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  • American Meteorological Society  (15)
  • 1
    Online Resource
    Online Resource
    ASIRI: An Ocean–Atmosphere Initiative for Bay of Bengal
    American Meteorological Society ; 2016
    In:  Bulletin of the American Meteorological Society Vol. 97, No. 10 ( 2016-10-01), p. 1859-1884
    Details
    In: Bulletin of the American Meteorological Society, American Meteorological Society, Vol. 97, No. 10 ( 2016-10-01), p. 1859-1884
    Abstract: Air–Sea Interactions in the Northern Indian Ocean (ASIRI) is an international research effort (2013–17) aimed at understanding and quantifying coupled atmosphere–ocean dynamics of the Bay of Bengal (BoB) with relevance to Indian Ocean monsoons. Working collaboratively, more than 20 research institutions are acquiring field observations coupled with operational and high-resolution models to address scientific issues that have stymied the monsoon predictability. ASIRI combines new and mature observational technologies to resolve submesoscale to regional-scale currents and hydrophysical fields. These data reveal BoB’s sharp frontal features, submesoscale variability, low-salinity lenses and filaments, and shallow mixed layers, with relatively weak turbulent mixing. Observed physical features include energetic high-frequency internal waves in the southern BoB, energetic mesoscale and submesoscale features including an intrathermocline eddy in the central BoB, and a high-resolution view of the exchange along the periphery of Sri Lanka, which includes the 100-km-wide East India Coastal Current (EICC) carrying low-salinity water out of the BoB and an adjacent, broad northward flow (∼300 km wide) that carries high-salinity water into BoB during the northeast monsoon. Atmospheric boundary layer (ABL) observations during the decaying phase of the Madden–Julian oscillation (MJO) permit the study of multiscale atmospheric processes associated with non-MJO phenomena and their impacts on the marine boundary layer. Underway analyses that integrate observations and numerical simulations shed light on how air–sea interactions control the ABL and upper-ocean processes.
    Type of Medium: Online Resource
    ISSN: 0003-0007 , 1520-0477
    URL: Article
    DOI: 10.1175/BAMS-D-14-00197.1
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2016
    detail.hit.zdb_id: 2029396-3
    detail.hit.zdb_id: 419957-1
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  • 2
    Online Resource
    Online Resource
    Bay of Bengal Intraseasonal Oscillations and the 2018 Monsoon Onset
    American Meteorological Society ; 2021
    In:  Bulletin of the American Meteorological Society Vol. 102, No. 10 ( 2021-10), p. E1936-E1951
    Details
    In: Bulletin of the American Meteorological Society, American Meteorological Society, Vol. 102, No. 10 ( 2021-10), p. E1936-E1951
    Abstract: In the Bay of Bengal, the warm, dry boreal spring concludes with the onset of the summer monsoon and accompanying southwesterly winds, heavy rains, and variable air–sea fluxes. Here, we summarize the 2018 monsoon onset using observations collected through the multinational Monsoon Intraseasonal Oscillations in the Bay of Bengal (MISO-BoB) program between the United States, India, and Sri Lanka. MISO-BoB aims to improve understanding of monsoon intraseasonal variability, and the 2018 field effort captured the coupled air–sea response during a transition from active-to-break conditions in the central BoB. The active phase of the ∼20-day research cruise was characterized by warm sea surface temperature (SST 〉 30°C), cold atmospheric outflows with intermittent heavy rainfall, and increasing winds (from 2 to 15 m s −1 ). Accumulated rainfall exceeded 200 mm with 90% of precipitation occurring during the first week. The following break period was both dry and clear, with persistent 10–12 m s −1 wind and evaporation of 0.2 mm h −1 . The evolving environmental state included a deepening ocean mixed layer (from ∼20 to 50 m), cooling SST (by ∼1°C), and warming/drying of the lower to midtroposphere. Local atmospheric development was consistent with phasing of the large-scale intraseasonal oscillation. The upper ocean stores significant heat in the BoB, enough to maintain SST above 29°C despite cooling by surface fluxes and ocean mixing. Comparison with reanalysis indicates biases in air–sea fluxes, which may be related to overly cool prescribed SST. Resolution of such biases offers a path toward improved forecasting of transition periods in the monsoon.
