NOAA National Data Buoy Center

On the basis of 30 samples from near-simultaneous overwater measurements by pairs of anemometers located at different heights in the Gulf of Mexico and off the Chesapeake Bay, Virginia, the mean and standard deviation for the exponent of the power-law wind profile over the ocean under near-neutral atmospheric stability conditions were determined to be 0.11 ± 0.03. Because this mean value is obtained from both deep and shallow water environments, it is recommended for use at sea to adjust the wind speed measurements at different heights to the standard height of 10 m above the mean sea surface. An example to apply this P value to estimate the momentum flux or wind stress is provided.

Several field intercomparisons of buoy winds were conducted to investigate the quality of the observations. Differences between dual anemometers on the same buoy were calculated during tropical cyclones. The speed and direction differences did not grow appreciably with increasing wind speed, and at no time was the speed difference greater than 1 m s−1. Differences between winds measured at colocated buoys and a buoy moored near a platform were investigated. Standard deviations of speed differences were less than 1 m s−1 and direction differences were less than 11°. The differences were slightly larger in certain sea stares in the interbuoy comparison. No similar evidence was found when buoy winds were compared to platform winds. Several comparisons were conducted to help quantify errors that arise when buoy winds are used as comparison data for satellite-based scatterometer and altimeter winds. First, 8.5 min average winds were compared to hourly average winds to investigate effects introduced by the buoy's short averaging period. Second, speed and direction differences between pairs of buoys located 39 and 109 km apart were calculated to determine differences due to spatial variation in the wind field. Differences due to spatial variations were larger than differences introduced by the short averaging period. Therefore, researchers are urged to compare remotely sensed winds with buoy winds only when the distance between the center of the footprint and the buoy is considerably less than 100 km.

[1] Routine wave observations from buoys in the northeast Pacific now extend up to 35 years. Several recent studies reported long-term trends extracted from these records. However, significant modifications of the wave measurement hardware as well as the analysis procedures since the start of the observations result in inhomogeneities of the records. We analyze significant wave heights from seven offshore wave records. Several step changes of the mean monthly significant wave height of a few decimetres are identified. These changes are induced by buoy modifications and poor data quality rather than changes in the wave climate. After adjusting the data for these step changes the wave heights show positive trends for some of the southern locations and negative trends at the northern buoys, however all trends are much smaller than reported in previous studies. Storm wave heights are extracted from the occurrence rate distributions of the adjusted significant wave heights. No statistically significant trends can be established for storm wave heights.

Platforms of the National Data Buoy Center provide vital meteorological and oceanographic observations from data-sparse marine areas worldwide. The data are essential for real-time weather forecasting and research programs. This paper provides information on the data-acquisition systems, networks, monitoring capabilities, data processing and dissemination, data quality and availability, and related technology development for these platforms.

The National Data Buoy Center (NDBC) of the National Oceanic and Atmospheric Administration (NOAA) deployed a 10-m-diameter discus-type hull in the Pacific Ocean some 185 km southwest of Los Angeles, California, in April 1984. Aboard this hull was an electronic system capable of acquiring, processing, and transmitting to shore directional wave measurements. For this system to produce accurate data, a number of factors had to be taken into account. These factors included noise, amplitude and phase alterations due to mechanical and electrical components, and magnetic fields arising from the hull. Comprehensive calibration and verification techniques were developed and applied to ensure data quality. The system configuration is described with emphasis on the methods used in the data processing to correct for the various factors. Examples of the resulting corrected data are given.

The National Data Buoy Center (NDBC) began posting buoy estimates of swell height and period in 1997 because of numerous requests from mariners. Until then, only significant wave height, dominant period, and spectral wave data were posted on its Web site. Though swell information can be gleaned from the wave energy spectral, many mariners do not have the time or experience to do so. NDBC developed a method based on wave steepness that requires only nondirectional wave data. This method determines a period to separate the wind seas from the swell based on the knowledge that seas are steeper than swell and that maximum steepness occurs near the peak period of the wind waves. However, the method underestimates the swell when winds are light or abating, as compared to the Navy's operational wave model (WAM). To improve performance, the steepness method was modified to limit the maximum allowable separation period based on the observed wind speed. Since peak frequencies of fully developed seas generated by a given wind speed are well known, this relationship can be used to set an upper limit on the separation period. Positive results were obtained in tests of the modified method using measurements from directional buoys where swell and wind seas can be easily identified by differences in propagation direction. The modified method also compared much more favorably with wind sea and swell estimates from the WAM.

