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Kurekin, Andrey A., Peter E. Land, and Peter I. Miller. "Internal Waves at the UK Continental Shelf: Automatic Mapping Using the ENVISAT ASAR Sensor." Remote Sensing 12, no. 15 (August 2, 2020): 2476. http://dx.doi.org/10.3390/rs12152476.
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Oceanic internal waves occur within stratified water along the boundary between water layers of different density and are generated when strong tidal currents flow over seabed topography. Their amplitude can exceed 50 m and they transport energy over long distances and cause vertical mixing when the waves break. This study presents the first fully automated methodology for the mapping of internal waves using satellite synthetic aperture radar (SAR) data and applies this to explore their spatial and temporal distribution within UK shelf seas. The new algorithm includes enhanced edge detection and spatial processing to target the appearance of these features on satellite images. We acquired and processed over 7000 ENVISAT ASAR scenes covering the UK continental shelf between 2006 and 2012, to automatically generate detailed maps of internal waves. Monthly and annual internal wave climatology maps of the continental shelf were produced showing spatial and temporal variability, which can be used to predict where internal waves have the most impact on the seabed environment and ecology in UK shelf seas. These observations revealed correlations between the temporal patterns of internal waves and the seasons when the continental shelf waters were more stratified. The maps were validated using well-known seabed topographic features. Concentrations of internal waves were automatically identified at Wyville-Thomson Ridge in June 2008, at the continental shelf break to the east of Rosemary Bank in January 2010 and in the Faroe-Shetland Channel in June 2011. This new automated methodology has been shown to be robust for mapping internal waves using a large SAR dataset and is recommended for studies in other regions worldwide and for SAR data acquired by other sensors.
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Derstroff, Bettina, Imke Hüser, Efstratios Bourtsoukidis, John N. Crowley, Horst Fischer, Sergey Gromov, Hartwig Harder, et al. "Volatile organic compounds (VOCs) in photochemically aged air from the eastern and western Mediterranean." Atmospheric Chemistry and Physics 17, no. 15 (August 9, 2017): 9547–66. http://dx.doi.org/10.5194/acp-17-9547-2017.
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Abstract. During the summertime CYPHEX campaign (CYprus PHotochemical EXperiment 2014) in the eastern Mediterranean, multiple volatile organic compounds (VOCs) were measured from a 650 m hilltop site in western Cyprus (34° 57′ N/32° 23′ E). Periodic shifts in the northerly Etesian winds resulted in the site being alternately impacted by photochemically processed emissions from western (Spain, France, Italy) and eastern (Turkey, Greece) Europe. Furthermore, the site was situated within the residual layer/free troposphere during some nights which were characterized by high ozone and low relative humidity levels. In this study we examine the temporal variation of VOCs at the site. The sparse Mediterranean scrub vegetation generated diel cycles in the reactive biogenic hydrocarbon isoprene, from very low values at night to a diurnal median level of 80–100 pptv. In contrast, the oxygenated volatile organic compounds (OVOCs) methanol and acetone exhibited weak diel cycles and were approximately an order of magnitude higher in mixing ratio (ca. 2.5–3 ppbv median level by day, range: ca. 1–8 ppbv) than the locally emitted isoprene and aromatic compounds such as benzene and toluene. Acetic acid was present at mixing ratios between 0.05 and 4 ppbv with a median level of ca. 1.2 ppbv during the daytime. When data points directly affected by the residual layer/free troposphere were excluded, the acid followed a pronounced diel cycle, which was influenced by various local effects including photochemical production and loss, direct emission, dry deposition and scavenging from advecting air in fog banks. The Lagrangian model FLEXPART was used to determine transport patterns and photochemical processing times (between 12 h and several days) of air masses originating from eastern and western Europe. Ozone and many OVOC levels were ∼ 20 and ∼ 30–60 % higher, respectively, in air arriving from the east. Using the FLEXPART calculated transport time, the contribution of photochemical processing, sea surface contact and dilution was estimated. Methanol and acetone decreased with residence time in the marine boundary layer (MBL) with loss rate constants of 0.74 and 0.53 day−1 from eastern Europe and 0.70 and 0.34 day−1 from western Europe, respectively. Simulations using the EMAC model underestimate these loss rates. The missing sink in the calculation is most probably an oceanic uptake enhanced by microbial consumption of methanol and acetone, although the temporal and spatial variability in the source strength on the continents might play a role as well. Correlations between acetone and methanol were weaker in western air masses (r2 = 0.68), but were stronger in air masses measured after the shorter transport time from the east (r2 = 0.73).
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Paredi, Davide, Tommaso Lucchini, Gianluca D’Errico, Angelo Onorati, Lyle Pickett, and Joshua Lacey. "Validation of a comprehensive computational fluid dynamics methodology to predict the direct injection process of gasoline sprays using Spray G experimental data." International Journal of Engine Research 21, no. 1 (August 22, 2019): 199–216. http://dx.doi.org/10.1177/1468087419868020.
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A detailed prediction of injection and air–fuel mixing is fundamental in modern direct injection, spark-ignition engines to guarantee a stable and efficient combustion process and to minimize pollutant formation. Within this context, computational fluid dynamics simulations nowadays represent a powerful tool to understand the in-cylinder evolution of spray and air–fuel charge. To guarantee the accuracy of the adopted multidimensional spray sub-models, it is mandatory to validate the computed results against available experimental data under well-defined operating conditions. To this end, in this work, the authors proposed the calibration and validation of a comprehensive set of spray sub-models by means of the simulation of the Spray G experiment, available in the context of the engine combustion network. For a suitable validation of the proposed numerical setup in addition to the baseline condition, gasoline direct injection operating points typical of early injection with homogeneous operation, late injection with high ambient density and flash boiling with enhanced fuel evaporation were also simulated. Numerical computations were validated against a wide set of available experimental data by means of an accurate post-processing analysis taking into account axial liquid and vapor penetrations, gas-phase velocity between spray plumes, droplet size, plume liquid velocity, direction and mass distribution. Satisfactory results were achieved with the proposed setup, which is able to predict gasoline spray evolution under different operating conditions.
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Ding, Yongsheng, Hua Han, and Fengming Liu. "Intelligent integrated data processing model for oceanic warning system." Knowledge-Based Systems 23, no. 1 (February 2010): 61–69. http://dx.doi.org/10.1016/j.knosys.2009.07.003.
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Fu, Hongli, Jinkun Yang, Wei Li, Xinrong Wu, Guijun Han, Yuanfu Xie, Shaoqing Zhang, Xuefeng Zhang, Yingzhi Cao, and Xiaoshuang Zhang. "A Potential Density Gradient Dependent Analysis Scheme for Ocean Multiscale Data Assimilation." Advances in Meteorology 2017 (2017): 1–13. http://dx.doi.org/10.1155/2017/9315601.
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This study addresses how to maintain oceanic mixing along potential density surface in ocean data assimilation (ODA). It is well known that the oceanic mixing across the potential density surface is much weaker than that along the potential density surface. However, traditional ODA schemes allow the mixing across the potential density surface and thus may result in extra assimilation errors. Here, a new ODA scheme that uses potential density gradient information of the model background to rescale observational adjustment is designed to improve the quality of assimilation. The new scheme has been tested using a regional ocean model within a multiscale 3-dimensional variational framework. Results show that the new scheme effectively prevents the excessive unphysical projection of observational information in the direction across potential density surface and thus improves assimilation quality greatly. Forecast experiments also show that the new scheme significantly improves the model forecast skills through providing more dynamically consistent initial conditions
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Tziperman, Eli. "Calculating the Time-Mean Oceanic General Circulation and Mixing Coefficients from Hydrographic Data." Journal of Physical Oceanography 18, no. 3 (March 1988): 519–25. http://dx.doi.org/10.1175/1520-0485(1988)018<0519:cttmog>2.0.co;2.
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Subramanian, A. C., A. J. Miller, B. D. Cornuelle, E. Di Lorenzo, R. A. Weller, and F. Straneo. "A data assimilative perspective of oceanic mesoscale eddy evolution during VOCALS-REx." Atmospheric Chemistry and Physics Discussions 12, no. 8 (August 20, 2012): 20901–30. http://dx.doi.org/10.5194/acpd-12-20901-2012.
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Abstract. Oceanic observations collected during the VOCALS-REx cruise time period, 1–30 November 2008, are assimilated into a regional ocean model (ROMS) using 4DVAR and then analyzed for their dynamics. Nonlinearities in the system prevent a complete 30-day fit, so two 15-day fits for 1–15 November and 16–30 November are executed using the available observations of hydrographic temperature and salinity, along with satellite fields of SST and sea-level height anomaly. The fits converge and reduce the cost function significantly, and the results indicated that ROMS is able to successfully reproduce both large-scale and smaller-scale features of the flows observed during the 76° W, 19° S. The ROMS fits capture this eddy as an isolated rotating 3-D vortex with a strong subsurface signature in velocity, temperature and anomalously low salinity. The eddy has an average temperature anomaly of approximately −0.5 °C over a depth range from 50–600 m and features a cold anomaly of approximately −1 °C near 150 m depth. The eddy moves northwestward and elongates during the second 15-day fit. It exhibits a strong signature in the Okubo-Weiss parameter, which indicates significant nonlinearity in its evolution. The heat balance for the period of the cruise from the ocean state estimate reveals that the horizontal advection and the vertical mixing processes are the dominant terms that balance the temperature tendency of the upper layer of the ocean locally in time and space. Areal averages, however, around the eddies and around the cruise tracks, suggest that vertical mixing processes generally balance the surface heating, indicating only a small role for lateral advective processes in this region.
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Kantha, Lakshmi, and Hubert Luce. "Mixing Coefficient in Stably Stratified Flows." Journal of Physical Oceanography 48, no. 11 (November 2018): 2649–65. http://dx.doi.org/10.1175/jpo-d-18-0139.1.
