国际Argo计划执行现状剖析

国际Argo计划自2000年实施以来,世界上25个国家和团体已经在全球海洋中布放了5000余个Argo浮标,其中在海上正常工作的浮标已经超过3000个。这标志着全球Argo实时海洋观测网已经全面建成。文中将系统介绍国际Argo计划主要成员国在浮标布放、回收和Argo资料管理等方面所作出的贡献,以帮助读者对这21世纪的重大国际海洋观测计划有一较全面、深入的了解。     

An estimation of the average lifetime of the latest model of APEX floats

Estimating the average lifetime of floats is very important for Argo, because the total cost of maintaining the monitoring network largely depends on float lifetime. However, the actual lifetime of floats used in Argo is currently unknown. An estimate can be made by examining past float survival, but this is complicated by floats still operating at sea and continuous improvements in float hardware. Because APEX (Autonomous Profiling Explorer) floats are the most widely deployed type of float in the world oceans, in this study we estimate the lifetime of the latest model of APEX powered by alkaline batteries. The expected lifetime is estimated with a statistical method that allows for floats that are still active and that failed because of a known and now fixed hardware fault that should not cause failure in the latest model of floats. As an example, we analyzed the APEX fleets managed by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), because we have access to a JAMSTEC database in which the causes of float failure have been carefully correlated to known hardware problems. Analysis of the JAMSTEC fleet (n = 571, as of 7 May 2008) indicated that the expected lifetime of the latest model of APEX is 134.6 (127.6–141.5, considering standard errors) cycles, equivalent to 3.7 years of 10-day cycles. We conclude that the annual deployment of 813 (773–859) APEX floats is needed to maintain the Argo observational network of 3000 floats. Floats with different hardware configurations (e.g., lithium batteries) or different mission programs (e.g., shallower profiling, deeper profiling every several cycles) may be expected to have an even longer lifetime.     

Long-term Sensor Drift Found in Recovered Argo Profiling Floats

We recovered three Argo profiling floats after 2 to 2.5 years of operation, and recalibrated their temperature, conductivity, and pressure sensors. The results demonstrate that these floats exhibited a significant drift in salinity of −0.0074 to −0.0125, primarily due to the conductivity sensor drift. Combined with the recalibration result for another previously recovered float, the indication is that the negative salinity drift increases nearly in proportion to the operating period of floats. The increasing rate is −0.0041 (±0.0015) year⁻¹, which yields a salinity drift of −0.016 (±0.006) for the expected float lifetime of four years. The present result suggests that reducing the float surfacing time would improve the accuracy of the salinity measurements.     

阵列筏式波浪能发电装置建模与仿真分析

为了提高阵列筏式波浪能发电装置采能效率,对不同排列方式的振荡浮子与不同楔形角的试验平台模型进行组合,优化水动力结构模型装置。建立了振荡浮子和采能装置试验平台三维模型,并进行了仿真分析。分别分析了由3种排列方式的振荡浮子和3种楔形角情况下的9种模型在水深15 m、平台吃水1.2 m、振荡浮子吃水0.5 m海况下垂直方向的时域响应和频域响应,结果发现当模型的振荡浮子以错开方式排列且试验平台楔形角为60°时,振荡浮子在垂直方向的振荡速度最快,其RAO值也最大,说明该组合模型更有利于提高筏式波浪能发电装置的采能效率。     

基于拉格朗日方法的南海自动剖面浮标轨迹模拟系统*

南海自动剖面浮标轨迹模拟系统包括高分辨率模式流场、拉格朗日追踪模型和垂向浮标运动参数化方案等三个核心部分。该系统可在南海范围内模拟两类自动剖面浮标: 传统自动剖面浮标(停滞深度为1000m, 最大下潜深度为2000m)和新型深海自动剖面浮标(停滞深度为距海底500m)。通过对南海现有的6个传统浮标的模拟, 该系统可以预测其100d内的漂流轨迹。通过与真实浮标轨迹数据的对比, 验证了该模拟系统的准确性。此外, 根据该系统, 我们初步探讨了深海自动剖面浮标阵列(时空分辨率为2°×2°×30d)在南海内区布放方案的可行性。该模拟系统的建立和完善将有助于对现有传统剖面浮标布放策略进行优化, 并对未来深海剖面浮标在南海的推广应用提供初步的理论依据。     

