Depolarization of radio waves by atmospheric hydrometeors in earth‐space paths: A review

Cox, D.C.

doi:10.1029/rs016i005p00781

Cited by 57 publications

(10 citation statements)

References 59 publications

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“…It should be mentioned here that, in this case, ice depolarization produced from the orientation of the ice crystals by the strong electrostatic fields in thunder-storms may be a serious problem. However, as reported by Cox [1981], between 10 and 30 GHz, rain depolarization appears to dominate the cumulative statistics in regions that experience the severe rain attenuation associated with thunderstorms. In Figures 8 and 9 the case of an earth-space link operated at 19 and 28 GHz and situated at Holmdel, New Jersey, is examined.…”

Section: It Is Evident Now That (1) Implies An Effective Pathmentioning

confidence: 74%

“…The elevation angle is 38.6 ø, and the polarization is 21 ø from the vertical. The experimental data have been taken by Cox [1981] and are referred to an annual length of measurements (April 18, 1977, to April 18, 1978. Similarly, in Figure 10 the case of an earth-space link operated at 11.7 GHz and situated at Blacksburg, Virginia, is analyzed.…”

Section: It Is Evident Now That (1) Implies An Effective Pathmentioning

confidence: 99%

See 1 more Smart Citation

A rigorous analysis for the study of rain attenuation and depolarization statistics for terrestrial and earth‐space links

Kanellopoulos¹

1983

Radio Science

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A well‐known rigorous technique proposed by Lin for predicting rain attenuation statistics for terrestrial links has been modified in order to apply it to 5‐min point rainfall long‐term distributions and to include the case of earth‐space links. This same technique leads to the construction of an effective predictive model for the rain depolarization statistics. Comparison of the so‐obtained theoretical results with experimental data has been quite encouraging.

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Section: It Is Evident Now That (1) Implies An Effective Pathmentioning

confidence: 74%

Section: It Is Evident Now That (1) Implies An Effective Pathmentioning

confidence: 99%

A rigorous analysis for the study of rain attenuation and depolarization statistics for terrestrial and earth‐space links

Kanellopoulos¹

1983

Radio Science

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“…Much of the relevant literature is summarized in a fine NASA handbook by Kaul et al (1980), and in a series of comprehensive review papers by Oguchi (1981), Fedi (1981), Brussaard (1981), Olsen (1981, and Cox (1981). The previously cited paper by Hogg and Chu (1975) is also most valuable.…”

Section: Earth To Spacementioning

confidence: 99%

The multiparameter remote measurement of rainfall

1984

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This paper is a critical survey of the measurement of rainfall by remote sensors. It is shown that single‐parameter radar rainfall measurements are limited because both reflectivity and rain rate are dependent on at least two parameters of the drop size distribution, viz., representative raindrop size and number concentration. Simulations are presented which use experimental raindrop size spectra and show the improvement in accuracy attainable through the use of combinations of two and three remote measurables. The spectrum of remote measurables is then reviewed. These include path integrated techniques of radiometry and of microwave and optical attenuation. A carefully designed short‐path microwave attenuation experiment which employs these techniques is sufficiently persuasive to show that the disappointing results achieved in many others was due largely to a combination of rain sampling problems and vertical air motions between the path and the gages. Other experiments reviewed show that when paths are colinear, attenuation deduced from radar and radiometry is in good agreement with that measured directly. Several dual‐wavelength radar methods are described which were aimed at improved measurements in small range increments but have produced generally disappointing results. However, when the total path attenuation estimated in this way, or by radiometry, is used as a constraint on the retrieval of rain profiles from the radar, the results are more promising. Selected experiments involving combinations of two or more of the three measurables, radar reflectivity Z, attenuation, and/or radiometry, show considerable promise when adequate account is taken of the sampling and air motion problems. The best results in gate‐by‐gate measurements have been achieved with dual polarization or differential reflectivity (ZDR). However, even these are subject to potentially large errors when the rainfall does not behave according to a priori assumptions embodied in the technique. An accompanying paper in this issue shows that the use of a third remote parameter in addition to Z and ZDR offers great promise. With a growing appreciation of the needs and the capabilities of the various techniques, the future of highly improved remote rainfall measurements seems bright.

