基于TerraSAR-X卫星数据的内孤立波参数和海表流速信息提取的探索研究

本文利用TerraSAR-X(TSX)卫星于2010年4月22日在南海东沙岛附近海域获取的数据进行海洋内孤立波动力要素和海表流速信息的提取研究。基于TSX数据的后向散射强度信息,利用经验模态分解法得到内孤立波半波宽度,再利用两层模型法和参数化法计算得到内孤立波振幅和相速度。反演结果显示,利用参数化方法得到的振幅(约21～39 m)和两层模型法得到的相速度(约1.07 m/s)与历史实测资料较为一致。进而利用TSX的顺轨干涉数据获取研究海域内的多普勒速度,再分别采用M4S模型法和直接分离法处理,进而提取海表流速。结果显示,两种方法得到的海表流速的全场平均值较为一致,均为1.10 m/s左右。M4S模型法对流速最大值的改变量较大而直接分离法对流速最小值的改变量较大。M4S模型对内孤立波波峰线区域海表流速的修正大于无内孤立波的海域。最后,基于KdV方程计算得到内孤立波引起的表面流的流速约为0.28 m/s,对反演出的海表流速贡献占比23%。

Exploratory research on the retrieval of internal wave parameters and sea surface current velocity based on TerraSAR-X satellite data

In this paper, we conducted a study on deriving internal wave parameters and sea surface current velocity in the vicinity of Dongsha Island from spaceborne SAR data of TerraSAR-X (TSX), acquired on April 22, 2010. Based on the intensity data of the TSX scene, characteristic half width of the internal wave was obtained through the empirical mode decomposition method. Then amplitude and phase speed of the internal solitary wave were calculated using the two-layer model method and the parameterization method, respectively. The results suggested that the amplitude (approximately 21–39 m) acquired by the parameterization method and the phase speed (approximately 1.06 m/s) obtained by the two-layer model method were consistent with the historical measurements. Furthermore, the Doppler velocity in the research area was calculated using along-track interferometry data of the TSX scene. The M4S model and the direct-separation method were used to extract the sea surface current velocity. The mean sea surface current field of the study area obtained by the two methods were consistent, which were both of approximately 1.10 m/s. The M4S model led to more adjustments to maximum of the surface velocity whereas more adjustments to the minimum values were found in the direct-separation method. Moreover, it was found that the adjustment of surface current retrieval using the M4S model were more in the region of wave crest of the internal waves. Finally, based on the KdV equation, the velocity of internal-wave-induced surface flow is about 0.28 m/s, which contributes 23% to the retrieved sea surface current velocity.