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AbstractTurbulent mixing in the interior of the oceans is not as well understood as mixing in the oceanic boundary layers. Mixing in the generally stably stratified interior is primarily, although not exclusively, due to intermittent shear instabilities. Part of the energy extracted by the Reynolds stresses acting on the mean shear is expended in increasing the potential energy of the fluid column through a buoyancy flux, while most of it is dissipated. The mixing coefficient χm, the ratio of the buoyancy flux to the dissipation rate of turbulence kinetic energy ε, is an important parameter, since knowledge of χm enables turbulent diffusivities to be inferred. Theory indicates that χm must be a function of the gradient Richardson number. Yet, oceanic studies suggest that a value of around 0.2 for χm gives turbulent diffusivities that are in good agreement with those inferred from tracer studies. Studies by scientists working with atmospheric radars tend to reinforce these findings but are seldom referenced in oceanographic literature. The goal of this paper is to bring together oceanographic, atmospheric, and laboratory observations related to χm and to report on the values deduced from in situ data collected in the lower troposphere by unmanned aerial vehicles, equipped with turbulence sensors and flown in the vicinity of the Middle and Upper Atmosphere (MU) radar in Japan. These observations are consistent with past studies in the oceans, in that a value of around 0.16 for χm yields good agreement between ε derived from turbulent temperature fluctuations using this value and ε obtained directly from turbulence velocity fluctuations.
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Blacic, T. M., and W. S. Holbrook. "First images and orientation of internal waves from a 3-D seismic oceanography data set." Ocean Science Discussions 6, no. 3 (October 20, 2009): 2341–56. http://dx.doi.org/10.5194/osd-6-2341-2009.
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Abstract. We present 3-D images of ocean finestructure from a unique industry-collected 3-D multichannel seismic dataset from the Gulf of Mexico that includes expendable bathythermograpgh casts for both swaths. 2-D processing reveals strong laterally continuous reflectors throughout the upper ~800 m as well as a few weaker but still distinct reflectors as deep as ~1100 m. Two bright reflections are traced across the 225-m-wide swath to produce reflector surface images that show the 3-D structure of internal waves. We show that the orientation of internal wave crests can be obtained by calculating the orientations of contours of reflector relief. Preliminary 3-D processing further illustrates the potential of 3-D seismic data in interpreting images of oceanic features such as internal wave strains. This work demonstrates the viability of imaging oceanic finestructure in 3-D and shows that, beyond simply providing a way to see what oceanic finestructure looks like, quantitative information such as the spatial orientation of features like internal waves and solitons can be obtained from 3-D seismic images. We expect complete, optimized 3-D processing to improve both the signal to noise ratio and spatial resolution of our images resulting in increased options for analysis and interpretation.
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Barth, M. F., R. B. Chadwick, and D. W. van de Kamp. "Data processing algorithms used by NOAA's wind profiler demonstration network." Annales Geophysicae 12, no. 6 (May 31, 1994): 518–28. http://dx.doi.org/10.1007/s00585-994-0518-1.
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Abstract. The National Oceanic and Atmospheric Administration's (NOAA) Wind Profiler Demonstration Network consists of 32 wind profiling radars, based primarily in the central United States. The network is being used to determine the operational feasibility and characteristics of a possible future nationwide profiler network. Data processing is performed both at the individual profiler sites and at a central hub processing system. This paper documents the algorithms used at the profilers to produce profiles of the moments of the velocity spectrum every 6 minutes, as well as those used on the hub to produce quality-controlled hourly winds.
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Subramanian, A. C., A. J. Miller, B. D. Cornuelle, E. Di Lorenzo, R. A. Weller, and F. Straneo. "A data assimilative perspective of oceanic mesoscale eddy evolution during VOCALS-REx." Atmospheric Chemistry and Physics 13, no. 6 (March 25, 2013): 3329–44. http://dx.doi.org/10.5194/acp-13-3329-2013.
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Abstract. Oceanic observations collected during the VOCALS-REx cruise time period, 1–30 November 2008, are assimilated into a regional ocean model (ROMS) using 4DVAR and then analyzed for their dynamics. Nonlinearities in the system prevent a complete 30-day fit, so two 15-day fits for 1–15 November and 16–30 November are executed using the available observations of hydrographic temperature and salinity, along with satellite fields of SST and sea-level height anomaly. The fits converge and reduce the cost function significantly, and the results indicated that ROMS is able to successfully reproduce both large-scale and smaller-scale features of the flows observed during the VOCALS-REx cruise. Particular attention is focused on an intensively studied eddy at 76° W, 19° S. The ROMS fits capture this eddy as an isolated rotating 3-D vortex with a strong subsurface signature in velocity, temperature and anomalously low salinity. The eddy has an average temperature anomaly of approximately −0.5 °C over a depth range from 50–600 m and features a cold anomaly of approximately −1 °C near 150 m depth. The eddy moves northwestward and elongates during the second 15-day fit. It exhibits a strong signature in the Okubo-Weiss parameter, which indicates significant nonlinearity in its evolution. The heat balance for the period of the cruise from the ocean state estimate reveals that the horizontal advection and the vertical mixing processes are the dominant terms that balance the temperature tendency of the upper layer of the ocean locally in time and space. Areal averages around the eddies, for a 15-day period during the cruise, suggest that vertical mixing processes generally balance the surface heating. Although, this indicates only a small role for lateral advective processes in this region during this period, this quasi-instantaneous heat budget analysis cannot be extended to interpret the seasonal or long-term upper ocean heat budget in this region.
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Barret, Brice, Yvan Gouzenes, Eric Le Flochmoen, and Sylvain Ferrant. "Retrieval of Metop-A/IASI N2O Profiles and Validation with NDACC FTIR Data." Atmosphere 12, no. 2 (February 5, 2021): 219. http://dx.doi.org/10.3390/atmos12020219.
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This paper reports atmospheric profiles of N2O retrieved from Metop/IASI with the Software for the Retrieval of IASI Data (SOFRID) for the 2008–2018 period and their validation with FTIR data from 12 stations of the Network for the Detection of Atmospheric Composition Changes (NDACC). SOFRID retrievals performed in the 2160–2218 cm−1 spectral window provide 3 independent pieces of information about the vertical profile of N2O. The FTIR versus SOFRID comparisons display a better agreement in the mid-troposphere (MT, 700–350 hPa) than in the lower (LT, Surface–700 hPa) and upper (UT, 350–110 hPa) troposphere with correlation coefficients (R) in the 0.49–0.83 range and comparable variabilities (3–5 ppbv). The agreement for oceanic and coastal stations (R > 0.77) is better than for continental ones (R < 0.72). The SOFRID MT N2O mixing ratios are significantly biased high (up to 16.8 ppbv) relative to FTIR at continental stations while the biases remain below 4.2 ppbv and mostly unsignificant when oceanic data are considered. The average MT decadal trends derived from SOFRID at the 8 NDACC stations with continuous observations during the 2008–2018 period (1.05 ± 0.1 ppbv·yr−1) is in good agreement with the corresponding FTIR trends (1.08 ± 0.1 ppbv·yr−1) and the NOAA-ESRL trends from surface in-situ measurements (0.95 ± 0.02 ppbv·yr−1). In the Northern Hemisphere where they are clearly detected, the N2O MT seasonal variations from SOFRID and FTIR are phased (summer minima) and have similar amplitudes. SOFRID also detects the UT summer maxima indicating independent MT and UT information. The global MT N2O oceanic distributions from SOFRID display low geographical variability and are mainly characterized by enhanced tropical mixing ratios relative to mid and high latitudes.
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Johns, Michael A., Jorge R. Valdés Kroff, and Paola E. Dussias. "Mixing things up: How blocking and mixing affect the processing of codemixed sentences." International Journal of Bilingualism 23, no. 2 (February 5, 2018): 584–611. http://dx.doi.org/10.1177/1367006917752570.
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Aims and objectives/purpose/research questions: The goal of this study is to determine if the way in which codemixed sentences are presented during experimental lab sessions affects the way they are processed, and how experimental design approximates (or not) patterns of language use in bilingual populations. Design/methodology/approach: An eye-tracking study was conducted comparing reading times on codemixed and unilingual Spanish sentences across two modes of presentation: (a) a blocked mode, where one block contained unilingual Spanish sentences and another one contained codemixed sentences; and (b) a mixed mode, where both unilingual and codemixed sentences were mixed together in a randomized fashion. Data and analysis: 20 heritage speakers of Spanish were tested. Four reading measures extracted from the eye-tracking data were subjected to linear mixed-effects regression, with significance determined via backwards likelihood ratio tests, to examine differences across modes of presentation. Findings/conclusions: Codemixes took significantly longer to process in the blocked mode than in the mixed mode. This is in line with corpus data suggesting that intra-sentential codemixing does not occur for long stretches of time and is broken up by unilingual discourse. Originality: While a few studies have hinted at the potential confounds related to the presentation of codemixed or language-switching stimuli, the direct effects of experimental manipulation coupled with insights from sociolinguistic or corpus-based studies have not been tested. Significance/implications: To better understand bilingual codemixing, as well as the cost (or lack thereof) associated with it, lab-based studies of codemixing should take insights from sociolinguistic and corpus-based research. The results of this study suggest that the experience that participants bring into the lab can interact with experimental design and result in unexpected results.
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Blacic, T. M., and W. S. Holbrook. "First images and orientation of fine structure from a 3-D seismic oceanography data set." Ocean Science 6, no. 2 (April 20, 2010): 431–39. http://dx.doi.org/10.5194/os-6-431-2010.
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Abstract. We present 3-D images of ocean fine structure from a unique industry-collected 3-D multichannel seismic dataset from the Gulf of Mexico that includes expendable bathythermograph casts for both swaths. 2-D processing reveals strong laterally continuous reflections throughout the upper ~800 m as well as a few weaker but still distinct reflections as deep as ~1100 m. We interpret the reflections to be caused by reversible fine structure from internal wave strains. Two bright reflections are traced across the 225-m-wide swath to produce reflection surface images that illustrate the 3-D nature of ocean fine structure. We show that the orientation of linear features in a reflection can be obtained by calculating the orientations of contours of reflection relief, or more robustly, by fitting a sinusoidal surface to the reflection. Preliminary 3-D processing further illustrates the potential of 3-D seismic data in interpreting images of oceanic features such as internal wave strains. This work demonstrates the viability of imaging oceanic fine structure in 3-D and shows that, beyond simply providing a way visualize oceanic fine structure, quantitative information such as the spatial orientation of features like fronts and solitons can be obtained from 3-D seismic images. We expect complete, optimized 3-D processing to improve both the signal to noise ratio and spatial resolution of our images resulting in increased options for analysis and interpretation.
