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Item Temperature variations and soil thermal properties at the Nigeria mesoscale experiment site, Ibadan, Nigeria(ECRTD-UK, 2019) Nwaokoro, E.; Nymphas, E. F.Soil temperature has been observed to depend on a number of factors, which also determine the surface temperature. In this study, soil temperature at the Nigeria Mesoscale Experiment (NIMEX) site, Ibadan (7.4398° N, 3.8930° E) was investigated and the soil thermal properties were estimated for the period of March, 2006 to January, 2007 using Kersten model. The rainy seasons had increased the soil moisture content and soil thermal properties while the dry seasons had low soil moisture content and soil thermal properties. The maximum temperature of 32.10° C at the 30cm depth was measured in November 2006 during the dry season and the minimum temperature 26.80° C was measured at 5cm depth in September 2016 during the wet/rainy season. Soil moisture, thermal conductivity, thermal diffusivity and volumetric heat capacity had their maximum value of 20.52m3m-3, 1.006 Wm-1K-1, 1.07*10-8m2s-1 and 0.91*108Jm- 3K-1 in September 2006 respectively. The minimum values for soil moisture, thermal conductivity and volumetric heat capacity occurred in January, 2007 with values of 15.75 m3m-3, 0.90 Wm-1K-1 and 0.91*108Jm-3K-1 respectively, and the minimum value of 0.85*10-8m2s-1 for thermal diffusivity occurred in July 2006.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 Characteristics of worst hour rainfall rate for radio wave propagation modelling in Nigeria(springer, 2019) Osita I.; Nymphas E.F.Radio waves especially at the millimeter-wave band are known to be attenuated by rain. Radio engineers and designers need to be able to predict the time of the day when radio signal will be attenuated so as to provide measures to mitigate this effect. This is achieved by characterizing the rainfall intensity for a particular region of interest into worst month and worst hour of the day. This paper characterized rainfall in Nigeria into worst year, worst month, and worst hour. It is shown that for the period of study, 2008 and 2009 are the worst years, while September is the most frequent worst month in most of the stations. The evening time (LT) is the worst hours of the day in virtually all the stations.Item Design and construction of a low cost air temperature and pressure data logging equipment using raspberry pi(2018) Otunla T.A.; Ukaegbu S.C.; Nympas E.F.This paper describes the design and construction of a hnv cost air temperature and pressure data-logging equipment using raspberry pi. The equipment is designed to perform automatic measurements of air temperature and atmospheric pressure and sendthe measured values to the Raspberry pi for togging. Raspberry pi logs the data on a comma-separated value (CSV) file format as wed as store the data for records. The equipment was tested and validated against a standard atmospheric weather observatory. The results indicated a good agreement with coefficient of determination of R~ = 0.83, slope = 0.7, mean bias error, MBE—0.77'C, and root mean squared error R\1SE=I.53"C. The equipment can be further improved to accommodate more sensors and provide data from remote locations.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 sporadic-e (es) layer at two equatorial stations: fortaleza (3os, 38ow) and Ilorin (8.5on, 4.5oe)(2014) Nymphas, E.F; Adeyemi, T.A.The day time variability of sporadic-E (Es) layer at Fortaleza (3oS, 38oW) and Ilorin (8.5oN, 4.5oE) during the solstice and equinox periods have been investigated using hourly daily Digisonde ionograms. The result show that during the equinox period, the critical frequency (foEs) of the Es-layer at Fortaleza dropped to minimum values before rising to its first peack values by 0900 hrs LT and 1000 hrs LT in March and September respectively. On the other hand, a continuous rise in the value offEs from sunrise till the first peack values of 6.0MHz by 0800 hrs LT and 5.5MHz by 0700 hrs LT was observed during the June and December solstices respectively. At Ilorin, the fEs reached its first peack values of 5.5MHz by 1200 hrs LT and 6.0MHz by 1000 hrs LT during the March and September equinoxes respectively. A double peack of about 5.4MHz by 0800 hrs LT and 6.5MHz by 1300 hrs LT was observed during the June Solstice as compared to the single peack of about 7.00MHz during the December solstice. The height (hmEs) of Es was lower at Fortaleza than at Ilorin for all the seasons (with a difference of between 2 and 4 km, depending on the month). For all the seasons and months investigated, the E-layer was never observed earlier than 0900 hrs LT at Fortaleza. At Ilorin, the E-layer was formed right from sun rise with frequencies lower than at Fortaleza. These results comfirm the latitudinal variation of the sporadic-E layer at the equatorial region. It also showed that the E-layer is formed earlier in Ilorin than at Fortaleza with a time lag of about 3 hours.Item Estimation of surface energy fluxes from bare ground in a tropical station using priestleytaylor method(2013) Adeniyi, M.O.; Nymphas, E. F.This investigation was designed to test the performance of Priestley Taylor method in the partitioning of the available energy into sensible and latent heat fluxes in a tropical site. Compared to eddy covariance measured fluxes, the conventional Priestley Taylor constant (aPT) of 1.25 gave low coefficient of determination and high bias error for both sensible and latent heat fluxes. It overestimated latent heat flux in the noon and afternoon but underestimated sensible heat flux. The bias error reduced and the coefficient of determination increased for sensible heat flux when aPT value was reduced to 1.0. The bias error for latent heat also reduced but the coefficient of determination did not change with the reduction in aPT value. The root mean square error reduced with the reduction in the aPT value. Compared to measured fluxes, coefficient of determination of sensible heat flux ranged from 0.82 to 0.90 while that of latent heat flux ranged from 0.78 to 0.9. Priestley Taylor method is recommended for partitioning of available energy into its component sensible and latent heat fluxes.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 Validation of analytical algorithms for the estimation of soil thermal properties using de Vries model(2012) Adeniyi, M.O.; Oshunsanya S.O.; Nymphas, E. F.Soil thermal conductivity, and diffusivity together with the damping depth of soil temperature computed using Amplitude decay, Phase shift, Harmonic (amplitude based and phase based), Arctangent, Logarithmic and conduction-convection algorithms were compared with those obtained from de Vries model. The amplitude decay algorithm yielded the most reliable values of the soil thermal properties of all the estimation methods with mean absolute error (MAE), root mean squared error (RMSE) and relative maximum error (RME) of 0.04, 0.05 and 5.63% respectively for soil thermal conductivity. Harmonic algorithm (using the amplitude of the first 4 harmonics) gave values of the soil thermal properties next to the amplitude decay algorithm with MAE, RMSE and RME values 0.41, 0.44 and 47.84% respectively for soil thermal conductivity. Higher error values were associated with the other algorithms. The Arctangent algorithm gave the most deviated values of soil thermal properties with RME of 156.83% for soil thermal conductivity. For soil moisture content between 0.168 and 0.189 (> critical soil moisture content) the values of the soil thermal properties of the loamy sand decreased with increasing soil moisture, while they increased with increasing soil aeration.