Values Of Refractivity Research Articles

Assessment of Tropospheric Radio Refractivity and its Variation with Climatic Variables in the Guinea Savannah Region of Nigeria

In studies involving terrestrial atmospheric electromagnetic propagation, such as point-to-point microwave communication, terrestrial radio, television radio, television broadcast, and mobile communication systems, radio refractivity—the bending of a radio signal as it propagates through media—is crucial. In this study, the seasonal tropospheric radio refractivity was estimated and its variations with other meteorological parameters and refractive index were investigated using the measured monthly climatic data of atmospheric pressure, relative humidity, and temperature obtained from the National Aeronautic and Space Administration (NASA) for Makurdi and Ibadan during the period of forty-two (42) years (1981 to 2022). The refractivity gradiant, effective earth radius, and percentage contribution of the dry and wet term radio refractivity were examined. The findings indicated that for the two locations, high values of radio refractivity were observed during the rainy season and low values during the dry season. The maximum and minimum average values of radio refractivity observed for Makurdi and Ibadan during the rainy and dry seasons are, respectively, 380.0641 N-units in the month of May, 331.9776 N-units in January, and 379.9479 N-units in the month of May, 352.2143 N-units in January. The dry term (Ndry) contributes 70.8764 % and 69.4504 % to the total value of radio refractivity, while the wet term (Nwet) contributes to the major variation with 29.1236 % and 30.5496 % for Makurdi and Ibadan, respectively. The study areas under investigation yielded average refractivity gradients of -43.8583 and -43.1480 N-units/km. Additionally, the average effective earth radius (k – factor) for Makurdi and Ibadan was found to be 1.3876 and 1.3790, respectively. These values align with the conditions of super refraction propagation.

INVESTIGATION OF TROPOSPHERIC RADIO REFRACTIVITY AND OTHER RELEVANT PARAMETERS USING METEOROLOGICAL VARIABLES OVER BAUCHI, NIGERIA

The National Aeronautics and Space Administration (NASA) archives were used in this work to obtain the measured monthly average daily temperature, relative humidity, and atmospheric pressure over a 41-years period (1981–2021) for Bauchi (latitude , longitude ) to calculate the monthly tropospheric radio refractivity. The site is located in Nigeria's midland climate zone. We also looked into the variation with other factors, the refractivity gradient, and the percentage contribution of the dry term (Ndry) and wet term (Nwet) radio refractivity. The results showed that during the rainy and dry seasons, respectively, the months of August and February had the highest and lowest average values of radio refractivity, measuring 355.032 (N-units) and 273.255 (N-units), respectively. This suggests that radio refractivity is higher during the rainy season than it is during the dry season. The wet term contributes to the significant fluctuation in radio refractivity values, while the dry term makes up 77.60 % of the total value. The average refractivity gradient estimate was found to be – 40.854 N – units/km suggesting super-refraction propagation for Bauchi indicating that electromagnetic waves are often bent downward towards the earth when the super refraction condition occurs.

A comprehensive investigation of Bi2O3 on the physical, structural, optical, and electrical properties of K2O.ZnO.V2O5.B2O3 glasses

