Microwave permittivity of dry snow
Microwave permittivity of dry snow
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DOI：
10.1109/36.485133
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
C. Mätzler
中科院分区：
文献类型：
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作者：
C. Mätzler
干雪的相对介电常数或相对介电常数/spl epsiv/与从约1 MHz到至少10 GHz的微波范围的频率无关。新的测量精度提高了与一个专门设计的谐振器工作在1 GHz附近。同轴传感器精确地定义了样品体积，可以确定其实际质量以给出雪样品的密度。一种特殊的电子仪器，称为resometer，可以在现场条件下进行准确和快速的测量。在瑞士和奥地利阿尔卑斯山的测试地点对不同类型的干雪（新鲜雪、旧雪、风压雪、深度雪和再冻结雪皮）进行了约90次测量。数据表明，/spl epsiv/仅是雪密度的函数，假定拟合曲线的标准偏差0.006只是由于预期的测量误差。根据物理混合理论对这些数据的解释支持Polder和货车Santen（1946）的有效介质公式。这些数据允许将平均轴比X作为冰体积分数的函数。长椭球体和扁椭球体都可以解释这些数据。独立的推理倾向于扁圆形粒子。在这两种情况下，轴比随着分数的增加而增加，直到临界值0.33，然后在更高的分数下减小。缓慢压实的雪的破坏性变质解释了X的增加，而随后的减少可能是由于烧结。到目前为止，在-10/spl deg/C和0/spl deg/C之间的温度下，没有观察到冰粒上的液体状表面层对/spl epsiv/的影响。
The relative dielectric constant, or relative permittivity, /spl epsiv/ of dry snow, is independent of frequency from about 1 MHz up to the microwave range of at least 10 GHz. New measurements of with improved accuracy were made with a specially designed resonator operating near 1 GHz. The coaxial sensor accurately defines the sample volume whose actual mass can be determined to give the density of the snow sample. A special electronic instrument, called a resometer, enabled accurate and rapid measurements under field conditions. Some 90 measurements of different kinds of dry snow (fresh, old, wind-pressed snow, depth hear, and refrozen crusts) were made at test sites in the Swiss and Austrian Alps. The data indicate that /spl epsiv/ is a function of snow density only, given that the standard deviation of 0.006 from the fitted curve is just due to the expected measurement errors. The interpretation of these data in terms of physical mixing theory favors the effective medium formula of Polder and van Santen (1946). The data allow to relate the average axial ratio X as a function of ice volume fraction. Both prolate and oblate spheroids can explain the data. Independent reasoning gives preference to oblate particles. In both cases, the axial ratio increases with increasing fraction up to a critical value of 0.33, followed by a decrease at still higher fractions. The destructive metamorphism of slowly compacting snow explains the increase of X, while the following decrease might be due to sintering. So far, no effect on /spl epsiv/ by a liquid-like surface layer on the ice grains at temperatures between -10/spl deg/C and 0/spl deg/C has been observed.