Abstract Processes controlling dissolved barium (dBa) were investigated along the GEOTRACES GA03 North Atlantic and GP16 Eastern Tropical Pacific transects, which traversed similar physical and biogeochemical provinces. Dissolved Ba concentrations are lowest in surface waters (∼35–50 nmol kg −1 ) and increase to 70–80 and 140–150 nmol kg −1 in deep waters of the Atlantic and Pacific transects, respectively. Using water mass mixing models, we estimate conservative mixing that accounts for most of dBa variability in both transects. To examine nonconservative processes, particulate excess Ba (pBa xs ) formation and dissolution rates were tracked by normalizing particulate excess 230 Th activities. Th‐normalized pBa xs fluxes, with barite as the likely phase, have subsurface maxima in the top 1,000 m (∼100–200 μmol m −2 year −1 average) in both basins. Barite precipitation depletes dBa within oxygen minimum zones from concentrations predicted by water mass mixing, whereas inputs from continental margins, particle dissolution in the water column, and benthic diffusive flux raise dBa above predications. Average pBa xs burial efficiencies along GA03 and GP16 are ∼37% and 17%–100%, respectively, and do not seem to be predicated on barite saturation indices in the overlying water column. Using published values, we reevaluate the global freshwater dBa river input as 6.6 ± 3.9 Gmol year −1 . Estuarine mixing processes may add another 3–13 Gmol year −1 . Dissolved Ba inputs from broad shallow continental margins, previously unaccounted for in global marine summaries, are substantial (∼17 Gmol year −1 ), exceeding terrestrial freshwater inputs. Revising river and shelf dBa inputs may help bring the marine Ba isotope budget more into balance.

This study concerns the use of selected geomagnetic field records to establish the 1990 quiet-day current system (Sq) for Australia and to use the ionospheric current source of Sq for a determination of the Earth’s deep electrical conductivity. The primary data set came from a chain of eight, three-component magnetometer stations that was operated along a north-south line in central Australia. Additional records, necessary for boundary conditions, were added to the data set. A regional spherical harmonic analysis (SHA) allowed the separation of the internal and external field contributions to the Sq variations. Mapping of the equivalent ionospheric current from the external field showed that the Sq contour focus passed near the —30° geomagnetic latitude of central Australia with a 5° latitude variation between winter and summer and a corresponding change from about 80 to 200 kA in strength. A special transfer function allowed the computation of an equivalent conductivity-depth profile of central Australia from the paired external and internal coefficients of the SHA. A regression line through the conductivity estimates gives a profile that starts at 0.025 S/m for a depth of 130 km, rising gradually to about 0.045 S/m at 250 km, then steepens to 0.11 S/m at 360 km and rises moderately to 0.13 S/m at 470 km near the base of the upper mantle. No data were obtained through the mantle transition zone. Computations gave 0.18 S/m in the region of 800 km depth. Previous conductivity models for the upper mantle beneath central Australia, although less specific in values, are consistent with our profile. At depths greater than 500 km, the regression profile is in agreement with the conductivity distribution beneath the Tasman Sea determined from seafloor magnetotellurics, although both measurements lack high resolution at such depths.

The architecture, status and applications of a realtime data access, distribution, processing and storage system designed for networking radial data from surface current mapping HF-Radar instruments across the United States is presented. By leveraging the system design of HF-Radar sites, data access is generalized to nearly all sites while still providing alternate access options where needed. Data format convergence, while not required, is achieved for data from all systems through careful metadata mapping and code development. Object ring buffers (ORBs) and ORB communication protocol provide robust and flexible data transport while a relational database facilitates data storage. The HF-Radar Network has evolved from a prototype project to an operational status over the last 2.5 years with 4 data access sites (portals) and 1 data aggregation site (node) deployed. By early 2007, an additional portal and 2 additional nodes will be added to create a distributed network. To date, the repository contains over 356,000 radial files produced by 45 sites from 10 participating institutions. Recent development has focused on real-time total vector processing on a national scale. Base grids for the U.S. West and East/Gulf Coast of 1 km nominal resolution extending 300km offshore are created using an equidistant cylindrical projection. A community standard MATLAB toolbox for total vector processing is optimized for production on large grids and integrated into the real-time system to produce hourly surface current maps on a national scale at 1 km, 2 km and 6 km resolutions. Current applications of the HF-Radar network include an interactive radial diagnostic site for use by site operators and a prototype interactive web site providing the first images of realtime surface currents integrated across a national scale