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Xu, Suqing, Keyhong Park, Yanmin Wang, Liqi Chen, Di Qi, and Bingrui Li. "Variations in the summer oceanic <i>p</i>CO<sub>2</sub> and carbon sink in Prydz Bay using the self-organizing map analysis approach." Biogeosciences 16, no. 3 (February 13, 2019): 797–810. http://dx.doi.org/10.5194/bg-16-797-2019.
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Abstract. This study applies a neural network technique to produce maps of oceanic surface pCO2 in Prydz Bay in the Southern Ocean on a weekly 0.1∘ longitude × 0.1∘ latitude grid based on in situ measurements obtained during the 31st CHINARE cruise from February to early March 2015. This study area was divided into three regions, namely, the “open-ocean” region, “sea-ice” region and “shelf” region. The distribution of oceanic pCO2 was mainly affected by physical processes in the open-ocean region, where mixing and upwelling were the main controls. In the sea-ice region, oceanic pCO2 changed sharply due to the strong change in seasonal ice. In the shelf region, biological factors were the main control. The weekly oceanic pCO2 was estimated using a self-organizing map (SOM) with four proxy parameters (sea surface temperature, chlorophyll a concentration, mixed Layer Depth and sea surface salinity) to overcome the complex relationship between the biogeochemical and physical conditions in the Prydz Bay region. The reconstructed oceanic pCO2 data coincide well with the in situ pCO2 data from SOCAT, with a root mean square error of 22.14 µatm. Prydz Bay was mainly a strong CO2 sink in February 2015, with a monthly averaged uptake of 23.57±6.36 TgC. The oceanic CO2 sink is pronounced in the shelf region due to its low oceanic pCO2 values and peak biological production.
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Löptien, Ulrike, and Heiner Dietze. "Reciprocal bias compensation and ensuing uncertainties in model-based climate projections: pelagic biogeochemistry versus ocean mixing." Biogeosciences 16, no. 9 (May 6, 2019): 1865–81. http://dx.doi.org/10.5194/bg-16-1865-2019.
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Abstract. Anthropogenic emissions of greenhouse gases such as CO2 and N2O impinge on the Earth system, which in turn modulates atmospheric greenhouse gas concentrations. The underlying feedback mechanisms are complex and, at times, counterintuitive. So-called Earth system models have recently matured to standard tools tailored to assess these feedback mechanisms in a warming world. Applications for these models range from being targeted at basic process understanding to the assessment of geo-engineering options. A problem endemic to all these applications is the need to estimate poorly known model parameters, specifically for the biogeochemical component, based on observational data (e.g., nutrient fields). In the present study, we illustrate with an Earth system model that through such an approach biases and other model deficiencies in the physical ocean circulation model component can reciprocally compensate for biases in the pelagic biogeochemical model component (and vice versa). We present two model configurations that share a remarkably similar steady state (based on ad hoc measures) when driven by historical boundary conditions, even though they feature substantially different configurations (parameter sets) of ocean mixing and biogeochemical cycling. When projected into the future the similarity between the model responses breaks. Metrics such as changes in total oceanic carbon content and suboxic volume diverge between the model configurations as the Earth warms. Our results reiterate that advancing the understanding of oceanic mixing processes will reduce the uncertainty of future projections of oceanic biogeochemical cycles. Related to the latter, we suggest that an advanced understanding of oceanic biogeochemical cycles can be used for advancements in ocean circulation modules.
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Mamberti, Marc, Henriette Lapierre, Delphine Bosch, Etienne Jaillard, Jean Hernandez, and Mireille Polvé. "The Early Cretaceous San Juan Plutonic Suite, Ecuador: a magma chamber in an oceanic plateau?" Canadian Journal of Earth Sciences 41, no. 10 (October 1, 2004): 1237–58. http://dx.doi.org/10.1139/e04-060.
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Sections through an oceanic plateau are preserved in tectonic slices in the Western Cordillera of Ecuador (South America). The San Juan section is a sequence of maficultramafic cumulates. To establish that these plutonic rocks formed in an oceanic plateau setting, we have developed criteria that discriminate intrusions of oceanic plateaus from those of other tectonic settings. The mineralogy and crystallization sequence of the cumulates are similar to those of intra-plate magmas. Clinopyroxene predominates throughout, and orthopyroxene is only a minor component. Rocks of intermediate composition are absent, and hornblende is restricted to the uppermost massive gabbros within the sequence. The ultramafic cumulates are very depleted in light rare-earth elements (LREE), whereas the gabbros have flat or slightly enriched LREE patterns. The composition of the basaltic liquid in equilibrium with the peridotite, calculated using olivine compositions and REE contents of clinopyroxene, contains between 16% and 8% MgO and has a flat REE pattern. This melt is geochemically similar to other accreted oceanic plateau basalts, isotropic gabbros, and differentiated sills in western Ecuador. The Ecuadorian intrusive and extrusive rocks have a narrow range of εNdi (+8 to +5) and have a rather large range of Pb isotopic ratios. Pb isotope systematics of the San Juan plutonic rocks and mineral separates lie along a mixing line between the depleted mantle (DMM) and the enriched-plume end members. This suggests that the Ecuadorian plutonic rocks generated from the mixing of two mantle sources, a depleted mid-oceanic ridge basalt (MORB) source and an enriched one. The latter is characterized by high (207Pb/204Pb)i ratios and could reflect a contamination by recycled either lower continental crust or oceanic pelagic sediments and (or) altered oceanic crust (enriched mantle type I, EMI). These data suggest that the San Juan sequence represents the plutonic components of an Early Cretaceous oceanic plateau, which accreted in the Late Cretaceous to the Ecuadorian margin.
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Luo, G., and F. Yu. "A numerical evaluation of global oceanic emissions of α-pinene and isoprene." Atmospheric Chemistry and Physics 10, no. 4 (February 19, 2010): 2007–15. http://dx.doi.org/10.5194/acp-10-2007-2010.
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Abstract. A numerical evaluation of global oceanic emissions of α-pinene and isoprene based on both "bottom-up" and "top-down" methods is presented. We infer that the global "bottom-up" oceanic emissions of α-pinene and isoprene are 0.013 TgC yr−1 and 0.32 TgC yr−1, respectively. By constraining global chemistry model simulations with the shipborne measurement of Organics over the Ocean Modifying Particles in both Hemispheres summer cruise, we derived the global "top-down" oceanic α-pinene source of 29.5 TgC yr−1 and isoprene source of 11.6 TgC yr−1. Both the "bottom-up" and "top-down" values are subject to large uncertainties. The incomplete understanding of the in-situ phytoplankton communities and their range of emission potentials significantly impact the estimated global "bottom-up" oceanic emissions, while the estimated total amounts of the global "top-down" oceanic sources can be influenced by emission parameterizations, model and input data spatial resolutions, boundary layer mixing processes, and the treatments of chemical reactions. The global oceanic α-pinene source and its impact on organic aerosol formation is significant based on "top-down" method, but is negligible based on "bottom-up" approach. Our research highlights the importance of carrying out further research (especially measurements) to resolve the large offset in the derived oceanic organic emission based on two different approaches.
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Carlisle, Aaron B., Kenneth J. Goldman, Steven Y. Litvin, Daniel J. Madigan, Jennifer S. Bigman, Alan M. Swithenbank, Thomas C. Kline, and Barbara A. Block. "Stable isotope analysis of vertebrae reveals ontogenetic changes in habitat in an endothermic pelagic shark." Proceedings of the Royal Society B: Biological Sciences 282, no. 1799 (January 22, 2015): 20141446. http://dx.doi.org/10.1098/rspb.2014.1446.
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Ontogenetic changes in habitat are driven by shifting life-history requirements and play an important role in population dynamics. However, large portions of the life history of many pelagic species are still poorly understood or unknown. We used a novel combination of stable isotope analysis of vertebral annuli, Bayesian mixing models, isoscapes and electronic tag data to reconstruct ontogenetic patterns of habitat and resource use in a pelagic apex predator, the salmon shark ( Lamna ditropis ). Results identified the North Pacific Transition Zone as the major nursery area for salmon sharks and revealed an ontogenetic shift around the age of maturity from oceanic to increased use of neritic habitats. The nursery habitat may reflect trade-offs between prey availability, predation pressure and thermal constraints on juvenile endothermic sharks. The ontogenetic shift in habitat coincided with a reduction of isotopic niche, possibly reflecting specialization upon particular prey or habitats. Using tagging data to inform Bayesian isotopic mixing models revealed that adult sharks primarily use neritic habitats of Alaska yet receive a trophic subsidy from oceanic habitats. Integrating the multiple methods used here provides a powerful approach to retrospectively study the ecology and life history of migratory species throughout their ontogeny.
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Jenkins, William J., Scott C. Doney, Michaela Fendrock, Rana Fine, Toshitaka Gamo, Philippe Jean-Baptiste, Robert Key, et al. "A comprehensive global oceanic dataset of helium isotope and tritium measurements." Earth System Science Data 11, no. 2 (April 5, 2019): 441–54. http://dx.doi.org/10.5194/essd-11-441-2019.
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Abstract. Tritium and helium isotope data provide key information on ocean circulation, ventilation, and mixing, as well as the rates of biogeochemical processes and deep-ocean hydrothermal processes. We present here global oceanic datasets of tritium and helium isotope measurements made by numerous researchers and laboratories over a period exceeding 60 years. The dataset's DOI is https://doi.org/10.25921/c1sn-9631, and the data are available at https://www.nodc.noaa.gov/ocads/data/0176626.xml (last access: 15 March 2019) or alternately http://odv.awi.de/data/ocean/jenkins-tritium-helium-data-compilation/ (last access: 13 March 2019) and includes approximately 60 000 valid tritium measurements, 63 000 valid helium isotope determinations, 57 000 dissolved helium concentrations, and 34 000 dissolved neon concentrations. Some quality control has been applied in that questionable data have been flagged and clearly compromised data excluded entirely. Appropriate metadata have been included, including geographic location, date, and sample depth. When available, we include water temperature, salinity, and dissolved oxygen. Data quality flags and data originator information (including methodology) are also included. This paper provides an introduction to the dataset along with some discussion of its broader qualities and graphics.
