeyeriK. S. A. OyekanK. S. A. Oyekan
Year Published:
 2017
Abstract:
Abuja, Nigeria’s capital city has witnessed remarkable expansion, growth and developmental activities since its inception in 1976. This mass inrush and settlement of people often leads to the replacement of the natural land cover with urban infrastructural facilities resulting in micro-climate change and worsening thermal environmental conditions. It is therefore pertinent to study the thermal environment of the city if Abuja will avoid the associated problems of growing and expanding city like many others in the world. Thus this study examines the use of remote sensing and geographic information system in mapping the temperature humidity index (THI) as human comfort indicator relative to land use land cover change in Abuja using Landsat Thematic Mapper, Enhanced Thematic Mapper + and Landsat 8 Operational Land Imager/Thermal Infrared Sensor data of 1987, 1999, 2009 and 2014. This is to assess the changes that have taken place between these periods. Subsequently, an attempt was made at comparing differences in the THI between five different land cover classes: water body, built-up area, closed canopy vegetation, open vegetation and waste land. The results show that the declining trend of vegetation cover between 1987–1999, and 2009–2014 saw a rise in the region with THI > 26 (discomfort) while the periods between 1999 and 2009 where there was a remarkable improvement in the vegetation cover saw an increase in region where comfortable condition is achieved. The discomfort index class category is the most dominant across most of the land cover classes except in the water body and closed canopy class categories. This order of dominance is the highest in wasteland and built-up areas land use/land cover categories. 
Publisher:
 Theoretical And Applied Climatology
Publication Type:
 Journal
Publication Title:
 Sensitivity Of Different Physics Schemes In The WRF Model During A West African Monsoon Regime
Publication Authors:
 Imoleayo E. Gbode & Jimy Dudhia & Kehinde O. Ogunjobi & Vincent O. Ajayi
Year Published:
 2017
Abstract:
A 2-month (August–September) regime of the year 2007 West African monsoon (WAM) was simulated with 27 physics combinations using the Weather Research and Forecasting model at 20-km horizontal grid. The objective is to examine WAM sensitivity to parameterization of microphysical, convective, and boundary layer processes for long-term simulation. The model precipitation was evaluated against the TRMM, CMORPH, and GPCP satellite rainfall products. The surface temperature was compared against the ERA-Interim, NCEP, MERRA, and global surface air temperature, an ensemble of the three reanalysis datasets. Model skill score (MSS) computed from a synthesis of the normalized correlation coefficient, mean bias, and mean absolute error was used to rank the model performance. Results show the model adequately simulates the diurnal cycles of surface temperature than precipitation, as well as the westward propagation of intense precipitation associated with the African easterly waves. The new Grell-Freitas (nGF) cumulus parameterization scheme (CPS) outperforms its predecessor especially when combined with the Mellor-Yamada-Nakanishi-Niino 2.5 (MYNN) planetary boundary layer scheme. The new simplified Arakawa-Schubert (nSAS) and Tiedtke CPSs produced better simulation of precipitation and surface temperature, respectively. The simulation of observed peak of diurnal precipitation in nSAS and nGF highlights success made towards a more realistic representation of convective processes by the schemes. Goddard microphysics and MYNN performed better for both variables. Based on the MSS, some relatively good and poorly performing combinations for precipitation and surface temperature were identified. The optimal combinations are however not separated in a statistically significant way and, thus, could be used for longterm simulation of WAM. 
Publisher:
 Nigerian Meteorological Society
Publication Type:
 Conferenceproceeding
Publication Title:
 Diagnostic Evaluation Of Precipitation Over West Africa Using Three Of The CORDEX-Africa Simulations
Publication Authors:
 Akintomide Afolayan Akinsanola, Ajayi Vincent, Elijah Adefisan,Kehinde Olufunso Ogunjobi
Year Published:
 2014
Abstract:
The study evaluates the ability of three Regional Climate model (RCMs) used in the Coordinated Regional climate Downscaling Experiment (CORDEX) activity driven by the same initial and boundary conditions (ERA-Interim) in simulating the characteristics of rainfall pattern over West Africa from 1998-2008. The seasonal climatology, annual rainfall cycles, interannual variability and the wind fields of RCMs output have been assessed over three homogenous sub-regions against ground observed data of 81 meteorological stations in West Africa and TRMM observational dataset. Furthermore, the study assessed the ability of the RCMs in simulating the El Nino and La Nina events. Result shows that all the RCMs simulate the main features of the rainfall climatology and associated dynamics over the three sub-regions (Guinea coast, Savannah and Sahel) of West Africa. Furthermore, analysis shows significant biases in individual models depending on sub-region and season. In general, the study shows that the three CORDEX RCMs simulate West Africa rainfall and extreme events adequately and can therefore be used for the assessment of future climate projections for the region taking into consideration the degree of biasness. 
