scholarly journals Radio Echo Sounding: Absorption and Scattering by Water Inclusion and Ice Lenses

1972 ◽  
Vol 11 (61) ◽  
pp. 133-146 ◽  
Author(s):  
B. M. Ewen Smith ◽  
S. Evans
Keyword(s):  
Sea Water ◽  
Radio Waves ◽  
Scattered Power ◽  
Glacier Melt ◽  
Naturally Occurring ◽  
Water Layers ◽  
Melt Water ◽  
Radio Echo Sounding ◽  
Radio Wavelength ◽  
Water Inclusion

AbstractThe absorption of radio waves propagating through naturally occurring waters varies greatly with the electrical conductivity. Glacier melt water is very transparent and the attenuation by melt water layers is due to reflexion of power, whereas the attenuation of sea-water layers is due to absorption. The attenuation of soaked firn is usually prohibitive if the liquid is brine but it should not be a serious obstacle to radio echo strength if the liquid is rain-water or melt water. However, the magnitude of the scattered power can become greater than that from continuous (bedrock) reflectors if the size of the irregularities in the medium is large (approaching the radio wavelength in ice). Echo power formulae show that ice lenses may have the most serious effect and that low radio frequencies will be necessary to combat this.

Radio Echo Sounding: Absorption and Scattering by Water Inclusion and Ice Lenses

1972 ◽  
Vol 11 (61) ◽  
pp. 133-146 ◽  
Author(s):  
B. M. Ewen Smith ◽  
S. Evans
Keyword(s):  
Sea Water ◽  
Radio Waves ◽  
Scattered Power ◽  
Glacier Melt ◽  
Naturally Occurring ◽  
Water Layers ◽  
Melt Water ◽  
Radio Echo Sounding ◽  
Radio Wavelength ◽  
Water Inclusion

Abstract The absorption of radio waves propagating through naturally occurring waters varies greatly with the electrical conductivity. Glacier melt water is very transparent and the attenuation by melt water layers is due to reflexion of power, whereas the attenuation of sea-water layers is due to absorption. The attenuation of soaked firn is usually prohibitive if the liquid is brine but it should not be a serious obstacle to radio echo strength if the liquid is rain-water or melt water. However, the magnitude of the scattered power can become greater than that from continuous (bedrock) reflectors if the size of the irregularities in the medium is large (approaching the radio wavelength in ice). Echo power formulae show that ice lenses may have the most serious effect and that low radio frequencies will be necessary to combat this.

scholarly journals CHARACTERISTICS OF UHF WAVES DISTRIBUTION IN LAND AND WATER SURFACE TROPOSPHERIC WAVEGUIDE

2019 ◽  
pp. 115-121
Author(s):  
Oxana Vladimirovna Kalambatskaya ◽  
Oleg Nickolaevich Pishchin
Keyword(s):  
Communication Systems ◽  
Water Surface ◽  
Sea Water ◽  
Systems Design ◽  
Cellular Communication ◽  
Effect Of Temperature ◽  
Radio Waves ◽  
Wave Direction ◽  
Surface Atmospheric Layer ◽  
Cellular Communication Systems

The article considers examples of ultra-long propagation of UHF radio waves in mobile cellular communication systems. The phenomena are mainly observed in the Astrakhan region in the spring-summer period (May-June) and are presumably associated with sharp seasonal changes of air temperature followed by rains. The effect of temperature inversion results in changing the refraction index in the surface layer and, as a result, in changing the wave direction as the effect of superrefraction in the surface atmospheric layer. The properties of radio waves in their propagation in the land and sea-water surface waveguide are investigated. The values of the heights of land and sea-water surface tropospheric waveguides for cellular communication systems of different ranges are obtained. The features of existing of tropospheric land and sea-water surface tropospheric waveguides are described. The need to use their properties in the mobile communication systems design is stated.

