S. A. Akinwumi

Dataset of surface refractivity in Southeast, Nigeria

In this data article, analysis of surface refractivity and water vapour density in Southeast, Nigeria were reported. The meteorological data were collected for the period of 39 years between 1973 and 2012 from National Oceanic and Atmospheric Administration (NOAA) Climatology Centre. Five locations considered in the study area includes: Enugu, Onitsha, Abakaliki, Aba and Ihiala. Descriptive statistics were used to show an increase in monthly variation of refractivity of about 299.8 N units at Enugu in January to peak value of about 385.81 N units at Abakaliki in May. Hence, the seasonal variation for South East indicate maximum value within the months of March to May in the rainy season and a minimum value around December to February which is the dry season. The results from this data will help engineers in proper design and planning of radiowave propagation and satellite communication systems in southeastern, Nigeria.

Dataset of surface water vapour density in southeast, Nigeria

In this data article, analysis of surface water vapour density in Southeast, Nigeria were reported. The meteorological data were obtained for the period of 39 years between 1973 and 2012 from National Oceanic and Atmospheric Administration (NOAA) Climatology Centre. Five stations considered in the research area includes: Enugu, Onitsha, Abakaliki, Aba and Ihiala. Descriptive statistics were used to show an increase in monthly variation of surface water vapour density (SWVD) minimum value of about 7.15 g/m3 at Enugu in January to maximum value of about 21.96 g/m3 at Onitsha in April. Hence, the seasonal variation for South East indicate peak value within the months of March to May in the rainy season and a lower value around December to February which is the dry season. The results from this data will help engineers in proper design and planning of radiowave propagation and satellite communication systems in southeastern, Nigeria.

Analysis of non-rainy attenuation on earth-space path in Ota, Southwest Nigeria

Propagation effects due to atmospheric gases and tropospheric scintillation requires accurate modelling in the design of satellite communication systems. The combination of the two attenuation phenomena was observed within the period of August 2014 to December 2015. The result of this paper presents the on-going observation and data analysis of non-rainy attenuation on earth-space path in Ota, Southwest Nigeria. Results of clear-sky attenuation vary between 0 dBm and 4.85 dBm in January and February 2015 respectively. While a value of 4.23 dBm and 4.75 dBm were observed in October 2014 and 2015 respectively. The results will be useful for satellite communication system design and will be submitted to ITU-R Study group 3 Databank.

Radiation exposure to dwellers due to naturally occurring radionuclides found in selected commercial building materials sold in Nigeria

Abstract The activity concentration of 226Ra, 232Th and 40 K was measured in commonly building materials used in Nigeria from commercial supplier using High Purity Germanium Gamma (HPGe) detector. The mean activity concentrations in the samples were found to be 51.5 ± 9.3, 72.46 ± 17.65 and 217.05 ± 44.31 Bqkg−1 for 226Ra, 232Th and 40 K respectively. The highest radium equivalent (Raeq) of 273.9 Bqkg−1 was noted in Perfect Superfix White Cement (Nigeria) but found to be < 370 Bqkg−1 as the recommended dose limiting safe value for bulk media as presumed, the highest value of internal hazard index (Hin) and external hazard index (Hex) of 0.894 and 0.744 respectively were also < 1. The absorbed dose rate (DR) with a value of 122.52 nGyh−1 noted in ceramic tile sample is higher than the weighted population world average value of 80 nGyh−1 by a factor of 1.53. The highest annual effective dose rate (AEDR) of 0.601 mSvy−1 reported in PNT ceramics but was found to be less < 1 mSvy−1. The investigated materials have the values of Hin, Hex and AEDR greater than 0.5 but less than1, showing that the dose impact exceeds the exemption dose level of 0.3 mSvy−1 for AEDR but complies to the upper limit of dose principle of 1 mSvy−1. Highlights • Radioactivity in building materials gamma activity index.• Alpha activity index.• Internal and external hazard index. Graphical abstract Identification of radioactivity level in building materials and its risks on dwellers.

Radiation from Visual Display Unit

The radiation from different types of Visual Display Units (VDU) (that is, Liquid Crystal Display (LCD) and Cathode Ray Tube (CRT)), projector and interactive screen were examined using a Cell Sensor Extremely Low Frequency (ELF) detection meter. The study revealed that ELF radiation in CRT VDUs is eight (8) times greater than in LCD VDUs. The mean ELF obtained from interactive screen at 30 cm was 1.6 mG and 1.9 mG at start-up and after 3 hours of use respectively with a mean value of 1.03 mG for a distance of 100 cm at start up. The mean ELF radiation from the projector screen at a distance of 10 cm is 0 mG, while that of interactive screen is 2.4 mG at the same distance. Thus, the study suggested that, projector and screen is better than interactive screen when making presentation considering the closeness of user to the interactive screen throughout the course of presentation.

