Call number:
ZSP-201-80/23
In:
CRREL Report, 80-23
Description / Table of Contents:
The contribution of brine layers to observed reflective anisotropy of sea ice at 100 MHz is quantitatively assessed. The sea ice is considered to be a stratified, inhomogeneous, anisotropic dielectric consisting of pure ice containing ordered arrays of conducting inclusions (brine layers). Below the transition zone, the ice is assumed to have constant azimuthal c-axis orientation within the horizontal plane, so that the orientation of brine layers is uniform. The brine layers are also assumed to become increasingly well-defined with depth, since adjacent brine inclusions tend to fuse together with increasing temperature. A theoretical explanation for observed reflective anisotropy is proposed in terms of an isotropic electric flux penetration into the brine layers. Penetration anisotropy and brine layer geometry are linked to anisotropy in the complex dielectric constant of sea ice. In order to illustrate the above effects we present a numerical method of approximating the reflected power of a plane wave pulse incident on a slab of sea ice. Mixture dielectric constants are calculated for two polarizations of the incident wave: 1) the electric field parallel to the c-axis direction, and 2) the electric field perpendicular to the c-axis direction. These dielectric constants are then used to calculate power reflection coefficients for the two polarizations. Significant bottom reflection (R ~ 0.08) occurs when the polariza-tion is parallel to the c-axis. However, when the polarization is perpendicular to the c-axis, the return may be almost completely extinguished (R 〈 0.001). This extinction is due primarily to absorptive loss associated with the conduct-ing inclusions and secondarily to an impedance match at the ice/water interface that results in transmission of the wave to the water without reflection.
Type of Medium:
Series available for loan
Pages:
vi, 15 Seiten
,
Illustrationen
Series Statement:
CRREL Report 80-23
URL:
https://erdc-library.erdc.dren.mil/jspui/bitstream/11681/9576/1/CR-80-23.pdf
Language:
English
Note:
CONTENTS
Abstract
Preface
List of symbols
Introduction
Anisotropy and sea ice macrostructure
Anisotropy and sea ice microstructure
A theory of anisotropic radar return from sea ice
Anisotropic electric flux penetration into brine layers
Implications of normal exclusion, tangential penetration, and brine layer geometry for dielectric behavior of sea ice
Modeling of electromagnetic reflection from a stratified, anisotropic, inhomogeneous lossy medium
Calculation of mixture complex dielectric constants
Calculation of interfacial power reflection coefficients
Calculation of bulk power reflection coefficients
Calculation of attenuated power reflection coefficients
Beam spread
Results
Anisotropic bottom reflections
Anisotropic complex dielectric constants
Sensitivity of parameters
Internal reflection: the bumps
Discussion
Conclusions
Literature cited
Location:
AWI Archive
Branch Library:
AWI Library
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