使用星载SAR对海洋涌浪场的例行监测和分析
Routine monitoring and analysis of ocean swell fields using a spaceborne SAR
摘要：
卫星合成孔径雷达（SAR）观测可以提供一个全球性的海洋涌浪场时，使用特定的“波样式“采样。介绍了一种方法，用于常规地从SAR 2级产品中获得波谱的较长波长（涌浪）部分的积分特性，并监测和预测其在洋盆中的演变。SAR派生的估计涌浪高度，能量加权的峰值周期和方向，验证浮标观测，和峰值方向被用来项目的峰值周期在一维沿相应的大圆航线，向前和向后的时间，使用峰值周期群速度。由此产生的实时数据集的伟大的圆形投影峰值期间产生的二维地图，可用于监测和预测的空间范围，和时间演变，个别海洋涌浪场，因为他们从他们的源区域传播到遥远的海岸线。该方法被认为是一致的分散到达的峰值涌浪期间在大洋中的浮标。简单的大圆传播方法不能像峰值周期那样在空间中投影涌浪高度，因为沿大圆的能量演化是源风暴特性和未知涌浪耗散率的函数。因此，提出了一个更一般的几何光学模型的风暴的远场。该模型在这里被应用于确定长距离上的衰减。对于一个最大的记录风暴，15秒的周期膨胀的观测是一致的，对应于一个恒定的耗散率为3300公里的e-折叠尺度的能量。在这种情况下，涌浪耗散是全球尺度上波浪能平衡中的一个重要项。
英文摘要：
Satellite Synthetic Aperture Radar (SAR) observations can provide a global view of ocean swell fields when using a specific "wave mode" sampling. A methodology is presented to routinely derive integral properties of the longer wavelength (swell) portion of the wave spectrum from SAR Level 2 products, and both monitor and predict their evolution across ocean basins. SAR-derived estimates of swell height, and energy-weighted peak period and direction, are validated against buoy observations, and the peak directions are used to project the peak periods in one dimension along the corresponding great circle route, both forward and back in time, using the peak period group velocity. The resulting real time dataset of great circle-projected peak periods produces two-dimensional maps that can be used to monitor and predict the spatial extent, and temporal evolution, of individual ocean swell fields as they propagate from their source region to distant coastlines. The methodology is found to be consistent with the dispersive arrival of peak swell periods at a mid-ocean buoy. The simple great circle propagation method cannot project the swell heights in space like the peak periods, because energy evolution along a great circle is a function of the source storm characteristics and the unknown swell dissipation rate. A more general geometric optics model is thus proposed for the far field of the storms. This model is applied here to determine the attenuation over long distances. For one of the largest recorded storms, observations of 15 s period swells are consistent with a constant dissipation rate that corresponds to a 3300 km e-folding scale for the energy. In this case, swell dissipation is a significant term in the wave energy balance at global scales.
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