WorldWideScience

Sample records for boundary upwelling systems

  1. The distribution and impacts of harmful algal bloom species in eastern boundary upwelling systems

    Science.gov (United States)

    Trainer, V. L.; Pitcher, G. C.; Reguera, B.; Smayda, T. J.

    2010-04-01

    Comparison of harmful algal bloom (HAB) species in eastern boundary upwelling systems, specifically species composition, bloom densities, toxin concentrations and impacts are likely to contribute to understanding these phenomena. We identify and describe HABs in the California, Canary, Benguela and Humboldt Current systems, including those that can cause the poisoning syndromes in humans called paralytic shellfish poisoning (PSP), diarrhetic shellfish poisoning (DSP), and amnesic shellfish poisoning (ASP), as well as yessotoxins, ichthyotoxins, and high-biomass blooms resulting in hypoxia and anoxia. Such comparisons will allow identification of parameters, some unique to upwelling systems and others not, that contribute to the development of these harmful blooms.

  2. Surface mixing and biological activity in the four Eastern Boundary Upwelling Systems

    Directory of Open Access Journals (Sweden)

    V. Rossi

    2009-08-01

    Full Text Available Eastern Boundary Upwelling Systems (EBUS are characterized by a high productivity of plankton associated with large commercial fisheries, thus playing key biological and socio-economical roles. Since they are populated by several physical oceanic structures such as filaments and eddies, which interact with the biological processes, it is a major challenge to study this sub- and mesoscale activity in connection with the chlorophyll distribution. The aim of this work is to make a comparative study of these four upwelling systems focussing on their surface stirring, using the Finite Size Lyapunov Exponents (FSLEs, and their biological activity, based on satellite data. First, the spatial distribution of horizontal mixing is analysed from time averages and from probability density functions of FSLEs, which allow us to divide each areas in two different subsystems. Then we studied the temporal variability of surface stirring focussing on the annual and seasonal cycle. We also proposed a ranking of the four EBUS based on the averaged mixing intensity. When investigating the links with chlorophyll concentration, the previous subsystems reveal distinct biological signatures. There is a global negative correlation between surface horizontal mixing and chlorophyll standing stocks over the four areas. To try to better understand this inverse relationship, we consider the vertical dimension by looking at the Ekman-transport and vertical velocities. We suggest the possibility of a changing response of the phytoplankton to sub/mesoscale turbulence, from a negative effect in the very productive coastal areas to a positive one in the open ocean. This study provides new insights for the understanding of the variable biological productivity in the ocean, which results from both dynamics of the marine ecosystem and of the 3-D turbulent medium.

  3. Surface-to-subsurface temperature variations during the last century in a western boundary upwelling system (Southeastern, Brazil)

    Science.gov (United States)

    Venancio, Igor M.; Gomes, Vitor P.; Belem, Andre L.; Albuquerque, Ana Luiza S.

    2016-08-01

    The upper thermal gradient of a western boundary upwelling system was reconstructed for the last 100 years. The reconstruction was based on oxygen isotopic composition (δ18O) of four planktonic foraminifera species derived from two boxcores (BCCF10-01 and BCCF10-04) located in the southeastern Brazilian shelf. Calcification depths of the four planktonic foraminifera species were estimated in order to understand which layer of the water column was assessed. Changes in the upper thermal gradient were evaluated by using the δ18O difference from the surface-dwelling species Globigerinoides ruber (pink) and the deep-dwelling Neogloboquadrina dutertrei. The relative abundance of cold-water species and the δ13C of G. ruber (pink) were also used to evaluate changes on the surface layer. Our results demonstrate a trend to reduction on the temperature difference (∆T) between the surface and the thermocline layer towards the present for both cores, together with an increase on the relative abundance of cold-water species for the mid-shelf core (BCCF10-04) and a decrease in δ13C values of G. ruber (pink) for both cores. Despite the observable trend on the proxies, only the relative abundance of Turborotalita quinqueloba and the δ13C of G. ruber (pink) for the mid-shelf core presented statistically significant trends. These results were related to an increase in South Atlantic Central Water (SACW) intrusions in the sub-surface layer, especially on the middle shelf region. The SACW intrusions would lower the sea surface temperature and would bring a depleted δ13C of the dissolved inorganic carbon signature to the surface, which would be in agreement with our findings. Moreover, these mid-shelf SACW intrusions in the region were attributed to the Ekman pumping (wind stress curl-driven), which was previously reported to be an important mechanism in this upwelling system. The major outcomes to this western boundary current ecosystem from an intensification of the mid

  4. Nitrogen fixation in sediments along a depth transect through the Eastern Boundary Upwelling Systems off Peru and Mauritania

    Science.gov (United States)

    Gier, J.; Sommer, S.; Löscher, C. R.; Dale, A.; Schmitz, R. A.; Treude, T.

    2015-12-01

    The distribution of benthic nitrogen (N2) fixation and its relevance for N cycling in the Eastern Boundary Upwelling Systems (EBUS) are still unknown. Recent studies confirm that benthic N2 fixation can be coupled to sulfate reduction (SR) and that several species of sulfate reducing bacteria have the genetic ability to fix N due to the presence of the gene encoding for the nitrogenase enzyme. We investigated benthic N2 fixation and SR in the Peruvian oxygen minimum zone at 12°S and in the Mauritanian upwelling system at 18°N along a depth transect. Sediments were retrieved by a multicorer and a benthic lander at six stations in both regions. Benthic N2 fixation occurred throughout the sediment in both EBUS. Off Peru the highest integrated (0-20 cm) N2 fixation rate of 0.4 mmol N/m2/d was measured inside the core of the OMZ at 253 m water depth. Off Mauritania the highest integrated (0-20 cm) N2 fixation rate of 0.15 mmol N/m2/d was measured at 90 m, coinciding with a low bottom water oxygen concentration (30 μM). N2 fixation depth profiles often overlapped with SR activity. Moreover, sequencing data yielded insights into the composition and diversity of the nifH gene pool in EBUS sediments. Interestingly, detected sequences in both EBUS clustered with SR bacteria, such as Desulfovibrio vulgaris and several of the novel detected clades belonged to uncultured diazotrophs. Our results suggest that N2 fixation and SR were coupled to a large extent in both regions. However, potential environmental factors controlling benthic diazotrophs in the EBUS appear to be the availability of sulfide and organic matter. Additionally, no inhibition of N2 fixation at high ammonium concentrations was found, which highlights gaps in our knowledge regards the interaction between ammonium availability and diazotrophy. Our results contribute to a better understanding of N cycling in EBUS sediments and sources of fixed N.

  5. An annually-resolved palaeoenvironmental archive for the Eastern Boundary North Atlantic upwelling system: Sclerochronology of Glycymeris glycymeris (Bivalvia) shells from the Iberian shelf

    Science.gov (United States)

    Freitas, Pedro; Monteiro, Carlos; Butler, Paul; Reynolds, David; Richardson, Christopher; Gaspar, Miguel; Scourse, James

    2015-04-01

    The seasonally variable western Iberia upwelling system, albeit placed at a crucial climatic boundary position to record high frequency climate events, lacks well-dated high-resolution records of environmental variability. Bivalve shells provide robust high-resolution archives of oceanographic and climatic variability on timescales of decades to millennia. In particular, the North Atlantic Ocean region has recently seen several noteworthy sclerochronological and geochemical reconstructions based on bivalve shells (mainly Arctica islandica) of high frequency oceanographic and climatic conditions during the last millennium. However, due to the absence of Arctica islandica and similarly long-lived bivalves, sclerochronological palaeoenvironmental studies of southern European coastal shelf seas are scarce. In particular, none of these studies focus on reconstructing the variability of an eastern boundary upwelling system. The relatively long-lived bivalve (>100 years) Glycymeris glycymeris occurs in European and North West African coastal shelf seas and provides a valid annually resolved archive of environmental conditions during growth. Annual growth increment width series from living G. glycymeris shells, collected in 2014 on the western Iberian continental shelf (ca. 35 m water depth), were used to construct a statistically robust, ca. 70-year long absolutely-dated chronology. Sub-annually resolved (11 to 22 samples per year) oxygen stable isotope (δ18Oshell) data covering three years of shell growth, together with the direct evaluation of the time of growth mark deposition in shells collected during the autumn and winter months, were used to constrain the season of growth and to evaluate the seasonal bias of the sea-surface temperature signal preserved in the δ18Oshelldata. The growth increment width and δ18Oshell series, once robustly calibrated against modelled and instrumental oceanographic and climatic series, potentially provide novel insights into the

  6. The role of nutrients in regulation and promotion of harmful algal blooms in upwelling systems

    Science.gov (United States)

    Kudela, R. M.; Seeyave, S.; Cochlan, W. P.

    2010-04-01

    The Core Research Project on HABs in upwelling systems, as a component project of the international scientific programme on the Global Ecology and Oceanography of Harmful Algal Blooms (GEOHAB), promotes a comparative approach within and across systems to understand and predict the ecology, frequency and occurrence of HABs in eastern boundary current upwelling systems. Unlike other systems, upwelling circulation tends to override nutrient limitation caused by stratification, but is less affected by anthropogenic impacts due to the magnitude of the upwelling nutrient signal. At the same time, upwelling systems are unique in that they undergo seasonal succession as well as short-term spatial and temporal oscillations driven by the time-scale of upwelling wind events. An understanding of nutrient dynamics in upwelling systems is thus critical to any attempt to understand or predict HAB events in these environments. We review the state of knowledge regarding nutrient ecophysiology of a subset of HAB organisms identified in upwelling systems. The upwelling HABs exhibit a number of adaptations previously identified in HAB organisms, such as mixotrophy, osmotrophy and vertical migration. We suggest that, unlike most other HABs, these organisms do not necessarily follow a low nutrient-affinity strategy, and do not fit well with classic allometric scaling relationships. Despite these anomalies, progress has been made in predicting HAB events in upwelling systems, by linking HAB events to the unique environmental conditions associated with these systems. We conclude that this subset of HAB organisms is still poorly described in terms of nutrient ecophysiology, and will benefit from a comparative approach across systems, particularly because the subset of upwelling HABs does not necessarily fit the generic patterns identified for HABs generally.

  7. A Model Analysis for the Design and Deployment of an Eulerian Sediment Trap Mooring Array in a Western Boundary Upwelling System from Southeast Brazil

    Directory of Open Access Journals (Sweden)

    URSULA MENDOZA

    2014-06-01

    Full Text Available This work addresses the design and configuration of a Eulerian sediment trap mooring array, which was deployed at the shelf edge (zm ≈ 140 m 80 km off Cabo Frio, SE- Brazil (23° S. The site was subject to interplay between the Tropical Waters (TW of the Brazil Current (BC, intrusions from the South Atlantic Central Waters (SACW, which are the source of upwelling in the region, and other oceanographic processes. Detailed computations were used to optimize the total weight, buoyancy balance, and maximum acceptable tilt to avoid hydrodynamic bias in the trapping efficiency and array adaptation to the local oceanographic conditions with the assistance of Matlab and Muringa programs and Modular Ocean Model 4.0 (MOM; i.e., to assert the vertical distribution of the meridional current component. The velocity range of the current component was determined by short term measurements to be between 0.1 and 0.5 m/s. Projections led to a resulting minimum anchor weight of 456 kg. The necessary line tension was ascertained by using the appropriate distribution of a series of buoys along the array, which finally attained a high vertical load of 350 kg because of the attached oceanographic equipment. Additional flotation devices resulted in a stable mooring array as reflected by their low calculated tilt (2.6° ± 0.6°. A low drag of 16 N was computed for the maximum surface current velocity of 0.5 m/s. The Reynolds number values ranged from 4 × 104 to 2 × 105 and a cone-trap aspect ratio of 1.75 was used to assess the trap sampling efficiency upon exposure to different current velocities.

  8. Warm Bias and Parameterization of Boundary Upwelling in Ocean Models

    Energy Technology Data Exchange (ETDEWEB)

    Cessi, Paola; Wolfe, Christopher

    2012-11-06

    It has been demonstrated that Eastern Boundary Currents (EBC) are a baroclinic intensification of the interior circulation of the ocean due to the emergence of mesoscale eddies in response to the sharp buoyancy gradients driven by the wind-stress and the thermal surface forcing. The eddies accomplish the heat and salt transport necessary to insure that the subsurface flow is adiabatic, compensating for the heat and salt transport effected by the mean currents. The EBC thus generated occurs on a cross-shore scale of order 20-100 km, and thus this scale needs to be resolved in climate models in order to capture the meridional transport by the EBC. Our result indicate that changes in the near shore currents on the oceanic eastern boundaries are linked not just to local forcing, such as coastal changes in the winds, but depend on the basin-wide circulation as well.

  9. Oceanic contributions from tropical upwelling systems to atmospheric halogens

    Science.gov (United States)

    Ziska, Franziska; Hepach, Helmke; Stemmler, Irene; Quack, Birgit; Atlas, Elliot; Fuhlbrügge, Steffen; Bracher, Astrid; Tegtmeier, Susann; Krüger, Kirstin

    2014-05-01

    Short lived halogenated substances (halocarbons) from the oceans contribute to atmospheric halogens, where they are involved in ozone depletion and aerosol formation. Oceanic regions that are characterized by high biological activity are often associated with increased halocarbon abundance of e.g. bromoform (CHBr3) and dibromomethane (CH2Br2), representing the main contributors to atmospheric organic bromine. Apart from biological production, photochemical pathways play an important role in the formation of methyl iodide (CH3I), the most abundant organoiodine in the marine atmosphere. Recently, the contribution of biogenic diiodomethane (CH2I2) and chloroiodomethane (CH2ClI) to atmospheric organic iodine has been estimated to be similarly significant as CH3I. In the tropics, rapid uplift of surface air can transport these short-lived compounds into the upper troposphere and into the stratosphere. Oceanic upwelling systems off Mauritania, Peru and in the equatorial Atlantic might therefore potentially contribute large amounts of halocarbons to the stratosphere. Concentrations and emissions of iodo- and bromocarbons from several SOPRAN campaigns in different tropical upwelling systems, the Mauritanian and the equatorial upwelling in the Atlantic, as well as the Peruvian upwelling in the Pacific, will be presented. Processes contributing to halocarbon occurrence in the water column, as well as biological and physical factors influencing their emission into the atmosphere are investigated (Fuhlbrügge, et al. 2013; Hepach et al., 2013). We will present the relative contribution of the upwelling systems to global air-sea fluxes from different modelling studies. The data based bottom-up emissions from Ziska et al. (2013) will be compared to model simulated halocarbons. The model is a global three-dimensional ocean general circulation model with an ecosystem model and halocarbon module embedded (MPIOM/HAMOCC). It resolves CH3I and CHBr3 production, degradation, and

  10. Partial decoupling of primary productivity from upwelling in the California Current system

    Science.gov (United States)

    Renault, Lionel; Deutsch, Curtis; McWilliams, James C.; Frenzel, Hartmut; Liang, Jun-Hong; Colas, François

    2016-07-01

    Coastal winds and upwelling of deep nutrient-rich water along subtropical eastern boundaries yield some of the ocean's most productive ecosystems. Simple indices of coastal wind strength have been extensively used to estimate the timing and magnitude of biological productivity on seasonal and interannual timescales and underlie the prediction that anthropogenic climate warming will increase the productivity by making coastal winds stronger. The effect of wind patterns on regional net primary productivity is not captured by such indices and is poorly understood. Here we present evidence, using a realistic model of the California Current system and satellite measurements, that the observed slackening of the winds near the coast has little effect on near-shore phytoplankton productivity despite a large reduction in upwelling velocity. On the regional scale the wind drop-off leads to substantially higher production even when the total upwelling rate remains the same. This partial decoupling of productivity from upwelling results from the impact of wind patterns on alongshore currents and the eddies they generate. Our results imply that productivity in eastern boundary upwelling systems will be better predicted from indices of the coastal wind that account for its offshore structure.

  11. What controls biological productivity in coastal upwelling systems? Insights from a comparative modeling study

    Science.gov (United States)

    Lachkar, Z.; Gruber, N.

    2011-06-01

    The magnitude of the biological productivity in Eastern Boundary Upwelling Systems (EBUS) is traditionally viewed as directly reflecting the upwelling intensity. Yet, different EBUS show different sensitivities of productivity to upwelling-favorable winds (Carr and Kearns, 2003). Here, using a comparative modeling study of the California Current System (California CS) and Canary Current System (Canary CS), we show how physical and environmental factors, such as light, temperature and cross-shore circulation modulate the response of biological productivity to upwelling strength. To this end, we made a series of eddy-resolving simulations of the California CS and Canary CS using the Regional Ocean Modeling System (ROMS), coupled to a nitrogen based Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD) ecosystem model. We find the nutrient content of the euphotic zone to be 20 % smaller in the Canary CS relative to the California CS. Yet, the biological productivity is 50 % smaller in the latter. This is due to: (1) a faster nutrient-replete growth in the Canary CS relative to the California CS, related to a more favorable light and temperature conditions in the Canary CS, and (2) the longer nearshore water residence times in the Canary CS which lead to larger buildup of biomass in the upwelling zone, thereby enhancing the productivity. The longer residence times in the Canary CS appear to be associated with the wider continental shelves and the lower eddy activity characterizing this upwelling system. This results in a weaker offshore export of nutrients and organic matter, thereby increasing local nutrient recycling and enhancing the coupling between new and export production in the Northwest African system. Our results suggest that climate change induced perturbations such as upwelling favorable wind intensification might lead to contrasting biological responses in the California CS and the Canary CS, with major implications for the biogeochemical cycles and fisheries

  12. What controls biological productivity in coastal upwelling systems? Insights from a comparative modeling study

    Directory of Open Access Journals (Sweden)

    Z. Lachkar

    2011-06-01

    Full Text Available The magnitude of the biological productivity in Eastern Boundary Upwelling Systems (EBUS is traditionally viewed as directly reflecting the upwelling intensity. Yet, different EBUS show different sensitivities of productivity to upwelling-favorable winds (Carr and Kearns, 2003. Here, using a comparative modeling study of the California Current System (California CS and Canary Current System (Canary CS, we show how physical and environmental factors, such as light, temperature and cross-shore circulation modulate the response of biological productivity to upwelling strength. To this end, we made a series of eddy-resolving simulations of the California CS and Canary CS using the Regional Ocean Modeling System (ROMS, coupled to a nitrogen based Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD ecosystem model. We find the nutrient content of the euphotic zone to be 20 % smaller in the Canary CS relative to the California CS. Yet, the biological productivity is 50 % smaller in the latter. This is due to: (1 a faster nutrient-replete growth in the Canary CS relative to the California CS, related to a more favorable light and temperature conditions in the Canary CS, and (2 the longer nearshore water residence times in the Canary CS which lead to larger buildup of biomass in the upwelling zone, thereby enhancing the productivity. The longer residence times in the Canary CS appear to be associated with the wider continental shelves and the lower eddy activity characterizing this upwelling system. This results in a weaker offshore export of nutrients and organic matter, thereby increasing local nutrient recycling and enhancing the coupling between new and export production in the Northwest African system. Our results suggest that climate change induced perturbations such as upwelling favorable wind intensification might lead to contrasting biological responses in the California CS and the Canary CS, with major implications for the biogeochemical cycles

  13. Influence of external climate forcing on coastal upwelling systems analysed in ensemble of past millennium climate simulations

    Science.gov (United States)

    Tim, Nele; Zorita, Eduardo; Hünicke, Birgit; Yi, Xin; Emeis, Kay

    2016-04-01

    Eastern Boundary Upwelling Systems are highly productive coastal ocean areas where nutrient rich, cold water upwells by the action of favorable winds. Observations over the 20th century and ocean sediment records, which may be indicative of upwelling, display an intensification due to stronger external climate forcing, such as increasing greenhouse gas concentrations or changes in solar irradiance. This intensification is compatible with the hypothesis put forward by Bakun (1990) that a stronger external radiative forcing should lead to a more intense coastal upwelling. Here, we analyze ensemble of simulations covering the past millennium with the aim of identifying and quantifying the role of external climate forcing on upwelling in the major Eastern Boundary Upwelling System. We analyse the decadal variability and centennial trends of upwelling in ensemble of simulations with the global climate model MPI-ESM covering the past millennium, the last 150 years and the next 100 years. The future simulations were driven by three IPCC scenarios of concentrations of anthropogenic greenhouse gases, RCP2.5, RCP4.5 and RCP 8.5. For the past millennium and the last 150 years, coastal upwelling does not show any imprint of external forcing. This result indicates that chaotic internal variability has dominated upwelling intensity in major upwelling regions over the last thousand years and even since industrialisation up to present. For the 21st century, all ensemble members show a consistent and significant intensification of upwelling in the strongest scenario RCP8.5 for the Benguela upwelling region, consistent and significant weakening for Morocco and California, and no significant change for the Peruvian upwelling. Weaker scenarios do not produce consistent long-term trends that are replicated in all ensemble members. The results are confirmed by analysing another ensemble of past millennium simulations with the model CESM-CAM5 (Community Earth System Model

  14. Winter conditioning of the Cascadian margin upwelling system: Remote forcing and coastal river influences (Invited)

    Science.gov (United States)

    Hales, B. R.; Goni, M. A.; Evans, W.; Harris, K. E.; Siedlecki, S. A.; Skyllingstad, E. D.; Wall, C.; Wetz, M.; White, A. E.

    2013-12-01

    The Cascadian margin stretches along the North American Pacific coast from Cape Mendocino to Vancouver Island, and across the land-ocean margin from the crest of the coastal mountains to the California Current. Carbonate system chemistry in these coastal waters is among the most dynamic in the world, with high net community productivity driving the system to a regionally important CO2 sink, while upwelled, respiration-influenced waters carry such elevated CO2 that they are often corrosive to biogenic carbonates. Most of the focus on this ecosystem has been on the influence of the seasonal upwelling and interaction with the upper thermocline of the ocean interior; recently, however, the downwelling-season has been recognized as critical in shaping the carbon cycling of the ecosystem. We present a combination of in-water survey and mooring data from river, estuary, and shelf waters; remote-sensing of coastal surface waters and watershed precipitation; and modeling results describing the physics of coastal circulation and storm-event precipitation and river discharge that shows how the winter conditions control carbon cycling. Coastally-trapped internal waves propagating northward from remote upwelling regions to the south lead to shoaling of the pycnocline such that upwelled source waters are present far inshore of the shelfbreak months before the onset of upwelling favorable winds. The close proximity of upwelled source waters to inner shelf upwelling locations leads to rapid transition in response to late winter and early spring upwelling favorable wind events. Winter storms and closely coupled flooding events deliver regionally significant amounts of nutrient-rich, low-CO2 fresh waters to the coastal ocean during downwelling conditions that retain these inputs on the shelf, and this fuels phytoplankton blooms that are a significant contribution to the annual net community production. These blooms and river influences maintain low coastal surface water pCO2 during

  15. What controls biological production in coastal upwelling systems? Insights from a comparative modeling study

    Directory of Open Access Journals (Sweden)

    Z. Lachkar

    2011-10-01

    Full Text Available The magnitude of net primary production (NPP in Eastern Boundary Upwelling Systems (EBUS is traditionally viewed as directly reflecting the wind-driven upwelling intensity. Yet, different EBUS show different sensitivities of NPP to upwelling-favorable winds (Carr and Kearns, 2003. Here, using a comparative modeling study of the California Current System (California CS and Canary Current System (Canary CS, we show how physical and environmental factors, such as light, temperature and cross-shore circulation modulate the response of NPP to upwelling strength. To this end, we made a series of eddy-resolving simulations of the two upwelling systems using the Regional Oceanic Modeling System (ROMS, coupled to a nitrogen-based Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD ecosystem model. Using identical ecological/biogeochemical parameters, our coupled model simulates a level of NPP in the California CS that is 50 % smaller than that in the Canary CS, in agreement with observationally based estimates. We find this much lower NPP in the California CS despite phytoplankton in this system having nearly 20 % higher nutrient concentrations available to fuel their growth. This conundrum can be explained by: (1 phytoplankton having a faster nutrient-replete growth in the Canary CS relative to the California CS; a consequence of more favorable light and temperature conditions in the Canary CS, and (2 the longer nearshore water residence times in the Canary CS, which permit a larger buildup of biomass in the upwelling zone, thereby enhancing NPP. The longer residence times in the Canary CS appear to be a result of the wider continental shelves and the lower mesoscale activity characterizing this upwelling system. This results in a weaker offshore export of nutrients and organic matter, thereby increasing local nutrient recycling and reducing the spatial decoupling between new and export production in the Canary CS. Our results suggest that climate change

  16. Modelling shelf-ocean exchange and its biogeochemical consequences in coastal upwelling systems

    DEFF Research Database (Denmark)

    Muchamad, Al Azhar

    slope and deeper depths. The coupled model may potentially serve as a robust tool in investigation of the dynamics of oceanic biogeochemical cycle throughout Earth history as well as a practical method to quantified storage of carbon flux into the ocean across the continental margins under present day...... in eastern boundary upwelling systems is an example of the most productive ocean waters over continental margins where intense supply of nutrients occur from deeper ocean waters. Interesting questions arise related to the biogeochemical cycles in such upwelling systems; such as 1) how the recently observed...... active but cryptic sulfur cycle possibly is coupled to the nitrogen cycle in an oxygen-minimum-zone (OMZ), 2) what is the relation between the shelf–ocean exchange, continental shelf width and development of the observed bottom water anoxia/euxinia associated with different configurations of continental...

  17. Oxygen cycling in the northern Benguela Upwelling System: Modelling oxygen sources and sinks

    Science.gov (United States)

    Schmidt, Martin; Eggert, Anja

    2016-12-01

    This paper elucidates the oxygen dynamics in the northern Benguela Upwelling System by means of process oriented, numerical modelling. Owing to the complex physical-biological interaction in this system, a coupled hydrodynamic-biogeochemical model is required to grasp the various aspects of the oxygen dynamics. We used high-resolution atmospheric fields derived from observations to force our model, available since 1999. The model results represent a 15 years, consistent data set of realistic hydrographic and ecosystem variables, including oxygen distribution patterns. After a concise description of the main aspects of the model, we use the model data to analyse the components contributing to the oxygen dynamics, namely, the ocean circulation, the exchange between ocean and atmosphere as well as the local biogeochemical oxygen cycling in the system. We thoroughly validate the model with available field observations and remote sensing data. The strengths of coastal upwelling, which controls the nutrient supply to the euphotic zone, as well as the poleward undercurrent that carries oxygen and nutrients to the shelf in the northern Benguela Upwelling System are well reproduced in the model. Among the biological oxygen sinks, mineralisation in the sediment, respiration of zooplankton and nitrification in the water column are important. We also found that vertical migration of zooplankton in response to the oxygen conditions provides a regulating feedback, which may prevent a complete deoxygenation of suboxic waters. As long as oxygen or nitrate are available in the bottom waters, the activities of chemolithoautotrophic sulphur bacteria on the sediment surface keep the redoxcline within the sediment and prevent the release of hydrogen sulphide into the water column. By horizontal integration of the simulated ocean-atmosphere oxygen flux, it can be shown that the Kunene upwelling cell between 16 ° S and 18 ° S is a boundary between the equatorial ocean, characterise by

  18. Variability in upwelling intensity and nutrient regime in the coastal upwelling system offshore Namibia: results from sediment archives

    Science.gov (United States)

    Emeis, Kay-Christian; Struck, Ulrich; Leipe, Thomas; Ferdelman, Timothy G.

    2009-03-01

    The coastal upwelling system offshore Namibia is ideally suited to address a focal question of the Integrated Marine Biogeochemistry and Ecosystem Research Programme: what are the mechanisms that drive long-term changes in ecosystems? Considerable interannual variability in climatic forcing is indicated by long time series of meteorological and remote sensing observation; these accompany considerable interannual to interdecadal changes in the upwelling intensity over the last 100 years, as well as a centennial trend. On longer time scales, the only archives available are sediment records spanning the late Holocene. To decipher the sediment record, we mapped surface-sediment patterns of proxies for physical (sea surface temperature/SST from alkenone unsaturation indexes) and nutrient (δ15N on bulk sedimentary N) variables. Their present-day surface-sediment patterns outline the coastal upwelling cells and filaments and associated high productivity area. Analysed in an array of dated sediment cores, the spatial patterns of SST suggest long-term (>100 years) variability in the location and intensity of individual upwelling cells. The patterns of δ15N outline an area of intense denitrification near the coast, and advection of water with low-oxygen concentrations in the undercurrent from the North. δ15N exhibits considerable downcore variability, in particular over the last 50 years. The variability appears to be governed by differences in extent of denitrification and thus of the shelf oxygen balance, which appears to have deteriorated in the last 50 years. Together, the data suggest that SST and denitrification conditions have remained in the narrow bounds outlined by today’s patterns in surface sediments, but that spatially small variability in upwelling intensity and make-up of upwelling feed waters induced considerable changes in the lower trophic levels of the coastal upwelling ecosystem over the last 6,000 years. Attempts to correlate proxy records from

  19. Biophysical interactions in the Cabo Frio upwelling system, southeastern Brazil

    Directory of Open Access Journals (Sweden)

    Sergio Augusto Coelho-Souza

    2012-09-01

    Full Text Available The rising of cold water from deeper levels characterizes coastal upwelling systems. This flow makes nutrients available in the euphotic layer, which enhances phytoplankton production and growth. On the Brazilian coast, upwelling is most intense in the Cabo Frio region (RJ. The basic knowledge of this system was reviewed in accordance with concepts of biophysical interactions. The high frequency and amplitude of the prevailing winds are the main factor promoting the rise of South Atlantic Central Water, but meanders and eddies in the Brazil Current as well as local topography and coast line are also important. Upwelling events are common during spring/summer seasons. Primary biomass is exported by virtue of the water circulation and is also controlled by rapid zooplankton predation. Small pelagic fish regulate plankton growth and in their turn are preyed on by predatory fish. Sardine furnishes an important regional fish stock. Shoreline irregularities define the embayment formation of the Marine Extractive Reserve of Arraial do Cabo making it an area with evident different intensities of upwelled water that harbors high species diversity. Consequently, on a small spatial scale there are environments with tropical and subtropical features, a point to be explored as a particularity of this ecosystem.Os sistemas costeiros de ressurgência são caracterizados pela ascensão de águas frias que tornam os nutrientes disponíveis na camada eufótica para o crescimento e aumento da produção fitoplanctônica. No Brasil, a região do Cabo Frio (RJ é o principal sistema de ressurgência costeira. O objetivo desse artigo foi revisar o atual conhecimento desse sistema através dos conceitos sobre interações biofísicas. A ascensão da Água Central do Atlântico Sul ocorre devido à alta frequência e amplitude dos ventos, à presença de meandros e vórtices na Corrente do Brasil, além da topografia local e da linha de costa. Os eventos de ressurg

  20. Defining seascapes for marine unconsolidated shelf sediments in an eastern boundary upwelling region: The southern Benguela as a case study

    Science.gov (United States)

    Karenyi, Natasha; Sink, Kerry; Nel, Ronel

    2016-02-01

    Marine unconsolidated sediment habitats, the largest benthic ecosystem, are considered physically controlled ecosystems driven by a number of local physical processes. Depth and sediment type are recognised key drivers of these ecosystems. Seascape (i.e., marine landscape) habitat classifications are based solely on consistent geophysical features and provide an opportunity to define unconsolidated sediment habitats based on processes which may vary in distribution through space and time. This paper aimed to classify unconsolidated sediment seascapes and explore their diversity in an eastern boundary upwelling region at the macro-scale, using the South African west coast as a case study. Physical variables such as sediment grain size, depth and upwelling-related variables (i.e., maximum chlorophyll concentration, austral summer bottom oxygen concentration and sediment organic carbon content) were included in the analyses. These variables were directly measured through sampling, or collated from existing databases and the literature. These data were analysed using multivariate Cluster, Principal Components Ordination and SIMPER analyses (in PRIMER 6 + with PERMANOVA add-in package). There were four main findings; (i) eight seascapes were identified for the South African west coast based on depth, slope, sediment grain size and upwelling-related variables, (ii) three depth zones were distinguished (inner, middle and outer shelf), (iii) seascape diversity in the inner and middle shelves was greater than the outer shelf, and (iv) upwelling-related variables were responsible for the habitat diversity in both inner and middle shelves. This research demonstrates that the inclusion of productivity and its related variables, such as hypoxia and sedimentary organic carbon, in seascape classifications will enhance the ability to distinguish seascapes on continental shelves, where productivity is most variable.

  1. Diatoms Si uptake capacity drives carbon export in coastal upwelling systems

    NARCIS (Netherlands)

    Abrantes, F.; Cermeno, P.; Lopes, C.; Romero, O.; Rufino, M.; van Iperen, J.; Matos, L.; Magalhães, V.

    2016-01-01

    Coastal upwelling systems account for approximatelyhalf of global ocean primary production and contributedisproportionately to biologically driven carbon sequestration.Diatoms, silica-precipitating microalgae, constitutethe dominant phytoplankton in these productive regions,and their abundance and a

  2. Evaluation and application of the ROMS 1-way embedding procedure to the central california upwelling system

    Science.gov (United States)

    Penven, Pierrick; Debreu, Laurent; Marchesiello, Patrick; McWilliams, James C.

    What most clearly distinguishes near-shore and off-shore currents is their dominant spatial scale, O (1-30) km near-shore and O (30-1000) km off-shore. In practice, these phenomena are usually both measured and modeled with separate methods. In particular, it is infeasible for any regular computational grid to be large enough to simultaneously resolve well both types of currents. In order to obtain local solutions at high resolution while preserving the regional-scale circulation at an affordable computational cost, a 1-way grid embedding capability has been integrated into the Regional Oceanic Modeling System (ROMS). It takes advantage of the AGRIF (Adaptive Grid Refinement in Fortran) Fortran 90 package based on the use of pointers. After a first evaluation in a baroclinic vortex test case, the embedding procedure has been applied to a domain that covers the central upwelling region off California, around Monterey Bay, embedded in a domain that spans the continental U.S. Pacific Coast. Long-term simulations (10 years) have been conducted to obtain mean-seasonal statistical equilibria. The final solution shows few discontinuities at the parent-child domain boundary and a valid representation of the local upwelling structure, at a CPU cost only slightly greater than for the inner region alone. The solution is assessed by comparison with solutions for the whole US Pacific Coast at both low and high resolutions and to solutions for only the inner region at high resolution with mean-seasonal boundary conditions.

  3. Implications of Upwells as Hydrodynamic Jets in a Pulse Jet Mixed System

    Energy Technology Data Exchange (ETDEWEB)

    Pease, Leonard F. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Bamberger, Judith A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Minette, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-08-01

    This report evaluates the physics of the upwell flow in pulse jet mixed systems in the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Although the initial downward flow and radial flow from pulse jet mixers (PJMs) has been analyzed in some detail, the upwells have received considerably less attention despite having significant implications for vessel mixing. Do the upwells behave like jets? How do the upwells scale? When will the central upwell breakthrough? What proportion of the vessel is blended by the upwells themselves? Indeed, how the physics of the central upwell is affected by multiple PJMs (e.g., six in the proposed mixing vessels), non-Newtonian rheology, and significant multicomponent solids loadings remain unexplored. The central upwell must satisfy several criteria to be considered a free jet. First, it must travel for several diameters in a nearly constant direction. Second, its velocity must decay with the inverse of elevation. Third, it should have an approximately Gaussian profile. Fourth, the influence of surface or body forces must be negligible. A combination of historical data in a 12.75 ft test vessel, newly analyzed data from the 8 ft test vessel, and conservation of momentum arguments derived specifically for PJM operating conditions demonstrate that the central upwell satisfies these criteria where vigorous breakthrough is achieved. An essential feature of scaling from one vessel to the next is the requirement that the underlying physics does not change adversely. One may have confidence in scaling if (1) correlations and formulas capture the relevant physics; (2) the underlying physics does not change from the conditions under which it was developed to the conditions of interest; (3) all factors relevant to scaling have been incorporated, including flow, material, and geometric considerations; and (4) the uncertainty in the relationships is sufficiently narrow to meet required specifications. Although the central upwell

  4. Diatoms Si uptake capacity drives carbon export in coastal upwelling systems

    Science.gov (United States)

    Abrantes, Fatima; Cermeno, Pedro; Lopes, Cristina; Romero, Oscar; Matos, Lélia; Van Iperen, Jolanda; Rufino, Marta; Magalhães, Vitor

    2016-07-01

    Coastal upwelling systems account for approximately half of global ocean primary production and contribute disproportionately to biologically driven carbon sequestration. Diatoms, silica-precipitating microalgae, constitute the dominant phytoplankton in these productive regions, and their abundance and assemblage composition in the sedimentary record is considered one of the best proxies for primary production. The study of the sedimentary diatom abundance (SDA) and total organic carbon content (TOC) in the five most important coastal upwelling systems of the modern ocean (Iberia-Canary, Benguela, Peru-Humboldt, California, and Somalia-Oman) reveals a global-scale positive relationship between diatom production and organic carbon burial. The analysis of SDA in conjunction with environmental variables of coastal upwelling systems such as upwelling strength, satellite-derived net primary production, and surface water nutrient concentrations shows different relations between SDA and primary production on the regional scale. On the global scale, SDA appears modulated by the capacity of diatoms to take up silicic acid, which ultimately sets an upper limit to global export production in these ocean regions.

  5. Diagnosing CO2 fluxes in the upwelling system off the Oregon coast

    Directory of Open Access Journals (Sweden)

    Z. Cao

    2014-05-01

    Full Text Available It is generally known that the interplay between the carbon and nutrients supplied from subsurface waters via biological metabolism would determine the CO2 fluxes in upwelling systems. However, quantificational assessment of such interplay is difficult because of the dynamic nature of both upwelling circulation and the associated biogeochemistry. In this study, the diagnosis approach based upon the carbon/nutrient mass balance in the Ocean-dominated Margin (OceMar framework was applied to resolve the CO2 fluxes in the well-known upwelling system in the US west coast off Oregon, using the data collected along two cross-shelf transects from the inner shelf to the open basin in spring/early summer 2007. Through examining the biological consumption on top of the water mass mixing built upon the total alkalinity–salinity relationship, we successfully predicted and semi-analytically resolved the CO2 fluxes showing strong uptakes from the atmosphere beyond the nearshore regions, primarily resulting from the higher utilization of nutrients relative to dissolved inorganic carbon (DIC based on their concurrent inputs from the depth. On the other hand, we showed significant CO2 outgassing in the nearshore regions associated with intensified upwelling and minor biological consumption, where CO2 fluxes could be simplified without considering DIC/nutrient consumption. We reasoned that our approach in conceptualizing OceMar would be in a steady state with balanced DIC and nutrients via both physical transport and biological alterations in comparable timescales.

  6. Microbial diversity of a Brazilian coastal region influenced by an upwelling system and anthropogenic activity.

    Directory of Open Access Journals (Sweden)

    Juliano C Cury

    Full Text Available BACKGROUND: Upwelling systems are characterised by an intense primary biomass production in the surface (warmest water after the outcrop of the bottom (coldest water, which is rich in nutrients. Although it is known that the microbial assemblage plays an important role in the food chain of marine systems and that the upwelling systems that occur in southwest Brazil drive the complex dynamics of the food chain, little is known about the microbial composition present in this region. METHODOLOGY/PRINCIPAL FINDINGS: We carried out a molecular survey based on SSU rRNA gene from the three domains of the phylogenetic tree of life present in a tropical upwelling region (Arraial do Cabo, Rio de Janeiro, Brazil. The aim was to analyse the horizontal and vertical variations of the microbial composition in two geographically close areas influenced by anthropogenic activity (sewage disposal/port activity and upwelling phenomena, respectively. A lower estimated diversity of microorganisms of the three domains of the phylogenetic tree of life was found in the water of the area influenced by anthropogenic activity compared to the area influenced by upwelling phenomena. We observed a heterogenic distribution of the relative abundance of taxonomic groups, especially in the Archaea and Eukarya domains. The bacterial community was dominated by Proteobacteria, Cyanobacteria and Bacteroidetes phyla, whereas the microeukaryotic community was dominated by Metazoa, Fungi, Alveolata and Stramenopile. The estimated archaeal diversity was the lowest of the three domains and was dominated by uncharacterised marine Crenarchaeota that were most closely related to Marine Group I. CONCLUSIONS/SIGNIFICANCE: The variety of conditions and the presence of different microbial assemblages indicated that the area of Arraial do Cabo can be used as a model for detailed studies that contemplate the correlation between pollution-indicating parameters and the depletion of microbial

  7. The significance of nitrogen regeneration for new production within a filament of the Mauritanian upwelling system

    Science.gov (United States)

    Clark, Darren R.; Widdicombe, Claire E.; Rees, Andrew P.; Woodward, E. Malcolm S.

    2016-05-01

    The Lagrangian progression of a biological community was followed in a filament of the Mauritanian upwelling system, north-west Africa, during offshore advection. The inert dual tracers sulfur hexafluoride and helium-3 labelled a freshly upwelled patch of water that was mapped for 8 days. Changes in biological, physical, and chemical characteristics were measured, including phytoplankton productivity, nitrogen assimilation, and regeneration. Freshly upwelled water contained high nutrient concentrations but was depleted in N compared to Redfield stoichiometry. The highest rate of primary productivity was measured on the continental shelf, associated with high rates of nitrogen assimilation and a phytoplankton community dominated by diatoms and flagellates. Indicators of phytoplankton abundance and activity decreased as the labelled water mass transited the continental shelf slope into deeper water, possibly linked to the mixed layer depth exceeding the light penetration depth. By the end of the study, the primary productivity rate decreased and was associated with lower rates of nitrogen assimilation and lower nutrient concentrations. Nitrogen regeneration and assimilation took place simultaneously. Results highlighted the importance of regenerated NH4+ in sustaining phytoplankton productivity and indicate that the upwelled NO3- pool contained an increasing fraction of regenerated NO3- as it advected offshore. By calculating this fraction and incorporating it into an f ratio formulation, we estimated that of the 12.38 Tg C of annual regional production, 4.73 Tg C was exportable.

  8. Climate change in the Iberian Upwelling System: a numerical study using GCM downscaling

    Science.gov (United States)

    Cordeiro Pires, Ana; Nolasco, Rita; Rocha, Alfredo; Ramos, Alexandre M.; Dubert, Jesus

    2016-07-01

    The present work aims at evaluating the impacts of a climate change scenario on the hydrography and dynamics of the Iberian Upwelling System. Using regional ocean model configurations, the study domain is forced with three different sets of surface fields: a climatological dataset to provide the control run; a dataset obtained from averaging several global climate models (GCM) that integrate the Intergovernmental Panel for Climate Change (IPCC) models used in climate scenarios, for the same period as the climatological dataset; and this same dataset but for a future period, retrieved from the IPCC A2 climate scenario. After ascertaining that the ocean run forced with the GCM dataset for the present compared reasonably well with the climatologically forced run, the results for the future run (relative to the respective present run) show a general temperature increase (from +0.5 to +3 °C) and salinity decrease (from -0.1 to -0.3), particularly in the upper 100-200 m, although these differences depend strongly on season and distance to the coast. There is also strengthening of the SST cross-shore gradient associated to upwelling, which causes narrowing and shallowing of the upwelling jet. This effect is contrary to the meridional wind stress intensification that is also observed, which would tend to strengthen the upwelling jet.

  9. Nutrients, oxygen and biogeochemical processes in the Humboldt upwelling current system off Peru

    Directory of Open Access Journals (Sweden)

    Michelle I. Graco

    2013-04-01

    Full Text Available The upwelling system of the Humboldt Current, is considered among the most productive systems in the world, extending along the eastern South Pacific off Chile and Peru. In particular the coastal waters off Peru attracted considerable interest for being among the most fertile and productive the world, highlighting fisheries, such as anchovy, which represent one of the pillars of the economy of Peru.

  10. Particle fluxes in the NW Iberian coastal upwelling system: Hydrodynamical and biological control

    Science.gov (United States)

    Zúñiga, D.; Villacieros-Robineau, N.; Salgueiro, E.; Alonso-Pérez, F.; Rosón, G.; Abrantes, F.; Castro, C. G.

    2016-07-01

    To better understand sources and transport of particulate material in the NW Iberian coastal upwelling system, a mooring line dotted with an automated PPS 4/3 sediment trap was deployed off Cape Silleiro at the base of the photic zone. The samples were collected from November 2008 through June 2012 over sampling periods of 4-12 days. Our study represents the first automated sediment trap database for the NW Iberian margin. The magnitude and composition of the settling material showed strong seasonal variability with the highest fluxes during the poleward and winter mixing periods (averages of 12.9±9.6 g m-2 d-1 and 5.6±5.6 g m-2 d-1 respectively), and comparatively lower fluxes (3.6±4.1 g m-2 d-1) for the upwelling season. Intensive deposition events registered during poleward and winter mixing periods were dominated by the lithogenic fraction (80±3%). They were associated to high energy wave-driven resuspension processes, due to the occurrence of south-westerly storms, and intense riverine inputs of terrestrial material from Minho and Douro rivers. On the other hand, during the spring - summer upwelling season, the share of biogenic compounds (organic matter, calcium carbonate (CaCO3), biogenic silica (bSiO2)) to downward fluxes was higher, reflecting an increase in pelagic sedimentation due to the seasonal intensification of primary production and negligible river inputs and wave-driven resuspended material. Otherwise, the large variations of biogenic settling particles were mainly modulated by upwelling intensity, which by means of upwelling filaments ultimately controlled the offshore transport of the organic carbon fixed by primary producers towards the adjacent ocean. Based on the average downward flux of organic carbon (212 mg C m-2 d-1) and considering an average primary production of 1013 mg C m-2 d-1 from literature, we estimated that about 21% of the fixed carbon is vertically exported during the upwelling season.

  11. A physical view of La Guajira Upwelling System, Colombian Basin, Caribbean Sea

    Science.gov (United States)

    Bernal, G.; Beier, E.; Barton, E. D.; Ruiz-Ochoa, M.; Correa, J. G.

    2013-05-01

    La Guajira Peninsula lies within a large upwelling system along the South Caribbean Coast, created by the NE trade winds. In this location, sea surface temperature (SST) exhibits the lowest mean value and the highest variability in the whole Colombian Basin. The seasonal variation of SST explains up to 75 % of the total variability. La Guajira coastal zone also experiences the highest values of wind stress and wind stress curl, with the greatest annual and semiannual variability in the Colombian Basin. It has been shown that wind stress curl enhances the upwelling over the region. Near 90% of the variability of SST in La Guajira can be explained by the seasonality plus the first three EOFs interannual modes: the first, synchronous throughout the Basin, is dominant, and consists of a uniform interannual variation in phase with the North Tropical Atlantic Index; the second co-varies strongly with the second mode of wind stress curl; and the third reflects the role of the vertical atmospheric circulation cell associated with the Caribbean Low Level Jet off Central America. The inclusion of wind stress curl with its maximum offshore of La Guajira explains in part the extension of cool coastal water into the Colombian Basin, with advection in filaments, eddies and meanders. In order to complement the physical knowledge of La Guajira upwelling system, an analysis of water masses, sea surface height, Ekman suction, Ekman transport and coastal upwelling index (CUI) was performed. Hydrographic data was obtained from gridded climatologies from the National Oceanographic Data Center (WOD01); sea surface height anomalies from the Archiving, Validation, and Interpretation of Satellite Oceanography (AVISO) data; and wind data from the Cross-Calibrated Multi-Platform Ocean Surface Wind Velocity Product for Meteorological and Oceanographic Applications (CCMP). The upwelling forms a local water mass, La Guajira surface water (LGSW), with the mixing of subtropical underwater and

  12. Wind-driven coastal upwelling along the western boundary of the Bay of Bengal during the southwest monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Shetye, S.R.; Shenoi, S.S.C.; Gouveia, A.D.; Michael, G.S.; Sundar, D.; Nampoothiri, G.