Pre-Japan-ARGO: Experimental Observation of Upper and Middle Layers South of the Kuroshio Extension Region Using Profiling Floats

We deployed two profiling floats in the region south of the Kuroshio Extension in March 2000. Temperature and salinity profiles from a depth of 1500 × 10⁴ Pa to the surface are reported every two and four weeks, respectively. The floats performed very well for first four months after deployment. Later they failed in surfacing for a few months when the sea surface temperature in the region was high. The salinity sensors seemed to suffer from some damage during their failure-in-surfacing period. Despite this trouble, the results clearly demonstrate that the profiling float is a very useful and cost-effective tool for physical oceanographic observation in the open sea. This revised version was published online in July 2006 with corrections to the Cover Date.     

基于机器学习的海洋浮标寿命及轨迹预测

Argo计划(Array or Real-time Geostrophic Oceanography)为海洋和大气研究提供了宝贵的资料,在短期天气预报和长期气候预测中起到了重要作用。为保证Argo观测阵列的正常运转,需要时刻关注浮标的运行状态,以保证研究区域内维持一定数量和密度的浮标。然而Argo浮标投放费用高昂,投放过早会导致资源浪费,投放过迟会导致信息资料的缺失。本文旨在使用机器学习的方法对Argo浮标在未来某个时间点的位置和状态(仍在工作或已经损坏)进行预测,以提前制定投放计划,保证在正确的位置和时间投放新的浮标,以减少资金投入。对于浮标寿命预测任务,除硬件特征之外添加额外的已存活时间作为动态属性,使用回归决策树、梯度提升回归树、随机森林和支持向量回归机等机器学习方法,对浮标剩余寿命进行预测。对于浮标轨迹预测任务,使用基于LSTM的Encoder-Decoder模型对未来多个时间步后的浮标的经/纬度信息进行预测,有效地避免了传统的LSTM模型循环单步预测所带来的误差累积问题。实验证明本文提出的浮标剩余寿命和位置预测模型都能达到较高的预测准确率,对指导浮标投放有重要意义。     

Large capacity multi-float configurations for the wave energy converter M4 using a time-domain linear diffraction model

The moored three-float line absorber WEC M4 has been developed to optimise power capture through experiments and linear diffraction modelling. With the progression down wave from small to medium to large floats, the device heads naturally into the wave direction. The bow and mid floats are rigidly connected by a beam and a beam from the stern float is connected to the hinge point above the mid float for power take off (PTO). Increasing the bow to mid float spacing to be more than 50% greater than the mid to stern float spacing has been found to improve power capture. To increase power capture further and potentially reduce electricity generation cost the number of mid floats and stern floats is increased while maintaining a single bow float for mooring connection. The bow and mid floats still form a rigid body while the stern floats may respond independently. A time domain linear diffraction model based on Cummins method has been applied to configurations of 121, 123, 132, 133, and 134 floats where the numbers indicate the number of floats: bow, mid, stern. This shows how power capture is increased while response remains similar. We only consider uni-directional (long-crested) waves with narrow band width typical of swell. By considering scatter diagrams for various offshore sites capacities may range from 3.7 MW to 17.3 MW for the eight float system with a capacity factor of 1/3 while the cost of electricity assuming capital cost to be a fixed multiple of steel cost is reduced from that for the three-float system.     

Twenty years of ocean observations with China Argo

The international Argo program, a global observational array of nearly 4 000 autonomous profiling floats initiated in the late 1990s, which measures the water temperature and salinity of the upper 2 000 m of the global ocean, has revolutionized oceanography. It has been recognized one of the most successful ocean observation systems in the world. Today, the proposed decade action “OneArgo” for building an integrated global, full-depth, and multidisciplinary ocean observing array for beyond 2020 ...     

