SPACIO-TEMPORAL VARIATION OF RADIO REFRACTIVITY IN LAFIA, NASARAWA STATE USING CM SAF ATOVS SATELLITE DATA

الملخص

Communications using radio waves propagates through the atmosphere and plays a major role in civilization. Vertical variation of radio refractivity in Lafia( 8.492°N and 8.517°E ) Nigeria, was investigated with a five-year (2010 – 2014) monthly mean atmospheric layered data from the ATOVS (Advanced TIROS (Television InfraRed Observation Satellite) Operational Vertical Sounders) instruments flying onboard the NOAA and Metop-A satellites; this data is provided by the EUMETSAT’s Climate Monitoring Satellite Application Facilities (CM SAF). Using the CM SAF data, at six pressure levels (1000hPa, 850hPa, 700hPa, 500hPa, 300hPa and 200hPa), the monthly mean of radio refractivity were estimated and the results analyzed. Also, the diurnal variation of the surface radio refractivity was also investigated using the data from the automatic weather station (model no WS104) installed at the Department of Physics, Federal University Lafia. Results obtained showed that the vertical model of the radio refractivity N, in Lafia could be given as N=No exp(-h⁄ho ),
where No, the surface radio refractivity, was found to be approximately equal to 288.1 N-units, while the scale height ho, was found to be approximately equal to 8.40km; it was found that sub-refraction predominates in Lafia at all seasons. The diurnal range of surface radio refractivity as measured by the in-situ weather station was found to be between 325.0 and 365.0 N-units, with a maximum in the morning and minimum in the afternoon