    , the longshore component of the wind stress was 0.45 dyne cm -2, which corresponds to an Ekman transport of 120 m 3 s -1 per 100 m of the coast. The winds were most favourable to upwelling when leg E of the track (Fig. 1) was covered. Here the Ekman transport... 88 90E -IO N Fig. 2. Winds measured on board the vessel every 3 h during the cruise (some of the wind vectors are not shown, to avoid confusion). Wind stress (F) was calculated using the bulk aerodynamic formula -Fffi CDp\\[~IV, where CD was taken...

  13. Imprint of external climate forcing on coastal upwelling in past and future climate

    Directory of Open Access Journals (Sweden)

    N. Tim

    2015-11-01

    Full Text Available The Eastern Boundary Upwelling Systems are the major coastal upwelling regions. The trade winds are driving these upwelling regimes located in the subtropics at the eastern boundary of the Atlantic and Pacific Ocean. Here we analyse the impact of the external climate forcing, e.g. the greenhouse gas concentration, solar activity and volcano eruptions, on these upwelling systems in simulations of ensembles of two Earth System Models. The ensembles contain three simulations for each time period which cover the past millennium (900–1850, the 20th century (1850–2005 and the near future (2006–2100. Using a set of simulations, differing only in their initial conditions, enables us to detect whether the variability is driven internally or externally. Our analysis shows that the variability of the simulated upwelling is to the most driven internally and that there are no significant trends except for the scenario with the most dramatic increase of greenhouse gas concentrations.

  14. Microzooplankton feeding impact in a coastal upwelling system on the NW Iberian margin: The Ría de Vigo

    Science.gov (United States)

    Teixeira, Isabel G.; Figueiras, Francisco G.; Crespo, Bibiana G.; Piedracoba, Sílvia

    2011-01-01

    The dilution technique, combined with identification and enumeration of pico-, nano- and micro-plankton by microscopy, was used to estimate microzooplankton impact on the microbial community in surface waters of a coastal embayment on the NW Iberian upwelling system. Microzooplankton were important consumers of autotrophic and heterotrophic plankton in this system, feeding up to 93% of standing stock and more than 100% of production of several groups. Heterotrophic bacteria and heterotrophic picoflagellates experienced the highest and constant impact, with 75-84% of their standing stocks and 85-102% of their production being channelled through the microbial food web. Pico- and nano-phytoplankton were also consumed, although maximum grazing occurred on diatoms during upwelling events, coinciding with highest primary production. Predation on pico-nano-heterotrophs was especially relevant under downwelling conditions, when consumption of total carbon and particularly autotrophic carbon was considerably lower than during upwelling. The results suggest that the existence of a multivorous food web, extending from the microbial loop to the herbivorous food web, could be a major feature in this coastal upwelling system. The microbial loop, which occurs as a permanent background in the system, would contribute to sustain the microbial food web during downwelling, whereas the herbivorous food web could coexist with a microbial food web based on large diatoms during upwelling. The multivorous food web would partially divert diatoms from sinking and hence favour the retention of organic matter in the water column. This could enhance the energy transfer to higher pelagic trophic levels in coastal upwelling systems.

  15. Intensification of upwelling along Oman coast in a warming scenario

    Science.gov (United States)

    Praveen, V.; Ajayamohan, R. S.; Valsala, V.; Sandeep, S.

    2016-07-01

    The oceanic impact of poleward shift in monsoon low-level jet (MLLJ) is examined using a Regional Ocean Modeling System (ROMS). Two sets of downscaling experiments were conducted using ROMS with boundary and initial conditions from six CMIP5 models. While outputs from the historical run (1981-2000) acts as forcing for the first, the second uses RCP8.5 (2080-2099). By comparing the outputs, it is found that Oman coast will experience an increase in upwelling in tune with MLLJ shift. Consistent with the changes in upwelling and zonal Ekman transport, temperature, salinity, and productivity show significant changes near the Oman coast. The changes in MLLJ causes the coastal wind to angle against the Oman coast in such a fashion that the net upwelling increases in the next century and so does the marine productivity. This study contrasts the general view of weakening of upwelling along the Arabian coasts due to the weakening of monsoon winds.

  16. Short-term changes in the northwest African Upwelling System induced by Saharan dust deposition events

    Energy Technology Data Exchange (ETDEWEB)

    Ramos, A G; Coca, J; Redondo, A [SeaSnet Canarias. Dpto. de Biologia (University of Las Palmas de Gran Canaria), Canary Islands (Spain); Cuevas, E; Alonso-Perez, S; Bustos, J J [Izana Atmospheric Research Center, Agencia Estatal de Meteorologia, Tenerife (Spain); Perez, C; Baldasano, J M [Earth Sciences Department. Barcelona Supercomputing Center, Barcelona (Spain); Nickovic, S [Atmospheric Research and Environment Branch, World Meteorological Organization, Geneva (Switzerland)], E-mail: aramos@pesca.gi.ulpgc.es

    2009-03-01

    During the last 7-year period (2000-2006) atmosphere circulation changes show strong influences on the dust storm deposition dynamics and, as a result, on the primary production dynamics of the northwest African Upwelling System. From 2000 to 2006, the annual mean sea level pressure became higher ranging from 1014 to 1015 mb. Mean annual zonal wind intensity became higher (from 1.1 to 1.8 m s{sup -1}), while the mean annual meridional was reduced from 6.2 to 5.3 m s{sup -1} at the north of the Canary Islands. Mean annual satellite-derived AVHRR/NOAA SST recorded in the northwest African Upwelling became warmer in both locations, from 18.3 deg. C to 18.8 deg. C in Cape Ghir and from 19.5 deg. C to 20.3 deg. C north Canary Islands waters. CHL records from the SeaWiFS/OV-2 showed a different pattern trend. Mean annual CHL levels increased at Cape Ghir from 0.65 mg m-3 to 0.9 mg m-3 and significantly reduced from 0.59 mg m{sup -3} to 0.31 mg m{sup -3} at the north of the Canary Islands. Changes observed in the role of CHL during the last 7-years period could be associated to intensive dust deposition and exceptional weather warming observed in this area since 2000. However, this study focused on a 7-year period and conclusions on possible links between dust deposition and marine biochemistry activity cannot be generalized.

  17. Bacterial community characterization and biogeochemistry of sediments from a tropical upwelling system (Cabo Frio, Southeastern Brazil)

    Science.gov (United States)

    Castelo-Branco, R.; Barreiro, A.; Silva, F. S.; Carvalhal-Gomes, S. B. V.; Fontana, L. F.; Mendonça-Filho, J. G.; Vasconcelos, V.

    2016-11-01

    The Cabo Frio Upwelling System is one of the largest and most productive areas in southeastern Brazil. Although it is well-known that bacterial communities play a crucial role in the biogeochemical cycles and food chain of marine ecosystems, little is known regarding the microbial communities in the sediments of this upwelling region. In this research, we address the effect of different hydrological conditions on the biogeochemistry of sediments and the diversity of bacterial communities. Biogeochemistry profiles of sediments from four sampling stations along an inner-outer transect on the continental shelf were evaluated and denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA gene fragments was used to study the bacterial community composition in these sediments. Our sequencing analysis of excised bands identified Alpha- and Gammaproteobacteria, Bacteroidetes and bacteria belonging to the Firmicutes phyla as the phylogenetic groups, indicating the existence of great diversity in these marine sediments. In this multidisciplinary study, the use of multivariate analysis was crucial for understanding how biogeochemical profiles influence bacterial community distribution. A Principal Component Analysis (PCA) indicated that the biogeochemical variables exhibited a clear spatial pattern that is mainly related to hydrological conditions. A Correspondence Analysis (CA) revealed an important association between certain taxonomic groups and specific sampling locations. Canonical Correspondence Analysis (CCA) demonstrated that the biogeochemistry influences the structure of the bacterial community in sediments. Among the bacterial groups identified, the most taxonomically diverse classes (Alphaproteobacteria and Gammaproteobacteria) were found to be distributed regardless of any studied biogeochemical variables influences, whereas other groups responded to biogeochemical conditions which, in turn, were influenced by hydrological conditions. This finding

  18. Inorganic carbon dynamics in the upwelling system off the Oregon coast and implications for commercial shellfish hatcheries

    Science.gov (United States)

    Vance, J. M.; Hales, B. R.

    2010-12-01

    The increasing absorption of anthropogenic CO2 by the global ocean and concomitant decrease in pH will alter seawater carbonate chemistry in ways that may negatively impact calcifying organisms. In particular, the change in saturation state (Ω) of calcium carbonate minerals calcite and aragonite may be energetically unfavorable for shell formation while favoring shell dissolution. Eastern boundary upwelling systems may provide insights into how ecosystems respond to future conditions of ocean acidification when deep water with high dissolved inorganic carbon (DIC), low pH and low Ω is forced toward the surface. Mortality in commercial seed stock and reduced wild set of the oyster Crassostrea gigas in the northeast Pacific during 2005-2009 reinforced the need for understanding biological responses to acidified ocean water. In response, a long-term strategy to understand local carbonate chemistry dynamics, seasonal perturbations and the effects on development of calcifying bivalves was developed. At present, a time-series of pCO2 measurements was implemented in April 2010 in Netarts Bay, Oregon at Whiskey Creek Shellfish Hatchery (WCH). The intake sits at a depth of 0.5-8ft and water is pumped in at 100gpm. A line taken off the intake is run continuously through a thermosalinograph at approximately 1.5gpm into a showerhead style equilibrator in which the headspace is recirculated by aerating the water for enhanced gas exchange. CO2 in equilibrated air is analyzed by NDIR. Additionally two discrete samples of intake seawater were taken across tidal cycles weekly and analyzed for total CO2 (TCO2) according to the methods of Hales et al. (2004) and pCO2 for quality control. The pCO2 in the bay exhibits a diurnal cycle representative of daytime photosynthesis and nighttime respiration. However, the phasing and profiles of these cycles are dominated by tidal mixing and are affected by the introduction of high pCO2 water during upwelling events. Diurnal pCO2 during

  19. Effects of upwelling, tides and biological processes on the inorganic carbon system of a coastal lagoon in Baja California

    Science.gov (United States)

    Ribas-Ribas, M.; Hernández-Ayón, J. M.; Camacho-Ibar, V. F.; Cabello-Pasini, A.; Mejia-Trejo, A.; Durazo, R.; Galindo-Bect, S.; Souza, A. J.; Forja, J. M.; Siqueiros-Valencia, A.

    2011-12-01

    The role of coastal lagoons and estuaries as sources or sinks of inorganic carbon in upwelling areas has not been fully understood. During the months of May-July, 2005, we studied the dissolved inorganic carbon system in a coastal lagoon of northwestern Mexico during the strongest period of upwelling events. Along the bay, different scenarios were observed for the distributions of pH, dissolved inorganic carbon (DIC) and apparent oxygen utilization (AOU) as a result of different combinations of upwelling intensity and tidal amplitude. DIC concentrations in the outer part of the bay were controlled by mixing processes. At the inner part of the bay DIC was as low as 1800 μmol kg -1, most likely due to high water residence times and seagrass CO 2 uptake. It is estimated that 85% of San Quintín Bay, at the oceanic end, acted as a source of CO 2 to the atmosphere due to the inflow of CO 2-rich upwelled waters from the neighboring ocean with high positive fluxes higher than 30 mmol C m -2 d -1. In contrast, there was a net uptake of CO 2 and HCO 3- by the seagrass bed Zostera marina in the inner part of the bay, so the pCO 2 in this zone was below the equilibrium value and slightly negative CO 2 fluxes of -6 mmol C m -2 d -1. Our positive NEP and ΔDIC values indicate that Bahía San Quintín was a net autotrophic system during the upwelling season during 2005.

  20. Octopus vulgaris paralarvae vertical distribution in a fluctuating upwelling-downwelling system

    Directory of Open Access Journals (Sweden)

    Lorena Olmos Pérez

    2014-06-01

    - Upwelling situation: superficial waters (0-20m enter through the northern mouth of the Ría and are washed through the southern mouth. This water movement promotes the entrance of cold, bottom upwelled water through the southern mouth of the Ría. Under this scenario, Octopus paralarvae are concentrated at the surface (10-0m, thus leaving the Ría. This difference is bigger after strong upwelling during the previous days. Abundances inside the Ría are the highest, maybe because it acts as a temporal retention area, or because cold upwelled waters might stimulate hatching inside the Ría. Day/night changes under strong upwelling conditions: paralarvae abundance in both mouths was quite similar, except that during the day they were in sub-surficial waters (10-5 m, while at night paralarvae were mainly found close to the surface (0-5 m. This vertical distribution during the day is remarkable because paralarvae may select offward surface waters.

  1. Distribution of zooplankton biomass and potential metabolic activities across the northern Benguela upwelling system

    Science.gov (United States)

    Fernández-Urruzola, I.; Osma, N.; Packard, T. T.; Gómez, M.; Postel, L.

    2014-11-01

    The distribution of zooplankton biomass and potential metabolic rates, in terms of electron transport system (ETS) and glutamate dehydrogenase (GDH), were analyzed along a cross-shelf transect in waters off Namibia. The highly variable dynamics of upwelling filaments promoted short-term fluctuations in the zooplankton biomass and metabolism. Maximum values were characteristically found over the shelf-break, where zooplankton biomass as dry mass (DM) reached peaks of 64.5 mg m- 3 within the upper 200 m in late August. Two weeks later, the zooplankton-DM decreased by more than a third (19 mg DM m- 3). Zooplankton potential respiration and NH4+ excretion averaged 234 μmol O2 m- 3 d- 1 and 169 μmol NH4+ m- 3 d- 1 in the Namibian shelf, respectively. High protein-specific ETS activities even in the low-chlorophyll waters outside the filament suggested a shift into greater omnivory seaward. In this light, zooplankton elemental and isotopic compositions were used to investigate the pelagic food web interactions. They evidenced spatial changes in the carbon resource for zooplankton as well as changes in the form of nitrogen that fueled the biological production in aging advected waters. Overall, both aspects of zooplankton metabolism impacted the primary productivity at a level less than 10% under all the different oceanographic conditions.

  2. Jet stream intraseasonal oscillations drive dominant ecosystem variations in Oregon's summertime coastal upwelling system.

    Science.gov (United States)

    Bane, John M; Spitz, Yvette H; Letelier, Ricardo M; Peterson, William T

    2007-08-14

    Summertime wind stress along the coast of the northwestern United States typically exhibits intraseasonal oscillations (ISOs) with periods from approximately 15 to 40 days, as well as fluctuations on the 2- to 6-day "weather-band" and 1-day diurnal time scales. Coastal upwelling of cool, nutrient-rich water is driven by extended periods of equatorward alongshore winds, and we show that the approximately 20-day ISOs in alongshore wind stress dominated the upwelling process during summer 2001 off Oregon. These wind stress ISOs resulted from north-south positional ISOs of the atmospheric jet stream (JS). Upper-ocean temperature, phytoplankton, and zooplankton varied principally on the approximately 20-day time scale as well, and these correlated with the ISOs in alongshore wind stress and JS position, even though there also were weather-band stress fluctuations of comparable magnitude. Such wind stress ISOs are typical along Oregon in the summer upwelling season, occurring in 10 of 12 years examined, including 2001. We present a previously unreported direct connection from the atmospheric JS to oceanic primary and secondary production on the intraseasonal time scale and show the leading importance of ISOs in driving this coastal upwelling ecosystem during a typical summer.

  3. Microbial and biogeochemical responses to projected future nitrate enrichment in the California upwelling system

    Directory of Open Access Journals (Sweden)

    Katherine Rose Marie Mackey

    2014-11-01

    Full Text Available Coastal California is a dynamic upwelling region where nitrogen (N and iron (Fe can both limit productivity and influence biogeochemistry over different spatial and temporal scales. With global change, the flux of nitrate from upwelling is expected to increase over the next century, potentially driving additional oceanic regions toward Fe limitation. In this study we explored the effect of changes in Fe/N ratio on native phytoplankton from five currently Fe-replete sites near the major California upwelling centers at Bodega Bay and Monterey Bay using nutrient addition incubation experiments. Despite the high nitrate levels (13-30 M in the upwelled water, phytoplankton at three of the five sites showed increased growth when 10 M nitrate was added. None of the sites showed enhanced growth following addition of 10 nM Fe. Nitrate additions favored slow sinking single-celled diatoms over faster sinking chain-forming diatoms, suggesting that future increases in nitrate flux could affect carbon and silicate export and alter grazer populations. In particular, solitary cells of Cylindrotheca were more abundant than the toxin-producing genus Pseudonitzschia following nitrate addition. These responses suggest the biogeochemistry of coastal California could change in response to future increases in nitrate, and multiple stressors like ocean acidification and hypoxia may further result in ecosystem shifts.

  4. Dynamics of the carbonate system in a large continental shelf system under the influence of both a river plume and coastal upwelling

    Science.gov (United States)

    Cao, Zhimian; Dai, Minhan; Zheng, Nan; Wang, Deli; Li, Qian; Zhai, Weidong; Meng, Feifei; Gan, Jianping

    2011-06-01

    We examined the dynamics of the carbonate system in a complex mixing scheme with enhanced biological consumption modulated by both a river plume and summer coastal upwelling in a large shelf system, the northern South China Sea (NSCS) shelf. The plume waters originated from a large flooding upstream the Pearl River, and extended from the mouth of the Pearl River estuary to the middle shelf and were characterized by low dissolved inorganic carbon (DIC) and total alkalinity (TAlk), and a high aragonite saturation state (Ωarag). In contrast, the upwelled water occupying the nearshore area was distinguished by high DIC and TAlk and a low Ωarag. While the dynamics of the carbonate system were largely shaped by physical mixing through plume and upwelling processes between the plume water, the offshore subsurface water and the offshore surface water, biological consumption of DIC was observable in both the river plume and the coastal upwelling areas and contributed to the elevated Ωarag during their pathway. Correlations between salinity normalized TAlk and DIC indicated that organic carbon production rather than biocalcification exclusively induced the DIC removal. By using a three end-member mixing model, we estimated the net community productivity in the plume water and the upwelled water to be 36 ± 19 mmol C m-2 d-1 and 23 ± 26 mmol C m-2 d-1, respectively. With the combination of stoichiometric relationship analysis of the carbonate system and applying the three end-member mixing model, we successfully differentiated semiquantitatively the biologically mediated DIC variations from its overall mixing control. We also attempted to link this natural process to the carbonate saturation on the NSCS shelf, contending that at present natural factors associated with the river plume and the coastal upwelling largely modulate the dynamics of the carbonate system on the NSCS shelf, whereas anthropogenic stressors such as ocean acidification currently play a relatively

  5. Modern sedimentation in the Cabo Frio upwelling system, Southeastern Brazilian shelf

    Directory of Open Access Journals (Sweden)

    Michel M. de Mahiques

    2005-09-01

    Full Text Available The analyses of Uk'37 paleotemperatures and sedimentological parameters in box cores from the Cabo Frio upwelling zone, southeastern Brazil, were used to understand the modern sedimentation as well as to evaluate the role played by the upwelling process in the sedimentary patterns. Three box-cores located closer to the upwelling area show a general trend of cooling waters taking place in the last 700 years. Since the present upwelling is dependent on local and remote wind regime, a phase of dominating NE winds favors a more effective upward transport of the cold thermocline level South Atlantic CentralWater towards the coast. The intensification in the upwelling regime for the last ca. 700 years can be associated with the strengthening of the NE winds off the area and a possible increase of the Brazil Current mesoscale activity. Nevertheless, the lack of significant correlation of the paleotemperatures and most of sedimentological parameters indicate that upwelling is not the only sedimentation mechanism in the area. Also, the comparison of sedimentological parameters reveals that eventual temporal changes are superimposed by the geographical variability. Sedimentation rates vary from 0.26 mm.yr-1 to 0.66 mm.yr-1.As análises de Uk'37 paleotemperaturas e de parâmetros sedimentológicos em amostras de box-core da zona de ressurgência de Cabo Frio, sudeste do Brasil, foram usadas para compreender os processos de sedimentação moderna na área, bem como avaliar o papel desempenhado pela ressurgência no estabelecimento dos padrões sedimentológicos principais. Como observado em três box-cores localizados nas proximidades da área de ressurgência, é possível verificar uma tendência geral de resfriamento das águas nos últimos 700 anos (idade calibrada. Uma vez que o processo de ressurgência é dependente do regime de ventos local e remoto, uma fase de ventos predominantes de NE favorece um deslocamento mais efetivo das águas frias da

  6. Meeting reproductive demands in a dynamic upwelling system: Foraging strategies of a pursuit-diving seabird, the marbled murrelet

    Science.gov (United States)

    Peery, M.Z.; Newman, S.H.; Storlazzi, C.D.; Beissinger, S.R.

    2009-01-01

    Seabirds maintain plasticity in their foraging behavior to cope with energy demands and foraging constraints that vary over the reproductive cycle, but behavioral studies comparing breeding and nonbreeding individuals are rare. Here we characterize how Marbled Murrelets (Brachyramphus marmoratus) adjust their foraging effort in response to changes in reproductive demands in an upwelling system in central California. We radio-marked 32 murrelets of known reproductive status (9 breeders, 12 potential breeders, and 11 nonbreeders) and estimated both foraging ranges and diving rates during the breeding season. Murrelets spent more time diving during upwelling than oceanographic relaxation, increased their foraging ranges as the duration of relaxation grew longer, and reduced their foraging ranges after transitions to upwelling. When not incubating, murrelets moved in a circadian pattern, spending nighttime hours resting near flyways used to reach nesting habitat and foraging during the daytime an average of 5.7 km (SD 6.7 km) from nighttime locations. Breeders foraged close to nesting habitat once they initiated nesting and nest attendance was at a maximum, and then resumed traveling longer distances following the completion of nesting. Nonbreeders had similar nighttime and daytime distributions and tended to be located farther from inland flyways. Breeders increased the amount of time they spent diving by 71-73% when they had an active nest by increasing the number of dives rather than by increasing the frequency of anaerobiosis. Thus, to meet reproductive demands during nesting, murrelets adopted a combined strategy of reducing energy expended commuting to foraging sites and increasing aerobic dive rates. ?? 2009 by The Cooper Ornithological Society. All rights reserved.

  7. Laboratory Simulation of an Iron(II)-rich Precambrian Marine Upwelling System to Explore the Growth of Photosynthetic Bacteria.

    Science.gov (United States)

    Maisch, Markus; Wu, Wenfang; Kappler, Andreas; Swanner, Elizabeth D

    2016-07-24

    A conventional concept for the deposition of some Precambrian Banded Iron Formations (BIF) proceeds on the assumption that ferrous iron [Fe(II)] upwelling from hydrothermal sources in the Precambrian ocean was oxidized by molecular oxygen [O2] produced by cyanobacteria. The oldest BIFs, deposited prior to the Great Oxidation Event (GOE) at about 2.4 billion years (Gy) ago, could have formed by direct oxidation of Fe(II) by anoxygenic photoferrotrophs under anoxic conditions. As a method for testing the geochemical and mineralogical patterns that develop under different biological scenarios, we designed a 40 cm long vertical flow-through column to simulate an anoxic Fe(II)-rich marine upwelling system representative of an ancient ocean on a lab scale. The cylinder was packed with a porous glass bead matrix to stabilize the geochemical gradients, and liquid samples for iron quantification could be taken throughout the water column. Dissolved oxygen was detected non-invasively via optodes from the outside. Results from biotic experiments that involved upwelling fluxes of Fe(II) from the bottom, a distinct light gradient from top, and cyanobacteria present in the water column, show clear evidence for the formation of Fe(III) mineral precipitates and development of a chemocline between Fe(II) and O2. This column allows us to test hypotheses for the formation of the BIFs by culturing cyanobacteria (and in the future photoferrotrophs) under simulated marine Precambrian conditions. Furthermore we hypothesize that our column concept allows for the simulation of various chemical and physical environments - including shallow marine or lacustrine sediments.

  8. Optimal boundary control and boundary stabilization of hyperbolic systems

    CERN Document Server

    Gugat, Martin

    2015-01-01

    This brief considers recent results on optimal control and stabilization of systems governed by hyperbolic partial differential equations, specifically those in which the control action takes place at the boundary.  The wave equation is used as a typical example of a linear system, through which the author explores initial boundary value problems, concepts of exact controllability, optimal exact control, and boundary stabilization.  Nonlinear systems are also covered, with the Korteweg-de Vries and Burgers Equations serving as standard examples.  To keep the presentation as accessible as possible, the author uses the case of a system with a state that is defined on a finite space interval, so that there are only two boundary points where the system can be controlled.  Graduate and post-graduate students as well as researchers in the field will find this to be an accessible introduction to problems of optimal control and stabilization.

  9. Influences of riverine and upwelling waters on the coastal carbonate system off Central Chile and their ocean acidification implications

    Science.gov (United States)

    Vargas, Cristian A.; Contreras, Paulina Y.; Pérez, Claudia A.; Sobarzo, Marcus; Saldías, Gonzalo S.; Salisbury, Joe

    2016-06-01

    A combined data set, combining data from field campaigns and oceanographic cruises, was used to ascertain the influence of both river discharges and upwelling processes, covering spatial and temporal variation in dissolved inorganic carbon (DIC) and aragonite saturation state. This work was conducted in one of the most productive river-influenced upwelling areas in the South Pacific coasts (36°S). Additionally, further work was also conducted to ascertain the contribution of different DIC sources, influencing the dynamics of DIC along the land-ocean range. Six sampling campaigns were conducted across seven stations at the Biobío River basin, covering approximately 200 km. Three research cruises were undertaken simultaneously, covering the adjacent continental shelf, including 12 sampling stations for hydrographic measurements. Additionally, six stations were also sampled for chemical analyses, covering summer, winter, and spring conditions over 2010 and 2011. Our results evidenced that seaward extent of the river plume was more evident during the winter field campaign, when highest riverine DIC fluxes were observed. The carbonate system along the river-ocean continuum was very heterogeneous varying over spatial and temporal scales. High DIC and pCO2 were observed in river areas with larger anthropogenic effects. CO2 supersaturation at the river plume was observed during all campaigns due to the influence of low pH river waters in winter/spring and high-pCO2 upwelling waters in summer. δ13CDIC evidenced that main DIC sources along the river and river plume corresponded to the respiration of terrestrial organic matter. We have linked this natural process to the carbonate saturation on the adjacent river-influenced coastal area, suggesting that Ωaragonite undersaturation in surface/subsurface waters is largely modulated by the influence of both river discharge and coastal upwelling events in this productive coastal area. Conditions of low Ωaragonite might impact

  10. Impacts of coastal upwelling off east Vietnam on the regional winds system: An air-sea-land interaction

    Science.gov (United States)

    Zheng, Zhe-Wen; Zheng, Quanan; Kuo, Yi-Chun; Gopalakrishnan, Ganesh; Lee, Chia-Ying; Ho, Chung-Ru; Kuo, Nan-Jung; Huang, Shih-Jen

    2016-12-01

    In this study, we analyze the influence of coastal upwelling off southeast Vietnam (CUEV) on local wind field using numerical simulations based on atmospheric model of Weather Research and Forecasting (WRF). Several scenarios are simulated by forcing identical model configurations with different SST fields. Based on simulation results, the relationship between CUEV and reduction of wind forcing is numerically evidenced. With the influence of a typical cold patch with a temperature drop of 3-5 °C, the local wind speeds can drop to less than 70% of original level. We find that the mechanism of response of the wind reduction to CUEV is enhancement of sea-breeze induced wind modulation. Onshore sea-breeze will enhance, while the contrast between land and sea is even more striking due to the contribution of a distinct coastal upwelling. This implies that air-sea-land interaction dominates the process of local wind system modulation in response to transient CUEV. This result sheds a new light on the air-sea interaction process within the SCS basin.

  11. Cell boundary fault detection system

    Science.gov (United States)

    Archer, Charles Jens; Pinnow, Kurt Walter; Ratterman, Joseph D.; Smith, Brian Edward

    2009-05-05

    A method determines a nodal fault along the boundary, or face, of a computing cell. Nodes on adjacent cell boundaries communicate with each other, and the communications are analyzed to determine if a node or connection is faulty.

  12. Absorbing Boundary Conditions for Hyperbolic Systems

    Institute of Scientific and Technical Information of China (English)

    Matthias Ehrhardt

    2010-01-01

    This paper deals with absorbing boundary conditions for hyperbolic systems in one and two space dimensions. We prove the strict well-posedness of the resulting initial boundary value problem in 1D. Afterwards we establish the GKS-stability of the corresponding Lax-Wendroff-type finite difference scheme. Hereby, we have to extend the classical proofs, since the (discretized) absorbing boundary conditions do not fit the standard form of boundary conditions for hyperbolic systems.

  13. MODELING AND ANALYSIS OF REGIONAL BOUNDARY SYSTEM

    Institute of Scientific and Technical Information of China (English)

    YAN Guangle; WANG Huanchen

    2001-01-01

    In this paper, the problems of modeling and analyzing the system with change able boundary are researched. First, a kind of expanding system is set up, in which the changeable boundary is dealt with as a regional boundary. Then some relative models are developed to describe the regional boundary system. Next, the transition or the driftage of bifurcation points in the system is discussed. A fascinating case is studied in which two or more than two classes of chaotic attractive points coexist together or exist alternatively in the same system. Lastly, an effective new method of chaos avoidance for the system is put forward.

  14. Life in the sea of plenty: Seasonal and regional comparison of physiological performance of Euphausia hanseni in the northern Benguela upwelling system

    Science.gov (United States)

    Werner, Thorsten; Buchholz, Cornelia; Buchholz, Friedrich

    2015-09-01

    Variability in upwelling events may lead to periods of constrained food availability in the northern Benguela upwelling system (NBUS), thereby affecting the physiological state and metabolic activity of euphausiids. Most attention has so far been paid to seasonal effects but little is known about regional variability. Metabolic activity (expressed by respiration and excretion rates) and physiological state (expressed by reproductive effort and moult activity) in Euphausia hanseni were examined at different stations during austral summer (minimum upwelling) and austral winter (maximum upwelling). Overall, regional differences in physiological state, influencing metabolic activity, were greater than seasonal ones, indicating favourable conditions for growth and reproduction year-round. Higher respiration rates were found for females in more advanced stages of sexual development. Moult stage did not affect oxygen consumption rates, however. The physiological state of E. hanseni at the time of capture may serve as a meaningful indicator of the associated hydrographic conditions in the NBUS, to be further used in eco-system analysis on seasonal or long-term time scales. A latitudinal comparison of species highlights the extraordinary physiological plasticity of euphausiids.

  15. Zooplankton associated with the oxygen minimum zone system in the northern upwelling region of Chile during March 2000

    Science.gov (United States)

    Escribano, Ruben; Hidalgo, Pamela; Krautz, Cristina

    2009-07-01

    Zooplankton in the coastal upwelling region off northern Chile may play a significant biogeochemical role by promoting carbon flux into the subsurface OMZ (oxygen minimum zone). This work identifies the dominant zooplankton species inhabiting the area influenced by the OMZ in March 2000 off Iquique (20°S, northern Chile). Abundance and vertical distribution studies revealed 17 copepod and 9 euphausiid species distributed between the surface and 600 m at four stations sampled both by day and by night. Some abundant species remained in the well-oxygenated upper layer (30 m), with no evidence of diel vertical migration, apparently restricted by a shallow (40-60 m) oxycline. Other species, however, were found closely associated with the OMZ. The large-sized copepod Eucalanus inermis was found below the oxycline and performed diel vertical migrations into the OMZ, whereas the very abundant Euphausia mucronata performed extensive diel vertical migrations between the surface waters and the core of the OMZ (200 m), even crossing it. A complete assessment of copepods and euphausiids revealed that the whole sampled water column (0-600 m) is occupied by distinct species having well-defined habitats, some of them within the OMZ. Ontogenetic migrations were evident in Eucalanidae and E. mucronata. Estimates of species biomass showed a substantial (>75% of total zooplankton biomass) daily exchange of C between the photic layer and the OMZ. Both E. inermis and E. mucronata can actively exchange about 37.8 g C m -2 d -1 between the upper well-oxygenated (0-60 m) layer and the deeper (60-600 m) OMZ layer. This migrant biomass may contribute about 7.2 g C m -2 d -1 to the OMZ system through respiration, mortality, and production of fecal pellets within the OMZ. This movement of zooplankton in and out of the OMZ, mainly as a result of the migratory behavior of E. mucronata, suggests a very efficient mechanism for introducing large amounts of freshly produced carbon into the OMZ

  16. Export of pre-aged, labile DOM from a central California coastal upwelling system: Insights from D/L amino acids and Δ14C signatures

    Science.gov (United States)

    Walker, B. D.; Shen, Y.; Benner, R. H.; Druffel, E. R. M.

    2014-12-01

    Coastal upwelling zones are among the most productive regions in the world and play a major role in global carbon and nitrogen cycles. Recent research suggests that a substantial fraction of newly fixed organic matter is exported offshore in the form of dissolved organic matter (DOM). However, to date only a few studies have examined DOM composition in the context of production and export from upwelling systems. The ultimate fate and geochemical impact of coastal DOM exported to offshore and mesopelagic ecosystems also remains largely unknown. Between 2007-2009 we conducted a high-resolution biogeochemical time series at the Granite Canyon Marine Pollution Studies Lab in part to evaluate the seasonal production and export of DOM from the Central CA coast. Our previous work demonstrated substantial, albeit disparate, seasonal production of dissolved organic carbon and nitrogen (DOC, DON) - with high DON (and low C:N ratios) produced during upwelling and high DOC produced during summer/fall water column stratification (Walker and McCarthy, 2012). Here we present new total dissolved D/L amino acid (TDAA) and UV-oxidizable DOC radiocarbon (Δ14C) data with the goal of determining the relative sources (heterotrophic vs. autotrophic), bioavailability, microbial processing and 14C-ages of C-rich vs. N-rich DOM exported from this upwelling system. Our results suggest that C-rich DOM produced during water column stratification carries a large microbial signature (i.e. high D/L AA ratios and non-protein AA abundance), whereas N-rich DOM produced during upwelling appears to be fresh, autotrophic DOM (i.e. lowest D/L AA ratios and highest TDAA abundance). DOM Δ14C signatures also did not approximate in situ dissolved inorganic carbon (DIC), and instead were far more negative and highly correlated to water mass density. Together our results indicate a previously unrecognized source of highly labile yet pre-aged DOM potentially impacting offshore and mesopelagic ecosystems.

  17. On Mario Bunge's Definition of System and System Boundary

    Science.gov (United States)

    Cavallo, Andrew M.

    2012-01-01

    In this short paper we discuss Mario Bunge's definition of system boundary. It is quickly discovered that Bunge's definition of system and system boundary are both deficient. We thus propose new definitions, which (hopefully) improve the situation. Our definition of system boundary works off the same intuition behind Bunge's.

  18. Seasonal variability of the Ekman transport and pumping in the upwelling system off central-northern Chile (˜ 30° S) based on a high-resolution atmospheric regional model (WRF)

    Science.gov (United States)

    Bravo, Luis; Ramos, Marcel; Astudillo, Orlando; Dewitte, Boris; Goubanova, Katerina

    2016-09-01

    Two physical mechanisms can contribute to coastal upwelling in eastern boundary current systems: offshore Ekman transport due to the predominant alongshore wind stress and Ekman pumping due to the cyclonic wind stress curl, mainly caused by the abrupt decrease in wind stress (drop-off) in a cross-shore band of 100 km. This wind drop-off is thought to be an ubiquitous feature in coastal upwelling systems and to regulate the relative contribution of both mechanisms. It has been poorly studied along the central-northern Chile region because of the lack in wind measurements along the shoreline and of the relatively low resolution of the available atmospheric reanalysis. Here, the seasonal variability in Ekman transport, Ekman pumping and their relative contribution to total upwelling along the central-northern Chile region (˜ 30° S) is evaluated from a high-resolution atmospheric model simulation. As a first step, the simulation is validated from satellite observations, which indicates a realistic representation of the spatial and temporal variability of the wind along the coast by the model. The model outputs are then used to document the fine-scale structures in the wind stress and wind curl in relation to the topographic features along the coast (headlands and embayments). Both wind stress and wind curl had a clear seasonal variability with annual and semiannual components. Alongshore wind stress maximum peak occurred in spring, second increase was in fall and minimum in winter. When a threshold of -3 × 10-5 s-1 for the across-shore gradient of alongshore wind was considered to define the region from which the winds decrease toward the coast, the wind drop-off length scale varied between 8 and 45 km. The relative contribution of the coastal divergence and Ekman pumping to the vertical transport along the coast, considering the estimated wind drop-off length, indicated meridional alternation between both mechanisms, modulated by orography and the intricate

  19. Role of nutrient recycling in upwelling ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Whitledge, T E

    1979-01-01

    The regeneration of nitrogen is an important process that increases the efficiency of the upwelling ecosystem by enlarging their spatial scales. Ammonium regeneration was considered to contribute 42 to 72 percent of phytoplankton nitrogen requirements in the northwest Africa, Peru, and Baja California upwelling systems. Zooplankton are responsible for the largest portion of regenerated nitrogen; however, fish and benthic sediments may be nearly as large. Comparisons of the importance of ammonium regeneration in upwelling areas with coastal and open ocean regions indicate that the percentage contributions are similar. Future nutrient regeneration studies are needed to assess the recycling of benthic sediments, microzooplankton, gelatinous zooplankton, demersal fish, bacterioplankton, and mollusks.

  20. Spatio-Temporal Variation in Effects of Upwelling on the Fatty Acid Composition of Benthic Filter Feeders in the Southern Benguela Ecosystem: Not All Upwelling Is Equal

    Science.gov (United States)

    McQuaid, Christopher David; Noyon, Margaux

    2016-01-01

    Variability in mesoscale nearshore oceanographic conditions plays an important role in the distribution of primary production and food availability for intertidal consumers. Advection of nutrient rich waters by upwelling usually allows the proliferation of diatoms, later replaced by dinoflagellates. We examined upwelling effects on the fatty acid (FA) signature of a benthic intertidal filter feeder to identify its response to pulsed variability in food availability. The study took place in two contrasting seasons and at two upwelling and two non-upwelling sites interspersed within the southern Benguela upwelling system of South Africa. We investigated the FA composition of the adductor muscles and gonads of the mussel Mytilus galloprovincialis to assess how FA are apportioned to the different tissues and whether this changes between upwelling and non-upwelling conditions. In situ temperature loggers used to identify upwelling conditions at the four sites indicated that such events occurred only at the upwelling centres and only in summer. Tissues differed strongly, with gonads presenting a higher proportion of essential FAs. This could reflect the faster turnover rate of gonad tissue or preferential retention of specific FA for reproductive purposes. FA composition did not vary as a direct function of upwelling, but there were strong dissimilarities among sites. Upwelling influenced mussel diets at one upwelling site while at the other, the expected signature of upwelling was displaced downstream of the core of upwelling. Condition Index (CI) and Gonad Index (GI) differed among sites and were not influenced by upwelling, with GI being comparable among sites. In addition, FA proportions were consistent among sites, indicating similar food quality and quantity over time and under upwelling and non-upwelling conditions. This suggests that the influence of upwelling on the west coast of South Africa is pervasive and diffuse, rather than discrete; while nearshore

  1. Boundary Controllability of Nonlinear Fractional Integrodifferential Systems

    Directory of Open Access Journals (Sweden)

    Ahmed HamdyM

    2010-01-01

    Full Text Available Sufficient conditions for boundary controllability of nonlinear fractional integrodifferential systems in Banach space are established. The results are obtained by using fixed point theorems. We also give an application for integropartial differential equations of fractional order.

  2. Contribution of changes in opal productivity and nutrient distribution in the coastal upwelling systems to late Pliocene/early Pleistocene climate cooling

    Directory of Open Access Journals (Sweden)

    J. Etourneau

    2012-03-01

    Full Text Available The global late Pliocene/early Pleistocene cooling (~3.0–2.0 million years ago, Ma concurred with extremely high diatom and biogenic opal production in most of the major coastal upwelling regions. This phenomenon was particularly pronounced in the Benguela Upwelling System (BUS, off Namibia, where it is known as the Matuyama Diatom Maximum (MDM. Our study focuses on a new diatom silicon isotope (δ30Si record covering the MDM in the BUS. Unexpectedly, the variations in δ30Si signal follow biogenic opal content, whereby the highest δ30Si values correspond to the highest biogenic opal content. We interpret the higher δ30Si values during the MDM as a result of a stronger degree of silicate utilization in the surface waters caused by high productivity of mat-forming diatom species. This was most likely promoted by weak upwelling intensity dominating the BUS during the Plio/Pleistocene cooling combined with a large silicate supply derived from a strong Southern Ocean nutrient leakage responding to the expansion of Antarctic ice cover and the resulting stratification of the polar ocean 3.0–2.7 Ma ago. A similar scenario is hypothesized for other major coastal upwelling systems (e.g. off California during this time interval, suggesting that the efficiency of the biological carbon pump was probably sufficiently enhanced in these regions during the MDM to have significantly increased the transport of atmospheric CO2 to the deep ocean. In addition, the coeval extension of the area of surface water stratification in both the Southern Ocean and the North Pacific, which decreased CO2 release to the atmosphere, led to further enhanced atmospheric CO2 drawn-down and thus contributed significantly to late Pliocene/early Pleistocene cooling.

  3. Dehumidification of Iberia by enhanced summer upwelling

    Science.gov (United States)

    Miranda, P. M.; Costa, V.; Nogueira, M.; Semedo, A.

    2015-12-01

    Dehumidification of Iberia by enhanced summer upwelling Miranda PMA, Costa V, Semedo AIDL, Faculdade de Ciências, University of LisbonA 24-year simulation of the recent Iberian climate, using the WRF model at 9km resolution forced by ERA-Interim reanalysis (1989-2012), is analysed for the decadal evolution of the upwelling forcing coastal wind and for column integrated Precipitable water vapour (PWV). Results indicate that, unlike what was found by Bakun et al. (2009) for the Peruvian region, a statistically significant trend in the upwelling favourable (northerly) wind has been accompanied by a corresponding decrease in PWV, not only inland but also over the coastal waters. Such increase is consistent with a reinforced northerly coastal jet in the maritime boundary layer contributing to atmospheric Ekman pumping of dry continental air into the coastal region. Diagnostics of the prevalence of the Iberian thermal low following Hoinka and Castro (2003) also show a positive trend in its frequency during an extended summer period (April to September). These results are consistent with recent studies indicating an upward trend in the frequency of upwelling in SW Iberia (Alves and Miranda 2013), and may be relevant for climate change applications as an increase in coastal upwelling (Miranda et al 2013) may lead to substantial regional impacts in the subtropics. Aknowledgements: Study supported by FCT Grant RECI/GEO-MET/0380/2012Alves JMR, Miranda PMA (2013) Variability of Iberian upwelling implied by ERA-40 and ERA-Interim reanalyses, Tellus A 2013, http://dx.doi.org/10.3402/tellusa.v65i0.19245.Bakun et al (2010) Greenhouse gas, upwelling-favorable winds, and the future of coastal ocean upwelling ecosystems, Global Change Biology, doi: 10.1111/j.1365-2486.2009.02094.xHoinka KP, Castro M (2003) The Iberian Peninsula thermal low. QJRMS, 129, 1491- 1511, doi: 10.1256/qj.01.189.Miranda et al (2013) Climate change and upwelling: response of Iberian upwelling to atmospheric

  4. Environmental proteomics of microbial plankton in a highly productive coastal upwelling system

    Energy Technology Data Exchange (ETDEWEB)

    Sowell, Sarah [Oregon State University, Corvallis; Abraham, Paul E [ORNL; Shah, Manesh B [ORNL; Verberkmoes, Nathan C [ORNL; Smith, Daniel [Oregon State University, Corvallis; Barofsky, Douglas [Oregon State University, Corvallis; Giovannoni, Stephen [Oregon State University, Corvallis

    2011-01-01

    Metaproteomics is one of a suite of new approaches providing insights into the activities of microorganisms in natural environments. Proteins, the final products of gene expression, indicate cellular priorities, taking into account both transcriptional and posttranscriptional control mechanisms that control adaptive responses. Here, we report the proteomic composition of the o 1.2 lm fraction of a microbial community from Oregon coast summer surface waters, detected with two-dimensional liquid chromatography coupled with electrospray tandem mass spectrometry. Spectra corresponding to proteins involved in protein folding and biosynthesis, transport, and viral capsid structure were the most frequently detected. A total of 36% of all the detected proteins were best matches to the SAR11 clade, and other abundant coastal microbial clades were also well represented, including the Roseobacter clade (17%), oligotrophic marine gammaproteobacteria group (6%), OM43 clade (1%). Viral origins were attributed to 2.5% of proteins. In contrast to oligotrophic waters, phosphate transporters were not highly detected in this nutrient-rich system. However, transporters for amino acids, taurine, polyamines and glutamine synthetase were among the most highly detected proteins, supporting predictions that carbon and nitrogen are more limiting than phosphate in this environment. Intriguingly, one of the highly detected proteins was methanol dehydrogenase originating from the OM43 clade, providing further support for recent reports that the metabolism of one-carbon compounds by these streamlined methylotrophs might be an important feature of coastal ocean biogeochemistry.

  5. Linking predators to seasonality of upwelling: Using food web indicators and path analysis to infer trophic connections

    Science.gov (United States)

    Thompson, Sarah Ann; Sydeman, William J.; Santora, Jarrod A.; Black, Bryan A.; Suryan, Robert M.; Calambokidis, John; Peterson, William T.; Bograd, Steven J.

    2012-08-01

    Upwelling in eastern boundary current systems is a primary driver of ecosystem productivity. Typically, peak upwelling occurs during spring and summer, but winter upwelling may also be important to ecosystem functions. In this study, we investigated the hypothesis that winter and spring/summer upwelling, operating through indirect trophic interactions, are important to a suite of top predators in the California Current. To test this hypothesis, we collated information on upwelling, chlorophyll-a concentrations, zooplankton and forage fish, and related these to predator responses including rockfish growth, salmon abundance, seabird productivity and phenology (timing of egg-laying), and whale abundance. Seabird diets served in part as food web indicators. We modeled pathways of response using path analysis and tested for significance of the dominant paths with multiple regression. We found support for the hypothesis that relationships between upwelling and top predator variables were mediated primarily by intermediate trophic levels. Both winter and summer upwelling were important in path models, as were intermediate lower and mid trophic level functional groups represented by chlorophyll-a, zooplankton, and forage fish. Significant pathways of response explained from 50% to 80% of the variation of seabird (Cassin's auklet (Ptychoramphus aleuticus) and common murre (Uria aalge)), humpback whale (Megaptera novaeangliae) and Chinook salmon (Oncorhynchus tshawytscha) dependent variables, whereas splitnose rockfish (Sebastes diploproa) showed no significant response pathways. Upwelling and trophic responses for salmon were established for both the year of ocean entry and the year of return, with zooplankton important in the year of ocean entry and forage fish important in the year of return. This study provides one of the first comparative investigations between upwelling and predators, from fish to marine mammals and birds within a geographically restricted area

  6. ON THE STABILITY BOUNDARY OF HAMILTONIAN SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    QI Zhao-hui(齐朝晖); Alexander P. Seyranian

    2002-01-01

    The criterion for the points in the parameter space being on the stability boundary of linear Hamiltonian system depending on arbitrary numbers of parameters was given, through the sensitivity analysis of eigenvalues and eigenvectors. The results show that multiple eigenvalues with Jordan chain take a very important role in the stability of Hamiltonian systems.

