Yes / In this communication, nine years of local radiosonde meteorological data, from 1997 to 2005, have been used to calculate the vertical refractivity gradient, ΔN, in the lowest atmospheric layer above the ground surface. The values obtained are used to estimate the parameter β0, which represents the probability of non-standard propagation. Hourly, monthly and yearly distributions of ΔN in the first 100 meters above the ground are given. Monthly and yearly variations of the mean of ΔN and β0 are provided and the β0 values are compared with the ITU maps.

Yes / A new simplified approach is proposed to evaluate the vertical refractivity profile within the lowest 1 km of atmosphere from the analysis of surface refractivity, Ns, in areas where upper air data are not available. Upper-air measurements from the nearest available radiosonde location with similar surface profile to these sites are utilized. The profiles of Ns and refractivity extrapolated to sea level, No, obtained from surface meteorological data using both fixed stations and radiosonde are investigated and compared. Vertical refractivity gradient, ΔN, is evaluated at three atmospheric layer heights within the first kilometer above the ground in addition to propagation parameters relevant to each atmospheric layer. At six sites, different approaches are compared for the analysis of three important parameters; namely effective earth radius factor, k, anomalous propagation probability parameter, β0, and point refractivity gradient at 65 m not exceeded for 1% of time, dN1. The k-factor parameter is investigated using a new weighted average approach of ΔN at 65 m, 100 m and 1 km layers above the ground. The results are compared with the latest ITU maps and tables for the same area.