Neutral atmospheric delay in interferometric synthetic aperture radar applications: Statistical description and mitigation
Neutral atmospheric delay in interferometric synthetic aperture radar applications: Statistical description and mitigation
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DOI：
10.1029/2002jb001781
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发表时间：
2003-05-03
影响因子：
3.9
通讯作者：
Webb, FH
中科院分区：
文献类型：
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作者：
Emardson, TR;Simons, M;Webb, FH
大气折射率的变化会引起基于卫星的干涉合成孔径雷达(InSAR)观测的变化。我们可以通过平均N个独立的干涉图来减轻对流层效应。由于中性大气在超过1天的时间尺度上是不相关的，使用这一技术在统计上将噪声的方差sigma(2)减少了N倍。利用来自南加州全球定位系统的全球定位系统数据的天顶中性大气延迟，我们发现平均方差取决于观测值L和高度差H之间的距离，即sigma=c L-α+KH，c，α和k的估计值分别约为2.5，0.5和4.8，其中sigma表示毫米，L和H表示公里。我们预计，α的值在很大程度上是与场地无关的，但c的值将取决于感兴趣区域的水汽可变性。该模型适用于L在大约10到800公里的范围内。在这项分析中使用了0到3公里之间的高度差。对于高度差可以忽略的100公里和10公里的距离，西格玛估计分别约为25毫米和8毫米。对于给定的轨道重访时间和图像存档持续时间，我们计算了在给定的长度尺度上达到期望的变形速率敏感度所需的干涉图的数目和持续时间(假设为常数)。假设中性大气是噪声的主要来源，30度视角，图像重访时间为7天，在10公里的距离上检测1 mm yr(-1)的形变速率需要大约2.2年的连续观测。根据我们的结果，我们建议在使用InSAR数据来约束地球物理模型时使用数据协方差结构。
Variations in the refractive index of the atmosphere cause variations in satellite-based interferometric synthetic aperture radar (InSAR) observations. We can mitigate tropospheric effects by averaging N-independent interferograms. Because the neutral atmosphere is uncorrelated at timescales longer than 1 day, using this technique statistically reduces the variance, sigma(2), of the noise by a factor of N. Using zenith neutral atmospheric delays from Global Positioning System (GPS) data from the Southern California Integrated GPS Network, we find that the average variance depends on the distance between observations, L, and height difference, H, as sigma=c L-alpha+kH with estimated values for c, alpha, and k of about 2.5, 0.5, and 4.8, respectively, where sigma is in mm and L and H are in km. We expect that the value of alpha is largely site-independent but the value of c will depend on the water vapor variability of the area of interest. This model is valid over a range of L between approximately 10 and 800 km. Height differences between 0 and 3 km have been used in this analysis. For distances of 100 and 10 km with negligible height differences, sigma is estimated to be approximately 25 and 8 mm, respectively. For a given orbit revisit time and image archive duration, we calculate the number and duration (assumed constant) of interferograms required to achieve a desired sensitivity to deformation rate at a given length scale. Assuming neutral atmosphere is the dominant source of noise, a 30degrees look angle, and an image revisit time of 7 days, detection of a deformation rate of 1 mm yr(-1) over distances of 10 km requires about 2.2 years of continuous observations. Given our results, we suggest a data covariance structure to use when using InSAR data to constrain geophysical models.