The multi-component glass system has a composition of 10K2O–10ZnO–55 B2O3–(25–x)V2O5–xBi2O3 (x = 4, 5, 7.5, 9, 10 mol%) are synthesized by the melt-quenching method. Using X-ray diffraction examination, the amorphous phase in the material was confirmed. The physical characteristics of the produced compositions are examined using density (D) and molar volume (Vm). Calculations of physical properties showed that adding Bi2O3 from 4 to 10 mol% increased the glass density from 2.7878 to 3.3617 g cm−3 and decreased the molar volume from 40.4196 to 38.5895 cm3/mol. Studies of glass samples using the FTIR show bands of absorption for oxides in different structural groups. Octahedral [BiO6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\ ext{BiO}}}_{6}$$\\end{document}], [BO4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\ ext{BO}}}_{4}$$\\end{document}], and tetrahedral [BO3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\ ext{BO}}}_{3}$$\\end{document}] structural units are observed in the present glass matrices. The cutoff wavelength (λC\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\lambda }_{C}$$\\end{document}), and optical band gap energy were determined using UV absorption spectra. The increase in non-bridging oxygens can be linked to the decrease in optical band gap energy (Eopt\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${E}_{opt}$$\\end{document}) (direct and indirect) and the increase in cutoff wavelength with an increase in Bi2O3 content. This is attributed to the existence of bismuth ions and the creation of non-bridging oxygens. Besides that, the values of optical parameters, viz., optical electronegativity, refractive index, and molar refractivity, are calculated. The metallization criterion values are less than 1 and the glass samples exhibit an increased tendency towards metallization. Both the conductivity and the dielectric constant increase with the rise in Bi2O3 content, however, the dielectric loss and the impedance reduce. The behavior and values of conductivity for the studied glasses reveal the semiconducting properties of all glass samples. These results suggest that the produced glass samples may be employed as amorphous semiconductors in electronics and memory switching devices.

The Investigation of Surface Radio Refractivity Over Lokoja, Kogi State Nigeria

This research investigated the variation of Surface Radio Refractivity and its propagation effects on radio signals over Lokoja, Kogi State, Nigeria. The study used six years (2015-2020) of satellite data on temperature, pressure, relative humidity and rainfall at the surface (12 km) above ground level. The data retrieved were used to determine the monthly, seasonal, and annual Surface Radio Refractivity value for Lokoja Kogi State. Results show that high Surface Radio Refractivity values were recorded generally during the wet season months compared to the dry season months in all Six years (2015-2020). The average values of Surface Radio Refractivity 307.7407 (N-units) and 323.4674 (N-units) were obtained during the dry and wet season, respectively. The minimum surface radio refractivity values of 280.7245, 284.6583, 308.0021, 285.2304, 304.2521 and 285.9139 (N-units) were recorded for the years 2015, 2016, 2017, 2018, 2019, and 2020 respectively. On the other hand, the highest values of 330.8153, 331.8133, 330.3580, 330.9278, 332.4704, and 331.1316 (N-units) were recorded for the years 2015, 2016, 2017, 2018, 2019 and 2020, respectively. Higher values of Surface Radio Refractivity were recorded generally during the wet season compared to the dry season months in all years (2015-2020) in Lokoja, Kogi State. This implies higher radio signal attenuation due to Ns during the wet season compared to the dry season. The correlation coefficients between Surface Radio Refractivity Ns and temperature are -0.41, -0.51, -0.49, -0.48, -0.46, -0.50, pressure 0.07, -0.15, -0.28, -0.08, -0.11, -0.26, relative humidity 0.89, 0.84, 0.75, 0.84, 0.77, 0.83, and the amount of rainfall 0.76, 0.64, 0.73, 0.58, 0.51, 0.65 respectively in the year 2015, 2016, 2017, 2018, 2019, 2020. The overall findings of the work will be useful to radio engineers for properly planning a reliable power budget for terrestrial radio communication over Lokoja, Kogi State.

Seasonal and latitudinal variations of surface radio refractivity over Nigeria

Refractivity is a significant challenge of radio signal propagation. As it often distorts or leads to loss of signals. The seasonal and latitudinal variations of surface refractivity at three Nigerian tropospheric Observatory stations in Nigeria, namely Port-Harcourt, Lagos, and Makurdi, are presented in this paper. Values of monthly averages of pressure, temperature, relative humidity, and water vapour from the stations were used to compute surface refractivity at each station. The results show that the values of surface refractivity increase from the arid region in the north to the coastal area in the south. There was an increase in the values of surface radio refractivity from the minimum value of about 332.83 N-units at Makurdi station to a maximum value of 386.69 N-units at Lagos station. Seasonal variations are seen to be caused by weather conditions. The values of the surface refractivity increased significantly in the wet season and reduced in the dry season. It also shows that the values of surface radio refractivity are affected by the meteorological components mentioned above. The result of this study is needed for effective planning of good signal reception in these stations.

