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Recent Publications

  • Park Y., Seong W., Gerstoft P.  2020.  Block-sparse two-dimensional off-grid beamforming with arbitrary planar array geometry. 147:2184-2191.
    Abstract Summary:

    For a sound field observed on a planar sensor array, compressive sensing (CS) reconstructs the two-dimensional (2D) direction-of-arrival (DOA) of multiple sources using a sparsity constraint. Conventional compressive beamforming methods suffer from grid mismatch, where true DOAs do not fall on the discretized angular search grid. This paper adopts a CS-based model, which can reconstruct block-sparse signals, and the model treats DOAs and the...

  • Song HC, Byun G..  2020.  Extrapolating Green's functions using the waveguide invariant theory. 147:2150-2158.
    Abstract Summary:

    The broadband interference structure of sound propagation in a waveguide can be described by the waveguide invariant, beta, that manifests itself as striations in the frequency-range plane. At any given range (r), there is a striation pattern in frequency (omega), which is the Fourier transform of the multipath impulse response (or Green's function). Moving to a different range (r+Delta r), the same pattern is retained but is either stretched...

  • Abstract Summary:

    This study provides an initial demonstration of a combined two-UAV (Unmanned Aerial Vehicle) system for measuring the underwater source levels and behavioural context of vocal and non-vocal marine mammal signals, information that is highly ecologically-relevant in terms of understanding how a species interacts and copes with conspecifics and its acoustic environment. Although the calls of a few species are well known, major gaps exist in our...

  • Ozanich E., Gerstoft P, Niu H.Q.  2020.  A feedforward neural network for direction-of-arrival estimation. 147:2035-2048.
    Abstract Summary:

    This paper examines the relationship between conventional beamforming and linear supervised learning, then develops a nonlinear deep feed-forward neural network (FNN) for direction-of-arrival (DOA) estimation. First, conventional beamforming is reformulated as a real-valued, linear inverse problem in the weight space, which is compared to a support vector machine and a linear FNN model. In the linear formulation, DOA is quickly and accurately...

  • Abstract Summary:
  • Li J., Gerstoft P, Siderius M., Fan J..  2020.  Inversion of head waves in ocean acoustic ambient noise. 147:1752-1761.
    Abstract Summary:

    The virtual head wave is produced through cross-correlation processing of signals containing the real, acoustic head wave. The virtual head wave has the same phase speed as the head wave, but the travel time is offset, thus the term virtual. The virtual head wave, like the real head wave, propagates in a direction corresponding to the seabed critical angle. The virtual head wave travel time varies with array depth and water column depth....

  • Abstract Summary:

    Large aperture towed arrays are widely used underwater to detect weak targets. During maneuvering, the beamformer performance degrades significantly if a wrong array configuration is assumed. Currently, engineering sensors and/or (augmented) acoustic sources are used to estimate the array element positions. The results are often inadequate depending on the number of measurements available. In this paper, an adaptive bow (AB) sparse Bayesian...

  • Couto N., Alford MH, MacKinnon J., Mickett J.B.  2020.  Mixing rates and bottom drag in Bering Strait. 50:809-825.
    Abstract Summary:

    Three shipboard survey lines were occupied in Bering Strait during autumn of 2015, where high-resolution measurements of temperature, salinity, velocity, and turbulent dissipation rates were collected. These first-reported turbulence measurements in Bering Strait show that dissipation rates here are high even during calm winds. High turbulence in the strait has important implications for the modification of water properties during transit...

  • Abstract Summary:

    Classical ocean acoustic experiments involve the use of synchronized arrays of sensors. However, the need to cover large areas and/or the use of small robotic platforms has evoked interest in single-hydrophone processing methods for localizing a source or characterizing the propagation environment. One such processing method is "warping," a non-linear, physics-based signal processing tool dedicated to decomposing multipath features of low-...

