Abstract
[1] This paper presents long‐term statistics additional to those previously published pertaining to evaporation duct propagation of UHF radio waves in the British Channel Islands, with particular focus on a completely over‐sea 50 km transhorizon path. The importance of the evaporation duct as an anomalous propagation mechanism in marine and coastal regions is highlighted. In particular, the influence of various atmospheric parameters on the performance of a popular operational evaporation duct model is examined. The strengths and weaknesses of this model are evaluated under specific atmospheric conditions. The relationship between the continually varying evaporation duct height and transmitter‐receiver antenna geometries is analyzed, and a range of statistics related to the implications of this relationship on the received signal strength is presented. The various issues under investigation are of direct relevance in the planning of long‐range, over‐sea radio systems operating in the UHF band, and have implications for the radio regulatory work carried out by organizations such as the International Telecommunication Union. Citation: Gunashekar, S. D., E. M. Warrington, and D. R. Siddle (2010), Long‐term statistics related to evaporation duct propagation of 2 GHz radio waves in the English Channel, Radio Sci., 45, RS6010, doi:10.1029/2009RS004339.
Highlights
0.52 to the parabolic equation (PE) method [Dockery, 1988; Barrios, 1994; Levy, 2000], and the results indicated a very good agreement between the measured and predicted signal strengths during periods of normal reception
The various issues under investigation in this long‐term study are of direct relevance in the planning of over‐sea communication links operating in the UHF band, and have implications for the radio regulatory work carried out by organizations such as the International Telecommunication Union and Ofcom (UK)
For 2 years of data corresponding to periods of normal reception, a strongly unstable atmosphere (ASTD ≤ −1°C) with wind speeds exceeding 10 m s−1 resulted in the highest correlation coefficient (0.76) between the observed and predicted signal strengths
Summary
[2] When considering over‐sea propagation within the UHF band and above, the most common type of nonstandard propagation mechanism that can result in radio waves traveling to beyond line‐of‐sight distances is the evaporation duct [Hitney et al, 1985; Paulus, 1985; Hitney and Veith, 1990; Babin et al, 1997; Space and Naval Warfare Systems Command (SPAWAR), 2008]. Confirmation of the Assumption of Horizontal Homogeneity [7] In order to ascertain that the utilization of meteorological data from the Channel Light Vessel is appropriate for the three radio links under consideration, data from two nearby lightships in the English Channel were compared to the weather data from the CLV. 4. Observations and Analysis [9] It has been reported previously by Siddle et al [2007] and Gunashekar et al [2007a] that there are possibly two distinct propagation mechanisms operating on the transhorizon over‐sea radio link between Jersey and Alderney: evaporation ducting and diffraction for majority of the time (classified as periods of normal reception), and higher‐altitude superrefractive/ducting structures for a small fraction of the time during which significant field strength enhancements occurred The P‐J evaporation duct refractivity profiles (obtained using meteorological data from the CLV) were utilized as inputs
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