The National Data Buoy Center (NDBC) operates ocean and coastal buoys and coastal land stations that report hourly through the Geostationary Operational Environmental Satellite (GOES) system. In addition, NDBC maintains drifting-buoy networks that report through the polar-orbiting TIROS-N satellites. To disseminate information on these systems that provide vital environmental reports from data-sparse marine areas, the data-acquisition systems, networks, monitoring capabilities, data processing and distribution, data quality and availability, and future programs are discussed.

Quantifying the number of recreational fishers is important for many aspects of managing coastal resources. Unfortunately, quantifying recreational boaters in offshore settings has proven difficult due to their distance from shore and a lack of cost-effective methods to monitor small boats (<10 m length). We investigated visitor-use at an offshore marine protected area (MPA) in the southeastern USA. We used multiple methods of counting boats (satellites, buoy camera, passive acoustics, and boat-based observations) and a generalized linear modeling approach to identify environmental and calendar-based predictor variables that influenced visitation. Based on the model, predicted visitor-encounter rates were estimated for various weather and calendar-based scenarios, and the probability of detecting a hypothetical change in visitation with each counting method was examined through a power analysis. The most important predictors were day of the week, special day (e.g., tournament), water temperature, and wave height. Boat counts were 2–5 times higher on weekend days than on weekdays. More boats were predicted on weekdays with good weather (defined as water temperature 24 °C, wave height 0.5 m), than weekends with decent weather (17 °C and 1 m). Considering weekends alone, those with good weather were predicted to have 5 times higher visitation than weekends with decent weather. Predicted visitation was highest on calm days, dropped by ∼75 % when wave height reached 1 m, and was essentially zero when wave height exceeded 1.5 m. Highest counts were predicted when water temperature was warmest and gradually declined as temperatures cooled. For the buoy camera and passive acoustic boat-count methods, power analysis suggested that 3–6 years of typical samples before and after a hypothetical 25 % increase in visitation would be needed to have an 80 % chance of detecting the change. Other techniques would take 14 or more years of typical samples. The process used here for investigating visitation can be adapted to other offshore or remote locations.

Abstract The eye of Hurricane Katrina passed within 49 n mi of an oceanographic observing system buoy in the Mississippi Bight that is part of the Central Gulf of Mexico Ocean Observing System. Although a mechanical anemometer failed on the buoy during the hurricane, a two-axis sonic anemometer survived and provided a complete record of the hurricane’s passage. This is the first reported case of a sonic anemometer surviving a hurricane and reporting validated data, and it demonstrates that this type of anemometer is a viable alternative to the mechanical anemometers traditionally used in marine applications. The buoy pitch and roll record during the storm show the importance of compensating the anemometer records for winds oblique to the horizontal plane of the anemometers. This is made apparent in the comparison between the two wind records from the anemometers during the hurricane.

Abstract Forecasts by mid-2015 for a strong El Niño during winter 2015/16 presented an exceptional scientific opportunity to accelerate advances in understanding and predictions of an extreme climate event and its impacts while the event was ongoing . Seizing this opportunity, the National Oceanic and Atmospheric Administration (NOAA) initiated an El Niño Rapid Response (ENRR), conducting the first field campaign to obtain intensive atmospheric observations over the tropical Pacific during El Niño. The overarching ENRR goal was to determine the atmospheric response to El Niño and the implications for predicting extratropical storms and U.S. West Coast rainfall. The field campaign observations extended from the central tropical Pacific to the West Coast, with a primary focus on the initial tropical atmospheric response that links El Niño to its global impacts. NOAA deployed its Gulfstream-IV (G-IV) aircraft to obtain observations around organized tropical convection and poleward convective outflow near the heart of El Niño. Additional tropical Pacific observations were obtained by radiosondes launched from Kiritimati , Kiribati, and the NOAA ship Ronald H. Brown , and in the eastern North Pacific by the National Aeronautics and Space Administration (NASA) Global Hawk unmanned aerial system. These observations were all transmitted in real time for use in operational prediction models. An X-band radar installed in Santa Clara, California, helped characterize precipitation distributions. This suite supported an end-to-end capability extending from tropical Pacific processes to West Coast impacts. The ENRR observations were used during the event in operational predictions. They now provide an unprecedented dataset for further research to improve understanding and predictions of El Niño and its impacts.

