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

合作研究：高频雷达海流测量误差的估计和评估

• 批准号: 0526614
• 负责人: Jeffrey Paduan
• 金额: $ 4.87万
• 依托单位: Naval Postgraduate School
• 依托单位国家: 美国
• 项目类别: Interagency Agreement
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-10-01 至 2007-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0526614&HistoricalAwards=false
• 关键词: Collaborative; Research; Estimation; Assessment; Errors

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.

0526978这是一项建议，对高频（HF）雷达得出的海洋表面流测量结果中的误差进行基于模拟的分析，并制定评估当今使用的观测系统中这些误差的方法。这些错误的系统识别和描述是需要的高频雷达派生的电流测量到近岸海洋环流模式同化。还需要将其纳入正在根据高频雷达网络海洋表面流连续图制作的许多新的业务产品。结论将适用于高频雷达派生的电流测量一般，但分析将集中在系统，使用紧凑，并置天线几何和测向技术，如CODAR/海洋探测系统。其他商用系统，如威兰雷达或WERA，也可以在测向配置中操作。目前，人们对用于海洋表面流近岸测绘的高频雷达系统的兴趣正在迅速加速。该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安装。这些系统在1-3公里分辨率的网格上提供海洋表面顶部一米或两米内的海洋环流的近实时测量，海洋表面上的范围约为70公里，远距离单元可达200公里，但数据中逐点不确定性的可靠估计仍然不可用，尽管这种误差值及其统计描述，需要适当的同化到数值环流模式。虽然通过与实地测量的比较提供了总体不确定性水平的估计数，但由于若干原因，这些比较本身是不够的。首先，实地测量和遥感测量有着本质的不同。海流计和在较小程度上的漂流器在固定点测量流速，而雷达对几平方公里的平均海流敏感。其次，雷达测量非常接近表面的电流，而传统的电流计测量存在问题。第三，雷达的连续、二维覆盖不能被复制，因此，系统误差，例如测向算法中的指向偏差，不能仅仅基于与现场观测的比较来评估。通过对海洋环流和波浪状况进行更详细、更准确的临近预报和预测，大大提高了准确性和分辨率，从而增强了公共安全和娱乐社区的能力。例如，以高空间和时间分辨率预测地表流动将通过准确的漂移预测来加强海气救援以及石油和有毒物质泄漏响应。同样，更准确地预测沿海环流可能导致预测海洋种群从浮游植物到鲸鱼的变化。该项目力求通过使用计算机模拟来解决误差分析和评估问题，并酌情通过与现有的现场数据集进行比较来加以支持。各种各样的误差源的影响，包括船舶回波，电离层回波，随机噪声，在测量单元内的洋流的随机变化，不完善的系统属性的知识，如天线方向图失真，以及作为天线设计的功能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早就应该进行的，一旦记录在案，这些误差模型将加速这些出色的海洋仪器的开发。