  • Glowacki O., Deane GB.  2020.  Quantifying iceberg calving fluxes with underwater noise. 14:1025-1042.
    Abstract Summary:

    Accurate estimates of calving fluxes are essential in understanding small-scale glacier dynamics and quantifying the contribution of marine-terminating glaciers to both eustatic sea-level rise (SLR) and the freshwater budget of polar regions. Here we investigate the application of acoustical oceanography to measure calving flux using the underwater sounds of iceberg-water impact. A combination of time-lapse photography and passive acoustics...

  • Thode A.M, Blackwell S.B, Conrad A.S, Kim K.H, Marques T., Thomas L., Oedekoven C.S, Harris D., Broker K..  2020.  Roaring and repetition: How bowhead whales adjust their call density and source level (Lombard effect) in the presence of natural and seismic airgun survey noisea). 147:2061-2080.
    Abstract Summary:

    Over 500 000 automated and manual acoustic localizations, measured over seven years between 2008 and 2014, were used to examine how natural wind-driven noise and anthropogenic seismic airgun survey noise influence bowhead whale call densities (calls/km(2)/min) and source levels during their fall migration in the Alaskan Beaufort Sea. Noise masking effects, which confound measurements of behavioral changes, were removed using a modified point...

  • Simonis A.E, Forney KA, Rankin S., Ryan J., Zhang Y.W, DeVogelaere A., Joseph J., Margolina T., Krumpel A., Baumann-Pickering S..  2020.  Seal bomb noise as a potential threat to Monterey Bay harbor porpoise. 7
    Abstract Summary:

    Anthropogenic noise is a known threat to marine mammals. Decades of research have shown that harbor porpoises are particularly sensitive to anthropogenic noise, and geographic displacement is a common impact from noise exposure. Small, localized populations may be particularly vulnerable to impacts associated with displacement, as animals that are excluded from their primary habitat may have reduced foraging success and survival, or be...

  • Carvalho F., Fitzsimmons J.N, Couto N., Waite N., Gorbunov M., Kohut J., Oliver M.J, Sherrell R.M, Schofield O..  2020.  Testing the Canyon Hypothesis: Evaluating light and nutrient controls of phytoplankton growth in penguin foraging hotspots along the West Antarctic Peninsula. 65:455-470.
    Abstract Summary:

    Biological hotspots along the West Antarctic Peninsula (WAP) are characterized by high phytoplankton productivity and biomass as well as spatially focused penguin foraging activity. While unique physical concentrating processes were identified in one of these hotspots, understanding the mechanisms driving the blooms at these locations is of high importance. Factors posited to explain the blooms include the upwelling of macronutrient- and...

  • Jaeger G.S, Lucas A.J, Mahadevan A..  2020.  Formation of interleaving layers in the Bay of Bengal. 172
    Abstract Summary:

    Observations of the upper 200 m of the strongly stratified Bay of Bengal reveal a host of interleaving layers of watermass properties. The features appear as isopycnal spice anomalies and form multiple, parallel, similar to 10 m thin layers, that are coherent over horizontal scales of 30-80 km. They are coincident with anomalies in density stratification and in some cases, with the vertical shear of horizontal velocity, but are not aligned...

  • Byun G., Akins F.H, Gemba K.L, Song HC, Kuperman WA.  2020.  Multiple constraint matched field processing tolerant to array tilt mismatch. 147:1231-1238.
    Abstract Summary:

    A multiple constraint method (MCM) specifically designed to accommodate the uncertainty of array tilt is developed for matched field processing (MFP). Combining the MCM with the white noise gain constraint method results in a processor that is tolerant to both array tilt and environmental mismatch. Experimental results verify the robustness of the proposed MFP to localize and track a surface ship radiating broadband noise (200-500 Hz), using...

  • Trehu A.M, de Moor A., Madrid J.M, Saez M., Chadwell C.D, Ortega-Culaciati F., Ruiz J., Ruiz S., Tryon M.D.  2020.  Post-seismic response of the outer accretionary prism after the 2010 Maule earthquake, Chile. 16:13-32.
    Abstract Summary:

    To investigate the dynamic response of the outer accretionary prism up-dip from the patch of greatest slip during the 2010 M-w 8.8 Maule earthquake (Chile), 10 ocean-bottom seismometers (OBSs) were deployed from May 2012 to March 2013 in a small network with an inter-instrument spacing of 710 km. Nine were recovered, with four recording data from intermediate-band three-component seismometers and differential pressure gauges, and five...

