FACULTY OF SCIENCE
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Item An artificial neural network estimation of global solar radiation at Ibadan, Nigeria using meteorological data(2020) Nymphas, E.F.; Udomboso, C.G.This paper estimates global solar radiation (Rs) from routinely measured meteorological parameters in the city of Ibadan, Nigeria, using artificial neural network method. Six combinations were used to estimate Rs namely (i) daily mean air temperature (T) and day of the year as inputs and global solar radiation as output, ((ii) daily mean relative humidity (RH) and day of the year as inputs and Rs as output (iii) daily mean T, daily mean RH and day of the year as inputs and Rs as output (iv) daily mean minimum relative humidity (RHmin) and day of the year as inputs and Rs as output, (v) daily mean minimum temperature (Tmin), daily RHmin and day of the year as inputs and Rs as output (vi) daily mean maximum temperature (Tmax), daily mean Tmin, daily mean RHmin, daily maximum relative humidity (RHmax) and day of the year as inputs and Rs as output. The neural network was trained with 3653 measured data between 1995 and 2004 and tested with data for 731 days between 2003 and 2004. The data for testing the neural network were not used for the training. The results obtained showed that the combination of RHmin, RHmax and day of the year gave the best estimate of Rs with MSE of 3.4124. This is followed by RHmin and day of the year with MSE of 3.4424. Daily mean air temperature and day of the year could not mimic the measured Rs; it gave MSE of 5.3345. It is concluded that Rs can be estimated for locations where only temperature and relative humidity data are available.Item Simulating the influence of greenhouse gases on the climate of West Africa(2019) Adeniyi, M.O.; Nymphas, E.F.; Oladiran, E.O.The response of climate to perturbations in GHGs is location dependent. Six experiments: control (CTRL); double CH4; double CO2; double N2O; halved CFC11 and halved CFC12 were carried out to reveal the local area response to different GHGs levels in the atmosphere over West Africa. Double CH4, CO2 and N2O generally induce wetness but they also induce localized dryness at the hilly and mountainous areas of SW Ghana, Central Nigeria, Northern Cameroon and South-eastern Central African Republic. Increase in ground temperature is induced by double GHGs with intensified warming at the north by double CO2. However, patches of cooling are induced at the north. Changes in specific humidity induced by double CO2, CH4 and N2O are similar. Intensified tropical easterly jet is induced by double GHGs. A dipole anomaly of wind with positive at the lower latitude and negative at higher latitude is induced at the northern part of West Africa. Significant reduction in cloud water content is induced from 900 to 400 hPa and 0 and 15oN.Item Meteorological comfort indices to assess extreme warmness in southwest, Nigeria(2019) Aluko, T.O; Nymphas, E.F.; Bolaji, O.A.; Odubanjo, O.F.2015, 2016 and 2017 have been confirmed the three warmest years on record and the degree of warming during these three years has been exceptional. Extremes of heat and cold environmental conditions have been known to be very detrimental to the health and comfort of humans. The severity of these adverse effects is often local and varies from one place to another though they are happening on a global scale therefore Temperature variation, Heat Index (HI) temperature and Dew Point Temperature (DPT) ( Meteorological comfort indices) were used to assess the effect of this condition in southwest, Nigeria. Air temperature and Humidity data were collected from meteorological stations situated in the southwestern states selected for study and was processed using the rule of Thumb for DPT calculations as expressed by Lawrence (2005) and Steadman (1979) formula simplified by Rothfusz’ model (1990) for HI temperature. The data analysis was done using Microsoft Excel Package and Statistical Package for the Social Sciences (SPSS), the following results were obtained: Elevation may affect temperature yet during extreme warmness other factors can have a greater influence on temperature and meteorological comfort indices used to assess extreme warmness in southwest Nigeria from this study showed greater impacts thus: Heat Index Temperature has highest values in Lagos State, while Dew Point Temperature have highest values in Ogun state. None of these extreme warmness measuring variables seem to be solely in favour of state Location in terms of coordinates and elevation; this suggests more anthropogenic influence forming the characteristics of the states to geographic locations of the states however, between the start year of extreme warmness (2015) and 2017, HI temperature showed a significant increase while average DPT did not really change during the period of extreme warmness.Item A statistical approach to estimate wind speed distribution in ibadan, nigeria(2016) Rauff, K.O; Nymphas, E.F.In this paper, the wind energy potential in Ibadan is statistically analyzed using daily wind speed data for 10 years (1995-2004) obtained from