This paper presents the results of an experiment designed to assess the directional spectrum resolution qualities of the pitch-roll-heave National Data Buoy Center-Surface Wave Dynamics Experiment (NDBC-SWADE) 3-m discus wave directional buoy in deep-water conditions. Wave frequency spectra and wave directional spectra measured by the buoy, moored in about 415-m water depth, are compared to similar measurements obtained from a wave staff and a biaxial current meter fixed to the nearby Bullwinkle platform (Gulf of Mexico). Both buoy and platform equipment operated simultaneously from 0000 UTC 29 May 1989 to 0100 UTC 24 June 1989. The analysis revealed that the buoy surface displacement energy spectra (estimated from heave acceleration) agree well with the platform spectra. Comparison of mean direction and directional width parameters is favorable considering the large variability of those estimators. Discrepancies are reduced when records of significant wave height less than 1 m are eliminated.

Three drifting buoys were successfully air-dropped ahead of Hurricane Josephine. This deployment resulted in detailed simultaneous measurements of surface wind speed, surface pressure and subsurface ocean temperature during and subsequent to storm passage. This represents the first time that such a self-consistent data set of surface conditions within a tropical cyclone has been collected. Subsequent NOAA research overflights of the buoys, as part of a hurricane planetary boundary-layer experiment, showed that aircraft wind speeds, extrapolated to the 20 m level, agreed to within ±2 m s−1, pressures agreed to within ±1 mb, and sea-surface temperatures agreed to within ±0.8°C of the buoy values. Ratios of buoy peak 1 min wind (sustained wind) to one-half h mean wind > 1.3 were found to coincide with eyewall and principal rainband features. Buoy trajectories and subsurface temperature measurements revealed the existence of a series of mesoscale eddies in the subtropical front. Buoy data revealed storm-generated, inertia-gravity-wave motions superposed upon mean current fields, which reached a maximum surface speed > 1.2 m s−1 immediately following storm passage. A maximum mixed-layer-temperature decrease of 1.8°C was observed to the right of the storm path. A temperature increase of 3.5°C at 100 m and subsequent decrease of 4.8°C following storm passage indicated a combination of turbulent mixing, upwelling and horizontal advection processes.

Abstract An intra-measurement evaluation was undertaken, deploying a NOMAD buoy equipped with three National Data Buoy Center and two Environment and Climate Change Canada-AXYS sensor/payload packages off Monterey, California; a Datawell Directional Waverider buoy was deployed within 19 km of the NOMAD site. The six independent wave measurement systems reported hourly estimates of the frequency spectra, and when applicable, the four Fourier directional components. The integral wave parameters showed general agreement among the five sensors compared to the neighboring Datawell Directional Waverider, with the Inclinometer and the Watchman performing similarly to the more sophisticated 3DMG, HIPPY, and Triaxys sensor packages. As the H m0 increased, all but the Inclinometer were biased low; however, even the Watchman reported reasonable wave measurements up to about 6–7 m, after which the H m0 becomes negatively biased up to about a meter, comparable to previous studies. The parabolic fit peak spectral wave period, T pp , results showed a large scatter, resulting from the complex nature of multiple swell wave systems compounded by local wind-sea development, exacerbated by a variable that can be considered as temporally unstable. The three directional sensors demonstrated that NOMAD buoys are capable of measuring directional wave properties along the western US coast, with biases of about 6 to 9 deg, and rms errors of approximately 30 deg. Frequency spectral evaluations found similarities in the shape, but a significant under estimation in the high frequency range. The results from slope analyses also revealed a positive bias in the rear face of the spectra, and a lack of invariance in frequency as suggested by theory.