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Gačić, Miroslav, and Manuel Bensi. "Ocean Exchange and Circulation." Water 12, no. 3 (March 20, 2020): 882. http://dx.doi.org/10.3390/w12030882.
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The great spatial and temporal variability, which characterizes the marine environment, requires a huge effort to be observed and studied properly since changes in circulation and mixing processes directly influence the variability of the physical and biogeochemical properties. A multi-platform approach and a collaborative effort, in addition to optimizing both data collection and quality, is needed to bring the scientific community to more efficient monitoring and predicting of the world ocean processes. This Special Issue consists of nine original scientific articles that address oceanic circulation and water mass exchange. Most of them deal with mean circulation, basin and sub-basin-scale flows, mesoscale eddies, and internal processes (e.g., mixing and internal waves) that contribute to the redistribution of oceanic properties and energy within the ocean. One paper deals with numerical modelling application finalized to evaluate the capacity of coastal vegetated areas to mitigate the impact of a tsunami. The study areas in which these topics are developed include both oceanic areas and semi-enclosed seas such as the Mediterranean Sea, the Norwegian Sea and the Fram Strait, the South China Sea, and the Northwest Pacific. Scientific findings presented in this Special Issue highlight how a combination of various modern observation techniques can improve our understanding of the complex physical and biogeochemical processes in the ocean.
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Lawrimore, Jay H., David Wuertz, Anna Wilson, Scott Stevens, Matthew Menne, Bryant Korzeniewski, Michael A. Palecki, Ronald D. Leeper, and Thomas Trunk. "Quality Control and Processing of Cooperative Observer Program Hourly Precipitation Data." Journal of Hydrometeorology 21, no. 8 (August 1, 2020): 1811–25. http://dx.doi.org/10.1175/jhm-d-19-0300.1.
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AbstractThe National Oceanic and Atmospheric Administration (NOAA) has operated a network of Fischer & Porter gauges providing hourly and subhourly precipitation observations as part of the U.S. Cooperative Observer Program since the middle of the twentieth century. A transition from punched paper recording to digital recording was completed by NOAA’s National Weather Service in 2013. Subsequently, NOAA’s National Centers for Environmental Information (NCEI) upgraded its quality assurance and data stewardship processes to accommodate the new digital record, better assure the quality of the data, and improve the timeliness by which hourly precipitation observations are made available to the user community. Automated methods for removing noise, detecting diurnal variations, and identifying malfunctioning gauges are described along with quality control algorithms that are applied on hourly and daily time scales. The quality of the hourly observations during the digital era is verified by comparison with hourly observations from the U.S. Climate Reference Network and summary of the day precipitation totals from the Global Historical Climatology Network dataset.
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Jaimes, Benjamin, Lynn K. Shay, and George R. Halliwell. "The Response of Quasigeostrophic Oceanic Vortices to Tropical Cyclone Forcing." Journal of Physical Oceanography 41, no. 10 (October 1, 2011): 1965–85. http://dx.doi.org/10.1175/jpo-d-11-06.1.
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Abstract The response of quasigeostrophic (QG) oceanic vortices to tropical cyclone (TC) forcing is investigated using an isopycnic ocean model. Idealized oceanic currents and wind fields derived from observational data acquired during Hurricane Katrina are used to initialize this model. It is found that the upwelling response is a function of the curl of wind-driven acceleration of oceanic mixed layer (OML) currents rather than a function of the wind stress curl. Upwelling (downwelling) regimes prevail under the TC’s eye as it translates over cyclonic (anticyclonic) QG vortices. OML cooling of ~1°C occurs over anticyclones because of the combined effects of downwelling, instantaneous turbulent entrainment over the deep warm water column (weak stratification), and vertical dispersion of near-inertial energy. By contrast, OML cooling of ~4°C occurs over cyclones due to the combined effects of upwelling, instantaneous turbulent entrainment over regions of tight vertical thermal gradients (strong stratification), and trapping of near-inertial energy that enhances vertical shear and mixing at the OML base. The rotational rate of the QG vortex affects the dispersion of near-inertial waves. As rotation is increased in both cyclones and anticyclones, the near-inertial response is shifted toward more energetic frequencies that enhance vertical shear and mixing. TC-induced temperature anomalies in QG vortices propagate westward with time, deforming the cold wake. Therefore, to accurately simulate the impact of TC-induced OML cooling and feedback mechanisms on storm intensity, coupled ocean–atmosphere TC models must resolve geostrophic ocean eddy location as well as thermal, density, and velocity structures.
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Zheng, Hua, Junhao Liu, and Shiqiang Duan. "Flutter Test Data Processing Based on Improved Hilbert-Huang Transform." Mathematical Problems in Engineering 2018 (August 12, 2018): 1–8. http://dx.doi.org/10.1155/2018/3496870.
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Flutter tests are conducted primarily for the purpose of modal parameter estimation and flutter boundary prediction, the accuracy of which is severely affected by the acquired data quality, structural modal density, and nonstationary conditions. An improved Hilbert-Huang Transform (HHT) algorithm is presented in this paper which mitigates the typical mode mixing effect via modulation. The algorithm is validated by theory, by numerical simulation, and per actual flight flutter test data. The results show that the proposed method could extract the flutter model parameters and predict the flutter speed more accurately, which is feasible for the current flutter test data processing.
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Kunii, Masaru, Kosuke Ito, and Akiyoshi Wada. "Preliminary Test of a Data Assimilation System with a Regional High-Resolution Atmosphere–Ocean Coupled Model Based on an Ensemble Kalman Filter." Monthly Weather Review 145, no. 2 (February 2017): 565–81. http://dx.doi.org/10.1175/mwr-d-16-0068.1.
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An ensemble Kalman filter (EnKF) that uses a regional mesoscale atmosphere–ocean coupled model was preliminarily examined to provide realistic sea surface temperature (SST) estimates and to represent the uncertainties of SST in ensemble data assimilation strategies. The system was evaluated through data assimilation cycle experiments over a one-month period from July to August 2014, during which time a tropical cyclone (TC) as well as severe rainfall events occurred. The results showed that the data assimilation cycle with the coupled model reproduced SST distributions realistically even without assimilating SST and sea surface salinity observations, and atmospheric variables provided to ocean models can, therefore, control oceanic variables physically to some extent. The forecast error covariance calculated in the EnKF with the coupled model showed dependency on oceanic vertical mixing for near-surface atmospheric variables due to the difference of variability between the atmosphere and the ocean as well as the influence of SST variations on the atmospheric boundary layer. The EnKF with the coupled model reproduced the intensity change of Typhoon Halong (2014) during the mature phase more realistically than with an uncoupled atmosphere model, although there remained a degradation of the SST estimate, particularly around the Kuroshio region. This suggests that an atmosphere–ocean coupled data assimilation system should be developed that is able to physically control both atmospheric and oceanic variables.
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Touch, Joe, Yinwen Cao, Morteza Ziyadi, Ahmed Almaiman, Amirhossein Mohajerin-Ariaei, and Alan E. Willner. "Digital optical processing of optical communications: towards an Optical Turing Machine." Nanophotonics 6, no. 3 (January 24, 2017): 507–30. http://dx.doi.org/10.1515/nanoph-2016-0145.
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AbstractOptical computing is needed to support Tb/s in-network processing in a way that unifies communication and computation using a single data representation that supports in-transit network packet processing, security, and big data filtering. Support for optical computation of this sort requires leveraging the native properties of optical wave mixing to enable computation and switching for programmability. As a consequence, data must be encoded digitally as phase (M-PSK), semantics-preserving regeneration is the key to high-order computation, and data processing at Tb/s rates requires mixing. Experiments have demonstrated viable approaches to phase squeezing and power restoration. This work led our team to develop the first serial, optical Internet hop-count decrement, and to design and simulate optical circuits for calculating the Internet checksum and multiplexing Internet packets. The current exploration focuses on limited-lookback computational models to reduce the need for permanent storage and hybrid nanophotonic circuits that combine phase-aligned comb sources, non-linear mixing, and switching on the same substrate to avoid the macroscopic effects that hamper benchtop prototypes.
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Akimoto, Hajime, Tatsuya Nagashima, Natsumi Kawano, Li Jie, Joshua S. Fu, and Zifa Wang. "Discrepancies between MICS-Asia III simulation and observation for surface ozone in the marine atmosphere over the northwestern Pacific Asian Rim region." Atmospheric Chemistry and Physics 20, no. 23 (December 4, 2020): 15003–14. http://dx.doi.org/10.5194/acp-20-15003-2020.
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Abstract. In order to identify the causes of overestimate of the surface-level O3 mixing ratio simulated by three regional chemical-transport models, NAQPMS v.3 (abbreviated as NAQM in this paper), CMAQ v.5.0.2, and CMAQ v.4.7.1, compared to the EANET observational data at a marine remote site at Oki in July 2010, analyses of hourly O3 mixing ratios and net ozone production were made in the context of MICS-Asia III. In addition to Oki, model-simulated and observational data for two other EANET marine sites, Hedo and Ogasawara, were also examined. Three factors, i.e., long-range transport from the continent, in situ photochemical formation, and dry deposition of O3 on seawater, have been identified as contributing to the overestimate by these regional models at Oki. The calculated O3 mixing ratios during long-range transport from the continent were much higher for all three models than those of the observation. In situ photochemical formation, demonstrated by a distinct diurnal variation which was not discerned in the observational data, was seen in the simulated data of all three models and ascribed to the virtual transport of NOx from the southern urban areas of the main island of Japan. The overestimate of the O3 mixing ratio in the background oceanic air mass has been discussed referring to dry deposition velocity (Vd) of O3 over oceanic water. Sensitivity analysis of the dry deposition velocity to the concentration of O3 was made for Oki in July. An increase in Vd from 0.0005 to 0.001 cm s−1 used in the standard runs for CMAQ by a factor of 10 decreases the O3 mixing ratio by more than 20 ppbv on an event basis in certain periods of time and by ca. 4.9 ppbv as a monthly mean in July. The dry deposition velocity of O3 in Bohai Bay and the Yellow Sea has been assumed to be comparable to that of the open ocean in all three models, which could have resulted in the overestimate of O3 mixing ratios in this area and also in the long-range transport of O3 from the continent to Oki. A higher value of dry deposition velocity in this marine area is expected considering the higher content of organics in the surface sea layer brought by rivers and atmospheric wet deposition. Empirical measurements of the mixing ratios and dry deposition flux of O3 in this area are highly recommended, since they would affect the simulated mixing ratios in the downwind region in the Pacific Rim region.