  • Shroyer E.L, Gordon A.L, Jaeger G.S, Freilich M., Waterhouse A.F, Farrar J.T, Sarma V, Venkatesan R., Weller RA, Moum J.N et al..  2020.  Upper layer thermohaline structure of the Bay of Bengal during the 2013 northeast monsoon. 172
    Abstract Summary:

    The Bay of Bengal is forced by the South Asian monsoon and associated seasonally reversing winds and freshwater fluxes. Here, we summarize a high-resolution, basin-wide survey of the Bay of Bengal conducted during the 2013 northeast (winter) monsoon. The observed mixed layer waters were sourced from the eastern Bay; and, generally, the upper ocean temperature-salinity properties followed regional trends as determined by Argo. Intense lateral...

  • Abstract Summary:

    Some high-resolution CTD data collected in the spring of 2017 are analyzed using Thorpe sorting and scale analyses, including both the commonly used "Thorpe scale" method and a lesser-used method that is based on directly estimating the "available overturn potential energy" (AOPE): the difference between potential energies of the raw versus sorted density profiles in a mixing "turbulent patch." The speed of the profiler varied, so the spatial...

  • Solsona-Berga A., Frasier K.E, Baumann-Pickering S., Wiggins SM, Hildebrand JA.  2020.  DetEdit: A graphical user interface for annotating and editing events detected in long-term acoustic monitoring data. 16
    Abstract Summary:

    Passive acoustic monitoring has become an important data collection method, yielding massive datasets replete with biological, environmental and anthropogenic information. Automated signal detectors and classifiers are needed to identify events within these datasets, such as the presence of species-specific sounds or anthropogenic noise. These automated methods, however, are rarely a complete substitute for expert analyst review. The ability...

  • Abstract Summary:

    The autonomous passive-acoustic lander Deep Sound was deployed at five locations during the Office of Naval Research (ONR)-supported Seabed Characterization Experiment, a multi-institutional field effort held at the New England Mud Patch, where the seabed is known to consist of a thick layer of silt and clay overlying a medium and coarse sand. The five deployments of Deep Sound were up to 9h long, during which time ambient noise data, taken...

  • Abstract Summary:

    Marginal probability distributions for parameters representing an effective sound-speed structure of a fine-grained sediment are inferred from a data ensemble maximum entropy method that utilizes a sparse spatially distributed set of received pressure time series resulting from multiple explosive sources in a shallow-water ocean environment possessing significant spatial variability of the seabed. A remote sensing seabed acoustics experiment...

  • McSweeney J.M, Lerczak J.A, Barth J.A, Becherer J., Colosi J.A, MacKinnon JA, Macmahan J.H, Moum J.N, Pierce S.D, Waterhouse A.F.  2020.  Observations of shoaling nonlinear internal bores across the central California inner shelf. 50:111-132.
    Abstract Summary:

    We present observations of shoaling nonlinear internal bores off the coast of central California. The dataset includes 15 moorings deployed during September-October 2017 and cross-shore shipboard surveys. We describe the cross-shore structure and evolution of large-amplitude internal bores as they transit from 9 km (100-m depth) to 1 km offshore (10 m). We observe that two bores arrive each semidiurnal period, both propagating from the...

  • Abstract Summary:

    Radar interferograms provide a map of the phase difference between the reference and repeat acquisitions modulo . Under ideal conditions, the phase can be unwrapped to provide an absolute phase connection across the map, although there is always an unknown integer phase ambiguity (i.e., ) for the entire map. Here, we demonstrate a practical time series method to solve for these integer ambiguities in order to recover the absolute phase change...

