Abstract
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.
Highlights
Refractivity is defined as the physical property of a medium as determined by its index of refraction and it is responsible for the different phenomena in radio wave propagation which comprises of refraction and fading, ducting and scintillation, range and elevation errors in radar acquisition [1].The way by which radio signals travel from the transmitter to receiver is of great importance when constructing a radio communication network
It was observed that the highest atmospheric pressure was in the month of August with 988.1994 hPa and the lowest value was in the month of March with 984.0770 hPa
It was observed that the highest relative humidity was in the month of September with 85.5913% and the lowest value was in the month of January with 54.6957%
Summary
Refractivity is defined as the physical property of a medium as determined by its index of refraction and it is responsible for the different phenomena in radio wave propagation which comprises of refraction and fading, ducting and scintillation, range and elevation errors in radar acquisition [1]. The way by which radio signals travel from the transmitter to receiver is of great importance when constructing a radio communication network. This is governed to a reasonable extent, by the state of the atmosphere through which the waves traverse. The variations in the refractive index of the troposphere are small but, play an important role in radio wave propagation. Estimation of tropospheric radio refractivity is significant in the planning and design of terrestrial communication links
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