Spatial and Temporal Distribution of Modified Radio Refractivity Gradient at 875 hPa and 700 hPa over Nigeria

Main Article Content

S. E. Falodun
J. S. Ojo
V. O. Oviangbede


The meteorological effects on radio wave signals propagating through the troposphere are of great concerns in the design and performance of radio communication systems. Often, the effect can lead to anomalous propagation conditions such as ducting, super refraction and sub refraction. In this paper, the spatial-temporal distribution of modified radio refractivity gradient and the effects on radio waves propagating at 875 hPa and 700 hPa pressure levels over sixteen selected locations aloft the four climatic regions of Nigeria are investigated. Five (5) years (2013-2017) meteorological parameters namely: air temperature, relative humidity and atmospheric pressure at ground level and 1 km above ground level were obtained from the European Center for Medium-Range Weather Forecast (ECMWF) at four synopses hours of the day. Modified radio refractivity and its gradient at the two pressure levels were computed using ITU- model. Results on a daily and seasonal basis shows similar trends at both 875 hPa and 700 hPa pressure levels, with higher values of modified radio refractivity gradient recorded at 700 hPa heights at the morning and night hours of the day. Results on seasonal basis shows that during the rainy season, modified radio refractivity gradients were high. On location basis, Port Harcourt (coastal region) recorded the highest value of modified radio refractivity gradient of about 115.5 M-units/km in the night time (00:00 hr. LT). The value depicts the occurrence of normal refraction in this location. The overall results will be useful for microwave links budgeting and design in Nigeria.

Temporal distribution, modified radio refractivity, radio wave signals, radio communication systems.

Article Details

How to Cite
Falodun, S. E., Ojo, J. S., & Oviangbede, V. O. (2019). Spatial and Temporal Distribution of Modified Radio Refractivity Gradient at 875 hPa and 700 hPa over Nigeria. Physical Science International Journal, 23(3), 1-13.
Original Research Article


Sasaki O, Akyama T. Studies on radio duct occurrence and properties. IEEE Transactions on Antennas and Propagation. 1982;30:853-858.

Mufti N, Siddle D. Investigations into the initial refractivity gradients and signal strengths over the English Channel. 7th European Conference on Antennas and Propagation, Gothenburg. 2013;1691-1694.

Willoughby AA, Aro TO, Owolabi IE. Seasonal variations of radio refractivity gradients in Nigeria. Journal of Atmosphere and Solar-Terrestrial Physics. 2002;64:417-425.

Mentes S, Kaymaz Z. Investigation of Surface Duct Conditions over Istanbul, Turkey. Journal of Applied Meteorology and Climatology. 2006;35: 318-329.

Babin S. Surface duct height distributions for Wallops Island, Virginia, 1985-1994. Journal of Applied Meteorology. 1995;35: 86-87.

Rogers TL. Likelihood estimation of tropospheric duct parameters from horizontal propagation measurements, Radio Science. 1997;32:79-92.

Ojo OL, Ajewole MO, Adediji AT, Ojo JS. Microwave anomalous propagation conditions in the First 100-m altitude in a tropical location. Journal of Microwave Power and Electromagnetic Energy. 2014; 48(2):131-137.
DOI: 10.1080/08327823.2014.11689877

Oyinloye JO. The troposphere in tropical and Sub-tropical latitudes in-handbook on radio propagation for tropical and sub-tropical countries, URSI Committee on Developing Countries. 1987;77-79.

Owolabi IE, Williams VA. Surface radio refractivity patterns in Nigeria and the Southern Cameroon. J West Africa Science Association. 1970;1:3-17.