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We provide a novel method and tool for computing the most likely path taken by drifters between arbitrary fixed locations in the ocean. In addition to this we provide an estimate of the travel time associated with the path. Lagrangian pathways and travel times are of practical value not just in understanding surface currents, but also in modelling the transport of ocean-borne species such as planktonic organisms, and floating debris such as plastics. To demonstrate the capabilities of this method we show emperical results derived from the Global Drifter Program data. We use the drifter data to construct Markov transition matrices and apply Dijkstra's algorithm to find the most likely paths. The novelty is that we apply hexagonal tessellation of the ocean using Uber's H3 index (which we show is far superior to the standard practice of rectangular or lat-lon gridding). Furthermore, we provide techniques for measuring uncertainty by bootstrapping and applying rotations to the hexagonal grid. The methodology is purely data-driven, and requires no simulations of drifter trajectories. The method scales globally and is computationally efficient.

Accurate estimates and forecasts of physical and biogeochemical processes at the air-sea interface must rely on integrated in-situ and satellite surface observations of essential Ocean/Climate Variables (EOVs /ECVs). Such observations, when sustained over appropriate temporal and spatial scales, are particularly powerful in constraining and improving the skills, impact and value of weather, ocean and climate forecast models. The calibration and validation of satellite ocean products also rely on in-situ observations, thus creating further positive high-impact applications of observing systems designed for global sustained observations of EOV and ECVs.The Global Drifter Program has operated uninterrupted for several decades and constitutes a particular successful example of a network of multiparametric platforms providing observations of climate, weather and oceanographic relevance (e.g. air-pressure, sea surface temperature, ocean currents). This presentation will review the requirements of sustainability of an observing system such as the GDP (i.e. cost effectiveness, peer-review of the observing methodology and of the technology, free data access and international cooperation), will present some key metrics recently used to quantify the impact of drifter observations, and will discuss two prominent examples of GDP regional observations and the transition to operations of novel platforms, such us wind and directional wave spectra drifters, in sparsely sampled regions of the Arabian Sea and of the North Atlantic Ocean.

Mixing by mesoscale eddies in the ocean plays a major role in setting the distribution of oceanic tracers, with important implications for physical and biochemical systems at local to global scales. Roach et al. (2016; https://doi.org/10.1002/2015JC011440) demonstrated that a two‐particle analysis of Argo trajectories produces robust estimates of horizontal mixing in the Southern Ocean. Here we extend this analysis to produce global 1° × 1° maps of eddy diffusivity at the nominal Argo parking depth of 1,000 m. We also applied this methodology to estimate surface eddy diffusivities from Global Drifter Program (GDP) surface drifters. The global mean eddy diffusivity was 543 ± 155 m2/s at 1,000 m and 2637 ± 311 m2/s at the surface, with elevated diffusivities in regions of enhanced eddy kinetic energy, such as western boundary currents and along the Antarctic Circumpolar Current. The eddy kinetic energy at the equator is high at both the surface and depth, but the eddy diffusivity is only enhanced near the surface. At depth the eddy diffusivity is strongly suppressed due to the presence of mean flow. We used our observational estimates to test the validity of an eddy diffusivity parameterization that accounts for mixing suppression in the presence of zonal mean flows. Our results indicated that this parameterization generally agrees with the directly observed eddy diffusivities in the midlatitude and high‐latitude oceans.

In the Northeast Pacific (40–50°N, 135–180°W), the angle between the wind friction velocity ( u * ) and the current observed by drifters with subsurface float (Global Drifter Program Version 1; GDP-V1) was found to be consistently 10–15° larger at all frequencies than the angle observed by drifters without subsurface float (Global Drifter Program Version 2; GDP-V2). To investigate the cause, cross-spectral analysis and vector regression between the wind and current were performed after carefully screening drifter tracks to study the wind-driven currents observed by drifters with different configurations. Vector regression analysis between the wind and current revealed that the angle of wind-driven current observed by GDP-V1 drifters was 10–13° larger for u * −1 compared to that observed by GDP-V2 drifters. One possible explanation for a smaller angle between wind and current from drifters without subsurface float is the shallowing of observed depth due to the shrinking of the holey sock drogue induced by surface wave action. The depth of the current observed by GDP-V2 drifters during the winter was estimated using the observed angle and the e-folding depth calculated from the angle at 15 m by GDP-V1 drifters. In the winter, the mean depth of the wind-driven current observed by GDP-V2 drifters, which have been deployed since the early 2000s, was approximately in the range of 8–10 m depending on the estimation of the e-folding depth either from the angle change or from the amplitude decay in the Ekman layer. Except for the friction velocity exceeding 1.5 cm s −1 , a nearly constant amplitude between surface current and friction velocity at all friction velocity ranges is another finding in our study.

