Yes / In this paper, local meteorological data for a period of 35 years (from 1979 to 2013) from Kuujuaq station have been used to calculate the surface refractivity, N and to estimate the vertical refractivity gradient, dN1, in the lowest atmospheric layer above the ground. Monthly and yearly variations of the mean of N and dN1 are provided. The values obtained are compared with the corresponding values from the ITU maps. The long-term trend of the surface refractivity is also investigated. The data demonstrate that the indices N and dN1 are subject to an evolution which may have significance in the context of climate change (CC). Monthly means of N show an increasing departure from ITU-R values since 1990. Yearly mean values of the dN1 show a progressive decrease over the period of study. Seasonal means of dN1 show a decrease over time, especially for summer. Such a trend may increase the occurrence of super-refraction. However, currently available ITU-R recommendations for microwave link design assume a stationary climate, so there is a need for a new modelling approach.

No description available.

M.Sc. (Geography) / In this study the spatial and temporal variation of radio-refractivity over southern Africa is investigated. Climatological data from 8 upper-air stations and 49 surface stations were used and transformed. into values of refractivity to establish a data base of radio refractivity information. The spatial analysis yielded maps of surface refractivity (Ns ) and height corrected surface refractivity (No) for southern Africa. In order to calculate the height correction factors, a radio-climatological classification of southern Africa was drawn: up. These maps are a refinement of the existing maps published by the CSIR. The temporal analysis consisted of graphs of mean monthly and yearly values of various refractivity- (Ns, Delta N, K-factor) and climatological (temperature, vapour pressure) factors for the eight upper-air stations. Some preliminary information about ducting was also obtained from this analysis. A spatial-temporal analysis of limited extent was then performed for one station to obtain an indication of the factors leading to the formation of radio ducts, as well as the actual variation of refractivity with height. Information about the variation of refractivity over southern Africa was thus obtained, with emphasis on macroscale variation as well as preliminary information about ducting conditions.

Thesis (M.Sc.)--University of Melbourne, Dept. of Science, 1974. / Typescript (roneo copy). Includes bibliographical references (leaves 104-105).

Thesis (M.S.)--Florida State University, 2005. / Advisor: Dr. Xiaolei Zou, Florida State University, College of Arts and Sciences, Dept. of Meteorology. Title and description from dissertation home page (viewed Sept. 29, 2005). Document formatted into pages; contains xvi, 119 pages. Includes bibliographical references.

No / In this paper, the seasonal variations of vertical refractivity gradients and statistics of anomalous Refractive Conditions in the United Arab Emirates (UAE) have been analyzed. Nine years of local radiosonde meteorological data, from 1997 to 2005, for the lowest atmospheric layer above the ground surface have been used. Monthly variations and cumulative distributions of refractivity gradients in the first 100 meters of the atmosphere are presented.

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.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND LINDGREN. / Includes bibliographical references. / by Joel Berman. / M.S.

In this paper, a set of local radiosonde meteorological data, from 1990 to 2005, have been used to statistically analyze the refractivity gradient, DeltaN, at the lowest 65 m, 100 m and 1 km of the atmosphere above the surface of the Earth in the Gulf region. These three levels are the reference atmospheric layers in which the refractivity gradients have been evaluated by the ITU-R Recommendations P.453-10 and P.452-12The vertical variations of the refractivity profile aredisplayed through the cumulative distributions of the refractivity gradients at the targeted levels. The obtained results are compared for the three layers and also compared with the estimated values in the ITU maps and tables when available. Index Terms – Atmospheric refraction, Refractivity gradient.