Impact of ZnO Modifier Concentration on TeO2 Glass Matrix for Optical and Gamma-Ray Shielding Capabilities.

This study carried out a comparison of the optical and gamma ray shielding features of TeO2 with and without ZnO modifier concentration. Incorporating ZnO into the TeO2 network reduces the indirect band gap from 3.515–3.481 eV. When ZnO is added, refractive indices, dielectric constants, and optical dielectric constants rise from 2.271–2.278, 5.156–5.191, and 4.156–4.191 accordingly. The transmission coefficient and reflection loss are in direct opposition to each other. With increasing ZnO concentration in the selected glasses, the values of molar refractivity and molar polarizability decrease from 18.767–15.018 cm3/mol and from 7.444 × 10−24–5.957 × 10−24 cm3, respectively, while the electronic polarizability rises from 8.244 × 1024–8.273 × 1024, correspondingly. As expected by the metallization values, the glass systems are non-metallic. The linear attenuation coefficients (LAC) of the studied glass samples ensue through enhancing the photon energy range 0.0395–0.3443 MeV. There is a very slow decrease in the LAC from an energy of 0.1218–0.3443 MeV, yet there is a sharp decrease from an energy of 0.0401–0.0459 MeV. According to the obtained values of numerous shielding parameters such as LAC, MAC, HVL, MFP, and Zeff sample, Zn30 has shown the best radiation shielding ability comprising other studied samples.

Study of ionic conduction, dielectric relaxation, optical and electrochemical properties of AgPO3/graphene glasses for magnesium battery applications

Developing suitable cathode material for alkali ion batteries is the most significant challenge facing commercialization. The effect of graphene nanoplatelets (GNP) on the physical and optical properties of AgPO3 glass is demonstrated. For the first time, AgPO3/Graphene glasses have been synthesized by melt-quenching method to assess the physical and the electrochemical performance as a cathode for a Magnesium ion battery. The complex impedance method determines bulk conductivity; the bulk conductivity increases with increasing temperature and graphene content. AgPO3_2 wt%GNP (sample 2) shows the optimum stoichiometric ratio with linear conductivity-temperature growth up to fast-ionic conductivity ∼ 1.79×10−2 (ohm. cm)−1 at 150 °C. The study of frequency dependence of both dielectric constant and dielectric loss have been explained based on ion hopping beside the ionic polarization mechanism. Optical properties such as the refractive index, optical energy gap, molar refractivity, molecular polarizability, dispersion, and oscillator energy of AgPO3 glass with different graphene nanoplatelets are investigated. The data reveal the lowest energy gap for the glass sample (AgPO3/2 wt%GNP). On the contrary, the values of refractive index, dispersion energy, molar refractivity and molecular polarizability are the highest for (AgPO3_2%wt%GNP) sample. The coin cell has been fabricated with the cell configuration Mg//electrolyte//AgPO3 and Mg//electrolyte//AgPO3_2 w%GNP. The cell with AgPO3_2 wt% GNP electrode has a high initial discharge capacity of ∼187 mAh/g compared with AgPO3 electrodes of ∼100 mAh/g.