  7. Meteorological constraints on oceanic halocarbons above the Peruvian Upwelling

    Directory of Open Access Journals (Sweden)

    S. Fuhlbrügge

    2015-07-01

    Full Text Available Halogenated very short lived substances (VSLS are naturally produced in the ocean and emitted to the atmosphere. Recently, oceanic upwelling regions in the tropical East Atlantic were identified as strong sources of brominated halocarbons to the atmosphere. During a cruise of R/V METEOR in December 2012 the oceanic sources and emissions of various halogenated trace gases and their mixing ratios in the marine atmospheric boundary layer (MABL were investigated above the Peruvian Upwelling for the first time. This study presents novel observations of the three VSLS bromoform, dibromomethane and methyl iodide together with high resolution meteorological measurements and Lagrangian transport modelling. Although relatively low oceanic emissions were observed, except for methyl iodide, surface atmospheric abundances were elevated. Radiosonde launches during the cruise revealed a low, stable MABL and a distinct trade inversion above acting both as strong barriers for convection and trace gas transport in this region. Significant correlations between observed atmospheric VSLS abundances, sea surface temperature, relative humidity and MABL height were found. We used a simple source-loss estimate to identify the contribution of oceanic emissions to observed atmospheric concentrations which revealed that the observed marine VSLS abundances were dominated by horizontal advection below the trade inversion. The observed VSLS variations can be explained by the low emissions and their accumulation under different MABL and trade inversion conditions. This study confirms the importance of oceanic upwelling and trade wind systems on creating effective transport barriers in the lower atmosphere controlling the distribution of VSLS abundances above ocean upwelling regions.

  8. Meteorological constraints on oceanic halocarbons above the Peruvian upwelling

    Science.gov (United States)

    Fuhlbrügge, Steffen; Quack, Birgit; Atlas, Elliot; Fiehn, Alina; Hepach, Helmke; Krüger, Kirstin

    2016-09-01

    During a cruise of R/V METEOR in December 2012 the oceanic sources and emissions of various halogenated trace gases and their mixing ratios in the marine atmospheric boundary layer (MABL) were investigated above the Peruvian upwelling. This study presents novel observations of the three very short lived substances (VSLSs) - bromoform, dibromomethane and methyl iodide - together with high-resolution meteorological measurements, Lagrangian transport and source-loss calculations. Oceanic emissions of bromoform and dibromomethane were relatively low compared to other upwelling regions, while those for methyl iodide were very high. Radiosonde launches during the cruise revealed a low, stable MABL and a distinct trade inversion above acting as strong barriers for convection and vertical transport of trace gases in this region. Observed atmospheric VSLS abundances, sea surface temperature, relative humidity and MABL height correlated well during the cruise. We used a simple source-loss estimate to quantify the contribution of oceanic emissions along the cruise track to the observed atmospheric concentrations. This analysis showed that averaged, instantaneous emissions could not support the observed atmospheric mixing ratios of VSLSs and that the marine background abundances below the trade inversion were significantly influenced by advection of regional sources. Adding to this background, the observed maximum emissions of halocarbons in the coastal upwelling could explain the high atmospheric VSLS concentrations in combination with their accumulation under the distinct MABL and trade inversions. Stronger emissions along the nearshore coastline likely added to the elevated abundances under the steady atmospheric conditions. This study underscores the importance of oceanic upwelling and trade wind systems on the atmospheric distribution of marine VSLS emissions.

  9. Solid-boundary treatment for moment systems

    Science.gov (United States)

    Khieu, Loc Huu

    Hyperbolic-relaxation systems for describing fluid flow, such as Grad's 13-moment (13M) system, are an alternative to the systems generated by the Chapman-Enskog expansion, which include derivatives of increasing order. The former have a number of numerical advantages stemming from the compactness of their spatial operator. They have been demonstrated to be suited for subsonic and transonic flow. In this dissertation we explore the solid-wall boundary conditions that have to supplement these moment systems. Starting from the boundary treatment proposed by Grad, we first remove an inconsistency in his theory that would lead to ambiguous results. We formulate two boundary conditions, 1— C and 2—C, containing one and two parameters, respectively; these are used to satisfy the non-penetration condition in 1— C and 2—C, and an additional normalization condition in 2—C. The boundary conditions are implemented in a computational code based on the 13M system. In order to study the accuracy of the new boundary condition we also develop a benchmark code based on the Boltzmann equation with Bhatnagar—Gross—Krook collision model (BGK equation), and implement the same boundary conditions in there. Both codes include a Finite-Volume (FV) and a Discontinuous Galerkin (DG) option (piecewise-linear discretization). These codes are used to solve three types of flow problems: low-speed Couette flow with zero difference in wall temperatures, zero-speed Couette flow with appreciable wall-temperature difference, and low-speed Poiseuille flow. The Knudsen number ranged from 0.01 to 10. For these problems, incompressible Navier—Stokes—Fourier (NSF) solutions are available for comparison (except for the temperature-driven flow); here the boundary condition used is a first-or second-order velocity-slip boundary condition. The numerical experiments indicate that the 13M/1—C system consistently predicts a flow velocity at the wall that is closer to the BGK solution than

  10. Boundary Value Problems for Boussinesq Type Systems

    Energy Technology Data Exchange (ETDEWEB)

    Fokas, A. S. [Cambridge University, Department of Applied Mathematics and Theoretical Physics (United Kingdom)], E-mail: t.fokas@damtp.cam.ac.uk; Pelloni, B. [University of Reading, Department of Mathematics (United Kingdom)], E-mail: b.pelloni@rdg.ac.uk

    2005-02-15

    We characterise the boundary conditions that yield a linearly well posed problem for the so-called KdV-KdV system and for the classical Boussinesq system. Each of them is a system of two evolution PDEs modelling two-way propagation of water waves. We study these problems with the spatial variable in either the half-line or in a finite interval. The results are obtained by extending a spectral transform approach, recently developed for the analysis of scalar evolution PDEs, to the case of systems of PDEs.The knowledge of the boundary conditions that should be imposed in order for the problem to be linearly well posed can be used to obtain an integral representation of the solution. This knowledge is also necessary in order to conduct numerical simulations for the fully nonlinear systems.

  11. Air-sea exchange of CO2 at a Northern California coastal site along the California Current upwelling system

    Directory of Open Access Journals (Sweden)

    W. C. Oechel

    2012-12-01

    Full Text Available Uncertainty in the air-sea CO2 exchange (CO2 flux in coastal upwelling zones is attributed to high temporal variability, which is caused by changes in ocean currents. Upwelling transports heterotrophic, CO2 enriched water to the surface and releases CO2 to the atmosphere, whereas the presence of nutrient-rich water at the surface supports high primary production and atmospheric CO2 uptake. To quantify the effects of upwelling on CO2 fluxes, we measured CO2 flux at a coastal upwelling site off of Bodega Bay, California, during the summer of 2007 and the fall of 2008 using the eddy covariance technique and the bulk method with pCO2 measurements from November 2010 to July 2011. Variations in sea surface temperatures (SST and alongshore wind speeds suggest that the measurement period in 2007 coincided with a typical early-summer upwelling period and the measurement period in 2008 was during a typical fall relaxation period. A strong source of CO2 (~1.5 ± 7 SD (standard deviation g C m−2 day−1 from the ocean to the atmosphere during the upwelling period was concurrent with high salinity, low SST, and low chlorophyll density. In contrast, a weak source of CO2 flux (~0.2 ± 3 SD g C m−2 day−1 was observed with low salinity, high SST and high chlorophyll density during the relaxation period. Similarly, the sink and source balance of CO2flux was highly related to salinity and SST during the pCO2 measurement periods; high salinity and low SST corresponded to high pCO2, and vice versa. We estimated that the coastal area off Bodega Bay was likely a source of CO2 to the atmosphere based on the following conclusions: (1 the overall CO2 flux estimated from both eddy covariance and pCO2 measurements showed a source of CO2; (2 although the relaxation period during the 2008 measurements were favorable to CO2 uptake, CO2 flux during this period was still a slight source, (3 salinity and SST were found to be good predictors of the CO2 flux for both eddy

  12. Boundary layer control of rotating convection systems.

    Science.gov (United States)

    King, Eric M; Stellmach, Stephan; Noir, Jerome; Hansen, Ulrich; Aurnou, Jonathan M

    2009-01-15

    Turbulent rotating convection controls many observed features of stars and planets, such as magnetic fields, atmospheric jets and emitted heat flux patterns. It has long been argued that the influence of rotation on turbulent convection dynamics is governed by the ratio of the relevant global-scale forces: the Coriolis force and the buoyancy force. Here, however, we present results from laboratory and numerical experiments which exhibit transitions between rotationally dominated and non-rotating behaviour that are not determined by this global force balance. Instead, the transition is controlled by the relative thicknesses of the thermal (non-rotating) and Ekman (rotating) boundary layers. We formulate a predictive description of the transition between the two regimes on the basis of the competition between these two boundary layers. This transition scaling theory unifies the disparate results of an extensive array of previous experiments, and is broadly applicable to natural convection systems.

  13. Global Weak Solutions of Initial Boundary Value Problem for Boltzmann-Poisson System with Absorbing Boundary

    Institute of Scientific and Technical Information of China (English)

    崔国忠; 张志平; 等

    2002-01-01

    This paper deals with the initial boundary value value problem for the Boltzmann-Poisson system ,which arises in semiconductor physics,with absorbing boundary.The global existence of weak solutions is proved by using the stability of velocity averages and the compactness results on L1-theory under weaker conditons on initial boundary values.

  14. LOCAL EXACT BOUNDARY CONTROLLABILITY FOR A CLASS OFQUASILINEAR HYPERBOLIC SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    For a class of mixed initial-boundary value problem for general quasilinear hyperbolic systems, this paper establishes the local exact boundary controllability with boundary controls only acting on one end. As an application, the authors show the local exact boundary controllability for a kind of nonlinear vibrating string problem.

  15. Impact of boundary regions on the interior circulation of the California Current System in a regional modeling framework

    Science.gov (United States)

    Veneziani, M.; Edwards, C.; Moore, A.

    2008-12-01

    We use the Regional Ocean Modeling System (ROMS) to model the circulation of the California Current System (CCS) using ECCO-GODAE products to force the model at the open boundaries of the domain. We investigate the impact that lateral boundary forcing (and the boundary region in general) has on particular metrics of the interior circulation by adopting both an adjoint model and a traditional sensitivity approach. Adjoint methods are naturally suited to sensitivity studies as they provide the direct dependencies of circulation metrics on uncertainties of the model initial conditions, surface and lateral external forcing, and model parameters, but their results are only valid within the time scale during which the linearity assumption underlying adjoint models can be considered to hold. More traditional sensitivity studies must be conducted to investigate longer time scales. We describe the adjoint model results for two metrics that represent the upwelling processes of the Central California region and the mean sea level field of the coastal circulation, respectively. The spatial distribution of the adjoint sensitivity fields allows us to quantify the contribution of the boundary regions over a biweekly time scale. We investigate longer time scales by adopting two methods: 1) apply different ECCO products at the open boundaries and evaluate mean stratification changes in the CalCOFI coastal region; 2) release passive tracers at the boundaries and calculate ventilation time scales and pathways from the boundary areas to the CCS interior.

  16. Salinity inversions in the thermocline under upwelling favorable winds

    Science.gov (United States)

    Burchard, Hans; Basdurak, N. Berkay; Gräwe, Ulf; Knoll, Michaela; Mohrholz, Volker; Müller, Selina

    2017-02-01

    This paper discusses and explains the phenomenon of salinity inversions in the thermocline offshore from an upwelling region during upwelling favorable winds. Using the nontidal central Baltic Sea as an easily accessible natural laboratory, high-resolution transect and station observations in the upper layers are analyzed. The data show local salinity minima in the strongly stratified seasonal thermocline during summer conditions under the influence of upwelling favorable wind. A simple analytical box model using parameters (including variation by means of a Monte Carlo method) estimated from a hindcast model for the Baltic Sea is constructed to explain the observations. As a result, upwelled water with high salinity and low temperature is warmed up due to downward surface heat fluxes while it is transported offshore by the Ekman transport. The warming of upwelled surface water allows maintenance of stable stratification despite the destabilizing salinity stratification, such that local salinity minima in the thermocline can be generated. Inspection of published observations from the Benguela, Peruvian, and eastern tropical North Atlantic upwelling systems shows that also there salinity inversions occur in the thermocline, but in these cases thermocline salinity shows local maxima, since upwelled water has a lower salinity than the surface water. It is hypothesized that thermocline salinity inversions should generally occur offshore from upwelling regions whenever winds are steady enough and surface warming is sufficiently strong.

  17. The relationship between Arabian Sea upwelling and Indian monsoon revisited

    Directory of Open Access Journals (Sweden)

    X. Yi

    2015-11-01

    Full Text Available Studies based on upwelling indices (sediment records, sea-surface temperature and wind suggest that upwelling along the western coast of Arabian Sea is strongly affected by the Indian summer monsoon (ISM. In order to examine this relationship directly, we employ the vertical water mass transport produced by the eddy-resolving global ocean simulation STORM driven by meteorological reanalysis over the last 61 years. With its very high spatial resolution (10 km, STORM allows us to identify characteristics of the upwelling system. We analyze the co-variability between upwelling and meteorological and oceanic variables from 1950 to 2010. The analyses reveal high interannual correlations between coastal upwelling and along-shore wind-stress (r=0.73 as well as with sea-surface temperature (r0.83. However, the correlation between the upwelling and the ISM is small and other factors might contribute to the upwelling variability. In addition, no long-term trend is detected in our modeled upwelling time series.

  18. A comparison of benthic foraminiferal Mn / Ca and sedimentary Mn / Al as proxies of relative bottom-water oxygenation in the low-latitude NE Atlantic upwelling system

    Science.gov (United States)

    McKay, C. L.; Groeneveld, J.; Filipsson, H. L.; Gallego-Torres, D.; Whitehouse, M. J.; Toyofuku, T.; Romero, O. E.

    2015-09-01

    Trace element incorporation into foraminiferal shells (tests) is governed by physical and chemical conditions of the surrounding marine environment, and therefore foraminiferal geochemistry provides a means of palaeo-oceanographic reconstructions. With the availability of high-spatial-resolution instrumentation with high precision, foraminiferal geochemistry has become a major research topic over recent years. However, reconstructions of past bottom-water oxygenation using foraminiferal tests remain in their infancy. In this study we explore the potential of using Mn / Ca determined by secondary ion mass spectrometry (SIMS) as well as by flow-through inductively coupled plasma optical emission spectroscopy (FT-ICP-OES) in the benthic foraminiferal species Eubuliminella exilis as a proxy for recording changes in bottom-water oxygen conditions in the low-latitude NE Atlantic upwelling system. Furthermore, we compare the SIMS and FT-ICP-OES results with published Mn sediment bulk measurements from the same sediment core. This is the first time that benthic foraminiferal Mn / Ca is directly compared with Mn bulk measurements, which largely agree on the former oxygen conditions. Samples were selected to include different productivity regimes related to Marine Isotope Stage 3 (35-28 ka), the Last Glacial Maximum (28-19 ka), Heinrich Event 1 (18-15.5 ka), Bølling Allerød (15.5-13.5 ka) and the Younger Dryas (13.5-11.5 ka). Foraminiferal Mn / Ca determined by SIMS and FT-ICP-OES is comparable. Mn / Ca was higher during periods with high primary productivity, such as during the Younger Dryas, which indicates low-oxygen conditions. This is further supported by the benthic foraminiferal faunal composition. Our results highlight the proxy potential of Mn / Ca in benthic foraminifera from upwelling systems for reconstructing past variations in oxygen conditions of the sea floor environment as well as the need to use it in combination with other proxy records such as faunal

  19. Salinity driven oceanographic upwelling

    Science.gov (United States)

    Johnson, D.H.

    1984-08-30

    The salinity driven oceanographic upwelling is maintained in a mariculture device that includes a long main duct in the general shape of a cylinder having perforated cover plates at each end. The mariculture device is suspended vertically in the ocean such that one end of the main duct is in surface water and the other end in relatively deep water that is cold, nutrient rich and relatively fresh in comparison to the surface water which is relatively warm, relatively nutrient deficient and relatively saline. A plurality of elongated flow segregating tubes are disposed in the main duct and extend from the upper cover plate beyond the lower cover plate into a lower manifold plate. The lower manifold plate is spaced from the lower cover plate to define a deep water fluid flow path to the interior space of the main duct. Spacer tubes extend from the upper cover plate and communicate with the interior space of the main duct. The spacer tubes are received in an upper manifold plate spaced from the upper cover plate to define a surface water fluid flow path into the flow segregating tubes. A surface water-deep water counterflow is thus established with deep water flowing upwardly through the main duct interior for discharge beyond the upper manifold plate while surface water flows downwardly through the flow segregating tubes for discharge below the lower manifold plate. During such counterflow heat is transferred from the downflowing warm water to the upflowing cold water. The flow is maintained by the difference in density between the deep water and the surface water due to their differences in salinity. The upwelling of nutrient rich deep water is used for marifarming by fertilizing the nutrient deficient surface water. 1 fig.

  20. Surface free energy for systems with integrable boundary conditions

    Energy Technology Data Exchange (ETDEWEB)

    Goehmann, Frank [Fachbereich C-Physik, Bergische Universitaet Wuppertal, 42097 Wuppertal (Germany); Bortz, Michael [Department of Theoretical Physics, Australian National University, Canberra ACT 0200 (Australia); Frahm, Holger [Institut fuer Theoretische Physik, Universitaet Hannover, 30167 Hannover (Germany)

    2005-12-16

    The surface free energy is the difference between the free energies for a system with open boundary conditions and the same system with periodic boundary conditions. We use the quantum transfer matrix formalism to express the surface free energy in the thermodynamic limit of systems with integrable boundary conditions as a matrix element of certain projection operators. Specializing to the XXZ spin-1/2 chain we introduce a novel 'finite temperature boundary operator' which characterizes the thermodynamical properties of surfaces related to integrable boundary conditions.

  1. Biogenic halocarbons from coastal oceanic upwelling regions as tropospheric halogen source

    Science.gov (United States)

    Krüger, Kirstin; Fuhlbrügge, Steffen; Hepach, Helmke; Fiehn, Alina; Atlas, Elliot; Quack, Birgit

    2016-04-01

    Halogenated very short lived substances (VSLS) are naturally produced in the ocean and emitted to the atmosphere. Recently, oceanic upwelling regions in the tropical East Atlantic were identified as strong sources of brominated halocarbons to the troposphere. During a cruise of R/V METEOR in December 2012 the oceanic sources and emissions of various halogenated trace gases and their mixing ratios in the marine atmospheric boundary layer (MABL) were investigated above the Peruvian Upwelling for the first time. This study presents novel observations of the three VSLS bromoform, dibromomethane and methyl iodide together with high resolution meteorological measurements and Lagrangian transport modelling. Although relatively low oceanic emissions were observed, except for methyl iodide, surface atmospheric abundances were elevated. Radiosonde launches during the cruise revealed a low, stable MABL and a distinct trade inversion above acting both as strong barriers for convection and trace gas transport in this region. Significant correlations between observed atmospheric VSLS abundances, sea surface temperature, relative humidity and MABL height were found. We used a simple source-loss estimate to identify the contribution of oceanic emissions to observed atmospheric concentrations which revealed that the observed marine VSLS abundances were dominated by horizontal advection below the trade inversion. The observed VSLS variations can be explained by the low emissions and their accumulation under different MABL and trade inversion conditions. Finally, observations from a second Peruvian Upwelling cruise with R/V SONNE during El Nino in October 2015 will be compared to highlight the role of different El Nino Southern Oscillation conditions. This study confirms the importance of coastal oceanic upwelling and trade wind systems on creating effective transport barriers in the lowermost atmosphere controlling the distribution of VSLS abundances above coastal ocean upwelling

  2. Patterns in passive optical systems with boundary effects

    Institute of Scientific and Technical Information of China (English)

    李春萍; 沈柯

    2003-01-01

    Pattern formation is closely related to system boundary conditions in nonlinear dynamic systems, apart from the system control parameters. To avoid complexity, system boundary conditions are usually considered to be infinite or periodic, and the initial conditions spatially homogeneous. But it is not always the case in real situations, or sometimes periodic boundary conditions are not exact. To show the important and interesting boundary effects in real pattern formation, we suggest a simple universal boundary condition in a typical optical pattern formation system. Numerical simulations of the passive optical system show that pattern characteristics such as distribution symmetry, peak number,structure strength, evolution course and stability are all greatly influenced by the system boundary conditions.

  3. ON STABILITY BOUNDARY OF LINEAR MULTI-PARAMETER HAMILTONIAN SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    Qi Zhaohui(齐朝晖); Alexander P.Seyranian

    2002-01-01

    In this paper an approximate equation is derived to describe smoothparts of the stability boundary for linear Hamiltonian systems, depending on arbitrarynumber of parameters. With this equation, we can obtain parameters correspondingto the stability boundary, as well as to the stability and instability domains, pro-vided that one point on the stability boundary is known. Then differential equationsdescribing the evolution of eigenvalues and eigenvectors along a curve on the sta-bility boundary surface are derived. These equations also allow us to obtain curvesbelonging to the stability boundary. Applications to linear gyroscopic systems areconsidered and studied with examples.

  4. Modelling the CO2 atmosphere-ocean flux in the upwelling zones using radiative transfer tools

    Science.gov (United States)

    Krapivin, Vladimir F.; Varotsos, Costas A.

    2016-12-01

    An advanced mathematical model of the radiation forcing on the ocean surface is proposed for the assessment of the CO2 fluxes between atmosphere and ocean boundary in the upwelling zones. Two types of the upwelling are considered: coastal and local in the open ocean that are closely associated with changes in solar irradiance. The proposed model takes into account the maximal number of the carbon fluxes in the upwelling ecosystem considering that in the latter the only original source of energy and matter for all forms of life is the energy of the solar radiation. The vertical structure of the upwelling zone is represented by four levels: the upper mixed layer above the thermocline, the intermediate photic layer below the thermocline, the deep ocean and the near-bottom layer. Peruvian upwelling and typical local upwelling of tropical pelagic region are considered as examples for the model calculations.

  5. Zonation of bacterioplankton communities along aging upwelled water in the northern Benguela upwelling

    Directory of Open Access Journals (Sweden)

    Benjamin eBergen

    2015-06-01

    Full Text Available Upwelling areas are shaped by enhanced primary production in surface waters, accompanied by a well-investigated planktonic succession. Although bacteria play an important role in biogeochemical cycles of upwelling systems, little is known about bacterial community composition and its development during upwelling events. The aim of this study was to investigate the succession of bacterial assemblages in aging upwelled water of the Benguela upwelling from coastal to offshore sites. Water from the upper mixed layer at 12 stations was sampled along two transects from the origin of the upwelling to a distance of 220 km. 16S rRNA gene amplicon sequencing was then used in a bacterial diversity analysis and major bacterial taxa were quantified by catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH. Additionally, bacterial cell numbers and bacterial production were assessed . Community statistical analysis revealed a reproducible zonation along the two transects, with four clusters of significantly different microbial assemblages. Clustering was mainly driven by phytoplankton composition and abundance. Similar to the temporal succession that occurs during phytoplankton blooms in temperate coastal waters, operational taxonomic units (OTUs affiliated with Bacteroidetes and Gammaproteobacteria were dominant during algal blooming whereas Pelagibacterales were highly abundant in regions with low algal abundance. The most dominant heterotrophic OTU (9% of all reads was affiliated with Pelagibacterales and showed a strong negative correlation with phytoplankton. By contrast, the second most abundant heterotrophic OTU (6% of all reads was affiliated with the phylum Verrucomicrobia and correlated positively with phytoplankton. Together with the close relation of bacterial production and phytoplankton abundance, our results showed that bacterial community dynamics is strongly driven by the development and composition of the phytoplankton

  6. In situ measurements and model estimates of NO3 and NH4 uptake by different phytoplankton size fractions in the southern Benguela upwelling system.

    Directory of Open Access Journals (Sweden)

    Josephine Ffion Atkins

    2016-10-01

    Full Text Available Bulk measurements can be made of phytoplankton standing stocks on a quasi-synoptic scale but it is more difficult to measure rates of production and nutrient uptake. We present a method to estimate nitrogen uptake rates in productive coastal environments. We use observed phytoplankton cell size distributions and ambient nitrogen concentrations to calculate uptake rates of nitrate, ammonium and total nitrogen by different size fractions of diverse phytoplankton communities in a coastal upwelling system. The data are disaggregated into size categories, uptake rates are calculated and these uptake rates are reaggregated to obtain bulk estimates. The calculations are applied to 72 natural assemblages for which nitrogen uptake rates and particle size distributions were measured textit in situ . The calculated values of total N uptake integrated across all size classes are similar to those of textit in situ bulk measurements (N slope=0.90, (NH _ 4 slope=0.96 indicating dependence of NH _ 4 and total N uptake on ambient N concentrations and cell size distributions of the phytoplankton assemblages. NO _ 3 uptake was less well explained by cell size and ambient concentrations, but regressions between measured and estimated rates were still significant. The results suggest that net nitrogen dynamics can be quantified at an assemblage scale using size dependencies of Michaelis-Menten uptake parameters. These methods can be applied to particle size distributions that have been routinely measured in eutrophic systems to estimate and subsequently analyse variability in nitrogen uptake.

  7. A system boundary identification method for life cycle assessment

    DEFF Research Database (Denmark)

    Li, Tao; Zhang, Hongchao; Liu, Zhichao;

    2014-01-01

    Life cycle assessment (LCA) is a useful tool for quantifying the overall environmental impacts of a product, process, or service. The scientific scope and boundary definition are important to ensure the accuracy of LCA results. Defining the boundary in LCA is difficult and there are no commonly...... accepted scientific methods yet. The objective of this research is to present a comprehensive discussion of system boundaries in LCA and to develop an appropriate boundary delimitation method.A product system is partitioned into the primary system and interrelated subsystems. The hierarchical relationship......, technical, geographical and temporal dimensions are presented to limit the boundaries of LCA. An algorithm is developed to identify an appropriate boundary by searching the process tree and evaluating the environmental impact contribution of each process while it is added into the studied system...

  8. Boundary control of nonlinear coupled heat systems using backstepping

    KAUST Repository

    Bendevis, Paul

    2016-10-20

    A state feedback boundary controller is designed for a 2D coupled PDE system modelling heat transfer in a membrane distillation system for water desalination. Fluid is separated into two compartments with nonlinear coupling at a membrane boundary. The controller sets the temperature on one boundary in order to track a temperature difference across the membrane boundary. The control objective is achieved by an extension of backstepping methods to these coupled equations. Stability of the target system via Lyapunov like methods, and the invertibility of the integral transformation are used to show the stability of the tracking error.

  9. Micro-phytoplankton community structure in the coastal upwelling zone off Concepción (central Chile): Annual and inter-annual fluctuations in a highly dynamic environment

    Science.gov (United States)

    Anabalón, V.; Morales, C. E.; González, H. E.; Menschel, E.; Schneider, W.; Hormazabal, S.; Valencia, L.; Escribano, R.

    2016-12-01

    An intensification of upwelling-favorable winds in recent decades has been detected in some of the main eastern boundary current systems, especially at higher latitudes, but the response of coastal phytoplankton communities in the Humboldt Current System (HCS) remains unknown. At higher latitudes in the HCS (35-40°S), strong seasonality in wind-driven upwelling during spring-summer coincides with an annual increase in coastal chlorophyll-a and primary production, and a dominance of micro-phytoplankton. In order to understand the effects of potential upwelling intensification on the micro-phytoplankton community in this region, annual and inter-annual variability in its structure (total and taxa-specific abundance and biomass) and its association with oceanographic fluctuations were analyzed using in situ time series data (2002-2009) from a shelf station off Concepcion (36.5°S). At the annual scale, total mean abundance and biomass, attributed to a few dominant diatom taxa, were at least one order of magnitude greater during spring-summer than autumn-winter, in association with changes in upwelling and surface salinity and temperature, whereas macro-nutrient concentrations remained relatively high all the year. At the inter-annual scale, total abundance and biomass decreased during the upwelling season of the 2006-2009 period compared with the 2002-2006 period, notably due to lower abundances of Skeletonema and Leptocylindrus, but the relative dominance of a few taxa was maintained. The 2006-2009 period was characterized by higher upwelling intensity, colder and higher salinity waters, and changes in nutrient concentrations and ratios compared with the first period. The inter-annual changes in the micro-phytoplankton community were mostly associated with changes in surface salinity and temperature (changes in upwelling intensity) but also with changes in Si/N and N/P, which relate to other land-derived processes.

  10. Spatio-temporal variation of microphytoplankton in the upwelling system of the south-eastern Arabian Sea during the summer monsoon of 2009

    Directory of Open Access Journals (Sweden)

    Lathika Cicily Thomas

    2013-02-01

    Full Text Available The phytoplankton standing crop was assessed in detail along the South Eastern Arabian Sea (SEAS during the different phases of coastal upwelling in 2009. During phase 1 intense upwelling was observed along the southern transects(8°N and 8.5°N. The maximum chlorophyll a concentration (22.7 mg m-3 was observedin the coastal waters off Thiruvananthapuram (8.5°N. Further north there was no signature of upwelling, with extensive Trichodesmium erythraeum blooms. Diatoms dominated in these upwelling regions with thecentric diatom Chaetoceros curvisetus being the dominant species along the 8°N transect. Along the 8.5°N transect pennate diatoms like Nitzschia seriata and Pseudo-nitzschia sp. dominated. Duringphase 2, upwelling of varying intensity was observed throughout the study area with maximum chlorophyll a concentrations along the 9°N transect (25 mg m-3 with Chaetoceros curvisetus as the dominantphytoplankton. Along the 8.5°N transect pennate diatoms during phase 1 were replaced by centric diatoms like Chaetoceros sp. The presence of solitary pennate diatoms Amphora sp. and Navicula sp.were significant in the waters off Kochi. Upwelling was waning during phase 3 and was confined to the coastal waters of the southern transects with the highest chlorophyll a concentration of 11.2 mg m-3. Along withdiatoms, dinoflagellate cell densities increased in phases 2 and 3. In the northern transects (9°N and 10°N the proportion of dinoflagellates was comparatively higher and was represented mainly by Protoperidinium spp.

  11. Boundary Layer to a System of Viscous Hyperbolic Conservation Laws

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In this paper, we investigate the large-time behavior of solutions to the initial-boundary value problem for nxn hyperbolic system of conservation laws with artificial viscosity in the half line (0, ∞). We first show that a boundary layer exists if the corresponding hyperbolic part contains at least one characteristic field with negative propagation speed. We further show that such boundary layer is nonlinearly stable under small initial perturbation. The proofs are given by an elementary energy method.

  12. Rocket Experiment For Neutral Upwelling

    Science.gov (United States)

    Kenward, D. R.; Lessard, M.

    2015-12-01

    Observations from the CHAMP satellite from 2004 show relatively small scale heating in the thermosphere. Several different mechanisms have been proposed to explain this phenomenon. The RENU 2 rocket mission includes a suite of 14 instruments which will acquire data to help understand processes involved in neutral upwelling in the cusp. Neutral, ion, and electron measurements will be made to provide an assessment of the upwelling process. SUPERDarn measurements of large- scale Joule heating in the cusp during overflight will also be acquired. Small-scale data which could possibly be associated with Alfvén waves, will be acquired using onboard electric field measurements. In-situ measurement of precipitating electrons and all other measurements will be used in thermodynamic and electrodynamic models for comparison to the observed upwelling.

  13. A model-based insight into the coupling of nitrogen and sulfur cycles in a coastal upwelling system

    DEFF Research Database (Denmark)

    Muchamad, Al Azhar; Canfield, Donald Eugene; Fennel, Katja;

    2014-01-01

    detritus, to quantify the nitrogen and sulfur cycles in the Chilean OMZ. A new biogeochemical submodule was developed and coupled to the Regional Ocean Model System (ROMS). The model results generally agree with the observed distribution of reactive species and the measured process rates. Modeled...

  14. Emergy analysis of coastal systems influenced by upwelling in northern Chile: Estimation of ecological-economic sustainability at multiple scales

    Science.gov (United States)

    Numerous studies carried out in a variety of environments have suggested that coastal marine systems generate a variety of goods and services for humanity. However, in recent decades there has been a marked degradation of these ecosystems, as well as over-exploitation of natural ...

  15. Parameter identification of stochastic diffusion systems with unknown boundary conditions

    NARCIS (Netherlands)

    Aihara, Shin Ichi; Bagchi, Arunabha

    2013-01-01

    This paper treats the filtering and parameter identification for the stochastic diffusion systems with unknown boundary conditions. The physical situation of the unknown boundary conditions can be found in many industrial problems,i.g., the salt concentration model of the river Rhine is a typical ex

  16. Experiments with Seasonal Forecasts of ocean conditions for the Northern region of the California Current upwelling system

    Science.gov (United States)

    Siedlecki, Samantha A.; Kaplan, Isaac C.; Hermann, Albert J.; Nguyen, Thanh Tam; Bond, Nicholas A.; Newton, Jan A.; Williams, Gregory D.; Peterson, William T.; Alin, Simone R.; Feely, Richard A.

    2016-06-01

    Resource managers at the state, federal, and tribal levels make decisions on a weekly to quarterly basis, and fishers operate on a similar timeframe. To determine the potential of a support tool for these efforts, a seasonal forecast system is experimented with here. JISAO’s Seasonal Coastal Ocean Prediction of the Ecosystem (J-SCOPE) features dynamical downscaling of regional ocean conditions in Washington and Oregon waters using a combination of a high-resolution regional model with biogeochemistry and forecasts from NOAA’s Climate Forecast System (CFS). Model performance and predictability were examined for sea surface temperature (SST), bottom temperature, bottom oxygen, pH, and aragonite saturation state through model hindcasts, reforecast, and forecast comparisons with observations. Results indicate J-SCOPE forecasts have measurable skill on seasonal timescales. Experiments suggest that seasonal forecasting of ocean conditions important for fisheries is possible with the right combination of components. Those components include regional predictability on seasonal timescales of the physical environment from a large-scale model, a high-resolution regional model with biogeochemistry that simulates seasonal conditions in hindcasts, a relationship with local stakeholders, and a real-time observational network. Multiple efforts and approaches in different regions would advance knowledge to provide additional tools to fishers and other stakeholders.

  17. Inverse Boundary Problems for Systems in Two Dimensions

    CERN Document Server

    Albin, Pierre; Tzou, Leo; Uhlmann, Gunther

    2011-01-01

    We prove identification of coefficients up to gauge by Cauchy data at the boundary for elliptic systems on oriented compact surfaces with boundary or domains of $\\mathbb{C}$. In the geometric setting, we fix a Riemann surface with boundary, and consider both a Dirac-type operator plus potential acting on sections of a Clifford bundle and a connection Laplacian plus potential (i.e. Schr\\"odinger Laplacian with external Yang-Mills field) acting on sections of a Hermitian bundle. In either case we show that the Cauchy data determines both the connection and the potential up to a natural gauge transformation: conjugation by an endomorphism of the bundle which is the identity at the boundary. For domains of $\\mathbb{C}$, we recover zeroth order terms up to gauge from Cauchy data at the boundary in first order elliptic systems.

  18. Boundary Controllability of Integrodifferential Systems in Banach Spaces

    Indian Academy of Sciences (India)

    K Balachandran; E R Anandhi

    2001-02-01

    Sufficient conditions for boundary controllability of integrodifferential systems in Banach spaces are established. The results are obtained by using the strongly continuous semigroup theory and the Banach contraction principle. Examples are provided to illustrate the theory.

  19. The noncommutative Choquet boundary III: Operator systems in matrix algebras

    CERN Document Server

    Arveson, William

    2008-01-01

    We classify operator systems $S\\subseteq \\mathcal B(H)$ that act on finite dimensional Hilbert spaces by making use of the noncommutative Choquet boundary. S is said to be {\\em reduced} when its boundary ideal is 0. In the category of operator systems, that property functions as semisimplicity does in the category of complex Banach algebras. We construct explicit examples of reduced operator systems using sequences of "parameterizing maps" $\\Gamma_k: \\mathbb C^r\\to \\mathcal B(H_k)$, $k=1,..., N$. We show that every reduced operator system is isomorphic to one of these, and that two sequences give rise to isomorphic operator systems if and only if they are "unitarily equivalent" parameterizing sequences. Finally, we construct nonreduced operator systems $S$ that have a given boundary ideal $K$ and a given reduced image in $C^*(S)/K$, and show that these constructed examples exhaust the possibilities.

  20. Propagating buoyant mantle upwelling on the Reykjanes Ridge

    Science.gov (United States)

    Martinez, Fernando; Hey, Richard

    2017-01-01

    Crustal features of the Reykjanes Ridge have been attributed to mantle plume flow radiating outward from the Iceland hotspot. This model requires very rapid mantle upwelling and a "rheological boundary" at the solidus to deflect plume material laterally and prevent extreme melting above the plume stem. Here we propose an alternative explanation in which shallow buoyant mantle upwelling instabilities propagate along axis to form the crustal features of the ridge and flanks. As only the locus of buoyant upwelling propagates this mechanism removes the need for rapid mantle plume flow. Based on new geophysical mapping we show that a persistent sub-axial low viscosity channel supporting buoyant mantle upwelling can explain the current oblique geometry of the ridge as a reestablishment of its original configuration following an abrupt change in opening direction. This mechanism further explains the replacement of ridge-orthogonal crustal segmentation with V-shaped crustal ridges and troughs. Our findings indicate that crustal features of the Reykjanes Ridge and flanks are formed by shallow buoyant mantle instabilities, fundamentally like at other slow spreading ridges, and need not reflect deep mantle plume flow.

  1. Stability and boundary stabilization of 1-D hyperbolic systems

    CERN Document Server

    Bastin, Georges

    2016-01-01

    This monograph explores the modeling of conservation and balance laws of one-dimensional hyperbolic systems using partial differential equations. It presents typical examples of hyperbolic systems for a wide range of physical engineering applications, allowing readers to understand the concepts in whichever setting is most familiar to them. With these examples, it also illustrates how control boundary conditions may be defined for the most commonly used control devices. The authors begin with the simple case of systems of two linear conservation laws and then consider the stability of systems under more general boundary conditions that may be differential, nonlinear, or switching. They then extend their discussion to the case of nonlinear conservation laws and demonstrate the use of Lyapunov functions in this type of analysis. Systems of balance laws are considered next, starting with the linear variety before they move on to more general cases of nonlinear ones. They go on to show how the problem of boundary...

  2. Classification of boundary equilibrium bifurcations in planar Filippov systems.

    Science.gov (United States)

    Glendinning, Paul

    2016-01-01

    If a family of piecewise smooth systems depending on a real parameter is defined on two different regions of the plane separated by a switching surface, then a boundary equilibrium bifurcation occurs if a stationary point of one of the systems intersects the switching surface at a critical value of the parameter. We derive the leading order terms of a normal form for boundary equilibrium bifurcations of planar systems. This makes it straightforward to derive a complete classification of the bifurcations that can occur. We are thus able to confirm classic results of Filippov [Differential Equations with Discontinuous Right Hand Sides (Kluwer, Dordrecht, 1988)] using different and more transparent methods, and explain why the 'missing' cases of Hogan et al. [Piecewise Smooth Dynamical Systems: The Case of the Missing Boundary Equilibrium Bifurcations (University of Bristol, 2015)] are the only cases omitted in more recent work.

  3. Trophic structure and diversity in rocky intertidal upwelling ecosystems: A comparison of community patterns across California, Chile, South Africa and New Zealand

    Science.gov (United States)

    Blanchette, C. A.; Wieters, E. A.; Broitman, B. R.; Kinlan, B. P.; Schiel, D. R.

    2009-12-01

    The Benguela, California, and Humboldt represent three of the major eastern boundary upwelling ecosystems in the world. Upwelling ecosystems are highly productive, and this productivity forms the base of the food chain, potentially leading to ecosystems similar in trophic structure and diversity among upwelling regions. Here we compare the biological and trophic structure of rocky intertidal communities in each of these major upwelling regions. Our comparison includes a fourth region, New Zealand, which spans a similar latitudinal range, and experiences intermittent upwelling. The influence of oceanographic conditions on these communities was evaluated by using the long-term mean and standard deviation of satellite-based sea surface temperature (SST). Large differences emerged in the taxonomic richness in each of these systems, with California as the most and the Humboldt as the least taxonomically rich. Across all regions, richness tended to decrease progressively from lower trophic levels (macrophytes) to higher trophic levels (carnivores), and richness was inversely correlated with the proportion of variance in SST contained in the seasonal cycle, suggesting that strongly seasonal, predictable environments are relatively low in diversity. The functional and trophic structures were remarkably similar across these four regions of the world. Macrophytes were slightly dominant over filter-feeders in terms of space occupancy in all regions except the Benguela. Densities of herbivorous grazers were greatest in California and Benguela and far outnumbered carnivore densities in all regions. Despite some similarities, the overall structure of the communities from these regions differed significantly supporting the hypothesis that the biological and ecological consequences of similar physical forcing mechanisms (e.g. upwelling) are likely to be context-dependent.

  4. Two degenerate boundary equilibrium bifurcations in planar Filippov systems

    NARCIS (Netherlands)

    Dercole, F.; Della Rossa, F.; Colombo, A.; Kuznetsov, Yuri

    2011-01-01

    We contribute to the analysis of codimension-two bifurcations in discontinuous systems by studying all equilibrium bifurcations of 2D Filippov systems that involve a sliding limit cycle. There are only two such local bifurcations: (1) a degenerate boundary focus, which we call the homoclinic boundar

  5. Intense submesoscale upwelling in anticyclonic eddies

    Science.gov (United States)

    Brannigan, L.

    2016-04-01

    Observations from around the global ocean show that enhanced biological activity can be found in anticyclonic eddies. This may mean that upwelling of nutrient-rich water occurs within the eddy, but such upwelling is not captured by models that resolve mesoscale processes. High-resolution simulations presented here show intense submesoscale upwelling from the thermocline to the mixed layer in anticyclonic eddies. The properties of the upwelling are consistent with a process known as symmetric instability. A simple limiting nutrient experiment shows that this upwelling can drive much higher biological activity in anticyclonic eddies when there is a high nutrient concentration in the thermocline. An estimate for the magnitude of upwelling associated with symmetric instability in anticyclonic eddies in the Sargasso Sea shows that it may be of comparable magnitude to other processes, though further work is required to understand the full implications for basin-scale nutrient budgets.

  6. Influence of ocean winds on the pelagic ecosystem in upwelling regions.

    Science.gov (United States)

    Rykaczewski, Ryan R; Checkley, David M

    2008-02-12

    Upwelling of nutrient-rich, subsurface water sustains high productivity in the ocean's eastern boundary currents. These ecosystems support a rate of fish harvest nearly 100 times the global mean and account for >20% of the world's marine fish catch. Environmental variability is thought to be the major cause of the decadal-scale biomass fluctuations characteristic of fish populations in these regions, but the mechanisms relating atmospheric physics to fish production remain unexplained. Two atmospheric conditions induce different types of upwelling in these ecosystems: coastal, alongshore wind stress, resulting in rapid upwelling (with high vertical velocity, w); and wind-stress curl, resulting in slower upwelling (low w). We show that the level of wind-stress curl has increased and that production of Pacific sardine (Sardinops sagax) varies with wind-stress curl over the past six decades. The extent of isopycnal shoaling, nutricline depth, and chlorophyll concentration in the upper ocean also correlate positively with wind-stress curl. The size structure of plankton assemblages is related to the rate of wind-forced upwelling, and sardine feed efficiently on small plankters generated by slow upwelling. Upwelling rate is a fundamental determinant of the biological structure and production in coastal pelagic ecosystems, and future changes in the magnitude and spatial gradient of wind stress may have important and differing effects on these ecosystems. Understanding of the biological mechanisms relating fisheries production to environmental variability is essential for wise management of marine resources under a changing climate.

  7. Exact boundary controllability of nodal profile for quasilinear hyperbolic systems

    CERN Document Server

    Li, Tatsien; Gu, Qilong

    2016-01-01

    This book provides a comprehensive overview of the exact boundary controllability of nodal profile, a new kind of exact boundary controllability stimulated by some practical applications. This kind of controllability is useful in practice as it does not require any precisely given final state to be attained at a suitable time t=T by means of boundary controls, instead it requires the state to exactly fit any given demand (profile) on one or more nodes after a suitable time t=T by means of boundary controls. In this book we present a general discussion of this kind of controllability for general 1-D first order quasilinear hyperbolic systems and for general 1-D quasilinear wave equations on an interval as well as on a tree-like network using a modular-structure construtive method, suggested in LI Tatsien's monograph "Controllability and Observability for Quasilinear Hyperbolic Systems"(2010), and we establish a complete theory on the local exact boundary controllability of nodal profile for 1-D quasilinear hyp...

  8. Boundary control of parabolic systems - Finite-element approximation

    Science.gov (United States)

    Lasiecka, I.

    1980-01-01

    The finite element approximation of a Dirichlet type boundary control problem for parabolic systems is considered. An approach based on the direct approximation of an input-output semigroup formula is applied. Error estimates are derived for optimal state and optimal control, and it is noted that these estimates are actually optimal with respect to the approximation theoretic properties.

  9. Classical system boundaries cannot be determined within quantum Darwinism

    Science.gov (United States)

    Fields, Chris

    Multiple observers who interact with environmental encodings of the states of a macroscopic quantum system S as required by quantum Darwinism cannot demonstrate that they are jointly observing S without a joint a priori assumption of a classical boundary separating S from its environment E. Quantum Darwinism cannot, therefore, be regarded as providing a purely quantum-mechanical explanation of the "emergence" of classicality.

  10. Optimal control problems for impulsive systems with integral boundary conditions

    Directory of Open Access Journals (Sweden)

    Allaberen Ashyralyev

    2013-03-01

    Full Text Available In this article, the optimal control problem is considered when the state of the system is described by the impulsive differential equations with integral boundary conditions. Applying the Banach contraction principle the existence and uniqueness of the solution is proved for the corresponding boundary problem by the fixed admissible control. The first and second variation of the functional is calculated. Various necessary conditions of optimality of the first and second order are obtained by the help of the variation of the controls.

  11. Seasonal variability and trends in coastal upwelling across the Northwest African coastline, 1981-2012

    Science.gov (United States)

    Cropper, T. E.; Hanna, E.; Bigg, G. R.

