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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.

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.

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.

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.

We propose a method for controlling multiple active drifters in the presence of external forcing induced by the ocean. Our active drifters have one actuator: they can lower and raise their drogues in depth. By exploiting the vertically stratified nature of ocean currents, we show how classical multi-robot tasks (spreading out and aggregation) can be accomplished by the multi-drifter system. Tests with a realistic simulation based on an ocean model suggest that a practical implementation of active drifters which aggregate and disperse in the coastal ocean could be realized through our control method with relatively inexpensive components. Specifically, we are able to show that over a 90 day deployment a significant fraction of drifters can be made to aggregate in few clusters suitable for recovery.

This paper considers a team of spatially distributed drifters that move underwater under the influence of an ocean internal wave. The team's objective is to estimate the physical parameters that determine the internal wave, use the then-known ocean dynamics to rendezvous underwater, and finally return to the surface as a cluster for easy retrieval. From the structure of the internal wave, the ocean's flowfield is time-varying and spatially dependent on depth and position along the wave propagation direction. The drifters can control their depth by changing their buoyancy and are otherwise subject to the horizontal flowfield at their given depth. We consider two different drifter dynamical models: a first-order Lagrangian model, useful when the drifter's mass is sufficiently small, and a second-order model, where the drag force caused by the water accelerates the drifter. We propose provably correct distributed algorithms that rely on the drifters opportunistically changing their depth so that the ocean flowfield takes them in a desirable direction to perform coordinated motion. The drifters converge to the same depth and position along the wave propagation direction asymptotically. Simulations illustrate our results.

Based on the statistics of all surface drifting buoys of 1979-2011, the transport paths and times of Fukushima nuclear pollutants in the North Pacific surface have been studied. We examined the trajectories of surface drifting buoys that passed by the pre-defined source region of nuclear pollutants (totally 176 buoys) one by one to identify typical buoy trajectories in the North Pacific surface. Results show that there are three types of drifting trajectories for these 176 buoys. 80% (141) of 176 surface drifting buoys moved eastward along with Kuroshio and Kuroshio-extension currents, and only 20% moved southward. However, among 141 buoys that traveled along with the Kuroshio and Kuroshio-extension currents, only 13 finally reached the easternmost area of the North Pacific. Among the 35 buoys southward, only 5 turned their directions westward and entered the South China Sea through the Luzon Strait. Among the 5 buoys reaching the east coast of China, 1 buoy was found to travel with the Subtropical circulation branch at the central Pacific and formed its relatively longer trajectory and other 4 were brought into the South China Sea by local eddy-associated circulations.

Ocean drifters are floating platforms equipped with sensors and satellite communication technology that can transmit data on a nearly continuous basis. We use student-built ocean drifters as the focal point for incorporating ocean technology, real-time data collection, data sharing and data visualizations into curriculum. Using Google Earth we are able to visualize ocean processes by overlaying the drifter tracks with multiple layers of oceanographic time series data. A teaching moment emerges as students watch the path of their drifter; they want to learn about both the forces that cause currents and the currents' relationship to other ocean parameters such as sea surface temperature. Google Earth time animations have become an important tool in teaching these types of interconnections between Earth processes because they show what traditional still images cannot: spatial and temporal relationships between parameters simultaneously.

We study the possibility of using ocean surface drifting buoys (“drifters”) as a low-cost alternative to assess the potential of a tidal channel to deliver useful renewable energy. Instead of using Acoustic Doppler Current Profilers (ADCP) for underwater ocean current measurement, we propose the use of drifters released on localized areas of interest which is more affordable and flexible for use of coastal communities in the Philippines. We discuss the drifters used in our experiments and show our methodology with field results obtained from an actual drifter deployment on April 2010 in the Mactan-Olango Channel of Cebu, and in Ligpo island, Anilao, Batangas, Philippines. Since power extraction devices and systems used for tidal currents primarily take into account flow speed in the channel, we present flow speed data derived from the Mactan-Olango and Ligpo drifter deployments. We also discuss how this effort can be refined and replicated to yield site assessment guidelines including power prediction estimation using drifter data.