STUDIES ON SURFACE RADIO REFRACTIVITY OVER SOME SELECTED CITIES IN NORTH-CENTRAL, NIGERIA

This research investigated the variations of surface radio refractivity and its propagation effects on radio signal over the cities of Abuja and Ilorin, Nigeria. Six years (2015-2020) satellite data of Temperature, Pressure and Humidity both at the surface (12m) and at 100 m AGL, were used for the study. The data retrieved were used to determine the monthly, seasonal and annual surface radio refractivity values for the locations. Results show that the values of surface radio refractivity (Ns) in Abuja was slightly lower than Ilorin with average values of 335.62 and 351.07 N-Units obtained for the six years respectively. Average values of Ns, obtained during the dry season months in Abuja and Ilorin were 299.40 and 321.03(N-units) respectively while average values of 360.24 and 368.21 (N-units) were obtained during the wet season months in Abuja and Ilorin respectively. Higher values of Ns, were recorded generally during wet compared to the dry seasons’ months in all the years and study locations. The implication of this is higher attenuation of radio signal due to Ns during wet compared to the dry seasons’ months and as well as in Ilorin compared to Abuja. Correlation coefficients of -0.53, 0.98 and 0.53 were determined between (Ns) and; temperature, humidity and pressure respectively in Abuja while -0.30, 0.97 and 0.34 were determined between Ns and; temperature, humidity and pressure respectively in Ilorin. The overall findings of this work will be useful to radio engineers for the proper planning of reliable power budget over the study areas.

Impact of replacement of B2O3 by TeO2 on the physical, optical and gamma ray shielding characteristics of Pb-free B2O3-TeO2-ZnO-Al2O3-Li2O-MgO glass system

A study has been conducted to determine the effect of replacing B2O3 with TeO2 on the physical and optical properties of a Pb-free B2O3-TeO2-ZnO-Al2O3-Li2O-MgO glass system, as well as the system's gamma-ray shielding capabilities. The optical basicity of the manufactured glass samples is increased from 0.577 to 0.862, which is a significant improvement. As the quantity of oxygen atoms in the produced glass samples diminishes, the oxygen packing density varies between 102.978 and 78.351, depending on the sample size. The energy of the optical band gap ranges between 3.878 eV and 2.21 eV. The refractive index, dielectric constant, and optical dielectric constant all rise as the amount of TeO2 in the material increases. The values of molar refractivity (Rm) and electronic polarizability (αm) have been shown to decrease as the amount of TeO2 in the sample has increased. The radiation protection efficiency RPE (%) for the glasses was reported at 0.356 MeV. We compared the RPE (%) for the glasses with lowest and highest TeO2 content and we found that the RPE values for the Te10 and Te60 glasses are 8% and 13% respectively (this is for a thickness of 0.25 cm). Also, we found that the RPE of the Te10 glass becomes 35% and that of the Te60 glass is 51% when the thickness of both the glasses is increased to 1.25 cm. The effective atomic number (Zeff) for the glasses was reported at 0.356 MeV. The Zeff of the glass system showed an upward trend with TeO2 concentration.

Radio refractivity computations in Kano, Northwestern Nigeria

This paper is the study of radio refractivity computations in Kano State (12.43°N, 8.19°E), Northwestern Nigeria. One-year meteorological data of relative humidity, pressure, temperature, and dew point were obtained from Nigerian Meteorological Agency (NiMET) and the statistical values of tropospheric radio refractivity were evaluated. The data were further analysed to obtain the refractivity gradient values. From the results, the computed refractivity has peak values of 290 N-Units, 231 N-Units, 158 N-Units and 125 N-Units at heights of 1.5 km, 3 km, 6 km and 8 km respectively, while minimum values of 245 N-Units, 170 N-Units, 146 N-Units and 114 N-Units were obtained at the same respective heights of 1.5 km, 3 km, 6 km and 8 km. For the refractivity gradients, the computed values ranged from -50 N-Units/km to -24 N-Units/km at 3 km, -29 N-Units/km to -22 N-Units/km at 6 km and from -25 N-Units/km to -19 N-Units/km at 8 km.

