Source regions and reflection of infragravity waves offshore of the U . S .s P acific N orthwest
Source regions and reflection of infragravity waves offshore of the U . S .s P acific N orthwest
复制标题
美国近海次重力波的源区和反射。
作者：
Neale J
海洋重力波是一种海洋表面重力波，但其波长（数十公里）和周期（>30秒）远长于风浪和涌浪。大多数研究都是在浅水中进行的，对深水中亚重力波的了解仍然有限。最近对深水亚重力波的兴趣是由于它们可能对未来海平面的高分辨率卫星雷达测高测量产生误差。在这里，使用2012年9月至2013年5月作为卡斯卡迪亚倡议阵列的一部分部署的压差计研究了美国太平洋西北部近海的深水亚重力波。记录的互相关揭示了亚重力波在整个阵列中的传播方向，并由此推断出震源区。发现主要来源是东部的海岸线，与大风浪和涌浪事件在盆地的东侧。在北方半球夏季，震源向南移动，在有记录的几天里，亚重力波从太平洋西侧到达。其中五个西风波到达的互相关函数的不对称性被用来计算向海传播能量与向岸传播能量的比值，从而估计100-200 s周期的亚重力波反射强度。这些来自西方的遥远到达的反射似乎很强，下限估计为r = 0.49 ± 0.29（反射系数±标准误差），上限估计为r = 0.74 ± 0.06。这些结果表明，在海洋边界的反射可能是一个重要的考虑在深海亚重力波。
Infragravity waves are oceanic surface gravity waves but with wavelengths (tens of km) and periods (>30 s) much longer than wind waves and swell. Mostly studied in shallow water, knowledge of infragravity waves in deep water has remained limited. Recent interest in deep water infragravity waves has been motivated by the error they may contribute to future high‐resolution satellite radar altimetry measurements of sea level. Here deep water infragravity waves offshore of the Pacific Northwest of the U.S. were studied using differential pressure gauges which were deployed as part of the Cascadia Initiative array from September 2012 to May 2013. Cross correlation of the records revealed direction of infragravity wave propagation across the array, from which source regions were inferred. The dominant source was found to be the coastline to the east, associated with large wind waves and swell incident on the eastern side of the basin. The source shifted southward during northern‐hemisphere summer, and on several days in the record infragravity waves arrived from the western side of the Pacific. Asymmetry of cross‐correlation functions for five of these westerly arrivals was used to calculate the ratio of seaward to shoreward propagating energy, and hence estimate the strength of infragravity wave reflection at periods of 100–200 s. Reflection of these remote arrivals from the west appeared to be strong, with a lower bound estimate of r = 0.49 ± 0.29 (reflection coefficient ± standard error) and an upper bound estimate of r = 0.74 ± 0.06. These results suggest that reflection at ocean boundaries may be an important consideration for infragravity waves in the deep ocean.