Surface drift of eighty-nine undrogued RAFOS floats in the California Current System (CCS) has been studied to describe patterns of flotsam drift, its seasonal variability and predictability limitations. The floats were launched in the California Undercurrent during 1992–2010 and were tracked by the ARGOS system when they surfaced at the end of their subsurface missions. The duration of surface trajectories varied from as short as 11 to as long as 280 days. The surface drift of these floats was typically equatorward in the California Current. However, some floats moved poleward into the Subpolar Gyre, and others drifted westward into the North Equatorial Current. Usually, observations of surface currents use drifters which are coupled to the surface layer by drogues located at 15 m depth. While drogued observations are useful for studies of circulation of the upper layer of the ocean, a more typical operational problem involves trying to find flotsam that has fallen off the deck of a ship or to predict the path of an abandoned vessel. To better understand the behavior of these surface drifting objects, observations of the surface drifts of RAFOS floats in the California Current system were used to compare the floats’ motions to wind-induced drift and to evaluate the drift prediction by three ocean models: Ocean Surface Current Simulator (OSCURS), Global Navy Coastal Model (gNCOM) and Hybrid Coordinate Ocean Model (HYCOM). Cross-Calibrated Multi-Platform Ocean Surface Wind Vector L3.0 First-Look Analysis wind data were used to analyze the surface drift of the RAFOS floats. The best correlation between float drift speed and wind speed was observed during summer and fall months, when the wind regime over the Northeast Pacific is dominated by the North Pacific High. The predominant winds associated with this regime are steady and contribute to the surface drift in the same direction as the large-scale geostrophic component of the California Current. Evaluation of the drift prediction by three ocean models was conducted by comparing observed drifter trajectories with model-simulated trajectories at 7-day time scales. The model-simulated trajectories were initially collocated with RAFOS positions and restarted every 15 days. The OSCURS model was the only one of three analyzed models which allowed for tuning based on the surface RAFOS trajectories. Two main parameters, Wind Angle Deflection (WAD) and Geostrophic Current Factor (GCF), were adjusted to minimize the separation between observed and modeled trajectories. At shorter time scales, from weeks to several months, the tuned OSCURS model outperformed gNCOM and HYCOM models in reproducing the observed surface drift. For seasonal and longer time scales, both gNCOM and HYCOM can reproduce the seasonal variability, flow direction, and eddy-like structures in the California Current system, which may be useful for long-term forecasts of the Northeast Pacific circulation.

The international programs have been considered within which global oceanographic in-situ measurements are systematically carried out: the Global Drifter Program of tracking of currents in the upper ocean mixed layer as well as measurements of water temperature and atmospheric pressure at the ocean surface along the trajectories of buoys (drifters) which are freely drift with surface ocean currents; the ARGO program of global measurements of vertical profiles of temperature and salinity as well as currents at the given depth of drift by means of network of the diving buoys; the GO-SHIP program of repeated hydrographic measurements along the system of oceanographic sections which is carried out by means of drop probes from the research vessels; the VOS program of ship-based voluntary observations for hydrometeorological parameters and the state of the ocean surface and the overlying atmosphere; the OceanSITES program of long-term observations of various oceanographic parameters at the surface of the ocean and its depths on a global network of moorings and the GLOSS program of monitoring of the global ocean level on the network of coastal stations. The participation of Russian organizations of an oceanographic profile in the listed programs of observations has been described - the observations which form the surface-oceanic subsystem of the Global Ocean Observing System.

Drifting buoys are widely deployed to measure near surface ocean currents and temperature. The Global Ocean Observation System program designed a global array of 1250 drifter buoys to cover oceans at resolution of one per 5° × 5° grids spatially. The National Institute of Ocean Technology, India indigenized drifting buoy in 2012 with geostationary satellite communication to have near real-time data at every hour. The drifting buoy technology is applied for intellectual property right and transferred to Industries. The measurement scheme in the drifting buoys is capable to measure variability in sea surface temperature and small mesoscale surface eddies. This article describes case studies of indigenous drifting buoys in the Indian Ocean from 2012 onwards. The sea surface temperature and drifting speed measured with indigenous drifting buoy is compared with market available drifting buoy (Marlin-Yug), moored data buoy (BD11) and remote sensed data. We also report results from a drifting buoy with General Packet Radio Service (GPRS) telemetry in the coastal region.

This work updates the methods of Lumpkin and Johnson (2013) to obtain an improved near-surface velocity climatology for the global ocean using observations from undrogued and 15-m drogued Global Drifter Program (GDP) drifters. The proposed procedure includes the correction of the slip bias of undrogued drifters, thus recovering about half of the GDP dataset; and a new approach for decomposing Lagrangian data into mean, seasonal and eddy components, which reduces the smoothing of spatial gradients inherent in data binning methods. The sensitivity of the results to method parameters, the method performance relative to other techniques, and the associated estimation errors, are evaluated using statistics calculated for a test dataset consisting of altimeter-derived geostrophic velocities subsampled at the drifter locations, and for the full altimeter-derived geostrophic velocity fields. It is demonstrated that (1) the correction of drifter slip bias produces statistically similar mean velocities for both drogued and undrogued drifter datasets at most latitudes and reduces differences between their variance estimates, (2) the proposed decomposition method produces pseudo-Eulerian mean fields with magnitudes and horizontal scales closer to time-averaged Eulerian observations than other methods, and (3) standard errors calculated for pseudo-Eulerian quantities underestimate the real errors by a factor of almost two. The improved decomposition method and the inclusion of undrogued drifters in the analysis allows resolving details of the time-mean circulation not well defined in the previous version of the climatology, such as the cross-stream structure of western boundary currents, recirculation cells, and zonally-elongated mid-ocean striations.

Since 1994 the U.S. Global Drifter Program (GDP) and its international partners cooperating within the Data Buoy Cooperation Panel (DBCP) of the World Meteorological Organization (WMO) and the United Nations Education, Scientific and Cultural Organization (UNESCO) have been deploying drifters equipped with barometers primarily in the extratropical regions of the world’s oceans in support of operational weather forecasting. To date, the impact of the drifter data isolated from other sources has never been studied. This essay quantifies and discusses the effect and the impact of in situ sea level atmospheric pressure (SLP) data from the global drifter array on numerical weather prediction using observing system experiments and forecast sensitivity observation impact studies. The in situ drifter SLP observations are extremely valuable for anchoring the global surface pressure field and significantly contributing to accurate marine weather forecasts, especially in regions where no other in situ observations are available, for example, the Southern Ocean. Furthermore, the forecast sensitivity observation impact analysis indicates that the SLP drifter data are the most valuable per-observation contributor of the Global Observing System (GOS). All these results give evidence that surface pressure observations of drifting buoys are essential ingredients of the GOS and that their quantity, quality, and distribution should be preserved as much as possible in order to avoid any analysis and forecast degradations. The barometer upgrade program offered by the GDP, under which GDP-funded drifters can be equipped with partner-funded accurate air pressure sensors, is a practical example of how the DBCP collaboration is executed. Interested parties are encouraged to contact the GDP to discuss upgrade opportunities.