Estimation of Geoclimatic Factor for Nigeria through Meteorological Data

Geoclimatic factor variable is one of the most important radio climatic variables in the planning of the radio links in any region. A fade margin that takes into account multipath fading has to be incorporated in the link budget in the design of terrestrial line of sight communication system. This work involves the determination of the refractivity gradient over the first 100 m above ground level in Nigeria and by using the determined refractivity gradient, the geo-climatic factor (K) was calculated for typical links in Nigeria. The Geo-climatic factor (K) for the six major cities representing each geopolitical zone in Nigeria is determined in-order to improve future planning of the radio links in the regions. Measurement of meteorological parameters for five years taken in Ikeja, Lagos (Latitude 6º27´11´´N, Longitude 3º23´44´´E), Enugu (Latitude 6º27´35.8704´´N, Longitude 7º32´56.2164´´E), Kaduna (Latitude 10º31´23´´N, Longitude 7º26´25´´E), Port Harcourt (Latitude 4º47´21´´N, Longitude 6º59´54´´E), Kano (Latitude 12º3’N,Longitude 8º32´N) and Abuja (Latitude 9º10´32´´N Longitude 7º10´50´´E) were employed to estimate the country value of K. The pressure, P(hPa), temperature, T(ºC) and the relative humidity, (%), for the six location used were taken for a period of five years (2011-2015). The value of humidity were converted to water vapour pressure, e(hPa). In processing of the data, the average values of each month collected over a period of five years was used. The monthly data was used to calculate the values of the refractivity at the ground level and at 100 m altitude. From the calculated values of refractivity,the values of the refractivity gradient of heights of 65 m and at 100 m was computed and thereafter the geo-climatic factor (K) was calculated for the six geopolitical region of the country.

Alkylacrylic-carboxyalkylacrylic random bipolymers as demulsifiers for heavy crude oils

This paper explains and analyses the process where two series of acrylic random bipolymers, based on alkyl acrylate/carboxyalkyl acrylate (KC) and alkyl acrylate/acrylic acid (KA), were prepared by means of emulsion polymerization technique. In both, the bipolymers’ monomers ratio was varied, while holding the more hydrophobic monomer in majority. The KC and KA bipolymers were characterized by nuclear magnetic resonance (NMR), infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and size exclusion chromatography (SEC). Afterwards, demulsifying activity of the KC and KA bipolymers in two heavy crude oils was evaluated through bottle tests. According to the obtained results, the selection and determination of weight ratio of monomers have an important impact on the bipolymers efficiency to destabilize the water/crude oil emulsion. In both crude oils, KC bipolymer with a monomer ratio of K/C = 80/20 w/w showed the best demulsifying performance in comparison with KA bipolymer at the same weight ratio. Structure-activity parameters including partition coefficient (Log P), hydration energy (HE), molar refractivity (MR), and polarizability (α) were calculated for both bipolymers. The destabilization effectiveness of bipolymers of the water/crude oil interface was found to be related to the partition coefficient (Log P), which indicated a strong diffusion capacity of the bipolymer to traverse through the oil phase and destabilize the water/oil interface. Furthermore, higher values of molar refractivity and polarizability are preferable for higher water removal efficiency (WRE). Moreover, the structure–activity parameters, as well as the quantum parameters, specific characteristics of acrylic bipolymers and some physicochemical properties of the crude oil were deployed in the process to predict the water removal efficiency. E2 equation which accomplished the external validation acted as the resultant of the two equations, E1 and E2, that fulfilled the restriction for the internal validation of Q2 > 0.6. Predictive squared correlation coefficients (QF12,QF22, and QF32) and external validation metric parameter (rm2) were calculated based on E2. Consequently, the new alkylacrylic-carboxyalkylacrylic bipolymers, insusceptible to acid environment, showed significantly improved properties as emulsion breakers, drop coalescers, and clarifiers.

Comparison of Surface Radio Refractivity Variability in the Northern and Southern Parts of Quebec, Canada

AbstractThirty‐nine years of archived meteorological data measured at two stations located in the northern and southern parts of Quebec, Canada are used to estimate the surface refractivity and its dry and wet components. The results of the comparison of the obtained estimates showed that for all months the values of the dry component are higher in the northern part, whereas the values of the wet component are higher in the southern part. Due to this, for several months of the year, the values of the surface refractivity are higher in the northern part and for the remaining months in the southern part. Moreover, in both parts, August is the month where the highest values of the surface refractivity were recorded. In this particular month, the slope of the surface refractivity trend in the northern part is several times higher than that in the southern part. The obtained results show that the performance of the used direct smoothing forecasting technique depends on the deviation between the values of N in the current year and the previous year.