    2013-12-01

    The evolution of coastal upwelling systems under global warming is of huge biological, climatological and socio-economic importance. It was hypothesized in the early 1990's that upwelling might increase as a result of stronger land-ocean pressure gradients, however published results since then have conflicted as to whether coastal upwelling intensity has increased across the NW African coastline. Here, we present seasonal upwelling estimates for NW Africa (11-35°N) from 1981-2012, focusing mainly on changes during summer (JJA). Seasonal coastal upwelling indices are derived or estimated from several near-surface wind, sea-surface temperature (SST), sea-surface height (SSH), geometric vertical velocity and near-surface horizontal current datasets. For the wind-stress upwelling indices we use observational data (ICOADS), forecast model data (PFEL) and five atmospheric reanalysis datasets (ERA-Interim, NCEP-DOE II, 20th Century Reanalysis, MERRA and CFSR). For the SST indices we use the HadISST, Reynolds OISST and ICOADS datasets and for SSH we use satellite altimetry data from AVISO. Ocean reanalysis products (ORS4A, SODA 2.1.6 and GODAS) are used for ocean motion data. The numerous indices generally correlate well spatially, all reflecting a similar pattern induced by the trade wind climatology A statistically significant upwelling increase above 21°N is found in several indices, with a corresponding decrease in upwelling intensity below 20°N as well. This supports the upwelling intensification hypothesis as at approximately 20°N the summer trade winds are displaced by onshore monsoonal winds, which favour downwelling. However, these trend directions aren't ubiquitous across all the datasets, with most of the reanalysis wind indices suggesting no significant trend direction and sea-level height from altimetry showing no signs of lowering at coastal gridpoints (which would potentially indicate an upwelling increase). We attempt to validate if upwelling trends are

  12. Ego boundary as process: a systemic-contextual approach.

    Science.gov (United States)

    Polster, S

    1983-08-01

    This paper examines the ego boundary construct, outlining its origin and development within psychoanalytic theory and demonstrating the ways in which its interpretation and use have been affected and circumscribed by the structural model upon which psychoanalytic theory is based. In particular, I will discuss the sequence of reasoning by which the construct boundary became synonymous with barrier at the expense of consideration of its role in maintaining contact and exchange with the world. The contributions and limitations of the mathematical model of Kurt Lewin are also discussed. An alternative systemic-contextual model is proposed, a model which describes boundary not as barrier but as dialectical processes of separation and inclusion which mediate a person's complex relationship with the world.

  13. Variability of Iberian upwelling implied by ERA-40 and ERA-Interim reanalyses

    Directory of Open Access Journals (Sweden)

    José M. R. Alves

    2013-05-01

    Full Text Available The Regional Ocean Modeling System ocean model is used to simulate the decadal evolution of the regional waters in offshore Iberia in response to atmospheric fields given by ECMWF ERA-40 (1961–2001 and ERA-Interim (1989–2008 reanalyses. The simulated sea surface temperature (SST fields are verified against satellite AVHRR SST, and they are analysed to characterise the variability and trends of coastal upwelling in the region. Opposing trends in upwelling frequency are found at the northern limit, where upwelling has been decreasing in recent decades, and at its southern edge, where there is some evidence of increased upwelling. These results confirm previous observational studies and, more importantly, indicate that observed SST trends are not only due to changes in radiative or atmospheric heat fluxes alone but also due to changes in upwelling dynamics, suggesting that such a process may be relevant in climate change scenarios.

  14. Nutrients, Recycling, and Biological Populations in Upwelling Ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Whitledge, T. E.

    1980-01-01

    Nutrient recycling has been studied in the upwelling areas of Baja California, Northwest Africa, and Peru. Regeneration by biological populations in these areas contributes significant quantities of recycled nitrogen which is utilized in productivity processes. Each area has a different combination of organisms which leads to differences in the relative contributions of zooplankton, nekton, or benthos to the nutrient cycles. Comparisons of ammonium regeneration rates of zooplankton and nekton-micronekton populations in the three upwelling areas show that zooplankton recycle relatively less nitrogen in the Baja California and Peru systems than nekton. In the Northwest Africa upwelling region, however, zooplankton, fish, and benthic inputs are all substantial. In recent years the Peruvian upwelling system has been altered with the decline of the anchoveta population and an increase in the importance of zooplankton in nutrient recycling. The distribution of recycled nitrogen (ammonium and urea) in transects across the shelf at 10°S and 15°S indicates that regeneration is relatively more important at 10°S in the region of the wide shelf. In both areas the distribution of ammonium and urea are not entirely coincident thereby indicating differences in their production and/or utilization.

  15. Record of the Pacific Large Low Shear Velocity Province Upwellings Preserved in the Cretaceous Large Igneous Provinces

    Science.gov (United States)

    Madrigal, P.; Gazel, E.; Flores, K. E.; Bizimis, M.; Jicha, B. R.

    2015-12-01

    As the surface expression of deep mantle dynamics, Large Igneous Provinces (LIPs) are associated with the edges of large low shear velocity provinces (LLSVP) rooted at the core-mantle boundary. Instabilities in the LLSVP can cause periodic upwellings of material in the form of mantle plumes, which impact the lithosphere forming LIPs. However, the time frames of these massive lava outpourings are still uncertain. While continental LIPs are more readily accessible, oceanic LIPs have only been studied through drilling and sampling of fragments accreted to continental margins or island arcs, hence, they are relatively less understood. The impact of oceanic LIPs on oceanic biota is conspicuously recorded in global occurrences of black shale deposits that evidence episodes of anoxia and mass extinctions shortly after the formation of LIPs that ultimately can affect life on the entire planet. Our new geochemical and geochronological data of accreted Pacific LIPs found in the coasts of Nicoya Peninsula in Costa Rica record three LIP pulses possibly reflecting upwelling periods of the LLSVP at 140, 120 and 90 Ma. In order to test different models of origin of these LIPS, we created a complete reconstruction of the Pacific Plate configuration from the Mid-Jurassic to Upper-Cretaceous to show the existing correlation between upwelling pulses at edges of the Pacific LLSVP, oceanic anoxic events and the age from Pacific LIPs. We propose that since the formation of the Pacific plate at circa 175-180 Ma, a series of upwellings that interacted with mid-ocean ridge systems separated by 10-20 Ma have affected the planet periodically forming oceanic LIPs that still can be found today on the Pacific seafloor and accreted along the plate margins.

  16. System, subsystem, hive: boundary problems in computational theories of consciousness

    Directory of Open Access Journals (Sweden)

    Tomer Fekete

    2016-07-01

    Full Text Available A computational theory of consciousness should include a quantitative measure of consciousness, or MoC, that (i would reveal to what extent a given system is conscious, (ii would make it possible to compare not only different systems, but also the same system at different times, and (iii would be graded, because so is consciousness. However, unless its design is properly constrained, such an MoC gives rise to what we call the boundary problem: an MoC that labels a system as conscious will do so for some – perhaps most – of its subsystems, as well as for irrelevantly extended systems (e.g., the original system augmented with physical appendages that contribute nothing to the properties supposedly supporting consciousness, and for aggregates of individually conscious systems (e.g., groups of people. This problem suggests that the properties that are being measured are epiphenomenal to consciousness, or else it implies a bizarre proliferation of minds. We propose that a solution to the boundary problem can be found by identifying properties that are intrinsic or systemic: properties that clearly differentiate between systems whose existence is a matter of fact, as opposed to those whose existence is a matter of interpretation (in the eye of the beholder. We argue that if a putative MoC can be shown to be systemic, this ipso facto resolves any associated boundary issues. As test cases, we analyze two recent theories of consciousness in light of our definitions: the Integrated Information Theory and the Geometric Theory of consciousness.

  17. Free boundary problems in PDEs and particle systems

    CERN Document Server

    Carinci, Gioia; Giardinà, Cristian; Presutti, Errico

    2016-01-01

    In this volume a theory for models of transport in the presence of a free boundary is developed. Macroscopic laws of transport are described by PDE's. When the system is open, there are several mechanisms to couple the system with the external forces. Here a class of systems where the interaction with the exterior takes place in correspondence of a free boundary is considered. Both continuous and discrete models sharing the same structure are analysed. In Part I a free boundary problem related to the Stefan Problem is worked out in all details. For this model a new notion of relaxed solution is proposed for which global existence and uniqueness is proven. It is also shown that this is the hydrodynamic limit of the empirical mass density of the associated particle system. In Part II several other models are discussed. The expectation is that the results proved for the basic model extend to these other cases. All the models discussed in this volume have an interest in problems arising in several research fields...

  18. Applying Twisted Boundary Conditions for Few-body Nuclear Systems

    CERN Document Server

    Körber, Christopher

    2015-01-01

    We describe and implement twisted boundary conditions for the deuteron and triton systems within finite-volumes using the nuclear lattice EFT formalism. We investigate the finite-volume dependence of these systems with different twists angles. We demonstrate how various finite-volume information can be used to improve calculations of binding energies in such a framework. Our results suggests that with appropriate twisting of boundaries, infinite-volume binding energies can be reliably extracted from calculations using modest volume sizes with cubic length $L\\approx8-14$ fm. Of particular importance is our derivation and numerical verification of three-body analogue of `i-periodic' twist angles that eliminate the leading order finite-volume effects to the three-body binding energy.

  19. On Systems of Boundary Value Problems for Differential Inclusions

    Institute of Scientific and Technical Information of China (English)

    Lynn ERBE; Christopher C. TISDELL; Patricia J. Y. WONG

    2007-01-01

    Herein we consider the existence of solutions to second-order,two-point boundary value problems (BVPs) for systems of ordinary differential inclusions.Some new Bernstein –Nagumo condi-tions are presented that ensure a priori on the derivative of solutions to the differential inclusion.These a priori results are then applied,in conjunction with appropriate topological methods,to prove some new existence theorems for solutions to systems of BVPs for differential inclusions.The new conditions allow of the treatment of systems of BVPs without growth restrictions.

  20. Boundary-Value Problems for Weakly Nonlinear Delay Differential Systems

    Directory of Open Access Journals (Sweden)

    A. Boichuk

    2011-01-01

    Full Text Available Conditions are derived of the existence of solutions of nonlinear boundary-value problems for systems of n ordinary differential equations with constant coefficients and single delay (in the linear part and with a finite number of measurable delays of argument in nonlinearity: ż(t=Az(t-τ+g(t+εZ(z(hi(t,t,ε,  t∈[a,b], assuming that these solutions satisfy the initial and boundary conditions z(s:=ψ(s if s∉[a,b],  lz(⋅=α∈Rm. The use of a delayed matrix exponential and a method of pseudoinverse by Moore-Penrose matrices led to an explicit and analytical form of sufficient conditions for the existence of solutions in a given space and, moreover, to the construction of an iterative process for finding the solutions of such problems in a general case when the number of boundary conditions (defined by a linear vector functional l does not coincide with the number of unknowns in the differential system with a single delay.

  1. Nonstationary Stokes System in Cylindrical Domains Under Boundary Slip Conditions

    Science.gov (United States)

    Zaja¸czkowski, Wojciech M.

    2017-03-01

    Existence and uniqueness of solutions to the nonstationary Stokes system in a cylindrical domain {Ωsubset{R}^3} and under boundary slip conditions are proved in anisotropic Sobolev spaces. Assuming that the external force belong to {L_r(Ω×(0,T))} and initial velocity to {W_r^{2-2/r}(Ω)} there exists a solution such that velocity belongs to {W_r^{2,1}(Ω×(0,T))} and gradient of pressure to {L_r(Ω×(0,T))}, {rin(1,∞)}, {T > 0}. Thanks to the slip boundary conditions and a partition of unity the Stokes system is transformed to the Poisson equation for pressure and the heat equation for velocity. The existence of solutions to these equations is proved by applying local considerations. In this case we have to consider neighborhoods near the edges which by local mapping can be transformed to dihedral angle {π/2}. Hence solvability of the problem bases on construction local Green functions (near an interior point, near a point of a smooth part of the boundary, near a point of the edge) and their appropriate estimates. The technique presented in this paper can also work in other functional spaces: Sobolev-Slobodetskii, Besov, Nikolskii, Hölder and so on.

  2. Bifurcations and Stability Boundary of a Power System

    Institute of Scientific and Technical Information of China (English)

    Ying-hui Gao

    2004-01-01

    A single-axis ux decay model including an excitation control model proposed in [12,14,16] is studied. As the bifurcation parameter P m (input power to the generator) varies, the system exhibits dynamics emerging from static and dynamic bifurcations which link with system collapse. We show that the equilibrium point of the system undergoes three bifurcations: one saddle-node bifurcation and two Hopf bifurcations. The state variables dominating system collapse are different for different critical points, and the excitative control may play an important role in delaying system from collapsing. Simulations are presented to illustrate the dynamical behavior associated with the power system stability and collapse. Moreover, by computing the local quadratic approximation of the 5-dimensional stable manifold at an order 5 saddle point, an analytical expression for the approximate stability boundary is worked out.

  3. A semilinear parabolic system with a free boundary

    Science.gov (United States)

    Wang, Mingxin; Zhao, Yonggang

    2015-12-01

    This paper deals with a semilinear parabolic system with reaction terms {v^p, u^q} and a free boundary {x = s(t)} in one space dimension, where {s(t)} evolves according to the free boundary condition {s'(t) = -μ(u_x + ρ v_x)}. The main aim of this paper was to study the existence, uniqueness, regularity and long-time behavior of positive solution (maximal positive solution). Firstly, we prove that this problem has a unique positive solution when {p, q ≥ 1}, and a (unique) maximal positive solution when {p < 1} or {q < 1}. Then, we study the regularity of {(u,v)} and {s}. At last, we discuss the global existence, finite-time blowup of the unique positive solution (maximal positive solution) and long-time behavior of bounded global solution.

  4. On the global existence and uniqueness of solutions to the nonstationary boundary layer system

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Jianwen; ZHAO; Junning

    2006-01-01

    In this paper, we study the problem of boundary layer for nonstationary flows of viscous incompressible fluids. There are some open problems in the field of boundary layer. The method used here is mainly based on a transformation which reduces the boundary layer system to an initial-boundary value problem for a single quasilinear parabolic equation. We prove the existence of weak solutions to the modified nonstationary boundary layer system. Moreover, the stability and uniqueness of weak solutions are discussed.

  5. Influence of upwelling on distribution of chaetognath (zooplankton) in the oxygen deficient zone of the eastern Arabian Sea.

    Digital Repository Service at National Institute of Oceanography (India)

    Kusum, K.K.; Vineetha, G.; Raveendran, T.V.; Muraleedharan, K.R.; Biju, A.; Achuthankutty, C.T.

    in the coastal upwelling and coastal transition zones off central-southern Chile (35-40°S). Prog. Oceanogr. 92-95C, 1-7. Escribano, R., Hidalgo, P., Fuentes, M., Donoso, K., 2012. Zooplankton time series in the coastal zone of Chile: Variation in upwelling...., 2010. Patterns of copepod diversity in the Chilean coastal upwelling system. Deep-Sea Res. II 57, 2089-2097. Hidalgo, P., Escribano, R., Fuentes, M., Jorquera, E., Vergara, O., 2012. How coastal upwelling influences spatial patterns of size...

  6. Iron Meteorites and Upwelling in Antarctica

    Science.gov (United States)

    Gourlay, B. S.; Behr, E.; Mardon, A.; Behr, E.

    2016-09-01

    In Antarctica, a meteorite stranding zone, stone meteorites are more common than iron. Dr. Evatt's team suggests that the heat conductivity of iron may be opposing the upwelling effects so iron meteorites sink under the ice unlike the stone ones.

  7. Boundary control of long waves in nonlinear dispersive systems

    DEFF Research Database (Denmark)

    Hasan, Agus; Foss, Bjarne; Aamo, Ole Morten

    2011-01-01

    Unidirectional propagation of long waves in nonlinear dispersive systems may be modeled by the Benjamin-Bona-Mahony-Burgers equation, a third order partial differential equation incorporating linear dissipative and dispersive terms, as well as a term covering nonlinear wave phenomena. For higher...... orders of the nonlinearity, the equation may have unstable solitary wave solutions. Although it is a one dimensional problem, achieving a global result for this equation is not trivial due to the nonlinearity and the mixed partial derivative. In this paper, two sets of nonlinear boundary control laws...... that achieve global exponential stability and semi-global exponential stability are derived for both linear and nonlinear cases....

  8. Boundary relations and boundary conditions for general (not necessarily definite) canonical systems with possibly unequal deficiency indices

    CERN Document Server

    Mogilevskii, Vadim

    2011-01-01

    We investigate in the paper general (not necessarily definite) canonical systems of differential equation in the framework of extension theory of symmetric linear relations. For this aim we first introduce the new notion of a boundary relation $\\G:\\gH^2\\to\\HH$ for $A^*$, where $\\gH$ is a Hilbert space, $A$ is a symmetric linear relation in $\\gH, \\cH_0$ is a boundary Hilbert space and $\\cH_1$ is a subspace in $\\cH_0$. Unlike known concept of a boundary relation (boundary triplet) for $A^*$ our definition of $\\G$ is applicable to relations $A$ with possibly unequal deficiency indices $n_\\pm(A)$. Next we develop the known results on minimal and maximal relations induced by the general canonical system $ J y'(t)-B(t)y(t)=\\D (t)f(t)$ on an interval $\\cI=(a,b),\\; -\\infty\\leq aboundary relation for $\\Tma$ we describe in terms of boundary conditions proper extensions of $\\Tmi$ in the case of the regular endpoint $a$ and arbitrary (possibly unequal)...

  9. Solutions to a hyperbolic system of conservation laws on two boundaries

    Institute of Scientific and Technical Information of China (English)

    JIA Zhi; YAO Ai-di

    2009-01-01

    This paper studies the interaction of elementary waves including delta-shock waves on two boundaries for a hyperbolic system of conservation laws. The solutions of the initial-boundary value problem for the system are constructively obtained. In the problem the initial-boundary data are in piecewise constant states.

  10. The Nonlinear Predator-Prey Singularly Perturbed Robin Initial Boundary Value Problems for Reaction Diffusion System

    Institute of Scientific and Technical Information of China (English)

    莫嘉琪

    2003-01-01

    The nonlinear predator-prey singularly perturbed Robin initial boundary value problems for reaction diffusion systems were considered. Under suitable conditions, using theory of differential inequalities the existence and asymptotic behavior of solution for initial boundary value problems were studied.

  11. Peru-Chile upwelling dynamics under climate change

    Science.gov (United States)

    Oerder, Véra; Colas, Francois; Echevin, Vincent; Codron, Francis; Tam, Jorge; Belmadani, Ali

    2015-02-01

    The consequences of global warming on the Peru-Chile Current System (PCCS) ocean circulation are examined with a high-resolution, eddy-resolving regional oceanic model. We performed a dynamical downscaling of climate scenarios from the IPSL-CM4 Coupled General Circulation Model (CGCM), corresponding to various levels of CO2 concentrations in the atmosphere. High-resolution atmospheric forcing for the regional ocean model are obtained from the IPSL atmospheric model run on a stretched grid with increased horizontal resolution in the PCCS region. When comparing future scenarios to preindustrial (PI) conditions, the circulation along the Peru and Chile coasts is strongly modified by changes in surface winds and increased stratification caused by the regional warming. While the coastal poleward undercurrent is intensified, the surface equatorial coastal jet shoals and the nearshore mesoscale activity are reinforced. Reduction in alongshore wind stress and nearshore wind stress curl drive a year-round reduction in upwelling intensity off Peru. Modifications in geostrophic circulation mitigate this upwelling decrease in late austral summer. The depth of the upwelling source waters becomes shallower in warmer conditions, which may have a major impact on the system's biological productivity.

  12. Biogeochemical cycling in the ocean. Part 1: Introduction to the effects of upwelling along the west coast of North America

    Science.gov (United States)

    Howe, John T.

    1986-01-01

    Coastal upwelling is examined as it relates to the cycling of chemical species in coastal waters along the west coast of North America. The temporal and spatial features of upwelling phenomena in the Eastern boundary regions of the North Pacific Ocean are presented and discussed in terms of upwelling episodes. Climate conditions affecting upwelling include: thermal effects, wind-induced shear stress which moves surface layers, and the curl of the wind stress vector which is thought to affect the extent and nature of upwelling and the formation of offshore convergent downwelling fronts. These effects and the interaction of sunlight and upwelled nutrients which result in a biological bloom in surface waters is modeled analytically. The roles of biological and chemical species, including the effects of predation, are discussed in that context, and relevant remote sensing and in situ observations are presented. Climatological, oceanographic, biological, physical, chemical events, and processes that pertain to biogeochemical cycling are presented and described by a set of partial differential equations. Simple preliminary results are obtained and are compared with data. Thus a fairly general framework has been laid where the many facets of biogeochemical cycling in coastal upwelled waters can be examined in their relationship to one another, and to the whole, to whatever level of detail or approximation is warranted or desired.

  13. Positive solutions of quasilinear parabolic systems with Dirichlet boundary condition

    Science.gov (United States)

    Pao, C. V.; Ruan, W. H.

    Coupled systems for a class of quasilinear parabolic equations and the corresponding elliptic systems, including systems of parabolic and ordinary differential equations are investigated. The aim of this paper is to show the existence, uniqueness, and asymptotic behavior of time-dependent solutions. Also investigated is the existence of positive maximal and minimal solutions of the corresponding quasilinear elliptic system. The elliptic operators in both systems are allowed to be degenerate in the sense that the density-dependent diffusion coefficients D(u) may have the property D(0)=0 for some or all i=1,…,N, and the boundary condition is u=0. Using the method of upper and lower solutions, we show that a unique global classical time-dependent solution exists and converges to the maximal solution for one class of initial functions and it converges to the minimal solution for another class of initial functions; and if the maximal and minimal solutions coincide then the steady-state solution is unique and the time-dependent solution converges to the unique solution. Applications of these results are given to three model problems, including a scalar polynomial growth problem, a coupled system of polynomial growth problem, and a two component competition model in ecology.

  14. The thermodynamic cost of driving quantum systems by their boundaries

    Science.gov (United States)

    Barra, Felipe

    2015-10-01

    The laws of thermodynamics put limits to the efficiencies of thermal machines. Analogues of these laws are now established for quantum engines weakly and passively coupled to the environment providing a framework to find improvements to their performance. Systems whose interaction with the environment is actively controlled do not fall in that framework. Here we consider systems actively and locally coupled to the environment, evolving with a so-called boundary-driven Lindblad equation. Starting from a unitary description of the system plus the environment we simultaneously obtain the Lindblad equation and the appropriate expressions for heat, work and entropy-production of the system extending the framework for the analysis of new, and some already proposed, quantum heat engines. We illustrate our findings in spin 1/2 chains and explain why an XX chain coupled in this way to a single heat bath relaxes to thermodynamic-equilibrium while and XY chain does not. Additionally, we show that an XX chain coupled to a left and a right heat baths behaves as a quantum engine, a heater or refrigerator depending on the parameters, with efficiencies bounded by Carnot efficiencies.

  15. Positive solutions of quasilinear parabolic systems with nonlinear boundary conditions

    Science.gov (United States)

    Pao, C. V.; Ruan, W. H.

    2007-09-01

    The aim of this paper is to investigate the existence, uniqueness, and asymptotic behavior of solutions for a coupled system of quasilinear parabolic equations under nonlinear boundary conditions, including a system of quasilinear parabolic and ordinary differential equations. Also investigated is the existence of positive maximal and minimal solutions of the corresponding quasilinear elliptic system as well as the uniqueness of a positive steady-state solution. The elliptic operators in both systems are allowed to be degenerate in the sense that the density-dependent diffusion coefficients Di(ui) may have the property Di(0)=0 for some or all i. Our approach to the problem is by the method of upper and lower solutions and its associated monotone iterations. It is shown that the time-dependent solution converges to the maximal solution for one class of initial functions and it converges to the minimal solution for another class of initial functions; and if the maximal and minimal solutions coincide then the steady-state solution is unique and the time-dependent solution converges to the unique solution. Applications of these results are given to three model problems, including a porous medium type of problem, a heat-transfer problem, and a two-component competition model in ecology. These applications illustrate some very interesting distinctive behavior of the time-dependent solutions between density-independent and density-dependent diffusions.

  16. Representing Autonomous Systems Self-Confidence through Competency Boundaries

    Science.gov (United States)

    2015-01-01

    Representing Autonomous Systems’ Self-Confidence through Competency Boundaries Andrew R. Hutchins, M. L. Cummings Humans and Autonomy...characteristics of such interactions. This is particularly problematic when task demands approach, or exceed, the competency boundaries of assigned...Systems’ Self-Confidence through Competency Boundaries 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT

  17. Accumulation on the boundary for one-dimensional stochastic particle system

    CERN Document Server

    Malyshev, V A

    2011-01-01

    We consider infinite particle system on the positive half-line moving independently of each other. When a particle hits the boundary it immediately disappears, and the boundary moves to the right on some fixed quantity (particle size). We study the speed of the boundary movement (growth). Possible applications - dynamics of the traffic jam growth, growth of thrombus, epitaxy. Nontrivial mathematics is related to the correlation between particle dynamics and boundary growth.

  18. Surface circulation and upwelling patterns around Sri Lanka

    Directory of Open Access Journals (Sweden)

    A. de Vos

    2013-09-01

    Full Text Available Sri Lanka occupies a unique location within the equatorial belt in the northern Indian Ocean with the Arabian Sea on its western side and the Bay of Bengal on its eastern side. The region is characterised by bi-annually reversing monsoon winds resulting from seasonal differential heating and cooling of the continental land mass and the ocean. This study explored elements of the dynamics of the surface circulation and coastal upwelling in the waters around Sri Lanka using satellite imagery and the Regional Ocean Modelling System (ROMS configured to the study region and forced with ECMWF interim data. The model was run for 2 yr to examine the seasonal and shorter term (∼10 days variability. The results confirmed the presence of the reversing current system in response to the changing wind field: the eastward flowing Southwest Monsoon Current (SMC during the Southwest (SW monsoon transporting 11.5 Sv and the westward flowing Northeast Monsoon Current (NMC transporting 9.5 Sv during the Northeast (NE monsoon, respectively. A recirculation feature located to the east of Sri Lanka during the SW monsoon, the Sri Lanka Dome, is shown to result from the interaction between the SMC and the Island of Sri Lanka. Along the eastern and western coasts, during both monsoon periods, flow is southward converging along the south coast. During the SW monsoon the Island deflects the eastward flowing SMC southward whilst along the east coast the southward flow results from the Sri Lanka Dome recirculation. The major upwelling region, during both monsoon periods, is located along the south coast and is shown to be due to flow convergence and divergence associated with offshore transport of water. Higher surface chlorophyll concentrations were observed during the SW monsoon. The location of the flow convergence and hence the upwelling centre was dependent on the relative strengths of wind driven flow along the east and west coasts: during the SW (NE monsoon the flow

  19. Spatio-temporal trends in coastal upwelling across NW Africa, 1981-2010

    Science.gov (United States)

    Cropper, Thomas; Hanna, Edward; Bigg, Grant

    2013-04-01

    In the early 1990's it was hypothesized that coastal upwelling across the eastern boundary currents may increase as a result of global warming. Since then, numerous studies have sought to elucidate the spatial and temporal trends in coastal upwelling intensity. Across the Canary Current (10-36°N), a conflicting signal (i.e. a positive/negative/no trend) in published results has emerged. We surmise this to be the consequence of (1) minor methodological differences, (2) differences in the temporal periods considered (intra- and inter-annual) and (3) the use of different data sets/sources. Here, we present seasonal upwelling estimates across the most recent 30-year climatic 'normal' period (1981-2010) based on the more commonly used wind stress and sea-surface temperature (SST) methodologies, and reinforce this analysis with traditionally 'lesser-used' sources (including sea-surface height, horizontal current velocity and vertical water column motion). For the wind-stress upwelling index we use six data sources (ERA-Interim, NCEP/NCAR, 20CR, PFEL, ICOADS and MERRA) and for the SST index we use three (HadISST, Reynolds OISST and ICOADS). We also utilize the sparse coastal meteorological and tide-gauge stations scattered across the NW African coastline. Additionally, we examine sea-surface height data from four sources (AVISO, GODAS, SODA and GRACE), horizontal current velocity from two sources (GODAS, SODA) and vertical water column motion from the GODAS dataset as further proxies for upwelling estimation. Generally, across summer, the numerous indices correlate reasonably well and display consistent spatial patterns and the same year-to-year oscillations, although the trend directions across the entire period sometimes diverge. Nevertheless, we conclude there is enough corroborating evidence to suggest there is a positive (negative) tendency in upwelling poleward (equatorward) of 20°N, but are cautious that these trends aren't ubiquitously significant. We suggest

  20. West Florida shelf upwelling: Origins and pathways

    Science.gov (United States)

    Weisberg, Robert H.; Zheng, Lianyuan; Liu, Yonggang

    2016-08-01

    Often described as oligotrophic, the west Florida continental shelf supports abundant fisheries, experiences blooms of the harmful alga, Karenia brevis, and exhibits subsurface chlorophyll maxima evident in shipboard and glider surveys. Renewal of inorganic nutrients by the upwelling of deeper ocean water onto the shelf may account for this, but what are the origins and pathways by which such new water may broach the shelf break and advance toward the shoreline? We address these questions via numerical model simulations of pseudo-Lagrangian, isopycnic water parcel trajectories. Focus is on 2010, when the west Florida shelf was subjected to an anomalously protracted period of upwelling caused by Gulf of Mexico Loop Current interactions with the shelf slope. Origins and pathways are determined by integrating trajectories over successive 45 day intervals, beginning from different locations along the shelf break and at various locations and depths along the shelf slope. Waters upwelling across the shelf break are found to originate from relatively shallow depths along the shelf slope. Even for the anomalous 2010 year, much of this upwelling occurs from about 150 m and above, although waters may broach the shelf break from 300 m depth, particularly in the Florida Panhandle. Such interannual renewal of west Florida shelf waters appears to have profound effects on west Florida shelf ecology.

  1. Boundary value problems for systems of linear partial differential equations and propagation of microanalyticity

    OpenAIRE

    Oaku, Toshinori

    1986-01-01

    We give a general formulation of boundary value problems in the framework of hyperfunctions both for systems of linear partial differential equations with non-characteristic boundary and for Fuchsian systems of partial differential equations in a unified manner. We also give a microlocal formulation, which enables us to prove new results on propagation of micro-analyticity up to the boundary for solutions of systems micro-hyperbolic in a weak sense.

  2. The mechanism of the effects of the upwelling mean on the ENSO event mature phase locking

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The mechanism of the effects of the upwelling mean on the ENSO event mature phase locking is ex-amined by using a mixed-mode model. The results show that the positive feedback process of the ef-fects of the seasonal variation of the upwelling mean on the Kelvin wave is the mechanism of the locking of the event mature phase to the end of the calendar year. The memory of the Rossby waves for the sign-shifting of the sea surface temperature anomaly from positive to negative 6 months before the cold peak time is the other mechanism of the locking of the La Nia event mature phase to the end of the calendar year. The results here are different from previous ones which suggest that the balance between cold and warm trends of sea surface temperature anomaly is the mechanism involved. The cold trend is caused by the upwelling Kelvin wave from upwelling Rossby wave reflected at the western boundary, excited by the westerly anomaly stress over the central Pacific and amplified by the seasonal variation of the coupled strength in its way propagating westward. The warm trend is caused by the Kelvin wave forced by the western wind stress over the middle and eastern equatorial Pacific. The cause of the differences is due to the opposite phase of the seasonal variation of the upwelling mean to that in the observation and an improper parameterization scheme for the effects of the seasonal varia-tion of the upwelling mean on the ENSO cycle in previous studies.

  3. The mechanism of the effects of the upwelling mean on the ENSO event mature phase locking

    Institute of Scientific and Technical Information of China (English)

    YAN BangLiang

    2007-01-01

    The mechanism of the effects of the upwelling mean on the ENSO event mature phase locking is examined by using a mixed-mode model. The results show that the positive feedback process of the effects of the seasonal variation of the upwelling mean on the Kelvin wave is the mechanism of the locking of the event mature phase to the end of the calendar year. The memory of the Rossby waves for the sign-shifting of the sea surface temperature anomaly from positive to negative 6 months before the cold peak time is the other mechanism of the locking of the La Ni(n)a event mature phase to the end of the calendar year. The results here are different from previous ones which suggest that the balance between cold and warm trends of sea surface temperature anomaly is the mechanism involved. The cold trend is caused by the upwelling Kelvin wave from upwelling Rossby wave reflected at the western boundary, excited by the westerly anomaly stress over the central Pacific and amplified by the seasonal variation of the coupled strength in its way propagating westward. The warm trend is caused by the Kelvin wave forced by the western wind stress over the middle and eastern equatorial Pacific. The cause of the differences is due to the opposite phase of the seasonal variation of the upwelling mean to that in the observation and an improper parameterization scheme for the effects of the seasonal variation of the upwelling mean on the ENSO cycle in previous studies.

  4. COMPLEX SYSTEM SELF-ORGANIZATION AND BOUNDARY OF ITS PERCEPTION

    Directory of Open Access Journals (Sweden)

    DUBROV Ju. I.

    2016-04-01

    Full Text Available Stipulations. The term “complex system” (CS is rather frequently utilized, therefore, we will take an effort to give a detailed explanation of what is understood by this term. In order to do that, we will not cite a variety of interpretations existing for this term, instead, we are intended to give a notion to this term that would provide for a more visual interpretation. Basic problem statement. Using the abovementioned Stipulation and Hypotheses it is necessary to determine a quality criterion of a self-organizing system functioning as well as to give its formal description. Certain SC subclasses. In order to detect qualitative peculiarities of the considered model the following numerical investigations were conducted. In a new equilibrium state we obtain an absolutely new evolvable system that again, with the change of a load parameter, initiates the process of its development similar. Facts confirming presence of information perception boundary (IPB with self-organizing systems. Given analysis shows that any system, capable of perceiving information, possesses its own IPB. This fact comes well enough to an agreement with data that prove the possibilities of self-organization on the basis of the existing principles of physics and biology. According to the abovementioned it can be concluded that the task of a qualitative survey of evolvable system may lie in determination of its IPB, depending on determining parameters, such as quantity and quality of information coming into the system as well as speed rate of its organization. Such survey is aimed at the description of all possible bifurcations, plotting of a range of bifurcation set at a range with various type of phase portraits and to indicate a phase portrait corresponding to every range with IPB domain. Using the words of great I.P. Pavlov “all types of life, from the simplest to the most complex organisms, including human, is a long line of ever complicating to the highest degree

  5. EXCURSIONS AND L(E')VY SYSTEM OF BOUNDARY PROCESS

    Institute of Scientific and Technical Information of China (English)

    HE PING; YING JIANGANG

    2003-01-01

    In this paper, the authors investigate the joint distribution of end points of excursion awayfrom a closed set straddling on a fixed time and use this result to compute the Levy systemand the Dirichlet form of the boundary process.

  6. A FREE-BOUNDARY PROBLEM TO DYNAMIC SYSTEM FOR PURE FOREST

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A free-boundary model of nonlinear dynamic system for pure forest is presented, in which the felling rate is unbounded nearby the free boundary. The effiect of unbounded function on a priori estimate and analysis of regularity is overcome, and the existence and uniqueness of the global classical solution to this system are proved.

  7. Exact Boundary Controllability for a Kind of Second-Order Quasilinear Hyperbolic Systems

    Institute of Scientific and Technical Information of China (English)

    Ke WANG

    2011-01-01

    Based on the theory of semi-global C1 solution and the local exact boundary controllability for first-order quasilinear hyperbolic systems,the local exact boundary controllability for a kind of second-order quasilinear hyperbolic systems is obtained by a constructive method.

  8. Laboratory Experiments Concerning Upwellings From the Slab-Graveyard: Implications For Geochemical and Seismic Models

    Science.gov (United States)

    Harris, A. C.; Kincaid, C.; Hall, P.

    2005-12-01

    The ongoing plume debate appears to focus on upwellings characterized by large heads and smaller tails, that form from a deep or basal thermal boundary layer (BTBL), which are driven by temperature excesses in the range of 200° C. We use 3-D laboratory experiments to explore how upwellings might differ from this common plume description when BTBLs are influenced by subducted plates. An important aspect of the models is the representation of ridge chemical differentiation processes resulting in slabs with two distinct layers; a lighter, depleted upper mantle component (Harzburgite:H) and a heavier, iron-rich crustal component (Basalt/Eclogite:B/E). Laboratory experiments utilize a working fluid of glucose syrup with temperature dependent density and viscosity. Compositionally distinct mantle reservoirs are represented through isothermal density/viscosity contrasts controlled by water content. The ambient fluid (AF) is contained within a rectangular tank that is heated from below and cooled from above to produce background convection with a Rayleigh number of 10-5-10-6. Highly viscous, tabular slabs are produced by pouring compositionally distinct syrup from two slab reservoirs (B/E and H) into a mold which is chilled to -5° C. The viscous layered slab is emplaced at the fluid surface and subsequently sinks through, stalls and spreads within a BTBL roughly twice the slab thickness (1 cm). Results show that a wide variety in upwelling morphologies form when layered slabs reside within the BTBL and that plume heads/tails are largely dissimilar to those of the standard plume model. The manner in which the slab laminae vs. AF in the BTBL combine (or segregate) within upwellings depends on viscosity/density contrasts, how slabs collapse in the BTBL, and time. End-member regimes include: experiments dominated by a very light H-slab component with early, cold H-plumes and late, hot B/E-AF plumes and experiments where density differences between H, B/E and AF are small and

  9. Steps in the intensification of Benguela upwelling over the Walvis Ridge during Miocene and Pliocene

    Science.gov (United States)

    Hoetzel, Sebastian; Dupont, Lydie M.; Marret, Fabienne; Jung, Gerlinde; Wefer, Gerold

    2017-01-01

    Upwelling is a significant part of the ocean circulation controlling largely the transport of nutrient-rich cold waters to the surface and therefore influencing ocean productivity and global climate. The Benguela upwelling system (BUS) is one of the major upwelling areas in the world. Previous reconstructions of the BUS mainly focused on the onset and intensification in southern and central parts, but changes of the northern part have been rarely investigated in detail. Using the Late Miocene to Pliocene organic-walled dinoflagellate cyst record of ODP Site 1081, we reconstruct and discuss the early upwelling history over the Walvis Ridge with a special focus on the movement of the Angola-Benguela Front (ABF). We suggest that during the Late Miocene the Angola Current flowed southwards over the Walvis Ridge more frequently than today because the ABF was probably located further south as a result of a weaker meridional temperature gradient. A possible strengthening of the meridional gradient during the latest Miocene to early Pliocene in combination with uplift of south-western Africa intensified the upwelling along the coast and increased the upwelling's filaments over the Walvis Ridge. An intermediate period from 6.2 to 5.5 Ma is shown by the dominance of Habibacysta tectata, cysts of a cool-tolerant dinoflagellate known from the northern Atlantic, indicating changing oceanic conditions contemporaneous with the Messinian Salinity Crisis. From 4.3 Ma on, the upwelling signal got stronger again and waters were well-mixed and nutrient-rich. Our results indicate a northward migration of the ABF as early as 7 Ma and the initial stepwise intensification of the BUS.

  10. Steps in the intensification of Benguela upwelling over the Walvis Ridge during Miocene and Pliocene

    Science.gov (United States)

    Hoetzel, Sebastian; Dupont, Lydie M.; Marret, Fabienne; Jung, Gerlinde; Wefer, Gerold

    2016-03-01

    Upwelling is a significant part of the ocean circulation controlling largely the transport of nutrient-rich cold waters to the surface and therefore influencing ocean productivity and global climate. The Benguela upwelling system (BUS) is one of the major upwelling areas in the world. Previous reconstructions of the BUS mainly focused on the onset and intensification in southern and central parts, but changes of the northern part have been rarely investigated in detail. Using the Late Miocene to Pliocene organic-walled dinoflagellate cyst record of ODP Site 1081, we reconstruct and discuss the early upwelling history over the Walvis Ridge with a special focus on the movement of the Angola-Benguela Front (ABF). We suggest that during the Late Miocene the Angola Current flowed southwards over the Walvis Ridge more frequently than today because the ABF was probably located further south as a result of a weaker meridional temperature gradient. A possible strengthening of the meridional gradient during the latest Miocene to early Pliocene in combination with uplift of south-western Africa intensified the upwelling along the coast and increased the upwelling's filaments over the Walvis Ridge. An intermediate period from 6.2 to 5.5 Ma is shown by the dominance of Habibacysta tectata, cysts of a cool-tolerant dinoflagellate known from the northern Atlantic, indicating changing oceanic conditions contemporaneous with the Messinian Salinity Crisis. From 4.3 Ma on, the upwelling signal got stronger again and waters were well-mixed and nutrient-rich. Our results indicate a northward migration of the ABF as early as 7 Ma and the initial stepwise intensification of the BUS.

  11. Influence of ENSO-Related Wind Stress Variability on the Coastal Upwelling off Peru

    Science.gov (United States)

    Huaringa, E. E.; Campos, E. J.; Lentini, C. A.

    2005-05-01

    The Eastern Tropical and Subtropical Pacific, particularly the coastal region off the western South America, is negatively affected by the El Niño-Southern Oscillation (ENSO) events. The rise of coastal sea temperatures due to the weakening of coastal upwelling causes the reduction of important fish stocks and other coastal resources of economical significance, especially the sardine and anchovy populations. Here, variability in the intensity of upwelling along the Peruvian coast is studied using monthly means of the ERS-1 and ERS-2 scatterometer wind stress. In the study area, the Trade Winds blow predominantly parallel to the coast, making the upwelling system highly sensitive to variability in the intensity of the wind stress. On its turn, the wind stress intensity is expected to suffer strong variation during ENSO periods. In our ongoing work we try to understand the relationship between coastal upwelling and different ENSO events in the 1991-2000 decade. In this period, two warm events where observed, the relatively weaker 1991-1994 and the stronger 97-98 El Niños. In both cases we found that in the region from 12°S to 3°S, the intensity of alongshore wind stress is reduced considerably, with the coastal upwelled waters being replaced by warmer waters. On the other hand, in the region between 12°S and 19°S the coastal upwelling maintains its intensity because only the cross-shore component of the wind stress was reduced. With respect to the two cold events, the 1996-1997 and the 1998-2000 La Niñas, the intensity of the alongshore windstress was higher than the climatological values. This resulted in more intense upwelling in the entire region.

  12. Humpback whale “super-groups” – A novel low-latitude feeding behaviour of Southern Hemisphere humpback whales (Megaptera novaeangliae) in the Benguela Upwelling System

    Science.gov (United States)

    Seakamela, S. Mduduzi; Meÿer, Michael A.; Kirkman, Stephen P.; Barendse, Jaco; Cade, David E.; Hurwitz, David; Kennedy, Amy S.; Kotze, Pieter G. H.; McCue, Steven A.; Thornton, Meredith; Vargas-Fonseca, O. Alejandra; Wilke, Christopher G.

    2017-01-01

    Southern Hemisphere humpback whales (Megaptera novaeangliae) generally undertake annual migrations from polar summer feeding grounds to winter calving and nursery grounds in subtropical and tropical coastal waters. Evidence for such migrations arises from seasonality of historic whaling catches by latitude, Discovery and natural mark returns, and results of satellite tagging studies. Feeding is generally believed to be limited to the southern polar region, where Antarctic krill (Euphausia superba) has been identified as the primary prey item. Non-migrations and / or suspended migrations to the polar feeding grounds have previously been reported from a summer presence of whales in the Benguela System, where feeding on euphausiids (E. lucens), hyperiid amphipods (Themisto gaudichaudii), mantis shrimp (Pterygosquilla armata capensis) and clupeid fish has been described. Three recent research cruises (in October/November 2011, October/November 2014 and October/November 2015) identified large tightly-spaced groups (20 to 200 individuals) of feeding humpback whales aggregated over at least a one-month period across a 220 nautical mile region of the southern Benguela System. Feeding behaviour was identified by lunges, strong milling and repetitive and consecutive diving behaviours, associated bird and seal feeding, defecations and the pungent “fishy” smell of whale blows. Although no dedicated prey sampling could be carried out within the tightly spaced feeding aggregations, observations of E. lucens in the region of groups and the full stomach contents of mantis shrimp from both a co-occurring predatory fish species (Thyrsites atun) and one entangled humpback whale mortality suggest these may be the primary prey items of at least some of the feeding aggregations. Reasons for this recent novel behaviour pattern remain speculative, but may relate to increasing summer humpback whale abundance in the region. These novel, predictable, inter-annual, low latitude feeding

  13. Humpback whale "super-groups" - A novel low-latitude feeding behaviour of Southern Hemisphere humpback whales (Megaptera novaeangliae) in the Benguela Upwelling System.

    Science.gov (United States)

    Findlay, Ken P; Seakamela, S Mduduzi; Meÿer, Michael A; Kirkman, Stephen P; Barendse, Jaco; Cade, David E; Hurwitz, David; Kennedy, Amy S; Kotze, Pieter G H; McCue, Steven A; Thornton, Meredith; Vargas-Fonseca, O Alejandra; Wilke, Christopher G

    2017-01-01

    Southern Hemisphere humpback whales (Megaptera novaeangliae) generally undertake annual migrations from polar summer feeding grounds to winter calving and nursery grounds in subtropical and tropical coastal waters. Evidence for such migrations arises from seasonality of historic whaling catches by latitude, Discovery and natural mark returns, and results of satellite tagging studies. Feeding is generally believed to be limited to the southern polar region, where Antarctic krill (Euphausia superba) has been identified as the primary prey item. Non-migrations and / or suspended migrations to the polar feeding grounds have previously been reported from a summer presence of whales in the Benguela System, where feeding on euphausiids (E. lucens), hyperiid amphipods (Themisto gaudichaudii), mantis shrimp (Pterygosquilla armata capensis) and clupeid fish has been described. Three recent research cruises (in October/November 2011, October/November 2014 and October/November 2015) identified large tightly-spaced groups (20 to 200 individuals) of feeding humpback whales aggregated over at least a one-month period across a 220 nautical mile region of the southern Benguela System. Feeding behaviour was identified by lunges, strong milling and repetitive and consecutive diving behaviours, associated bird and seal feeding, defecations and the pungent "fishy" smell of whale blows. Although no dedicated prey sampling could be carried out within the tightly spaced feeding aggregations, observations of E. lucens in the region of groups and the full stomach contents of mantis shrimp from both a co-occurring predatory fish species (Thyrsites atun) and one entangled humpback whale mortality suggest these may be the primary prey items of at least some of the feeding aggregations. Reasons for this recent novel behaviour pattern remain speculative, but may relate to increasing summer humpback whale abundance in the region. These novel, predictable, inter-annual, low latitude feeding events

  14. Free Boundary Problems for a Lotka-Volterra Competition System

    Science.gov (United States)

    Wang, Mingxin; Zhao, Jingfu

    2014-09-01

    In this paper we investigate two free boundary problems for a Lotka-Volterra type competition model in one space dimension. The main objective is to understand the asymptotic behavior of the two competing species spreading via a free boundary. We prove a spreading-vanishing dichotomy, namely the two species either successfully spread to the entire space as time t goes to infinity and survive in the new environment, or they fail to establish and die out in the long run. The long time behavior of the solutions and criteria for spreading and vanishing are also obtained. This paper is an improvement and extension of J. Guo and C. Wu.

  15. Interactions between trophic levels in upwelling and non-upwelling regions during summer monsoon

    Science.gov (United States)

    Malik, A.; Fernandes, C. E. G.; Gonsalves, M.-J. B. D.; Subina, N. S.; Mamatha, S. S.; Krishna, K.; Varik, S.; Kumari, R.; Gauns, M.; Cejoice, R. P.; Pandey, S. S.; Jineesh, V. K.; Kamaleson, A. S.; Vijayan, V.; Mukherjee, I.; Subramanyan, S.; Nair, S.; Ingole, B.; LokaBharathi, P. A.