    Type of Medium: Online Resource
    ISSN: 0003-0007 , 1520-0477
    URL: Article
    DOI: 10.1175/BAMS-D-20-0113.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2021
    detail.hit.zdb_id: 2029396-3
    detail.hit.zdb_id: 419957-1
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  • 3
    Online Resource
    Online Resource
    On the Development of SWOT In Situ Calibration/Validation for Short-Wavelength Ocean Topography
    American Meteorological Society ; 2022
    In:  Journal of Atmospheric and Oceanic Technology Vol. 39, No. 5 ( 2022-05), p. 595-617
    Details
    In: Journal of Atmospheric and Oceanic Technology, American Meteorological Society, Vol. 39, No. 5 ( 2022-05), p. 595-617
    Abstract: The future Surface Water and Ocean Topography (SWOT) mission aims to map sea surface height (SSH) in wide swaths with an unprecedented spatial resolution and subcentimeter accuracy. The instrument performance needs to be verified using independent measurements in a process known as calibration and validation (Cal/Val). The SWOT Cal/Val needs in situ measurements that can make synoptic observations of SSH field over an O (100) km distance with an accuracy matching the SWOT requirements specified in terms of the along-track wavenumber spectrum of SSH error. No existing in situ observing system has been demonstrated to meet this challenge. A field campaign was conducted during September 2019–January 2020 to assess the potential of various instruments and platforms to meet the SWOT Cal/Val requirement. These instruments include two GPS buoys, two bottom pressure recorders (BPR), three moorings with fixed conductivity–temperature–depth (CTD) and CTD profilers, and a glider. The observations demonstrated that 1) the SSH (hydrostatic) equation can be closed with 1–3 cm RMS residual using BPR, CTD mooring and GPS SSH, and 2) using the upper-ocean steric height derived from CTD moorings enable subcentimeter accuracy in the California Current region during the 2019/20 winter. Given that the three moorings are separated at 10–20–30 km distance, the observations provide valuable information about the small-scale SSH variability associated with the ocean circulation at frequencies ranging from hourly to monthly in the region. The combined analysis sheds light on the design of the SWOT mission postlaunch Cal/Val field campaign.
    Type of Medium: Online Resource
    ISSN: 0739-0572 , 1520-0426
    URL: Article
    DOI: 10.1175/JTECH-D-21-0039.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2022
    detail.hit.zdb_id: 2021720-1
    detail.hit.zdb_id: 48441-6
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  • 4
    Online Resource
    Online Resource
    Characterizing the Uncertainty and Assessing the Value of Gap-Filled Daily Rainfall Data in Hawaii
    American Meteorological Society ; 2020
    In:  Journal of Applied Meteorology and Climatology Vol. 59, No. 7 ( 2020-07-01), p. 1261-1276
    Details
    In: Journal of Applied Meteorology and Climatology, American Meteorological Society, Vol. 59, No. 7 ( 2020-07-01), p. 1261-1276
    Abstract: Almost all daily rainfall time series contain gaps in the instrumental record. Various methods can be used to fill in missing data using observations at neighboring sites (predictor stations). In this study, five computationally simple gap-filling approaches—normal ratio (NR), linear regression (LR), inverse distance weighting (ID), quantile mapping (QM), and single best estimator (BE)—are evaluated to 1) determine the optimal method for gap filling daily rainfall in Hawaii, 2) quantify the error associated with filling gaps of various size, and 3) determine the value of gap filling prior to spatial interpolation. Results show that the correlation between a target station and a predictor station is more important than proximity of the stations in determining the quality of a rainfall prediction. In addition, the inclusion of rain/no-rain correction on the basis of either correlation between stations or proximity between stations significantly reduces the amount of spurious rainfall added to a filled dataset. For large gaps, relative median errors ranged from 12.5% to 16.5% and no statistical differences were identified between methods. For submonthly gaps, the NR method consistently produced the lowest mean error for 1- (2.1%), 15- (16.6%), and 30-day (27.4%) gaps when the difference between filled and observed monthly totals was considered. Results indicate that gap filling prior to spatial interpolation improves the overall quality of the gridded estimates, because higher correlations and lower performance errors were found when 20% of the daily dataset is filled as opposed to leaving these data unfilled prior to spatial interpolation.
