A Model of the Zenith Excess Attenuation Due to the Melting Layer

Zhang, W; Salonen, E.; Karhu, S.

doi:10.1109/euma.1991.336514

Cited by 3 publications

(5 citation statements)

References 10 publications

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“…7 to a stratiform rain by calculating the sum of the additional zenith attenuation and rain zenith attenuation. The additional attenuation was also termed the excess attenuation due to the melting layer in the literature, e.g., in [7] and [8].…”

Section: In the Melting Layermentioning

confidence: 99%

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Predictions of radiowave attenuations due to a melting layer of precipitation

Zhang¹,

Karhu²,

Salonen³

1994

IEEE Trans. Antennas Propagat.

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Abstruct-A melting layer model related to the physical constants and meteorological parameters is employed in this investigation. The specific phase shift, together with the specific attenuation, is computed at 1-100 GHz by using the Mie theory. The additional zenith attenuation, which is the difference between zenith attenuation due to the melting layer and attenuation due to the same thickness of the resulting rain, is comprehensively studied. The ratio of the difference to rain zenith attenuation may be over 1 at 1-5 GHz although the difference is much less than 1 dB. The difference can be over 1 dB at frequencies above 20 GHz. A minimum of the ratio is below 0.05 at frequencies about 40-60 GHz but the ratio can become a value of about 0.1 at 100 GHz. The additional attenuation should be taken into account in satellite-earth communications and radar remote sensing. The power law parameters of the average specific attenuation of the melting layer and rain specific attenuation are tabulated for three raindrop size distributions at rain rates of below 25 mm/h. The power law method could be utilized in the additional attenuation calculation. It is a good approximation of the Mie theory results at 1-50 GHz and a useful estimate at 50-100 GHz.

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Section: In the Melting Layermentioning

confidence: 99%

“…The ratio of the additional zenith attenuation to rain zenith attenuation is shown at 1-100 GHz. It is suggested in Section V that the power law [8], [ 101 method be utilized in the additional attenuation calculation. The power law parameters are tabulated for three raindrop size distributions at rain rates below 25 mm/h.…”

Section: Introductionmentioning

confidence: 99%

Predictions of radiowave attenuations due to a melting layer of precipitation

Zhang¹,

Karhu²,

Salonen³

1994

IEEE Trans. Antennas Propagat.

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“…Helsinki University of Technology and Finnish Meteorological Institute have made a very comprehensive study of attenuation effects of oxygen, watervapour, clouds, rain, melting layer and scintillation at frequencies from 10 to 57 GHz for ESA [7,8,9,10,11,12].…”

Section: Satellite Communicationsmentioning

confidence: 99%

Research and New Developments in Microwave Communications in Finland

Santomaa

1992

22nd European Microwave Conference, 1992

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Finland has long traditions in microwave technology and techniques. The first development work was a 8 channel radiolink for 7 GHz in 1948. After that many radars, radiolinks, radiometers, radio astronomy receivers, satellite receivers and antennas have been developed.The main subjects covered are wave propagation-studies, radiolinks and satellite and land mobile communications terminals including antennas. Also a short overview of developments on MMIC technology is given.

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“…The precipitation effects, scattering and attenuation, often cause problems [1][2][3][4][5] in the satellite-earth links. The effects of rain, especially rain scattering [6] in the forward and backward directions [7], have been investigating by several researchers.…”

Section: Introductionmentioning

confidence: 99%

“…The Nordic countries, however, are suffering from other types of precipitation beside the rain. References [4,5,8] discuss the effects of the melting layer of precipitation. Some general discussions have also been presented on hail and sleet, but it is still necessary to develop a theoretical model.…”

mentioning

confidence: 99%

Scattering by Hail and Sleet Particles at Microwave and Millimeter Wave Frequencies

Zhang¹

1992

22nd European Microwave Conference, 1992

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Scattering by hail and sleet particles, prolate and oblate spheroids with axial ratios up to 1.8, is considered using the point matching technique. For computing, the truncated modal index and the recurrence relations are discussed. Numerical results, at 30 and 100 GHz, show that the extinction cross sections of the hail particles oscillate around twice the geometrical cross sections of the particles in the resonance region. It is found that the bistatic scattering and the back scattering depend strongly on the material components of the particles. The effects of the particle shape on the extinction cross section, the bistatic scattering cross section and the radar back scattering cross section are shown. INTRODUCTIONThe precipitation effects, scattering and attenuation, often cause problems [1][2][3][4][5] in the satellite-earth links. The effects of rain, especially rain scattering [6] in the forward and backward directions [7], have been investigating by several researchers. The Nordic countries, however, are suffering from other types of precipitation beside the rain. References [4,5,8] discuss the effects of the melting layer of precipitation. Some general discussions have also been presented on hail and sleet, but it is still necessary to develop a theoretical model. The Olympus beacons provide now a possibility to measure the attenuation and depolarization caused by hail and sleet. Now, the first stage of developing the theoretical model has been made.. The shape of hail and sleet particles is approximated to a spheroid. Because of the truncated modal index and the recurrence relations working likely, the fine computing of the extinction cross section, the bistatic scattering cross section and the radar back scattering cross section can be performed at 1-100 GHz by using the point matching technique [1]. The salient points of the computing, together with numerical results at 30 and 100 GHz are presented here. SCATTERING CROSS SECTIONS Consider, a hail or sleet particle is illuminated by a plane wave as shown in Fig 1. The scattered field can be expanded into a double series in terms of the spherical vector wave functions with the expansion coefficients found by the point matching technique [1]. The vector scattering amplitude, resulted from the scattered far field approximation, is also a double series in terms of the spherical harmonics [9] which are functions of the angles (9, 4) on the surface of a sphere. Based upon the vector scattering amplitude, the extinction cross section oe,, the bistatic scattering cross section 0rji (j refers to the received polarization while i refers to the incident one), and the radar back scattering cross section crb can be obtained. Symmetrical semiaxis a and the incident wave direction ki define the incident plane, while the scattering plane is determined by the incident wave direction k, and the scattering direction k,. The scattering angle, vertical incidence and side incidence are also shown in Fig 1. Vertical polarization, v, and horizontal polarization, h, are connec...

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A Model of the Zenith Excess Attenuation Due to the Melting Layer

Cited by 3 publications

References 10 publications

Predictions of radiowave attenuations due to a melting layer of precipitation

Predictions of radiowave attenuations due to a melting layer of precipitation

Research and New Developments in Microwave Communications in Finland

Scattering by Hail and Sleet Particles at Microwave and Millimeter Wave Frequencies

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