Three years of C band signal measurements for overwater, line‐of‐sight links in the mid‐Atlantic coast: 1. Fade statistics

Goldhirsh, J.; Dockery, G. Daniel; Musiani, B.H.

doi:10.1029/94rs01349

Cited by 8 publications

(3 citation statements)

References 6 publications

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“…During some of these Wallops Island measurements, microwave measurements were available from a nearby over-the-water transmission link described by Goldhirsh et al (1994). Under certain conditions, it is possible to determine evaporation duct height from this microwave data.…”

Section: Measurement Methodsmentioning

confidence: 99%

“…This link is described in more detail in Goldhirsh et al (1994) and provides two line-of-sight over-the-water microwave links. Because the transmitted signal power is known, the fade in the received signal can be determined for each receiver.…”

Section: B Independent Duct Height Determinationsmentioning

confidence: 99%

“…By running the TEMPER electromagnetic propagation model (Dockery 1988), Goldhirsh et al (1993) derived fade measurements for normal refraction with a superimposed evaporation duct at different heights. Time series fade measurements for each of the two receivers can then be examined to see how they compare to these simulations for the different evaporation duct heights.…”

Section: B Independent Duct Height Determinationsmentioning

confidence: 99%

See 2 more Smart Citations

A New Model of the Oceanic Evaporation Duct

Babin¹,

Young²,

Carton³

1997

J. Appl. Meteor.

166

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Failure to consider anomalous propagation of microwave radiation in the troposphere may result in erroneous meteorological radar measurements. The most commonly occurring anomalous propagation phenomenon over the ocean is the evaporation duct. The height of this duct is dependent on atmospheric variables and is a major input to microwave propagation prediction models. This evaporation duct height is determined from an evaporation duct model using bulk measurements. Two current evaporation duct models in widespread operational use are examined. We propose and test a new model that addresses deficiencies in these two models. The new model uses recently refined bulk similarity expressions developed for the determination of the ocean surface energy budget in the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment.Comparison of these models is made using data collected from a boat off Wallops Island, Virginia, during a range of seasons and weather conditions and from the tidal Potomac River during June and August. Independent evaporation duct height determinations are made using profile measurements from the same boat and are corroborated with fade measurements made with a nearby microwave link whenever possible. The proposed model performs better than the other (operational) models for the cases examined and has advantages of internal consistency.

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Section: Measurement Methodsmentioning

confidence: 99%

Section: B Independent Duct Height Determinationsmentioning

confidence: 99%

Section: B Independent Duct Height Determinationsmentioning

confidence: 99%

See 1 more Smart Citation

A New Model of the Oceanic Evaporation Duct

Babin¹,

Young²,

Carton³

1997

J. Appl. Meteor.

166

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Signal level statistics and case studies for an over‐the‐horizon mid‐Atlantic coastal link operating at C‐band

Goldhirsh¹,

Musiani²

1999

Radio Science

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Abstract. We examine the results of 1 year of near-continuous measurements for a 128-km over-the-horizon C-band coastal propagation link. The link extends between Dam Neck, Virginia (16 km south of Virginia Beach), and Wallops Island, Virginia (approximately 150 km southeast of Washington, D.C.). The objectives of this effort are to explore the different mechanisms of propagation through an analysis of several case studies and to assess the statistical connectivity over the 1-year period. Case studies involving the linking of environmental information and measured signal levels are analyzed. Propagation factor levels due to evaporation ducts, surface ducts, and scattering from irregularities of the refractive index in the common volume are determined. Cumulative distributions of the measured propagation factor for the annual, fall-winter, and spring-summer periods are presented. Conditional and absolute distributions of propagation factor time durations are also presented and analyzed. It is demonstrated that during the spring-summer period, received signal levels were consistent with ducting and not with troposcatter. The fall-winter levels may be due to troposcatter from irregularities of the refractive index. The months giving the smallest and largest propagation factors were January and June, respectively. IntroductionThere is a continuing need to better understand the propagation conditions associated with ship-to-ship and ship-to-shore communications and radar opera-

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K factor statistics for subrefraction in the mid‐Atlantic coast of the United States

Goldhirsh¹,

Dockery²

2001

Radio Science

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Abstract. Statistics of "equivalent K factor" are derived for the mid-Atlantic coast of the United States. These statistics are associated with subrefraction using 3 years of nearcontinuous line-of-sight link signal measurements at 4.7 GHz in the mid-Atlantic coast of the United States. Probabilities are derived for a family of threshold levels of K factors ranging from 0.6 to 1.0 which are sustained over durations exceeding 1-5 hours. An analytical model is derived that characterizes this family of curves with excellent accuracy. It is, for example, demonstrated that for 6% of the average year the K factor is smaller than 1 for durations greater than 1 hour in the mid-Atlantic coast of the United States. Caveats that should be considered in applying these results are reviewed. Monthly probabilities of K factor statistics reveal that the winter and early spring months dominate. For example, during February of year 1 and December of years 2 and 3 the K factors were smaller than 0.8 for periods exceeding 2 hours at the probabilities of 11.5%, 12.0%, and 11.5%, respectively. This result is consistent with the fact that cold water conditions and warm overlying moist air are more prevalent during the winter season. These conditions represent the correct meteorological ingredients for extreme subrefraction to occur. Annually, the K factor was smaller than 0.8 with durations greater than 1 hour at a probability of 3.2%. The bending effects of propagating rays may be partially accounted for by replacing the Earth's radius "a" by an effective radius "Ka," where K (hereinafter called the K factor) is a constant that may be smaller or greater than 1. This concept was first introduced by Schelling et al. [1933] and was expanded by Lagrone [1960], who showed 5 year averages of "K factor" isopleths for the winter and summer months throughout the United States. These contours were derived from averaged radiosonde measurements over the first 300 rn from the surface. The use of a K factor, such as K = 4/3, which is referred to as a "standard propagation condition," implies a particular rate of decrease of refractivity with height for all altitudes. For K = 4/3, this rate is approximately -40 N units 1425

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Three years of C band signal measurements for overwater, line‐of‐sight links in the mid‐Atlantic coast: 1. Fade statistics

Cited by 8 publications

References 6 publications

A New Model of the Oceanic Evaporation Duct

A New Model of the Oceanic Evaporation Duct

Signal level statistics and case studies for an over‐the‐horizon mid‐Atlantic coastal link operating at C‐band

K factor statistics for subrefraction in the mid‐Atlantic coast of the United States

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