American Journal of Astronomy and Astrophysics
Volume 6, Issue 4, December 2018, Pages: 97-101
Received: Jan. 16, 2019;
Accepted: Mar. 5, 2019;
Published: Mar. 22, 2019
Views 303 Downloads 56
Adedayo Kayode David, Department of Physics, Federal University of Technology, FUTA, Akure, Nigera
Emmanuel Israel, Department of Physics, Federal University of Technology, FUTA, Akure, Nigera
Ojo Olusola Samuel, Department of Physics, Federal University of Technology, FUTA, Akure, Nigera
This paper investigate the percentage of anomalous occurrence in tropic region of West Africa using meteorological data obtained from Era interim archive. The data covered the period of 36 years span from 1979 to 2014. Refractivity gradient, G are calculated from meteorological parameters (temperature, relative humidity and pressure) via surface refractivity and refractivity at 100m above the sea level. Relative incidence, βo, which percentage of time refractivity gradient at 100 m is less than -100 N-units/km were estimated from cumulative distribution of refractivity gradient. The result shows the occurrence of seasonal variation of refractivity gradient across the observed stations with high variability in Jos. Super refraction and ducting condition are prevalent in Akure and Lagos stations, whereas sub refraction and ducting conditions are predominant in Jos during the rainy and dry season respectively. Minimum values of relative incidence of about 10% and 78% at Akure and Lagos respectively were obtained around 12 noon. Highest relative incidence of 80%, 98% and 97% were obtained at Jos, Lagos and Akure respectively in the mid night. Positive correlation of 0.29 and 0.66 exist between surface refractivity and βo in Lagos and Akure respectively, moreover negative correlation of -0.84 is observed in Jos.
Adedayo Kayode David,
Ojo Olusola Samuel,
Anomalous Radio Propagation and Relative Incidence inTropical Zone, American Journal of Astronomy and Astrophysics.
Vol. 6, No. 4,
2018, pp. 97-101.
Bech J., J. Sairouni, B. Codina, J. Lorente and D. Bebbington, “Weather radar anaprop conditions at a Mediterranean coastal site,” Phys. Chem. of the Earth (B), 25, 829-832, 2000.
Hermann J. A., A. S. Kulessa, C. Lucas, R. A. Vincent, J. M. Hacker and C. M. Ewenz, “Impact of elevated atmospheric structures upon radio-refractivity and propagation,” in: Proceedings of the Workshop on the Applications of Radio Science, 20-22, 2002.
Willoughby A. A., T. O. Aro and I. E. Owolabi, “Seasonal variations of radio refractivity gradients in Nigeria,” Journal of Atmospheric and Solar-Terrestrial Physics, 64, 417–425, 2002.
Adeyemi B, “Tropospheric radio refractivity over three Radiosonde Stations in Nigeria, Ife J Sci (Nigeria),” 6( 2). 167-176, 2004.
Adediji A. T. and M. O. Ajewole, “Vertical profile of radio refractivity gradient in Akure, Southwest Nigeria,” Progress in Electromagnetic Research 14, pp. 157-168, 2008.
Adeyemi B. and I. Emmanuel, “Monitoring tropospheric radio refractivity over Nigeria using CM–SAF data derived from NOAA – 15, 16 and 18 satellites,” Indian Journal of Radio and Space Physics 40, pp. 301 – 310, 2011.
Emmanuel I. and B. Adeyemi, “ Statistical Investigation of Clear Air Propagation in the Coastal and Plateau Regions of Nigeria,” Progress In Electromagnetics Research Letters, 64, 37-41, 2016.
Emmanuel I., B. Adeyemi, E. O. Ogolo and A. T. Adediji, “Characteristics of the anomalous refractive conditions in Nigeria,” Journal of Atmospheric and Solar-Terrestrial Physics, 164, 215-221, 2017.
Adefolalu D. O, Rainfall trends in Nigeria, Theoretical and Applied Climatology, 37, 205-21, 1986.
ITU-R Recommendation P. 453-10, “The radio refractive index: its formula and refractivity data,” International Telecommunication Union, 2012.
Dominguez M. A., A. Benarroch and J. M. Riera, “Refractivity statistics in Spain: First results,” COST 255, CP52004, 1988 Shen X. D. and E. Vilar, “Anomalous transhorizon propagation and meteorological processes of a multilink path,” Radio Science, vol. 30, (5), 1467 – 1479, 1995.
Hayton T. G. and K. H. Craig, “Use of radiosonde data in propagation prediction, presented at the IEE, Savoy Place,” WC2R OBL, London, U. K, 1996.
AbouAlmal A., R. A. Abd-Alhameed, K. Al-Ansari, H. AlAhmad, C. H. See, S. M. R. Jones and J. M. Noras, “Statistical Analysis of Refractivity Gradient and Parameter in the Gulf region,” IEEE Transactions on Antennas and propagation, 61, No. 12, December -2013, 6250-6254, 2013.
Zhu, M. and B. W. Atkinson, “Observed and modelled climatology of the land-sea breeze circulation over the Persian Gulf,” Int. J. Climatol. 24: 883–905, 2004.