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Exploring Tornadic Debris Signature Hypotheses Using Radar Simulations and Large-Eddy Simulations 利用雷达模拟和大涡模拟探索龙卷风碎片特征假设
IF 2.2 4区 地球科学 Q2 ENGINEERING, OCEAN Pub Date : 2023-08-14 DOI: 10.1175/jtech-d-22-0141.1
Rachael N. Cross, D. Bodine, R. Palmer, Casey B. Griffin, B. Cheong, S. Torres, C. Fulton, J. Lujan, T. Maruyama
When a tornado lofts debris to the height of the radar beam, a signature known as the tornadic debris signature (TDS) can sometimes be observed on radar. The TDS is a useful signature for operational forecasters as it can confirm the presence of a tornado and provide information about the amount of damage occurring. Since real-time estimates of tornadic intensity do not have a high degree of accuracy, past studies have hypothesized that the TDS could also be an indicator of the strength of a tornado. However, few studies have related the tornadic wind field to TDS characteristics due to the difficulty of obtaining accurate, three-dimensional wind data in tornadoes from radar data. With this in mind, the goals of this study are twofold: 1) to investigate the relationships between polarimetric characteristics of TDSs and the three-dimensional tornadic winds, and 2) to define relationships between polarimetric radar variables and debris characteristics. Simulations are performed using a dual-polarization radar simulator called SimRadar; Large-Eddy Simulations (LESs) of tornadoes; and a single-volume, T-matrix based emulator. Results show that increases (decreases) in horizontal and vertical wind speeds are related to decreases (increases) in correlation coefficient and increases (decreases) in TDS area and height for all simulated debris types. However, the range of correlation coefficient values varies with debris type, indicating that TDSs comprised of similar debris types can appear remarkably different on radar compared to a TDS with diverse scatterers. Such findings confirm past, observational hypotheses and can aid operational forecasters in tornado detection and potentially the categorization of damage severity using radar data.
当龙卷风将碎片抛到雷达波束的高度时,有时可以在雷达上观察到龙卷风碎片特征(TDS)。TDS对预报员来说是一个有用的信号,因为它可以确认龙卷风的存在,并提供有关正在发生的破坏程度的信息。由于对龙卷风强度的实时估计没有很高的准确性,过去的研究假设TDS也可以作为龙卷风强度的一个指标。然而,由于难以从雷达数据中获得准确的三维龙卷风风场数据,因此将龙卷风风场与TDS特征联系起来的研究很少。考虑到这一点,本研究的目标有两个:1)研究tds的极化特征与三维龙卷风风之间的关系;2)定义极化雷达变量与碎片特征之间的关系。使用双偏振雷达模拟器simmradar进行仿真;龙卷风的大涡模拟(LESs)以及基于t矩阵的单体积仿真器。结果表明:水平风速和垂直风速的增大(减小)与相关系数的减小(增大)、TDS面积和高度的增大(减小)相关;然而,相关系数的取值范围随碎片类型的不同而不同,这表明由相似碎片类型组成的TDS与具有不同散射体的TDS相比,在雷达上的表现有显著差异。这些发现证实了过去的观测假设,可以帮助预报员进行龙卷风探测,并可能利用雷达数据对破坏程度进行分类。
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引用次数: 0
A Novel Doppler Unfolding Technique Using Optical Flow 一种新型的光流多普勒展开技术
IF 2.2 4区 地球科学 Q2 ENGINEERING, OCEAN Pub Date : 2023-08-11 DOI: 10.1175/jtech-d-23-0057.1
A. Protat, V. Louf, M. Curtis
Doppler radars measure Doppler velocity within the [-VN, VN] range, where VN is the Nyquist velocity. Doppler velocities outside of this range are “folded” within this interval. All Doppler “unfolding” techniques use the folded velocities themselves. In this work, we investigate the potential of using velocities derived from optical flow techniques applied to the radar reflectivity field for that purpose. The analysis of wind speed errors using six months of multi-Doppler wind retrievals showed that 99.9% of all points are characterized by errors smaller than 26 ms-1 below 5 km height, corresponding to a failure rate of less than 0.01% if optical flow winds were used to unfold Doppler velocities for VN = 26 ms-1. These errors largely increase above 5 km height, indicating that vertical continuity tests should be included to reduce failure rates at higher elevations. Following these results, we have developed the Two-step Optical Flow Unfolding (TOFU) technique, with the specific objective to accurately unfold Doppler velocities with VN = 26 ms-1.The TOFU performance was assessed using challenging case studies, comparisons with an advanced Doppler unfolding technique using higher Nyquist velocities, and six months of high VN (47.2 ms-1) data artificially folded to 26 ms-1. TOFU failure rates were found to be very low. Three main situations contributed to these errors: high low-level wind shear, elevated cloud layers associated with high winds, and radar data artefacts. Our recommendation is to use these unfolded winds as the first step of advanced Doppler unfolding techniques.
