Texture of Polar Firn for Remote Sensing
Texture of Polar Firn for Remote Sensing
复制标题
用于遥感的极地冷杉纹理
作者：
R. Alley
了解极地冰层的结构对遥感资料的解释是必要的。我们发现干极铁是一种不规则分层的各向异性介质。firn中的晶粒可以近似为长形球体，其平均轴比高达1.2或更大，并且具有围绕垂直方向聚集的长轴的优选方向。这种细长的晶粒在接近其末端的地方优先结合成垂直的柱状，因此晶粒键表现出优先的水平方向。粒度分布在大部分地区基本一致，归一化分布在时间上是平稳的，但在深度上有一定的差异。在任何深度附近，材料性能波动都很大，但随着深度的增加而减小。随着深度的增加，表面各向异性减小，键尺寸相对于晶粒尺寸略有减小，每个晶粒的键数和键占总晶粒表面的比例增加。晶粒尺寸在2 ~ 5 m以下随龄期线性增加，但在较浅的土层中增加得更快。
Knowledge of the texture of polar firn is necessary for interpretation of remotely sensed data. We find that dry polar firn is an irregularly stratified, anisotropic medium. Grains in firn may be approximated as prolate spheroids with average axial ratios as high as 1.2 or greater and with a preferred orientation of long axes clustered around the vertical. Such elongate grains are preferentially bonded near their ends into vertical columns, so that grain bonds show a preferred horizontal orientation. The grain-size distribution is similar in most firn and the normalized distribution is stationary in time, but the distribution is somewhat different in depth hoar. Fluctuations of firn properties are large near any depth, but decrease with increasing depth. With increasing depth, anisotropy of surfaces decreases, bond size relative to grain size decreases slightly, and number of bonds per grain and fraction of total grain surface in bonds increase. Grain size increases linearly with age below 2 to 5 m, but increases more rapidly in shallower firn.