scholarly journals Radio Echo Sounding on a Valley Glacier in East Greenland

1973 ◽  
Vol 12 (64) ◽  
pp. 87-91 ◽  
Author(s):  
J. L. Davis ◽  
J. S. Halliday ◽  
K. J. Miller
Keyword(s):  
The Arctic ◽  
Radio Waves ◽  
Polar Ice ◽  
East Greenland ◽  
High Attenuation ◽  
Valley Glacier ◽  
Radio Echo Sounding ◽  
Improved Performance ◽  
Temperature Water ◽  
Echo Sounding

AbstractAlthough radio echo sounding equipment has been used with success for measuring the thickness of ice sheets in the Arctic and Antarctic, a valley glacier poses the additional problems of echoes from the valley walls, which may obscure the bottom echoes, and a high attenuation of radio waves in the ice. During July and August 1970, a study was carried out on Roslin Gletscher in Stauning Alper, East Greenland, to investigate the problems of radio echo sounding on a valley glacier. Results show that reflections from the valley walls are minimized by using sufficiently directional antennae, but attenuation of the signal in the ice is higher than that in polar ice at the same temperature. Water in and on the ice probably accounts for much of the attenuation, and the use of a lower frequency or measurements before the melt commences should give improved performance.

scholarly journals Depolarization of Radio Waves can Distinguish between Floating and Grounded Ice Sheets

1979 ◽  
Vol 23 (89) ◽  
pp. 223-232 ◽  
Author(s):  
A. H. W. Woodruff ◽  
C. S. M. Doake
Keyword(s):  
Electrical Properties ◽  
Crystal Orientation ◽  
Ice Sheets ◽  
Large Change ◽  
Radio Waves ◽  
Polar Ice ◽  
Ice Shelf ◽  
Radio Echo Sounding ◽  
Polarization Behaviour ◽  
Hinge Zone

Abstract Polar ice is now thought to be marginally birefringent at radio echo-sounding frequencies. An experiment on the polarization behaviour of 60 MHz radio echoes from the bed of both ice shelf and land ice in Antarctica showed a marked difference in the returned polarization. It appears that differences in electrical properties or roughness of the reflecting boundary cannot explain our results. We suggest that there is a large change in the birefringence of the ice sheet at the hinge zone, caused by the effect of tidal strain on crystal orientation. This would imply a minimum value of the radio-frequency anisotropy in permittivity for the single crystal of (0.52±0.8)%. Therefore polarization changes could allow floating and grounded ice to be distinguished.

scholarly journals Remote-Sensing Studies of Kvitøyjøkulen, an Ice Cap on Kvitøya, North-East Svalbard

1990 ◽  
Vol 36 (122) ◽  
pp. 75-81
Author(s):  
Jonathan L. Bamber ◽  
Julian A. Dowdeswell
Keyword(s):  
Landsat Imagery ◽  
Ice Core ◽  
Geographical Location ◽  
Climatic Conditions ◽  
Radio Waves ◽  
Anthropogenic Contamination ◽  
Ice Cap ◽  
North East ◽  
Radio Echo Sounding ◽  
Basal Melting

AbstractAirborne 60 MHz radio echo-sounding data were collected over 250 km of flight track from an ice cap (Kvitøyjøkulen) on Kvitøya in north-eastern Svalbard. These were combined with Landsat imagery to provide ice-surface and bed topographic information and inferences about the thermal and climatic conditions on the ice cap. Quantitative analysis of radio-echo strength measurements and the existence of offshore plumes of sediment-laden melt water indicate significant basal melting and a warmer thermal regime than would be expected from the geographical location of the ice cap. Analysis of the dielectric absorption of radio waves by the ice and data from a recently recovered ice core from a neighbouring ice cap (Austfonna) suggest considerable anthropogenic contamination of the precipitation falling on Kvitøya, most probably originating from Eurasia.

scholarly journals Utilization of the Radiofrequency Spectrum above 1 GHz by Passive Services