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Gong, Yi, Haibin Song, Zhongxiang Zhao, Yongxian Guan, Kun Zhang, Yunyan Kuang, and Wenhao Fan. "Enhanced diapycnal mixing with polarity-reversing internal solitary waves revealed by seismic reflection data." Nonlinear Processes in Geophysics 28, no. 3 (September 14, 2021): 445–65. http://dx.doi.org/10.5194/npg-28-445-2021.
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Abstract. Shoaling internal solitary waves near the Dongsha Atoll in the South China Sea dissipate their energy and enhance diapycnal mixing, which have an important impact on the oceanic environment and primary productivity. The enhanced diapycnal mixing is patchy and instantaneous. Evaluating its spatiotemporal distribution requires comprehensive observation data. Fortunately, seismic oceanography meets the requirements, thanks to its high spatial resolution and large spatial coverage. In this paper, we studied three internal solitary waves in reversing polarity near the Dongsha Atoll and calculated their spatial distribution of diapycnal diffusivity. Our results show that the average diffusivities along three survey lines are 2 orders of magnitude larger than the open-ocean value. The average diffusivity in internal solitary waves with reversing polarity is 3 times that of the non-polarity reversal region. The diapycnal diffusivity is higher at the front of one internal solitary wave and gradually decreases from shallow to deep water in the vertical direction. Our results also indicate that (1) the enhanced diapycnal diffusivity is related to reflection seismic events, (2) convective instability and shear instability may both contribute to the enhanced diapycnal mixing in the polarity-reversing process, and (3) the difference between our results and Richardson-number-dependent turbulence parameterizations is about 2–3 orders of magnitude, but its vertical distribution is almost the same.
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Yamamoto, M., T. Ohigashi, K. Tsuboki, and N. Hirose. "Cloud-resolving simulation of heavy snowfalls in Japan for late December 2005: application of ocean data assimilation to a snow disaster." Natural Hazards and Earth System Sciences 11, no. 9 (September 26, 2011): 2555–65. http://dx.doi.org/10.5194/nhess-11-2555-2011.
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Abstract. We applied eddy-resolving ocean data assimilation to a cloud-resolving atmospheric simulation of a snow disaster and investigated the effects of mesoscale eddies on a heavy snowfall event in late December 2005. Ocean circulation model (OCM) data assimilation reproduces mesoscale sea surface temperature (SST) structures, which are smoothed out by optimum interpolation. This difference between OCM-assimilation and optimum-interpolation SSTs affects the atmospheric boundary layers over oceanic mesoscale eddies. The atmospheric response to the SST difference is complex at the cold tongue in the central Sea of Japan. Although the horizontal wind and turbulent mixing are quickly and locally affected by the low SST, the atmospheric temperature and water amounts are greatly affected by the upstream high SST via the northwesterly advection. In the heavy snowfall areas, the OCM assimilation greatly affects 10-day accumulated precipitation, though it does not largely influence 10-day mean vertical structures of wind, temperature and water vapor. Thus, we should recognize the significance of oceanic mesoscale eddies for heavy snowfall.
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Kompalli, Sobhan Kumar, Surendran Nair Suresh Babu, Krishnaswamy Krishna Moorthy, Sreedharan Krishnakumari Satheesh, Mukunda Madhab Gogoi, Vijayakumar S. Nair, Venugopalan Nair Jayachandran, Dantong Liu, Michael J. Flynn, and Hugh Coe. "Mixing state of refractory black carbon aerosol in the South Asian outflow over the northern Indian Ocean during winter." Atmospheric Chemistry and Physics 21, no. 11 (June 16, 2021): 9173–99. http://dx.doi.org/10.5194/acp-21-9173-2021.
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Abstract. Regional climatic implications of aerosol black carbon (BC), which has a wide variety of anthropogenic sources in large abundance, are well recognized over South Asia. Significant uncertainties remain in its quantification due to a lack of sufficient information on the microphysical properties (its concentration, size, and mixing state with other aerosol components) that determine the absorption potential of BC. In particular, the information on the mixing state of BC is extremely sparse over this region. In this study, the first observations of the size distribution and mixing state of individual refractory black carbon (rBC) particles in the South Asian outflow to the south-eastern Arabian Sea and the northern and equatorial Indian Ocean regions are presented based on measurements using a single particle soot photometer (SP2) aboard the Integrated Campaign for Aerosols, gases, and Radiation Budget (ICARB-2018) ship during winter 2018 (16 January to 13 February). The results revealed significant spatial heterogeneity of BC characteristics. The highest rBC mass concentrations (∼938±293 ng m−3) with the highest relative coating thickness (RCT; the ratio of BC core to its coating diameters) of ∼2.16±0.19 are found over the south-east Arabian Sea (SEAS) region, which is in the proximity of the continental outflow. As we move to farther oceanic regions, though the mass concentrations decreased by nearly half (∼546±80 ng m−3), BC still remained thickly coated (RCT∼2.05±0.07). The air over the remote equatorial Indian Ocean, which received considerable marine air masses compared to the other regions, showed the lowest rBC mass concentrations (∼206±114 ng m−3) with a moderately thick coating (RCT∼1.73±0.16). Even over oceanic regions far from the landmass, regions that received the outflow from the more industrialized east coast/the Bay of Bengal had a thicker coating (∼104 nm) compared to regions that received outflow from the west coast and/or peninsular India (∼86 nm). Although different regions of the ocean depicted contrasting concentrations and mixing state parameters due to the varied extent and nature of the continental outflow as well as the atmospheric lifetime of air masses, the modal parameters of rBC mass–size distributions (mean mass median diameters ∼ 0.19–0.20 µm) were similar over all regions. The mean fraction of BC-containing particles (FBC) varied in the range of 0.08–0.12 (suggesting significant amounts of non-BC particles), whereas the bulk mixing ratio of coating mass to rBC mass was highest (8.31±2.40) over the outflow regions compared to the remote ocean (4.24±1.45), highlighting the role of outflow in providing condensable material for coatings on rBC. These parameters, along with the information on the size-resolved mixing state of BC cores, throw light on the role of sources and secondary processing of their complex mixtures for coatings on BC under highly polluted conditions. Examination of the non-refractory sub-micrometre aerosol chemical composition obtained using the aerosol chemical speciation monitor (ACSM) suggested that the overall aerosol system was sulfate-dominated over the far-oceanic regions. In contrast, organics were equally prominent adjacent to the coastal landmass. An association between the BC mixing state and aerosol chemical composition suggested that sulfate was the probable dominant coating material on rBC cores.
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Mashayek, A., C. P. Caulfield, and W. R. Peltier. "Role of overturns in optimal mixing in stratified mixing layers." Journal of Fluid Mechanics 826 (August 8, 2017): 522–52. http://dx.doi.org/10.1017/jfm.2017.374.
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Turbulent mixing plays a major role in enabling the large-scale ocean circulation. The accuracy of mixing rates estimated from observations depends on our understanding of basic fluid mechanical processes underlying the nature of turbulence in a stratified fluid. Several of the key assumptions made in conventional mixing parameterizations have been increasingly scrutinized in recent years, primarily on the basis of adequately high resolution numerical simulations. We add to this evidence by compiling results from a suite of numerical simulations of the turbulence generated through stratified shear instability processes. We study the inherently intermittent and time-dependent nature of wave-induced turbulent life cycles and more specifically the tight coupling between inherently anisotropic scales upon which small-scale isotropic turbulence grows. The anisotropic scales stir and stretch fluid filaments enhancing irreversible diffusive mixing at smaller scales. We show that the characteristics of turbulent mixing depend on the relative time evolution of the Ozmidov length scale $L_{O}$ compared to the so-called Thorpe overturning scale $L_{T}$ which represents the scale containing available potential energy upon which turbulence feeds and grows. We find that when $L_{T}\sim L_{O}$, the mixing is most active and efficient since stirring by the largest overturns becomes ‘optimal’ in the sense that it is not suppressed by ambient stratification. We argue that the high mixing efficiency associated with this phase, along with observations of $L_{O}/L_{T}\sim 1$ in oceanic turbulent patches, together point to the potential for systematically underestimating mixing in the ocean if the role of overturns is neglected. This neglect, arising through the assumption of a clear separation of scales between the background mean flow and small-scale quasi-isotropic turbulence, leads to the exclusion of an highly efficient mixing phase from conventional parameterizations of the vertical transport of density. Such an exclusion may well be significant if the mechanism of shear-induced turbulence is assumed to be representative of at least some turbulent events in the ocean. While our results are based upon simulations of shear instability, we show that they are potentially more generic by making direct comparisons with $L_{T}-L_{O}$ data from ocean and lake observations which represent a much wider range of turbulence-inducing physical processes.
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Tegtmeier, S., K. Krüger, B. Quack, E. Atlas, D. R. Blake, H. Boenisch, A. Engel, et al. "The contribution of oceanic methyl iodide to stratospheric iodine." Atmospheric Chemistry and Physics Discussions 13, no. 4 (April 30, 2013): 11427–71. http://dx.doi.org/10.5194/acpd-13-11427-2013.