多普勒雷达测量[-VN,VN]范围内的多普勒速度,其中VN是奈奎斯特速度。该范围之外的多普勒速度在该区间内“折叠”。所有多普勒“展开”技术都使用折叠速度本身。在这项工作中,我们研究了将光流技术导出的速度应用于雷达反射率场的潜力。使用六个月的多多普勒风反演对风速误差的分析表明,99.9%的所有点的特征是在5公里高度以下的误差小于26 ms-1,如果使用光流风来展开VN=26 ms-1的多普勒速度,则故障率小于0.01%。这些误差在5km高度以上大幅增加,表明应包括垂直连续性测试,以降低高海拔地区的故障率。根据这些结果,我们开发了两步光学流展开(TOFU)技术,其具体目标是准确展开VN=26ms-1的多普勒速度。TOFU性能通过具有挑战性的案例研究进行评估,与使用更高奈奎斯特速度的先进多普勒展开技术进行比较,6个月的高VN(47.2ms-1)数据被人工折叠到26ms-1。TOFU失败率非常低。造成这些错误的主要有三种情况:高水平风切变、与大风相关的云层升高以及雷达数据伪影。我们的建议是将这些展开的风作为先进多普勒展开技术的第一步。
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引用次数: 0
Observations of Surface Gravity Wave Spectra from Moving Platforms 移动平台表面重力波谱观测
IF 2.2 4区 地球科学 Q2 ENGINEERING, OCEAN Pub Date : 2023-08-08 DOI: 10.1175/jtech-d-23-0022.1
Luke Colosi, N. Pizzo, L. Grare, N. Statom, L. Lenain
Surface waves play an important role in the ocean-atmosphere coupled climate system by mediating the exchange of momentum, heat, and gas between the atmosphere and the ocean. Pseudo-Lagrangian autonomous platforms (e.g., Boeing Liquid Robotics Wave Gliders) have been used to investigate the underlying physical dynamics involved in these processes to better parameterize the air-sea exchange occurring at the scale of the surface waves. This requires accurate measurements of directional surface waves down to short scales (O(1) meter), as these shorter waves support most of the stress between the atmosphere and the ocean. A challenge to overcome for pseudo-Lagrangian autonomous vehicles is that the platform’s velocity causes the observed frequency of the waves to be Doppler shifted. This leads to a modulation of the wave spectrum, particularly at high frequencies, that depends on the platform’s speed, the wave frequency, and the relative angle between the direction of wave and platform propagation. In this work, we propose a method to account for Doppler effects that considers the full directionality of the wave field. The method is validated using a unique dataset collected from a fleet of two Wave Gliders off the coast of Southern California in September 2019 operating on the perimeter of a tight square (500-m edge length) track over a three-day deployment. This technique can be used to estimate wave spectra derived from other slow-moving surface vehicles such as Saildrones that use platform motion to characterize the surface wave field. MATLAB routines to implement this method are publicly available.