Publisher:
 Access Internationa Journals
Publication Type:
 Journal
Publication Title:
 Assessing The Impacts Of Climate Variability On Crop Yield Over Sudano-Sahelian Zone In Nigeria
Publication Authors:
 Folorunso Mathew Akinseye, Ajayi Vincent, Titilayo O.Oladitan
Year Published:
 2013
Abstract:
Crop production in Sudano-Sahelian part of Nigeria is highly vulnerable to various challenges of climate variability, land degradation and desertification. This study investigates the impacts of climatic variability on major cereals crop (Maize, Millet and Sorghum) using Stepwise Multiple Regression Analysis (SMRA) as an index for the assessment. The crop-yield data was correlated with climate parameters. Parameters with significant relationship where retained while parameters that correlates weakly were discarded. The parameters considered were rainfall, temperatures (T_max; T_min), relative humidity (RH), sunshine duration (SS) and crop yield .The retained parameters were regressed to create crop-yield prediction model. The variability indices (z-value) were also employed in the study and it establishes the impacts of climate that are significant to crop-yield during growing season. The result shows that crops suffered low yield output during the year 1980's toward the early 1990's (reflected as negative anomalies) due to unfavourable climatic conditions before a significant recovery afterwards. However, the predictive model generated for the crops were significant at ? ? 0.05 (p-value). It was also observed crop yield are sensitive to June and September rainfall as well as daily Sunshine duration (SS) during the growing season. It was also observed that the predictor variables used in the study accounts for 60% of the crop-yield considered. This implies that climate is a major determinant for the yield of these crops as reflected by their total contribution. 
Publisher:
 International Journal Of Remote Sensing
Publication Type:
 Journal
Publication Title:
 A Long-term Record Of Aerosol Index From TOMS Observations And Horizontal Visibility In Sub-Saharan West Africa
Publication Authors:
 Kehinde Olufunso Ogunjobi, Ayodeji Oluleye, Ajayi Vincent
Year Published:
 2012
Abstract:
Aerosol index (AI) observations from the Total Ozone Mapping Spectrometers (TOMS) on board the Nimbus-7 (1979–1992) and Earth Probe (1997–2004) satellites are used to investigate the annual and seasonal variations of dust haze in Sahelian West Africa. Eight synoptic stations, namely Port Harcourt (PHA), Lagos, Ilorin, Makurdi, Minna, Yola, Maiduguri and Kano, representing the four major climatic zones (tropical rainforest and Guinea, Sudan and Sahel savannahs) of Nigeria were considered in this study. Twenty-nine years (1979–2007) of horizontal visibility data are also analysed in order to investigate the effect of dust haze on visibility in the stations under study. Results show that there are general decreasing trends in the visibility with corresponding increases in TOMS AI trends in all the climatic zones of Nigeria. This clearly suggests that there had been an increase in the integrated column dust aerosols over the years, especially during the harmattan dusty months. The average visibility was highest in Ilorin (11363.2 ± 1644.4 m) and the lowest in Maiduguri (9017.9 ± 1021.3 m) when the dust-prone months of November to March of the following year were considered. Logarithmic equations with inverse relationships are developed between TOMS AI and horizontal visibility for each station with correspondingly high coefficients of determination (R ) in all the locations. It is concluded that TOMS AI can reasonably be used to reproduce visibility measurement in sub-Saharan West Africa where sparse visibility data are available for meteorological uses. 
Publisher:
 Global Journals Inc. (USA)
Publication Type:
 Journal
Publication Title:
 Multiyear Analysis Of Ground-Based Sunphotometer (AERONET) Aerosol Optical Properties And Its Comparison With Satellite Observations Over West Africa
Publication Authors:
 Ayodeji Oluleye, Kehinde Olufunso Ogunjobi, A. Bernard, Akintomide Afolayan Akinsanola
Year Published:
 2012
Abstract:
The Sahelian West Africa (Long 20W:20E, Lat 0:30N) by its climatological and geographical conditions is a key region for the characterization of global atmospheric aerosol optical properties. This study evaluates the spatial and temporal variation of the Aerosol Optical Depth (AOD440nm), aerosol particle size characterization (Angstrom exponent (?440-675nm) at four locations (Agoufou, Banizoumbou, Cape Verde and Ilorin) over a period of January 2005 to December 2009. Results of the day-today AOD440nm variations as well as the seasonal and annual variations are presented in order to establish the aerosol climatology in the region. We compared satellite derived data of Total Ozone Mapping Spectrometer-Aerosol Index (TOMS-AI), MODIS (Terra and Aqua) with those of ground-based Sunphotometer AERONET measurements. In general, there exits good relationship between MODIS (Terra and Aqua) and the ground-based AERONET measurements with correlation coefficients, R2 › 0.8 reported in all stations. However low coefficients (as low as 0.40) were obtained in all the stations for regressions between TOMS AI and ground-based Sunphotometer AERONET data. Abstract-The Sahelian West Africa (Long 20W:20E, Lat 0:30N) by its climatological and geographical conditions is a key region for the characterization of global atmospheric aerosol optical properties. This study evaluates the spatial and temporal variation of the Aerosol Optical Depth (AOD 440nm), aerosol particle size characterization (Angstrom exponent (? 440-675nm) at four locations (Agoufou, Banizoumbou, Cape Verde and Ilorin) over a period of January 2005 to December 2009. Results of the day-today AOD 440nm variations as well as the seasonal and annual variations are presented in order to establish the aerosol climatology in the region. We compared satellite derived data of Total Ozone Mapping Spectrometer-Aerosol Index (TOMS-AI), MODIS (Terra and Aqua) with those of ground-based Sunphotometer AERONET measurements. In general, there exits good relationship between MODIS (Terra and Aqua) and the ground-based AERONET measurements with correlation coefficients, R 2 › 0.8 reported in all stations. However low coefficients (as low as 0.40) were obtained in all the stations for regressions between TOMS AI and ground-based Sunphotometer AERONET data.