Construction of an in-situ smart device that measures some basic environmental factors for agricultural monitoring

Most of the rural agricultural and extension officers have no access to the daily variations in meteorological data that affect the growth and yield of crops. This is as a result of little or no access to the data that could be used to predict the best agricultural practices for optimum output in the rural environments. In this work, a portable and user friendly smart Automated Weather Station (AWS) was constructed. The device that is programmed with Arduino UNO is capable of measuring the temperature, relative humidity and moisture content of the soil. The performance evaluation of the device was observed in the laboratory and onsite (Covenant University farm) both on the sunny and rainy days respectively. It was revealed that there is positive linear relationship between the volume of water added to the soil sample and the soil moisture content in the laboratory measurements. The on-site measurements showed that the temperature is inversely proportional to the relative humidity and soil moisture content. This device is efficient in taking the short-term essential parameters that could improve the yield of agricultural products in the rural environments if properly utilized.

Analysis and comparison of tropospheric scintillation prediction models at Covenant University

Knowledge of tropospheric scintillation is an important phenomenon in the design of satellite communication system. One year (January 2015-December 2015) scintillation data extracted from Astra 2E/2F/2G Satellite link measurement installed at Covenant University, Ota (Lat: 6.7 oN, Long: 3.23 oE) southwest Nigeria, at an elevation angle of 59.9o and a frequency of 12.245 GHz was used in this study. The analysis and the result were compared with some reputable scintillation prediction models so as to obtain best performance model for Ota region. From the result, it was discovered that the Karasawa model gives the lowest percentage error rate for both fade and enhancement of about 0.57% at 0.1 percentage of time and 6.93% at 0.01 percentage of time respectively and therefore was best found fit for the prediction of propagation impairment for the region. However, the model should be tested further using higher frequency band such as Ka and V bands to confirm the accuracy of the model. The information provided in this study will help in fade margin for antenna sizing and performance needed for satellite communication link in the region.

Cloud attenuation modelling for satellite network links performance improvement

All local climate zones need to develop relevant climatic models such as cloud attenuation model which can serve as correlative resources to global satellites applications and a means of determining local link margins for satellite networks services in localities. Effects of suspended water droplets (SWD) and suspended ice crystals (SIC) which constitute clouds are major concern in the design and successful operation of satellite communication system at frequencies above 3GHz because the hydrometeors reduces the services availability critically as frequency increases. This work is a review of cloud attenuation modelling, using as a case study typical research work been carried out, to develop cloud attenuation model for tropical Ota (6.7oN, 3.23oE), southwest Nigeria. Cloud attenuation modelling for a station involve obtaining clouds parametric system equation from their numerical representations, taking into consideration the climatic initial and boundary conditions. The numerical representations are collected climatological and radiometric data, derived from well-designed experiments in which cloud parameters measurements are carried out using radiances change measured by satellites and visual observations from the surface station(s) on land and ships in the ocean. The on-going research work begin with the study of performance of eight foundation cloud models at the station, through their detailed evaluation from cloud cover data and radiosonde data analysis, followed by analysis of collected over three years spectrum analyser signal attenuation data. Then modelling analysis of the station spectrum analyser data collected at computed elevation angle 56.18o to Astra 2(E-G) Satellite located at 28.2oE, which involve comparisons of the derived attenuation distribution curves, both of the spectrum analyser data and those of the existing cloud models for the station, with the derived attenuation distribution curves of output data generated by each run session of the station simulation equation program. The general representation of the station cloud attenuation model is stated and the specific model equation is been worked on.

Comparison between experimental and satellite temperature datasets in Covenant University

This article contains the ground and satellite meteorological data sets of clear-sky temperature events for five years (2012–2016) in Covenant University, Ota, Ogun State, Nigeria. The satellite data were obtained from Atmospheric Infrared Sounder (AIRS) while the ground data information were acquired from Davis weather station data logger-vantage pro2. These data were acquired from propagation study that used same location (Lat: 6.67°N and Long: 3.23°E) for both satellite data and radiometer directed along the same path by providing information about the temperature. The data sets were assessed and evaluated by means of a descriptive statistics. There was perfect agreement between the two data. The peak temperature events occurs between the months of November and April for the five years of observation for both Ota and AIRS Satellite. The data from this article can be used for further studies on non-rainy attenuation effect in the study area.

Year to year variation of rainfall rate and rainfall regime in Ota, southwest Nigeria for the year 2012 to 2015

The tropics is characterized to have convective type of rainfall which has high occurrence of rainfall compared to the temperate regions of the world. In this paper, the accumulation of rainfall in Ota, Southwest, Nigeria (6o 42 N, 3o 14 E) has been analysed to present the one-minute rainfall rate and the predominant type of rainfall. Four years’ data used for this study was taken using the Davis Wireless vantage Pro2 weather station at Covenant University, Ota, Ogun State. The data collected were used to analyse the one-minute rainfall rate and different types of rainfall predominant in this region. For the prediction and modelling of rain attenuation at microwave frequencies for a region like the Nigeria at various percentage of time, one-minute rainfall rate is required. Nigeria falls into the P zone of 114 mm/hr. as per International Telecommunication Union – Recommendation (ITU-R). The analysis carried out indicated that the measured yearly averaged maximum one-minute rainfall rate for 2012, 2013, 2014 and 2015 are 157.7 mm/h, 148.0 mm/h, 241.2 mm/h and 157.3 mm/h respectively. It also indicated that the drizzle type of rainfall is predominant in contrast to established fact that thunderstorm occurs more in the tropics.