表面波通过介导大气和海洋之间的动量、热量和气体交换,在海洋-大气耦合气候系统中发挥着重要作用。伪拉格朗日自主平台(例如波音液体机器人波浪滑翔机)已被用于研究这些过程中涉及的潜在物理动力学,以更好地参数化在表面波规模下发生的海气交换。这需要精确测量低至短尺度(O(1)米)的定向表面波,因为这些较短的波支持大气和海洋之间的大部分应力。伪拉格朗日自动驾驶汽车需要克服的一个挑战是,平台的速度会导致观测到的波的频率发生多普勒频移。这导致了波谱的调制,特别是在高频下,这取决于平台的速度、波的频率以及波的方向和平台传播之间的相对角度。在这项工作中,我们提出了一种考虑波场全方向性的多普勒效应的方法。该方法使用一个独特的数据集进行了验证,该数据集于2019年9月在南加州海岸外的一支由两架波浪滑翔机组成的机队中收集,在为期三天的部署中,该机队在一条紧密的正方形(500米边长)轨道的周边运行。这项技术可用于估计其他缓慢移动的水面交通工具(如使用平台运动来表征表面波场的水手无人机)的波谱。实现这种方法的MATLAB例程是公开的。
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引用次数: 0
A mapping methodology adapted to all polar and subpolar oceans with a stretching/shrinking constraint 一种适用于所有极地和副极地海洋的测绘方法,具有拉伸/收缩约束
IF 2.2 4区 地球科学 Q2 ENGINEERING, OCEAN Pub Date : 2023-08-07 DOI: 10.1175/jtech-d-22-0143.1
Vigan Mensah, K. Ohshima
Polar and subpolar oceans play a particularly important role in the global climate and its temporal changes, yet these regions are less well sampled than the rest of the global ocean. To better understand the physical or biogeochemical properties and their variabilities in these regions, accurate data mapping is crucial. In this paper, we introduce a mapping methodology that includes a water column shrinking and stretching constraint (SSC) based on the principle of conservation of potential vorticity. To demonstrate the mapping scheme efficiency, we map the ocean temperature in the southern Sea of Okhotsk, where the bottom topography comprises a broad and shallow shelf, a sharp continental slope, and a deep oceanic basin. Such topographic features are typical of polar and subpolar marginal seas. Results reveal that the SSC integrated (SSCI) mapping strongly reduces the mapping error in the broad and shallow shelf compared with a recently introduced topographic constraint integrated (TCI) mapping procedure. We also tested our mapping scheme in the Southern Ocean, which has a comparatively slanted shelf, a wider and gentler slope, and a deep and broad oceanic basin. We found that the SSCI and TCI methods are practically equivalent there. The SSCI mapping is thus an effective method to map the ocean’s properties in various topographic environments and should be adequate in all polar and subpolar regions. Importantly, we introduced a standardized procedure for determining the decorrelation length scales—a necessary step prior to implementing any mapping scheme—in any topographic conditions.
极地和副极地海洋在全球气候及其时间变化中发挥着特别重要的作用,但这些区域的采样情况不如全球海洋的其他区域。为了更好地了解这些地区的物理或生物地球化学特性及其变化性,准确的数据测绘至关重要。在本文中,我们介绍了一种基于位涡守恒原理的映射方法,该方法包括水柱收缩和拉伸约束(SSC)。为了证明绘图方案的有效性,我们绘制了鄂霍次克海南部的海洋温度图,那里的底部地形包括宽阔而浅的陆架、陡峭的大陆坡和深洋盆。这种地形特征是极地和副极地边缘海的典型特征。结果表明,与最近引入的地形约束综合成图程序相比,SSC综合成图大大降低了宽陆架和浅陆架的成图误差。我们还在南大洋测试了我们的测绘方案,南大洋有一个相对倾斜的大陆架、一个更宽更平缓的斜坡和一个又深又宽的洋盆。我们发现SSCI和TCI方法在那里实际上是等效的。因此,SSCI绘图是绘制各种地形环境中海洋特性的有效方法,在所有极地和亚极地都应该足够。重要的是,我们引入了一种标准化程序,用于在任何地形条件下确定去相关长度尺度——这是实施任何测绘方案之前的必要步骤。
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引用次数: 0
Masthead 报头
IF 2.2 4区 地球科学 Q2 ENGINEERING, OCEAN Pub Date : 2023-08-01 DOI: 10.1175/jtech-408masthead
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引用次数: 0
Estimation of transmitted differential phase on dual polarization radars 双偏振雷达上传输差相位的估计
IF 2.2 4区 地球科学 Q2 ENGINEERING, OCEAN Pub Date : 2023-07-27 DOI: 10.1175/jtech-d-22-0014.1
D. Zrnić, V. Melnikov
A measurement procedure to determine transmitted differential phase between horizontally and vertically polarized radiation of a dual polarization radar is presented. It is applicable to radars that transmit and receive Simultaneously Horizontally and Vertically (SHV) polarized waves. The method relies solely on weather data with no instrument intrusions whatsoever. It takes data at vertical incidence while the antenna rotates in azimuth. That way a large number of samples is collected to reduce statistical errors in estimates. The theory indicates that the transmitted differential phase appears prominently in the backscatter signals off the melting layer. That and relations between various elements of the backscattering matrix are used to derive a set of nonlinear equations whereby the differential phase on transmission is one of the unknowns. Steps for solving these equations are presented as well as a demonstration of the results on radar data. Finally, a simplified algorithm that bypasses the coupled nonlinear equations is exposed. Conditions under which the simplification can be applied are presented. These restrict the range of the transmitted differential phase for which the simplified procedure may be applied.
