a b s t r a c tThe activity concentration of 226 Ra, 232 Th 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 À1 for 226 Ra, 232 Th and 40 K respectively. The highest radium equivalent (Ra eq ) of 273.9 Bqkg À1 was noted in Perfect Superfix White Cement (Nigeria) but found to be < 370 Bqkg À1 as the recommended dose limiting safe value for bulk media as presumed, the highest value of internal hazard index (H in ) and external hazard index (H ex ) of 0.894 and 0.744 respectively were also < 1. The absorbed dose rate (DR) with a value of 122.52 nGyh À1 noted in ceramic tile sample is higher than the weighted population world average value of 80 nGyh À1 by a factor of 1.53. The highest annual effective dose rate (AEDR) of 0.601 mSvy À1 reported in PNT ceramics but was found to be less < 1 mSvy À1 . The investigated materials have the values of H in , H ex and AEDR greater than 0.5 but less than1, showing that the dose impact exceeds the exemption dose level of 0.3 mSvy À1 for AEDR but complies to the upper limit of dose principle of 1 mSvy À1 .

This is a further study on development of the cloud attenuation model for improvement of the availability of satellite services in tropical Ota (6.7oN, 3.23oE) climatic zone. The radiometric data analysis has been re-evaluated for better accuracy through the Matlab embedded into the data processing electronic spreadsheets. The collection of station data such as the spectrum analyser beacon measurements of the total attenuation at re-established elevation angle 59.9° to Astra 2(E-G) satellites located at 28.2°E; the station weather parameters and the clouds parameters visual measurements; as well as the acquisition of station climatic zone radiosonde data were carried out. Then the station spectrum analyser data for 2014 - 2017 were analysed to obtain cloud attenuation contributions from the total attenuation measurement. Cloud attenuation distributions outputs of these data analyses were used to obtain the station integrated cumulative distribution for each of the existing cloud models and the 2014 – 2017 integrated data. The results at the station beacons frequency of 12.245 GHz show wide gap between the 3.40 dB maximum cloud attenuation by the Ota spectrum analyser integrated data cumulative distribution to the 0.81 dB maximum cloud attenuation predicted by its closest ITU-R model, while next in closeness is the Liebe model, followed by Slobin model. This recommends a new cloud attenuation model be developed for the tropical region. The earlier published cloud attenuation algorithm is further developed with simulation program written to run its simulations cycles over possible range of maximum signal amplitudes, using the Ota climatic zone radiosonde empirical data (1953-2011) for computations of each cloud layer’s liquid water content and specific cloud attenuation coefficient. The cumulative distribution curves obtained were compared with those for each generated simulation distribution and the closest match to the station integrated data cumulative distribution became the new cloud attenuation model for Ota climatic zone. The new model predicted 4.0 dB margin for signals to pass through clouds attenuation effect in the Ota climatic zone, revealing that the prediction for cloud attenuation by the earlier models largely under estimate the margin for the tropical region.

Graphical abstractSurvey plan for the Study.

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.

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