Anomalous transhorizon propagation and meteorological processes of a multilink path

Abstract

An event‐based approach is developed and applied to 3 years of data of a four link transhorizon path over the English Channel (La Manche). The signal enhancements (events) observed on the chart recordings during anomalous propagation are selected and, according to their dynamical signatures, categorized into three main patterns of ducting, layer reflection, and high k factor diffraction. The statistical analysis carried out on this event basis gives the correlation between the signal levels of different links and the cross correlation between signal levels and local N index derived from surface meteorological monitoring. The results reveal the fundamental properties of the anomalous propagation regimes. Using case studies of several interesting events, the meteorological processes and resultant impact on transhorizon transmission are also explained. This extensive work contributes to a better understanding of anomalous propagation mechanisms present in transhorizon links.

Determination of the effective earth radius factor and its impact on propagation of signals on over-sea paths in the English Channel

“…Shen and Vilar, in their study on over-sea propagation, identified typical features of signal received due to each type of propagation mechanism [9]. A comparison of enhanced signal strength events with this study indicated that most of the enhancement events were a likely result of ducting.…”

C band transhorizon signal characterisations in evaporation duct propagation environment over Bohai Sea of China

“…As Gunashekar et al [6] and other researchers [4,8,10,27] point out, diffraction, tropospheric duct and tropospheric scatter are the main modes of microwave transhorizon transmission. In reality, which mode plays a leading role depends on the meteorological conditions, signal frequency, transmission distance and geomorphology, and so on.…”

“…However, energy at lower [29], respectively frequencies or transmissions outside the duct may be less affected. From (7) and (8), it can be seen that the weaker duct strength results in the stronger trapping capability; even the duct height is the same value. Thus, the higher air-sea temperature difference and the nearly neutral or stable atmospheric conditions correspond to the stronger signal strength.…”

“…These experiments indicate that microwave signals can propagate beyond the line of sight, especially in the marine atmospheric environment. At present, the transhorizon propagation is mainly attributed to tropospheric scatter, ducting, spherical diffraction, layer reflection, and sometimes rain scatters [7][8][9][10]. The transhorizon channel may have different characteristics as the dominant propagation mechanism varies under various meteorological conditions.…”

“…In order to analyse the effects of the evaporation duct on radar or communications, some models, such as AREPS and tropospheric electromagnetic parabolic equation routine [19], are used to predict the radio wave propagation characteristics. Meanwhile, some transhorizon propagation measurements have been made to obtain the signal strength (path loss) and to compare with the model predictions [1,2,5,6,8,9,16]. Normally, the measurements are in accord with the models.…”