    Type of Medium: Online Resource
    ISSN: 1558-8424 , 1558-8432
    URL: Article
    DOI: 10.1175/JAMC-D-20-0007.1
    RVK:
    UA 4547
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2020
    detail.hit.zdb_id: 2227779-1
    detail.hit.zdb_id: 2227759-6
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  • 5
    Online Resource
    Online Resource
    Submesoscale Processes at Shallow Salinity Fronts in the Bay of Bengal: Observations during the Winter Monsoon
    American Meteorological Society ; 2018
    In:  Journal of Physical Oceanography Vol. 48, No. 3 ( 2018-03), p. 479-509
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 48, No. 3 ( 2018-03), p. 479-509
    Abstract: Lateral submesoscale processes and their influence on vertical stratification at shallow salinity fronts in the central Bay of Bengal during the winter monsoon are explored using high-resolution data from a cruise in November 2013. The observations are from a radiator survey centered at a salinity-controlled density front, embedded in a zone of moderate mesoscale strain (0.15 times the Coriolis parameter) and forced by winds with a downfront orientation. Below a thin mixed layer, often ≤10 m, the analysis shows several dynamical signatures indicative of submesoscale processes: (i) negative Ertel potential vorticity (PV); (ii) low-PV anomalies with O (1–10) km lateral extent, where the vorticity estimated on isopycnals and the isopycnal thickness are tightly coupled, varying in lockstep to yield low PV; (iii) flow conditions susceptible to forced symmetric instability (FSI) or bearing the imprint of earlier FSI events; (iv) negative lateral gradients in the absolute momentum field (inertial instability); and (v) strong contribution from differential sheared advection at O (1) km scales to the growth rate of the depth-averaged stratification. The findings here show one-dimensional vertical processes alone cannot explain the vertical stratification and its lateral variability over O (1–10) km scales at the radiator survey.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-16-0283.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2018
    detail.hit.zdb_id: 2042184-9
    detail.hit.zdb_id: 184162-2
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  • 6
    Online Resource
    Online Resource
    Numerical simulations of internal tide dynamics in a steep submarine canyon
    American Meteorological Society ; 2023
    In:  Journal of Physical Oceanography ( 2023-09-6)
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, ( 2023-09-6)
    Abstract: This study investigates three-dimensional semidiurnal internal tide (IT) energetics in the vicinity of La Jolla Canyon, a steep shelf submarine canyon off the South California Coast, with the SUNTANS numerical simulator. Numerical simulations show vertical structure and temporal phasing consistent with detailed field observations. ITs induce large (approximately 34-m peak-to-peak) isotherm displacements and net onshore IT energy flux up to 200 W m -1 . Although the net IT energy flux is onshore, the steep supercritical slope around the canyon results in strong reflection. The model provides the full life span of internal tides around the canyon, including internal tide generation, propagation and dissipation. ITs propagate into the canyon from the south and are reflected back towards offshore from the canyon’s north side. In the inner part of the canyon, elevated mixing occurs in the middle layer due to an interaction between incident mode-1 ITs and reflected higher-mode ITs. The magnitude of IT flux, generation and dissipation on the south side of the canyon are higher than those on the north side. An interference pattern in horizontal kinetic energy and available potential energy with a scale of approximately 20–50 km arises due to low-mode wave reflections. Our results provide new insight into IT dynamics associated with a small scale canyon topography.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-23-0040.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2023
    detail.hit.zdb_id: 2042184-9
    detail.hit.zdb_id: 184162-2
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  • 7
    Online Resource
    Online Resource
    Fine-Scale Velocity Measurement on the Wirewalker Wave-Powered Profiler
    American Meteorological Society ; 2022
    In:  Journal of Atmospheric and Oceanic Technology Vol. 39, No. 2 ( 2022-02), p. 133-147
    Details
    In: Journal of Atmospheric and Oceanic Technology, American Meteorological Society, Vol. 39, No. 2 ( 2022-02), p. 133-147
    Abstract: The Wirewalker (WW) ocean-wave-powered vertical profiling system allows the collection of high-resolution oceanographic data due to its rapid profiling, hydrodynamically quiet operation, and long endurance. We have assessed the potential for measuring fine-scale ocean velocities from the Wirewalker platform using commercially available acoustic velocimeters. Although the vertical profiling speed is relatively steady, platform motion affects the velocity measurements and requires correction. We present an algorithm to correct our velocity estimates using platform motion calculated from the inertial sensors—accelerometer, gyroscope, and magnetometer—on a Nortek Signature1000 acoustic Doppler current profiler (ADCP). This correction, carried out ping by ping, was effective in removing the vehicle motion from the measured velocities. The motion-corrected velocities contain contributions from surface wave orbital velocities, especially near the surface, and the background currents. To proceed, we use an averaging approach that leverages both the vertical platform profiling of the system and the ∼15–20 m vertical profiling range resolution of the down-looking ADCP to separate the surface wave orbital velocities and the background flow. The former can provide information on the wave conditions. From the latter, we are able to estimate fine-scale velocity and shear with spectral wavenumber rolloff at vertical scales around 3 m, a vertical resolution several times finer than that possible from modern shipboard or fixed ADCPs with similar profiling range, and similar to recent glider measurements. When combined with a continuous time series of buoy drift calculated from the onboard GPS, a highly resolved total velocity field is obtained, with a unique combination of space and time resolution.