    2015-01-01

    Coastal upwelling is a regular phenomenon occurring along the southwest coast of India during summer monsoon (May-September). We hypothesize that there could be a shift in environmental parameters along with changes in the network of interactions between bacteria, phytoplankton, and zooplankton in upwelling and non-upwelling regions. During cruise # 267 on FORV Sagar Sampada, water samples were analysed for environmental and biological parameters from two transects, one upwelling region off Trivandrum (TVM) (8°26‧N, 76°20‧E-8°30‧N, 76°50‧E), and the other non-upwelling region off Calicut (CLT) (11°11‧N, 75°30‧E-11°14‧N,74°54‧E), about 230 nmi to the north. Meteorological, hydrological, and nutrient profiles confirmed upwelling off TVM. Bacteria, phytoplankton and zooplankton significantly responded. Primary and bacterial productivity enhanced together with increase in the percentage of viable bacteria (TVC). Pearson's correlation analysis pointed out the differences in bacterial interactions with other trophic levels at both transects. TVC played a prominent role in trophic interactions off TVM by depending on phytoplankton for substrate (r = 0.754). This contrasted with CLT where total counts (TC) played an important role. However, most interrelationships were less pronounced. Principal component analysis (PCA) confirmed the correlation analysis and further showed that the factor loadings of the biotic and abiotic parameters differed in strength and direction in the two regions. More importantly, the processes of mineralization by bacteria and uptake by phytoplankton are obviously more coupled off TVM as evidenced by the clustering of the related parameters in the PCA biplot. Canonical correspondence analysis also complements these findings and demonstrated that the abiotic factors influenced phytoplankton and bacteria similarly at TVM but differently at CLT. The impact on the trophic interrelationships is evident by the close association

  16. Boundary Layers Associated with a Coupled Navier-Stokes/Allem-Cahn System: The Non-Characteristic Boundary Case

    Institute of Scientific and Technical Information of China (English)

    XIE Xiaoqiang

    2012-01-01

    The goal of this article is to study the boundary layer of Navier-Stokes/Allen-Cahn system in a channel at small viscosity.We prove that there exists a boundary layer at the outlet(down-wind)of thickness v,where v,is the kinematic viscosity.The convergence in L2 of the solutions of the Navier-Stokes/Allen-Cahn equations to that of the Euler/Allen-Cahn equations at the vanishing viscosity was established.In two dimensional case we are able to derive the physically relevant uniform in space and time estimates,which is derived by the idea of better control on the tangential derivative and the use of an anisotropic Sobolve imbedding.

  17. Impact of sea-level change on the paleo Primary Productivity record in the NW African coastal upwelling area

    Science.gov (United States)

    Giraud, X.; Paul, A.

    2009-04-01

    A sea level decrease of 120 m at the Last Glacial Maximum (LGM) drastically modifies the shelf morphology of the North West African coastal upwelling area. Using a regional coupled circulation-ecosystem model subject to a set of boundary conditions that reflect Present Day (PD) and LGM conditions, we aim to quantify how changes in shelf morphology, as well as changes in sub-surface nutrient concentrations or local climatic conditions, influence the biological productivity and its record in the sediments. The oceanic circulation is simulated by the Regional Ocean Modelling System (ROMS), taking advantage of the AGRIF (Adaptive Grid Refinement in Fortran) technique to set-up an embedded grid structure. A high-resolution grid (1/10°) is centred on our study area, and is nested in a larger, coarser grid (1/2°) over the Atlantic domain. Boundary and initial conditions for PD and LGM are provided by global simulations performed with the University of Victoria Earth System-Climate Model (UVic ESCM). We used NPZD (Nutrient, Phytoplankton, Zooplankton and Detritus) biogeochemical models. We have identified the following issues in interpreting a sedimentary record at a fixed core location as an indicator of the total upwelling productivity: - Changes in the shelf morphology due to sea-level change appeared to have an impact on the productivity of the upwelling itself, but also to displace the high-productivity zone. - Comparing the Primary Production (PP) between PD and LGM at a given geographical location, or comparing the zonal mean of the PP, can show opposite results. The comparison at geographical locations assumes a direct connection between the production in the surface ocean and the underlying sediments. The comparison of the zonal mean of PP or sediment flux assumes that lateral advection of particulates and sediment transport are significant processes in producing the sedimentary signal at a given location. We illustrate the various situations, with or without

  18. VOCALS-CUpEx: the Chilean Upwelling Experiment

    Science.gov (United States)

    Garreaud, R. D.; Rutllant, J. A.; Muñoz, R. C.; Rahn, D. A.; Ramos, M.; Figueroa, D.

    2011-03-01

    The VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) was a major field experiment conducted in spring of 2008 off southern Peru and northern Chile, aimed at better understanding the coupled climate systems of the southeast Pacific. Because of logistical constrains, the coastal area around 30° S was not sampled during VOCALS-REx. This area not only marks the poleward edge of the subtropical stratocumulus cloud regime (thus acting as a source of transient disturbances) but is also one of the most active upwelling centers and source of surface ocean kinetic energy along the Chilean coast. To fill such an observational gap, a small, brief, but highly focused field experiment was conducted in late spring 2009 in the near-shore region around 30° S. The Chilean Upwelling Experiment (CUpEx) was endorsed by VOCALS as a regional component. CUpEx included long-term monitoring, an intensive two-week field campaign and off-shore research flights. Our goal was to obtain an atmospheric/oceanic dataset with enough temporal and spatial coverage to be able to document (a) the mean diurnal cycles of the lower-troposphere and upper-ocean in a region of complex topography and coastline geometry, and (b) the ocean-atmosphere response to the rapid changes in coastal winds from strong, upwelling-favorable equatorward flow (southerly winds) to downwelling-favorable poleward flow (northerly winds). In this paper we describe the measurement platforms and sampling strategy, and provide an observational overview, highlighting some key mean-state and transient features.

  19. Bayesian Statistics and Uncertainty Quantification for Safety Boundary Analysis in Complex Systems

    Science.gov (United States)

    He, Yuning; Davies, Misty Dawn

    2014-01-01

    The analysis of a safety-critical system often requires detailed knowledge of safe regions and their highdimensional non-linear boundaries. We present a statistical approach to iteratively detect and characterize the boundaries, which are provided as parameterized shape candidates. Using methods from uncertainty quantification and active learning, we incrementally construct a statistical model from only few simulation runs and obtain statistically sound estimates of the shape parameters for safety boundaries.

  20. On the asymptotic limit of the Navier-Stokes system on domains with rough boundaries

    Science.gov (United States)

    Bucur, Dorin; Feireisl, Eduard; Nečasová, Šárka; Wolf, Joerg

    We study the asymptotic behavior of solutions to the incompressible Navier-Stokes system considered on a sequence of spatial domains, whose boundaries exhibit fast oscillations with amplitude and characteristic wave length proportional to a small parameter. Imposing the complete slip boundary conditions we show that in the asymptotic limit the fluid sticks completely to the boundary provided the oscillations are non-degenerate, meaning not oriented in a single direction.

  1. Well-Posedness of Second Order Uniformly Elliptic Boundary Control Systems with Additive or Multiplicative Uncertainty

    Directory of Open Access Journals (Sweden)

    Ada Cheng

    2006-01-01

    Full Text Available Boundary control systems arises naturally in many applications. Any modelling of real systems involve uncertainty. Sufficient conditions for well-posededness for additive or multiplicative uncertainty are presented through the use of matrix theory.

  2. Characterization of upwelling phenomenon along the Italian coasts

    Science.gov (United States)

    Orasi, Arianna; Morucci, Sara; Rinaldi, Eleonora; Bignami, Francesco; Inghilesi, Roberto; Santoleri, Rosalia

    2013-04-01

    In order to investigate wind-driven upwelling along the Italian coasts, preliminary wind data provided by the ISPRA Italian Tide Gauge Measurement Network (RMN) have been analyzed. In a further step, MyOcean Sea Surface Temperature (SST) data have been analyzed in order to define an SST index for wind-driven coastal upwelling assessment. At first, hourly wind data for the period 2009 - 2011 have been used in order to provide the statistical distribution and the wind rose plots at each RMN station. In particular, wind direction and speed have been selected in order to find upwelling-favorable areas and periods of time. E.g. wind directions in the sector between North and West in the Tyrrhenian Sea and between South and East in the Adriatic Sea have been defined as upwelling favorable, the wind sector being defined as the ± 30° arc around the direction parallel to the coast. Moreover only wind speeds greater than 3.0 m/s have been considered as significant for upwelling. For each location, the number of selected data has been divided by the total number of recorded wind data, thus obtaining a sort of upwelling frequency, which allows to define areas mostly exposed to upwelling. Once these areas were defined, satellite SST data have been used as a proxy to study the changes in upwelling intensity, since upwelling waters are colder than surrounding waters. So, in a given satellite SST image the upwelling event is identifiable through SST minima along the coasts. Finally, the SST upwelling index has been defined; also, this index has been "weighted" with wind intensity and direction indicating upwelling conditions obtained from the RMN wind dataset, to better distinguish between upwelling-favorable and downwelling-favorable conditions at each RMN site.

  3. Boundary-induced dynamics in one-dimensional topological systems and memory effects of edge modes

    Science.gov (United States)

    He, Yan; Chien, Chih-Chun

    2016-07-01

    Dynamics induced by a change of boundary conditions reveals rate-dependent signatures associated with topological properties in one-dimensional Kitaev chain and SSH model. While the perturbation from a change of the boundary propagates into the bulk, the density of topological edge modes in the case of transforming to open boundary condition reaches steady states. The steady-state density depends on the transformation rate of the boundary and serves as an illustration of quantum memory effects in topological systems. Moreover, while a link is physically broken as the boundary condition changes, some correlation functions can remain finite across the broken link and keep a record of the initial condition. By testing those phenomena in the nontopological regimes of the two models, none of the interesting signatures of memory effects can be observed. Our results thus contrast the importance of topological properties in boundary-induced dynamics.

  4. Quantum Dynamics of a Bulk-Boundary System

    CERN Document Server

    Ichinose, S; Ichinose, Shoichi; Murayama, Akihiro

    2004-01-01

    The quantum dynamics of a bulk-boundary theory is closely examined by the use of the background field method. As an example we take the Mirabelli-Peskin model, which is composed of 5D super Yang-Mills (bulk) and 4D Wess-Zumino (boundary). Singular interaction terms play an important role of canceling the divergences coming from the KK-mode sum. An interesting background configuration of scalar fields is found. It is a localized solution of the field equation. In this process of the vacuum search, we present a new treatment of the extra coordinate. The "supersymmetric" effective potential is obtained at the full (w.r.t. the coupling) 1-loop level. Renormalization group analysis is done. The Casimir energy is calculated and is compared with the case of the Kaluza-Klein model.

  5. REGULARITY THEORY FOR SYSTEMS OF PARTIAL DIFFERENTIAL EQUATIONS WITH NEUMANN BOUNDARY CONDITIONS

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The objective of this paper is to consider the theory of regularity of systems of partial differential equations with Neumann boundary conditions. It complements previous works of the authors for the Dirichlet case. This type of problem is motivated by stochastic differential games. The Neumann case corresponds to stochastic differential equations with reflection on boundary of the domain.

  6. Dislocations, boundaries and slip systems in cube grains of rolled aluminium

    DEFF Research Database (Denmark)

    Wei, Yili; Godfrey, A.; Liu, W.;

    2011-01-01

    The relationship between the dislocation content of boundaries and the active slip systems is explored by characterisation of Burgers vectors, dislocation lines and relative densities in 11 boundaries in near-cube grains in 10% rolled aluminium. To provide a good basis for comparison, all...

  7. Quantum dynamics of a bulk-boundary system

    Science.gov (United States)

    Ichinose, Shoichi; Murayama, Akihiro

    2005-03-01

    The quantum dynamics of a bulk-boundary theory is closely examined by the use of the background field method. As an example we take the Mirabelli-Peskin model, which is composed of 5D super-Yang-Mills (bulk) and 4D Wess-Zumino (boundary). Singular interaction terms play an important role of canceling the divergences coming from the KK-mode sum. Some new regularization of the momentum integral is proposed. An interesting background configuration of scalar fields is found. It is a localized solution of the field equation. In this process of the vacuum search, we present a new treatment of the vacuum with respect to the extra coordinate. The "supersymmetric" effective potential is obtained at the 1-loop full (w.r.t. the coupling) level. This is the bulk-boundary generalization of the Coleman-Weinberg's case. Renormalization group analysis is done and the correct 4D result is reproduced. The Casimir energy is calculated and is compared with the case of the Kaluza-Klein model.

  8. The use of circulation weather types to predict upwelling activity along the Western Iberian Peninsula coast

    Science.gov (United States)

    Ramos, Alexandre M.; Cordeiro Pires, Ana; Sousa, Pedro M.; Trigo, Ricardo M.

    2013-04-01

    Coastal upwelling is a phenomenon that occurs in most western oceanic coasts due to the presence of mid-latitude high-pressure systems that generate equatorward winds along the coast and consequent offshore displacement of surface waters that in turn cause deeper, colder, nutrient-rich waters to arise. In western Iberian Peninsula (IP) the high-pressure system associated to northerly winds occurs mainly during spring and summer. Upwelling systems are economically relevant, being the most productive regions of the world ocean and crucial for fisheries. In this work, we evaluate the intra- and inter-annual variability of the Upwelling Index (UI) off the western coast of the IP considering four locations at various latitudes: Rias Baixas, Aveiro, Figueira da Foz and Cabo da Roca. In addition, the relationship between the variability of the occurrence of several circulation weather types (Ramos et al., 2011) and the UI variability along this coast was assessed in detail, allowing to discriminate which types are frequently associated with strong and weak upwelling activity. It is shown that upwelling activity is mostly driven by wind flow from the northern quadrant, for which the obtained correlation coefficients (for the N and NE types) are higher than 0.5 for the four considered test locations. Taking into account these significant relationships, we then developed statistical multi-linear regression models to hindcast upwelling series (April to September) at the four referred locations, using monthly frequencies of circulation weather types as predictors. Modelled monthly series reproduce quite accurately observational data, with correlation coefficients above 0.7 for all locations, and relatively small absolute errors. Ramos AM, Ramos R, Sousa P, Trigo RM, Janeira M, Prior V (2011) Cloud to ground lightning activity over Portugal and its association with Circulation Weather Types. Atmospheric Research 101:84-101. doi: 10.1016/j.atmosres.2011.01

  9. Large-Eddy Simulations of Tropical Convective Systems, the Boundary Layer, and Upper Ocean Coupling

    Science.gov (United States)

    2014-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Large - Eddy Simulations of Tropical Convective Systems... large eddy simulation (LES) of organized convective systems, which resolve boundary layer eddy scales to mesoscale Report Documentation Page Form...COVERED 00-00-2014 to 00-00-2014 4. TITLE AND SUBTITLE Large - Eddy Simulations of Tropical Convective Systems, the Boundary Layer, and Upper Ocean

  10. Artificial ocean upwelling utilizing the energy of surface waves

    Science.gov (United States)

    Soloviev, Alexander

    2016-04-01

    Artificial upwelling can bring cold water from below the thermocline to the sea surface. Vershinsky, Pshenichnyy, and Soloviev (1987) developed a prototype device, utilizing the energy of surface waves to create an upward flow of water in the tube. This is a wave-inertia pump consisting of a vertical tube, a valve, and a buoy to keep the device afloat. An outlet valve at the top of the unit synchronizes the operation of the device with surface waves and prevents back-splashing. A single device with a 100 m long and 1.2 m diameter tube is able to produce up to 1 m3s-1 flow of deep water to the surface. With a 10 oC temperature difference over 100 m depth, the negative heat supply rate to the sea surface is 42 MW, which is equivalent to a 42 Wm-2 heat flux, if distributed over 1 km2 area. Such flux is comparable to the average net air-sea flux. A system of artificial upwelling devices can cool down the sea surface, modify climate on a regional scale and possibly help mitigate hurricanes. The cold water brought from a deeper layer, however, has a larger density than the surface water and therefore has a tendency to sink back down. In this work, the efficiency of wave-inertia pumps and climatic consequences are estimated for different environmental conditions using a computational fluid dynamics model.

  11. Generalized solutions of initial-boundary value problems for second-order hyperbolic systems

    Science.gov (United States)

    Alexeyeva, L. A.; Zakir'yanova, G. K.

    2011-07-01

    The method of boundary integral equations is developed as applied to initial-boundary value problems for strictly hyperbolic systems of second-order equations characteristic of anisotropic media dynamics. Based on the theory of distributions (generalized functions), solutions are constructed in the space of generalized functions followed by passing to integral representations and classical solutions. Solutions are considered in the class of singular functions with discontinuous derivatives, which are typical of physical problems describing shock waves. The uniqueness of the solutions to the initial-boundary value problems is proved under certain smoothness conditions imposed on the boundary functions. The Green's matrix of the system and new fundamental matrices based on it are used to derive integral analogues of the Gauss, Kirchhoff, and Green formulas for solutions and solving singular boundary integral equations.

  12. Boundary-locality and perturbative structure of entanglement spectra in gapped systems.

    Science.gov (United States)

    Alba, Vincenzo; Haque, Masudul; Läuchli, Andreas M

    2012-06-01

    The entanglement between two parts of a many-body system can be characterized in detail by the entanglement spectrum. Focusing on gapped phases of several one-dimensional systems, we show how this spectrum is dominated by contributions from the boundary between the parts. This contradicts the view of an "entanglement Hamiltonian" as a bulk entity. The boundary-local nature of the entanglement spectrum is clarified through its hierarchical level structure, through the combination of two single-boundary spectra to form a two-boundary spectrum, and finally through consideration of dominant eigenfunctions of the entanglement Hamiltonian. We show consequences of boundary-locality for perturbative calculations of the entanglement spectrum.

  13. A question of fit: reflections on boundaries, organizations and social-ecological systems.

    Science.gov (United States)

    Sternlieb, Faith; Bixler, R Patrick; Huber-Stearns, Heidi; Huayhuaca, Ch'aska

    2013-11-30

    Although there is acknowledgment that the complexity of social-ecological systems governance demands representation from diverse perspectives, there is little agreement in the literature on how to cross both fiat (human-demarcated) and bona fide (physical) boundaries to address such complexities. As a cohort of interdisciplinary scholars, we navigate the boundary between science and practice to address the question of fit regarding the role of organizations in transcending boundaries. We found there is a need to rectify discrepancies between theories about boundaries and theories about organizations. To this end, we propose a conceptual framework to analyze transboundary organizations, an umbrella term to group the literature on boundary organizations, intermediaries and bridging organizations; we introduce this term to illustrate they are not mutually exclusive and to facilitate interdisciplinary research. We first examine social-ecological systems (SES), a framework intended to improve understandings of boundaries and governance. We then continue to unpack the complexity of boundaries and organizations, specifically through important transboundary concepts such as scale and organizational learning. This helps frame our examination of the literature on: 1) boundary organizations; 2) bridging organizations (third-party entities); and 3) intermediaries (distinguished by their position between other actors). Our review identifies a number of discrepancies that pertain to the types of boundaries discussed and the roles assigned to organizations governing SES. Important characteristics have emerged from our review of transboundary organizations including legitimacy, saliency, urgency, and credibility. In developing a conceptual framework, we argue that transboundary organizations: 1) expand upon the boundary spectrum, 2) incorporate transboundary concepts, and 3) hybridize characteristics of boundary, bridging, and intermediary organizations. We conclude with a number

  14. The Nonlinear Singularly Perturbed Initial Boundary Value Problems of Nonlocal Reaction Diffusion Systems

    Institute of Scientific and Technical Information of China (English)

    Jia-qi Mo; Wan-tao Lin

    2006-01-01

    In this paper the singularly perturbed initial boundary value problems for the nonlocal reaction diffusion system are considered. Using the iteration method and the comparison theorem, the existence and its asymptotic behavior of the solution for the problem are studied.

  15. Aquifer Boundary of the Wood River Valley Aquifer System, South-Central Idaho

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This dataset contains the boundary of the Wood River Valley aquifer system as modified and expanded from that defined by Skinner and others (2007): It has been...

  16. Blow-up estimates for semilinear parabolic systems coupled in an equation and a boundary condition

    Institute of Scientific and Technical Information of China (English)

    王明新

    2001-01-01

    This paper deals with the blow-up rate estimates of solutions for semilinear parabolic systems coupled in an equation and a boundary condition. The upper and lower bounds of blow-up rates have been obtained.

  17. POSITIVE SOLUTIONS OF BOUNDARY VALUE PROBLEM FOR A SYSTEM OF NONLINEAR ORDINARY DIFFERENTIAL EQUATIONS

    Institute of Scientific and Technical Information of China (English)

    LiHongyu; SunJingxian

    2005-01-01

    By using topological method, we study a class of boundary value problem for a system of nonlinear ordinary differential equations. Under suitable conditions,we prove the existence of positive solution of the problem.

  18. THE DYNAMICS OF SINE-GORDON SYSTEM WITH DIRICHLET BOUNDARY CONDITION

    Institute of Scientific and Technical Information of China (English)

    Liu Yingdong; Li Zhengyuan

    2000-01-01

    We prove the existence of the global attractor of Sine-Gordon system with Dirichlet boundary condition and show the attractor is the unique steady state when the damping constant and the diffusion constant are sufficiently large.

  19. Undiscovered natural gas resources Total Petroleum System unit boundaries for Bangladesh (tps8bg)

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This coverage includes arcs, polygons, and polygon labels that describe the Total Petroleum System boundaries of the natural gas resources of Bangladesh. This...

  20. Stratigraphic modeling of organic matter distribution and preservation in deep marine environment. Case of a margin with pelagic sedimentation: the coastal upwelling system of Benguela (Namibia, Western South Africa); Modelisation stratigraphique de la distribution et de la preservation de la matiere organique en milieu marin profond. Cas d'une marge a sedimentation pelagique: systeme d'upwelling cotier du Benguela (Namibie, Afrique du Sud Ouest)

    Energy Technology Data Exchange (ETDEWEB)

    Tranier, J.

    2006-06-15

    In order to develop stratigraphic modelling of organic matter distribution and preservation in marine environment, the methodology established, uses three modelling softwares. We make use of a 3D stratigraphic model, DIONISOS, which allows to build margin thanks to sediment input and transport and thanks to basin deformation. Biogenic sediments are introduced in DIONISOS after their production modelling by two coupled models, ROMS and NPZD. ROMS is a physical model which allows to simulate upwelling dynamics thanks to wind strength exerted on ocean surface and to margin morphology. NPZD models relationships (photosynthesis, grazing, excretion, mortality, re-mineralization, etc.) between four boxes: nutrients, phytoplankton, zooplankton and detritus. Nutrients availability (model inputs) and flux intensity between boxes are controlled by upwelling dynamics, i-e ROMS. Thanks to these three softwares, organic matter can be modelled from its production to its fossilization considering the influence of various factors as upwelling intensity, nutrients availability, chemical compounds of water mass and oxygenation of water column, species competition (diatoms and coccolithophoridae), margin morphology and eustatism. After testing sensibility of the various parameters of the three models, we study their capacity for reproduce biogenic sedimentation and simulate climatic cycle effect on organic matter distribution on a passive continental margin: the Namibian margin (Southwest Africa). They are validated comparing results with core data from this margin. (author)

  1. Bifurcations of Eigenvalues of Gyroscopic Systems with Parameters Near Stability Boundaries

    DEFF Research Database (Denmark)

    Seyranian, Alexander P.; Kliem, Wolfhard

    1999-01-01

    . It is shown that the bifurcation (splitting) of double eigenvalues is closely related to the stability, flutter and divergence boundaries in the parameter space. Normal vectors to these boundaries are derived using only information at a boundary point: eigenvalues, eigenvectors and generalized eigenvectors......The paper deals with stability problems of linear gyroscopic systems with finite or infinite degrees of freedom, where the system matrices or operators depend smoothly on several real parameters. Explicit formulae for the behavior of eigenvalues under a change of parameters are obtained...

  2. Tomographic mapping of a coastal upwelling and the associated diurnal internal tides in Hiroshima Bay, Japan

    Science.gov (United States)

    Zhang, Chuanzheng; Kaneko, Arata; Zhu, Xiao-Hua; Gohda, Noriaki

    2015-06-01

    Temperature variations caused by a typhoon were measured in the northern part of Hiroshima Bay by four coastal acoustic tomography (CAT) systems. The horizontal distributions of depth-averaged temperature from 0 to 8 m were mapped at 10 min intervals between the 11 and 25 September 2013. The horizontal distributions of a coastal upwelling and the associated diurnal internal tides were reconstructed well by regularized inversion based on the grid segmented method, using one-way travel time data along five successful sound transmission lines. Station-to-station ranges were corrected in such a way that sound speed (determined from one-way travel time data) was equal to sound speed calculated from a couple of CTD (conductivity-temperature-depth) data sets on each transmission line. In addition, all station positions were adjusted to make focal points at the geographical positions of the transducers. The corrections increased the accuracy of temperature measurements to make temperature errors as small as 0.073-0.079°C. The high accuracy made it possible to map the temperature structure with a variation range of less than 0.5°C. An upwelling grew from 16 to 17 September, due to a typhoon-derived northerly wind. The diurnal internal tide resonated with the semidiurnal external tide, which was pronounced after the upwelling decayed (18 September), around the time the spring tide occurred. The upwelling and mixing fractions were formulated. These fractions increased continuously as the upwelling grew. Complete mixing was observed during the upwelling's mature phase.

  3. Role of Ekman Transport Versus Ekman Pumping in Driving Summer Upwelling in the South China Sea

    Institute of Scientific and Technical Information of China (English)

    WANG Dakui; WANG Hui; LI Ming; LIU Guimei; WU Xiangyu

    2013-01-01

    Relative roles of Ekman transport and Ekman pumping in driving summer upwelling in the South China Sea (SCS) are examined using QuikSCAT scatterometer wind data.The major upwelling regions in the SCS are the coastal regions east and southeast of Vietnam (UESEV),east and southeast of Hainan Island (UESEH),and southeast of Guangdong province (USEG).It is shown that the Ekman transport due to alongshore winds and Ekman pumping due to offshore wind stress curl play different roles in the three upwelling systems.In UESEV,Ekman pumping and Ekman transport are equally important in generating upwelling.The Ekman transport increases linearly from 0.49 Sv in May to 1.23 Sv in August,while the Ekman pumping increases from 0.36 to 1.22 Sv during the same period.In UESEH,the mean estimates of Ekman transport and Ekman pumping are 0.14 and 0.07 Sv,respectively,indicating that 33% of the total wind-driven upwelling is due to Ekman pumping.In USEG,the mean Ekman transport is 0.041 Sv with the peak occurring in July,while Ekman pumping is much smaller (0.003 on average),indicating that the upwelling in this area is primarily driven by Ekman transport.In the summers of 2003 and 2007 following E1 Ni(n)o-Southem Oscillation (ENSO) events,both Ekman transport and Ekman pumping decrease in UESEV due to the abnormally weak southwest monsoon.During the same events,however,Ekman transport is slightly enhanced and Ekman pumping is weakened in UESEH and USEG.

  4. Exact Synchronization for a Coupled System of Wave Equations with Dirichlet Boundary Controls

    Institute of Scientific and Technical Information of China (English)

    Tatsien LI; Bopeng RAO

    2013-01-01

    In this paper,the exact synchronization for a coupled system of wave equations with Dirichlet boundary controls and some related concepts are introduced.By means of the exact null controllability of a reduced coupled system,under certain conditions of compatibility,the exact synchronization,the exact synchronization by groups,and the exact null controllability and synchronization by groups are all realized by suitable boundary controls.

  5. Invariance of decay rate with respect to boundary conditions in thermoelastic Timoshenko systems

    Science.gov (United States)

    Alves, M. S.; Jorge Silva, M. A.; Ma, T. F.; Muñoz Rivera, J. E.

    2016-06-01

    This paper is mainly concerned with the polynomial stability of a thermoelastic Timoshenko system recently introduced by Almeida Júnior et al. (Z Angew Math Phys 65(6):1233-1249, 2014) that proved, in the general case when equal wave speeds are not assumed, different polynomial decay rates depending on the boundary conditions, namely, optimal rate {t^{-1/2}} for mixed Dirichlet-Neumann boundary condition and rate {t^{-1/4}} for full Dirichlet boundary condition. Here, our main achievement is to prove the same polynomial decay rate {t^{-1/2}} (corresponding to the optimal one) independently of the boundary conditions, which improves the existing literature on the subject. As a complementary result, we also prove that the system is exponentially stable under equal wave speeds assumption. The technique employed here can probably be applied to other kind of thermoelastic systems.

  6. Coastal upwelling and downwelling forcing of circulation in a semi-enclosed bay: Ria de Vigo

    Science.gov (United States)

    Barton, E. D.; Largier, J. L.; Torres, R.; Sheridan, M.; Trasviña, A.; Souza, A.; Pazos, Y.; Valle-Levinson, A.

    2015-05-01

    Semi-enclosed bays in upwelling regions are exposed to forcing related to winds, currents and buoyancy over the shelf. The influence of this external forcing is moderated by factors such as connectivity to the open ocean, shelter by surrounding topography, dimensions of the bay, and freshwater outflows. Such bays, preferred locations for ports, mariculture, marine industry, recreational activities and coastal settlement, present a range of characteristics, understanding of which is necessary to their rational management. Observations in such a semi-enclosed bay, the Ria de Vigo in Spain, are used to characterize the influence of upwelling and downwelling pulses on its circulation. In this location, near the northern limit of the Iberian upwelling system, upwelling events dominate during a short summer season and downwelling events the rest of the year. The ria response to the external forcing is central to nutrient supply and resultant plankton productivity that supports its high level of cultured mussel production. Intensive field studies in September 2006 and June 2007 captured a downwelling event and an upwelling event, respectively. Data from eight current profiler moorings and boat-based MiniBat/ADCP surveys provided an unprecedented quasi-synoptic view of the distribution of water masses and circulation patterns in any ria. In the outer ria, circulation was dominated by the introduction of wind-driven alongshore flow from the external continental shelf through the ria entrances and its interaction with the topography. In the middle ria, circulation was primarily related to the upwelling/downwelling cycle, with a cool, salty and dense lower layer penetrating to the inner ria during upwelling over the shelf. A warmer, lower salinity and less dense surface layer of coastal waters flowed inward during downwelling. Without external forcing, the inner ria responded primarily to tides and buoyancy changes related to land runoff. Under both upwelling and downwelling

  7. Habitable Zone Boundaries: Implications for our Solar System and Beyond

    Science.gov (United States)

    Kasting, J. F.; Kopparapu, R.; Harman, C.; Batalha, N. E.; Haqq-Misra, J. D.

    2015-12-01

    The successful completion of NASA's Kepler Mission has led to renewed interest in the definition and boundaries of the circumstellar habitable zone (HZ), where liquid water can be stable on a planet's surface. Goldblatt et al. [1] showed that the runaway greenhouse effect, which defines the inner edge of the HZ, depends critically on absorption coefficients of H2O obtained from the new HITEMP database. Kopparapu et al. [2,3] followed up on this observation by recalculating HZ boundaries using HITEMP coefficients. This caused the inner edge to move out to 0.99 AU in their (fully saturated, cloud-free) 1-D climate model. Leconte et al. [4] then used a 3-D climate model to show that the inner edge moves back in to 0.95 AU when relative humidity and clouds are taken into account. In their model, however, the upper stratosphere remained cold and dry, making it difficult to explain how Venus lost its water. But Leconte et al. only looked at surface temperatures up to ~330 K. At somewhat higher surface temperatures (350 K), our own 1-D model predicts that the stratosphere should indeed become wet [5]. Towards the outer edge of the HZ, it now appears that planets should undergo limit cycles involving global glaciation, CO2 buildup from volcanism, and CO2 drawdown from weathering [6,7]. If supplemented with volcanic H2 [8], such cycles could explain how early Mars could have been cold much of the time and yet have experienced enough warm periods to carve the observed fluvial features. Results from a new model of this process will be discussed. Refs: 1. Goldblatt, C., Robinson, T. D., Zahnle, K. J., & Crisp, D. 2013, Nature Geoscience, 6, 661 2. Kopparapu, R. K., et al. 2013, Astrophysical Journal, 765 3. ---. 2013, Astrophysical Journal, 770 4. Leconte, J., Forget, F., Charnay, B., Wordsworth, R., & Pottier, A. 2013, Nature, 504, 268 5. Kasting, J. F., Chen, H., & Kopparapu, R. K. in prep., Ap J Lett 6. Kadoya, S., & Tajika, E. 2014, Astrophysical Journal, 790 7. Menou, K

  8. Upwelling features near Sri Lanka in the Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    ShreeRam, P.; Rao, L.V.G.

    , the southwest monsoon in summer and the northeast monsoon in winter. The wind stress associated with these winds cause mass drift of oceanic waters leading to upwelling and downwelling. The upwelling features in the Bay of Bengal with a special mention about...

  9. Evidence of Upwelling along Peninsular Malaysia during Southwest Monsoon

    DEFF Research Database (Denmark)

    Daryabor, Farshid

    2015-01-01

    Upwelling off the east coast of Peninsular Malaysia (PM) was detected from recent cruise data collected during the southwest monsoon. Thermocline lifting was observed at 104˚E from a number of parallel transects. To confirm the presence of upwelling, satellite remote sensing data were used...

  10. A NON-UNIFORM SEDIMENT TRANSPORT MODEL WITH THE BOUNDARY-FITTING ORTHOGONAL COORDINATE SYSTEM

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A 2-D non-uniform sediment mathmatical model in the boundary-fitting orthogonal coordinate system was developed in this paper. The governing equations, the numerical scheme, the boundary conditions, the movable boundary technique and the numerical solutions were presented. The model was verified by the data of the reach 25km upstream the Jialingjiang estuary and the 44km long main stream of the Chongqing reach of the Yangtze river. The calculated results show that, the water elevation, the velocity distribution and the river bed deformation are in agreement with the measured data.

  11. Magnetic field effect on the liquidus boundary of Bi-Mn binary system

    Science.gov (United States)

    Mitsui, Yoshifuru; Koyama, Keiichi; Oikawa, Katsunari; Watanabe, Kazuo

    2014-10-01

    The magnetic field effect (MFE) on liquidus boundary of Bi-Mn binary system was investigated by differential thermal analysis (DTA) and the computer coupling of phase diagram method (CALPHAD). The liquidus boundary for Bi-18at.%Mn and Bi-24at.%Mn rose clearly by the application of the magnetic fields. The MFE for liquidus boundary temperature Tliq changed from ΔTliq∝B2 to ΔTliq∝B because of the large increase of the peritectic temperature from BiMn and BiMn1.08 by the application of magnetic field.

  12. Diffusive boundary layers over varying topography

    KAUST Repository

    Dell, R. W.

    2015-03-25

    Diffusive bottom boundary layers can produce upslope flows in a stratified fluid. Accumulating observations suggest that these boundary layers may drive upwelling and mixing in mid-ocean ridge flank canyons. However, most studies of diffusive bottom boundary layers to date have concentrated on constant bottom slopes. We present a study of how diffusive boundary layers interact with various idealized topography, such as changes in bottom slope, slopes with corrugations and isolated sills. We use linear theory and numerical simulations in the regional ocean modeling system (ROMS) model to show changes in bottom slope can cause convergences and divergences within the boundary layer, in turn causing fluid exchanges that reach far into the overlying fluid and alter stratification far from the bottom. We also identify several different regimes of boundary-layer behaviour for topography with oceanographically relevant size and shape, including reversing flows and overflows, and we develop a simple theory that predicts the regime boundaries, including what topographies will generate overflows. As observations also suggest there may be overflows in deep canyons where the flow passes over isolated bumps and sills, this parameter range may be particularly significant for understanding the role of boundary layers in the deep ocean.

  13. Boundary layers for self-similar viscous approximations of nonlinear hyperbolic systems

    CERN Document Server

    Christoforou, Cleopatra

    2011-01-01

    We provide a precise description of the set of residual boundary conditions generated by the self-similar viscous approximation introduced by Dafermos et al. We then apply our results, valid for both conservative and non conservative systems, to the analysis of the boundary Riemann problem and we show that, under appropriate assumptions, the limits of the self-similar and the classical vanishing viscosity approximation coincide. We require neither genuinely nonlinearity nor linear degeneracy of the characteristic fields.

  14. Boundary control of a Timoshenko beam system with input dead-zone

    Science.gov (United States)

    He, Wei; Meng, Tingting; Liu, Jin-Kun; Qin, Hui

    2015-06-01

    In this paper, boundary control is designed for a Timoshenko beam system with the input dead-zone. By the Hamilton's principle, the dynamics of the Timoshenko beam system is represented by a distributed parameter model with two partial differential equations and four ordinary differential equations. The bounded part is separated from the input dead-zone and then forms the disturbance-like term together with the boundary disturbance, which finally acts on the Timoshenko beam system. Boundary control, based on the Lyapunov's direct method, is proposed to ensure the Timoshenko beam converge into a small neighbourhood of zero, where stability of the system is also analysed. Besides, the existence and uniqueness of the solution of the Timoshenko beam system are proved. Simulations are provided to reveal the applicability and effectiveness of the proposed control scheme.

  15. Trophic interactions in northern Chile upwelling ecosystem, year 1997

    Directory of Open Access Journals (Sweden)

    Mónica E Barros

    2014-11-01

    Full Text Available A food web model is constructed to describe predator-prey interactions, community structure and trophic flows in northern Chile upwelling ecosystem (18°20'S, 24°S, for the year 1997. The model is built using the Ecopath with Ecosim software version 6.4, and encompasses 21 functional groups, ranging from primary producers (phytoplankton to top predators (birds and marine mammals, the principal fishing resources and the fishery. Input parameters required to build the model were gathered from specialized literature, grey literature and our own estimates. The results indicated that the total biomass (B T was estimated at 624.7 ton km-2. The combined biomass of small pelagic fish represented 26% of B T, while the combined biomass of demersal fish represented only 0.1% of B T. These results highlight the importance of pelagic fish in this system. Predation mortality resulted to be the main source of mortality. Nevertheless, fishing mortality was important in anchovy, mackerel, common dolphinfish and jack mackerel. The mean trophic level of the fishery was estimated as 3.7, with landings sustained mainly by anchovy. Primary production required to sustain the landings (PPR was estimated at 7.5% of calculated total net primary production, which is lower than PPR estimates in other upwelling ecosystems. The average trophic transfer efficiency was 18%, which is in the range (10-20% informed for marine ecosystems. Results indicate that in 1997 the northern Chile marine ecosystem was characterized for being a system far from maturity, dominated in terms of biomass and flows by the pelagic realm.

  16. Boundary-value problems for two-dimensional canonical systems

    NARCIS (Netherlands)

    Hassi, Seppo; De Snoo, H; Winkler, Henrik

    2000-01-01

    The two-dimensional canonical system Jy' = -lHy where the nonnegative Hamiltonian matrix function H(x) is trace-normed on (0,∞) has been studied in a function-theoretic way by L. de Branges. We show that the Hamiltonian system induces a closed symmetric relation which can be reduced to a, not necess

  17. Models of oxic respiration, denitrification and sulfate reduction in zones of coastal upwelling

    Science.gov (United States)

    Canfield, D. E.

    2006-12-01

    Coastal upwelling zones support some of the highest rates of primary production in the oceans. The settling and subsequent decomposition of this organic matter promotes oxygen depletion. In the Eastern tropical North and South Pacific and the Arabian Sea, large tracts of anoxic water develop, where intensive N 2 production through denitrification and anammox accounts for about 1/3 of the total loss of fixed nitrogen in the marine realm. It is curious that despite extensive denitrification in these waters, complete nitrate removal and the onset of sulfate reduction is extremely rare. A simple box model is constructed here to reproduce the dynamics of carbon, oxygen and nutrient cycling in coastal upwelling zones. The model is constructed with five boxes, where water is exchanged between the boxes by vertical and horizontal mixing and advection. These primary physical drivers control the dynamics of the system. The model demonstrates that in the absence of nitrogen fixation, the anoxic waters in a coastal upwelling system will not become nitrate free. This is because nitrate is the limiting nutrient controlling primary production, and if nitrate concentration becomes too low, primary production rate drops and this reduces rates of nitrate removal through N 2 production. With nitrogen fixation, however, complete nitrate depletion can occur and sulfate reduction will ensue. This situation is extremely rare in coastal upwelling zones, probably because nitrogen-fixing bacteria do not prosper in the high nutrient, turbid waters as typically in these areas. Finally, it is predicted here that the chemistry of the upwelling system will develop in a similar matter regardless whether N 2 production is dominated by anaerobic ammonium oxidation (anammox) or canonical heterotrophic denitrification.

  18. SST patterns and dynamics of the southern Senegal-Gambia upwelling center

    Science.gov (United States)

    Ndoye, S.; Capet, X.; Estrade, P.; Sow, B.; Dagorne, D.; Lazar, A.; Gaye, A.; Brehmer, P.

    2014-12-01

    The southern end of the Canary current system comprises of an original upwelling center that has so far received little attention, the Southern Senegal-Gambia Upwelling Center (SSUC). We investigate its dynamical functioning by taking advantage of favorable conditions in terms of limited cloud coverage. Analyses and careful examinations of over 1500 satellite images of sea surface temperature scenes contextualized with respect to wind conditions confirm the regularity and stability of the SSUC dynamical functioning (as manifested by the recurrence and persistence of particular SST patterns). The analyses also reveal subtle aspects of its upwelling structure: shelf break cooling of surface waters consistent with internal tide breaking/mixing; complex interplay between local upwelling and the Mauritanian current off the Cape Verde headland; complexity of the inner-shelf/mid shelf frontal transition. The amplitude of the diurnal cycle suggests that large uncertainties exist in the SSUC heat budget. The studies limitations underscore the need for continuous in situ measurement in the SSUC, particularly of winds.

  19. Performance of Numerical Boundary Condition based on Active Wave Absorption System

    DEFF Research Database (Denmark)

    Trouch, P.; Rouck, J. de; Frigaard, Peter

    2001-01-01

    that was first developed in the context of physical wave flume experiments, using a wave paddle. The method applies to regular and irregular waves. Velocities are measured at one location inside the computational domain. The reflected wave train is separated from the incident wave field in front of a structure......The implementation and performance of a new active wave generating‐absorbing boundary condition for a numerical model based on the Volume Of Fluid (VOF) method for tracking free surfaces is presented. This numerical boundary condition AWAVOF is based on an active wave absorption system...... by means of digital filtering and subsequent superposition of the measured velocity signals. The incident wave signal is corrected, so that the reflected wave is effectively absorbed at the boundary. The effectiveness of the active wave generating‐absorbing boundary condition is proved using numerical...

  20. Port Hamiltonian Formulation of Infinite Dimensional Systems II. Boundary Control by Interconnection

    NARCIS (Netherlands)

    Macchelli, Alessandro; Schaft, Arjan J. van der; Melchiorri, Claudio

    2004-01-01

    In this paper, some new results concerning the boundary control of distributed parameter systems in port Hamiltonian form are presented. The classical finite dimensional port Hamiltonian formulation of a dynamical system has been generalized to the distributed parameter and multi-variable case by ex

  1. Port Hamiltonian formulation of infinite dimensional systems II. Boundary control by interconnection

    NARCIS (Netherlands)

    Macchelli, Alessandro; Schaft, van der Arjan J.; Melchiorri, Claudio

    2004-01-01

    In this paper, some new results concerning the boundary control of distributed parameter systems in port Hamiltonian form are presented. The classical finite dimensional port Hamiltonian formulation of a dynamical system has been generalized to the distributed parameter and multivariable case by ext

  2. Blow-up estimates for semilinear parabolic systems coupled in an equation and a boundary condition

    Institute of Scientific and Technical Information of China (English)

    WANG; Mingxin(

    2001-01-01

    [1]Wang, S., Wang, M. X., Xie, C. H., Reaction-diffusion systems with nonlinear boundary conditions, Z. angew. Math.Phys., 1997, 48(6): 994-1001.[2]Fila, M., Quittner, P., The blow-up rate for a semilinear parabolic system, J. Math. Anal. Appl., 1999, 238: 468-476.[3]Hu, B., Remarks on the blow-up estimate for solutions of the heat equation with a nonlinear boundary condition, Differential Integral Equations, 1996, 9(5): 891-901.[4]Hu, B. , Yin, H. M., The profile near blow-up time for solution of the heat equation with a nonlinear boundary condition,Trans. of Amer. Math. Soc., 1994, 346: 117-135.[5]Amann, H., Parabolic equations and nonlinear boundary conditions, J. of Diff. Eqns., 1988, 72: 201-269.[6]Deng, K., Blow-up rates for parabolic systems, Z. angew. Math. Phys. ,1996, 47: 132-143.[7]Fila, M., Levine, H. A., On critical exponents for a semilinear parabolic system coupled in an equation and a boundary condition, J. Math. Anal. Appl., 1996, 204: 494-521.

  3. Boundary Work: Engaging Knowledge Systems in Co-management of Feral Animals on Indigenous Lands

    Directory of Open Access Journals (Sweden)

    Tabatha J. Wallington

    2012-06-01

    Full Text Available The integration and use of Indigenous knowledge to inform contemporary environmental policy decisions and management solutions is a growing global phenomenon. However, there is little critical inquiry about how the interactions between scientific and Indigenous knowledge (IK systems can be effectively negotiated for the joint management of social-ecological systems. Such issues are urgent on Indigenous lands where co-management efforts respond to pressing conservation agendas and where the contribution of scientific knowledge and IK is required to better understand and manage complex social-ecological systems. We draw on the notion of boundary work to examine how interaction at the boundaries of scientific and IK systems can be managed effectively as a contribution to co-management. The case study of feral animal co-management in Australia's Kakadu National Park illuminates the work required for local co-managers to bridge the divide between scientific and IK systems and to ensure the translation of knowledge for management decisions. Attributes of effective boundary work demonstrated in this case include: meaningful participation in agenda setting and joint knowledge production to enable co-managers to translate available knowledge into joint feral animal programs, Indigenous and non-Indigenous ranger efforts to broker interactions between knowledge systems that are supported by co-governance arrangements to ensure that boundary work remains accountable, and the production of collaboratively built boundary objects (e.g., feral animal impact assessment data that helps to coordinate local action between co-managers. This case study illustrates the contribution of boundary work to local co-manager efforts to translate across knowledge systems and across the knowledge-action divide, even when consensus is difficult to achieve.

  4. Initial-boundary value problems for second order systems of partial differential equations

    OpenAIRE

    Kreiss, Heinz-Otto; Ortiz, Omar E.; Petersson, N. Anders

    2010-01-01

    We develop a well-posedness theory for second order systems in bounded domains where boundary phenomena like glancing and surface waves play an important role. Attempts have previously been made to write a second order system consisting of n equations as a larger first order system. Unfortunately, the resulting first order system consists, in general, of more than 2n equations which leads to many complications, such as side conditions which must be satisfied by the solution of the larger firs...

  5. Nitrate reducing activity pervades surface waters during upwelling.

    Digital Repository Service at National Institute of Oceanography (India)

    Fernandes, S.O.; Halarnekar, R.; Malik, A.; Vijayan, V.; Varik, S.; RituKumari; Jineesh V.K.; Gauns, M.U.; Nair, S.; LokaBharathi, P.A.

