Environmental characterization of the marine boundary layer for electromagnetic wave propagation

The propagation of IR radiation through the marine boundary layer is very much dependent on vertical temperature gradients. Due to the Air-Sea Temperature Difference (ASTD) the distance to the visible horizon for an imaging system can be shorter (ASTD < 0) or larger (ASTD > 0) than the distance to the geometric horizon. To analyse these phenomena FGAN-FOM took measurements in the mid and long wave IR. Location of the experiment was the Baltic Sea. A ship, equipped with IR point sources, was tracked while it was sailing in and out up to, and beyond, the horizon. Weather conditions during the measurement period showed interesting variations in ASTD and atmospheric turbulence (see paper 4884-11). Especially strong sub-refractive effects have been observed with ASTDs up to -5.0 °C. This paper deals with the analysis of the detection range of point targets under different meteorological conditions. Experimental results are compared with the propagation model IRBLEM (IR Boundary Layer Effects Model) which was developed by DRDC-RDDC -Valcartier, Canada.

Section: Introductionmentioning

confidence: 90%

“…A detailed description of meteorological conditions measured during the experiment is given in [3]. The frequency of occurrence of the ASTD throughout the measurements, is shown in Fig.…”

Section: Meteorologymentioning

confidence: 99%

See 1 more Smart Citation

IR propagation through the marine boundary layer: comparison of model and experimental data

Stein¹,

Polnau²,

Seiffer³

2003

“…To calculate the propagation factor for a given transmission geometry it is necessary to know the environmental parameters, namely the profiles of temperature, humidity and wind speed. During the measurements discussed here a thorough environmental characterization was performed, which is described in a separate paper [4]. Using this basis from which refractivity profiles and duct heights are derived, the propagation factors in dependence on height, which are relevant for the cases shown in paragraph 3, were calculated.…”

Section: Modelling Of Transmission Characteristicsmentioning

confidence: 99%

“…4 shows an overlay of RCS/range-plots for several outbound runs. The overlay plot shows that a great variety exists for different runs, which are related to different atmospheric conditions.…”

mentioning

confidence: 99%

Millimeterwave propagation within boundary layers over sea comparison of modelling and experimental data

Essen

Fuchs

2003

The performance of sensors operating within the marine boundary layer is severely influenced by the actual atmospheric conditions and the sea surface. Propagation models are in existence, which cope with the varying environment and allow a performance prediction for sensors in different bands of the electromagnetic spectrum. Model calculations give evidence for a complementary performance of sensors operating in the IR region and at millimeterwaves (35/94 GHz). To validate existing radar propagation models like TERPEM and to compare IR and mm-wave propagation over sea under various atmospherical conditions, joint experiments were conducted over transmission ranges well beyond the horizon, assisted by a careful characterization of the environment. This paper describes the experimental approach and gives representative results for measurement and simulation. The implications on performance especially for a multispectral (IR/mmW) approach are discussed.

Simultaneous characterization of propagation within the marine boundary layer at X-, Ka- and W-band

Essen

Fuchs

Foerster³

2004

Self Cite

The performance of radar sensors operating within the marine boundary layer is severely influenced by the actual atmospheric conditions, the sea surface and the geometry between radar and reflection point. Propagation models are in existence, which cope with the varying environment and allow a performance prediction for sensors in different radar bands. To assess the propagation within different layers simultaneously at X-, Ka- and W-band an experiment was performed using the experimental three frequency radar MEMPHIS operating against point targets at different heights above sea, carried on a naval vessel, which moved on outbound and inbound courses to ranges well beyond horizon. In-situ measurements included recordings of atmospheric properties and sea surface parameters. Based upon the environmental measurements, refractivity profiles were calculated. With the help of the vertical refractivity gradient and the air sea temperature difference, conditions for the radar propagation were determined.The experimental results were used to validate respective simulations with the parabolic equation model TERPEM. In conclusion, the experimental results and calculations underline the importance of the environmental characterization of the marine boundary layer with high temporal and spatial resolution.This paper describes the experimental approach and gives representative results for measurement and simulation