A family of lightweight (less than 15 kg), long-life (up to 3–4 months) and low-cost drifters are developed in the Tallinn University of Technology and local engineering companies. Such buoys have a rugged and simple housing construction with the diameter of 11 cm and length of 1 m. The buoys are equipped with GPRS based two-way communication and they are programmable during the mission. The data are transferred in real time into one or several FTPs for the operational use in circulation and ice models for data assimilation and/or model validations. The buoys are used also for the estimation of oil drift and ice dynamics properties, e.g. ice drift, compacting, ridging, etc. Real-time (on-line) data transfer is performed via the GPRS protocol with a typical time interval of 15 minutes, but it can be programmed otherwise. The data received in FTP are ready to be used for model assimilation and in different operational applications and services like the drift of surface objects, ice and oil drift. It is possible to view the buoy data in real time via a special web solution. Two major measurement campaigns have been performed using light drifters. Firstly, the validation of High Resolution Operational Model for the Baltic Sea (HIROMB) surface currents in Estonian coastal waters in 2007 and secondly, the study of dynamic ice drift. In both cases the light on-line drifters showed good performance and stability for long-life operation. The percentage of fault positioning was higher in water, reaching up to 20%, and was mainly caused by the reflections of GPS signal from the waves, since a very small part of the buoy remains above the sea surface. In ice the fault positioning was lower, less than 10%. In the case of an ice covered sea, the buoys were from time to time pushed under ice for some period during which the positioning systems failed to transfer the signal. In 2007 during the period from August till November 17 experiments were carried out with surface drifters released in small coastal bays and the open sea of the Gulf of Finland. The longest period when a buoy was drifting lasted for 8 days. It moved across the Gulf of Finland covering a little less than 50 miles. In accordance with the drifter experiments the drifter trajectories that imitate oil spill drift were calculated from HIROMB currents and wind. The calculations were carried out with a different wind factor between 0–3%. The results of modeling showed close agreement with drifter data in some cases, but no unique wind factor suitable for the Gulf of Finland could be identified. In March-April 2010, an extensive ice drifter experiment was conducted in the eastern part of the Gulf of Finland. The development of light on-line GPS drifters continues. The platform of data logging and transfer allows adding a number of parameters to be measured by the drifter and transmitted on-line. To begin with, water temperature and salinity sensors will be added.

Ocean surface winds play a significant role in the global ocean-atmosphere system. Surface winds drive the worlds ocean currents, transport atmospheric heat and moisture, force nutrient rich upwelling areas, create surface waves and swell, and can reach destructive force in both extratropical and tropical cyclones. Although the oceans cover 70% of the Earth's surface, the network of ocean wind observations obtained from conventional buoys and ships is very sparse. The measurement of ocean surface winds using remote sensing technologies is the only means of obtaining wind information over large portions of the global ocean in a timely manner. The Ocean Surface Vector Winds Team (OSVWT) of the Satellite Oceanography and Climatology Division (SOCD) within the NOAA/NESDIS/Center for Satellite Applications and Research (StAR) has been producing satellite-derived ocean surface wind data since the mid 1990s. Wind products from several remotely sensed sources such as QuikSCAT and WindSat are available in near real time (NRT) on the Internet and are also distributed within NOAA. These wind products are used by operational forecasters, scientific researchers and the marine community. The researchers and forecasters from NOAA Ocean Prediction Center (OPC), the NESDIS StAR Ocean Winds Team and the University Corporation for Atmospheric Research (UCAR) have partnered to increase awareness of the various ocean surface wind vector products available and to develop the educational materials needed to expose these products and to educate teachers at various levels about the latest technology for measuring and interpreting remotely sensed ocean vector winds. To accomplish this it has been proposed to host an educator workshop OPC. This workshop would target educators that train professional and future mariners in meteorology, oceanography and storm avoidance. Teachers from state maritime colleges, federal academies, and professional training institutions would be among those invited to participate. This workshop would be hosted by both researchers and forecasters and held within an operational forecast environment to promote hands-on experience. This paper will provide background information on current and new ocean surface wind remote sensing technologies, give examples of how products are used within the operational environment, and discuss the development of training material

Future observations of the global ocean will move beyond measurements of the ocean surface topography, winds, roughness, sea surface temperature, and surface salinity to include in situ and remotely sensed measurements of the deep ocean. These important measurements will quantify the deep ocean circulation and its implication for the oceanic transport of heat, and the relationships between ocean circulation variability and the climate change. New measurement technologies will include remote sensing measurements of ocean mass through global gravity observations, innovative measurement of oceanic vertical structure with satellite relayed data from in-situ profiling floats, and remote measurement of the ocean surface boundary layer at higher temporal resolution.