    (Hernandez-Leon et al., 2008) could also be a key factor contributing to NH4+ generation off Trivandrum. Despite such observations, DNC values suggest that upwelling is still in the initial stages. In an upwelling area, NW of Spain, Varela et al. (2003...., 2008. Variability in biological responses influenced by upwelling events in the Eastern Arabian Sea. J. Mar. Sys. 74(1-2), 545–560. Hernandez-Leon, S., Fraga, C., Ikeda, T., 2008. A global estimation of mesozooplankton ammonium excretion in the open...

  6. Existence of solutions for critical elliptic systems with boundary singularities

    Directory of Open Access Journals (Sweden)

    Jianfu Yang

    2013-04-01

    Full Text Available This article concerns the existence of positive solutions to the nonlinear elliptic system involving critical Hardy-Sobolev exponent $$displaylines{ -Delta u= frac{2lambdaalpha}{alpha+eta} frac{u^{alpha-1} v^eta}{|pi(x|^s}- u^p, quad hbox{in } Omega,cr -Delta v= frac{2lambdaeta}{alpha+eta} frac{u^alpha v^{eta-1}}{|pi(x|^s}- v^p, quad hbox{in } Omega,cr u>0,quad v>0, quad hbox{in } Omega,cr u=v=0, quad hbox{on } partialOmega, }$$ where $Ngeq 4$ and $Omega$ is a $C^1$ bounded domain in $mathbb{R}^N$, $01$, $lambda>0$ and $1leq p

  7. Simulation of a free-surface and seepage face using boundary-fitted coordinate system method

    Science.gov (United States)

    Lee, Kang-Kun; Leap, Darrell I.

    1997-09-01

    The boundary-fitted coordinate (BFC) system method is applied to simulate steady groundwater seepage with a free-surface and seepage face using the finite-difference method. The BFC system method eliminates the difficulty of fitting finite-difference grids to a changeable free-surface which is not known a priori but will be obtained as part of a solution. Also, grid generation with this approach is simpler than with the finite-element method. At each iterative sweep, the changeable free-surface becomes a part of the boundary-fitted grid lines, making boundary condition implementation easy and accurate. An example problem demonstrating the simulation procedure and numerical results compares very well with the analytical solution.

  8. Long-term frequency stabilization system for external cavity diode laser based on mode boundary detection.

    Science.gov (United States)

    Xu, Zhouxiang; Huang, Kaikai; Jiang, Yunfeng; Lu, Xuanhui

    2011-12-01

    We have realized a long-term frequency stabilization system for external cavity diode laser (ECDL) based on mode boundary detection method. In this system, the saturated absorption spectroscopy was used. The current and the grating of the ECDL were controlled by a computer-based feedback control system. By checking if there are mode boundaries in the spectrum, the control system determined how to adjust current to avoid mode hopping. This procedure was executed periodically to ensure the long-term stabilization of ECDL in the absence of mode hops. This diode laser system with non-antireflection coating had operated in the condition of long-term mode-hop-free stabilization for almost 400 h, which is a significant improvement of ECDL frequency stabilization system.

  9. Systemic effects of geoengineering by terrestrial carbon dioxide removal on carbon related planetary boundaries

    Science.gov (United States)

    Heck, Vera; Donges, Jonathan; Lucht, Wolfgang

    2015-04-01

    The planetary boundaries framework as proposed by Rockström et al. (2009) provides guidelines for ecological boundaries, the transgression of which is likely to result in a shift of Earth system functioning away from the relatively stable Holocene state. As the climate change boundary is already close to be transgressed, several geoengineering (GE) methods are discussed, aiming at a reduction of atmospheric carbon concentrations to control the Earth's energy balance. One of the proposed GE methods is carbon extraction from the atmosphere via biological carbon sequestration. In case mitigation efforts fail to substantially reduce greenhouse gas emissions, this form of GE could act as potential measure to reduce atmospheric carbon dioxide concentrations. We here study the possible influences of human interactions in the Earth system on carbon related planetary boundaries in the form of geoengineering (terrestrial carbon dioxide removal). We use a conceptual model specifically designed to investigate fundamental carbon feedbacks between land, ocean and atmosphere (Anderies et al., 2013) and modify it to include an additional geoengineering component. With that we analyze the existence and stability of a safe operating space for humanity, which is here conceptualized in three of the 9 proposed dimensions, namely climate change, ocean acidification and land-use. References: J. M. Anderies et al., The topology of non-linear global carbon dynamics: from tipping points to planetary boundaries. Environ. Res. Lett., 8(4):044048 (2013) J. Rockström et al., A safe operating space for humanity. Nature 461 (7263), 472-475 (2009)

  10. Optimal boundary control of parabolic system on doubly connected region in new space

    Institute of Scientific and Technical Information of China (English)

    陈任昭

    1995-01-01

    The optimal boundary control of the system governed by parabolic partial differential equations on a doubly connected region in the new space advanced by Lions is discussed. It proves the necessary and sufficient conditions for a control to be optimal and obtains the optimality system consisting of partial differential equations and variational inequalities. And the application of penalty shifting method to the approximate solution of control problems for the system is researched.

  11. THE NONLINEAR BOUNDARY VALUE PROBLEM FOR A CLASS OF INTEGRO-DIFFERENTIAL SYSTEM

    Institute of Scientific and Technical Information of China (English)

    Rongrong Tang

    2006-01-01

    In this paper, using the theory of differential inequalities, we study the nonlinear boundary value problem for a class of integro-differential system. Under appropriate assumptions, the existence of solution is proved and the uniformly valid asymptotic expansions for arbitrary n-th order approximation and the estimation of remainder term are obtained simply and conveniently.

  12. POSITIVE SOLUTIONS TO SYSTEMS OF SECOND ORDER NONLOCAL BOUNDARY VALUE PROBLEMS WITH FIRST ORDER DERIVATIVES

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    This paper investigates the existence of positive solutions to systems of second order nonlocal boundary value problems with first order derivatives, in which the nonlinear term is not required to be continuous and involves first order derivatives. The main tool used in this paper is a fixed point index theory in a cone.

  13. An Examination of the Social Boundaries of the Migratory Labor System of the Atlantic Coast Stream.

    Science.gov (United States)

    Stewart, Judith Anne

    The purpose of this thesis was to define key elements of the migrant labor system structure by mapping its boundaries. Elements of the social structure in areas where large numbers of potential migrants were found and personal reasons given for joining the migrant stream were examined to understand how the structure is perceived by and motivates…

  14. Symmetric solutions of singular nonlocal boundary value problems for systems of differential equation

    Institute of Scientific and Technical Information of China (English)

    KANG Ping; YAO Jianli

    2009-01-01

    In this paper, we investigate the existence of symmetric solutions of singular nonlocal boundary value problems for systems of differential equations. Our analysis relies on a nonlinear alternative of Leray - schauder type. Our results presented here unify, generalize and significantly improve many known results in the literature.

  15. Clinical simulation as a boundary object in design of health IT-systems

    DEFF Research Database (Denmark)

    Rasmussen, Stine Loft; Jensen, Sanne; Lyng, Karen Marie

    2013-01-01

    Healthcare organizations are very complex, holding numerous stakeholders with various approaches and goals towards the design of health IT-systems. Some of these differences may be approached by applying the concept of boundary objects in a participatory IT-design process. Traditionally clinical ...

  16. Multiple Positive Solutions of Boundary Value Problems for Systems of Nonlinear Third-Order Differential Equations

    Institute of Scientific and Technical Information of China (English)

    Yaohong LI; Xiaoyan ZHANG

    2013-01-01

    In this paper,we consider boundary value problems for systems of nonlinear thirdorder differential equations.By applying the fixed point theorems of cone expansion and compression of norm type and Leggett-Williams fixed point theorem,the existence of multiple positive solutions is obtained.As application,we give some examples to demonstrate our results.

  17. Flow system boundary by D'Agnese and others (1997) for the Death Valley regional ground-water flow system study, Nevada and California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This digital data set defines the flow-system boundary encompassing the regional ground-water flow model by D'Agnese and others (1997). The boundary encompasses an...

  18. The minimal habitat size for spreading in a weak competition system with two free boundaries

    Science.gov (United States)

    Wu, Chang-Hong

    2015-08-01

    In this paper, we focus on the dynamics for a Lotka-Volterra type weak competition system with two free boundaries, where free boundaries which may intersect each other as time evolves are used to describe the spreading of two competing species, respectively. In the weak competition case, the dynamics of this model can be classified into four cases, which forms a spreading-vanishing quartering. The notion of the minimal habitat size for spreading is introduced to determine if species can always spread. Some sufficient conditions for spreading and vanishing are established. Also, when spreading occurs, some rough estimates for spreading speed and the long-time behavior of solutions are established.

  19. Human-Environment System Boundaries: A Case Study of the Honghe Hani Rice Terraces as a World Heritage Cultural Landscape

    Directory of Open Access Journals (Sweden)

    Honglian Hua

    2015-08-01

    Full Text Available Any World Heritage Cultural Landscape requires a clear boundary for administration. One of the administrative goals is sustainability. There is no widely identified way to demarcate the boundary of a World Heritage Cultural Landscape. This paper aims to explore a methodology framework to provide a holistic perspective for demarcating boundaries for a World Heritage Cultural Landscape. Honghe Hani Rice Terraces (HHRT in Yunnan Province is a new World Heritage Cultural Landscape in China. We use it as a research area to illustrate the methodology framework. The framework of methodology is constructed based on four scales of a human-environment system identified by Anne Buttimer. It is used to describe the level of the sustainability of local economy, social organization, natural environment and people’s understanding of the human-environment. Four types of boundaries were investigated in this area. They are the boundary of Malizhai River Basin, the boundary of local water-allocation organization, the boundary of the economic network and the perceptual boundary of the human-environment system. With a comprehensive perspective, we integrated the four types of boundaries to judge the boundary of the core area of HHRT by three criteria, they are: Environmental sustainability, social justice, and the ability to create a new human-environment system. We conclude that some parts of the boundary of the core area of HHRT do not fit the criteria of sustainable development.

  20. Numerical investigation of the boundary value problem for the carleman system of equations

    Directory of Open Access Journals (Sweden)

    Vasilyeva Ol’ga Aleksandrovna

    2016-12-01

    Full Text Available The boundary value problem for the Carleman system of equations is considered. The problem is investigated numerically for initial conditions which are perturbed nonnegative stationary solutions of the problem. First point of the paper is numerical investigation of solution of the boundary value problem with perturbed positive stationary solutions as an initial condition. The time dependence of the maximum deviation of the solution of the stationary solution problem of stationary solutions is investigated. The results of numerical problem solution are presented. The time dependence of the energy of perturbations of stationary solutions of the problem is presented. The solution stabilization to the stationary solution problem is obtained. The solution stabilization time is compared with stabilization time in periodic case. Second point of the paper is numerical investigation of solution of the boundary-value problem with perturbed zero stationary solutions as an initial condition. The results of numerical problem solution are presented.

  1. On the Navier-Stokes system with the Coulomb friction law boundary condition

    Science.gov (United States)

    Bălilescu, Loredana; San Martín, Jorge; Takahashi, Takéo

    2017-02-01

    We propose a new model for the motion of a viscous incompressible fluid. More precisely, we consider the Navier-Stokes system with a boundary condition governed by the Coulomb friction law. With this boundary condition, the fluid can slip on the boundary if the tangential component of the stress tensor is too large. We prove the existence and uniqueness of weak solution in the two-dimensional problem and the existence of at least one solution in the three-dimensional case, together with regularity properties and an energy estimate. We also propose a fully discrete scheme of our problem using the characteristic method, and we present numerical simulations in two physical examples.

  2. CALL FOR PAPERS: Topical issue on the nonstationary Casimir effect and quantum systems with moving boundaries

    Science.gov (United States)

    Barton, Gabriel; Dodonov, Victor V.; Man'ko, Vladimir I.

    2004-05-01

    The past few years have seen a growing interest in quantum mechanical systems with moving boundaries. One of its manifestations was the First International Workshop on Problems with Moving Boundaries organized by Professor J Dittrich in Prague in October 2003. Another event in this series will be the (first) International Workshop on the Dynamical Casimir Effect in Padua in June 2004, organized by Professor G Carugno (see webpage www.pd.infn.it/casimir/ for details). As Guest Editors we invite researchers working in any area related to moving boundaries to contribute to a Topical Issue of Journal of Optics B: Quantum and Semiclassical Optics on the nonstationary Casimir effect and quantum systems with moving boundaries. Our intention is to cover a wide range of topics. In particular, we envisage possible contributions in the following areas: Theoretical and experimental studies on quantum fields in cavities with moving boundaries and time-dependent media. This area includes, in particular, various manifestations of the nonstationary (dynamical) Casimir effect, such as creation of quanta and modifications of Casimir force due to the motion of boundaries. Other relevant subjects are: generation and evolution of nonclassical states of fields and moving mirrors; interaction between quantized fields and atoms in cavities with moving boundaries; decoherence and entanglement due to the motion of boundaries; field quantization in nonideal cavities with moving boundaries taking into account losses and dispersion; nano-devices with moving boundaries. Quantum particles in domains confined with moving boundaries. This area includes: new exact and approximate solutions of the evolution equations (Schrödinger, Klein-Gordon, Dirac, Fokker-Planck, etc); quantum carpets and revivals; escape and tunnelling through moving barriers; evolution of quantum packets in the presence of moving boundaries; ultracold atoms (ions) in traps with moving boundaries. The topical issue is scheduled

  3. R\\'enyi entanglement entropies of descendant states in critical systems with boundaries: conformal field theory and spin chains

    CERN Document Server

    Taddia, Luca; Pálmai, Tamás

    2016-01-01

    We discuss the R\\'enyi entanglement entropies of descendant states in critical one-dimensional systems with boundaries, that map to boundary conformal field theories (CFT) in the scaling limit. We unify the previous CFT approaches to describe primary and descendant states in systems with both open and closed boundaries. We apply the technique to critical systems belonging to different universality classes with non-trivial boundary conditions that preserve conformal invariance, and compare the results to numerical data obtained on finite spin chains.

  4. Distributed tuning of boundary resources: the case of Apple's iOS service system

    OpenAIRE

    Eaton, Ben; Elaluf-Calderwood, Silvia; Sorensen, Carsten; Yoo, Youngjin

    2015-01-01

    The digital age has seen the rise of service systems involving highly distributed, heterogeneous, and resource-integrating actors whose relationships are governed by shared institutional logics, standards, and digital technology. The cocreation of service within these service systems takes place in the context of a paradoxical tension between the logic of generative and democratic innovations and the logic of infrastructural control. Boundary resources play a critical role in managing the ten...

  5. Solution of the boundary value problem for optimal escape in continuous stochastic systems and maps.

    OpenAIRE

    S; Beri; Mannella, R.; Luchinsky, Dmitry G.; Silchenko, A. N.; McClintock, Peter V. E.

    2005-01-01

    Topologies of invariant manifolds and optimal trajectories are investigated in stochastic continuous systems and maps. A topological method is introduced that simplifies the solution of boundary value problems: The activation energy is calculated as a function of a set of parameters characterizing the initial conditions of the escape path. The method is applied explicitly to compute the optimal escape path and the activation energy for a variety of dynamical systems and maps.

  6. Stability result of the Timoshenko system with delay and boundary feedback

    KAUST Repository

    Said-Houari, Belkacem

    2012-01-06

    Our interest in this paper is to analyse the asymptotic behaviour of a Timoshenko beam system together with two boundary controls, with delay terms in the first and second equation. Assuming the weights of the delay are small enough, we show that the system is well-posed using the semigroup theory. Furthermore, we introduce a Lyapunov functional that gives the exponential decay of the total energy. © 2012 The author.

  7. Modelling an alkenone-like proxy record in the NW African upwelling

    OpenAIRE

    2006-01-01

    A regional biogeochemical model is applied to the NW African coastal upwelling between 19° N and 27° N to investigate how a water temperature proxy is produced at the sea surface and recorded in the slope sediments. The biological model has two phytoplankton groups, to distinguish an alkenone producer group (considered as coccolithophores) from other phytoplankton. The Regional Ocean Modelling System (ROMS) is used to simulate the ocean circulation, and takes advantage of the ...

  8. Phytoplankton community and environmental correlates in a coastal upwelling zone along western Taiwan Strait

    Science.gov (United States)

    Wang, Yu; Kang, Jian-hua; Ye, You-yin; Lin, Geng-ming; Yang, Qing-liang; Lin, Mao

    2016-02-01

    Upwelling system in western Taiwan Strait is important for facilitating the fishery production. This study investigated hydro-chemical properties, phytoplankton biomass, phytoplankton species composition, three-dimensional (horizontal, vertical and transect) distribution of phytoplankton abundance, as well as phytoplankton annual variation and the correlation of phytoplankton community with the upwelling of underlying current and nutrients according to samples of Fujian-Guangdong coastal upwelling zone in western Taiwan Strait from August 27 to September 8, 2009. The results manifest that the nutrient-rich cold and high salinity current on the continental shelf of South China Sea upwells to the Fujian-Guangdong coastal waters through Taiwan Bank and the surging strength to surface is weak while strong at 30-m layer. The thermohaline center of coastal upwelling shifts to the east of Dongshan Island and expanded to offshore waters in comparison with previous records. A total of 137 phytoplankton species belonging to 59 genera in 4 phyla are identified excluding the unidentified species. Diatom is the first major group and followed by dinoflagellate. Cyanobacteria mainly composed by three Trichodesmium species account for a certain proportions, while Chrysophyta are only found in offshore waters. The dominant species include Thalassionema nitzschioides, Pseudo-nitzschia pungens, Thalassionema frauenfeldii, Pseudo-nitzschia delicatissima, Rhizosolenia styliformis, Chaetoceros curvisetus, Diplopsalis lenticula and Trichodesmium thiebautii. Phytoplankton community mainly consists of eurythermal and eurytopic species, followed by warm-water species, tropic high-salinity species and oceanic eurythermic species in order. Phytoplankton abundance ranges from 1.00 × 102 ind./L ~ 437.22 × 102 ind./L with an average of 47.36 × 102 ind./L. For vertical distribution, maximum abundance is found at 30 m-depth and the surface comes second. Besides, the abundance below 30 m

  9. Solutions Stability of Initial Boundary Problem, Modeling of Dynamics of Some Discrete Continuum Mechanical System

    Directory of Open Access Journals (Sweden)

    D. A. Eliseev

    2015-01-01

    Full Text Available The solution stability of an initial boundary problem for a linear hybrid system of differential equations, which models the rotation of a rigid body with two elastic rods located in the same plane is studied in the paper. To an axis passing through the mass center of the rigid body perpendicularly to the rods location plane is applied the stabilizing moment proportional to the angle of the system rotation, derivative of the angle, integral of the angle. The external moment provides a feedback. A method of studying the behavior of solutions of the initial boundary problem is proposed. This method allows to exclude from the hybrid system of differential equations partial differential equations, which describe the dynamics of distributed elements of a mechanical system. It allows us to build one equation for an angle of the system rotation. Its characteristic equation defines the stability of solutions of all the system. In the space of feedback-coefficients the areas that provide the asymptotic stability of solutions of the initial boundary problem are built up.

  10. A system level boundary scan controller board for VME applications [to CERN experiments

    CERN Document Server

    Cardoso, N; Da Silva, J C

    2000-01-01

    This work is the result of a collaboration between INESC and LIP in the CMS experiment being conducted at CERN. The collaboration addresses the application of boundary scan test at system level namely the development of a VME boundary scan controller (BSC) board prototype and the corresponding software. This prototype uses the MTM bus existing in the VME64* backplane to apply the 1149.1 test vectors to a system composed of nineteen boards, called here units under test (UUTs). A top-down approach is used to describe our work. The paper begins with some insights about the experiment being conducted at CERN, proceed with system level considerations concerning our work and with some details about the BSC board. The results obtained so far and the proposed work is reviewed in the end of this contribution. (11 refs).

  11. Multi-component Cahn-Hilliard system with different boundary conditions in complex domains

    Science.gov (United States)

    Li, Yibao; Choi, Jung-Il; Kim, Junseok

    2016-10-01

    We propose an efficient phase-field model for multi-component Cahn-Hilliard (CH) systems in complex domains. The original multi-component Cahn-Hilliard system with a fixed phase is modified in order to make it suitable for complex domains in the Cartesian grid, along with contact angle or no mass flow boundary conditions on the complex boundaries. The proposed method uses a practically unconditionally gradient stable nonlinear splitting numerical scheme. Further, a nonlinear full approximation storage multigrid algorithm is used for solving semi-implicit formulations of the multi-component CH system, incorporated with an adaptive mesh refinement technique. The robustness of the proposed method is validated through various numerical simulations including multi-phase separations via spinodal decomposition, equilibrium contact angle problems, and multi-phase flows with a background velocity field in complex domains.

  12. A method of boundary parameter estimation for a two-dimensional diffusion system under noisy observations

    Science.gov (United States)

    Sunahara, Y.; Kojima, F.

    1988-01-01

    The purpose of this paper is to establish a method for identifying unknown parameters involved in the boundary state of a class of diffusion systems under noisy observations. A mathematical model of the system dynamics is given by a two-dimensional diffusion equation. Noisy observations are made by sensors allocated on the system boundary. Starting with the mathematical model mentioned above, an online parameter estimation algorithm is proposed within the framework of the maximum likelihood estimation. Existence of the optimal solution and related necessary conditions are discussed. By solving a local variation of the cost functional with respect to the perturbation of parameters, the estimation mechanism is proposed in a form of recursive computations. Finally, the feasibility of the estimator proposed here is demonstrated through results of digital simulation experiments.

  13. Modelling the upwelling offthe east Hainan Island coast in summer 2010

    Science.gov (United States)

    Bai, Peng; Gu, Yanzhen; Li, Peiliang; Wu, Kejian

    2016-11-01

    A synoptic-scale upwelling event that developed offthe east coast of the Hainan Island (EHIU) in the summer of 2010 is defined well via processing the Moderate Resolution Imaging Spectroradiometer (MODIS) sea surface temperature (SST) data. The Regional Ocean Modeling System (ROMS) with high spatial resolution has been used to investigate this upwelling event. By comparing the ROMS results against tide station data, Argo float profiles and MODIS SST, it is confirmed that the ROMS reproduces the EHIU well. The cooler-water core (CWC) distinguished by waters wind stress curl that dominated the east Qiongzhou Strait mouth area suppressed the intensity of the CWC by 0.2-0.4°C. Further, nonlinear interaction between tidal currents and wind stress enhanced vertical mixing greatly, which would benefit the development of the CWC.

  14. An equilibrium model for the coupled ocean-atmosphere boundary layer in the tropics

    Science.gov (United States)

    Sui, C.-H.; Lau, K.-M.; Betts, Alan K.

    A coupled model is used to study the equilibrium state of the ocean-atmosphere boundary layer in the tropics. The atmospheric model is a one-dimensional thermodynamic model for a partially mixed, partly cloudy convective boundary layer (CBL), including the effects of cloud-top subsidence, surface momentum and heat (latent and sensible) fluxes, and realistic radiative transfer for both shortwaves and longwaves (Betts and Ridgway, 1988; 1989). The oceanic model is a thermodynamic model for a well-mixed layer, with a closure constraint based on a one-dimensional turbulent kinetic energy (TKE) equation following Kraus and Turner (1967). Results of several sets of experiments are reported in this paper. In the first two sets of experiments, with sea surface temperature (SST) specified, we solve the equilibrium state of the coupled system as a function of SST for a given surface wind (case 1) and as a function of surface wind for a given SST (case 2). In both cases the depth of the CBL and the ocean mixed layer (OML) increases and the upwelling below the OML decreases, corresponding to either increasing SST or increasing surface wind. The deepening of the equilibrium CBL is primarily linked to the increase of CBL moisture with increasing SST and surface wind. The increase of OML depth and decrease of upwelling are due to a decrease of net downward heat flux with increasing SST and the generation of TKE by increasing wind. In another two sets of experiments, we solve for the coupled ocean-atmosphere model iteratively as a function of surface wind for a fixed upwelling (case 3) and a fixed OML depth (case 4). SST falls with increasing wind in both cases, but the fall is steeper in case 4, because the OML depth is fixed, whereas in case 3 the depth is allowed to deepen and the cooling is spread over a larger mass of water. The decrease of evaporation with increasing wind in case 4 leads to a very dry and shallow CBL. Results of further experiments with surface wind and SST

  15. Dynamic Analysis of HSDB System and Evaluation of Boundary Non-linearity through Experiments

    Directory of Open Access Journals (Sweden)

    K. Chandrakar

    2016-04-01

    Full Text Available This paper deals with mechanical design and development of high speed digital board (HSDB system which consists of printed circuit board (PCB with all electronic components packaged inside the cavity for military application. The military environment poses a variety of extreme dynamic loading conditions, namely, quasi static, vibration, shock and acoustic loads that can seriously degrade or even cause failure of electronics. The vibrational requirement for the HSDB system is that the natural frequency should be more than 200 Hz and sustain power spectrum density of 14.8 Grms in the overall spectrum. Structural integrity of HSDB is studied in detail using finite element analysis (FEA tool against the dynamic loads and configured the system. Experimental vibration tests are conducted on HSDB with the help of vibration shaker and validated the FE results. The natural frequency and maximum acceleration response computed from vibration tests for the configured design were found. The finite element results show a good correlation with the experiment results for the same boundary conditions. In case of fitment scenario of HSDB system, it is observed that the influence of boundary non-linearity during experiments. This influence of boundary non-linearity is evaluated to obtain the closeout of random vibration simulation results.

  16. The effect of system boundaries on the mean free path for confined gases

    Directory of Open Access Journals (Sweden)

    Sooraj K. Prabha

    2013-10-01

    Full Text Available The mean free path of rarefied gases is accurately determined using Molecular Dynamics simulations. The simulations are carried out on isothermal argon gas (Lennard-Jones fluid over a range of rarefaction levels under various confinements (unbounded gas, parallel reflective wall and explicit solid platinum wall bounded gas in a nanoscale domain. The system is also analyzed independently in constitutive sub-systems to calculate the corresponding local mean free paths. Our studies which predominate in the transition regime substantiate the boundary limiting effect on mean free paths owing to the sharp diminution in molecular free paths near the planar boundaries. These studies provide insight to the transport phenomena of rarefied gases through nanochannels which have established their potential in microscale and nanoscale heat transfer applications.

  17. GLOBAL C1 SOLUTION TO THE INITIAL-BOUNDARY VALUE PROBLEM FOR DIAGONAL HYPERBOLIC SYSTEMS WITH LINEARLY DEGENERATE CHARACTERISTICS

    Institute of Scientific and Technical Information of China (English)

    Li Ta-tsien(李大潜); Peng Yue-Jun

    2003-01-01

    Abstract We prove that the C0 boundedness of solution impliesthe global existence and uniqueness of C1 solution to the initial-boundary value problem for linearly degenerate quasilinear hyperbolic systems of diagonal form with nonlinear boundary conditions. Thus, if the C1 solution to the initial-boundary value problem blows up in a finite time, then the solution itself must tend to the infinity at the starting point of singularity.

  18. Changes in optical characteristics of surface microlayers hint to photochemically and microbially-mediated DOM turnover in the upwelling region off Peru

    Science.gov (United States)

    Galgani, L.; Engel, A.

    2015-12-01

    The coastal upwelling system off Peru is characterized by high biological activity and a pronounced subsurface oxygen minimum zone, as well as associated emissions of atmospheric trace gases such as N2O, CH4 and CO2. During the Meteor (M91) cruise to the Peruvian upwelling system in 2012, we investigated the composition of the sea-surface microlayer (SML), the oceanic uppermost boundary directly subject to high solar radiation, often enriched in specific organic compounds of biological origin like Chromophoric Dissolved Organic Matter (CDOM) and marine gels. In the SML, the continuous photochemical and microbial recycling of organic matter may strongly influence gas exchange between marine systems and the atmosphere. In order to understand organic matter cycling in surface films, we analyzed SML and underlying water samples at 38 stations determining DOC concentration, amino acid composition, marine gels, CDOM and bacterial and phytoplankton abundance as indicators of photochemical and microbial alteration processes. CDOM composition was characterized by spectral slope (S) values and Excitation-Emission Matrix fluorescence (EEMs), which allow to track changes in molecular weight (MW) of DOM, and to determine potential DOM sources and sinks. We identified five fluorescent components of the CDOM pool, of which two had excitation/emission characteristics of protein-like fluorophores and were highly enriched in the SML. CDOM composition and changes in spectral slope properties suggested a local microbial release of HMW DOM directly in the SML as a response to light exposure in this extreme environment. Our results suggest that microbial and photochemical processes play an important role for the production, alteration and loss of optically active substances in the SML.

  19. Finite difference method of first boundary problem for quasilinear parabolic systems (III)——Stability

    Institute of Scientific and Technical Information of China (English)

    周毓麟; 沈隆钧; 袁光伟

    1996-01-01

    The explicit, weak and strong implicit difference solution for the first boundary problem ofquasilinear parabolic system is considered:where u,, and f are m-dimensional vector valued functions, A is an m x m positively definite matrix, andFor this problem, the absolute and relative stability for the general difference schemes is justifiedin the sense of the continuous dependence of the discrete vector solution of the difference schemes on the discrete data of the original problems.

  20. Unique Solution of a Coupled Fractional Differential System Involving Integral Boundary Conditions from Economic Model

    Directory of Open Access Journals (Sweden)

    Rui Li

    2013-01-01

    Full Text Available We study the existence and uniqueness of the positive solution for the fractional differential system involving the Riemann-Stieltjes integral boundary conditions , , , , , and , where , , and and are the standard Riemann-Liouville derivatives, and are functions of bounded variation, and and denote the Riemann-Stieltjes integral. Our results are based on a generalized fixed point theorem for weakly contractive mappings in partially ordered sets.

  1. Accurate numerical schemes for approximating initial-boundary value problems for systems of conservation laws

    CERN Document Server

    Mishra, Siddhartha

    2011-01-01

    Solutions of initial-boundary value problems for systems of conservation laws depend on the underlying viscous mechanism, namely different viscosity operators lead to different limit solutions. Standard numerical schemes for approximating conservation laws do not take into account this fact and converge to solutions that are not necessarily physically relevant. We design numerical schemes that incorporate explicit information about the underlying viscosity mechanism and approximate the physically relevant solution. Numerical experiments illustrating the robust performance of these schemes are presented.

  2. Determination of the carbon budget of a pasture: effect of system boundaries and flux uncertainties

    Science.gov (United States)

    Felber, Raphael; Bretscher, Daniel; Münger, Andreas; Neftel, Albrecht; Ammann, Christof

    2016-05-01

    Carbon (C) sequestration in the soil is considered as a potential important mechanism to mitigate greenhouse gas (GHG) emissions of the agricultural sector. It can be quantified by the net ecosystem carbon budget (NECB) describing the change of soil C as the sum of all relevant import and export fluxes. NECB was investigated here in detail for an intensively grazed dairy pasture in Switzerland. Two budget approaches with different system boundaries were applied: NECBtot for system boundaries including the grazing cows and NECBpast for system boundaries excluding the cows. CO2 and CH4 exchange induced by soil/vegetation processes as well as direct emissions by the animals were derived from eddy covariance measurements. Other C fluxes were either measured (milk yield, concentrate feeding) or derived based on animal performance data (intake, excreta). For the investigated year, both approaches resulted in a small near-neutral C budget: NECBtot -27 ± 62 and NECBpast 23 ± 76 g C m-2 yr-1. The considerable uncertainties, depending on the approach, were mainly due to errors in the CO2 exchange or in the animal-related fluxes. The comparison of the NECB results with the annual exchange of other GHG revealed CH4 emissions from the cows to be the major contributor in terms of CO2 equivalents, but with much lower uncertainty compared to NECB. Although only 1 year of data limit the representativeness of the carbon budget results, they demonstrate the important contribution of the non-CO2 fluxes depending on the chosen system boundaries and the effect of their propagated uncertainty in an exemplary way. The simultaneous application and comparison of both NECB approaches provides a useful consistency check for the carbon budget determination and can help to identify and eliminate systematic errors.

  3. Nontrivial Solutions of Superquadratic Hamiltonian Systems with Lagrangian Boundary Conditions and the L-index Theory

    Institute of Scientific and Technical Information of China (English)

    Chong LI; Chungen LIU

    2008-01-01

    In this paper, the authors study the existence of nontrivial solutions for the Hamiltonian systems z(t) = J▽H(t, z(t)) with Lagrangian boundary conditions, where (H)(t,z) = 1/2((B)(t)z,z) + (H)(t,z), (B)(t) is a semipositive symmetric continuous matrix and (H) satisfies a superquadratic condition at infinity. We also obtain a result about the L-index.

  4. Monotone methods for solving a boundary value problem of second order discrete system

    Directory of Open Access Journals (Sweden)

    Wang Yuan-Ming

    1999-01-01

    Full Text Available A new concept of a pair of upper and lower solutions is introduced for a boundary value problem of second order discrete system. A comparison result is given. An existence theorem for a solution is established in terms of upper and lower solutions. A monotone iterative scheme is proposed, and the monotone convergence rate of the iteration is compared and analyzed. The numerical results are given.

  5. Isotopic and enzymatic analyses of planktonic nitrogen utilisation in the vicinity of Cape Sines (Portugal) during weak upwelling activity

    Science.gov (United States)

    Slawyk, Gerd; Coste, Bernard; Collos, Yves; Rodier, Martine

    1997-01-01

    ) absolute and Chl a-specific nitrate uptake rates (10.4 nM h -1, 7.5 nmol μ -1 h -1) compared to the mean rates during weak upwelling (1.7 nM h -1, 1.5 nmol μ -1 h -1). From a comparison with the neighbouring Moroccan upwelling, it is assumed that new production in the Portuguese upwelling averages 50 nM h -1. Thus, this upwelling would rank with the northwest African upwelling system off Cape Blanc or with the Californian upwelling at Point Conception for the capacity of new production, but seems to be much less efficient (seven-fold) than the highly permanent Peru upwelling.

  6. Biogenic halocarbons from the Peruvian upwelling region as tropospheric halogen source

    Science.gov (United States)

    Hepach, Helmke; Quack, Birgit; Tegtmeier, Susann; Engel, Anja; Bracher, Astrid; Fuhlbrügge, Steffen; Galgani, Luisa; Atlas, Elliot L.; Lampel, Johannes; Frieß, Udo; Krüger, Kirstin

    2016-09-01

    Halocarbons are produced naturally in the oceans by biological and chemical processes. They are emitted from surface seawater into the atmosphere, where they take part in numerous chemical processes such as ozone destruction and the oxidation of mercury and dimethyl sulfide. Here we present oceanic and atmospheric halocarbon data for the Peruvian upwelling zone obtained during the M91 cruise onboard the research vessel METEOR in December 2012. Surface waters during the cruise were characterized by moderate concentrations of bromoform (CHBr3) and dibromomethane (CH2Br2) correlating with diatom biomass derived from marker pigment concentrations, which suggests this phytoplankton group is a likely source. Concentrations measured for the iodinated compounds methyl iodide (CH3I) of up to 35.4 pmol L-1, chloroiodomethane (CH2ClI) of up to 58.1 pmol L-1 and diiodomethane (CH2I2) of up to 32.4 pmol L-1 in water samples were much higher than previously reported for the tropical Atlantic upwelling systems. Iodocarbons also correlated with the diatom biomass and even more significantly with dissolved organic matter (DOM) components measured in the surface water. Our results suggest a biological source of these compounds as a significant driving factor for the observed large iodocarbon concentrations. Elevated atmospheric mixing ratios of CH3I (up to 3.2 ppt), CH2ClI (up to 2.5 ppt) and CH2I2 (3.3 ppt) above the upwelling were correlated with seawater concentrations and high sea-to-air fluxes. During the first part of the cruise, the enhanced iodocarbon production in the Peruvian upwelling contributed significantly to tropospheric iodine levels, while this contribution was considerably smaller during the second part.

  7. Modelling Upwelling Irradiance using Secchi disk depth in lake ecosystems

    Directory of Open Access Journals (Sweden)

    Claudio ROSSI

    2009-02-01

    Full Text Available A simple model for upwelling irradiance has been developed. The model represents the relationship between Photosynthetically Active Radiation diffuse attenuation coefficients and Secchi disk depth described with a physical-mathematical expression. This physical mathematical expression allows the evaluation of the sub surface upwelling irradiance that was generated by the interaction between downwelling irradiance and the water column. The validation of the relation was performed using experimental data collected from five different aquatic ecosystems at different latitudes, solar elevations and irradiance levels. We found a good linear, positive correlation between the theoretical and measured upwelling irradiance (R2 = 0.96. The residues were well distributed, around the null value, according a Gaussian curve (R2 = 0.92. The results confirm the importance and the versatility of the Secchi disk measurements for aquatic optics.

  8. Dynamics of transient upwelling across the tropical tropopause

    Science.gov (United States)

    Randel, W. J.; Abalos, M.

    2013-12-01

    Tropical upwelling is a fundamental component of the stratospheric Brewer Dobson circulation (BDC), influencing temperatures, water vapor and chemical constituents throughout the global stratosphere. There is a substantial component of sub-seasonal variability in upwelling, with strong effects on temperatures and tracers in the tropical lower stratosphere. Upwelling diagnosed using momentum balance calculations from ERAinterim data demonstrate that transience is linked to the effects of extratropical wave forcing, with centers of action in the high latitude winter stratosphere and in the subtropical upper troposphere of both hemispheres. Zonal mean wind tendencies are an important part of communicating the remote wave forcing to the deep tropics. Dynamical patterns reflect clear differences in forcing the shallow vs. deep branches of the BDC; the shallow branch is most correlated with wave forcing in the subtropical upper troposphere, while the deep branch is mainly influenced by high latitude planetary waves.

  9. Influence of upwelling saline groundwater on iron and manganese cycling in the Rio Grande floodplain aquifer

    Energy Technology Data Exchange (ETDEWEB)

    Kirk, Matthew F. [Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131 (United States)], E-mail: matthew.f.kirk@gmail.com; Crossey, Laura J. [Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131 (United States); Takacs-Vesbach, Cristina [Department of Biology, University of New Mexico, Albuquerque, NM 87131 (United States); Newell, Dennis L. [Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131 (United States); Bowman, Robert S. [Department of Earth and Environmental Science, New Mexico Tech, Socorro, NM 87801 (United States)

    2009-03-15

    Salinity contributions from upwelling groundwater significantly degrade water quality in the Rio Grande, a major source of water for the southwestern USA. This study considers the influence of this upwelling water on the geochemistry and microbiology of the Rio Grande floodplain alluvial aquifer. The composition of surface water, groundwater, and floodplain sediment samples collected from three transects in the Socorro Basin was examined. Terminal-restriction fragment length polymorphism (T-RFLP) was also used to examine microbial biomass samples. The distribution of salinity in the floodplain groundwater largely reflects the configuration of local groundwater flow and mixing of two major water sources, deeply-sourced saline groundwater and river water. Microbial populations in the shallow aquifer consume O{sub 2} and NO{sub 3}{sup -} and serve to redistribute metal oxides from the saturated zone to locations of groundwater discharge at the surface and possibly near the water table. The upwelling saline groundwater affects floodplain microbial processes by transporting reduced metals and organic electron donors to the alluvial aquifer system. This enhances metal reduction in the saturated zone and ultimately metal oxidation at or near the surface. Geochemical modeling suggests that mixing of the saline groundwater with more dilute water in the floodplain creates conditions more favorable for metal oxidation to occur and thereby influences the distribution of metal oxides.

  10. Macro-Scale Patterns in Upwelling/Downwelling Activity at North American West Coast

    Science.gov (United States)

    Saldívar-Lucio, Romeo; Di Lorenzo, Emanuele; Nakamura, Miguel; Villalobos, Héctor; Lluch-Cota, Daniel; Del Monte-Luna, Pablo

    2016-01-01

    The seasonal and interannual variability of vertical transport (upwelling/downwelling) has been relatively well studied, mainly for the California Current System, including low-frequency changes and latitudinal heterogeneity. The aim of this work was to identify potentially predictable patterns in upwelling/downwelling activity along the North American west coast and discuss their plausible mechanisms. To this purpose we applied the min/max Autocorrelation Factor technique and time series analysis. We found that spatial co-variation of seawater vertical movements present three dominant low-frequency signals in the range of 33, 19 and 11 years, resembling periodicities of: atmospheric circulation, nodal moon tides and solar activity. Those periodicities might be related to the variability of vertical transport through their influence on dominant wind patterns, the position/intensity of pressure centers and the strength of atmospheric circulation cells (wind stress). The low-frequency signals identified in upwelling/downwelling are coherent with temporal patterns previously reported at the study region: sea surface temperature along the Pacific coast of North America, catch fluctuations of anchovy Engraulis mordax and sardine Sardinops sagax, the Pacific Decadal Oscillation, changes in abundance and distribution of salmon populations, and variations in the position and intensity of the Aleutian low. Since the vertical transport is an oceanographic process with strong biological relevance, the recognition of their spatio-temporal patterns might allow for some reasonable forecasting capacity, potentially useful for marine resources management of the region. PMID:27893826

  11. Why productive upwelling areas are often sources rather than sinks of CO2? – a comparative study on eddy upwellings in the South China Sea

    Directory of Open Access Journals (Sweden)

    N. Jiao

    2013-08-01

    Full Text Available Marine upwelling regions are known to be productive in carbon fixation and thus thought to be sinks of CO2, whereas many upwelling areas in the ocean are actually sources rather than sinks of CO2. To address this paradox, multiple biogeochemical parameters were investigated at two cyclonic-eddy-induced upwelling sites CE1 and CE2 in the western South China Sea. The results showed that upwelling can exert significant influences on biological activities in the euphotic zone and can either increase or decrease particulate organic carbon (POC export flux depending on upwelling conditions such as the magnitude, timing, and duration of nutrient input and consequent microbial activities. At CE2 the increase of phytoplankton biomass caused by the upwelled nutrients resulted in increase of POC export flux compared to non-eddy reference sites, while at CE1 the microbial respiration of organic carbon stimulated by the upwelled nutrients significantly contributed to the attenuation of POC export flux, aggravating outgassing of CO2. These results suggest that on top of upwelled dissolved inorganic carbon release, microbial activities stimulated by upwelled nutrients and phytoplankton labile organic carbon can play a critical role for a marine upwelling area to be a source rather than a sink of CO2. Meanwhile, we point out that even though an upwelling region is outgassing, carbon sequestration still takes place through the POC-based biological pump as well as the refractory dissolved organic carbon (RDOC-based microbial carbon pump.

  12. Global Weak Solutions of Initial Boundary Value Problem for Boltzmann-Poisson System with Absorbing Boundary%具吸收边界的Bolzmann-Poisson方程组初边值问题的整体弱解

    Institute of Scientific and Technical Information of China (English)

    崔国忠; 张志平; 江成顺

    2002-01-01

    This paper deals with the initial boundary value problem for the BoltzmannPoisson system, which arises in semiconductor physics, with absorbing boundary. The global existence of weak solutions is proved by using the stability of velocity averages and the compactness results on L1-theory under weaker conditons on initial boundary values.

  13. Thermal indices of upwelling effects on inner-shelf habitats

    Science.gov (United States)

    Tapia, Fabián J.; Navarrete, Sergio A.; Castillo, Manuel; Menge, Bruce A.; Castilla, Juan C.; Largier, John; Wieters, Evie A.; Broitman, Bernardo L.; Barth, John A.

    2009-12-01

    Spatial and temporal variability in regimes of coastal upwelling may have profound effects on the distribution and local dynamics of coastal marine populations and entire communities. Currently available mesoscale indices for upwelling intensity lack the resolution needed to characterize and compare inner-shelf upwelling regimes at small spatial scales (1-10’s km), which is often required to test relevant hypotheses in ecology, conservation, and management. We present local, quantitative indices of thermal variability, whose pattern across sites is largely driven by variation in coastal upwelling intensity at scales of few kilometers. Index calculations were based on daily records of insitu Sea Surface Temperature [SST], gathered at 30 sites along the Oregon-California coast, and at 25 sites along the coast of northern and central Chile. Several univariate metrics were calculated using daily series of temperature anomalies, and combined to produce a multivariate ordination of sites (Multivariate Upwelling Zone Index of Cooling, MUZIC) that allowed us to compare sites across regions. Multivariate indices calculated for 13 central Chile sites explained 52% and 50% of the among-site variance in corticated algal biomass and growth rate, respectively. Upwelling-induced variability at the scales documented here can have significant consequences on the ecology of coastal ecosystems. The basic data requirements (i.e. SST time series) and the simplicity of calculation make these indices a useful tool to apply at a large number of sites around the world, and to examine the generality of community- and population-level responses to physical forcing.

  14. PERIODIC BOUNDARY VALUE PROBLEM OF QUASILINEAR SYSTEM%拟线性系统周期边值问题

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The existence and uniqueness results about quasilinear periodic boundary value problems are established by using the global inverse function theorem and the result about the existence and uniquencess of periodic solutions for the periodic boundary value problem of nonhomogeneous linear periodic system.

  15. A Parameter Estimation Method for Nonlinear Systems Based on Improved Boundary Chicken Swarm Optimization

    Directory of Open Access Journals (Sweden)

    Shaolong Chen

    2016-01-01

    Full Text Available Parameter estimation is an important problem in nonlinear system modeling and control. Through constructing an appropriate fitness function, parameter estimation of system could be converted to a multidimensional parameter optimization problem. As a novel swarm intelligence algorithm, chicken swarm optimization (CSO has attracted much attention owing to its good global convergence and robustness. In this paper, a method based on improved boundary chicken swarm optimization (IBCSO is proposed for parameter estimation of nonlinear systems, demonstrated and tested by Lorenz system and a coupling motor system. Furthermore, we have analyzed the influence of time series on the estimation accuracy. Computer simulation results show it is feasible and with desirable performance for parameter estimation of nonlinear systems.

  16. Influence of boundary conditions and confinement on nonlocal effects in flows of wormlike micellar systems.

    Science.gov (United States)

    Masselon, Chloé; Colin, Annie; Olmsted, Peter D

    2010-02-01

    In this paper we report on the influence of different geometric and boundary constraints on nonlocal (spatially inhomogeneous) effects in wormlike micellar systems. In a previous paper, nonlocal effects were observable by measuring the local rheological flow curves of micelles flowing in a microchannel under different pressure drops, which appeared to differ from the flow curve measured using conventional rheometry. Here we show that both the confinement and the boundary conditions can influence those nonlocal effects. The role of the nature of the surface is analyzed in detail using a simple scalar model that incorporates inhomogeneities, which captures the flow behavior in both wide and confined geometries. This leads to an estimate for the nonlocal "diffusion" coefficient (i.e., the shear curvature viscosity) which corresponds to a characteristic length from 1 to 10 microm.

  17. Piecewise Smooth Dynamical Systems Theory: The Case of the Missing Boundary Equilibrium Bifurcations

    Science.gov (United States)

    Hogan, S. J.; Homer, M. E.; Jeffrey, M. R.; Szalai, R.

    2016-10-01

    We present two codimension-one bifurcations that occur when an equilibrium collides with a discontinuity in a piecewise smooth dynamical system. These simple cases appear to have escaped recent classifications. We present them here to highlight some of the powerful results from Filippov's book Differential Equations with Discontinuous Righthand Sides (Kluwer, 1988). Filippov classified the so-called boundary equilibrium collisions without providing their unfolding. We show the complete unfolding here, for the first time, in the particularly interesting case of a node changing its stability as it collides with a discontinuity. We provide a prototypical model that can be used to generate all codimension-one boundary equilibrium collisions, and summarize the elements of Filippov's work that are important in achieving a full classification.