提出了一种确定双极化雷达水平和垂直极化辐射之间传输差相位的测量方法。它适用于同时发射和接收水平和垂直(SHV)极化波的雷达。该方法完全依赖于天气数据,没有任何仪器入侵。当天线在方位角上旋转时,它以垂直入射角获取数据。这样可以收集大量样本,以减少估计中的统计误差。该理论表明,透射微分相位在熔化层外的反向散射信号中表现突出。这一点以及后向散射矩阵的各个元素之间的关系被用来导出一组非线性方程,其中传输时的微分相位是未知数之一。给出了求解这些方程的步骤,并对雷达数据的结果进行了演示。最后,给出了一种绕过耦合非线性方程组的简化算法。给出了可以应用简化的条件。这些限制了可以应用简化过程的传输差分相位的范围。
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引用次数: 0
Estimation of Surface Current Divergence from Satellite Doppler Radar Scatterometer Measurements of Surface Ocean Velocity 卫星多普勒雷达散射仪测量海面流速估算海面海流发散
IF 2.2 4区 地球科学 Q2 ENGINEERING, OCEAN Pub Date : 2023-07-24 DOI: 10.1175/jtech-d-23-0052.1
D. Chelton
The ability to estimate surface current divergence and vorticity from space is assessed from simulated satellite Doppler radar scatterometer measurements of surface velocity with an effective footprint diameter of 5 km across an 1800-km measurement swath. The focus is on non-internal-wave contributions to divergence and vorticity. This is achieved by simulating Doppler measurements of surface velocity from a numerical model in which internal waves are weak because of high dissipation, seasonal cycle forcing and the lack of tidal forcing. Divergence is much more challenging to estimate than vorticity because the signals are weaker and restricted to smaller scales. With the measurement noise that was anticipated based on early engineering studies, divergence cannot be estimated with useful resolution. Recent advances in the understanding of how the noise in measurements of surface currents depends on the ambient wind speed have concluded that measurement noise will be substantially smaller in conditions of wind speed greater than 6 m s−1. A reassessment of the ability to estimate non-internal-wave contributions to surface current divergence in this study finds that useful estimates can be obtained in such wind conditions; the wavelength resolution capability for divergence estimates in the middle of the measurement swaths will be better than 100 km in 16-day averages. The improved measurement accuracy will also provide estimates of surface current vorticity with a resolution nearly a factor-of-2 higher than was previously thought, resulting in wavelength resolutions of about 50 km, 30 km and 20 km in snapshots, 4-day averages and 16-day averages, respectively.