We used transition path theory (TPT) to infer "reactive" pathways of floating marine debris trajectories. The TPT analysis was applied on a pollution-aware time-homogeneous Markov chain model constructed from trajectories produced by satellite-tracked undrogued buoys from the NOAA Global Drifter Program. The latter involved coping with the openness of the system in physical space, which further required an adaptation of the standard TPT setting. Directly connecting pollution sources along coastlines with garbage patches of varied strengths, the unveiled reactive pollution routes represent alternative targets for ocean cleanup efforts. Among our specific findings we highlight: constraining a highly probable pollution source for the Great Pacific Garbage Patch; characterizing the weakness of the Indian Ocean gyre as a trap for plastic waste; and unveiling a tendency of the subtropical gyres to export garbage toward the coastlines rather than to other gyres in the event of anomalously intense winds., Comment: Submitted to Chaos

The Oceans cover around 70 percent of entire earth’s surface and contain a volume of 1.3 billion cubic kilometers. According to few analysts roughly 95 percent of the world ocean and 99 percent of ocean floor are yet to be explored. The more interesting fact is that mid-water which is the region between ocean’s surface and sea bottom is least explored. This study is aimed at various sensors, system, and platforms involved in measuring ocean autonomously and providing in situ data in real-time or near real-time. The study encompasses the working and types of such systems which provide atmospheric, physical, and ocean measurements. The systems include, but not limited to, various buoys, drifters, gliders, sailing drones, aerial drones, and ocean observing satellites. These measuring devices, gadgets, and systems are providing data both in the recorded and in-situ form. As an example, the 90% collected data from the Argo buoys is freely available online within 24 hours of its collection. This Core Argo program have covered the ocean globally since 2007 and have collected over 1.6 million temperature/salinity profiles and trajectories. Similar to Core Argo, there are various other global coverage program such as Deep Argo, Biogeochemical (BGC) Argo, Polar Argo, and Global Drifter Program (GDP). Then, this study proceeds with systems providing ocean observations on autonomous scales. These systems comprise of Underwater Gliders, Wave Gliders, Sail Drones, X-spar Buoys, Sonobuoys, and Sensors equipped to live marine mammals. Finally, the study explores the systems involved in aerial observations of the ocean. These aerial observations are being carried out with Global Hawk Drone and multifarious satellites working in collaboration with National Oceanic and Atmospheric Administration (NOAA). These satellites are responsible for providing data of near ocean’s surface salinity, temperature, winds, and ocean color. This study has taken into consideration varying systems and devices involved in exploring global oceans as comprehensive as possible.

Lagrangian drifters are oceanographic devices used to study circulation patterns in the ocean. The devices are typically passive, which means that they have no actuators to initiate motion. They are mainly driven by the ocean currents. A drifter, as depicted in Figure 1, in principle, consists of a surface float and a drogue connected via a tether. The surface float provides the necessary buoyancy to hold the drogue at a certain depth, whereas the drogue (and, thus, the whole drifter) is carried by the currents prevailing at that depth of the ocean. A main focus of oceanographers' and marine biologists' research is the complex dynamics of the ocean, the circulation patterns of water, and the induced movements of effluents, larvae, and other microorganisms [1]. Drifters are used to tag and track the ocean currents and can help to better explain both oceanographic as well as biological phenomena. Our particular interest is the monitoring task of tracking wastewater plumes in the coastal ocean. In this article, we describe the design of low-power, low-cost Lagrangian drifters for ocean monitoring, developed at the Robotic Embedded Systems Laboratory (RESL) at the University of Southern California (USC). We discuss the design challenges and present the overall system characteristics of the RESL drifters. The drifters are augmented by radio communication, which simplifies the task of drifter recovery by a research vessel and enables setting up a bidirectional wireless sensor network between drifters, autonomous underwater vehicles (AUVs), vessels, and base stations.

In the early 70s, 20th century, the tools for studying the World Ocean (besides the already existing research vessels equipped with celestial navigation) were expanded with automatic buoys and remote sensing technologies. The first idea was to create the global observing system on basis of large quantity of surface mooring buoys, equipped with hydrological and meteorological equipment. The evaluation of this suggestion revealed the fact that such tool was too expensive. It was decided to construct a network on the basis of drifting buoys which are significantly cheaper. The article shows the results of scientific and practical efforts to perform a step by step development of the drifter technology, which is the main instrument for global observation in the Ocean now. The cycle of works executed from 1973 to 2016 provided a creation of a world-class drifter technology for solution of different scientific and practical challenges. The research results are actively used for the needs of the Russian Federation and the global drifter program. The prospect of future works is related to the national challenges on the research of the Arctic and other World Ocean regions, participation in national and international projects on calibration of satellite onboard systems for the Earth remote sensing and also to validation of numerical simulation results for refining the marine environment variability forecast.

Calculation results are presented for long-term mean annual surface currents in the North Atlantic based on direct drifter measurements and numerical experiments with the ocean general circulation model using both climatic arrays of hydrological data World Ocean Atlas 2009 and Argo profiling data. The calculations show that the technique suggested for model calculations of oceanographic characteristics of the World Ocean with the use of Argo data significantly improves the climatic fields of the temperature and salinity even on a coarse grid. The comparison of the model calculation results with drifter data showed that the temperature and salinity fields found from Argo data with the use of data variational interpolation on a regular grid allow the calculation of realistic currents and can be successfully used as initial conditions in hydrodynamic models of the ocean dynamics.