Formation Process of North Pacific Intermediate Water Revealed by Profiling Floats Set to Drift on 26.7 σθ Isopycnal Surface

Six newly developed floats, which were set to drift on the 26.7 σ_θ isopycnal surface and to profile temperature, salinity and pressure above 1000 dbar once a week, were deployed in the Oyashio and Kuroshio Extension (KE) in order to examine the circulation, formation site and time scale of newly formed North Pacific Intermediate Water (NPIW). The floats were deployed in February or May 2001, and the data from their deployments to December 2002 are analyzed here. Four of the six floats were deployed near the KE axis at around the first meander crest, and they moved eastward to 157°E–176°W at latitudes of 30°N–45°N. The other two floats deployed in the Oyashio water with low-potential vorticity near the south coast of Hokkaido moved southward to reach the KE front and then moved eastward to the same region as the first four floats. The temperature and salinity at 26.7 σ_θ measured by the profiling floats indicate that the source waters of NPIW, Oyashio and Kuroshio waters are drastically mixed and modified in the mixed water region west of 160°E. The floats were separated into the three paths east of 160°E between the Kuroshio Extension front and the north of Water-Mass front (nearly subarctic front). New NPIW is judged to be formed along these three paths since the vertical profiles of temperature and salinity are quite smooth, having a salinity minimum at about 26.7σ_θ along each path. Kuroshio-Oyashio isopycnal mixing ratios of the new NPIW are 7:3, 6:4 and 5:5 at 26.7σ_θ along the southern, middle and northern paths, respectively. Potential vorticity converges to about 14–15 × 10⁻¹¹ m⁻¹s⁻¹ along these paths. The time scale of new NPIW formation is estimated to be 1–1.5 years from the merger of Oyashio and Kuroshio waters to the formation of the new NPIW. This revised version was published online in July 2006 with corrections to the Cover Date.     

Agulhas leakage into the Atlantic estimated with subsurface floats and surface drifters

Surface drifters and subsurface floats drifting at depths near 800 m were used to study the pathways of warm, salty Indian Ocean water leaking into the South Atlantic that is a component of the upper limb of the Atlantic meridional overturning circulation (MOC). Four drifters and 5 floats drifted from the Agulhas Current directly into the Benguela Current. Others looped for various amounts of time in Agulhas rings and cyclones, which translated westward into the Atlantic, contributing a large part of Indian Ocean leakage. Agulhas rings translated into the Benguela Current, where they slowly decayed. Some large, blob-like Agulhas rings with irregular shapes were found in the southeastern Cape Basin. Drifter trajectories suggest these rings become more circular with time, eventually evolving into the circular rings observed west of the Walvis Ridge. Agulhas cyclones, which form on the north side of the Agulhas Current south of Africa, translated southwestward (to 6°E) and contributed water to the southern Cape Basin. A new discovery is a westward extension from the mean Agulhas retroflection measured by westward drifting floats near 41°S out to at least 5°W, with some floats as far west as 25°W. The Agulhas extension appears to split the South Atlantic Current (SAC) into two branches and to transport Agulhas water westward, where it is mixed and blended with eastward-flowing water from the western Atlantic. The blended mixture flows northeastward in the northern branch of the SAC and into the Benguela Current. Agulhas leakage transport was estimated from drifters and floats to be at least 15 Sv in the upper 1000 m, which is equivalent to the transport of the upper layer MOC. It is suggested that the major component of the upper layer overturning circulation in the Atlantic is Agulhas leakage in the form of Agulhas rings.     

Detection of Intermediate Mediterranean Waters in the Atlantic Ocean by ARGO Floats Data

Peculiarities of the spatial distribution of intermediate Mediterranean waters (MW), which are the main source to maintain the heat and salt budgets at depths of 600–1500 m in the Atlantic Ocean, have been studied using the ARGO floats measurements database. About 75000 temperature and salinity profiles recorded by 900 ARGO floats in 2005–2014 in the Atlantic Ocean for latitudes from 20° to 50° N were used. To process these data, we used the ARGO-Based Model for Investigation of the Global Ocean (AMIGO). This technique allowed us for the first time to obtain a complete set of oceanographic characteristics up to a depth of 2000 m for different time averaging intervals (month, season, years). Joint analysis of the temperature, salinity, and velocity distributions at 700–1000 m depths made it possible to revise the distribution of MW and their penetration into the western part of the ocean across the Mid-Atlantic Ridge (MAR). It is shown that at depths of 700 and 1000 m, the Mid-Atlantic Ridge is a barrier to advective propagation of salty waters (>35.5 PSU) to the west and is transparent to fragments of destroyed intrathermocline lenses (ITL) with lower salinity (<35.4 PSU). In the Atlantic region, from 20° to 35° N and from 30° to 70° W, individual lens profiles with an anomalous salinity distribution were sought using ARGO measurements to detect ITL and its separate fragments. About 24 000 measurements from 370 ARGO floats were analyzed, and only about 3% of them showed weak salinity anomalies at 800–1200 m depths. No ITL were found from these observations. Analysis of long-term drifting of individual floats recording temperature and salinity profiles with anomalous layers made it possible to study the nature of MW transport through the MAR.     