  • Schramek T.A, Terrill E.J, Colin P.L, Cornuelle BD.  2019.  Coastally trapped waves around Palau. 191
    Abstract Summary:

    Observations from around the main island group of Palau, located in the tropical Western Pacific, exhibit a persistent presence of baroclinic coastally trapped waves. The signals are found in records of temperature that were sustained on the fore-reef for seven months, May to December 2013, with the strongest signal from Typhoon Haiyan which passed over Kayangel Atoll, along with the northern most Palauan islands, in November of 2013. This...

  • Simmons H.L, Powell B.S, Merrifield S.T, Zedler S.E, Colin P.L.  2019.  Dynamical downscaling of equatorial flow response to Palau. 32:84-91.
    Abstract Summary:

    The wake created by the interaction of equatorial currents with the Palau islands generates small-scale vortices. We aim to identify the significant scales of this vortex wake by studying its structure and variability. We utilize a subkilometer resolution numerical model integrated from May 2016 through April 2017 that is nested within a 2.5 km state estimate hindcast model. The near-Palau flow is highly variable and has very different wake...

  • Andres M., Siegelman M., Hormann V., Musgrave R.C, Merrifield S.T, Rudnick D.L, Merrifield M.A, Alford MH, Voet G., Wijesekera H.W et al..  2019.  Eddies, topography, and the abyssal flow by the Kyushu-Palau Ridge near Velasco Reef. 32:46-55.
    Abstract Summary:

    Palau, an island group in the tropical western North Pacific at the southern end of Kyushu-Palau Ridge, sits near the boundary between the westward-flowing North Equatorial Current (NEC) and the eastward-flowing North Equatorial Countercurrent. Combining remote-sensing observations of the sea surface with an unprecedented in situ set of subsurface measurements, we examine the flow near Palau with a particular focus on the abyssal circulation...

  • Girton J.B, Mickett J.B, Zhao Z.X, Alford MH, Voet G., Cusack J.M, Carter G.S, Pearson-Potts K.A, Pratt L.J, Tan S.W et al..  2019.  Flow-topography interactions in the Samoan Passage. 32:184-193.
    Abstract Summary:

    Mixing in the Samoan Passage has implications for the abyssal water properties of the entire North Pacific-nearly 20% of the global ocean's volume. Dense bottom water formed near Antarctica encounters the passage-a gap in a ridge extending from north of Samoa eastward across the Pacific at around 10 degrees S-and forms an energetic cascade much like a river flowing through a canyon. The 2011-2014 Samoan Passage Abyssal Mixing Experiment...

  • Merrifield S.T, Colin P.L, Cook T., Garcia-Moreno C., MacKinnon JA, Otero M, Schrnmek T.A, Siegeman M., Simmons H.L, Terrill E.J.  2019.  Island wakes observed from high-frequency current mapping radar. 32:92-101.
    Abstract Summary:

    The interaction of large-scale oceanic flows with remote island chains can lead to turbulent wakes, enhanced vorticity production, and significant increases in biological productivity. This study showcases the range of flow conditions captured by surface current mapping high-frequency (HF) radar systems deployed around the main island group of Palau in the western Pacific. The radar array captures strong tidal and inertial flows, both near-...

  • Colin P.L, Johnston T.MS, MacKinnon JA, Ou C.Y, Rudnick D.L, Terrill E.J, Lindfield S.J, Batchelor H..  2019.  Ngaraard Pinnacle, Palau: An Undersea “Island” in the Flow. 32:164-173.
    Abstract Summary:

    This paper uses the Flow Encountering Abrupt Topography (FLEAT) experiment's unique data set to examine and document the biophysical environment of an unusual low-light reef habitat in the western tropical Pacific Ocean. Located 1.6 km seaward of the eastern coast of Palau, Ngaraard Pinnacle (NP) rises from the deep ocean to 92 m depth, constituting an "island" where such a habitat exists. Low-light reef habitats have not been well studied...

  • Garwood J.C, Lucas A.J, Naughton P., Alford MH, Roberts P.LD, Jaffe J.S, DeGelleke L., Franks PJS.  2019.  A novel cross-shore transport mechanism revealed by subsurface, robotic larval mimics: Internal wave deformation of the background velocity field.
    Abstract Summary:

    Coastal physical processes are essential for the cross-shore transport of meroplanktonic larvae to their benthic adult habitats. To investigate these processes, we released a swarm of novel, trackable, subsurface vehicles, the Mini-Autonomous Underwater Explorer (M-AUEs), which we programmed to mimic larval depth-keeping behavior. The M-AUE swarm measured a sudden net onshore transport of 30-70 m over 15-20 min, which we investigated in...

