Collaborative Research: Estimation and Assessment of Errors in High Frequency Radar Ocean Current Measurements

0526978这是一项建议，对高频（HF）雷达衍生的海洋表面流测量误差进行基于模拟的分析，并开发在目前使用的观测系统中评估这些误差的方法。在近岸海洋环流模型中，需要系统地识别和描述这些误差。它还需要纳入许多新的业务产品，这些产品是基于高频雷达网络的海洋表面洋流连续地图而创建的。结论将适用于一般的高频雷达衍生电流测量，但分析将集中在使用紧凑、配置天线几何和测向技术的系统，如CODAR/SeaSonde系统。其他商用系统，如Welan雷达或WERA，也可以在测向配置中操作。目前，人们对用于近岸海面海流测绘的高频雷达系统的兴趣正处于一个迅速加速的时期。系统已经在美国沿海的许多地方以及世界各地的许多其他地方就位。这些系统提供接近实时的测量前一个或两米内的海洋环流的海洋表面,在1 - 3公里分辨率网格,射程约70公里的海面高达200公里的远程单位但可靠的估计逐点数据的不确定性仍然不可,即使这样的错误值,连同他们的统计描述,需要适当的同化成数字循环模型。虽然通过与实地测量的比较提供了对总体不确定程度的估计，但由于若干原因，这些比较本身是不够的。首先，原位测量和遥感测量具有本质上的不同。流动仪和较小程度上的漂移仪在一个固定点测量速度，而雷达对几平方公里内的平均电流很敏感。其次，雷达测量非常接近表面的电流，而传统的电流计测量是有问题的。第三，雷达的连续二维覆盖不能重复，因此不能仅根据与现场观测的比较来评估系统误差，例如测向算法中的指向偏差。科学、海岸工程、公共安全和娱乐社区将通过更详细和准确的海洋环流和波浪条件的临近预报和预报，大大提高精度和分辨率，感受到沿海地区高频电流测量有效同化的广泛影响。例如，具有高空间和时间分辨率的地表流动预测将通过允许准确的漂移预测来加强海空救援和石油和有毒物质泄漏响应。同样，对沿海环流的更准确预测可以预测海洋种群从浮游植物到鲸鱼的变化。本项目力求通过使用计算机模拟，酌情与现有的现场数据集进行比较，来解决误差分析和评价的问题。各种误差源的影响，包括船舶回波，电离层回波，随机噪声，测量单元内洋流的随机变化，系统特性的不完善知识，如天线方向图失真，以及作为天线设计函数的测向算法的局限性，将被检查。对常用高频雷达配置的误差传播进行系统的研究是迟来的，一旦记录下来，这些误差模型将加速这些卓越的海洋仪器的开发。

0526978This is a proposal to conduct a simulation-based analysis of errors in high frequency (HF) radar derived ocean surface current measurements and develop means of assessing these errors in observational systems in use today. The systematic identification and description of these errors is needed for assimilation of HF radar-derived current measurements into near-shore ocean circulation models. It is also needed for incorporation into the many new operational products that are being created based on continuous maps of ocean surface currents from HF radar networks. Conclusions will be applicable to HF radar-derived current measurements in general, but analyses will focus on systems that use compact, collocated antenna geometry and direction finding techniques, such as the CODAR/SeaSonde systems. Other commercially available systems, such as the Welan Radar or WERA, can also be operated in a direction-finding configuration. The interest in HF radar systems for near-shore mapping of ocean surface currents is presently undergoing a period of rapid acceleration. Systems are already in place at numerous locations around the coastal United States as well as many other locations around the world. These systems provide near real-time measurements of the ocean circulation within the top one or two meters of the ocean surface, on a 1-3 km resolution grid, with a range over the ocean surface of about 70 km with up to 200 km for the long range units but reliable estimates of the point-by-point uncertainties in the data remain unavailable even though such error values, together with their statistical descriptions, are required for proper assimilation into numerical circulation models. While estimates of overall uncertainty levels have been provided through comparisons with in situ measurements, those comparisons on their own are not sufficient for a number of reasons. Firstly, the in situ and remote-sensing measurements are inherently different. Current meters and, to a lesser extent, drifters measure velocity at a fixed point while the radar is sensitive to the current averaged over several square kilometers. Secondly, the radar measures the current very close to the surface where measurement with conventional current meters is problematic. Thirdly, the continuous, two-dimensional coverage of the radar cannot be duplicated and, therefore systematic errors, such as pointing biases in the direction finding algorithms, cannot be assessed based solely on comparisons with in situ observations.The broad impact of effective assimilation of HF current measurements in coastal areas would be felt by the scientific, coastal engineering, public safety and recreational communities through more detailed and accurate nowcasts and forecasts for ocean circulation and wave conditions with greatly improved accuracy and resolution. For example, prediction of surface flows with high spatial and temporal resolution would enhance air-sea rescue and oil and toxic spill response by allowing accurate drift forecasts. Similarly, more accurate predictions of coastal circulation could lead to forecasting shifts in marine populations from phytoplankton to whales. This project seeks to address the problem of error analysis and assessment through the use of computer simulations backed up, where appropriate, by comparisons with existing in situ data sets. The effects of a wide variety of error sources, including ship echoes, ionospheric echoes, random noise, random variations in the ocean currents within a measurement cell, imperfect knowledge of system properties, such as antenna pattern distortion, and limitations of the direction finding algorithms as a function of antenna design will be examined. A systematic look at error propagation for the commonly used HF radar configurations is overdue and that, once documented, these error models will accelerate the exploitation of these remarkable oceanographic instruments.