Empirical Models for Estimating Tropospheric Radio Refractivity Over Osogbo, Nigeria

Background:Estimation of tropospheric radio refractivity is significant in the planning and design of terrestrial communication links.Methods:In this study, the monthly average daily atmospheric pressure, relative humidity and temperature data obtained from the National Aeronautics and Space Administration (NASA) during the period of twenty two years (July 1983 - June 2005) for Osogbo (Latitude 7.470N, Longitude 4.290E, and 302.0 m above sea level) were used to estimate the monthly tropospheric radio refractivity. The monthly average daily global solar radiation with other meteorological parameters was used to developed one, two, three and four variable correlation(s) tropospheric radio refractivity models for the location. The accuracy of the proposed models are validated using statistical indicator of coefficient of determination (R2), Mean Bias Error (MBE), Root Mean Square Error (RMSE), Mean Percentage Error (MPE), Nash - Sutcliffe Equation (NSE) and Index of Agreement (IA).Results:In each case one empirical model was recommended based on their exceptional performances after ranking, except for the two variation correlations with two empirical models. The recommended models were further subjected to ranking from which the three variable correlations model that relates the radio refractivity with the absolute temperature, relative humidity and global solar radiation was found more suitable for estimating tropospheric radio refractivity for Osogbo with R2= 100.0%, MBE = -0.2913 N-units, RMSE = 0.3869 N-units, MPE = 0.0811%, NSE = 99.9999% and IA = 100.00%.Conclusion:The newly developed recommended models (Equations 16c, 17d, 17f, 18d and 19) can be used for estimating daily and monthly values of tropospheric radio refractivity with higher accuracy and has good compliance to highly varying climatic conditions for Osogbo and regions of similar climatic information.

Empirical Models for Estimating Tropospheric Radio Refractivity Over Osogbo, Nigeria

Background:Estimation of tropospheric radio refractivity is significant in the planning and design of terrestrial communication links.Methods:In this study, the monthly average daily atmospheric pressure, relative humidity and temperature data obtained from the National Aeronautics and Space Administration (NASA) during the period of twenty two years (July 1983 - June 2005) for Osogbo (Latitude 7.470N, Longitude 4.290E, and 302.0 m above sea level) were used to estimate the monthly tropospheric radio refractivity. The monthly average daily global solar radiation with other meteorological parameters was used to developed one, two, three and four variable correlation(s) tropospheric radio refractivity models for the location. The accuracy of the proposed models are validated using statistical indicator of coefficient of determination (R2), Mean Bias Error (MBE), Root Mean Square Error (RMSE), Mean Percentage Error (MPE), Nash - Sutcliffe Equation (NSE) and Index of Agreement (IA).Results:In each case one empirical model was recommended based on their exceptional performances after ranking, except for the two variation correlations with two empirical models. The recommended models were further subjected to ranking from which the three variable correlations model that relates the radio refractivity with the absolute temperature, relative humidity and global solar radiation was found more suitable for estimating tropospheric radio refractivity for Osogbo with R2= 100.0%, MBE = -0.2913 N-units, RMSE = 0.3869 N-units, MPE = 0.0811%, NSE = 99.9999% and IA = 100.00%.Conclusion:The newly developed recommended models (Equations 16c, 17d, 17f, 18d and 19) can be used for estimating daily and monthly values of tropospheric radio refractivity with higher accuracy and has good compliance to highly varying climatic conditions for Osogbo and regions of similar climatic information.