  18. The Role of Shelf Break Upwelling Along the East Coast of the US in the Coastal Carbon Cycle: A Model's Tale

    Science.gov (United States)

    Siedlecki, S. A.; Mahadevan, A.; Archer, D.

    2008-12-01

    The coastal ocean is highly productive because it has several sources of nutrients: rivers, sediments and the open ocean. Although the East Coast of the United States is not an upwelling regime, its continental shelf is supplied by nutrients from the open ocean. Instead of traditional upwelling, a persistent front at the continental shelf break regulates the source of nutrients by interactions with the bottom boundary layer and the winds via a mechanism referred to as "shelf break upwelling." Shelf break upwelling also leads to ventilation of carbon dioxide and methane from coastal waters. A three-dimensional, nonhydrostatic, 2km resolution model with idealized bathymetry is used to simulate the shelf and shelf-break front circulations of an archetypical passive margin off the eastern coast of the United States. The model is adapted for the coastal setting from a model developed for open ocean fronts after Mahadevan et al, (1996a) and Mahadevan et al, (1996b) and is ground-truthed using data from the Mid- Atlantic Bight. We diagnose the pathways for nutrient supply and ventilation using a series of idealized tracers including nutrient, gas and bottom boundary layer tracers We find that the location of the foot of the front determines the source waters for the shelf break upwelling. In response to Southerly winds, the foot of the front moves onshore. Conversely, the foot moves offshore in response to Northerly winds. Targeted tracer results indicate that the source waters for upwelling depend on the direction of the wind: Southerly winds bring slope bottom water to the shelf, while Northerly winds bring up shelf bottom boundary layer water. The upwelling flux is sensitive to the duration as well as the magnitude of wind events. The physics and geochemistry of the bottom boundary layer and the shelf break front are not resolved in global-scale carbon cycle models, yet they appear to play a strong role in the coastal carbon cycle. Mahadevan, A., J. Oliger, and R

  19. A Reaction-diffusion System with Nonlinear Absorption Terms and Boundary Flux

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    This paper deals with a reaction-diffusion system with nonlinear absorption terms and boundary flux. As results of interactions among the six nonlinear terms in the system, some sufficient conditions on global existence and finite time blow-up of the solutions are described via all the six nonlinear exponents appearing in the six nonlinear terms. In addition, we also show the influence of the coefficients of the absorption terms as well as the geometry of the domain to the global existence and finite time blow-up of the solutions for some cases. At last, some numerical results are given.

  20. Characteristic finite difference method and application for moving boundary value problem of coupled system

    Institute of Scientific and Technical Information of China (English)

    YUAN Yi-rang; LI Chang-feng; YANG Cheng-shun; HAN Yu-ji

    2008-01-01

    The coupled system of multilayer dynamics of fluids in porous media is to describe the history of oil-gas transport and accumulation in basin evolution. It is of great value in rational evaluation of prospecting and exploiting oil-gas resources. The mathematical model can be described as a coupled system of nonlinear partial differential equations with moving boundary values. A kind of characteristic finite difference schemes is put forward, from which optimal order estimates in l2 norm are derived for the error in the approximate solutions. The research is important both theoretically and practically for the model analysis in the field, the model numerical method and software development.

  1. Many-body position operator in lattice fermionic systems with periodic boundary conditions

    Energy Technology Data Exchange (ETDEWEB)

    Hetenyi, Balazs [Institut fuer Theoretische Physik, Technische Universitaet Graz, Petersgasse 16, A-8010 Graz (Austria); Mathematisches Institut, Fakultaet fuer Mathematik, Informatik und Statistik, Ludwig Maximilians Universitaet, Theresienstrasse 39, Muenchen 80333 (Germany)], E-mail: hetenyi@itp.tugraz.at

    2009-10-16

    A total position operator X in the position representation is derived for lattice fermionic systems with periodic boundary conditions. The operator is shown to be Hermitian, the generator of translations in momentum space, and its time derivative is shown to correspond to the total current operator in a periodic system. The operator is such that its moments can be calculated up to any order. To demonstrate its utility finite size scaling is applied to the Brinkman-Rice transition as well as to metallic and insulating Gutzwiller wavefunctions. (fast track communication)

  2. Effects from magnetic boundary conditions in superconducting-magnetic proximity systems

    Directory of Open Access Journals (Sweden)

    Thomas E. Baker

    2016-05-01

    Full Text Available A superconductor-magnetic proximity system displays singlet-triplet pair correlations in the magnetization as a function of inhomogeneities of the magnetic profile. We discuss how the magnetic boundary conditions affects differently the curvature and winding number of rotating magnetizations in the three commonly used structures to generate long range triplet components: an exchange spring, a helical structure and a misaligned magnetic multilayer. We conclude that the choice of the system is dictated by the goal one wishes to achieve in designing a spintronic device but note that only the exchange spring presently offers an experimentally realizable magnetic profile that is tunable.

  3. Impact of climate change on surface wind regime over the Peru-Chile upwelling region

    Science.gov (United States)

    Goubanova, K.; Echevin, V.; Dewitte, B.; Garreaud, R.; Terray, P.; Vrac, M.

    2009-04-01

    The ocean region off the Chile-Peru coast is characterized by upwelling of cold, nutrient-rich waters, which drives an exceptionally high biological productivity. This upwelling is induced by the persistent southerly winds along the coast that exhibit a coastal jet structure at intraseasonal scales. Recent climate change studies based on the coupled atmosphere-ocean general circulation models (AOGCM) show a strengthening of the large-scale southerlies along the subtropical coast that could lead to an increase in coastal upwelling. However the coastal jet events which represent a considerable source of the synoptic variability of the alongshore winds are characterized by horizontal scale comparable to a AOGCM grid cell size, and cannot be therefore explicitly resolved by the AOGCMs. In order to provide a regional estimate of the winds as predicted by the coarse-resolution AOGCMs, a statistical downscaling method based on multiple linear regression is proposed. Large-scale wind at 10 m and sea level pressure are chosen as the predictor variables for regional 10 m wind. The validation is performed in two steps. First, QuikSCAT and ERS satellite products and NCEP reanalysis for the period 1992-2006 are used to build and validate the statistical model for the present climate. Second, the model is validated under a warmer climate: it is applied to large-scale predictors extracted from HadCM3 AOGCM simulations for the A2 and B2 SRES scenarios (2071-2100); the downscaled wind is then compared with outputs of the PRECIS regional climate model, forced at its boundaries by the same HadCM3 scenarios. To assess climate change impact on the along-shore wind, the statistical downscaling is applied to two contrasted SRES scenarios, namely the so-called preindustrial and CO2 quadrupling. The outputs of the IPSL-CM4 AOGCM are used as predictors. Evolution of the along-shore wind regime with a focus on the change of the coastal jet characteristics is discussed. For this particular

  4. Multifunction lidar system and its application for detecting aerosol and wind in boundary layer

    Science.gov (United States)

    Yang, Liquan; Qiu, Jinhuan; Zheng, Siping; Huang, Qirong

    1998-08-01

    A backscatter Nd-YAG lidar system has been constructed in our institute, which was designed to measure and image the four- dimensional structure the aerosol and to detect wind in lower atmosphere. It contains a Nd-YAG laser with maximum repetition rate of 15 pulses per second and a 20-cm telescope with maximum field of view of 3 mrad. A fast computer controlled angular scanning system provides can make the lidar to fire at the set position and time. Data logging system provides a logarithmic amplifier of 80 dB, 8 bit A/D conversion with range resolution of 7.5 m and high pixel resolution lidar images in a graphics computer. The system allows observations of inhomogeneities in natural aerosol in boundary layer showing the spatial distribution of aerosol scattering. A model to use triple angle azimuth scan method for measuring wind velocity is developed, which agrees well with the supposed wind in numerical experiment. The lidar system is been used in observations of aerosol and wind in boundary layer during February to July of 1998 and some results are presented.

  5. Parameter estimation for chaotic systems based on improved boundary chicken swarm optimization

    Science.gov (United States)

    Chen, Shaolong; Yan, Renhuan

    2016-10-01

    Estimating unknown parameters for chaotic system is a key problem in the field of chaos control and synchronization. Through constructing an appropriate fitness function, parameter estimation of chaotic system could be converted to a multidimensional parameter optimization problem. In this paper, a new method base on improved boundary chicken swarm optimization (IBCSO) algorithm is proposed for solving the problem of parameter estimation in chaotic system. However, to the best of our knowledge, there is no published research work on chicken swarm optimization for parameters estimation of chaotic system. Computer simulation based on Lorenz system and comparisons with chicken swarm optimization, particle swarm optimization, and genetic algorithm shows the effectiveness and feasibility of the proposed method.

  6. Geodynamic Evolution of the Nubia-Arabia-Somalia Plate Boundary System

    Science.gov (United States)

    Reilinger, R. E.; McClusky, S.; Vernant, P.; Ogubazghi, G.; Fisseha, S.; Arrajehi, A.; Bendick, R. O.; Sholan, J.

    2009-12-01

    We present a geodynamic scenario for the evolution of the Nubia (Nu)-Arabia (Ar)-Somalia (So) plate boundary system that is based on new geodetic constraints on the kinematics of active deformation, and published estimates of the timing of regional tectonic processes. This scenario supports two, long debated, principal hypotheses for plate dynamics, 1) plate motions are driven primarily by sinking of oceanic lithosphere at subduction zones, and 2) the lithosphere is strong in relation to plate boundaries and drag forces on the base of the lithosphere (and likely, resisting forces associate with continental collision). 1) During the Late Oligocene (~30 Ma), domal uplift of the Afar region due to the Afar hot spot caused regional extension and the initial development of the Afar Triple Junction (TJ) along pre-existing zones of weakness; 2) The So-Nu plate boundary, East African Rift (EAR), developed at a slow rate due to the absence of boundary-normal extensional stresses (i.e., no subduction “pulling” the So Plate), slow motion that continues to the present; 3) Larger extensional stresses across the Nu-Ar and Ar-So boundaries (Red Sea and Gulf of Aden) due to active subduction of the Neotethys ocean lithosphere beneath Eu caused more rapid extension of these early rifts, with full scale continental rifting beginning ~ 25-30 Ma; 4) Between 16 - 11 Ma full ocean rifting in the Gulf of Aden caused a decrease in the forces transmitted to the So and Nu plates, causing slowing of the Nu and So plates with respect to Eu and Ar, and (possibly) an additional component of N-S oriented extension across the Red Sea; 5) Around this time (~10 Ma), activity shifted from the Gulf of Suez to the DSF system in the N Red Sea, and the Danakil Block in the southern Red Sea began rotating with respect to Nu and Ar, both changes related to the change in Nu-Ar relative motion; and 6) The balance of forces on the plate system have remained roughly unchanged since ~10 Ma, as have

  7. An Examination of the Effect of Boundary Layer Ingestion on Turboelectric Distributed Propulsion Systems

    Science.gov (United States)

    Felder, James L.; Kim, Huyn Dae; Brown, Gerald V.; Chu, Julio

    2011-01-01

    A Turboelectric Distributed Propulsion (TeDP) system differs from other propulsion systems by the use of electrical power to transmit power from the turbine to the fan. Electrical power can be efficiently transmitted over longer distances and with complex topologies. Also the use of power inverters allows the generator and motors speeds to be independent of one another. This decoupling allows the aircraft designer to place the core engines and the fans in locations most advantageous for each. The result can be very different installation environments for the different devices. Thus the installation effects on this system can be quite different than conventional turbofans where the fan and core both see the same installed environments. This paper examines a propulsion system consisting of two superconducting generators, each driven by a turboshaft engine located so that their inlets ingest freestream air, superconducting electrical transmission lines, and an array of superconducting motor driven fan positioned across the upper/rear fuselage area of a hybrid wing body aircraft in a continuous nacelle that ingests all of the upper fuselage boundary layer. The effect of ingesting the boundary layer on the design of the system with a range of design pressure ratios is examined. Also the impact of ingesting the boundary layer on off-design performance is examined. The results show that when examining different design fan pressure ratios it is important to recalculate of the boundary layer mass-average Pt and MN up the height for each inlet height during convergence of the design point for each fan design pressure ratio examined. Correct estimation of off-design performance is dependent on the height of the column of air measured from the aircraft surface immediately prior to any external diffusion that will flow through the fan propulsors. The mass-averaged Pt and MN calculated for this column of air determine the Pt and MN seen by the propulsor inlet. Since the height

  8. Boundary Wall Shear Measurement with an Automated LDV-Based System

    Science.gov (United States)

    Modarress, Darius; Jeon, David; Svitek, Pavel; Gharib, Morteza

    2014-11-01

    Wall shear stress is one of the most important measurements in boundary layer flows. Getting wall shear measurements is generally quite difficult due to the need to measure very close to the wall, where poor optical access, particle seeding, and wall effects can bias the results. To simplify that process, a novel system was developed by Measurement Science Enterprise (MSE). The microPro consists of a 12 mm diameter miniLDV attached to a micro-translation stage assembled inside a sealed housing. The microPro automatically locates the wall and measures the mean flow speed profile from a point as close as 50 microns from the window. Accurate estimate of the mean wall shear is obtained from the calculation of the wall velocity gradient obtained from the velocity profile data. We measured wall shear stress on a boundary layer plate mounted in a water tunnel across a range of Reynolds numbers and compared the results against skin friction coefficient models. We also introduced bubbles into the boundary layer to measure the change in wall shear stress with changing void fraction. The measurements show good agreement with established data. This work is supported by the Office of Naval Research (Grant ONR-N00014-11-1-0031) and MSE.

  9. Arabian Sea upwelling - A comparison between coastal and open ocean regions

    Digital Repository Service at National Institute of Oceanography (India)

    Muraleedharan, P.M.; PrasannaKumar, S.

    Flux Studies (JGOFS) programme. Analysis of wind measurements indicated active upwelling along the southwest coast of India, which gradually propagates towards north. While the dominant long-shore component of the wind induces upwelling in the south...

  10. Coastal upwelling observed by multi-satellite sensors

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Coastal upwelling phenomenon along the China coast in the Yellow Sea during August 2007 is studied using ENVISAT Advanced Synthetic Aperture Radar (ASAR) data, NOAA Advanced AVHRR series Sea Surface Temperature (SST) data,and NASA QuikSCAT Scatterometer ocean surface wind data. A dark pattern in an ASAR image is interpreted as coastal upwelling. This is because the natural biogenic slicks associated with coastal upwelling damp the Bragg waves on the sea surface and thus make the surface smoother. Most of the incoming radar energy is reflected in the forward direction. As a result, the radar backscatter signal is very weak. Analyzing the concurrent AVHRR SST image, we find that the dark pattern in the ASAR image is indeed corresponding to the low SST area. The wind retrieval in the slicks dominant region is biased due to the low Normalised Radar Cross Section (NRCS) associated with the coastal upwelling. We applied a SST correction to the NRCS values to improve the accuracy of wind retrieval from ASAR data.

  11. Coastal upwelling observed by multi-satellite sensors

    Institute of Scientific and Technical Information of China (English)

    LI XiaoMing; LI XiaoFeng; HE MingXia

    2009-01-01

    Coastal upwelling phenomenon along the China coast in the Yellow Sea during August 2007 is studied using ENVISAT Advanced Synthetic Aperture Radar (ASAR) data, NOAA Advanced AVHRR series Sea Surface Temperature (SST) data, and NASA QuikSCAT Scatterometer ocean surface wind data. A dark pattern in an ASAR image is interpreted as coastal upwelling. This is because the natural biogenic slicks associated with coastal upwelling damp the Bragg waves on the sea surface and thus make the surface smoother. Most of the incoming radar energy is reflected in the forward direction. As a result, the radar backscatter signal is very weak. Analyzing the concurrent AVHRR SST Image, we find that the dark pattern in the ASAR image is indeed corresponding to the low SST area. The wind retrieval in the slicks dominant region is biased due to the low Normaliced Radar Cross Section (NRCS) associated with the coastal upwelling. We applied a SST correction to the NRCS values to improve the accuracy of wind retrieval from ASAR data.

  12. Upwelling Index, 42N 125W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  13. Upwelling Index, 48N 125W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  14. Upwelling Index, 24N 113W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  15. Upwelling Index, 21N 107W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  16. Upwelling Index, 60N 149W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  17. Upwelling Index, 60N 146W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  18. Upwelling Index, 45N 125W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  19. Upwelling Index, 33N 119W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  20. Upwelling Index, 27N 116W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  1. Upwelling Index, 57N 137W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  2. Upwelling Index, 30N 119W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  3. Upwelling Index, 54N 134W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  4. Upwelling Index, 51N 131W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  5. Upwelling Index, 39N 125W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  6. Upwelling Index, 36N 122W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  7. New microprofiling and micro sampling system for water saturated environmental boundary layers.

    Science.gov (United States)

    Fabricius, Anne-Lena; Duester, Lars; Ecker, Dennis; Ternes, Thomas A

    2014-07-15

    The spatial high resolution of a microprofiling system was combined with the multi element capability of ICP-MS to enable a better understanding of element distributions and related processes across environmental boundary layers. A combination of a microprofiling system with a new micro filtration probe head connected to a pump and a fraction collector (microprofiling and micro sampling system, missy) is presented. This enables for the first time a direct, dynamic, and high resolution automatic sampling of small water volumes (system as well as (iv) exemplary results of a sediment water interface are delivered. On the basis of this, potentials, possible sources of errors, and future applications of the new missy are discussed.

  8. Solution Transformations and Their Effects on the Systems with Open Boundary Conditions

    Institute of Scientific and Technical Information of China (English)

    JU Guo-Xing; ZHAO Xian-Lin

    2002-01-01

    The solution transformations and properties of the R-matrices for two-component systems uner these transformations are analyzed in details.Not all transformed R-matrices can be put into the Skalyanin's formalism.For those R-matrices with all required properties,the effects of solution transformations to the six- and eight-vertex systems with open boundary conditions are discussed.These effects can be one of the following types: The Hamiltonian is invariant or transposition-invariant or made in a similarity transformation,or its coupling coefficients are multiplied by an overall factor,or the spin of the system is rotated around the z axis or/and reflected with respect to some plane.In these cases,the transformed systems remain to be integrable.

  9. An instrument system for monitoring and sampling suspended sediment in the benthic boundary layer

    Science.gov (United States)

    Sternberg, R.W.; Johnson, R.V.; Cacchione, D.A.; Drake, D.E.

    1986-01-01

    An instrument system has been constructed that can monitor and sample suspended sediment distributions in the benthic boundary layer. It consists of miniature nephelometers and suspended sediment samplers placed within one meter of the seabed. The system is capable of continuously monitoring suspended sediment profiles at eight levels between 14 and 100 cm above the seabed and collecting suspended sediment samples at four levels (20, 50, 70 and 100 cm) at three times during a deployment period. The suspended sediment system is designed to fit onto the instrumented tripod GEOPROBE which contains four electromagnetic current meters, pressure sensor, bottom stereo camera, two temperature sensors, transmissometer, and a Savonius rotor current meter. Sensor operation, data recording, and sediment sampling events are synchronized. Thus detailed measurements of the near-bottom flow conditions are made concurrently with suspended sediment measurements. The combined system has been used in sediment transporting environments within San Francisco Bay, California, and Puget Sound, Washington. ?? 1986.

  10. Boundary of the area contributing flow to the Death Valley regional ground-water flow system, Nevada and California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This digital data set defines the boundary of the area contributing ground-water flow to the Death Valley regional ground-water flow-system (DVRFS) model domain. The...

  11. Existence and uniqueness for boundary-value problem with additional single point conditions of the Stokes-Bitsadze system

    Directory of Open Access Journals (Sweden)

    Muhammad Tahir

    2012-11-01

    Full Text Available This article shows the uniqueness of a solution to a Bitsadze system of equations, with a boundary-value problem that has four additional single point conditions. It also shows how to construct the solution.

  12. Boundary of the area contributing flow to the Death Valley regional ground-water flow system, Nevada and California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This digital data set defines the boundary of the area contributing ground-water flow to the Death Valley regional ground-water flow-system (DVRFS) model domain....

  13. Eddy Surface properties and propagation at Southern Hemisphere western boundary current systems

    Directory of Open Access Journals (Sweden)

    G. S. Pilo

    2015-02-01

    Full Text Available Oceanic eddies occur in all world oceans, but are more energetic when associated to western boundary currents (WBC systems. In these regions, eddies play an important role on mixing and energy exchange. Therefore, it is important to quantify and qualify eddies occurring within these systems. Previous studies performed eddy censuses in Southern Hemisphere WBC systems. However, important aspects of local eddy population are still unknown. Main questions to be answered relate to eddies' spatial distribution, propagation and lifetime within each system. Here, we use a global eddy dataset to qualify eddies based on their surface characteristics at the Agulhas Current (AC, the Brazil Current (BC and the East Australian Current (EAC Systems. We show that eddy propagation within each system is highly forced by the local mean flow and bathymetry. In the AC System, eddy polarity dictates its propagation distance. BC system eddies do not propagate beyond the Argentine Basin, and are advected by the local ocean circulation. EAC System eddies from both polarities cross south of Tasmania, but only anticyclonics reach the Great Australian Bight. Eddies in all systems and from both polarities presented a geographical segregation according to size. Large eddies occur along the Agulhas Retroflection, the Agulhas Return Current, the Brazil-Malvinas Confluence and the Coral Sea. Small eddies occur in the systems southernmost domains. Understanding eddies' propagation helps to establish monitoring programs, and to better understand how these features would affect local mixing.

  14. Nonlinear systems of differential inequalities and solvability of certain boundary value problems

    Directory of Open Access Journals (Sweden)

    Tvrdý Milan

    2001-01-01

    Full Text Available In the paper we present some new existence results for nonlinear second order generalized periodic boundary value problems of the form These results are based on the method of lower and upper functions defined as solutions of the system of differential inequalities associated with the problem and their relation to the Leray–Schauder topological degree of the corresponding operator. Our main goal consists in a fairly general definition of these functions as couples from . Some conditions ensuring their existence are indicated, as well.

  15. A computer program for generating two-dimensional boundary-fitted orthogonal curvilinear coordinate systems

    Energy Technology Data Exchange (ETDEWEB)

    Barbaro, M. [ENEA, Centro Ricerche `Ezio Clementel`, Bologna (Italy). Dipt. Innovazione

    1997-11-01

    A numerical method is described which generates an orthogonal curvilinear mesh, subject to the constraint that mesh lines are matched to all boundaries of a closed, simply connected two-dimensional region of arbitrary shape. The method is based on the solution, by an iterative finite-difference technique, of an elliptic differential system of equations for the Cartesian coordinates of the orthogonal grid nodes. The interior grid distribution is controlled by a technique which ensures that coordinate lines can be concentrated as desired. Examples of orthogonal meshes inscribed in various geometrical figures are included.

  16. On the Existence of Hydrodynamic Instability in Single Diffusive Bottom Heavy Systems with Permeable Boundaries

    Indian Academy of Sciences (India)

    A K Gupta; R G Shandil

    2011-11-01

    We utilize the reformulated equations of the classical theory, as derived by Banerjee et al.(J. Math. Anal. Appl. 175 (1993) 458), to establish mathematically, the existence of hydrodynamic instability in single diffusive bottom heavy systems, when considered in the more general framework of the boundary conditions of the type specified by Beavers and Joseph (J. Fluid Mech. 30 (1967) 197), in the parameter regime $T_0_2>1$, where $T_0$ and 2 being some properly chosen mean temperature and coefficient of specific heat (at constant volume) variation due to temperature variation respectively.

  17. Analisys of Hamiltonian Boundary Value Methods (HBVMs) for the numerical solution of polynomial Hamiltonian dynamical systems

    CERN Document Server

    Brugnano, Luigi; Trigiante, Donato

    2009-01-01

    One main issue, when numerically integrating autonomous Hamiltonian systems, is the long-term conservation of some of its invariants, among which the Hamiltonian function itself. For example, it is well known that standard (even symplectic) methods can only exactly preserve quadratic Hamiltonians. In this paper, a new family of methods, called Hamiltonian Boundary Value Methods (HBVMs), is introduced and analyzed. HBVMs are able to exactly preserve, in the discrete solution, Hamiltonian functions of polynomial type of arbitrarily high degree. These methods turn out to be symmetric, perfectly $A$-stable, and can have arbitrarily high order. A few numerical tests confirm the theoretical results.

  18. Weak solutions to the Landau-Lifshitz-Maxwell system with nonlinear Neumann boundary conditions arising from surface energies

    Directory of Open Access Journals (Sweden)

    Gilles Carbou

    2015-02-01

    Full Text Available We study the Landau-Lifshitz system associated with Maxwell equations in a bilayered ferromagnetic body when super-exchange and surface anisotropy interactions are present in the spacer in-between the layers. In the presence of these surface energies, the Neumann boundary condition becomes nonlinear. We prove, in three dimensions, the existence of global weak solutions to the Landau-Lifshitz-Maxwell system with nonlinear Neumann boundary conditions.

  19. Defining Hydrogeological Boundaries for Mountain Front Recharge (MFR) Predictions in Multi-Catchment Mountainous Systems

    Science.gov (United States)

    Neilson-Welch, L. A.; Allen, D. M.

    2010-12-01

    Cross-catchment groundwater flow in mountainous watersheds results from the development of local, intermediate, and regional groundwater flow pathways in multi-catchment systems. As such, hydrogeological analysis (e.g. water balance calculations and numerical modelling) to assess contributions of groundwater to mountain front recharge (MFR) must consider the choice of boundaries based on hydrological divides. Numerical 3-dimensional hydrogeological modelling was completed using FeFlow (DHI-WASY), for conceptual regional-scale multi-catchment systems; extending from a watershed boundary to a mountain front. The modelled systems were designed to represent major ridge and valley configurations observed in mountainous watersheds including: nested, adjacent, disconnected, non-parallel, and parallel catchments. Both homogeneous and heterogeneous hydraulic conductivity scenarios were simulated; with the heterogeneous scenario including a shallow zone of higher hydraulic conductivity bedrock overlying less permeable bedrock. The influence of cross-catchment flow in the development of groundwater flow pathways contributing to MFR was examined. The results provide a basis for identifying topographic scenarios where contributions to MFR may originate outside hydrological divides. This understanding will contribute to improving MFR predictions using both the numerical modelling approach and the water balance approach.

  20. On an upwelling front, propagation of upwelling and vertical velocity in the eastern Arabian sea during monsoon, 1987

    Digital Repository Service at National Institute of Oceanography (India)

    Antony, M.K.; Unnikrishnan, A.S.

    A coastal upwelling front parallel to the coast and identifiable upto a depth of 75 m was observed between 12.5 and 16 degrees N along the eastern Arabian Sea in September, 1987 from closely spaced digital BT data. With a north-south slope...

  1. THE ARTIFICIAL BOUNDARY CONDITIONS FOR NUMERICAL SIMULATIONS OF THE COMPLEX AMPLITUDE IN A COUPLED BAY-RIVER SYSTEM

    Institute of Scientific and Technical Information of China (English)

    Hou-de Han; Xin Wen

    2004-01-01

    We consider the numerical approximations of the complex amplitude in a coupled bay-river system in this work. One half-circumference is introduced as the artificial boundary in the open sea, and one segment is introduced as the artificial boundary in the river if the river is semi-infinite. On the artificial boundary a sequence of high-order artificial boundary conditions are proposed. Then the original problem is solved in a finite computational domain, which is equivalent to a variational problem. The numerical approximations for the original problem are obtained by solving the variational problem with the finite element method. The numerical examples show that the artificial boundary conditions given in this work are very effective.

  2. Did Cooling of Subthermocline Waters Help Establish Modern Upwelling Regions? Evidence rom ODP Site 716 in the Indian Ocean: Subthermocline δ18O Record Does Not Exceed General Cooling Trend of the Global Deep Ocean

    Science.gov (United States)

    Phelps, S.; Polissar, P. J.; deMenocal, P. B.

    2012-12-01

    The modern Indian Ocean exhibits a strong sea surface temperature gradient between the upwelling zone in the northwest Arabian Sea and the central warm pool. However, during the Pliocene, this temperature difference was essentially nonexistent. The shift in Indian Ocean sea surface temperature patterns parallels those in ocean basins worldwide—modern upwelling zones were dramatically warmer in the Pliocene and cooled around 2 million years ago, which had significant implications for regional precipitation patterns. Whether this cooling was due to stronger upwelling, colder subthermocline waters or other factors is not yet known. We analyzed the δ18O of benthic foraminifera from ODP site 716 in the Indian Ocean to test whether cooling of subthermocline waters contributed to cooling of the Arabian Sea upwelling region. Currently, bottom water at this 533 meter-deep site ventilates the thermocline and eventually upwells in the northwest Arabian Sea. We used the stable oxygen isotopic composition of the benthic foraminifera Uvigerina proboscidea and Cibicidoides spp. to infer changes in the temperature of bottom water at site 716. Our benthic record exhibits a ~1.5‰ secular shift over the past 4.5 million years, indicating cooling of bottom waters. The benthic δ18O trend at site 716 parallels the record from the deep ocean suggesting cooling of shallow waters was comparable to that observed in abyssal waters. The onset of cooling precedes the shift observed in upwelling regions by ~0.5 million years suggesting that colder subsurface waters were not the proximal cause of cooler upwelling regions. Cooler subsurface waters were likely a precondition that primed the system to amplify any changes in upwelling, but increased wind-driven upwelling at 2 million years initiated the establishment of the modern cold upwelling regions.

  3. Renyi entanglement entropies of descendant states in critical systems with boundaries: conformal field theory and spin chains

    Science.gov (United States)

    Taddia, Luca; Ortolani, Fabio; Pálmai, Tamás

    2016-09-01

    We discuss the Renyi entanglement entropies of descendant states in critical one-dimensional systems with boundaries, that map to boundary conformal field theories in the scaling limit. We unify the previous conformal-field-theory approaches to describe primary and descendant states in systems with both open and closed boundaries. We provide universal expressions for the first two descendants in the identity family. We apply our technique to critical systems belonging to different universality classes with non-trivial boundary conditions that preserve conformal invariance, and find excellent agreement with numerical results obtained for finite spin chains. We also demonstrate that entanglement entropies are a powerful tool to resolve degeneracy of higher excited states in critical lattice models.

  4. Prediction of acoustic radiation from axisymmetric surfaces with arbitrary boundary conditions using the boundary element method on a distributed computing system.

    Science.gov (United States)

    Wright, Louise; Robinson, Stephen P; Humphrey, Victor F

    2009-03-01

    This paper presents a computational technique using the boundary element method for prediction of radiated acoustic waves from axisymmetric surfaces with nonaxisymmetric boundary conditions. The aim is to predict the far-field behavior of underwater acoustic transducers based on their measured behavior in the near-field. The technique is valid for all wavenumbers and uses a volume integral method to calculate the singular integrals required by the boundary element formulation. The technique has been implemented on a distributed computing system to take advantage of its parallel nature, which has led to significant reductions in the time required to generate results. Measurement data generated by a pair of free-flooding underwater acoustic transducers encapsulated in a polyurethane polymer have been used to validate the technique against experiment. The dimensions of the outer surface of the transducers (including the polymer coating) were an outer diameter of 98 mm with an 18 mm wall thickness and a length of 92 mm. The transducers were mounted coaxially, giving an overall length of 185 mm. The cylinders had resonance frequencies at 13.9 and 27.5 kHz, and the data were gathered at these frequencies.

  5. Bio-optical characteristics of phytoplankton populations in the upwelling system off the coast of Chile Características (bio-ópticas de poblaciones de fitoplancton en el sistema de surgencia de la costa de Chile

    Directory of Open Access Journals (Sweden)

    VENETIA STUART

    2004-03-01

    Full Text Available Phytoplankton samples collected from two cruises off the coast of Chile were analysed for pigment composition and absorption characteristics. High pigment concentrations (up to 20 mg chl-a m-3 were found in the upwelled waters over the shelf break off the coast of Concepción during spring (October 1998, but relatively oligotrophic conditions were found further offshore. Similarly, stations further north (between Coquimbo and Iquique, sampled during the austral summer (February 1999, also showed low pigment concentrations, characterised by the presence of prymnesiophytes, and cyanobacteria including Prochlorococcus sp. The specific absorption coefficient of phytoplankton at 443 nm (a*ph(443 was much higher for the offshore population than the inshore population, which was dominated by large diatoms. These differences are attributed to changes in pigment packaging and pigment composition. The relative proportion of non-photosynthetic carotenoids to chl-a, together with the ratio of the peak height of the Gaussian bands in the blue and red regions of the spectrum, p(435/p(676, (an indicator of the importance of the packaging effect could account for up to 92 % of the total variation in a*ph(443. Blue/green absorption ratios were strongly related to the relative concentration of 19'-hexanoyloxyfucoxanthin and fucoxanthin. A reasonable agreement was found between in situ and satellite estimates of chl-a (SeaWiFS data despite the large variability in phytoplankton specific absorption coefficients, suggesting that the `global' absorption-to-chlorophyll relationships encompass the regional variations observed off the coast of Chile. Satellite chl-a was overestimated in oligotrophic water when compared to HPLC chl-a measurements, apparently because of the high specific absorption coefficients of phytoplankton in the offshore waters. On the other hand, ship and satellite data were in closer agreement when in situ fluorometric chl-a data was used. It is

  6. Can upwelling signals be detected in intertidal fishes of different trophic levels?

    Science.gov (United States)

    Pulgar, J; Poblete, E; Alvarez, M; Morales, J P; Aranda, B; Aldana, M; Pulgar, V M

    2013-11-01

    For intertidal fishes belonging to three species, the herbivore Scartichthys viridis (Blenniidae), the omnivore Girella laevifrons (Kyphosidae) and the carnivore Graus nigra (Kyphosidae), mass and body size relationships were higher in individuals from an upwelling zone compared with those from a non-upwelling zone. RNA:DNA were higher in the herbivores and omnivores from the upwelling zone. Higher biomass and RNA:DNA in the upwelling intertidal fishes may be a consequence of an increased exposure to higher nutrient availability, suggesting that increased physiological conditioning in vertebrates from upwelling areas can be detected and measured using intertidal fishes of different trophic levels.

  7. Coefficient of Variation Estimates for the Plate Boundary Fault System of California

    Science.gov (United States)

    Biasi, G. P.; Scharer, K. M.

    2015-12-01

    The number of high-quality paleoseismic records on major strike-slip faults of California has increased in recent years to the point that patterns in earthquake recurrence are emerging. The degree of predictability in time intervals between ground-rupturing earthquakes can be measured by the CoV (coefficient of variation). The CoV approximately normalizes for mean recurrence, and is thus useful to isolate the temporal variability of earthquake records. CoV estimates are themselves uncertain because input dates are actually probability distributions and because paleoseismic records are short and not necessarily representative samples from the underlying recurrence distribution. Radiocarbon dating uncertainty can be incorporated by sampling from event PDFs and compiling sample CoV estimates. Uncertainty due to the brevity of the site event record is larger, and neglect of it can lead to improbable estimates. Long records are now available on the San Andreas and San Jacinto faults in Southern California, and the San Andreas and Hayward faults in northern California. These faults accommodate most of the Pacific-North American relative plate motion in their respective regions. CoV estimates from sites with 8 or more events cluster around 0.63, but are as low as 0.4 for the southern Hayward fault. Sites with fewer events give similar estimates, though with lower resolution. The one prominent outlier, Burro Flats, with a CoV near 1.0, is in a region of severe fault complexity and rapid fault-normal compression. Quasi-periodic recurrence is emerging as a general property for these plate boundary faults. Some individual site records allow that, at low probabilities, recurrence could be random in time. When the ensemble is considered together, however, it is improbable that we would see the observed degree of agreement among boundary fault paleoseismic records; the more likely explanation is that quasi-periodic recurrence is a real property of the boundary fault system.

  8. Initial-boundary value problems for second order systems of partial differential equations

    CERN Document Server

    Kreiss, Heinz-Otto; Petersson, N Anders

    2010-01-01

    We develop a well-posedness theory for second order systems in bounded domains where boundary phenomena like glancing and surface waves play an important role. Attempts have previously been made to write a second order system consisting of n equations as a larger first order system. Unfortunately, the resulting first order system consists, in general, of more than 2n equations which leads to many complications, such as side conditions which must be satisfied by the solution of the larger first order system. Here we will use the theory of pseudo-differential operators combined with mode analysis. There are many desirable properties of this approach: 1) The reduction to first order systems of pseudo-differential equations poses no difficulty and always gives a system of 2n equations. 2) We can localize the problem, i.e., it is only necessary to study the Cauchy problem and halfplane problems with constant coefficients. 3) The class of problems we can treat is much larger than previous approaches based on "integ...

  9. On the Boundaries of Trust and Security in Computing and Communications Systems

    CERN Document Server

    Pathan, Al-Sakib Khan

    2012-01-01

    This article analyzes trust and security in computing and communications systems. While in human-life, trust usually has some kind of commonly understood meaning, in the realm of computing and communications systems, it could be interpreted differently in different environments and settings. On the other hand, security is about making sure that the participating entities are legitimate in a communication event or incident so that the core requirements of privacy, integrity, and authenticity are maintained. This notion is also true for our human life, even for example entering a house needs legitimacy of a person. Some boundary lines preserve the security; otherwise an unwanted access is called a 'security breach'. The intent of this article is to compare and discuss these two terms with our societal behavior and understanding amongst entities. To illustrate these issues especially in computing and communications world, some of the innovating and recent technologies are discussed which demand trust and securit...

  10. Numerical continuation methods for dynamical systems path following and boundary value problems

    CERN Document Server

    Krauskopf, Bernd; Galan-Vioque, Jorge

    2007-01-01

    Path following in combination with boundary value problem solvers has emerged as a continuing and strong influence in the development of dynamical systems theory and its application. It is widely acknowledged that the software package AUTO - developed by Eusebius J. Doedel about thirty years ago and further expanded and developed ever since - plays a central role in the brief history of numerical continuation. This book has been compiled on the occasion of Sebius Doedel''s 60th birthday. Bringing together for the first time a large amount of material in a single, accessible source, it is hoped that the book will become the natural entry point for researchers in diverse disciplines who wish to learn what numerical continuation techniques can achieve. The book opens with a foreword by Herbert B. Keller and lecture notes by Sebius Doedel himself that introduce the basic concepts of numerical bifurcation analysis. The other chapters by leading experts discuss continuation for various types of systems and objects ...

  11. Open Innovation and the Erosion of the Traditional Information Systems Project's Boundaries

    Science.gov (United States)

    Elbanna, Amany

    This paper examines the notion of open innovation and its implication on information systems management. It investigates a project of an enterprise resource planning system implementation in an international organization to unravel the resemblance with the open innovation model. The study shows that the conceptualization of ERP project as an open innovation could reveal the complex architecture of today's organization from which the ERP project cannot be isolated. It argues that the traditional boundaries around IS projects are dissolving and the relationship between what used to be outside and what used to be inside the project is increasingly blurred. The study calls for a different perspective of project management that goes beyond single and multiple project management to scan the open space of innovation and actively look for partners, competitors, and collaborators.

  12. THE UPWIND FINITE DIFFERENCE METHOD FOR MOVING BOUNDARY VALUE PROBLEM OF COUPLED SYSTEM

    Institute of Scientific and Technical Information of China (English)

    Yuan Yirang

    2011-01-01

    Coupled system of multilayer dynamics of fluids in porous media is to describe the history of oil-gas transport and accumulation in basin evolution. It is of great value in rational evaluation of prospecting and exploiting oil-gas resources. The mathematical model can be described as a coupled system of nonlinear partial differential equations with moving boundary values. The upwind finite difference schemes applicable to parallel arith- metic are put forward and two-dimensional and three-dimensional schemes are used to form a complete set. Some techniques, such as change of variables, calculus of variations, multiplicative commutation rule of difference operators, decomposition of high order dif- ference operators and prior estimates, are adopted. The estimates in 12 norm are derived to determine the error in the approximate solution. This method was already applied to the numerical simulation of migration-accumulation of oil resources.

  13. Computational Investigation of a Boundary-Layer Ingesting Propulsion System for the Common Research Model

    Science.gov (United States)

    Blumenthal, Brennan T.; Elmiligui, Alaa; Geiselhart, Karl A.; Campbell, Richard L.; Maughmer, Mark D.; Schmitz, Sven

    2016-01-01

    The present paper examines potential propulsive and aerodynamic benefits of integrating a Boundary-Layer Ingestion (BLI) propulsion system into a typical commercial aircraft using the Common Research Model (CRM) geometry and the NASA Tetrahedral Unstructured Software System (TetrUSS). The Numerical Propulsion System Simulation (NPSS) environment is used to generate engine conditions for CFD analysis. Improvements to the BLI geometry are made using the Constrained Direct Iterative Surface Curvature (CDISC) design method. Previous studies have shown reductions of up to 25% in terms of propulsive power required for cruise for other axisymmetric geometries using the BLI concept. An analysis of engine power requirements, drag, and lift coefficients using the baseline and BLI geometries coupled with the NPSS model are shown. Potential benefits of the BLI system relating to cruise propulsive power are quantified using a power balance method, and a comparison to the baseline case is made. Iterations of the BLI geometric design are shown and any improvements between subsequent BLI designs presented. Simulations are conducted for a cruise flight condition of Mach 0.85 at an altitude of 38,500 feet and an angle of attack of 2 deg for all geometries. A comparison between available wind tunnel data, previous computational results, and the original CRM model is presented for model verification purposes along with full results for BLI power savings. Results indicate a 14.4% reduction in engine power requirements at cruise for the BLI configuration over the baseline geometry. Minor shaping of the aft portion of the fuselage using CDISC has been shown to increase the benefit from Boundary-Layer Ingestion further, resulting in a 15.6% reduction in power requirements for cruise as well as a drag reduction of eighteen counts over the baseline geometry.

  14. Regenerated primary production dominates in a periodically upwelling shelf ecosystem, northeast New Zealand

    Science.gov (United States)

    Bury, S. J.; Zeldis, J. R.; Nodder, S. D.; Gall, M.

    2012-01-01

    We present the first field measured primary production values for an intermittently upwelling shelf ecosystem in the Hauraki Gulf, northeast New Zealand. Phytoplankton uptake rates of 13C and 15N were used to determine the relative importance of new (15NO3- ) versus regenerated nutrients (15NH4+ and 15N-urea) to productivity, and to test the hypothesis that the upwelling system supports high export of organic material, acting as a net sink for CO2. From early spring to early summer (1996-1997), deep NO3--rich waters upwelled onto the shelf and into the inner gulf, producing a short-lived low-level predominantly NO3--fuelled bloom (surface chlorophyll-a (chl-a) >1.0 mg m-3) in early spring. From late spring onwards, mixed layer NO3- concentrations were depleted to often lower levels than NH4+ and urea (∼0.1 mmol m-3), with mid-water chl-a maxima associated with the top of the nitracline fuelled predominantly by regenerated nutrients. By late summer, upwelling had ceased, with intrusions of low-nutrient subtropical oceanic surface water producing oligotrophic conditions. NH4+ and urea uptake nearly always exceeded NO3- uptake throughout the euphotic zone, even within the nitracline, with relative preference index (RPI) estimates giving RPIUrea>RPINH>RPINO, and low uptake f ratios (generally fphysiological preference of phytoplankton for reduced forms of nitrogen. Despite periods of upwelling producing relatively high levels of integrated NO3- (typically 25-150 mmol NO3- m-2) across the shelf from early spring to early summer, the highest integrated total production (1266 mg C m-2 d-1) and specific uptake rates of C/chl-a were obtained in late summer. In the inner gulf and on the mid-shelf, these higher late summer production rates coincided with low integrated chl-a biomass and NO3- inventories. There was no correlation of chl-a with C uptake in either surface waters (r2=0.0115), or in the euphotic zone (r2=0.0232) for the compiled data set, raising potential

  15. Distributed Plate Boundary Deformation Across the San Andreas Fault System, Central California

    Science.gov (United States)

    Dyson, M.; Titus, S. J.; Demets, C.; Tikoff, B.

    2007-12-01

    Plate boundaries are now recognized as broad zones of complex deformation as opposed to narrow zones with discrete offsets. When assessing how plate boundary deformation is accommodated, both spatially and temporally, it is therefore crucial to understand the relative contribution of the discrete and distributed components of deformation. The creeping segment of the San Andreas fault is an ideal location to study the distribution of plate boundary deformation for several reasons. First, the geometry of the fault system in central California is relatively simple. Plate motion is dominated by slip along the relatively linear strike-slip San Andreas fault, but also includes lesser slip along the adjacent and parallel Hosgri-San Gregorio and Rinconada faults, as well as within the borderlands between the three fault strands. Second, the aseismic character of the San Andreas fault in this region allows for the application of modern geodetic techniques to assess creep rates along the fault and across the region. Third, geologic structures within the borderlands are relatively well-preserved allowing comparison between modern and ancient rates and styles of deformation. Continuous GPS stations, alignment arrays surveys, and other geodetic methods demonstrate that approximately 5 mm/yr of distributed slip is accumulated (on top of the fault slip rate) across a 70-100 km wide region centered on the San Andreas fault. New campaign GPS data also suggest 2-5 mm/yr of deformation in the borderlands. These rates depend on the magnitude of the coseismic and postseismic corrections that must be made to our GPS time series to compensate for the 2003 San Simeon and 2004 Parkfield earthquakes, which rupture faults outside, but near the edges of our GPS network. The off-fault deformation pattern can be compared to the style of permanent deformation recorded in the geologic record. Fold and thrust belts in the borderlands are better developed in the Tertiary sedimentary rocks west of

  16. The role of Equatorial Undercurrent in sustaining the Eastern Indian Ocean upwelling

    Science.gov (United States)

    Chen, Gengxin; Han, Weiqing; Shu, Yeqiang; Li, Yuanlong; Wang, Dongxiao; Xie, Qiang

    2016-06-01

    By combining volume transport and salinity analysis from 1958 to 2014, this paper investigates how the transient Equatorial Undercurrent (EUC) sustains the summer-fall equatorial eastern Indian Ocean (EIO) upwelling. On seasonal time scales, the EIO upwelling is mainly supplied by the salty water from the western basin through a buffering process: The winter-spring EUC carries the salty water from the western basin eastward, induces downwelling in the EIO, and pushes portion of the salty water below the central thermocline, which subsequently upwells to the central thermocline during summer-fall and sustains the EIO upwelling. On interannual time scales, enhanced upwelling occurs during positive Indian Ocean Dipole (+IOD) years. The strong summer-fall EUC associated with the +IOD supplies water for the intensified upwelling. This research provides new knowledge for basin-scale mass and property exchanges associated with the EIO upwelling, contributing to our understanding of three-dimensional ocean circulation and climate variability.

  17. Binary mask optimization for forward lithography based on the boundary layer model in coherent systems.

    Science.gov (United States)

    Ma, Xu; Arce, Gonzalo R

    2009-07-01

    Recently, a set of generalized gradient-based optical proximity correction (OPC) optimization methods have been developed to solve for the forward and inverse lithography problems under the thin-mask assumption, where the mask is considered a thin 2D object. However, as the critical dimension printed on the wafer shrinks into the subwavelength regime, thick-mask effects become prevalent, and thus these effects must be taken into account in OPC optimization methods. OPC methods derived under the thin-mask assumption have inherent limitations and perform poorly in the subwavelength regime. This paper focuses on developing model-based forward binary mask optimization methods that account for the thick-mask effects of coherent imaging systems. The boundary layer (BL) model is exploited to simplify and characterize the thick-mask effects, leading to a model-based OPC method. The BL model is simpler than other thick-mask models, treating the near field of the mask as the superposition of the interior transmission areas and the boundary layers. The advantages and limitations of the proposed algorithm are discussed, and several illustrative simulations are presented.