通过模拟卫星多普勒雷达散射仪对1800公里测量带上有效足迹直径为5公里的表面速度的测量,评估了从空间估计表面电流散度和涡度的能力。重点是非内波对散度和涡度的贡献。这是通过模拟数值模型中表面速度的多普勒测量来实现的,在该模型中,由于高耗散、季节性周期强迫和缺乏潮汐强迫,内波较弱。散度比涡度更难估计,因为信号较弱,并且局限于较小的尺度。由于测量噪声是基于早期工程研究预期的,因此无法用有用的分辨率来估计偏差。在理解表面电流测量中的噪声如何取决于环境风速方面的最新进展表明,在风速大于6 m s−1的情况下,测量噪声将显著较小。在这项研究中,对估计非内波对地表电流发散的贡献的能力进行了重新评估,发现在这种风况下可以获得有用的估计;在16天的平均值中,测量带中间的发散估计的波长分辨率能力将优于100km。测量精度的提高还将提供表面流涡度的估计,其分辨率比之前认为的高出近2倍,从而在快照、4天平均值和16天平均值中分别获得约50公里、30公里和20公里的波长分辨率。
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引用次数: 0
Performance Evaluation of the Lightning Imaging Sensor on the International Space Station 国际空间站雷电成像传感器性能评价
IF 2.2 4区 地球科学 Q2 ENGINEERING, OCEAN Pub Date : 2023-07-21 DOI: 10.1175/jtech-d-22-0120.1
Daile Zhang, K. Cummins, T. Lang, D. Buechler, S. Rudlosky
Optical lightning observations from low-Earth orbit play an important role in our understanding of long-term global lightning trends. Lightning Imaging Sensors (LIS) on the Tropical Rainfall Measurement Mission (TRMM) satellite (1997-2015) and International Space Station (2017-present) capture optical emissions produced by lightning. This study uses the well-documented TRMM LIS performance to determine if the ISS LIS performs well enough to bridge the gap between TRMM LIS and the new generation of Geostationary Lightning Mappers (GLMs). The average events per group and groups per flash for ISS LIS are 3.6 and 9.9, which are 25% and 10% lower than TRMM LIS, respectively. ISS LIS has 30% lower mean group energy density and 30-50% lower mean flash energy density than TRMM LIS in their common (+/−38 degree) latitude range. These differences are likely the result of larger pixel areas for ISS LIS over most of the field-of-view due to off-nadir pointing, combined with viewing obstructions and possible engineering differences. For both instruments, radiometric sensitivity decreases radially from the center of the array to the edges. ISS LIS sensitivity falls-off faster and more-variably, contributed to by the off-nadir pointing. Event energy density analysis indicate some anomalous hotspot pixels in the ISS LIS pixel array that were not present with the TRMM LIS. Despite these differences, ISS LIS provides similar parameter values to TRMM LIS with the expectation of somewhat lower lightning detection capability. In addition, recalculation of the event, group, and flash areas for both LIS datasets are strongly recommended since the archived values in the current release versions have significant errors.
近地轨道光学闪电观测对我们了解长期全球闪电趋势起着重要作用。热带降雨测量任务(TRMM)卫星(1997-2015年)和国际空间站(2017年至今)上的闪电成像传感器(LIS)捕获闪电产生的光发射。本研究使用记录良好的TRMM LIS性能来确定ISS LIS是否表现良好,足以弥补TRMM LIS与新一代地球静止闪电绘图仪(GLMs)之间的差距。ISS LIS每组和每组闪光的平均事件数分别为3.6和9.9,分别比TRMM LIS低25%和10%。在其共同纬度(+/−38度)范围内,ISS LIS的平均基团能量密度比TRMM LIS低30%,平均闪光能量密度比TRMM LIS低30-50%。这些差异可能是由于ISS LIS在大多数视场中由于非最低点指向而产生的较大像素区域,再加上观看障碍和可能的工程差异。对于这两种仪器,辐射灵敏度从阵列中心到边缘呈放射状递减。ISS的灵敏度下降得更快,变化更大,这是由非最低点指向造成的。事件能量密度分析表明,在ISS LIS像元阵列中存在TRMM LIS不存在的异常热点像元。尽管存在这些差异,ISS LIS提供了与TRMM LIS相似的参数值,但预期闪电探测能力略低。此外,强烈建议重新计算两个LIS数据集的事件、组和flash区域,因为当前发布版本中的存档值存在重大错误。
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引用次数: 0
Diagnosing seasonal forecast skill of the Indian Ocean Dipole mode using model-analogs 用模式类似物诊断印度洋偶极子模式的季节预报技巧
IF 2.2 4区 地球科学 Q2 ENGINEERING, OCEAN Pub Date : 2023-07-20 DOI: 10.1175/jtech-d-22-0106.1
Yanling Wu, Youmin Tang
A retrospective tropical Indian Ocean Dipole mode (IOD) hindcast for 1958–2014 was conducted using 20 models from the sixth phase of the Coupled Model Intercomparison Project (CMIP6), with a model-based analog forecast (MAF) method. In the MAF approach, forecast ensembles are extracted from preexisting model simulations by finding the states that initially best match an observed anomaly and tracking their subsequent evolution, with no additional model integrations. By optimizing the key factors in the MAF method, we suggest that the optimal do main for the analog criteria should be concentrated in the tropical Indian Ocean region for IOD predictions. Including external forcing trends improves the skills of the east and west poles of the IOD, but not the IOD prediction itself. The MAF IOD prediction showed comparable skills to the assimilation-initialized hindcast, with skillful predictions corresponding to a 4- and 3-month lead respectively. The IOD forecast skills had significant decadal variations during the 55-year period, with low skills after the early 2000s and before 1985 and high skills during 1985–2000. This work offers a computational efficiency and practical approach for seasonal prediction of the tropical Indian Ocean sea surface temperature.