Buoy azimuth, pitch, and roll, when used with measurements of buoy vertical acceleration, can provide directional wave spectra. Earlier work, which considered effects of buoy hull magnetism, showed that azimuth can be determined from magnetic field measurements (K.E. Steele and J.C. Lau, 1986). This work is extended to show that buoy pitch and roll, and thus buoy slopes, can also be determined from the same measurements. These slopes can be determined from measurements of the magnetic field components inside the hull along two orthogonal axes parallel to the deck of a buoy. Algorithms are developed for estimation of azimuth, pitch, and roll angles using these measurements. The algorithms account for residual and induced hull magnetism. Azimuth, pitch, roll, and estimates of directional wave spectra are determined both from the magnetic field measurements and from a conventional wave measurement system on the same buoy. Comparisons show that estimates of directional spectra based on magnetometer-derived pitch and roll agree well.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

In most wave-measuring payloads deployed by NDBC, the displacement spectra of the ocean is obtained from the acceleration spectra, as calculated from the readings of a vertical heave sensor, which is fixed in the hull of the buoy. Due to being fixed (strapped-down, as distinct from vertically stabilized), the accelerometer is subjected to motions other than vertical, and this distorts its readings, as discussed in [1] and [2]. Loosely speaking, there is a "spreading around" of energy from one frequency to the next. This is not a problem at higher frequencies. What a given frequency loses to its neighbors, it pretty well gets back from them, and any difference is a small percentage of the total energy in a real signal But at low frequencies, where there is little or no real signal, the spurious energy acquired from the rest of the spectrum has been shown to be significant. It is especially significant since the power transfer function, which converts from acceleration to displacement spectra, multiplies by the reciprocal of frequency to the power four, and will, therefore, greatly magnify any false signal. Because of this, NDBC applies a correction function to eliminate low-frequency noise, but there has been an ongoing problem with periodic noise spikes in some buoys. This paper describes a correction function that is designed to eliminate these problems.

Data buoy vandalism, which is an unlawful and willful interference with moored data buoys, has been a troublesome problem for the U.S. National Oceanic and Atmospheric (NOAA)/National Data Buoy Center (NDBC) and other buoy operators around the world. NDBC has three buoy networks-Weather and Ocean Platform (WxOP) program, Tropical Atmosphere/Ocean (TAO) buoy program, and the Tsunameter buoy program. In addition to the significant financial impact to NDBC's buoy programs and operations, vandalism disrupts the vital data collected and reported by moored buoys, which place lives, property, and economies in peril. Vandalism is not unique to just NDBC's buoy systems but is a national and international issue affecting both research and operational systems. This paper presents various vandalism incidents experienced by NDBC's three buoy networks. Prevention of buoy vandalism, including buoy and mooring system modifications, education and outreach, statutory penalty and enforcement, interagency efforts, and international cooperation and efforts, are also discussed.

The United States Coast Guard (USCG), as part of the Department of Homeland Security, is responsible for a wide variety of missions in the maritime domain. In order to support the accomplishment of these missions, the USCG needs to collect as much information as possible on activities occurring in the maritime domain. A large part of maritime activity relates to the movement of vessels. Therefore, detection, classification, identification and monitoring of vessels are a key component of what is known as Maritime Domain Awareness (MDA). The Automatic Identification System (AIS) is a technology that is used primarily as a tool for maritime safety, including vessel collision avoidance and as a means for coastal nations' Vessel Traffic Services (VTSs) to get information on vessels operating near their coasts. AIS equipment aboard vessels continuously and autonomously transmits information about the vessel including its identity, position, course, and speed to enhance safety. These transmissions can be received by other vessels or by land-based stations equipped with AIS receivers. The USCG sees the capability AIS provides, particularly for vessel tracking, as a major contributor to MDA and VTS. To extend the capability of USCG land-based AIS monitoring stations further offshore, the USCG Maritime Domain Awareness Program Integration Office sponsored the development of a near real-time, autonomous automatic identification and telemetry system based on AIS technology for installation on National Oceanic and Atmospheric Administration (NOAA) weather buoys through the National Data Buoy Center (NDBC) and its technical support contractor, Science Applications International Corporation (SAIC).