一种海洋潜标适用的新型GPS信标机

本研究设计了一种潜标适用的新型信标机,它集成了GPS模块、数传模块、微处理器和压力开关等部件,可有效提高潜标回收过程中的目标定位能力。该信标机安装于潜标主浮体,通过压力开关控制电源。当主浮体位于海面时,信标机处于工作状态,它可以不断地将GPS位置数据通过无线传输方式向外发送,配套的接收端可以将接收的位置信息直观地显示在...     

Convective structures in the Lofoten Basin based on satellite and Argo data

We discuss the possibility of detecting deep convection in the Lofoten Basin of the Norwegian Sea based on the eddy structures revealed from the satellite data. Satellite altimetry, SAR imagery, and MODIS satellite spectral radiometer sea-surface temperature (SST) data are used in the analysis, along with the data of oceanographic Argo floats. It is shown that the eddies identified from the satellite data correspond to the convective cells in the same region according to the data of the Argo floats. We consider several examples of the summer eddy and one winter eddy and the corresponding structures in the ocean measured by the Argo floats when they were located close to the identified eddies. As this method develops and improves, it can be used for the analysis of the dynamic of oceanic eddies in the region of the Lofoten Basin, and possibly in other regions with active deep convection.     

Significant salinity increase in subsurface waters of the South China Sea during 2016–2017

The South China Sea(SCS) is the largest semi-enclosed marginal sea in the North Pacific. Salinity changes in the SCS play an important role in regional and global ocean circulation and the hydrological cycle. However, there are few studies on salinity changes over the SCS due to lack of high-quality and long-term observations. In the past decade, the deployment of floats from the Argo program in the SCS and their accumulated temperature and salinity profiles have made it possible for us to examine salinity changes over the entire basin. In this study,salinity changes were investigated with Argo and underwater glider temperature and salinity observations and gridded temperature–salinity objective analyses(UK Met Office Hadley Centre EN4.2.1 objective analysis and China Argo Real-time Data Center BOA_Argo). The results indicated that the subsurface water in the entire SCS became significantly saltier during 2016–2017. The most significant salinity increase was found during 2016 in the northeastern SCS. The subsurface water in the northeastern SCS exhibited a salinity maximum above 35, which was recorded by three Argo floats during 2015–2016. Such high salinity water was rarely observed and reported prior to the Argo era. Average salinity of 2016–2017 along the 25.5σ_θ–23.5σ_θ isopycnal surfaces in the whole SCS is 0.014-0.130 higher than the climatology. Increases in subsurface salinity started from the northeastern SCS and extended southwestward gradually. Moreover, the subsurface salinity changes, especially in the northern SCS,exhibited a semiannual lead behind the subsurface Luzon Strait transport. Further analysis indicated that the predominance of advection, driven by subsurface Luzon Strait transport, led to salinification along the western boundary of the SCS. In other parts of the SCS, negative wind stress curl trends tended to preserve the high salinity characteristics of the subsurface water.     

Monthly Variability of Mixed Layer over Arabian Sea Using ARGO Data

The mixed layer depths over the Arabian Sea were computed for the three successive years 2004-2006 using ARGO floats data. The large availability of ARGO floats for the above period resulted in better estimation of mixed layer depth (MLD) over the Arabian Sea. The results were compared with World Ocean Atlas 1994 MLD Climatology. Marked variability in MLD on a monthly time scale is observed and it was in accordance with the wind stress and/or net heat gain variability, which are the principal factors influencing mixed layer over Arabian Sea. With the availability of large number of ARGO profile data, an attempt is made to study the monthly variability of Mixed Layer.     

Isothermal,mixed, and barrier layers in the subtropical and tropical Atlantic Ocean during the ARAMIS experiment

The ARAMIS project (Altimétrie sur un Rail Atlantique et Mesures In Situ) provides a long term survey (2002–2008) for thermohaline structures in the tropical Atlantic Ocean. Here, these data are used to address questions regarding the existence and formation of barrier layers. The analysis presented which uses different criteria to calculate isothermal layer depth and mixed layer depth, shows the sensitivity of different methods to a variety of variables. A 0.5 °C criterion for the isothermal layer and its equivalent in density change for the mixed layer are found to be the most adaptable due to their robustness. Barrier layers observed with ARAMIS data sets are in good agreement with climatologies and in-situ Argo floats along the route. Three systems of barrier layers are observed during the voyages. Their variability and formation as described in previous works concerned with the tropical Atlantic are analyzed. Different processes such as subduction, frontal activity, and precipitation are needed to explain their presence.     

