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.


Subject area
Meteorology and Atmospheric environment More specific subject area

Satellite Communication, Radiowave propagation, Radio Science
Type of data

Data source location
Data Obtained from National Oceanic and Atmospheric Administration (NOAA) Climatology Centre, USAF Data accessibility All the data are in this article as a supplementary file

Value of the data
The data could be useful for government in understanding of radio propagation within or around the lower atmosphere in the southeast region of Nigeria.
The database could provide insights of radio refractivity and water vapour density for the five locations.
The dataset will help engineers in siting good antenna reception at ground level for AM, FM, VHF, UHF bands in Nigeria.
The data will be useful in understanding of the refractive index structure of the atmosphere through which the waves travel.

Data
The meteorological data for this article were obtained from National Oceanic and Atmospheric Administration (NOAA) Climatology center for the period of about thirty-nine years from 1973 through 2012 for five locations within southeast, Nigeria. The data input parameters such as pressure, temperature, and relative humidity were used for the calculation of surface radio refractivity (N) for all the location. The meteorological data assembled were based on one-minute to produce the daily average data and consequently to acquire the monthly. Therefore, the monthly means of the measurements, over the thirty-nine years is a good characteristic of the seasonal behavior of surface radio refractivity as revealed in Tables 1a-1e. The descriptive statistics summaries of the surface refractivity are presented tables. While, bar charts for the refractivity distribution are presented in figures.
Radio refractivity, N, depends on meteorological parameters such as the pressure P (mbar), the absolute air temperature T (K), and the vapour pressure e (mbar) as given in Eq. (1). N dry and N wet are frequently denoted as dry and wet terms of atmospheric radio refractivity, respectively. where: and The nature and usefulness of the data entails that it can be analyzed using different statistics techniques like ordinary least square regression analysis, simple correlation, multiple correlation analysis, analysis of variance, factor analysis and principal component analysis just to mention few. The summary statistics of the data collected from Enugu state is presented in the Table 2 below. The data was also presented in a bar chart in Fig. 1. The bar chart is a representation of the descriptive statistics which revealed the level of radio refractivity recorded monthly for the state.

The summary statistics of the data from Anambra state
The summary statistics of the data collected from Anambra state is presented in the Table 3 below. The data was also presented in a bar chart in Fig. 2. The bar chart is a representation of the descriptive statistics which revealed the level of radio refractivity recorded monthly for the state.

The summary statistics of the data from Ebonyi state
The summary statistics of the data collected from Ebonyi state is presented in the Table 4 below. The data was also presented in a bar chart in Fig. 3. The bar chart is a representation of the descriptive statistics which revealed the level of radio refractivity recorded monthly for the state.

The summary statistics of the data from Abia state
The summary statistics of the data collected from Abia state is presented in the Table 5 below. The data was also presented in a bar chart in Fig. 4. The bar chart is a representation of the descriptive statistics which revealed the level of radio refractivity recorded monthly for the state.

The summary statistics of the data from Imo state
The summary statistics of the data collected from Imo state is presented in the Table 6 below. The data was also presented in a bar chart in Fig. 5. The bar chart is a representation of the descriptive statistics which revealed the level of radio refractivity recorded monthly for the state.

Materials and methods
Several researches have been conducted on surface radio refractivity in Nigeria [1][2][3][4][5][6][7][8][9][10][11][12][13]. However, this work is relevant with a focus on southeast zone, Nigeria where few research has been concluded. Hence, formed the uniqueness of this data and the analysis. Similar statistical tools on refractivity were applied by [14,15]. Radiosonde data for at least 39 years between 1973 and 2012 for 5 stations  within Southeast Nigeria were utilized for the computation. It was launched from National Oceanic and Atmospheric Administration (NOAA) Climatology center based in United State of America (USA). The variables contained in the meteorology data such as pressure, temperature, and relative humidity were used as input parameters for the outcome of this article.

Transparency document. Supporting information
Transparency data associated with this article can be found in the online version at https://doi.org/ 10.1016/j.dib.2017.11.052.