Estimation of Radio Horizon Distance Using Measured Meteorological Parameters over Some Selected Locations in Nigeria

In this study, results of the variation of maximum and minimum radio horizon distance derived from the computation of surface refractivity through measurement of temperature, relative humidity and pressureacrosssevenlocations((Akure (7.15°N, 5.12°E), Lagos (6.30°N, 3.20°E), Abuja (7.10°N, 9.25°E), Jos (9.50°N, 8.50°E), Makurdi (7.30°N,8.53°E), Port-Harcourt(4.20°N,7.00°E), and Nsukka (6.90°N,7.67°E)) in Nigeria are presented. Two years (Jan., 2011–Dec., 2012) archived data as provided by Tropospheric Data Acquisition Network (TRODAN) of the Centre for Atmospheric Research Anyigba, Kogi State were utilized for the study. Results showed that the values of surface refractivity (Ns) were low during the dry season months and high during the wet season months and also there was high value of NS at the coastal areas compared with the inland areas. It was also deduced that the mean value of NS for Abuja, Akure, Jos, Lagos, Markurdi, Nsukka and Port-Harcourt is 355, 362, 303, 391, 375, 361 and 399 N-units respectively. Results showed that the Radio Horizon Distance (RDH) values were generally low during the wet season months and high during the dry season months. The variability of radio horizon distance of transmitting antennas is higher in the Northern part of Nigeria than the southern part.

Linkage of meteorological parameters and anomalous radio propagation profile over Nigeria

The vertical distribution of refractivity gradient is important in determining anomalous propagation condition. Thirty five years of meteorological parameters, obtained from Era-Interim archive of European Centre for Medium-Range Weather Forecasts has been used to analyze and investigated surface meteorological data linked with refractivity gradient aloft altitude across Nigeria. Spatial distribution of surface temperature, relative humidity and refractivity gradient at 0.1 km, 0.5 km, 1.0 km and 1.5 km over Nigeria were plotted. Vertical distribution of temperature, relative humidity, refractivity and refractivity gradient were obtained for some locations across Nigeria. Similarly, spatial distribution of coefficient of determination between surface temperature, relative humidity and refractivity gradient at four different height were estimated. Linear regression were developed to investigate the relationship between surface data and refractivity gradient at different altitude. The result revealed existence of sub refractive, super refractive, and ducting across the country at 0.1 km and 0.5 km however occurrence of ducting and sub refractive disappeared at 1.0 km and 1.5 km. Likewise, the existence of temperature inversion was noticed between surface and 100 m across all the locations except in Lagos. Values of refractivity across the observed locations converged around 0.5 km. Through result of correlation coefficient and statistical parameters, significant linked have been established between surface data and refractivity gradient at different height.

Assessment of Anomalous Propagation Conditions in Ondo City, South Western Nigeria for Microwave Applications

Recent results of the in-situ measurement of radio climatological parameters of pressure, temperature and relative humidity carried out to investigate the trends in propagation conditions over altitude of 100-m in Ondo city Nigeria are presented. The assessments have been based on the time series of average value of the radio refractivity on the season of the year, characterization of radio refractivity gradient and the impact of secondary radio climatic data on terrestrial line of sight link design in Ondo city. We have used concurrent measurement of pressure, relative humidity and temperature for the period between 2017 and 2018. The results obtained confirmed the assertion that radio refractivity values are higher during the wet season months when compared with the dry season months. Yearly variation shows that the values of refractivity in the year 2018 are much higher than ones obtained in the year 2017. Results of radio refractivity gradient also shows a considerably large negative N value of about 288 N-units/km for the month of October and the value later becomes less negative in the remaining months of the year. Average value of k-factor during the dry and wet seasons for the year under study is about 1.37 and 1.47 respectively. This implies that, for microwave propagation in the Ondo environ, the propagation condition could be largely super-refractive during these seasons. A good relation also exists between Geoclimatic factor and season of the year. The overall will assist in achieving optimum performance of digital terrestrial point to point links in Ondo city. Keywords: Propagation behavior, Time series analysis, Refractivity gradient, k-factor, Geoclimatic factor DOI : 10.7176/JEES/9-4-07 Publication date : April 30 th 2019

