Modeling Atmospheric Effects on Over Land UHF Propagation Links

Abby Anderson, Christopher R. Anderson , and Henry S. Owen

Abstract:

Propagation modeling for over land paths has historically been performed using semi-empirical models. These models capture median propagation expected over a month or season but cannot model expected propagation for smaller time scales. Variability in atmospheric conditions, which influences radio frequency electromagnetic propagation, occurs on time scales of minutes to hours. Deterministic models, such as parabolic equation (PE) models, are required to accurately capture the effects of atmospheric variability on these timescales; however, they are typically used only in maritime environments. In this manuscript we evaluate the performance of a PE model for two over land propagation paths. Propagation measurement data and atmospheric model data were collected in July 2022 for 43.5 and 112 km UHF links. Ducting conditions are found to exist approximately 20% of the time. Evaluation of PE model output demonstrates accurate characterization of the measured ≈10 dB magnitude variability in received signal level.

Keywords: radio frequency; predictive models; time-frequency analysis; atmospheric measurements; atmospheric modeling; weather forecasting; UHF measurements

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