The RED Experiment: An Assessment of Boundary Layer Effects in a Trade Winds Regime on Microwave and Infrared Propagation over the Sea

Abstract

The Rough Evaporation Duct experiment aimed to see if the effects of ocean waves account for errors in modeling the ranges at which radar and infrared can detect low-flying targets. When radars first came into operation during the late 1930s, they were not expected to detect targets much beyond the geometrical horizon. These early radars, operating at a wavelength of 13 m, generally met expectations. As new radars were rapidly developed, operating at shorter and shorter wavelengths for better target detection, observations of anomalous propagation effects became more frequent. When 10-cm radars were installed along the south coast of England during World War II, they were often able to see the coast of France, even though the coast was well beyond the geometric horizon (Booker 1948). These anomalous propagation effects also became more pronounced as the operating area became more tropical. For example, a 1.5-mwavelength radar operating in Bombay, India, re-

Brief review on PE method application to propagation channel modeling in sea environment

“…A general agreement between the measured and predicted field strength and a variety of atmospheric conditions [31]; some discrepancies are reported concerning the fading: the computed fading was not always as deep as the measured one [32]. Another experiment, the Rough Evaporation Duct (RED) experiment [92,93], specifically organized to investigate the effects of ocean waves on the meteorological parameters and, hence, on the evaporation duct, has provided also data for the validation of meteorological and propagation models designed for the marine surface layer. Measurements of microwave propagation loss under evaporation duct conditions were compared to prediction estimates based on the PE given by (1).…”

“…The adequacy of the PE method in modeling the radio wave propagation has been also extensively validated by means of comparisons to measured data [27,31,32,[89][90][91][92][93]. Both verification and validation refer to different inhomogeneous environments and a broad range of frequencies and propagation scenarios.…”

“…The surface roughness was modeled with Ament RRF (15) where σ ξ = 0 0051 2 , with the wind speed in m/s. For λ = 3 cm and a 25.7-km over-sea path (for details on the experiment see [93]) the mean and standard deviation of the difference between the observed and modeled propagation loss was −0.2 and 4.0 dB for a transmitter with = 13 m and 4.3, and 3.4 dB for a transmitter with = 5 m (receiver at 4.7 m). Similar results for the comparisons are reported for λ = 1 5 and 10 cm as well.…”

Physicochemical and Optical Characterization of Aerosol Fields from Coastal Breaking Waves

“…From our RED measurements we found that, depending upon conditions, the degradation in EO signal could be on the order of tens of percent at a wavelength of 4 µm (Anderson et al, submitted [7], Clarke et al, [8]). …”

“…SEAS [2][3][4][5] highlighted new approaches for calibration of lidars and to derive aerosol extinction values. RED aerosol data [7,8] allowed estimate the effect of coastal aerosol from breaking waves on visible and IR EO propagation.…”