Abstract
The refractivity variations of the troposphere are responsible for various effects on radio wave propagation, such as refraction, bending, radio-station interference, etc. In this work, the refractivity variations of the Hellenic troposphere are studied using data from Helliniko airport of Athens/Greece. The data were analyzed using various interpolation procedures, i.e. in a day-by-day manner for temperature and relative humidity, to transform the data according to a reference height common for the whole dataset and finally for the refractivity N with respect to time, using piece-wise hermite interpolation polynomials for the low and medium altitudes and linear interpolation factors for the high altitudes. Since refractivity varies with time and height, two height independent basic parameters were computed and analyzed: the refractivity at station height N0 and scale height Hs. These parameters can be used to calculate the refractivity profile. Using statistical tools as the moving average, the s0 parameter and the monthly mean values, together with the corresponding standard deviations, useful results were obtained for the variations of the refractivity with respect to observation hour, height, season, month, day and level.
Highlights
The troposphere is the lower region of Atmosphere and it extends from the earth’s surface to an altitude of about 10 km at the middle latitudes (6 km at the poles and up to 18 km at the equator)
These refractivity variations are responsible for various phenomena in the wave propagation, such as range and elevation angle errors in radar acquisition
It can be seen that in general, the refractivity increases from January to June, where it appears to reach a first peak
Summary
The troposphere is the lower region of Atmosphere and it extends from the earth’s surface to an altitude of about 10 km at the middle latitudes (6 km at the poles and up to 18 km at the equator). Propagation in the troposphere is affected by the variations of the refractive index with time and height. The data cover the period from 1991 to 1999 and the measured parameters are temperature, relative humidity and height at constant pressure levels.
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