  • Siegelman M., Merrifield M.A, Firing E., MacKinnon JA, Alford MH, Voet G., Wijesekera H.W, Schramek T.A, Zeiden K.L, Terrill E.J.  2019.  Observations of near-inertial surface currents at Palau. 32:74-83.
    Abstract Summary:

    An impulsive or rotary wind stress can excite near-inertial oscillations (NIOs) in the surface mixed layer. Although previous work shows that coastal boundaries modify NIOs, few studies have explored their behavior near island topography. Understanding how topography modifies NIOs provides insight into physical processes that contribute to local mixing, which enhances biological richness near islands. Here, encounters between NIOs and the...

  • Cusack J.M, Voet G., Alford MH, Girton J.B, Carter G.S, Pratt L.J, Pearson-Potts K.A, Tan S.W.  2019.  Persistent turbulence in the Samoan Passage. 49:3179-3197.
    Abstract Summary:

    Abyssal waters forming the lower limb of the global overturning circulation flow through the Samoan Passage and are modified by intense mixing. Thorpe-scale-based estimates of dissipation from moored profilers deployed on top of two sills for 17 months reveal that turbulence is continuously generated in the passage. Overturns were observed in a density band in which the Richardson number was often smaller than 1/4, consistent with shear...

  • Baker M.G, Aster R.C, Anthony R.E, Chaput J., Wiens D.A, Nyblade A., Bromirski PD, Gerstoft P, Stephen R.A.  2019.  Seasonal and spatial variations in the ocean-coupled ambient wavefield of the Ross Ice Shelf. 65:912-925.
    Abstract Summary:

    The Ross Ice Shelf (RIS) is host to a broadband, multimode seismic wavefield that is excited in response to atmospheric, oceanic and solid Earth source processes. A 34-station broadband seismographic network installed on the RIS from late 2014 through early 2017 produced continuous vibrational observations of Earth's largest ice shelf at both floating and grounded locations. We characterize temporal and spatial variations in broadband ambient...

  • Carter G.S, Voet G., Alford MH, Girton J.B, Mickett J.B, Klymak J.M, Pratt L.J, Pearson-Potts K.A, Cusack J.M, Tan S.W.  2019.  A spatial geography of abyssal turbulent mixing in the Samoan Passage. 32:194-203.
    Abstract Summary:

    High levels of turbulent mixing have long been suspected in the Samoan Passage, an important topographic constriction in the deep limb of the Pacific Meridional Overturning Circulation. Along the length of the passage, observations undertaken in 2012 and 2014 showed the bottom water warmed by similar to 55 millidegrees Celsius and decreased in density by 0.01 kg m(-3). Spatial analysis of this first-ever microstructure survey conducted in the...

  • Franks PJS, Garwood J.C, Ouimet M., Cortes J., Musgrave R.C, Lucas A.J.  2019.  Stokes drift of plankton in linear internal waves: Cross-shore transport of neutrally buoyant and depth-keeping organisms.
    Abstract Summary:

    The meroplanktonic larvae of many invertebrate and vertebrate species rely on physical transport to move them across the shelf to their adult habitats. One potential mechanism for cross-shore larval transport is Stokes drift in internal waves. Here, we develop theory to quantify the Stokes velocities of neutrally buoyant and depth-keeping organisms in linear internal waves in shallow water. We apply the analyses to theoretical and measured...

  • Gallimore E., Anderson M., Freitag L., Terrill E.  2019.  Synthetic baseline navigation using phase-coherent acoustic communication signals. 146:4831-4841.
    Abstract Summary:

    The development of a synthetic baseline navigation technique that self-localizes an autonomous underwater vehicle (AUV) using intermittent acoustic communications signals received by a single transducer is described, along with field results from in-ocean tests. The method uses the phase measurement at the output of a second-order phase-locked loop to create fine-scale pseudorange estimates in addition to, or in the absence of, a one-way...

