Fram Strait satellite image‐derived ice motions
Fram Strait satellite image‐derived ice motions
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DOI：
10.1029/90jc02273
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发表时间：
1991-03
影响因子：
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通讯作者：
W. Emery;C. Fowler;J. Hawkins;R. Preller
中科院分区：
文献类型：
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作者：
W. Emery;C. Fowler;J. Hawkins;R. Preller
为了开发一个业务方法，美国海军/NOAA联合冰中心提取冰速度矢量从序列的高级甚高分辨率辐射计（AVHRR）图像，我们结合了最大互相关（MCC）方法与空间滤波技术的图像推断冰运动矢量。我们直接从图像亮度值计算图像之间的互相关，而不是计算FFT。直接方法允许更大的灵活性，在计算参数设置，并允许一个计算运动矢量附近的海岸线，需要不规则的窗口。通过使用统计和空间滤波器的组合，我们可以检索相干冰运动矢量存在的云污染的图像。自1986年4月以来，弗拉姆海峡地区的一系列六张卫星图像被用来根据成对的连续图像计算海冰运动。由此产生的冰的运动矢量作为一个代表性的表面流场来自客观的卫星图像。所得矢量运动场与人工跟踪矢量匹配良好，从而验证了客观MCC方法计算冰运动的有效性。这些技术被应用到可见光和红外AVHRR通道和图像具有不同的空间分辨率，产生约0.5厘米/秒的总偏差精度和约0.9厘米/秒的标准偏差。MCC冰运动的结果也与该地区的风力驱动的数值模型模拟进行了比较。MCC图像得出的速度与数值模型得出的速度之间的显著差异被认为主要是由于比模型中存在的更强的洋流。
In order to develop an operational method for the U.S. Navy/NOAA Joint Ice Center to extract ice velocity vectors from sequential advanced very high resolution radiometer (AVHRR) imagery, we have combined the maximum cross correlation (MCC) method with a spatial filtering technique on the image inferred ice motion vectors. We compute the cross correlations between images directly from the image brightness values rather than computing FFTs. The direct method allows greater flexibility in computational parameter settings and allows one to compute motion vectors near coastlines where irregular windows are required. By using a combination of statistical and spatial filters we can then retrieve coherent ice motion vectors in the presence of cloud contaminated imagery. A series of six satellite images of the Fram Strait region, from April 1986, was used to compute sea ice motion from pairs of sequential images. The resulting ice motion vectors were taken as a representation of the surface flow field derived objectively from the satellite imagery. Resulting vector motion fields were found to match well with manually tracked vectors for the same images, thus verifying the validity of the objective MCC method of computing ice motion. These techniques were applied to both the visible and infrared AVHRR channels and to images with different spatial resolutions yielding an overall bias accuracy of about 0.5 cm/s and standard deviations of about 0.9 cm/s. The MCC ice motion results were also compared with wind-driven numerical model simulations of the region. Marked differences between the MCC image-derived velocities and those from the numerical model were thought to be primarily due to a stronger ocean current than was present in the model.