Performance Analysis of Tropospheric Radio Refractivity on Radio Field Strength and Radio Horizon Distance and Its Variation with Meteorological Parameters over Osogbo, Nigeria

Radio refractivity estimation is paramount in the planning and design of radio link/systems for the purpose of achieving optimal performances. In this study, the monthly average daily atmospheric pressure, relative humidity and temperature data obtained from the National Aeronautics and Space Administration (NASA) during the period of twenty two years (July 1983 – June 2005) for Osogbo (Latitude 7.47 0N, Longitude 4.29 0E, and 302.0 m above sea level) were used to estimate the monthly tropospheric radio refractivity and to investigate its variation with other meteorological parameters of monthly average daily atmospheric pressure, relative humidity, absolute temperature, saturation vapour pressure and radio refractive index. The field strength variability (FSV) and the radio horizon distance were also computed. The monthly variation of FSV using two years of data (2003 – 2004) was also investigated. The results of this study revealed that the values of radio refractivity are more during the rainy season than in the dry season. It was found that the maximum average value of tropospheric radio refractivity of 370.98 N-units and the minimum average value of 332.36 N-units occurred in the months of May and January during the rainy and dry seasons respectively. 71.45 % of the total value of the radio refractivity was contributed by the dry term while the major variation is by the wet term radio refractivity. The average refractivity gradient computed for the study area under investigation was −42.69 N-units/km and the average effective earth radius (k – factor) was 1.37 which corresponds to the conditions of super refraction. The annual maximum mean value of FSV is 7.72 dB and the minimum monthly mean value of 0.07 dB was obtained for the study area. The implication of this FSV values is that the output of a receiving antenna in Osogbo may generally be subjected to changes not less than 0.07 dB in a year and not greater than 7.72 dB. The descriptive statistical analysis shows that the radio refractivity, relative humidity, absolute temperature and radio refractive index data spread out more to the left of their mean value (negatively skewed), while the atmospheric pressure data spread out more to the right of their mean value (positively skewed). The radio refractivity, relative humidity and radio refractive index data have positive kurtosis which indicates a relatively peaked distribution and the possibility of a leptokurtic distribution. The atmospheric pressure and absolute temperature data have negative kurtosis which indicates a relatively flat distribution and possibility of platykurtic distribution.

Diurnal and Seasonal Variation of Surface Refractivity in Minna and Lapai, North Central Nigeria

Spatial and temporal variations of surface refractivity, Ns, in the troposphere are important parameters in designing terrestrial communication links. This research work examines the effect of variations of meteorological parameters on surface radio refractivity during dry and wet seasons in Minna and Lapai (2011-2013). The data on surface temperature, humidity and pressure collected from the Tropospheric Data Acquisition Network (TRODAN) weather stations installed at the Federal University of Technology, Minna, and at Ibrahim Badamasi Babangida University, Lapai, were used for the computation of radio refractivity. The hourly and monthly averages of radio refractivity during dry and wet seasons were calculated. The results showed that surface refractivity varied diurnally and seasonally in both stations. Refractivity values were high during the early morning and night hours and decreased rapidly during the afternoon hours. Values of refractivity were also generally low during the dry season months and high during the wet season months. It was also observed that refractivity values were higher at Lapai than Minna in dry season months. The result also shows that diurnal refractivity variation is attributed to atmospheric phenomena while seasonal variation is caused by the climatic conditions of the regions. Maximum values of 350 N-units in August in 2011, 343 N-units in July in 2012 and 347 N-units in August in 2013, while the minimum values of 275 N-units in January in 2011, 278 N-units in March in 2012 and 273 N-units were recorded in February for Minna. Surface refractivity has maximum values of 350 N-Units in August (2011), 347 N-Units in August (2012) and 349 N-Units in September (2013), while minimum values of 289 N-Units, 290 N-Units and 297 N-Units occurred in January in 2011, 2012 and 2013 respectively for Lapai.