With the relatively recent development of Global Drifter Program (GDP) drifters that measure the near-surface ocean velocity and Argo floats that can be used to derive both the intermediate-ocean (1000 m) velocity and the mean dynamic height of the surface relative to 1000 dbar, there now exists the opportunity to directly observe the mean velocity decomposition of the ocean. This study computes the mean Ekman velocity by subtracting the mean referenced velocity derived from Argo data from the mean surface velocity derived from GDP data. This Ekman velocity is slightly stronger than previous observations and shows a spatial structure consistent with a vertical eddy diffusivity that is linearly dependent on wind stress. To do this analysis, the author has to deal with the fact that GDP drifters often lose their drogues, and a product of this research is validation of the wind-slip correction applied to GDP drifters that have lost their drogues.

The Global Ocean Observing System (GOOS) requirements for in situ surface temperature and velocity measurements call for observations at 5° × 5° resolution. A key component of the GOOS that measures these essential climate variables is the global array of surface drifters. In this study, statistical observing system sampling experiments are performed to evaluate how many drifters are required to achieve the GOOS requirements, both with and without the presence of a completed global tropical moored buoy array at 5°S–5°N. The statistics for these simulations are derived from the evolution of the actual global drifter array. It is concluded that drifters should be deployed within the near-equatorial band even though that band is also in principle covered by the tropical moored array, as the benefits of not doing so are marginal. It is also concluded that an optimal design half-life for the drifters is ~450 days, neglecting external sources of death, such as running aground or being picked up. Finally, it is concluded that comparing the drifter array size to the number of static 5° × 5° open-ocean bins is not an ideal performance indicator for system evaluation; a better performance indicator is the fraction of 5° × 5° open-ocean bins sampled, neglecting bins with high drifter death rates.

Combining ocean model data and in-situ Lagrangian data, I show that an array of surface drifting buoys tracked by a Global Navigation Satellite System (GNSS), such as the Global Drifter Program, could provide estimates of global mean sea level (GMSL) and its changes, including linear decadal trends. For a sustained array of 1250 globally distributed buoys with a standardized design, I demonstrate that GMSL decadal linear trend estimates with an uncertainty less than 0.3 mm yr$^{-1}$ could be achieved with GNSS daily random error of 1.6 m or less in the vertical direction. This demonstration assumes that controlled vertical position measurements could be acquired from drifting buoys, which is yet to be demonstrated. Development and implementation of such measurements could ultimately provide an independent and resilient observational system to infer natural and anthropogenic sea level changes, augmenting the on-going tide gauge and satellites records., Comment: resubmitted to AGU Geophysical Research Letters

Starting in the 1970s, surface drifters and subsurface neutrally buoyant floats have been developed, improved, and tracked in large numbers in the ocean. For the first time we have now obtained worldwide maps of the surface and subsurface velocity at a few depths. New profiling floats are measuring and reporting in real time the evolving temperature and salinity structure of the upper 2 km of the ocean in ways that were impossible just a few years ago. These measurements are documenting variations of the world ocean’s temperature and salinity structure. The new data are revealing insights about ocean circulation and its time variability. Surface drifters and subsurface floats measure ocean trajectories that show where water parcels go, how fast they go there, and how vigorously they are mixed by eddies. Ocean trajectories are useful both for visualizing ocean motion and for determining its velocity characteristics. The superposition of numerous trajectories reveals that very different kinds of circulation patterns occur in different regions. Maps of velocity fields can be combined with other measurements such as those of hydrography to give the three-dimensional velocity field of the ocean. Oceanographers are also incorporating the newly acquired data into models of ocean circulation.

High resoultion Eulerian mean velocity field has been derived by combining the satellite tracked surface drifter data with satellite altimetry and ocean surface winds. The drifter data used in this study includes Argos and surface drifter data from Global Drifter Program. Maps of Sea Level Anomaly (MSLA) weekly files with a resolution of (1/3)° in both Latitude and Longitude for the period 1993–2012 have been used. The Ekman current is computed using ocean surface mean wind fields from scatterometers onboard ERS 1/2, Quikscat and ASCAT. The derived mean velocity field exhibits the broad flow of Antarctic Circumpolar Current with speeds up to 0.6 m/s. Anomalous field is quite significant in the western part between 20° and 40°E and in the eastern part between 80°E and 100°E with velocity anomaly up to 0.3 m/s. The estimated mean flow pattern well agrees with the dynamic topography derived from in-situ observations. Also, the derived velocity field is consistent with the in-situ ADCP current measurements. Eddy kinetic energy illustrates an increasing trend during 1993–2008 and is in phase coherence with the Southern Annular Mode by three month lag. Periodic modulations are found in the eddy kinetic energy due the low frequency Antarctic Circumpolar Wave propagation.

Global Drifter Program (GDP) drifter data and Argo float data from 2006 to 2013 are used to provide quantitative description and comparison of the mean near-surface (15 m) and 1000 m velocity fields in the New Zealand region. These fields are estimated both from bin-averaging the drifter/float velocities and by fitting non-divergent streamfunctions to the velocities. At both levels, our velocity fields are broadly consistent with previous drifter/float estimates, but provide more detail on the local structure of the mean fields. North of the Subantarctic Front there are large differences between the surface and 1000 m flows, with the Tasman Front being largely absent at 1000 m. South of the Subantarctic Front, where the flow is expected to be more barotropic, there is a closer correspondence between the flows at both levels. Several previously undocumented eddies in the mean flows at both levels are described.

The purpose of this chapter is twofold. First, we illustrate the technology used by the Lagrangian drifters deployed by Global Drifter Program (GDP), which is the principal component of the Global Drifter Array; second, we review and summarize the most recent studies on the impact of drifter data for calibration and validation of sea surface temperature (SST) satellite products, Numerical Weather Prediction (NWP) and climate studies, tropical cyclones (TCs)-ocean interaction and ocean circulation studies. Several types of drifters are described, starting from the simplest configuration that measures SST and sea-level atmospheric pressure (SLP), continuing with special drifters designed to measure sea surface salinity (SSS) and sea-level wind (SLW), and ending with air-deployable drifting thermistor chains that measure the temperature of the upper 150 m of the ocean, which are used to study the interaction of the ocean’s mixed layer with TCs. We also discuss the implications of the satellite telecommunication technology on the accuracy of drifter’s geolocation and on the timeliness of the near real-time data stream.

