The Tropical Air–Sea Propagation Study (TAPS)

Abstract

The purpose of the Tropical Air–Sea Propagation Study (TAPS), which was conducted during November–December 2013, was to gather coordinated atmospheric and radio frequency (RF) data, offshore of northeastern Australia, in order to address the question of how well radio wave propagation can be predicted in a clear-air, tropical, littoral maritime environment. Spatiotemporal variations in vertical gradients of the conserved thermodynamic variables found in surface layers, mixing layers, and entrainment layers have the potential to bend or refract RF energy in directions that can either enhance or limit the intended function of an RF system. TAPS facilitated the collaboration of scientists and technologists from the United Kingdom, the United States, France, New Zealand, and Australia, bringing together expertise in boundary layer meteorology, mesoscale numerical weather prediction (NWP), and RF propagation. The focus of the study was on investigating for the first time in a tropical, littoral environment the i) refractivity structure in the marine and coastal inland boundary layers; ii) the spatial and temporal behavior of momentum, heat, and moisture fluxes; and iii) the ability of propagation models seeded with refractive index functions derived from blended NWP and surface-layer models to predict the propagation of radio wave signals of ultrahigh frequency (UHF; 300 MHz–3 GHz), super-high frequency (SHF; 3–30 GHz), and extremely high frequency (EHF; 30–300 GHz). Coordinated atmospheric and RF measurements were made using a small research aircraft, slow-ascent radiosondes, lidar, flux towers, a kitesonde, and land-based transmitters. The use of a ship as an RF-receiving platform facilitated variable-range RF links extending to distances of 80 km from the mainland. Four high-resolution NWP forecasting systems were employed to characterize environmental variability. This paper provides an overview of the TAPS experimental design and field campaign, including a description of the unique data that were collected, preliminary findings, and the envisaged interpretation of the results.

Impact of Radar Data Sampling on the Accuracy of Atmospheric Refractivity Inversions Over Marine Surfaces

“…The results of the Tropical Air-Sea Propagation Study and others show typical duct heights of 2-30 m (Ivanov et al, 2009;Kulessa et al, 2017;Wang et al, 2009) with long-term averages of 8 m in the northern latitudes and 30 m in the tropics (Hitney et al, 1985). The ranges of duct heights and M deficits associated with the trial parameters are consistent with the ranges observed in these studies.…”

“…The trial refractivity parameters used in this study ( c 0 , z d , and m 1 ; Table ) were selected based on the Saeger et al () study evaluating simplified evaporation duct models for inversion problems, as well as from evaluation of atmospheric data from the Tropical Air‐Sea Propagation Study (Kulessa et al, ). The results of the Tropical Air‐Sea Propagation Study and others show typical duct heights of 2–30 m (Ivanov et al, ; Kulessa et al, ; Wang et al, ) with long‐term averages of 8 m in the northern latitudes and 30 m in the tropics (Hitney et al, ). The ranges of duct heights and M deficits associated with the trial parameters are consistent with the ranges observed in these studies.…”

“…The trials are intended to encompass a range of realistic atmospheric conditions for testing the inversion process. The trial refractivity parameters used in this study (c 0 , z d , and m 1 ; Table 3) were selected based on the Saeger et al (2015) study evaluating simplified evaporation duct models for inversion problems, as well as from evaluation of atmospheric data from the Tropical Air-Sea Propagation Study (Kulessa et al, 2017).…”

Geostatistical Distribution of Vertical Refractivity Gradient Over Nigeria

“…Anomalous conditions can be classified into superrefraction, subrefraction, or ducting (trapping). Superrefraction, which is associated to subsidence, advection, or surface heating occurs when the atmospheric thermodynamic conditions cause the radio signals to refract much more than usual (Gunashekar, 2006; Kulessa et al, 2017). Subrefraction is a situation when the radio beam refracts less than usual, diminishing radio horizon, and its effects are less evident and occur less frequently, but it is relevant when correcting topographic beam blockage in radar rainfall estimation in complex terrain (Bech et al, 2007; Magaldi et al, 2016).…”

Anomalous tropospheric propagation: Usage possibilities and limitations in radar and wireless communications systems

“…Above mentioned models and tools are accompanied with increasing improvement in lower troposphere refractivity and sea state estimation/analysis in different area of the world and sophisticated refractive environmental modeling including inversion techniques [15][16][17][18][19]. In [18] are summarized the last 20 years field campaigns for data collection whereas [19] reviews previous work in estimating the atmospheric conditions from electromagnetic measurements which assures real-time tracking of atmospheric parameters.…”