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Abstract. We investigate the contribution of oceanic methyl iodide (CH3I) to the stratospheric iodine budget. Based on CH3I measurements during three tropical ship campaigns and the Lagrangian transport model FLEXPART we provide a detailed analysis of CH3I transport from the ocean surface to the cold point in the upper tropical tropopause layer (TTL). While average oceanic emissions differ by less than 50% from campaign to campaign, the measurements show much stronger variations within each campaign. A positive correlation between the oceanic CH3I emissions and the efficiency of CH3I troposphere–stratosphere transport has been identified for some cruise sections. The mechanism of strong horizontal surface winds triggering large emissions on the one hand and being associated with tropical convective systems, such as developing typhoons, on the other hand, could explain the identified correlations. As a result of the simultaneous occurrence of large CH3I emissions and strong vertical uplift, localized maximum mixing ratios of 0.6 ppt CH3I at the cold point have been determined for observed peak emissions during the SHIVA-Sonne campaign in the coastal West Pacific. The other two campaigns give considerable smaller maxima of 0.1 ppt CH3I for the TransBrom campaign in the open West Pacific and 0.03 ppt for emissions from the coastal East Atlantic during the DRIVE campaign. In order to assess the representativeness of the large local mixing ratios we use climatological emission scenarios to derive global upper air estimates of CH3I abundances. The model results are compared to available upper air measurements including data from the recent ATTREX and HIPPO2 aircraft campaigns. In the East Pacific region, the location of the available measurement campaigns in the upper TTL, the comparisons give a good agreement indicating that around 0.01 to 0.02 ppt of CH3I enter the stratosphere. However, other tropical regions, which are subject to stronger convective activity show larger CH3I entrainment, e.g., 0.08 ppt in the West Pacific. The strong variations in the geographical distribution of CH3I entrainment suggest that currently available upper air measurements are not representative of global estimates and further campaigns will be necessary in order to better understand the CH3I contribution to stratospheric iodine.
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Tegtmeier, S., K. Krüger, B. Quack, E. Atlas, D. R. Blake, H. Boenisch, A. Engel, et al. "The contribution of oceanic methyl iodide to stratospheric iodine." Atmospheric Chemistry and Physics 13, no. 23 (December 9, 2013): 11869–86. http://dx.doi.org/10.5194/acp-13-11869-2013.
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Abstract. We investigate the contribution of oceanic methyl iodide (CH3I) to the stratospheric iodine budget. Based on CH3I measurements from three tropical ship campaigns and the Lagrangian transport model FLEXPART, we provide a detailed analysis of CH3I transport from the ocean surface to the cold point in the upper tropical tropopause layer (TTL). While average oceanic emissions differ by less than 50% from campaign to campaign, the measurements show much stronger variations within each campaign. A positive correlation between the oceanic CH3I emissions and the efficiency of CH3I troposphere–stratosphere transport has been identified for some cruise sections. The mechanism of strong horizontal surface winds triggering large emissions on the one hand and being associated with tropical convective systems, such as developing typhoons, on the other hand, could explain the identified correlations. As a result of the simultaneous occurrence of large CH3I emissions and strong vertical uplift, localized maximum mixing ratios of 0.6 ppt CH3I at the cold point have been determined for observed peak emissions during the SHIVA (Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere)-Sonne research vessel campaign in the coastal western Pacific. The other two campaigns give considerably smaller maxima of 0.1 ppt CH3I in the open western Pacific and 0.03 ppt in the coastal eastern Atlantic. In order to assess the representativeness of the large local mixing ratios, we use climatological emission scenarios to derive global upper air estimates of CH3I abundances. The model results are compared with available upper air measurements, including data from the recent ATTREX and HIPPO2 aircraft campaigns. In the eastern Pacific region, the location of the available measurement campaigns in the upper TTL, the comparisons give a good agreement, indicating that around 0.01 to 0.02 ppt of CH3I enter the stratosphere. However, other tropical regions that are subject to stronger convective activity show larger CH3I entrainment, e.g., 0.08 ppt in the western Pacific. Overall our model results give a tropical contribution of 0.04 ppt CH3I to the stratospheric iodine budget. The strong variations in the geographical distribution of CH3I entrainment suggest that currently available upper air measurements are not representative of global estimates and further campaigns will be necessary in order to better understand the CH3I contribution to stratospheric iodine.
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Turiel, Antonio, Jordi Isern-Fontanet, and Emilio García-Ladona. "Wavelet Filtering to Extract Coherent Vortices from Altimetric Data." Journal of Atmospheric and Oceanic Technology 24, no. 12 (December 1, 2007): 2103–19. http://dx.doi.org/10.1175/2007jtecho434.1.
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Abstract Because of the optimal features of wavelet processing, the use of wavelets for describing and analyzing signals in 2D turbulence has been generalized since a decade ago. In spite of the close analogy between 2D turbulence and geophysical fluid dynamics, few works have tried to generalize the rich framework of wavelet techniques to the study of experimental signals in oceanography. In this paper, the authors extend a prominent wavelet technique designed for the study of direct numerical simulations (DNSs) on 2D turbulence, the coherent vortex simulation, and analyze with it ocean velocity fields obtained from sea surface height maps derived from satellite altimetry. The authors demonstrate the pertinence of this technique to describe altimetry data, resulting in a description of oceanic flows with a reduced number of degrees of freedom. In particular, it is shown that the western Mediterranean circulation is well approximated by a field of extracted coherent vortices when an appropriate wavelet basis is employed as a filter; however, about one-third of the energy is lost in this description, evidencing important differences between results obtained on the frame of 2D turbulence and oceanic data.
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Williams, J. E., G. Le Bras, A. Kukui, H. Ziereis, and C. A. M. Brenninkmeijer. "The impact of the chemical production of methyl nitrate from the NO + CH<sub>3</sub>O<sub>2</sub> reaction on the global distributions of alkyl nitrates, nitrogen oxides and tropospheric ozone: a global modelling study." Atmospheric Chemistry and Physics 14, no. 5 (March 7, 2014): 2363–82. http://dx.doi.org/10.5194/acp-14-2363-2014.
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Abstract. The formation, abundance and distribution of organic nitrates are relevant for determining the production efficiency and resident mixing ratios of tropospheric ozone (O3) on both regional and global scales. Here we investigate the effect of applying the recently measured direct chemical production of methyl nitrate (CH3ONO2) during NOx recycling involving the methyl-peroxy radical on the global tropospheric distribution of CH3ONO2 and the perturbations introduced towards tropospheric NOx and O3 using the TM5 global chemistry transport model. By comparisons against numerous observations, we show that the global surface distribution of CH3ONO2 can be largely explained by introducing the chemical production mechanism using a branching ratio of 0.3%, when assuming a direct oceanic emission source of ~0.15 Tg N yr−1. On a global scale, the chemical production of CH3ONO2 converts 1 Tg N yr−1 from nitrogen oxide for this branching ratio. The resident mixing ratios of CH3ONO2 are found to be highly sensitive to the dry deposition velocity that is prescribed, where more than 50% of the direct oceanic emission is lost near the source regions, thereby mitigating the subsequent effects due to long-range and convective transport out of the source region. For the higher alkyl nitrates (RONO2) we find improvements in the simulated distribution near the surface in the tropics (10° S–10° N) when introducing direct oceanic emissions equal to ~0.17 Tg N yr−1 . In terms of the vertical profile of CH3ONO2, there are persistent overestimations in the free troposphere and underestimations in the upper troposphere across a wide range of latitudes and longitudes when compared against data from measurement campaigns. This suggests either a missing transport pathway or source/sink term, although measurements show significant variability in resident mixing ratios at high altitudes at global scale. For the vertical profile of RONO2, TM5 performs better at tropical latitudes than at mid-latitudes, with similar features in the comparisons to those for CH3ONO2. Comparisons of CH3ONO2 with a wide range of surface measurements shows that further constraints are necessary regarding the variability in the deposition terms for different land surfaces in order to improve on the comparisons presented here. For total reactive nitrogen (NOy) ~20% originates from alkyl nitrates in the tropics and subtropics, where the introduction of both direct oceanic emissions and the chemical formation mechanism of CH3ONO2 only makes a ~5% contribution to the total alkyl nitrate content in the upper troposphere when compared with aircraft observations. We find that the increases in tropospheric O3 that occur due oxidation of CH3ONO2 originating from direct oceanic emission is negated when accounting for the chemical formation of CH3ONO2, meaning that the impact of such oceanic emissions on atmospheric lifetimes becomes marginal when a branching ratio of 0.3% is adopted.
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Lanotte, A. S., R. Corrado, L. Palatella, C. Pizzigalli, I. Schipa, and R. Santoleri. "Effects of vertical shear in modelling horizontal oceanic dispersion." Ocean Science 12, no. 1 (February 3, 2016): 207–16. http://dx.doi.org/10.5194/os-12-207-2016.
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Abstract. The effect of vertical shear on the horizontal dispersion properties of passive tracer particles on the continental shelf of the South Mediterranean is investigated by means of observation and model data. In situ current measurements reveal that vertical gradients of horizontal velocities in the upper mixing layer decorrelate quite fast ( ∼ 1 day), whereas an eddy-permitting ocean model, such as the Mediterranean Forecasting System, tends to overestimate such decorrelation time because of finite resolution effects. Horizontal dispersion, simulated by the Mediterranean sea Forecasting System, is mostly affected by: (1) unresolved scale motions, and mesoscale motions that are largely smoothed out at scales close to the grid spacing; (2) poorly resolved time variability in the profiles of the horizontal velocities in the upper layer. For the case study we have analysed, we show that a suitable use of deterministic kinematic parametrizations is helpful to implement realistic statistical features of tracer dispersion in two and three dimensions. The approach here suggested provides a functional tool to control the horizontal spreading of small organisms or substance concentrations, and is thus relevant for marine biology, pollutant dispersion as well as oil spill applications.
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Jaimes, Benjamin, and Lynn K. Shay. "Mixed Layer Cooling in Mesoscale Oceanic Eddies during Hurricanes Katrina and Rita." Monthly Weather Review 137, no. 12 (December 1, 2009): 4188–207. http://dx.doi.org/10.1175/2009mwr2849.1.