  • St Laurent L., Ijichi T., Merrifield S.T, Shapiro J., Simmons H.L.  2019.  Turbulence and vorticity in the wake of Palau. 32:102-109.
    Abstract Summary:

    The inleraclion of flow with sleep island and ridge topography at the Palau island chain leads to rich vorticity fields that generate a cascade of motions. The energy transfer to small scales removes energy from the large-scale mean flow of the equatorial current systems and feeds energy to the fine and microstructure scales where instability mechanisms lead to turbulence and dissipation. Until now, direct assessments of the turbulence...

  • Merrifield S.T, Schramek T.A, Celona S., Boas A.BV, Colin P.L, Terrill E.J.  2019.  Typhoon-forced waves around a western Pacific island nation. 32:56-65.
    Abstract Summary:

    Over the last decade, the Pacific island nation of Palau, situated at 7 degrees N, has had a number of close encounters with Category 4 and 5 typhoons, including the named storms Bopha, Haiyan, and Lan in 2012, 2013, and 2017, respectively. Although historically, due to its low latitude location, typhoon activity has been rare in Palau, it was in the direct path of typhoons Bopha and Haiyan, which caused extensive wind damage, reef...

  • Rudnick D.L, Zeiden K.A, Ou C.Y, Johnston T.MS, MacKinnon JA, Alford MH, Voet G..  2019.  Understanding vorticity caused by flow passing an island. 32:66-73.
    Abstract Summary:

    This article presents a pedagogical approach toward understanding vorticity generated in flow past an island. The ubiquity of eddies in the ocean motivates the use of vorticity to quantify their rotation, and we define two kinds of vorticity: relative vorticity, that is, the vorticity of an eddy relative to Earth, and planetary vorticity, Earth's spin relative to local vertical. The ratio of relative to planetary vorticity is the Rossby...

  • Lenain L., Statom N.M, Melville W.K.  2019.  Airborne measurements of surface wind and slope statistics over the ocean. 49:2799-2814.
    Abstract Summary:

    As reported in 1954, more than a half century ago, C. Cox and W. Munk developed an empirical model of the slope distribution of ocean surface waves that has been widely used ever since to model the optical properties of the sea surface and is of particular importance to the satellite remote sensing community. In that work, the reflectance of sunlight was photographed from a Boeing B-17G bomber and was then analyzed. In this paper, surface...

  • Bianco M.J, Gerstoft P, Traer J., Ozanich E., Roch M.A, Gannot S., Deledalle C.A.  2019.  Machine learning in acoustics: Theory and applications. 146:3590-3628.
    Abstract Summary:

    Acoustic data provide scientific and engineering insights in fields ranging from biology and communications to ocean and Earth science. We survey the recent advances and transformative potential of machine learning (ML), including deep learning, in the field of acoustics. ML is a broad family of techniques, which are often based in statistics, for automatically detecting and utilizing patterns in data. Relative to conventional acoustics and...

  • Abstract Summary:

    An extensive data set of measurements within the Chukchi and Beaufort Seas is used to characterize the optical properties of seawater associated with different phytoplankton communities. Hierarchical cluster analysis of diagnostic pigment concentrations partitioned stations into four distinct surface phytoplankton communities based on taxonomic composition and average cell size. Concurrent optical measurements of spectral absorption and...

  • Wang W.B, Ni H.Y, Su L., Hu T., Ren Q.Y, Gerstoft P, Ma L..  2019.  Deep transfer learning for source ranging: Deep-sea experiment results. 146:EL317-EL322.
    Abstract Summary:

    A deep transfer learning for underwater source ranging is proposed, which migrates the predictive ability obtained from synthetic environment (source domain) into an experimental sea area (target domain). A deep neural network is first trained on large synthetic datasets generated from historical environmental data, and then part of the neural network is refined on collected data set for source ranging. Its performance is tested on a deep-sea...

