Browsing by Author "Oladiran, E.O."

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Behavior of multiple lightning dischargers under a tropical thundercloud
(2010) Nymphas. E.F.; Adeniyi, M.O.; Oladiran, E.O.
Lightning discharges on ground depend on the electrostatic charges, nature of vegetation, topography and dynamics of the turbulent layer. In designing lightning protectors, one major consideration is the highest point in the surrounding that lightning is directed. The effects of ambient dischargers on lightning protectors were investigated. to determine both the discharge behavior and performance. The starting potential of the discharger configuration increased with clearance of tip of the central discharger from surrounding dischargers, instead of increasing with the average spacing between dischargers. The point of strike of lightning discharge depended on the line of least stress rather than the height clearance from the cloud: which determined the charge structure and dynamics of the cloud particulates
Food security measures during uncertain climatic conditions in Nigeria
(2009) Adeniyi M.O.; Ogunsola O.E.; Nymphas E.F; Oladiran, E.O.
Food security is a function of a few variables such as technological input, capital, government policies and environmental (climate) factors. Good control of all these dependent variables except the last, and the thorough understanding of the last can take the nation to food security level. Possible ways of controlling the first three variables (technological input, capital, government policies) are suggested. To have thorough understanding of the climate factors, time series analysis of climate variables precisely temperature and precipitation data in twelve locations covering the various climatic belts of Nigeria were carried out. Nigeria rainfall has a usual zonal pattern and the vast majority of precipitation falls within a well-defined period. The coastal stations received more rainfall than the inland locations. The northern locations received less rainfall than southern locations. The onset period for the northern stations is May/June while the cessation period is September/October. The southern stations have April as their onset month while October is their cessation month. The southern stations have two peaks of rainfall in June/July and September. A period when rainfall ceases within the wet season exists in the south, and is referred to as ‘August break’. The northern stations have only one peak, which is in August. Annual trend of precipitation is positive in most of the southern stations while it is negative in most northern stations. At the ninety-nine percent confidence limits, all the stations have mean annual rainfall close to or within the limits except during El Nino Southern Oscillation (ENSO) years. Harmonic analysis reveals 3 to 4 and 7-8 years inter-annual cycle of precipitation which correspond to the warm and cold ENSO cycle. Temperature has a bimodal variation through the twelve months in a year. The two maxima occur in March/April/May and October/November while the minimum is in July/August. Annual temperature trend is positive (small slope) in some stations while it is negative in some not necessarily depending on the position.
Impact of the total solar eclipse of 29 March 2006 on the surface energy fluxes at Ibadan,Nigeria
(2012) Nymphas,E.F.; Otunla,T.A.; Adeniyi,M.O.; Oladiran, E.O.
This paper document the impact of the total solar eclipse (97.4%) of 29 March 2006 on the surface energy fluxes at Ibadan, Nigeria (longitude4.561E, latitude7.551N), a tropical location. The surface energy (determined by the BREB method) was found to be grossly affected by the eclipse. The latent heat and net radiation (Rn) lagged the sensible heat by 11 min in totality. The sensible heat lagged the latent heat and Rn by 6 min before it start to increase after the totality phase of the eclipse while global radiation (Rg) lagged Rn by 7 min. The sensible heat reversed sign reaching a value of _1.02 Wm_2 during the total phase of the eclipse while the latent heat dropped by 89.7%. All the radiation fluxes (global radiation, Rg, net radiation Rn, temperature and soil heat flux) measured during the eclipse event were significantly affected by the sudden ‘cutoff’of the solar irradiation.There was a 95% decrease in Rg, while Rn dropped from 354.3Wm_2 to _11.7 Wm_2.
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.
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%.