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Abstract During favorable atmospheric conditions, Hurricanes Katrina and Rita deepened to category 5 over the Loop Current’s (LC) bulge associated with an amplifying warm core eddy. Both hurricanes subsequently weakened to category 3 after passing over a cold core eddy (CCE) prior to making landfall. Reduced (increased) oceanic mixed layer (OML) cooling of ∼1°C (4.5°C) was observed over the LC (CCE) where the storms rapidly deepened (weakened). Data acquired during and subsequent to the passage of both hurricanes indicate that the modulated velocity response in these geostrophic features was responsible for the contrasts in the upper-ocean cooling levels. For similar wind forcing, the OML velocity response was about 2 times larger inside the CCE that interacted with Katrina than in the LC region affected by Rita, depending on the prestorm OML thickness. Hurricane-induced upwelling and vertical mixing were increased (reduced) in the CCE (LC). Less wind-driven kinetic energy was available to increase vertical shears for entrainment cooling in the LC, as the OML current response was weaker and energy was largely radiated into the thermocline. Estimates of downward vertical radiation of near-inertial wave energies were significantly stronger in the LC (12.1 × 10−2 W m−2) than in the CCE (1.8 × 10−2 W m−2). Katrina and Rita winds provided O(1010) W to the global internal wave power. The vertical mixing induced by both storms was confined to the surface water mass. From a broader perspective, models must capture oceanic features to reproduce the differentiated hurricane-induced OML cooling to improve hurricane intensity forecasting.
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Nakaoka, S., M. Telszewski, Y. Nojiri, S. Yasunaka, C. Miyazaki, H. Mukai, and N. Usui. "Estimating temporal and spatial variation of ocean surface <i>p</i>CO<sub>2</sub> in the North Pacific using a Self Organizing Map neural network technique." Biogeosciences Discussions 10, no. 3 (March 8, 2013): 4575–610. http://dx.doi.org/10.5194/bgd-10-4575-2013.
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Abstract. This study produced maps of the partial pressure of oceanic carbon dioxide (pCO2sea) in the North Pacific on a 0.25° latitude × 0.25° longitude grid from 2002 to 2008. The pCO2sea values were estimated by using a self-organizing map neural network technique to explain the non-linear relationships between observed pCO2sea data and four oceanic parameters: sea surface temperature (SST), mixed layer depth, chlorophyll a concentration, and sea surface salinity (SSS). The observed pCO2sea data was obtained from an extensive dataset generated by the volunteer observation ship program operated by the National Institute for Environmental Studies. The reconstructed pCO2sea values agreed rather well with the pCO2sea measurements, the root mean square error being 17.6 μatm. The pCO2sea estimates were improved by including SSS as one of the training parameters and by taking into account secular increases of pCO2sea that have tracked increases in atmospheric CO2. Estimated pCO2sea values accurately reproduced pCO2sea data at several stations in the North Pacific. The distributions of pCO2sea revealed by seven-year averaged monthly pCO2sea maps were similar to Lamont-Doherty Earth Observatory pCO2sea climatology and more precisely reflected oceanic conditions. The distributions of pCO2sea anomalies over the North Pacific during the winter clearly showed regional contrasts between El Niño and La Niña years related to changes of SST and vertical mixing.
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Drillet, Y., J. M. Lellouche, B. Levier, M. Drévillon, O. Le Galloudec, G. Reffray, C. Regnier, E. Greiner, and M. Clavier. "Forecasting the mixed layer depth in the north east Atlantic: an ensemble approach, with uncertainties based on data from operational oceanic systems." Ocean Science Discussions 11, no. 3 (June 11, 2014): 1435–72. http://dx.doi.org/10.5194/osd-11-1435-2014.
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Abstract. Operational systems operated by Mercator Océan provide daily ocean forecasts, and combining these forecasts we can produce ensemble forecast and uncertainty estimates. This study focuses on the mixed layer depth in the North East Atlantic near the Porcupine Abyssal Plain for May 2013. This period is of interest for several reasons: (1) four Mercator Océan operational systems provide daily forecasts at a horizontal resolution of 1/4°, 1/12° and 1/36° with different physics; (2) glider deployment under the OSMOSIS project provides observation of the changes in mixed layer depth; (3) the ocean stratifies in May, but mixing events induced by gale force wind are observed and forecasted by the systems. A statistical approach and forecast error quantification for each system and for the combined products are presented. Skill scores indicate that forecasts are in any case better than persistence, and temporal correlations between forecast and observations are greater than 0.8 even for the 4 day forecast. The impact of atmospheric forecast error, and for the wind field in particular, is also quantified in terms of the forecast time delay and the intensity of mixing or stratification events.
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LAPIERRE, H., D. BOSCH, A. NARROS, G. H. MASCLE, M. TARDY, and A. DEMANT. "The Mamonia Complex (SW Cyprus) revisited: remnant of Late Triassic intra-oceanic volcanism along the Tethyan southwestern passive margin." Geological Magazine 144, no. 1 (December 21, 2006): 1–19. http://dx.doi.org/10.1017/s0016756806002937.
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Upper Triassic volcanic and sedimentary rocks of the Mamonia Complex in southwestern Cyprus are exposed in erosional windows through the post-Cretaceous cover, where the Mamonia Complex is tectonically imbricated with the Troodos and Akamas ophiolitic suites. Most of these Upper Triassic volcanic rocks have been considered to represent remnants of Triassic oceanic crust and its associated seamounts. New Nd and Pb isotopic data show that the whole Mamonia volcanic suite exhibits features of oceanic island basalts (OIB). Four rock types have been distinguished on the basis of the petrology and chemistry of the rocks. Volcanism began with the eruption of depleted olivine tholeiites (Type 1) and oceanic island tholeiites (Type 2) associated with deep basin siliceous and/or calcareous sediments. The tholeiites were followed by highly phyric alkali basalts (Type 3) interbedded with pelagic Halobia-bearing limestones or white reefal limestones. Strongly LREE-enriched trachytes (Type 4) were emplaced during the final stage of volcanic activity. Nd and Pb isotopic ratios suggest that tholeiites and mildly alkali basalts derived from partial melting of heterogeneous enriched mantle sources. Fractional crystallization alone cannot account for the derivation of trachytes from alkaline basalts. The trachytes could have been derived from the partial melting at depth of mafic material which shares with the alkali basalts similar trace element and isotopic compositions. This is corroborated by the rather similar isotopic compositions of the alkali basalts and trachytes. The correlations observed between incompatible elements (Nb, Th) and εNd and Pb isotopic initial ratios suggest that the Mamonia suite was derived from the mixing of a depleted mantle (DMM) and an enriched component of High μ (μ = 238U/204Pb, HIMU) type. Models using both Nd and Pb isotopic initial ratios suggest that the depleted tholeiites (Type 1) derived from a DMM source contaminated by an Enriched Mantle Type 2 component (EM2), and that the oceanic tholeiites (Type 2), alkali basalts (Type 3) and trachytes (Type 4) were derived from the mixing of the enriched mantle source of the depleted tholeiites with a HIMU component. None of the Mamonia volcanic rocks show evidence of crustal contamination. The Upper Triassic within-plate volcanism likely erupted in a small southerly Neotethyan basin, located north of the Eratosthenes seamount and likely floored by oceanic crust.
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López, Rubén R., Luz-María Sánchez, Anas Alazzam, Julia V. Burnier, Ion Stiharu, and Vahé Nerguizian. "Numerical and Experimental Validation of Mixing Efficiency in Periodic Disturbance Mixers." Micromachines 12, no. 9 (September 14, 2021): 1102. http://dx.doi.org/10.3390/mi12091102.
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The shape and dimensions of a micromixer are key elements in the mixing process. Accurately quantifying the mixing efficiency enables the evaluation of the performance of a micromixer and the selection of the most suitable one for specific applications. In this paper, two methods are investigated to evaluate the mixing efficiency: a numerical model and an experimental model with a software image processing technique. Using two methods to calculate the mixing efficiency, in addition to corroborating the results and increasing their reliability, creates various possible approaches that can be selected depending on the circumstances, resources, amount of data to be processed and processing time. Image processing is an easy-to-implement tool, is applicable to different programming languages, is flexible, and provides a quick response that allows the calculation of the mixing efficiency using a process of filtering of images and quantifying the intensity of the color, which is associated with the percentage of mixing. The results showed high similarity between the two methods, with a difference ranging between 0 and 6% in all the evaluated points.
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Dumousseaud, C., E. P. Achterberg, T. Tyrrell, A. Charalampopoulou, U. Schuster, M. Hartman, and D. J. Hydes. "Contrasting effects of temperature and winter mixing on the seasonal and inter-annual variability of the carbonate system in the Northeast Atlantic Ocean." Biogeosciences 7, no. 5 (May 11, 2010): 1481–92. http://dx.doi.org/10.5194/bg-7-1481-2010.
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Abstract. Future climate change as a result of increasing atmospheric CO2 concentrations is expected to strongly affect the oceans, with shallower winter mixing and consequent reduction in primary production and oceanic carbon drawdown in low and mid-latitudinal oceanic regions. Here we test this hypothesis by examining the effects of cold and warm winters on the carbonate system in the surface waters of the Northeast Atlantic Ocean for the period between 2005 and 2007. Monthly observations were made between the English Channel and the Bay of Biscay using a ship of opportunity program. During the colder winter of 2005/2006, the maximum depth of the mixed layer reached up to 650 m in the Bay of Biscay, whilst during the warmer (by 2.6 ± 0.5 °C) winter of 2006/2007 the mixed layer depth reached only 300 m. The inter-annual differences in late winter concentrations of nitrate (2.8 ± 1.1 μmol l−1) and dissolved inorganic carbon (22 ± 6 μmol kg−1, with higher concentrations at the end of the colder winter (2005/2006), led to differences in the dissolved oxygen anomaly and the chlorophyll α-fluorescence data for the subsequent growing season. In contrast to model predictions, the calculated air-sea CO2 fluxes (ranging from +3.7 to −4.8 mmol m−2 d−1) showed an increased oceanic CO2 uptake in the Bay of Biscay following the warmer winter of 2006/2007 associated with wind speed and sea surface temperature differences.