From the analysis of oceanic eddies detected in the drifter trajectories of the Global Drifter Program (GDP) data set, it was found that oceanic eddies are asymmetrically distributed across the Kuroshio in the East China Sea: predominant cyclonic (anticyclonic) eddies are on the western (eastern) sides of Kuroshio. This distribution is confirmed by high-resolution numerical modeling output as well. Most of these eddies are 5~20 km in radius, less than the local first baroclinic deformation radius, thus categorized as submesoscale. The generation mechanism of these submesoscale eddies is speculated to be related to the horizontal velocity shear of the Kuroshio when it flows northeastward along the shelf break in the East China Sea. The budget analysis of eddy kinetic energy shows that both the horizontal shear and vertical buoyancy flux are important energy sources for eddy generation on the two sides of Kuroshio axis. The finding highlights the unique feature of oceanic eddies along the western boundary currents.

Coherent-on-Receive X-band marine radar system was developed with the aim to map the nearshore surface current that responsible for sediment transportation in the coastal zone. In order to evaluate the performance of this land-based remote sensing system and to validate the data, in-situ measurement of the surface velocities over the domain that covers from the surf-zone to the inner-shelf are required. In present study, low-cost GPS tracking drifters were developed. The synchronize deployment of the drifter clusters can be carried out to obtain the large data set as the sea truth data for comparative study. The drifter, field campaigns and the results are described.

The database (formed in MHI) for 22 drifters deployed in the Arctic region in 2012 – 2016 is represented. The most intensive drifter observations were performed in the Beaufort Sea (the Canada Basin) and in the Central Arctic. According to the data of temperature-profiling drifters, ∼ 2 million temperature profiles (including the ones acquired under the ice formations) and ∼ 120.000 atmospheric pressure measurements were obtained. Total life time of drifters as at August 2016 exceeded 7000 days. General information and technical characteristics of BTC60/GPS/ice/1ps, BTC60/GPS/ice/3ps, SVP-BTC80/GPS temperature-profiling drifters are given. Features of drifter information primary preparation are enumerated and the technique of database quality assessment is shown. The studies have shown that temperature-profiling data provides the assessment of the ice thickness and its spatial-temporal variability in the region. The results of the experiments carried out in the Arctic reveal the fact that autonomous temperature-profiling “ice” drifters are an effective instrument for studying the Arctic region. According to the results of the experiments carried out in the Arctic and verification of data quality in the formed database, the drifters showed the reliability of operational characteristics. This is confirmed by failure-free operation of IMEI 245950/WMO 48541 drifter which had been performed the measurements during 1.083 days. The obtained unique long-term series of systematic operational data can be applied for clarifying the concepts of thermal processes variability in the upper ocean layer (including the under-ice one), the dynamics of ice fields and air pressure fields in a wide range of spatial-temporal scales as well as for refining the concept of interaction processes in the Atmosphere – Ice – Ocean system.

We present an evaluation of a 19-year numerical hindcast, Bluelink ReANalysis 3.5 (BRAN 3.5), derived from the Australian Bluelink programme. The evaluation is made for the surface and at 1000 m depth using Global Drifter Program (GDP) drifters and Argo floats, respectively. It is aimed at comparing the model’s ability to correctly simulate the Lagrangian mixing processes. These mixing and dispersal processes are often parameterised in terms of an eddy diffusivity, and we use diffusivity as a metric of comparison. Because the data are spatially sparse and non-uniform in time, the hindcast was sampled at the data locations to provide a model velocity corresponding to each observed velocity. Pseudo-Eulerian mean velocity and eddy kinetic energy fields were computed from bin-averaging of the Lagrangian velocities, and eddy diffusivities were computed from single-particle statistics. The mean field at 2.5 m in BRAN is largely dominated by Ekman transport. The mean velocities at 12.5 m compare well with the GDP drifter mean velocities, except that the Antarctic Circumpolar Current (ACC) is stronger in GDP than in BRAN. At the surface, EKE in BRAN tends to be marginally higher than in GDP. Modelled eddy diffusivity compares well with observed diffusivity, except in the boundary currents and near the equator. At 1000 m, BRAN tends to overestimate the mean field, EKE and eddy diffusivity at low latitudes and underestimate them at higher latitudes.

Employing some 40 years of North Pacific drifter-track observations from the Global Drifter Program database, statistics defining the horizontal spread of radionuclides from Fukushima nuclear power plant into the Pacific Ocean are investigated over a time scale of 5 years. A novel two-iteration method is employed to make the best use of the available drifter data. Drifter-based predictions of the temporal progression of the leading edge of the radionuclide distribution are compared to observed radionuclide concentrations from research surveys occupied in 2012 and 2013. Good agreement between the drifter-based predictions and the observations is found.

Operational meteorologists and Oceanographers rely on real-time environmental data to run their numerical prediction models, even carry on the research. The ground station network is dense and the data of good quality, but there is not enough environmental data from the oceans, particularly in data-sparse areas not covered by commercial ships reporting environmental data. A drifting ocean buoy is described. The drifter consists of three main components: a surface float, a tether assembly and a dimensionally-stable drogue. It utilizes a drag structure which follows the water mass of the ocean as it flows in the form of the ocean current, and which also has an aerodynamically shaped low wind drag mast to minimize wind induced errors in ocean current drift measurements; the drag structure also being stable and resistant to heaving (pitch and roll) so as to maintain a mast carried antenna above the water even at high sea states.