the International Institute of Tropical Agriculture (IITA) and 1 year (2006) obtained from Nigeria Micro-scale Experimental (NIMEX) Ibadan,Nigeria. The statistical wind data set was analyzed using Weibull distributions in order to investigate the Weibull shape and scale parameters. The daily, monthly, seasonal, and yearly wind speed probability density distributions were modeled using Weibull Distribution Function. The measured annual mean wind speed was found to be 0.76 m/s and the total extractable wind power has been estimated as 0.33 kW at IITA while the annual mean wind speed ranged between 0.74 m/s, 1.02 m/s, 1.16 m/s and 1.34 m/s at (3 m, 6 m, 12 m and 15 m) respectively at NIMEX. The maximum extractable annual wind power density value of 0.90W /m2 for the whole year at IITA and 5.61W / m2 at the highest height of 15 m at NIMEX indicated that, Ibadan can be classified as a low wind energy region and it belongs to the wind power class 1, since the density is less than 100W /m2 . It is concluded that at both sites, the highest wind speed that prevailed in Ibadan is March and the location can be explored for wind power.Item Variability of the critical frequency of the f2 layer, fof2 in west africa using ionosonde stations at ouagadougou and dakar(2012) Salami, O.R.; Nymphas, E.F.The critical frequency of the F2 layer of the ionosphere, foF2 is responsible for various effects on radio communication such as refraction, scintillation, absorption, error in Global Positioning System (GPS), jitter and phase delay. The variations of the critical frequency of the F2 layer at two different locations over West Africa were studied using ionosonde data for a solar cycle (1979 to 1989) at low, moderate and high solar activity, 1986, 1983 and 1989, respectively. The ionosonde stations are Dakar in Senegal (15°N, 17°W) and Ouagadougou in Burkina Faso (12°N, 1,8°W). The investigation of critical frequency of the F2 layer, foF2 using Relative Standard Deviation (RSD) revealed the spread and the occurrence of foF2. The results obtained in this study are proposed as equatorial input values for the development of a Variability Model for the International Reference Ionosphere.Item Micrometeorological measurements in Nigeria during the total solar eclipse of 29 March, 2006(2009) Nymphas, E.F.; Adeniyi, M,O.; Ayoola, M.A.; Oladiran, E.O.The total solar eclipse of 29 March, 2006 which was visible at Ibadan (7.55°N, 4.56°E), south-western Nigeria was utilized to document atmospheric surface-layer effects of the eclipse for the first time in Nigeria. The meteorological parameters measured are global radiation, net radiation, wind speed (at different heights), atmospheric pressure and soil temperature (5,10 and 30cm), moisture and heat flux and rainfall. The results revealed remarkable dynamic atmospheric effects. The observations showed that the incoming solar radiation, net radiation and air temperature were significantly affected. There was an upsurge of wind speed just before the first contact of the eclipse followed by a very sharp decrease in wind speed due to the cooling and stabilization of the atmospheric boundary layer. The atmospheric pressure lags the eclipse maximum by 1 h 30 min, while the soil temperature at 5 and 10cm remain constant during the maximum phase of the eclipse.Item The nigerian micrometeorological experiment (nimex-1): an overview(2004) Jegede, O.O.; Mauder, M.; Okogbue, E.C.; Foken, T.; Balogun, E.E.; Adedokun, J.A.; Oladiran, E.O.; Omotosho, J.A.; Balogun, A.A.; Oladosu, O.R.; Sunmonu, L.A.; Ayoola, M.A.; Aregbesola , T.O.; Ogolo, E.O.; Nymphas, E.F.; Adeniyi, M.O.; Olatona, G.L.; Ladipo, K.O.; Ohamobi, S.I.; Gbobaniyi, E.O.; Akinlade, G.The first phase of the Nigerian Micrometeorological Experiment (NIMEX-1) was concluded between 15 February and 10 March 2004, at an agricultural site within the campus of Obafemi Awolowo University in Ile-Ife, Nigeria (7°33’N, 4°33’E). The multi-institutional project was aimed at determining the surface energy balance of a tropical wet and dry location in West Africa. The field observations made fell within a transition from the dry to wet season in the area, and as such, the surface conditions varied in extremes. An integrated measurement system comprising of various micrometeorological sensors was deployed to record the mean and turbulence parameters in the surface layers separately. A number of methodologies viz: the eddy covariance (EC), Bowen ratio energy balance (BREB), and modified Bowen ratio (MBR) systems, used to determine magnitudes of the surface fluxes; sensible and latent heats, were compared. Generally, there is a consistency of their diurnal trends but the BREB method overestimated the surface fluxes up to about 30%. The radiation balance indicated that the incoming shortwave is dominant during daytime and is mainly responsible for the surface forcings. The nonclosure of the energy balance obtained at the surface, typically, was less than 25%.Item Soil Thermal Properties at Nimex-1 site(2004) Oladosu, O.R.; Ayoola, M.A.; Nymphas, E.F.Item Transformer and transmission of power(Ibadan university press, 2013) Nymphas, E.F.