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Laboratory test of snow wetness influence on electrical conductivity measured with ground penetrating radar

机译:积雪对地面穿透雷达测量的电导率影响的实验室测试

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Ground penetrating radar operated from helicopters or snowmobiles is used to determine snownwater equivalent (SWE) for annual snowpacks from radar wave two-way travel time. However,npresence of liquid water in a snowpack is known to decrease the radar wave velocity, which forna typical snowpack with 5% (by volume) liquid water can lead to an overestimation of SWE bynabout 20%. It would therefore be beneficial if radar measurements could also be used tondetermine snow wetness. Our approach is to use radar wave attenuation in the snowpack, whichndepends on electrical properties of snow (permittivity and conductivity) which in turn depend onnsnow wetness. The relationship between radar wave attenuation and these electrical propertiesncan be derived theoretically, while the relationship between electrical permittivity and snownwetness follows a known empirical formula, which also includes snow density. Snow wetnessncan therefore be determined from radar wave attenuation if the relationship between electricalnconductivity and snow wetness is also known. In a laboratory test, three sets of measurementsnwere made on initially dry 1m thick snowpacks. Snow wetness was controlled by stepwisenaddition of water between radar measurements, and a linear relationship between electricalnconductivity and snow wetness was established.
机译:由直升机或雪地摩托操作的探地雷达用于根据雷达波的双向传播时间确定年度积雪的雪水当量(SWE)。但是,已知积雪中不存在液态水会降低雷达波速度,因此,以5%(按体积计)的液态水的典型积雪会导致SWE高估约20%。因此,如果雷达测量结果也可用于确定雪的湿度将是有益的。我们的方法是在积雪中使用雷达波衰减,这取决于雪的电特性(介电常数和电导率),而雪的电特性又取决于雪的湿度。可以从理论上推导雷达波衰减与这些电特性之间的关系,而介电常数与雪湿度之间的关系遵循已知的经验公式,其中也包括雪密度。如果电导率和雪湿度之间的关系也已知,则可以从雷达波衰减确定雪湿度。在实验室测试中,在最初干燥的1m厚积雪上进行了三组测量。通过在雷达测量之间逐步添加水来控制雪湿度,并建立了电导率与雪湿度之间的线性关系。

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