The Global Drifter Program data set is applied to develop 2° × 2° bin estimates of the lateral eddy diffusivity K in the Indian Ocean (IO) by means of a modification of the Davis approach. The calculations were performed relative to the seasonal change in the mean currents, which is especially important in the case of monsoon-driven circulation in the IO. Estimates of K were found to be below 1 × 104 m2/s almost every-where in the IO. The spatial variations of K were analyzed in relation to the instabilities of the ocean circulation.

The shedding sequence of the Loop Current (LC) inside the Gulf of Mexico (GoM) is strongly influenced by cyclonic frontal eddies around its edge. Along-track altimetry data, analyzed based on a wavelet decomposition to provide estimates of individual cyclones’ diameter, amplitude and relative vorticity, and in situ surface drifter data from the Global Drifter Program, are used to investigate the cyclonic activity in the eastern Gulf of Mexico, where the LC extends and retracts. By analyzing this ∼20 year long (1992–2011) combined set of observation data records, we were able to complement previous findings, to confirm results from modeling studies and to provide new insights on the LC frontal dynamics. Drifter data indicate, for the first time, that Loop Current Frontal Eddies (LCFEs) are in solid-body rotation close to their core. This property makes relative vorticity the most robust diagnostic from along-track altimetry for characterizing LCFEs in the eastern GoM, based on consistent comparisons with drifter data. Both data sets are complementary for describing the LCFEs’ regional variability. LCFEs observed in the deep southeastern GoM show intense relative vorticity, but they are not frequently observed. The study of an unprecedented, long drifter trajectory suggests that they are not intensified locally. This implies that, among LCFEs coming from the northern GoM, only intense ones reach the deep southeastern GoM. The observation datasets provide, for the first time, quantitative evidences of processes so far only identified with models: LCFEs are intensified when they are advected over the Mississippi Fan in the northern GoM; a small area north of Campeche Bank shows intense LCFE activity. The altimetry and drifter data confirm and complement results from more limited datasets: LCFEs forming the Tortugas Eddies, at the entrance of the Straits of Florida, are the most intensely observed LCFEs in altimetry. Coming from the GoM interior, they can be modified, in size and intensity, just before or during their stay in the Dry Tortugas area, whereas they were long considered to be modified only after they were advected in the Straits of Florida. A single drifter trajectory illustrates in detail the erosion of a LCFE in the southeastern GoM, presumably under the influence of the LC, which leads to the re-arrangement of vorticity and the formation of a distinct LCFE, just upstream the Dry Tortugas area. The study also confirms that LCFEs have diameters of 80–120 km, generally larger east and north of the LC. They tend to stay for long periods in the northeastern GoM, and thus may undergo vortex merging with incoming eddies, as previously noted on individual episodes. Altimetry reveals that the largest LCFEs reside in the central eastern GoM, in a location where they are known to block the LC extension; however, our long altimetry dataset shows that these large eddies are not always involved in such LC blocking. Finally, this study led to improvements in data treatment, for both along-track altimetry and drifter trajectories. The wavelet approach used to derive eddy characteristics from along-track altimetry allows robust estimates of the eddy relative vorticity. The drifter dataset has been extended to include data from drifters even after they lost their drogue; the latter data treatment can be applied in areas of moderate winds.

The Global Drifter Program data set, collected in the period 1979–2011, is divided in drogue-on and drogue-off subsets which are then used to develop 5°×5° bin estimates of lateral eddy diffusivity in the World Ocean's mixed and surface layers, respectively, by means of a modification of the Davis (1987. Journal of Marine Research, 430 (45), 635–666.; 1991. Deep Sea Research. 38, 432 (1), S531–S571.) approach. The analysis is geographically focused on the Indian Ocean, the region where such calculations have been lacking. As the Indian Ocean circulation is strongly determined by monsoonal winds, an effort was made to calculate the diffusivity relative to monsoon-driven mean currents. The drifter-derived estimates of the asymptotic lateral diffusivity at large time lags K ∞ , were found to be below 1×104 m2 s−1 almost everywhere in the World Ocean, while the maximum diffusivity K max , equivalent to integrating the Lagrangian velocity autocorrelation to the first zero crossing, exceeds K ∞ in strong ocean currents by a factor of 2–4. At mid latitudes (20° ≤ | ϕ | ≤ 50°), the estimates of K ∞ in the mixed and surface layers are shown to follow the frozen field regime parameterisation K ∞ ~ E K E × L b c , where E K E is the eddy kinetic energy and L b c is the baroclinic Rossby deformation radius. In contrast, at low latitudes ( | ϕ | 29°) in the surface layer, the fixed float regime parameterisation K max , K ∞ = E K E × T 0 , where T 0 = 1.9 days and 1.3 days is the typical value of the Lagrangian integral timescale in the cases of K max and K ∞ , respectively, is preferable.

In the present study, an attempt has been made to estimate sea surface salinity (SSS) by blending in situ observations from the National Oceanic and Atmospheric Administration/Pacific Marine Environmental Laboratory—Research Moored Array for African–Asian–Australian Monsoon Analysis and Prediction buoy with satellite data from the Soil Moisture and Salinity Mission using objective analysis approach. A preliminary analysis is done in the tropical Indian Ocean at monthly time scale for the year 2010 at 0.25°latitude ×0.25°longitude resolution. Comparison with other independent in situ SSS observations suggests that the analyzed SSS takes the advantage of high spatial coverage by the satellite and accurate measurements from the buoy data and has potential for better SSS estimation.

