Oceanic propagation measurement in the Northern part of the South China Sea

Abstract

The distance of conventional X-band microwave propagation over the sea surface is within 'radio line-of-sight' (RLOS) which limits its application in long-range land-buoy communication. To overcome the above limitation, evaporation duct (EVD) is employed as an alternative to the physical channel in the land-buoy communication and the corresponding communication distance could be extended to hundreds of kilometers. To explore the effects of EVD channels on communication signaling, an over-the-sea trans-horizon propagation experiment was conducted in the northern part of the South China Sea. The statistical features of the received signal level (RSL), e.g. median, fading range, and probability density function (PDF), are reported. Moreover, the influence of sea surface wind speed and the height of the receiving terminals on RSL fluctuation are also discussed. Finally, Some conclusions are given.

Statistical Analysis of the Quantified Relationship between Evaporation Duct and Oceanic Evaporation for Unstable Conditions

“…The evaporation duct is primarily affected by four environmental factors: near-surface wind speed, air temperature, SST, and relative humidity (Ramsaur 2009;McKeon 2013). The response of the EDH to variations in these factors is dependent on the thermodynamic atmospheric state, which is characterized by the air-sea temperature difference (ASTD) (Zhang et al 2016a). Positive, zero, and negative values of ASTD (8C) roughly correspond to stable, neutral, and unstable conditions, respectively.…”

“…This dataset covers a 32-yr period from 1979 to 2010, and so our analysis is also limited to this period. The reliability and suitability of the NCEP CFSR dataset for the evaporation duct and evaporation research have been discussed fully in several previously published works (Yang et al 2009;Ramsaur 2009;McKeon 2013;Shi et al 2015c;Zhang et al 2016a;Yang et al 2016).…”

“…If the gradient extends sufficiently high (always within a few tens of meters), an anomalous atmospheric structure forms in which the propagation of electromagnetic waves is similar as when trapped in a waveguide. This kind of structure is known as the evaporation duct, and the relevant anomalous effectknown as ducting-can significantly affect radio systems, especially those working at the microwave band (Brooks 2001;Shi et al 2015a,b;Lentini and Hackett 2015;Zhang et al 2016b;Fountoulakis and Earls 2016;Kang and Wang 2016).…”

“…To derive these profiles, the Monin-Obukhov similarity theory and the Liu-Katsaros-Businger theory are employed, combined with meteorological parameters [air temperature (2 m), sea surface temperature (SST), relative humidity (2 m), wind speed (10 m), and sea level pressure] (Babin and Dockery 2002;Frederickson et al 2000). For brevity, the computational procedures for the EDH are omitted here; for more details, please refer to our previous works (Yang et al 2009;Shi et al 2015c;Zhang et al 2016a;Yang et al 2016). A detailed flowchart of the procedures can be found in Yang et al (2017b).…”

Study on evaporation duct estimation from point‐to‐point propagation measurements

“…In the tropospheric microwave propagation, the refractive properties of the atmosphere influence the performance of the radio systems [1,2]. The atmospheric refractive index is usually presented in terms of modified refractivity defined by M = 10 6 × (n + z/R e − 1), where n is the refractive index, z is the height above earth and R e is the radius of the Earth [3].…”