Scholarly works
Permanent URI for this collectionhttps://repository.ui.edu.ng/handle/123456789/420
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Item 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.Item Analysis of data on net longwave, shortwave, and global radiation during a transition period in a tropical station in southwestern Nigeria(2009) Ogolo, E.O. Ph.D,; Falodun,S.E.; Oluyanmo,S.S.; Nymphas, E.This paper examines the distribution of the surface radiation balance components measured during the Nigerian Micrometeorological Experiment (NIMEX-1), a field study conducted to measure surface heat fluxes in the boundary layer during the transition period which marks the end of dry season and the onset of wet season (February 15 and March 10, 2004) in the southwestern part of Nigeria. Regression equations were obtained using the daily average values and hourly mean values between net shortwave and net longwave radiation, respectively, with the global radiation. Higher correlations with low standard error of measurement were obtained for daily mean values than the hourly mean. It was also observed that the peak values of each type of radiation during the period occurred, on average, two hours after noon when it was expected to occur.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 characteristics of positive ground discharges of tropical thunderstorms at Ibadan, Nigeria(2006) Oladiran. E.O.; Nymphas, F.F.; Akpan U. F.; Israelsson, SPositive ground lightning discharges were continuously recorded over a period of three years at Ibadan to supplement earlier composite records from 1987 by adapting the earlier design of Oladiran. et al (1988a) using the shape of the radiation field signatures and the frequency components of positive discharges (Oladiran and Israelsson. 1990). We recorded 92% discrimination between negative and positive ground flashes. The positive ground flashes were recorded at VLF and 17.3kHz, 3Db attenuation and yielded an average 13 and 11.6% ratios for (+CG)/(-CG) respectively. Compared to our results of 1988, the flash-rate characteristics for positive ground flashes are not significantly different from those of negative ground flashes and it does not show any seasonal preference. This leads to the conclusion that the occurrence of positive and negative ground flashes depends only on the cloud charge structure. Its dynamics and the ground conditions.Item Lightning signature as an index for the determination of the beginning of the Planting season in Nigeria(2004) Nymphas, F..F.; Adeniyi. M.O.; Ogolo, E.O.; Oladiran, L.O.The discharge characteristics of a Franklin rod and a compound discharger with an insolated central point and surrounding points (a modified Franklin rod) has been investigated in the Laboratory and in the open atmosphere with a view to determine their effectiveness as lightning protectors. Analysis of the data showed that the compound discharger is about two and half times more effective as lightning protectors as compared to a typical Franklin rod with multiple ends. An aperiodic relationship between in (At V.. :/AVf) and m (dn/dt) has been observed instead of the speculated linear relationship. Investigation of the environment effects reveals that point- discharge current measurement from a point in a built discharge is an under-estimate.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 A review of the bulk layer pollutant transfer over Nigeria during the harmattan season(2007) Oladiran, E. O.,; Nymphas, F. F.A review of the results of the bulk characteristics of the harmattan dust is presented to facilitate ease of reference and regional comparison where similar local effects exist. The meteorological interconnections are dealt with. The transport properties are presented, and are found to agree with the plume model for cascaded continuous sources on a 1km x 1km gnd point system. The wind profile is found to be consistent with turbulent electrode model of Willet.Item Soil Thermal Properties at Nimex-1 site(2004) Oladosu, O.R.; Ayoola, M.A.; Nymphas, E.F.Item Detection of seismic ULF geo-electrical potential variations as tremor precursors prior to quarry blasts(2009-05) Adetoyinbo, A. A.; Popoola, O. l.; Hammed, O. S.; Sumonu, L. A.A seismic ultra low frequency geo-electrical signal recording instrument was set up in three different quarry sites in the south-western part of Nigeria. This research was embarked upon to detect geo- seismic electrical signals produced from the brittle upper crust during rock loading and fracture as a simulated earthquake precursor. The seismic electromagnetic signals emitting from the interior earth in analogical pattern and detected at the earth surface through the signal detectors were transmitted to a conditioning circuit which not only protected the recording instruments from transients caused by ionospheric disturbances but also attenuated the 50 or 60 Hertz frequency caused by high voltage power transmission lines. The spectral analysis of the ULF signals with sampling of 48 KHz recorded during rock loading and fracture in each of the stations revealed that the amplitudes of the signals decrease with increasing frequency. The geo-electrical potential signals associated with ULF waves were varying during deformation stages of crustal layers of rocks. These signals were recorded a few seconds before and after fracture of the rocks as systematic precursors to the main tremors observed in each of the stations and felt five (5) kilometers away.Item Assessment of groundwater quality in unconsolidated sedimentary coastal aquifer in Lagos State, Nigeria(Academic Journals, 2009-04) Adebo, B. A; Adetoyinbo, A. A.This study assesses the quality of ground water from nine different borehole locations in Lagos State, Nigeria. Borehole water samples were carefully collected for physico - chemical analyses. Calcium, magnesium, iron, zinc, copper, manganese, aluminium, and silver, Nitrate, phosphate, fluoride, chloride, pH, conductivity, total dissolved solid, total suspended solid, hardness, summation of ions as well as the temperature and colour were assessed among the entire samples collected. The results show that: temperature ranges from 26.6 - 27.8°C, pH (7.27), average conductivity (462.2 ps/cm), TDS (204.73 mg/l), Total hardness (18.48 - 297.70 mg/l) and Chloride concentration (343.3 mg/l). However, a high value of chloride, 343.3 mg/l, was recorded in one of the water sample collected but, this is higher and above the limit of WHO guidelines of portable water (250 mg/i). This may be due to the proximity of the area where the sample was collected to the sea. Five samples of the water are is soft, that is, hardness was within a range of 0 - 75 mg/l recommended for safe drinking water, one is moderately hard while three samples are hard. Also, the presence of metals such as zinc, manganese, sodium, copper and magnesium were also observed. Results show that not all the water samples are safe for drinking purposes.
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