[1] This study investigates how the quality of sea surface temperature (SST) observations made by drifting buoys (drifters) and ships for 1996–2010 can be improved through retrospective quality control (QC) against a reference field. The observations used are a blend of delayed mode data taken from the International Comprehensive Ocean-Atmosphere Data Set (versions 2.0 and 2.5) and real time data obtained from the Global Telecommunication System. A comparison of drifter and ship measurements on a platform-by-platform basis to high-quality SST estimates from the Along track scanning radiometer Reprocessing for Climate (ARC) project reveals drifter observations are generally of good quality but frequently suffer from gross errors, whilst ship observations are generally of worse quality and show a diverse range of measurement errors. QC procedures are developed which similarly assess drifter and ship SST observations through comparison with the Met Office Operational SST and Sea Ice Analysis (OSTIA). These procedures make use of seasonal background error variance estimates now available for OSTIA. Drifter observations displaying some commonly observed gross errors are flagged and ship callsigns whose observations are deemed unreliable are blacklisted. Validation of the QC outcomes against ARC and Argo demonstrates that this retrospective QC improves the quality of drifter and ship observations, though some limitations are discussed.

Satellite-tracked drifting buoys of the Global Drifter Program have drogues, centered at 15-m depth, to minimize direct wind forcing and Stokes drift. Drogue presence has historically been determined from submergence or tether strain records. However, recent studies have revealed that a significant fraction of drifters believed to be drogued have actually lost their drogues, a problem that peaked in the mid-2000s before the majority of drifters in the global array switched from submergence to tether strain sensors. In this study, a methodology is applied to the data to automatically reanalyze drogue presence based on anomalous downwind ageostrophic motion. Results indicate that the downwind slip of undrogued drifters is approximately 50% higher than previously believed. The reanalyzed results no longer exhibit the dramatic and spurious interannual variations seen in the original data. These results, along with information from submergence/tether strain and transmission frequency variations, are now being used to conduct a systematic manual reevaluation of drogue presence for each drifter in the post-1992 dataset. Satellite-tracked drifting buoys (hereafter ‘‘drifters’’) of the Global Drifter Program (GDP) have been collecting near-surface ocean current observations in the tropical Pacific since 1979, with observations in the other basins also now spanning more than 15 years. The GDP is a branch of the National Oceanic and Atmospheric Administration’s (NOAA) Global Ocean Observing System and a scientific project of the Data Buoy Cooperation Panel, and is funded by NOAA’s Climate Program Office. Its objectives are to maintain a global array of ;1250 drifters and to provide a data processing system for scientific use of the resulting observations, which support short-term (seasonal to interannual) climate predictions, climate research, and climate monitoring. A subset of the driftersalso includes barometers for improved numerical weather forecasting efforts. The GDP works with a large number of national and international partners

In this chapter, a general overview and characterization of ocean current resources for potential power generation in the global oceans are presented. They are based on analysis of two relatively long data sets of surface drifter-observed mixed-layer current and the satellite altimeter-derived surface geostrophic current. Spatial and temporal variations of the four most prominent western boundary currents—the Kuroshio, Mindanao, Gulf Stream, and Agulhas currents—and their available mean undisturbed ocean power densities are discussed. Several potential sites for ocean current power generation in the North Pacific , South China Sea, and Oceania are identified based on a criterion formulated by combining the frequency with which the ocean currents occur, the magnitudes of their speed, the water depths at which they occur, and their distances from the shore.

[1] Recent geoids from the Gravity Recovery and Climate Experiment (GRACE) and the Gravity field and steady state Ocean Circulation Explorer satellite mission (GOCE) contain useful short-scale information for the construction of a geodetic ocean mean dynamic topography (MDT). The geodetic MDT is obtained from subtracting the geoid from a mean sea surface (MSS) as measured by satellite altimetry. A gainful use of the MDT and an adequate assessment needs an optimal filtering. This is accomplished here by defining a cutoff length scale dmax for the geoid and applying a Gaussian filter with half-width radius r on the MDT. A series of MDTs (GRACE, GOCE, and combined satellite-only (GOCO) solutions) is tested, using different sets of filter parameters dmax and r. Optimal global and regional dependent filter parameters are estimated. To find optimal parameters and to assess the resulting MDTs, the geostrophic surface currents induced by the filtered geodetic MDT are compared to corrected near-surface currents obtained from the Global Drifter Program (GDP). The global optimal cutoff degree and order (d/o) dmax (half-width radius r of the spatial Gaussian filter) is 160 (1.1°) for GRACE; 180 (1.1–1.2°) for 1st releases of GOCE (time- and space-wise methods) and GOCO models; and 210 (1.0 degree) for 2nd and 3rd releases of GOCE and GOCO models. The cutoff d/o is generally larger (smaller) and the filter length smaller (larger) for regions with strong, small-scale (slow, broad scale) currents. The smallest deviations from the drifter data are obtained with the GOCO03s geoid model, although deviations of other models are only slightly higher.

Drifting buoys are widely deployed to measure near surface ocean currents and temperature. The Global Ocean Observation System program designed a global array of 1250 drifter buoys to cover oceans at resolution of one per 5 ° × 5 ° grids spatially. The National Institute of Ocean Technology, India indigenized drifting buoy in 2012 with geostationary satellite communication to have near real-time data at every hour. The drifting buoy technology is applied for intellectual property right and transferred to Industries. The measurement scheme in the drifting buoys is capable to measure fluctuations in sea surface temperature and smaller surface eddies. This article describes case studies of indigenous drifting buoys in the Indian Ocean from 2012 onwards. The sea surface temperature and drifting speed measured with indigenous drifting buoy is compared with market available drifting buoy (Marlin-Yug), moored data buoy (BD11) and remote sensed data. We also report results from a drifting buoy with General Packet Radio Service (GPRS) telemetry in the coastal region.

Surface drifting buoys, or drifters, are used in oceanographic and climate research, oil spill tracking, weather forecasting, search and rescue operations, calibration and validation of velocities from high-frequency radar and from altimeters, iceberg tracking, and support of offshore drilling operations. In this review, we present a brief history of drifters, from the message in a bottle to the latest satellite-tracked, multisensor drifters. We discuss the different types of drifters currently used for research and operations as well as drifter designs in development. We conclude with a discussion of the various properties that can be observed with drifters, with heavy emphasis on a critical process that cannot adequately be observed by any other instrument: dispersion in the upper ocean, driven by turbulence at scales from waves through the submesoscale to the large-scale geostrophic eddies.