2001 ◽  
Vol 196 ◽  
pp. 255-263 ◽  
Author(s):  
Juan R. Pardo ◽  
Pierre J. Encrenaz ◽  
Daniel Breton
Keyword(s):  
Electromagnetic Spectrum ◽  
Radio Waves ◽  
Frequency Bands ◽  
Human Control ◽  
Naturally Occurring ◽  
Spectrum Radio ◽  
Active Service ◽  
Active Services ◽  
Cosmic Origin ◽  
Longwave Region

Microwave atmospheric radiometry and radio, mm and sub-mm astronomy are “passive” services, i.e. not involved in any man-made transmission but only concerned with the reception of naturally occurring radio waves. The intensity of the radiation received is not subject to human control, unlike the situation for active services. All active services operate in bands occupied by natural signals of atmospheric and cosmic origin and the active service tranmissions may be powerful enough to noticeably interfere with reception of those signals by scientific services. A conflict exists for the coexistence of active and passive services in many frequency bands, which leads to a need for regulating how to share the electromagnetic spectrum. This document gives an overview of the problems of frequency sharing in the longwave region of the electromagnetic spectrum (radio to submillimetre waves).

scholarly journals Electrical Resistivity Of George VI Ice Shelf, Antarctic Peninsula

1982 ◽  
Vol 3 ◽  
pp. 279-283 ◽  
Author(s):  
John M. Reynolds
Keyword(s):  
Apparent Resistivity ◽  
Sea Water ◽  
Free Water ◽  
Melting Rate ◽  
Small Range ◽  
Ice Shelf ◽  
Ross Ice Shelf ◽  
Melt Water ◽  
Electrical Sounding ◽  
Basal Melting

A georesistivity survey was made on part of George VI Ice Shelf (71°55'S, 67°20'W). The principal objectives were to determine the electrical structure of the 1ce shelf, in particular how refrozen melt water differs in electrical behaviour from dry firn, and to Investigate the environment beneath the ice shelf.Apparent resistivity profiles using a Schlumberger electrode configuration have been interpreted using Ghosh's convolution method for vertical electrical sounding (VES), adapted for use where extreme resistivity contrasts are present.Warm, wet surface conditions tend to reduce the gross resistivity of shallow permeable layers. The electrical results indicate that the refrozen free water has affected the resistivity only indirectly; the mean density of firn is raised to about 0.915 Mg m−3within the uppermost 10 m of the ice shelf at which point the resistivity is comparable to that of Ice of the same density but formed by compaction of firn. The apparent resistivities in the top 100 m reflect the variation of density with depth; a small range of resistivities implies that the range of density 1s narrow and that densification is affected by the percolation and refreezing of melt water.The bulk of the ice behaves as if resistivity either Is independent of temperature or has only a slight dependence (activation energy ~0.15 eV) with a basal melting rate in excess of 1 to 2 m a−1. The principal resistivities determined for two sites on George VI Ice Shelf were within 10% of those at station BC on the Ross Ice Shelf, allowing for differences in temperature. This Indicates that polar ice, I.e. non-temperate ice, has a very narrow range of resistivity. The apparent resistivity profiles are consistent with there being sea-water of oceanic salinity under the Ice shelf.

Sex Behaviour and Sex Determination in Crepidula Fornicata L

1959 ◽  
Vol 36 (1) ◽  
pp. 34-39
Author(s):  
JAN Z. WILCZYNSKI
Keyword(s):  
Sex Ratio ◽  
Sex Determination ◽  
Sea Water ◽  
Male And Female ◽  
Crepidula Fornicata ◽  
Naturally Occurring ◽  
Significant Tendency ◽  
Males And Females

1. The percentages of males and females in naturally occurring chains of Crepidula fornicata L. were found to be 39% females, 6% ‘transients’ and 55% males. 2. Disconnected males kept in cages in sea water for 9 months re-established the normal sex ratio. 3. Disconnected males were kept for periods of 4-6 weeks at temperatures of 30° and 10° C. No significant tendency to change sex was observed. 4. Males were injected with extracts of females. No tendency to change sex was observed. 5. In animals of all sizes from small males to large females both male and female gametes are invariably present together. The gametes of both sexes are polymorphic.

Sign in / Sign up

Export Citation Format

Share Document