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Dumousseaud, C., E. P. Achterberg, T. Tyrrell, A. Charalampopoulou, U. Schuster, M. Hartman, and D. J. Hydes. "Contrasting effects of temperature and winter mixing on the seasonal and inter-annual variability of the carbonate system in the Northeast Atlantic Ocean." Biogeosciences Discussions 6, no. 5 (October 8, 2009): 9701–35. http://dx.doi.org/10.5194/bgd-6-9701-2009.
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Abstract. Future climate change due to the increase in atmospheric CO2 concentrations is expected to strongly affect the oceans, with shallower winter mixing and consequent reduction in primary productivity and oceanic carbon drawdown in low and mid-latitudinal oceanic regions. Here we test this hypothesis by examining the effects of cold and warm winters on the carbonate system in the surface waters of the Northeast Atlantic Ocean for the period between 2005 and 2007. Monthly observations were made between the English Channel and the Bay of Biscay using a ship of opportunity program. During the colder winter of 2005/2006, the maximum depth of the mixed layer reached 500 m in the Bay of Biscay, whilst during the warmer (by 2.6±0.5°C) winter of 2006/2007 the mixed layer depth reached only 300 m. The inter-annual differences in late winter concentrations of nitrate (2.8±1.1 μmol l−1) and dissolved inorganic carbon (22±6 μmol l−1), with higher concentrations at the end of the colder winter (2005/2006), led to differences in the dissolved oxygen anomaly and the fluorescence data for the subsequent growing season. In contrast to model predictions, the calculated air-sea CO2 fluxes (ranging from +4.5 to −5.5 mmol m−2 d−1) showed an increased oceanic CO2 uptake in the Bay of Biscay following the warmer winter of 2006/2007 associated with wind speed and sea surface temperature differences.
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Leredde, Y., J. L. Devenon, and I. Dekeyser. "Turbulent viscosity optimized by data assimilation." Annales Geophysicae 17, no. 11 (November 30, 1999): 1463–77. http://dx.doi.org/10.1007/s00585-999-1463-9.
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Abstract. As an alternative approach to classical turbulence modelling using a first or second order closure, the data assimilation method of optimal control is applied to estimate a time and space-dependent turbulent viscosity in a three-dimensional oceanic circulation model. The optimal control method, described for a 3-D primitive equation model, involves the minimization of a cost function that quantifies the discrepancies between the simulations and the observations. An iterative algorithm is obtained via the adjoint model resolution. In a first experiment, a k + L model is used to simulate the one-dimensional development of inertial oscillations resulting from a wind stress at the sea surface and with the presence of a halocline. These results are used as synthetic observations to be assimilated. The turbulent viscosity is then recovered without the k + L closure, even with sparse and noisy observations. The problems of controllability and of the dimensions of the control are then discussed. A second experiment consists of a two-dimensional schematic simulation. A 2-D turbulent viscosity field is estimated from data on the initial and final states of a coastal upwelling event.Key words. Oceanography: general (numerical modelling) · Oceanography: physical (turbulence · diffusion · and mixing processes)
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Jakovlev, A. R., and S. P. Smyshlyaev. "Influence of ocean on dynamic of polar stratosphere and ozone layer." Известия Российской академии наук. Физика атмосферы и океана 55, no. 1 (April 16, 2019): 98–113. http://dx.doi.org/10.31857/s0002-351555198-113.
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Influence of the tropical oceanic processes (the El-Niño – La-Niña phenomenon) on structure and composition of a polar stratosphere is considered. Data of the reanalysis on sea surface temperature, a potential vorticity, temperatures of air, ozone mixing ratio and total ozone column per 1980–2016 are analyzed. Influence the El-Niño and La-Niña on circumpolar vorticity, temperature of air in a stratosphere and an ozone layer is studied. It is shown that the El-Niño leads to instability of circumpolar vorticity, causes sudden stratospheric warming and increase the content of ozone.
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Wang, C. G., Q. H. Sun, Z. M. Wang, and Y. J. Qi. "Design of Control and Monitor System of Foam Cement Mixing Device Based on PLC and MCGS." Advanced Materials Research 756-759 (September 2013): 261–64. http://dx.doi.org/10.4028/www.scientific.net/amr.756-759.261.
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Control and monitor system of foamed cement mixing device are designed based on PLC and MCGS(Monitor and Control Generated System) configuration software, it realizes data collection and dynamic monitoring, data processing. Through the control system, it achieves automatic control to foamed cement mixing device. Experiments show the system has advantanges of high precision, reliability and good maintain.
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Zaron, Edward D., and James N. Moum. "A New Look at Richardson Number Mixing Schemes for Equatorial Ocean Modeling." Journal of Physical Oceanography 39, no. 10 (October 1, 2009): 2652–64. http://dx.doi.org/10.1175/2009jpo4133.1.
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Abstract A reexamination of turbulence dissipation measurements from the equatorial Pacific shows that the turbulence diffusivities are not a simple function of the gradient Richardson number. A widely used mixing scheme, the K-profile parameterization, overpredicts the turbulent vertical heat flux by roughly a factor of 4 in the stably stratified region between the surface mixed layer and the Equatorial Undercurrent (EUC). Additionally, the heat flux divergence is of the incorrect sign in the upper 80 m. An alternative class of parameterizations is examined that expresses the mixing coefficients in terms of the large-scale kinetic energy, shear, and Richardson number. These representations collapse the turbulence diffusivities above and below the Equatorial Undercurrent, and a tuned version is able to reproduce the vertical turbulence heat flux within the 50–180-m depth range. Kinetic energy is not Galilean invariant, so the collapse of the data with the new parameterization suggests that oceanic turbulence responds to boundary forcing at depths well below the surface mixed layer.
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McFerren, G., and T. van Zyl. "GEOSPATIAL DATA STREAM PROCESSING IN PYTHON USING FOSS4G COMPONENTS." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B7 (June 22, 2016): 931–37. http://dx.doi.org/10.5194/isprs-archives-xli-b7-931-2016.
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One viewpoint of current and future IT systems holds that there is an increase in the scale and velocity at which data are acquired and analysed from heterogeneous, dynamic sources. In the earth observation and geoinformatics domains, this process is driven by the increase in number and types of devices that report location and the proliferation of assorted sensors, from satellite constellations to oceanic buoy arrays. Much of these data will be encountered as self-contained messages on data streams - continuous, infinite flows of data. Spatial analytics over data streams concerns the search for spatial and spatio-temporal relationships within and amongst data “on the move”. In spatial databases, queries can assess a store of data to unpack spatial relationships; this is not the case on streams, where spatial relationships need to be established with the incomplete data available. Methods for spatially-based indexing, filtering, joining and transforming of streaming data need to be established and implemented in software components. This article describes the usage patterns and performance metrics of a number of well known FOSS4G Python software libraries within the data stream processing paradigm. In particular, we consider the RTree library for spatial indexing, the Shapely library for geometric processing and transformation and the PyProj library for projection and geodesic calculations over streams of geospatial data. We introduce a message oriented Python-based geospatial data streaming framework called Swordfish, which provides data stream processing primitives, functions, transports and a common data model for describing messages, based on the Open Geospatial Consortium Observations and Measurements (O&M) and Unidata Common Data Model (CDM) standards. We illustrate how the geospatial software components are integrated with the Swordfish framework. Furthermore, we describe the tight temporal constraints under which geospatial functionality can be invoked when processing high velocity, potentially infinite geospatial data streams. The article discusses the performance of these libraries under simulated streaming loads (size, complexity and volume of messages) and how they can be deployed and utilised with Swordfish under real load scenarios, illustrated by a set of Vessel Automatic Identification System (AIS) use cases. We conclude that the described software libraries are able to perform adequately under geospatial data stream processing scenarios - many real application use cases will be handled sufficiently by the software.
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Duo, Zijun, Wenke Wang, and Huizan Wang. "Oceanic Mesoscale Eddy Detection Method Based on Deep Learning." Remote Sensing 11, no. 16 (August 17, 2019): 1921. http://dx.doi.org/10.3390/rs11161921.
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Oceanic mesoscale eddies greatly influence energy and matter transport and acoustic propagation. However, the traditional detection method for oceanic mesoscale eddies relies too much on the threshold value and has significant subjectivity. The existing machine learning methods are not mature or purposeful enough, as their train set lacks authority. In view of the above problems, this paper constructs a mesoscale eddy automatic identification and positioning network—OEDNet—based on an object detection network. Firstly, 2D image processing technology is used to enhance the data of a small number of accurate eddy samples annotated by marine experts to generate the train set. Then, the object detection model with a deep residual network, and a feature pyramid network as the main structure, is designed and optimized for small samples and complex regions in the mesoscale eddies of the ocean. Experimental results show that the model achieves better recognition compared to the traditional detection method and exhibits a good generalization ability in different sea areas.
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Spondylidis, Spyros, Konstantinos Topouzelis, Dimitris Kavroudakis, and Michail Vaitis. "Mesoscale Ocean Feature Identification in the North Aegean Sea with the Use of Sentinel-3 Data." Journal of Marine Science and Engineering 8, no. 10 (September 25, 2020): 740. http://dx.doi.org/10.3390/jmse8100740.
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The identification of oceanographic circulation related features is a valuable tool for environmental and fishery management authorities, commercial use and institutional research. Remote sensing techniques are suitable for detection, as in situ measurements are prohibitively costly, spatially sparse and infrequent. Still, these imagery applications require a certain level of technical and theoretical skill making them practically unreachable to the immediate beneficiaries. In this paper a new geospatial web service is proposed for providing daily data on mesoscale oceanic feature identification in the North Aegean Sea, produced by Sentinel-3 SLSTR Sea Surface Temperature (SST) imagery, to end users. The service encompasses an automated process for: raw data acquisition, interpolation, oceanic feature extraction and publishing through a webGIS application. Level-2 SST data are interpolated through a Co-Kriging algorithm, involving information from short term historical data, in order to retain as much information as possible. A modified gradient edge detection methodology is then applied to the interpolated products for the mesoscale feature extraction. The resulting datasets are served according to the Open Geospatial Consortium (OGC) standards and are available for visualization, processing and download though a dedicated web portal.