In this study, we investigated the accuracies of SSS in the northwest Pacific Ocean for the recent three years (2012–2014) by comparison with in situ salinity measurements from Argo floats, moored buoys, and many of ship CTD measurements. The satellite SSS errors of the northwest Pacific Ocean presented characteristic dependence on latitudes close to the global ocean but were mostly underestimated at all ranges of SST and wind speed.

The surface drifting buoys, or drifters, of the Global Drifter Program (GDP) are predominantly tracked by the Argos positioning system, providing drifter locations with O(100 m) errors at nonuniform temporal intervals, with an average interval of 1.2 h since January 2005. This data set is thus a rich and global source of information on high-frequency and small-scale oceanic processes, yet is still relatively understudied because of the challenges associated with its large size and sampling characteristics. A methodology is described to produce a new high-resolution global data set since 2005, consisting of drifter locations and velocities estimated at hourly intervals, along with their respective errors. Locations and velocities are obtained by modeling locally in time trajectories as a first-order polynomial with coefficients obtained by maximizing a likelihood function. This function is derived by modeling the Argos location errors with t location-scale probability distribution functions. The methodology is motivated by analyzing 82 drifters tracked contemporaneously by Argos and by the Global Positioning System, where the latter is assumed to provide true locations. A global spectral analysis of the velocity variance from the new data set reveals a sharply defined ridge of energy closely following the inertial frequency as a function of latitude, distinct energy peaks near diurnal and semidiurnal frequencies, as well as higher-frequency peaks located near tidal harmonics as well as near replicates of the inertial frequency. Compared to the spectra that can be obtained using the standard 6-hourly GDP product, the new data set contains up to 100% more spectral energy at some latitudes.

García Sotillo, Marcos ... et al.-- 9 pages, 5 figures, 2 tables, On 9 September 2014, an intensive drifter deployment was carried out in the Strait of Gibraltar. In the frame of the MEDESS-4MS Project (EU MED Program), the MEDESS-GIB experiment consisted of the deployment of 35 satellite tracked drifters, mostly of CODE-type, equipped with temperature sensor sampling at a rate of 30 min. Drifters were distributed along and on both sides of the Strait of Gibraltar. The MEDESS-GIB deployment plan was designed as to ensure quasi-synoptic spatial coverage. To this end, four boats covering an area of about 680NM2 in 6 h were coordinated. As far as these authors know, this experiment is the most important exercise in the area in terms of number of drifters released. Collected satellite-tracked data along drifter trajectories have been quality controlled and processed to build the presented MEDESS-GIB database. This paper reports the MEDESS-GIB data set that comprises drifter trajectories, derived surface currents and in situ SST measurements collected along the buoys tracks. This series of data is available through the PANGAEA (Data Publisher for Earth and Environmental Science) repository, with the following doi:10.1594/PANGAEA.853701. Likewise, the MEDESS-GIB data will be incorporated as part of the Copernicus Marine historical products. The MEDESS-GIB data set provides a complete Lagrangian view of the surface inflow of Atlantic waters through the Strait of Gibraltar and thus, very useful data for further studies on the surface circulation patterns in the Alboran Sea, and their links with one of the most energetic Mediterranean Sea flows: the Algerian Current, The MEDESS-GIB experiment was performed as part of the MEDESS-4MS Project activities (Project ref. 2S-MED11-01), supported by the European Regional Development Fund in the framework of the MED Programme. D. Conti is currently a PhD fellowship (FPI/1543/2013) granted by the Conselleria d’Educació, Cultura i Universitats from the Government of the Balearic Islands co-financed by the European Social Fund. J. M. Sayol is thankful for the financial support of CSIC and FSE with the JAE-pre PhD scholarship program

The water-following capabilities of surface drifting buoy are investigated through analyzing the hydrodynamic factors which influence the buoy’s floating, so as to improve the precision of ocean currents measured by drifters, and optimize the design of drifters. The force balance equation of surface drifting buoy is established, and the wind coefficient of drifter model is obtained and analyzed. A prototype based on GPS (Global Positioning System) and BeiDou-1 (BeiDou Satellite Navigation Experimental System) is designed to collect surface currents near Gulf of Jiaozhou. Calculated results indicate that the velocity data, which take the wind coefficient into account, are more approaching the measuring value of fixed current-meter. That provides some experimental validities to the modelling and designing of surface drifting buoy. This study also shows that the surface trajectory from GPS and BeiDou-1 float provides a new means to measure surface circulations in the global ocean at real time, and that the estimated currents could be one of the important sources to improve our understanding for ocean dynamics characteristics.

not less than 1250 buoys regularly distributed over the World Ocean have been drifting simultaneously. Data of observations are transferred via satellite communication systems to the acquisition coastal centers. Every day from drifters there come data ows which should be archived, processed, visualized, analyzed and conclusions need to be done. The present article is devoted to the description of the computer system of storage, processing and visualization of drifter data { the system which has been functioning already for more than 10 years at the State Oceanographic Institute of the Russian Federal Hydrometeorology and Environmental Monitoring Service. In the interactive mode the system gives the data of observations, including averaged grid sets, as well as the various graphical and statistical information on the measured currents and temperature in a surface layer of any given area of the World Ocean. KEYWORDS: Information system; database; data processing; visualization; drifter observations; surface currents; World Ocean. Citation: Nikitin, O. P. (2012), Storage, processing and visualization data system of drifter observations of surface currents in the World Ocean, Russ. J. Earth. Sci., 12, ES5002, doi:10.2205/2012ES000521.