Weather-Induced Transport through a Tidal Channel Calibrated by an Unmanned Boat
Weather-Induced Transport through a Tidal Channel Calibrated by an Unmanned Boat
复制标题
DOI：
10.1175/jtech-d-17-0130.1
复制
发表时间：
2018-02-01
影响因子：
2.2
通讯作者：
Wu, Renhao
中科院分区：
文献类型：
--
作者：
Li, Chunyan;Weeks, Eddie;Wu, Renhao
无人水面航行器 (USV) 被设计和建造为连续运行，以覆盖洪水和落潮，并且最好覆盖完整的潮汐周期（例如，类似于 24 小时），以测量水平流速的垂直剖面。它被应用于路易斯安那州福雄港的潮汐通道。底部安装的 ADCP 部署了 515 天。速度剖面的第一个 EOF 模式显示出正压型流动，可以解释超过 98.2% 的变异性。第二种模式显示了典型的两层河口流，这解释了 0.47% 的变异性。使用 USV 的总运输量与底部安装 ADCP 的垂直平均速度的线性回归（R 平方值为 98%），计算出整个部署过程中的总沿航道运输量。传输的低通滤波允许检查 76 个冷锋、暖锋或冷暖锋组合经过该地区的事件的影响。讨论了前七名最严重的事件，因为它们相关的运输在时间序列中明显突出，表明天气的重要性。结果表明，锋线水平长度尺度约为1500-3000公里的大尺度天气系统控制着该地区的潮下输送。冷（暖）锋往往会产生向外（向内）的输送，然后出现反弹。大气强迫与海洋响应之间的最大相干性达到约71%-84%，其发生频率f约每天0.29个周期或T约3.4天，与大气锋面返回周期（约3-7天）一致。
An unmanned surface vehicle (USV) was designed and constructed to operate continuously for covering both flood and ebb and preferably a complete tidal cycle (e.g., similar to 24 h) to measure the vertical profiles of horizontal flow velocity. It was applied in a tidal channel at Port Fourchon, Louisiana. A bottom-mounted ADCP was deployed for 515 days. The first EOF mode of the velocity profiles showed a barotropic type of flow that explained more than 98.2% of the variability. The second mode showed a typical estuarine flow with two layers, which explained 0.47% of the variability. Using a linear regression of the total transport from the USV with the vertically averaged velocity from the bottom-mounted ADCP, with an R-squared value of 98%, the total along-channel transport throughout the deployment was calculated. A low-pass filtering of the transport allowed for examining the impact of 76 events with cold, warm, or combined cold-warm fronts passing the area. The top seven most severe events were discussed, as their associated transports obviously stood out in the time series, indicating the importance of weather. It is shown that large-scale weather systems with frontal lines of similar to 1500-3000-km horizontal length scale control the subtidal transport in the area. Cold (warm) fronts tend to generate outward (inward) transports, followed by a rebound. The maximum coherence between the atmospheric forcing and the ocean response reached similar to 71%-84%, which occurred at about a frequency f of similar to 0.29 cycle per day or T of similar to 3.4 days in the period, consistent with the atmospheric frontal return periods (similar to 3-7 days).