利用耦合模式比对项目(CMIP6)第6阶段的20个模式,采用基于模式的模拟预报(MAF)方法,对1958-2014年热带印度洋偶极子模式(IOD)进行了回顾性预报。在MAF方法中,通过寻找最初与观测到的异常最匹配的状态并跟踪其后续演变,从预先存在的模型模拟中提取预报集合,而无需额外的模型集成。通过对MAF方法中关键因子的优化,我们建议在IOD预测中,模拟判据的最佳区域应集中在热带印度洋地区。包括外部强迫趋势可以提高IOD东极和西极的技能,但不能提高IOD预测本身。MAF IOD预测显示出与同化初始化预测相当的技能,熟练的预测分别对应于4个月和3个月的领先。IOD预测技能在55 a期间具有显著的年代际变化,2000年代初以后和1985年以前技能较低,1985—2000年技能较高。本研究为热带印度洋海表温度的季节预报提供了计算效率和实用方法。
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引用次数: 0
Optimizing The Biogeochemical Argo Float Distribution 优化生物地球化学Argo浮体分布
IF 2.2 4区 地球科学 Q2 ENGINEERING, OCEAN Pub Date : 2023-07-12 DOI: 10.1175/jtech-d-22-0093.1
P. Chamberlain, L. Talley, B. Cornuelle, M. Mazloff, S. Gille
The core Argo array has operated with the design goal of uniform spatial distribution of 3° in latitude and longitude. Recent studies have acknowledged that spatial and temporal scales of variability in some parts of the ocean are not resolved by 3° sampling and have recommended increased core Argo density in the equatorial region, boundary currents, and marginal seas with an integrated vision of other Argo variants. Biogeochemical (BGC) Argo floats currently observe the ocean from a collection of pilot arrays, but recently funded proposals will transition these pilot arrays to a global array. The current BGC Argo implementation plan recommends uniform spatial distribution of BGC Argo floats. For the first time, we estimate the effectiveness of the existing BGC Argo array to resolve the anomaly from the mean using a subset of modeled, full-depth BGC fields. We also study the effectiveness of uniformly-distributed BGC Argo arrays with varying float densities at observing the ocean. Then, using previous Argo trajectories, we estimate the Argo array’s future distribution and quantify how well it observes the ocean. Finally, using a novel technique for sequentially identifying the best deployment locations, we suggest the optimal array distribution for BGC Argo floats to minimize objective mapping uncertainty in a subset of BGC fields and to best constrain BGC temporal variability.
核心Argo阵列以经纬度均匀分布3°的设计目标运行。最近的研究已经认识到,海洋某些部分的时空变率不能通过3°采样来解决,并建议在综合考虑其他Argo变异体的情况下,增加赤道地区、边界流和边缘海的核心Argo密度。生物地球化学(BGC) Argo浮标目前通过一系列试点阵列观察海洋,但最近资助的提案将把这些试点阵列转变为全球阵列。目前的BGC Argo实施计划建议BGC Argo浮子的均匀空间分布。我们首次估计了现有BGC Argo阵列使用模拟的全深度BGC油田子集从平均值中解决异常的有效性。我们还研究了不同浮子密度的均匀分布BGC Argo阵列在海洋观测中的有效性。然后,利用以前的Argo轨迹,我们估计了Argo阵列未来的分布,并量化了它对海洋的观察程度。最后,利用一种新的顺序识别最佳部署位置的技术,我们提出了BGC Argo浮标的最佳阵列分布,以最大限度地减少BGC字段子集的客观映射不确定性,并最好地约束BGC的时间变异性。
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引用次数: 0
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