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“…From these two dependencies, the elevation angle dependent term of the XPD-CPA relation is theoretically estimated as -40 log cos E 191. This was verified by comparing 19 results [3, [6][7][8][9][10][11][12][13][14][15], all for circular polarisation and frequencies near 12 GHz, but elevation angles varying from 3.2" to 49.5". For these data, the correlation coefficient between XPD and CPA was maximised for D = 40 dB, which is in agreement with the theoretical approximation.…”

Section: Measurementsmentioning

confidence: 69%

“…tested using the current measurement set, so a globally effective value of C was sought. The value of C was estimated by comparing 25 results [3, [6][7][8][9][10][11][12][13][14][15][16][17], all for circular polarisation and frequencies from 11.6 to 29.66 GHz. The dependence on elevation angle was compensated for.…”

Section: Measurementsmentioning

confidence: 99%

Depolarisation due to rain: the XPD-CPA relation

Kamp

IEEE Antennas and Propagation Society International Symposium. 1999 Digest. Held in Conjunction With: USNC/URSI National Radio

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INTRODUCTTONTheoretically as well as empirically, it has been shown that there is a certain correlation between depolarisation and attenuation due to rain. This relation provides a practical prediction tool for depolarisation. Using, for example, an equiprobability relation, depolarisation statistics may be derived from attenuation statistics. Furthermore, combined statistics of depolarisation and attenuation can be used to assess the margins of both parameters required for a certain system outage probability.Several theoretical and semi-empirical models for the relation between cross polarisation discrimination ('XPD') and copolar attenuation ('CPA') have been published, as well as many measurement results of this relation. In this paper, a large group of measurement results is used to assess all different dependencies of this relation empirically. EXLSTING MODELS OF THE XPD-CPA RELATIONDifferent experimenters have derived expressions for the relation between XPD and CPA [l-51.These expressions have been derived from calculations using different theories of E.M. wave scattering by the raindrops and using different models of raindrop size dishbution and raindrop shape and orientation. All models were formulated in the form of the expressionwhere f = frequency (GHz); 6 = polarisation angle (measured from the horizontal); q = temporal standard deviation of the canting angle of the medium ("); E = elevation angle; os = momentary spatial standard deviation of raindrop canting angles ("). Z(6,o,) (dB) is a polarisation dependent term, and S, C, D, and V (dB) are parameters which are different for each proposed model and depend on raindrop size distribution and raindrop shape model. S also depends on the effective path length through rain.In one of the models [3], a term "-0.075 COS*& cos26 CPA" was added to the expression in equation (l), to predict a difference between quasi-vertical and -horizontal polarisation, due to the different attenuation for polarisations aligned with the two mean symmetry axes of the raindrops. Because 6 is measured from the horizontal, this term is positive for quasi-vertical polarisations and negative for quasi-horizontal polarisation. MEASUREMENTSMeasurements of the relation between XPD and CPA have been performed at many sites [3,6-191. We extracted the results of these measurements from publications, by enlarging the paper copies and scanning the graphs by hand. Other results were extracted from the database 'DBSGS' of lTU-R. This way, we obtained a collection of 39 results of measurements at frequencies from 11.6 to 29.7 GHz, elevation angles from 3.2" to 49.5" and polarisation angles from 0" to 180' . including also measurements at circular polarisation, which is effectively equal to linear polarisation at 6 = 45". This collection of measurement results is used in this paper to validate the different dependencies of the prediction models of the XPD-CPA relation. In Figure 1, all results are plotted together in one graph.

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Depolarization of radio waves by atmospheric hydrometeors in earth‐space paths: A review

Cited by 57 publications

References 59 publications

A rigorous analysis for the study of rain attenuation and depolarization statistics for terrestrial and earth‐space links

A rigorous analysis for the study of rain attenuation and depolarization statistics for terrestrial and earth‐space links

The multiparameter remote measurement of rainfall

Depolarisation due to rain: the XPD-CPA relation

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