Evolution and decay of a warm-core ring within the western subarctic gyre of the North Pacific,as observed by profiling floats

This study investigated temporal variations in the vertical structure and water properties of a warm-core ring that migrated into the western subarctic gyre of the North Pacific, based on analyses of temperature and salinity data derived from two profiling floats, together with shipboard and satellite observation data. The floats were initially deployed into cold and fresh Oyashio water in September 2003, and were entrained into a warm-core ring in October 2003, remaining within the ring until detrainment in December 2004. Drastic cooling and freshening of the upper core water of the ring were observed during the above entrainment of the floats with cold and fresh water into the ring, whereas moderate variations in structure and water properties were observed during a quasi-isolated phase from November 2003 to November 2004 when the ring did not experience major interactions with ambient hydrographic features. The upper part of the core water (upper core), with relatively warm/saline water above 26.6 σ _θ , was under the influence of the atmosphere in winter via the formation of a deep mixed layer exceeding 300 dB, and had a prominent pycnostad below the seasonal pycnocline from spring to autumn. In contrast, the lower core, with relatively cold and fresh water below 26.6 σ _θ , was not ventilated throughout the observation period. Isopycnal surfaces showed a shoaling trend of about 50 dB/year during the quasi-isolated phase, suggesting viscous decay over a timescale of several years. Markedly cold and thick water was also frequently observed within the ring, indicating the intrusion of water from the Sea of Okhotsk.     

Stability of Temperature and Conductivity Sensors of Argo Profiling Floats

After recalibration of the temperature and conductivity sensors of three Argo profiling floats recovered after operations for four to nine months, the results indicate that the floats basically showed no significant drift, either in temperature or salinity, and adequately fulfilled the accuracy requirement of the Argo project (0.005°C for temperature and 0.01 psu for salinity). Only the third float showed a significant offset in salinity of about −0.02 psu, as expected from comparison between the float data and the shipboard conductivity-temperature-depth data. This offset was caused by the operational error of the PROVOR-type float, in which the surface water was pumped immediately after the launch, fouling the conductivity sensor cell. This revised version was published online in July 2006 with corrections to the Cover Date.     

利用Argo剖面浮标分析上层海洋对台风“布拉万”的响应

In situ observations from Argo profiling floats combined with satellite retrieved SST and rain rate are used to investigate an upper ocean response to Typhoon Bolaven from 20 through 29 August 2012. After the passage of Typhoon Bolaven, the deepening of mixed layer depth(MLD), and the cooling of mixed layer temperature(MLT) were observed. The changes in mixed layer salinity(MLS) showed an equivalent number of increasing and decreasing because the typhoon-induced salinity changes in the mixed layer were influenced by precipitation, evaporation, turbulent mixing and upwelling of thermocline water. The deepening of the MLD and the cooling of the MLT indicated a significant rightward bias, whereas the MLS was freshened to the left side of the typhoon track and increased on the other side. Intensive temperature and salinity profiles observed by Iridium floats make it possible to view response processes in the upper ocean after the passage of a typhoon. The cooling in the near-surface and the warming in the subsurface were observed by two Iridium floats located to the left side of the cyclonic track during the development stage of the storm, beyond the radius of maximum winds relative to the typhoon center. Water salinity increases at the base of the mixed layer and the top of the thermocline were the most obvious change observed by those two floats. On the right side of the track and near the typhoon center when the typhoon was intensified, the significant cooling from sea surface to a depth of 200×104 Pa, with the exception of the water at the top of the thermocline, was observed by the other Iridium float. Owing to the enhanced upwelling near the typhoon center, the water salinity in the near-surface increased noticeably. The heat pumping from the mixed layer into the thermocline induced by downwelling and the upwelling induced by the positive wind stress curl are the main causes for the different temperature and salinity variations on the different sides of the track. It seems that more time is required for the anomalies in the subsurface to be restored to pretyphoon conditions than for the anomalies in the mixed layer.