We deployed ninety-seven oil-spill-simulating drifters over the continental shelf of the northeastern Gulf of Mexico during five hydrographic surveys conducted from 1997 through 1999. Earlier, side-by-side comparisons with spilled crude petroleum on the ocean surface had demonstrated that these drifters moved on the ocean surface like consolidated oil slicks under light to moderate winds. (Under high winds, a surface oil spill tends to be entrained into the mixed layer and Ekman transported, unlike the drifters, which remain on the sea surface and move mostly downwind.) The drifters were then deployed in the Gulf of Mexico as nonpolluting oil-spill proxies to compare their movements against results from an oil-spill trajectory model. The drifter trajectories were compared statistically to trajectories generated by the Oil-Spill Risk Analysis (OSRA) model. The model uses a variation of the 3.5-percent rule to compute the drift due to local wind forcing and superposes the prevailing ocean current on this wind-induced drift to obtain the total velocity of an oil spill on the ocean surface. The input fields are the European Center for Medium Range Weather Forecasts (ECMWF) winds and a data-assimilating hindcast of the ocean currents over the time the drifters were deployed. Scatter plots and linear regressions of the speeds and directions of simulated vs. modeled oil-spill drift show the extent to which they are different. Underlying these differences are the expected differences between the ocean current input field and the trajectories of satellite-tracked, "water-following" drifters deployed simultaneously with the oil-spill-simulating drifters. An earlier evaluation of the ECMWF winds showed better, but of course not perfect, agreement with meteorological buoys in the Gulf. The integrated effect of the errors in the input fields results in average discrepancies between the terminal ends of the simulated and modeled spill trajectories of 78, 229, 416, and 483 km after 3,10, 20, and 30 days of drift, respectively. These results are the consequence of integrating wind and ocean current fields, which are not perfect, and comparing the resultant trajectories against those of the oil-spill-simulating drifters, which themselves contain location errors and which are not considered to be perfect simulators of real oil spills. However, the results are useful to practical oils spill risk analysis through ongoing improvement of the model.

For over twenty years researchers have used satellite tracked buoys to study oceanic currents. This ever growing data base offers an exceptional opportunity to improve the mean current data bases used for a wide range of purposes, from oil spill contingency planning to predicting the movement of search objects. The origin of currents now used is a patchwork of ship-drift and hydrographic data of widely varying reliability and spatial resolution. Of course the drifter data set comes with its own list of problems, the most serious of which are: the large variation in drifter and drogue design, differing drogue depths and, indeed, whether or not there is a drogue attached. Although there is some variability in the quality of the buoy position data, most researches use ARGOS tracking services, so the accuracy of the positions is reasonably well known, a distinct advantage over the bulk of the ship drift data. This paper describes the first steps of International Ice Patrol's (IIP) efforts to use drifter data to develop a new gridded data base for its iceberg drift model. In 1995 IIP set out to obtain all available drifting buoy data in the western North Atlantic, its area of operations, and blend these data into a single representation of the near surface currents in the region. Ice Patrol acquired data from the two major archival centers, the National Oceanographic Data Center (NODC) and Canada's Marine Environmental Data Service (MEDS). In addition, IIP obtained data from several principal investigators whose buoy tracks were not yet in the archives. The resulting drifter data set contains 243 trajectories for a total of 30,308 buoy-days, over half of which were from IIP's own drifter program. Daily averaged current vectors were calculated from the interpolated drifter tracks. These vectors were then resolved into their u and v components, which were placed in 1 degree of latitude by 1 degree of longitude bins over the area 37-61 N and 35-60 W. For each bin the mean and variance were calculated. Although some areas, notably the offshore branch of the Labrador Current, are well resolved there are vast areas where there are relatively few observations.

The authors have recently undertaken a program of measurements and numerical modeling of the strong currents in Juan de Fuca Strait. Previous current measurement programs have under-sampled the near surface region (0 to 15 m) because of the vulnerability of conventional moored instrument arrays in this commercially active water way and because instrumental limitations preclude reliable measurements near the surface. Satellite tracked surface drifters, like those developed for the World Ocean Circulation Experiment (WOCE), have been used in great numbers to observe the surface currents in the open ocean. However, the accuracy and frequency of the position fixes provided by satellite-based location system (Argos) are insufficient to resolve the short space and time scale of the flow in the coastal zone. The Global Positioning System (GPS) has improved both the frequency and accuracy of drifter positioning, and its wide spread use has made it feasible to incorporate this technology into the field proven WOCE surface drifter. In the last two years, the authors have modified, tested and successfully used WOCE-GPS drifters from three different manufactures. An indispensable component of their drifter program is a ship-based, real-time tracking system. The tracking system comprises a commercially available uplink receiver to acquire the direct data transmissions from the drifters, together with a software program which we developed in-house to process the data messages so that they may monitor the drifter positions and their onboard sensor data in real-time. With the use of the real-time tracking they are able to recover and re-seed the drifters when they leave the experimental area or run aground, and they have been able to adjust their sampling strategy based on the observed surface circulation patterns.

The Tropical Ocean Global Atmosphere (TOGA) Program was started in January of 1985 as part of the World Climate Research Project (WCRP).It is designed to improve our understanding of events in the tropical oceans and global atmosphere that significantly influence predictability of seasonal to interannual climatic variations. To support TOGA, the National Data Buoy Center (NDBC) was assigned the responsibility of procuring, deploying, and maintaining a grid pattern of 50 drifting buoys throughout the oceans of the Southern Hemisphere. From October I984 through June 1985, NDBC deployed 64 buoys in the southern oceans. This paper describes the buoys, addresses the extensive logistics program necessary for worldwide deployment, and evaluates buoy performance.