  • Hennon T.D, Alford MH, Zhao Z.X.  2019.  Global assessment of semidiurnal internal tide aliasing in Argo profiles. 49:2523-2533.
    Abstract Summary:

    Though unresolved by Argo floats, internal waves still impart an aliased signal onto their profile measurements. Recent studies have yielded nearly global characterization of several constituents of the stationary internal tides. Using this new information in conjunction with thousands of floats, we quantify the influence of the stationary, mode-1 M-2 and S-2 internal tides on Argo-observed temperature. We calculate the in situ temperature...

  • Lenain L., Pizzo N., Melville W.K.  2019.  Laboratory studies of Lagrangian transport by breaking surface waves. 876
    Abstract Summary:

    While it has long been recognized that Lagrangian drift at the ocean surface plays a critical role in the kinematics and dynamics of upper ocean processes, only recently has the contribution of wave breaking to this drift begun to be investigated through direct numerical simulations (Deike et al., J. Fluid Mech., vol. 829, 2017, pp. 364-391; Pizzo et al., J. Phys. Oceanogr., vol. 49(4), 2019, pp. 983-992). In this work, laboratory...

  • Ty A.JA, Fang Z., Gonzalez R.A, Rozdeba P.J, Abarbanel H.DI.  2019.  Machine learning of time series using time-delay embedding and precision annealing. 31:2004-2024.
    Abstract Summary:

    Tasking machine learning to predict segments of a time series requires estimating the parameters of a ML model with input/output pairs from the time series. We borrow two techniques used in statistical data assimilation in order to accomplish this task: time-delay embedding to prepare our input data and precision annealing as a training method. The precision annealing approach identifies the global minimum of the action (-log[P]). In this way...

  • Nelson A.D, Arbic B.K, Zaron E.D, Savage A.C, Richman J.G, Buijsman M.C, Shriver J.F.  2019.  Toward realistic nonstationarity of semidiurnal baroclinic tides in a hydrodynamic model.
    Abstract Summary:

    Semidiurnal baroclinic tide sea surface height (SSH) variance and semidiurnal nonstationary variance fraction (SNVF) are compared between a hydrodynamic model and altimetry for the low- to middle-latitude global ocean. Tidal frequencies are aliased by similar to 10-day altimeter sampling, which makes it impossible to unambiguously identify nonstationary tidal signals from the observations. In order to better understand altimeter sampling...

  • Shields J.E, Burden A.R, Karr M.E.  2019.  Atmospheric cloud algorithms for day/night whole sky imagers. 58:7050-7062.
    Abstract Summary:

    This paper discusses new atmospheric cloud algorithms that we have developed to detect the presence and location of clouds in images of the sky acquired by day/night whole sky imagers, and to categorize the douds by opacity. The day/night whole sky imagers that we developed are ground-based sensors that acquire digital imagery of the full sky down to the horizon in several visible spectral bands and a near-infrared spectral band. The...

  • Romero L., Ohlmann J.C, Pallas-Sanz E., Statom N.M, Perez-Brunius P., Maritorena S..  2019.  Coincident observations of dye and drifter relative dispersion over the inner shelf. 49:2447-2468.
    Abstract Summary:

    Coincident Lagrangian observations of coastal circulation with surface drifters and dye tracer were collected to better understand small-scale physical processes controlling transport and dispersion over the inner shelf in the Gulf of Mexico. Patches of rhodamine dye and clusters of surface drifters at scales of O(100) m were deployed in a cross-shelf array within 12 km from the coast and tracked for up to 5 h with airborne and in situ...

  • Stramski D, Reynolds R.A, Gernez P., Rottgers R., Wurld O..  2019.  Inherent optical properties and particle characteristics of the sea-surface microlayer. 176
    Abstract Summary:

    The sea-surface microlayer (SML) is known to have physical, chemical, and biological properties that are distinctly different from the underlying subsurface water (USW). However, only a few studies in the past reported on measurements of the optical properties of the SML and were limited to light absorption. In this study we present results for the main inherent optical properties (IOPs), the spectral absorption coefficients and the volume...

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