    Type of Medium: Online Resource
    ISSN: 0739-0572 , 1520-0426
    URL: Article
    URL: Article
    DOI: 10.1175/JTECH-D-21-0048.1
    DOI: 10.1175/JTECH-D-21-0048.s1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2022
    detail.hit.zdb_id: 2021720-1
    detail.hit.zdb_id: 48441-6
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  • 8
    Online Resource
    Online Resource
    Distributed Temperature Sensing for Oceanographic Applications
    American Meteorological Society ; 2020
    In:  Journal of Atmospheric and Oceanic Technology Vol. 37, No. 11 ( 2020-11), p. 1987-1997
    Details
    In: Journal of Atmospheric and Oceanic Technology, American Meteorological Society, Vol. 37, No. 11 ( 2020-11), p. 1987-1997
    Abstract: Distributed temperature sensing (DTS) uses Raman scatter from laser light pulsed through an optical fiber to observe temperature along a cable. Temperature resolution across broad scales (seconds to many months, and centimeters to kilometers) make DTS an attractive oceanographic tool. Although DTS is an established technology, oceanographic DTS observations are rare since significant deployment, calibration, and operational challenges exist in dynamic oceanographic environments. Here, results from an experiment designed to address likely oceanographic DTS configuration, calibration, and data processing challenges provide guidance for oceanographic DTS applications. Temperature error due to suboptimal calibration under difficult deployment conditions is quantified for several common scenarios. Alternative calibration, analysis, and deployment techniques that help mitigate this error and facilitate successful DTS application in dynamic ocean conditions are discussed.
    Type of Medium: Online Resource
    ISSN: 0739-0572 , 1520-0426
    URL: Article
    DOI: 10.1175/JTECH-D-20-0066.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2020
    detail.hit.zdb_id: 2021720-1
    detail.hit.zdb_id: 48441-6
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  • 9
    Online Resource
    Online Resource
    Observations of Nonlinear Internal Wave Run-Up to the Surfzone
    American Meteorological Society ; 2018
    In:  Journal of Physical Oceanography Vol. 48, No. 3 ( 2018-03), p. 531-554
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 48, No. 3 ( 2018-03), p. 531-554
    Abstract: The cross-shore evolution of nonlinear internal waves (NLIWs) from 8-m depth to shore was observed by a dense thermistor array and ADCP. Isotherm oscillations spanned much of the water column at a variety of periods. At times, NLIWs propagated into the surfzone, decreasing temperature by ≈1°C in 5 min. When stratification was strong, temperature variability was strong and coherent from 18- to 6-m depth at semidiurnal and harmonic periods. When stratification weakened, temperature variability decreased and was incoherent between 18- and 6-m depth at all frequencies. At 8-m depth, onshore coherently propagating NLIW events had associated rapid temperature drops (Δ T ) up to 1.7°C, front velocity between 1.4 and 7.4 cm s −1 , and incidence angles between −5° and 23°. Front position, Δ T , and two-layer equivalent height z IW of four events were tracked upslope until propagation terminated. Front position was quadratic in time, and normalized Δ T and z IW both decreased, collapsing as a linearly decaying function of normalized cross-shore distance. Front speed and deceleration are consistent with two-layer upslope gravity current scalings. During NLIW rundown, near-surface cooling and near-bottom warming at 8-m depth coincide with a critical gradient Richardson number, indicating shear-driven mixing.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-17-0210.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2018
    detail.hit.zdb_id: 2042184-9
    detail.hit.zdb_id: 184162-2
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  • 10
    Online Resource
    Online Resource
    Turbulence Driven by Reflected Internal Tides in a Supercritical Submarine Canyon
    American Meteorological Society ; 2021
    In:  Journal of Physical Oceanography Vol. 51, No. 2 ( 2021-02), p. 591-609
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 51, No. 2 ( 2021-02), p. 591-609
    Abstract: The La Jolla Canyon System (LJCS) is a small, steep, shelf-incising canyon offshore of San Diego, California. Observations conducted in the fall of 2016 capture the dynamics of internal tides and turbulence patterns. Semidiurnal (D 2 ) energy flux was oriented up-canyon; 62% ± 20% of the signal was contained in mode 1 at the offshore mooring. The observed mode-1 D 2 tide was partly standing based on the ratio of group speed times energy c g E and energy flux F . Enhanced dissipation occurred near the canyon head at middepths associated with elevated strain arising from the standing wave pattern. Modes 2–5 were progressive, and energy fluxes associated with these modes were oriented down-canyon, suggesting that incident mode-1 waves were back-reflected and scattered. Flux integrated over all modes across a given canyon cross section was always onshore and generally decreased moving shoreward (from 240 ± 15 to 5 ± 0.3 kW), with a 50-kW increase in flux occurring on a section inshore of the canyon’s major bend, possibly due to reflection of incident waves from the supercritical sidewalls of the bend. Flux convergence from canyon mouth to head was balanced by the volume-integrated dissipation observed. By comparing energy budgets from a global compendium of canyons with sufficient observations (six in total), a similar balance was found. One exception was Juan de Fuca Canyon, where such a balance was not found, likely due to its nontidal flows. These results suggest that internal tides incident at the mouth of a canyon system are dissipated therein rather than leaking over the sidewalls or siphoning energy to other wave frequencies.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-20-0123.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2021
    detail.hit.zdb_id: 2042184-9
    detail.hit.zdb_id: 184162-2
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