  18. Binary mask optimization for forward lithography based on boundary layer model in coherent systems

    Science.gov (United States)

    Ma, Xu; Arce, Gonzalo R.

    2010-04-01

    Recently, a set of generalized gradient-based optical proximity correction (OPC) optimization methods have been developed to solve for the forward and inverse lithography problem under the thin-mask assumption, where the mask is considered a thin 2-D object. However, as the critical dimension printed on the wafer shrinks into the subwavelength regime, thick-mask effects become prevalent and thus these effects must be taken into account in OPC optimization methods. OPC methods derived under the thin-mask assumption have inherent limitations and perform poorly in the subwavelength scenario. This paper focuses on developing model-based forward binary mask optimization methods which account for the thick-mask effects of coherent imaging systems. The boundary layer (BL) model is exploited to simplify and characterize the thick-mask effects, leading to a computationally efficient OPC method. The BL model is simpler than other thick-mask models, treating the near field of the mask as the superposition of the interior transmission areas and the boundary layers. The advantages and limitations of the proposed algorithm are discussed and several illustrative simulations are presented.

  19. Tracer dynamics in a single-file system with absorbing boundary.

    Science.gov (United States)

    Ryabov, Artem; Chvosta, Petr

    2014-02-01

    The paper addresses the single-file diffusion in the presence of an absorbing boundary. The emphasis is on an interplay between the hard-core interparticle interaction and the absorption process. The resulting dynamics exhibits several qualitatively new features. First, starting with the exact probability density function for a given particle (a tracer), we study the long-time asymptotics of its moments. Both the mean position and the mean-square displacement are controlled by dynamical exponents which depend on the initial order of the particle in the file. Second, conditioning on nonabsorption, we study the distribution of long-living particles. In the conditioned framework, the dynamical exponents are the same for all particles, however, a given particle possesses an effective diffusion coefficient which depends on its initial order. After performing the thermodynamic limit, the conditioned dynamics of the tracer is subdiffusive, the generalized diffusion coefficient D(1/2) being different from that reported for the system without absorbing boundary.

  20. Multiple positive solutions to nonlinear boundary value problems of a system for fractional differential equations.

    Science.gov (United States)

    Zhai, Chengbo; Hao, Mengru

    2014-01-01

    By using Krasnoselskii's fixed point theorem, we study the existence of at least one or two positive solutions to a system of fractional boundary value problems given by -D(0+)(ν1)y1(t) = λ1a1(t)f(y1(t), y2(t)), - D(0+)(ν2)y2(t) = λ2a2(t)g(y1(t), y2(t)), where D(0+)(ν) is the standard Riemann-Liouville fractional derivative, ν1, ν2 ∈ (n - 1, n] for n > 3 and n ∈ N, subject to the boundary conditions y1((i))(0) = 0 = y ((i))(0), for 0 ≤ i ≤ n - 2, and [D(0+)(α)y1(t)] t=1 = 0 = [D(0+ (α)y2(t)] t=1, for 1 ≤ α ≤ n - 2, or y1((i))(0) = 0 = y ((i))(0), for 0 ≤ i ≤ n - 2, and [D(0+)(α)y1(t)] t=1 = ϕ1(y1), [D(0+)(α)y2(t)] t=1 = ϕ2(y2), for 1 ≤ α ≤ n - 2, ϕ1, ϕ2 ∈ C([0,1], R). Our results are new and complement previously known results. As an application, we also give an example to demonstrate our result.

  1. Stability boundaries analysis of non-autonomous systems with resonant solutions based on subharmonic Melnikov functions, Proceedings of the 2004 American Control Conference

    OpenAIRE

    Susuki, Yoshihiko; Hikihara Takashi

    2004-01-01

    This paper addresses stability boundaries in non-autonomous systems. An analytical criterion for stability boundaries in one degree of freedom (time-periodic) perturbed Hamiltonian systems was recently proposed. The criterion evaluates basin boundaries of non-resonant solutions. This paper discusses the stability boundaries with respect to the resonant solutions based on the above result and subharmonic Melnikov functions. At first one degree of freedom perturbed (time-independent) Hamiltonia...

  2. Laboratory Modelling of the Dynamics of Coastal Upwelling

    Science.gov (United States)

    1991-02-28

    such regions. standing features. as described above. should be absent. instead a uniform upwelled front and associated traveling frontal-eddies...Argote. E.M.L., Amador. B.A. and Barton. E.D.. 1978. Mediciones de vientos. corrientes e hidrografia frente a Punto Colonet. B.C. En Junio 1976. CICESE...the distance of the downstream standing waves bre from the cape were considerably smaller. by As in our previous experiment, travelling baroclinic waves

  3. Aragonite saturation state dynamics in a coastal upwelling zone

    Science.gov (United States)

    Harris, Katherine E.; Degrandpre, Michael D.; Hales, Burke

    2013-06-01

    upwelling zones may be at enhanced risk from ocean acidification as upwelling brings low aragonite saturation state (ΩAr) waters to the surface that are further suppressed by anthropogenic CO2. ΩAr was calculated with pH, pCO2, and salinity-derived alkalinity time series data from autonomous pH and pCO2 instruments moored on the Oregon shelf and shelf break during different seasons from 2007 to 2011. Surface ΩAr values ranged between 0.66 ± 0.04 and 3.9 ± 0.04 compared to an estimated pre-industrial range of 1.0 ± 0.1 to 4.7 ± 0.1. Upwelling of high-CO2 water and subsequent removal of CO2 by phytoplankton imparts a dynamic range to ΩAr from ~1.0 to ~4.0 between spring and autumn. Freshwater input also suppresses saturation states during the spring. Winter ΩAr is less variable than during other seasons and is controlled primarily by mixing of the water column.

  4. Acceleration of multiple solution of a boundary value problem involving a linear algebraic system

    Science.gov (United States)

    Gazizov, Talgat R.; Kuksenko, Sergey P.; Surovtsev, Roman S.

    2016-06-01

    Multiple solution of a boundary value problem that involves a linear algebraic system is considered. New approach to acceleration of the solution is proposed. The approach uses the structure of the linear system matrix. Particularly, location of entries in the right columns and low rows of the matrix, which undergo variation due to the computing in the range of parameters, is used to apply block LU decomposition. Application of the approach is considered on the example of multiple computing of the capacitance matrix by method of moments used in numerical electromagnetics. Expressions for analytic estimation of the acceleration are presented. Results of the numerical experiments for solution of 100 linear systems with matrix orders of 1000, 2000, 3000 and different relations of variated and constant entries of the matrix show that block LU decomposition can be effective for multiple solution of linear systems. The speed up compared to pointwise LU factorization increases (up to 15) for larger number and order of considered systems with lower number of variated entries.

  5. Nitrogen transfers and air-sea N2O fluxes in the upwelling off Namibia within the oxygen minimum zone: a 3-D model approach

    Directory of Open Access Journals (Sweden)

    A. Paulmier

    2011-04-01

    Full Text Available As regions of high primary production and being often associated to Oxygen Minimum Zones (OMZs, Eastern Boundary Upwelling Systems (EBUS represent key regions for the oceanic nitrogen (N cycle. Indeed, by exporting the Organic Matter (OM and nutrients produced in the coastal region to the open ocean, EBUS can play an important role in sustaining primary production in subtropical gyres. Losses of fixed inorganic N, through denitrification and anammox processes and through nitrous oxide (N2O emissions to the atmosphere, take place in oxygen depleted environments such as EBUS, and alleviate the role of these regions as a source of N. In the present study, we developed a 3-D coupled physical/biogeochemical (ROMS/BioBUS model for investigating the full N budget in the Namibian sub-system of the Benguela Upwelling System (BUS. The different state variables of a climatological experiment have been compared to different data sets (satellite and in situ observations and show that the model is able to represent this biogeochemical oceanic region. The N transfer is investigated in the Namibian upwelling system using this coupled model, especially in the Walvis Bay area between 22° S and 24° S where the OMZ is well developed (O2 2 l−1. The upwelling process advects 24.2 × 1010 mol N yr−1 of nitrate enriched waters over the first 100 m over the slope and over the continental shelf. The meridional advection by the alongshore Benguela current brings also nutrient-rich waters with 21.1 × 1010 mol N yr−1. 10.5 × 1010 mol N yr−1 of OM are exported outside of the continental shelf (between 0 and 100-m depth. 32.4% and 18.1% of this OM are exported by advection in the form of Dissolved and Particulate Organic Matters (DOM and POM, respectively, however vertical sinking of POM represents the main contributor (49.5% to OM export outside of the first 100-m depth of the water column on the continental shelf. The continental slope also represents a net N

  6. Seasonal variability of phytoplankton fluorescence in relation to the Straits of Messina (Sicily) tidal upwelling

    Science.gov (United States)

    Azzaro, F.; Decembrini, F.; Raffa, F.; Crisafi, E.

    2007-10-01

    In the Straits of Messina, large gradients of tidal displacements, as well as the topographic constrictions, determine the upwelling of deeper waters in the surface layer. This work describes the seasonal variability in the surface distribution of phytoplankton biomass depending on the upwelling phenomena. Temperature, salinity, nitrates and phytoplankton fluorescence were measured in 1994 and 1995 by continuous underway surface real-time measurements onboard dedicated research boats. Each survey was performed following the dynamic phases of flooding and ebbing tides. Tidal currents are essentially southward during high tide and northward during low tide. During the low water slack tide, large spatial gradients of physical-chemical and biological parameters were found, while at the high water slack tide, a diffused phytoplankton fluorescence was observed only in autumn due to a seasonal thermocline. Salinity, nitrate and chlorophyll-a fluorescence data revealed a significant positive intercorrelation, whereas they were inversely correlated with temperature. Generally, the upwelling distribution was limited to narrow zones during winter, while in summer it was found in the middle of the Straits and in the southern zones. During spring in the southern zone of the Straits, the maximum chlorophyll-a fluorescence was detected (May 1995, 0.32 μg-Chla l-1); in summer, when back and forth tidal movements between the Tyrrhenian and the Ionian seas intensify, decreased values were observed throughout the study area. The data set obtained through continuous and repeatable samplings has allowed the study of different time-space scales in the Straits of Messina, a very strong and dynamic environment. The Straits system could be compared to an "intermittent pump" which, during the different seasons, initially enriches itself and subsequently provides nutrients to the surrounding basins.

  7. Seasonal variability of phytoplankton fluorescence in relation to the Straits of Messina (Sicily tidal upwelling

    Directory of Open Access Journals (Sweden)

    F. Azzaro

    2007-05-01

    Full Text Available In the Straits of Messina the large gradients of tidal displacements as well as the topographic constrictions determine the upwelling of deeper waters in the surface layer. This work describes the seasonal variability of surface distribution of phytoplankton biomass depending on upwelling phenomena. Temperature, salinity, nitrates and phytoplankton fluorescence were measured in 1994 and 1995 by continuous underway surface real-time measurements on board dedicated research boats. Each survey was performed following the dynamic phases of flooding and ebbing tides. Tidal currents are essentially southward during the high tide and northward during the low tide.

    During the low water slack, large spatial gradients of physical-chemical and biological parameters were mainly found, while in the high water slack a diffused phytoplankton fluorescence was observed only in autumn, in coincidence of a seasonal thermocline. Salinity, nitrate and chlorophyll-a fluorescence data revealed a significant positive intercorrelation, whereas they are inversely correlated with temperature. Generally, during winter, the upwelling distribution was limited to narrow zones, while in summer it involved the middle of the Straits and southern zones. During spring in the southern zone of the Straits, maximum of chlorophyll-a fluorescence was detected (May 1995, 0.32 µg-Chla l-1; in summer, when back and forth tidal movements become intense between the Tyrrhenian and the Ionian seas, values was everywhere lower.

    The data set from continuous and repeatable acquisition has allowed the study of different time-space scales in the Straits of Messina, a very strong dynamic environment.

    The Straits system can be compared to an "intermittent pump" which, during the different seasons, before enriched itself and then it provides nutrients to the surrounding basins.

  8. Research on a Small Signal Stability Region Boundary Model of the Interconnected Power System with Large-Scale Wind Power

    Directory of Open Access Journals (Sweden)

    Wenying Liu

    2015-03-01

    Full Text Available For the interconnected power system with large-scale wind power, the problem of the small signal stability has become the bottleneck of restricting the sending-out of wind power as well as the security and stability of the whole power system. Around this issue, this paper establishes a small signal stability region boundary model of the interconnected power system with large-scale wind power based on catastrophe theory, providing a new method for analyzing the small signal stability. Firstly, we analyzed the typical characteristics and the mathematic model of the interconnected power system with wind power and pointed out that conventional methods can’t directly identify the topological properties of small signal stability region boundaries. For this problem, adopting catastrophe theory, we established a small signal stability region boundary model of the interconnected power system with large-scale wind power in two-dimensional power injection space and extended it to multiple dimensions to obtain the boundary model in multidimensional power injection space. Thirdly, we analyzed qualitatively the topological property’s changes of the small signal stability region boundary caused by large-scale wind power integration. Finally, we built simulation models by DIgSILENT/PowerFactory software and the final simulation results verified the correctness and effectiveness of the proposed model.

  9. ADFE METHOD WITH HIGH ACCURACY FOR NONLINEAR PARABOLIC INTEGRO-DIFFERENTIAL SYSTEM WITH NONLINEAR BOUNDARY CONDITIONS

    Institute of Scientific and Technical Information of China (English)

    崔霞

    2002-01-01

    Alternating direction finite element (ADFE) scheme for d-dimensional nonlinear system of parabolic integro-differential equations is studied. By using a local approximation based on patches of finite elements to treat the capacity term qi(u), decomposition of the coefficient matrix is realized; by using alternating direction, the multi-dimensional problem is reduced to a family of single space variable problems, calculation work is simplified; by using finite element method, high accuracy for space variant is kept; by using inductive hypothesis reasoning, the difficulty coming from the nonlinearity of the coefficients and boundary conditions is treated; by introducing Ritz-Volterra projection, the difficulty coming from the memory term is solved. Finally, by using various techniques for priori estimate for differential equations, the unique resolvability and convergence properties for both FE and ADFE schemes are rigorously demonstrated, and optimal H1 and L2norm space estimates and O((△t)2) estimate for time variant are obtained.

  10. Family of singular solutions in a SUSY bulk-boundary system

    Science.gov (United States)

    Ichinose, Shoichi; Murayama, Akihiro

    2004-08-01

    A set of classical solutions of a singular type is found in a 5D SUSY bulk-boundary system. The "parallel" configuration, where the whole components of fields or branes are parallel in the iso-space, naturally appears. It has three free parameters related to the scale freedom in the choice of the brane-matter sources and the "free" wave property of the extra component of the bulk-vector field. The solutions describe brane, anti-brane and brane-anti-brane configurations depending on the parameter choice. Some solutions describe the localization behaviour even after the non-compact limit of the extra space. Stableness is assured. Their meaning in the brane world physics is examined in relation to the stableness, localization, non-singular (kink) solution and the bulk Higgs mechanism.

  11. Family of Singular Solutions in A SUSY Bulk-Boundary System

    CERN Document Server

    Ichinose, S; Ichinose, Shoichi; Murayama, Akihiro

    2004-01-01

    A set of classical solutions of a singular type is found in a 5D SUSY bulk-boundary system. The "parallel" configuration, where the whole components of fields or branes are parallel in the iso-space, naturally appears. It has three {\\it free} parameters related to the {\\it scale freedom} in the choice of the brane-matter sources and the {\\it "free" wave} property of the extra component of the bulk-vector field. The solutions describe brane, anti-brane and brane-anti-brane configurations depending on the parameter choice. Some solutions describe the localization behaviour even after the non-compact limit of the extra space. Stableness is assured. Their meaning in the brane world physics is examined in relation to the stableness, localization, non-singular (kink) solution and the bulk Higgs mechanism.

  12. Existence of solutions to second-order nonlinear coupled systems with nonlinear coupled boundary conditions

    Directory of Open Access Journals (Sweden)

    Imran Talib

    2015-12-01

    Full Text Available In this article, study the existence of solutions for the second-order nonlinear coupled system of ordinary differential equations $$\\displaylines{ u''(t=f(t,v(t,\\quad t\\in [0,1],\\cr v''(t=g(t,u(t,\\quad t\\in [0,1], }$$ with nonlinear coupled boundary conditions $$\\displaylines{ \\phi(u(0,v(0,u(1,v(1,u'(0,v'(0=(0,0, \\cr \\psi(u(0,v(0,u(1,v(1,u'(1,v'(1=(0,0, }$$ where $f,g:[0,1]\\times \\mathbb{R}\\to \\mathbb{R}$ and $\\phi,\\psi:\\mathbb{R}^6\\to \\mathbb{R}^2$ are continuous functions. Our main tools are coupled lower and upper solutions, Arzela-Ascoli theorem, and Schauder's fixed point theorem.

  13. Modeling quorum sensing trade-offs between bacterial cell density and system extension from open boundaries

    Science.gov (United States)

    Marenda, Mattia; Zanardo, Marina; Trovato, Antonio; Seno, Flavio; Squartini, Andrea

    2016-12-01

    Bacterial communities undergo collective behavioural switches upon producing and sensing diffusible signal molecules; a mechanism referred to as Quorum Sensing (QS). Exemplarily, biofilm organic matrices are built concertedly by bacteria in several environments. QS scope in bacterial ecology has been debated for over 20 years. Different perspectives counterpose the role of density reporter for populations to that of local environment diffusivity probe for individual cells. Here we devise a model system where tubes of different heights contain matrix-embedded producers and sensors. These tubes allow non-limiting signal diffusion from one open end, thereby showing that population spatial extension away from an open boundary can be a main critical factor in QS. Experimental data, successfully recapitulated by a comprehensive mathematical model, demonstrate how tube height can overtake the role of producer density in triggering sensor activation. The biotic degradation of the signal is found to play a major role and to be species-specific and entirely feedback-independent.

  14. Family of singular solutions in a SUSY bulk-boundary system

    Energy Technology Data Exchange (ETDEWEB)

    Ichinose, Shoichi; Murayama, Akihiro

    2004-08-19

    A set of classical solutions of a singular type is found in a 5D SUSY bulk-boundary system. The 'parallel' configuration, where the whole components of fields or branes are parallel in the iso-space, naturally appears. It has three free parameters related to the scale freedom in the choice of the brane-matter sources and the 'free' wave property of the extra component of the bulk-vector field. The solutions describe brane, anti-brane and brane-anti-brane configurations depending on the parameter choice. Some solutions describe the localization behaviour even after the non-compact limit of the extra space. Stableness is assured. Their meaning in the brane world physics is examined in relation to the stableness, localization, non-singular (kink) solution and the bulk Higgs mechanism.

  15. Changes in optical characteristics of surface microlayers hint to photochemically and microbially mediated DOM turnover in the upwelling region off the coast of Peru

    OpenAIRE

    Galgani, Luisa; Engel, Anja

    2016-01-01

    The coastal upwelling system off the coast of Peru is characterized by high biological activity and a pronounced subsurface oxygen minimum zone, as well as associated emissions of atmospheric trace gases such as N2O, CH4 and CO2. From 3 to 23 December 2012, R/V Meteor (M91) cruise took place in the Peruvian upwelling system between 4.59 and 15.4° S, and 82.0 to 77.5° W. During M91 we investigated the composition of the sea-surface microlayer (SML), the oceanic uppermos...

  16. On the Fluctuation Relation for Nosé-Hoover Boundary Thermostated Systems

    Science.gov (United States)

    Mejía-Monasterio, Carlos; Rondoni, Lamberto

    2008-11-01

    We discuss the transient and steady state fluctuation relation for a mechanical system in contact with two deterministic thermostats at different temperatures. The system is a modified Lorentz gas in which the fixed scatterers exchange energy with the gas of particles, and the thermostats are modelled by two Nosé-Hoover thermostats applied at the boundaries of the system. The transient fluctuation relation, which holds only for a precise choice of the initial ensemble, is verified at all times, as expected. Times longer than the mesoscopic scale, needed for local equilibrium to be settled, are required if a different initial ensemble is considered. This shows how the transient fluctuation relation asymptotically leads to the steady state relation when, as explicitly checked in our systems, the condition found in (D.J. Searles, et al., J. Stat. Phys. 128:1337, 2007), for the validity of the steady state fluctuation relation, is verified. For the steady state fluctuations of the phase space contraction rate Λ and of the dissipation function Ω, a similar relaxation regime at shorter averaging times is found. The quantity Ω satisfies with good accuracy the fluctuation relation for times larger than the mesoscopic time scale; the quantity Λ appears to begin a monotonic convergence after such times. This is consistent with the fact that Ω and Λ differ by a total time derivative, and that the tails of the probability distribution function of Λ are Gaussian.

  17. EXISTENCE OF POSITIVE SOLUTION TO TWO-POINT BOUNDARY VALUE PROBLEM FOR A SYSTEM OF SECOND ORDER ORDINARY DIFFERENTIAL EQUATIONS

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    In this paper, we consider a two-point boundary value problem for a system of second order ordinary differential equations. Under some conditions, we show the existence of positive solution to the system of second order ordinary differential equa-tions.

  18. Electrostatic Interactions in Finite Systems treated with Periodic Boundary Conditions: Application to Linear-Scaling Density Functional Theory

    CERN Document Server

    Hine, N D M; Haynes, P D; Skylaris, C K

    2011-01-01

    We present a comparison of methods for treating the electrostatic interactions of finite, isolated systems within periodic boundary conditions (PBCs), within Density Functional Theory (DFT), with particular emphasis on linear-scaling (LS) DFT. Often, PBCs are not physically realistic but are an unavoidable consequence of the choice of basis set and the efficacy of using Fourier transforms to compute the Hartree potential. In such cases the effects of PBCs on the calculations need to be avoided, so that the results obtained represent the open rather than the periodic boundary. The very large systems encountered in LS-DFT make the demands of the supercell approximation for isolated systems more difficult to manage, and we show cases where the open boundary (infinite cell) result cannot be obtained from extrapolation of calculations from periodic cells of increasing size. We discuss, implement and test three very different approaches for overcoming or circumventing the effects of PBCs: truncation of the Coulomb ...

  19. The MORENA Project: Shelf-ocean exchanges and transport processes along the continental margin in the European coastal upwelling region

    Energy Technology Data Exchange (ETDEWEB)

    Fiuza, A.F.G. [Univ. de Lisboa (Portugal). Inst. de Oceanografia; Perez, F. [Inst. Investigaciones Marinas, Vigo (Spain); Johnson, J. [Univ. East Anglia (United Kingdom)] [and others

    1994-12-31

    The MORENA Project (Multidisciplinary Oceanographic Research in the Eastern Boundary of the North Atlantic) is sponsored by the CEC MAST-2 Programme and has as general objective to measure, understand and model shelf-ocean exchange in a typical coastal upwelling region of the eastern boundary layer of the subtropical ocean. This is being attained through a multidisciplinary approach aimed at the quantitative understanding of the physical, chemical and biological processes involved in the transfer of matter (including salt, particulates, nutrients, organic compounds, biomass), momentum and energy across and along the shelf, the shelf break and the slope, in the Iberian region of the European Atlantic. MORENA has the following components: Observations, Modelling and Combined Analysis.

  20. Planetary boundary layer (PBL) monitoring by means of two laser radar systems: experimental results and comparison

    Science.gov (United States)

    Bellecci, C.; Gaudio, P.; Gelfusa, M.; Malizia, A.; Richetta, M.; Serafini, C.; Ventura, P.

    2010-10-01

    The PBL is the lower layer of the atmosphere that is sensitive to the effect of the Earths surface, it controls the flow of heat and momentum between the surface and the free atmosphere, thus playing a key role in atmospheric circulation. At University of Rome "Tor Vergata", Quantum Electronic and Plasma Laboratories (EQP), two mobile Light Detection and Ranging (LIDAR) systems have been developed. With these systems the monitoring of the Planetary Boundary Layer (PBL) has been performed. The first mobile Lidar system is based on a pulsed Nd:YAG Q-Switched laser source operating at three wavelengths: 1064 nm, 532 nm and 355 nm. Acquiring the elastic backscattered signals, it has been possible to estimate the aerosolitic backscattering coefficient at the aim to reconstruct the vertical aerosol profiles. The second one is a Differential Absorption Lidar system (DIAL), composed by a CO2 laser, working in the window spectral range between 9 and 11μm. With this system it has been estimated the water vapour concentration in the PBL region using the two wavelengths 10R20 (10.591 μm) and 10R18 (10.571 μm), which represent, respectively, the absorbing wavelength and non-absorbing one of the water molecule. The comparison of the backscattered radiation at these wavelengths yields the trace gas number density as a function of distance along the field-of-view of the receiving telescope. Diurnal and nocturnal measurements have been performed simultaneity using the two Lidar/Dial systems. Vertical profiles of the aerosolitic backscattering coefficient and water vapour concentration profiles have been estimated. The results and their comparison will be present in this work.

  1. Fluid-mechanical Representation of Plate Boundaries - Trench-Ridge System -

    Science.gov (United States)

    Takaku, M.; Fukao, Y.

    2005-12-01

    Seismic tomography models have been used extensively to simulate mantle convection driven by density heterogeneity. Such simulation to date has been unsuccessful to reconcile itself with the most obvious convection-related phenomenon of plate motions. Here we present a theoretical framework for tomography-based convection modeling to include the plates as an integral part of the mantle convection. We model the lithosphere as a highly viscous, incompressible, Newtonian fluid layer and plate boundaries as faults across which tangential velocities are discontinuous. Fluid-mechanical expressions of such faults have their exact analogies in the seismic source representation theory and can be derived by referring to it. We test this idea against the simplest two-dimensional case with only trench and ridge as plate boundaries, and with only subducting slab as mass anomaly. We model ridge (trench) as the horizontal (vertical) tensile fault that comprises of a conjugate pair of 45-degree dip normal (reverse) faults extending over the entire thickness of the surface layer. The system comprises of three elementary convections, slab mass-driven convection, trench fault-driven convection and ridge fault-driven convection. Flow due to the slab excess mass imposes vertical tensile stress on trench, which is released by flow driven by trench faulting. This faulting converts efficiently the vertical tensile stress to the horizontal tensile stress, which can transmit to extreme distances through the surface viscous layer. This horizontal tensile stress is relieved by flow driven by ridge faulting. The three elementary convections are thus coupled through the stress minimum conditions at ridge and trench. The resultant coupled flow is very plate-like in the surface viscous layer. In this system the horizontal surface velocity depends little on the relative distance between the ridge and trench and depends mostly on the excess weight of the subducting slab. The horizontal speed can be

  2. Control Volume Analysis of Boundary Layer Ingesting Propulsion Systems With or Without Shock Wave Ahead of the Inlet

    Science.gov (United States)

    Kim, Hyun Dae; Felder, James L.

    2011-01-01

    The performance benefit of boundary layer or wake ingestion on marine and air vehicles has been well documented and explored. In this article, a quasi-one-dimensional boundary layer ingestion (BLI) benefit analysis for subsonic and transonic propulsion systems is performed using a control volume of a ducted propulsion system that ingests the boundary layer developed by the external airframe surface. To illustrate the BLI benefit, a relationship between the amount of BLI and the net thrust is established and analyzed for two propulsor types. One propulsor is an electric fan, and the other is a pure turbojet. These engines can be modeled as a turbofan with an infinite bypass ratio for the electric fan, and with a zero bypass ratio for the pure turbojet. The analysis considers two flow processes: a boundary layer being ingested by an aircraft inlet and a shock wave sitting in front of the inlet. Though the two processes are completely unrelated, both represent a loss of total pressure and velocity. In real applications, it is possible to have both processes occurring in front of the inlet of a transonic vehicle. Preliminary analysis indicates that the electrically driven propulsion system benefits most from the boundary layer ingestion and the presence of transonic shock waves, whereas the benefit for the turbojet engine is near zero or negative depending on the amount of total temperature rise across the engine.

  3. The Effects of Climate Change on the Planting Boundary and Potential Yield for Different Rice Cropping Systems in Southern China

    Institute of Scientific and Technical Information of China (English)

    YE Qing; YANG Xiao-guang; LIU Zhi-juan; DAI Shu-wei; LI Yong; XIE Wen-juan; CHEN Fu

    2014-01-01

    Based on climate data from 254 meteorological stations, this study estimated the effects of climate change on rice planting boundaries and potential yields in the southern China during 1951-2010. The results indicated a signiifcant northward shift and westward expansion of northern boundaries for rice planting in the southern China. Compared with the period of 1951-1980, the average temperature during rice growing season in the period of 1981-2010 increased by 0.4°C, and the northern planting boundaries for single rice cropping system (SRCS), early triple cropping rice system (ETCRS), medium triple cropping rice system (MTCRS), and late triple cropping rice system (LTCRS) moved northward by 10, 30, 52 and 66 km, respectively. In addition, compared with the period of 1951-1980, the suitable planting area for SRCS was reduced by 11%during the period of 1981-2010. However, the suitable planting areas for other rice cropping systems increased, with the increasing amplitude of 3, 8, and 10%for ETCRS, MTCRS and LTCRS, respectively. In general, the light and temperature potential productivity of rice decreased by 2.5%. Without considering the change of rice cultivars, the northern planting boundaries for different rice cropping systems showed a northward shift tendency. Climate change resulted in decrease of per unit area yield for SRCS and the annual average yields of ETCRS and LTCRS. Nevertheless, the overall rice production in the entire research area showed a decreasing trend even with the increasing trend of annual average yield for MTCRS.

  4. A free boundary problem for a reaction-diffusion system with nonlinear memory

    DEFF Research Database (Denmark)

    Lin, Zhigui; Ling, Zhi; Pedersen, Michael

    2013-01-01

    We consider a integro-partial differential equation with a free boundary which appears in the theory of the nuclear dynamics. First, local existence and uniqueness are obtained by using the contraction mapping theorem. Then, the behavior of the free boundary and the blow-up criteria are obtained...

  5. Implementation of a boundary layer heat flux parameterization into the Regional Atmospheric Modeling System (RAMS

    Directory of Open Access Journals (Sweden)

    E. L. McGrath-Spangler

    2008-07-01

    Full Text Available The response of atmospheric carbon dioxide to a given amount of surface flux is inversely proportional to the depth of the boundary layer. Overshooting thermals that entrain free tropospheric air down into the boundary layer modify the characteristics and depth of the lower layer through the insertion of energy and mass. This alters the surface energy budget by changing the Bowen ratio and thereby altering the vegetative response and the surface boundary conditions. Although overshooting thermals are important in the physical world, their effects are unresolved in most regional models. A parameterization to include the effects of boundary layer entrainment was introduced into a coupled ecosystem-atmosphere model (SiB-RAMS. The parameterization is based on a downward heat flux at the top of the boundary layer that is proportional to the heat flux at the surface. Results with the parameterization show that the boundary layer simulated is deeper, warmer, and drier than when the parameterization is turned off. These results alter the vegetative stress factors thereby changing the carbon flux from the surface. The combination of this and the deeper boundary layer change the concentration of carbon dioxide in the boundary layer.

  6. Stress relaxation in thin film/substrate systems by grain boundary diffusion : a discrete dislocation framework

    NARCIS (Netherlands)

    Ayas, C; Van der Giessen, E

    2009-01-01

    The relaxation of stress in a thin film due to grain boundary diffusion is investigated in terms of a new discrete dislocation framework. Discrete dislocations along grain boundaries are nucleated from the free surface and are then driven to 'climb' by the Peach-Koehler force, with a mobility that i

  7. The Langley thermal protection system test facility: A description including design operating boundaries

    Science.gov (United States)

    Klich, G. F.

    1976-01-01

    A description of the Langley thermal protection system test facility is presented. This facility was designed to provide realistic environments and times for testing thermal protection systems proposed for use on high speed vehicles such as the space shuttle. Products from the combustion of methane-air-oxygen mixtures, having a maximum total enthalpy of 10.3 MJ/kg, are used as a test medium. Test panels with maximum dimensions of 61 cm x 91.4 cm are mounted in the side wall of the test region. Static pressures in the test region can range from .005 to .1 atm and calculated equilibrium temperatures of test panels range from 700 K to 1700 K. Test times can be as long as 1800 sec. Some experimental data obtained while using combustion products of methane-air mixtures are compared with theory, and calibration of the facility is being continued to verify calculated values of parameters which are within the design operating boundaries.

  8. Chlorine isotope geochemistry of Icelandic thermal fluids: Implications for geothermal system behavior at divergent plate boundaries

    Science.gov (United States)

    Stefánsson, Andri; Barnes, Jaime D.

    2016-09-01

    The chlorine isotope composition of thermal fluids from Iceland were measured in order to evaluate the source of chlorine and possible chlorine isotope fractionation in geothermal systems at divergent plate boundaries. The geothermal systems studied have a wide range of reservoir temperatures from 40 to 437 °C and in-situ pH of 6.15 to 7.15. Chlorine concentrations range from 5.2 to 171 ppm and δ37 Cl values are -0.3 to + 2.1 ‰ (n = 38). The δ37 Cl values of the thermal fluids are interpreted to reflect the source of the chlorine in the fluids. Geothermal processes such as secondary mineral formation, aqueous and vapor speciation and boiling were found to have minimal effects on the δ37 Cl values. However, further work is needed on incorporation of Cl into secondary minerals and its effect on Cl isotope fractionation. Results of isotope geochemical modeling demonstrate that the range of δ37 Cl values documented in the natural thermal fluids can be explained by leaching of the basaltic rocks by meteoric source water under geothermal conditions. Magmatic gas partitioning may also contribute to the source of Cl in some cases. The range of δ37 Cl values of the fluids result mainly from the large range of δ37 Cl values observed for Icelandic basalts, which range from -0.6 to + 1.2 ‰.

  9. Planetary boundary layer as an essential component of the earth's climate system

    Science.gov (United States)

    Davy, Richard; Esau, Igor

    2015-04-01

    Following the traditional engineering approach proposed by Prandtl, the turbulent planetary boundary layers (PBLs) are considered in the climate science as complex, non-linear, essential but nevertheless subordinated components of the earth's climate system. Correspondingly, the temperature variations, dT - a popular and practically important measure of the climate variability, are seen as the system's response to the external heat forcing, Q, e.g. in the energy balance model of the type dT=Q/C (1). The moderation of this response by non-linear feedbacks embedded in the effective heat capacity, C, are to a large degree overlooked. The effective heat capacity is globally determined by the depth of the ocean mixed layer (on multi-decadal and longer time scales) but regionally, over the continents, C is much smaller and determined (on decadal time scales) by the depth, h, of the PBL. The present understanding of the climatological features of turbulent boundary layers is set by the works of Frankignoul & Hasselmann (1976) and Manabe & Stauffer (1980). The former explained how large-scale climate anomalies could be generated in the case of a large C (in the sea surface temperature) by the delta-correlated stochastic forcing (white noise). The latter demonstrated that the climate response to a given forcing is moderated by the depth, h, so that in the shallow PBL the signal should be significantly amplified. At present there are more than 3000 publications (ISI Web of Knowledge) which detail this understanding but the physical mechanisms, which control the boundary layer depth, and statistical relationships between the turbulent and climatological measures remain either unexplored or incorrectly attributed. In order to identify the climatic role of the PBL, the relationships between the PBL depth, h, - as the integral measure of the turbulent processes and micro-circulations due to the surface heterogeneity - and the climatic variability (variations and trends) of

  10. Domoic acid production near California coastal upwelling zones, June 1998

    Energy Technology Data Exchange (ETDEWEB)

    Trainer, V L.(National Marine Fisheries Service); Adams, Nicolaus G.(National Marine Fisheries Service); Bill, Brian D.(National Marine Fisheries Service); Stehr, Carla M.(National Marine Fisheries Service); Wekell, John C.(National Marine Fisheries Service); Moeller, Peter (National Ocean Service, Marine Biotoxins Program); Busman, Mark (National Ocean Service, Marine Biotoxins Program); Woodruff, Dana L.(BATTELLE (PACIFIC NW LAB))

    2000-01-01

    Sea lion mortalities in central California during May and June 1998 were traced to their ingestion of sardines and anchovies that had accumulated the neurotoxin domoic acid. The detection of toxin in urine, feces, and stomach contents of several sea lions represents the first proven occurrence of domoic acid transfer through the food chain to a marine mammal. The pennate diatoms, Pseudo-nitzschia multiseries and P. australis, were the dominant, toxin-producing phytoplankton constituting algal blooms near Monterey Bay, Half Moon Bay, and Oceano Dunes, areas where sea lions with neurological symptoms stranded. Toxic Pseudo-nitzschia were also found near Morrow Bay, Point Conception, Point Arguello, and Santa Barbara, demonstrating that these species were widespread along the central California coast in June 1998. Measurements of domoic acid during three cruises in early June showed the highest cellular toxin levels in P. multiseries near Point A?o Nuevo and in P. australis from Morro w Bay. Maximum cellular domoic acid levels were observed within 20 km of the coast between 0 and 5 m depth, although toxin was also measured to depths of 40 m. Hydrographic data indicated that the highest toxin levels and greatest numbers of toxic cells were positioned in water masses associated with upwelling zones near coastal headlands. Nutrient levels at these sites were less than those typically measured during periods of active upwelling, due to the 1998 El Ni?o event. The flow of cells and/or nutrients from coastal headlands into embayments where cells can multiply in a stratified environment is a possible mechanism of bloom development along the central California coast. This coupling of toxic Pseudo-nitzschia growth near upwelling zones with physical processes involved in cell transport will be understood only when long-term measurements are made at several key coastal locations, aiding in our capability to predict domoic-acid producing algal blooms.

  11. Coastal Upwelling and Deep Fog: 50-year Worldwide Climatology

    Science.gov (United States)

    Koracin, D. R.

    2015-12-01

    An analysis is presented of the marine fog distribution based upon the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) ship observations taken during 1950-2007. Deep fog occurrence is reported in routine weather reports that are encoded in an ICOADS ship observation. Occurrence is estimated by the number of deep fog observations divided by the total present weather observations in a one-degree area centered on latitude and longitude grid point intersections. The mean fog occurrence for the summer (June-July-August) 1950-2007 was computed for each one degree point for the world. There are five major world locations with coastal SST minimums due to wind driven upwelling. Four of these are during the local summer on the eastern side of a semi-permanent anticyclone on eastern sides of northern and southern mid-latitudes of the Pacifica and the Atlantic. The fifth is during the SW monsoon in the Indian Ocean. For all five of these locations, the deep fog occurrence is at maximum during the upwelling season, with the greatest occurrences concentrated along the coast and isolated over the SST minimum. For the five coastal fog maxima, the greatest and longest duration occurrence along coast occurrence is associated with the coldest sea surface temperature and longest along coast occurrence, which is along N. California- S. Oregon. In contrast, the lowest occurrence of fog and the least along coast occurrence is associated with the warmest sea surface temperatures and least along coast occurrence along the SE Arabian Peninsula. The remaining three zones, Peru-Chile, NW Africa, and SW Africa are between the two extremes in fog occurrence, along coast coverage and sea surface temperature. Peru-Chile is more complex than the others as the Peru upwelling and fog appears the more dominant although ship observations are sparse along Chile.

  12. Coastal upwelling in Southern Coast of Sumbawa Island, Indonesia

    Science.gov (United States)

    Taufikurahman, Qamal; Hidayat, Rahmat

    2017-01-01

    Circulation and water mass characteristics in southern coast of Sumbawa Island is strongly influenced by monsoon which change each season. This research aims to (1) identify the Ekman transport and Ekman pumping variations and (2) analyse the SST and chlorophyll-a variability. During Juni-July-August (JJA) season, the highest value of Ekman transport (-0.72 m2 s-1) moves the water mass towards Indian Ocean while Ekman pumping (0.15x10-4 m2 s-1) rises the water mass to the surface (upwelling). Impact of coastal upwelling was identified by cooling SST and high chlorophyll-a. Coolest SST (26.58°C) associated with highest chlorophyll-a (0.6 mg m-3) were found in JJA season. Inter-annual variation of SST and chlorophyll-a concentrations during 2003-2015 is driven by Ekman transport and Ekman pumping. Coolest SST and highest chlorophyll-a were found in JJA season in 2006 with an average value of 25.98°C and 0.78 mg m-3, also in JJA season in 2008 with an average value of 26°C and 0.71 mg m-3. Thus the process of Ekman transport and Ekman pumping has an important role in lifting the cold water high nutriens from the deeper layer to surface. The high concentration of chlorophyll-a in water is the impact of appointment nutrient from the deeper layer by the coastal upwelling.

  13. The Asymptotic Behavior and the Quasineutral Limit for the Bipolar Euler-Poisson System with Boundary Effects and a Vacuum

    Institute of Scientific and Technical Information of China (English)

    Yeping LI

    2013-01-01

    In this paper,a one-dimensional bipolar Euler-Poisson system (a hydrodynamic model) from semiconductors or plasmas with boundary effects is considered.This system takes the form of Euler-Poisson with an electric field and frictional damping added to the momentum equations.The large-time behavior of uniformly bounded weak solutions to the initial-boundary value problem for the one-dimensional bipolar Euler-Poisson system is firstly presented.Next,two particle densities and the corresponding current momenta are verified to satisfy the porous medium equation and the classical Darcy's law time asymptotically.Finally,as a by-product,the quasineutral limit of the weak solutions to the initial-boundary value problem is investigated in the sense that the bounded L∞ entropy solution to the one-dimensional bipolar Euler-Poisson system converges to that of the corresponding one-dimensional compressible Euler equations with damping exponentially fast as t → +∞.As far as we know,this is the first result about the asymptotic behavior and the quasineutral limit for the one-dimensional bipolar Euler-Poisson system with boundary effects and a vacuum.

  14. Isotopic evidences of past upwelling intensity in the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P

    covering a time span of 520 ka. In these studies, the Dd 18 O and Dd 13 C data P.D. Naidu / Global and Planetary Change 40 (2004) 285–293286 Greater than 70% of the annual particle flux in the upwelling areas of Arabian Sea occurs during the SW monsoon...C where DBD is the bulk density of the sediment (in grams per cubic centimeter), LSR is the linear sedi- P.D. Naidu / Global and Planetary Change 40 (2004) 285–293 287 Fig. 1. Physiography and bathymetry of the western Arabian Sea along with location...

  15. The upwelling record in the sediments of the westen continental margin of India

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.; PrakashBabu, C.; Rao, Ch.M.

    , International Indian Ocean Expedition, Oceanographic Monographs, 2,173 pp. DIESTER-HAASS L. (1976) Quaternary accumulation rates of biogenous and terrigenous components on the East Atlantic continental slope off NW Africa. Marine Geology, 21, 1-24. Dm.... THIEDE (1983) Coastal upwelling its sediment record. Plenum Press, New York, 604 pp. THIEDE J. (1983) Skeletal plankton and nekton in upwelling water masses off north western south America and northwest Africa. In: Coastal upwelling: its sediment record...

  16. Alkenone-based temperature patterns along the eastern South Pacific Coastal Ocean: the effect of upwelling and advection on the sedimentary alkenone unsaturation-index (U37K'

    Directory of Open Access Journals (Sweden)

    J. Garcés-Vargas

    2010-01-01

    Full Text Available We report that the sedimentary record of alkenone unsaturation-index (U37K' in the eastern South Pacific displays a wide range of temperatures, in response to sea surface temperature (SST, as well as nutrient concentrations. The U37K' inshore-offshore trend shows low-correlation with SSTs at many transitional sites (50–200 km offshore, and in one oligotrophic coastal site (~20° S. In contrast, in open-ocean sites SSTs play the expected dominant role. The latitudinal trend shows that nitrate, phosphate and/or temperature affect distinctively the U37K', suggesting progressive high-impacts in areas with permanent nutrient-stress conditions (~20° S, which is consistent with previous experiments. In contrast, this impact is slightly and not observable in transitional and open-ocean areas, respectively, where the coupling between offshore propagation of mesoscale eddies and upwelling filaments supply additional chlorophyll/nutrient. This study is a first field approximation to the impacts of thermal/non-thermal factors over the unsaturation-index in eastern Boundary Current systems, which would help in future temperature reconstructions.

  17. Narrowing of the Upwelling Branch of the Brewer-Dobson Circulation and Hadley Cell in Chemistry-Climate Model Simulations of the 21st Century

    Science.gov (United States)

    Li, Feng; Stolarski, Richard S.; Pawson, Steven; Newman, Paul A.; Waugh, Darryn

    2010-01-01

    Changes in the width of the upwelling branch of the Brewer-Dobson circulation and Hadley cell in the 21st Century are investigated using simulations from a coupled chemistry-climate model. In these model simulations the tropical upwelling region narrows in the troposphere and lower stratosphere. The narrowing of the Brewer-Dobson circulation is caused by an equatorward shift of Rossby wave critical latitudes and Eliassen-Palm flux convergence in the subtropical lower stratosphere. In the troposphere, the model projects an expansion of the Hadley cell's poleward boundary, but a narrowing of the Hadley cell's rising branch. Model results suggest that eddy forcing may also play a part in the narrowing of the rising branch of the Hadley cell.

  18. The Effects of Changing Climatological Variables on Upwelling along the Southern California Coast

    Science.gov (United States)

    Grasmick, C.; Kudela, R. M.; Bausell, J.

    2015-12-01

    A large part of the high productivity of CA current ecosystems can be attributed to Ekman upwelling of cold, nutrient-rich water, driven by north winds running parallel to shore. As meteorological (e.g. wind direction and velocity, atmospheric pressure fields, etc.) and oceanographic (e.g. sea surface temperature) parameters change in the context of climate change, it is unclear how ecosystems and the coastal upwelling on which they depend, will be impacted. To better understand the effects of meteorological and oceanographic forcing on coastal upwelling, eleven years (2005-2015) of data were taken from satellites, weather stations and data-collecting buoys located in and around the Santa Barbara Channel as part of the NASA Student Airborne Research Program (SARP). These data were then analyzed using regression and time-series cross-correlation statistics in order to identify trends in meteorological and oceanographic cycles, their relationship to localized upwelling (e.g. upwelling indices), and how climate change may impact upwelling. Results indicate that as temperature has increased over the last four years (as a result of the 'warm blob'), upwelling has decreased. They also indicate differences in the annual cycles of cross-shore pressure gradients during years of poor versus years when upwelling conditions are favorable. This documented dependence of the coastal wind on sea surface temperature could have important implications as our oceans change; elevated sea surface temperatures, such as those associated with the 'warm blob', may result in less coastal upwelling and lower ecosystem productivity.

  19. Delayed upwelling alters nearshore coastal ocean ecosystems in the northern California current.

    Science.gov (United States)

    Barth, John A; Menge, Bruce A; Lubchenco, Jane; Chan, Francis; Bane, John M; Kirincich, Anthony R; McManus, Margaret A; Nielsen, Karina J; Pierce, Stephen D; Washburn, Libe

    2007-03-06

    Wind-driven coastal ocean upwelling supplies nutrients to the euphotic zone near the coast. Nutrients fuel the growth of phytoplankton, the base of a very productive coastal marine ecosystem [Pauly D, Christensen V (1995) Nature 374:255-257]. Because nutrient supply and phytoplankton biomass in shelf waters are highly sensitive to variation in upwelling-driven circulation, shifts in the timing and strength of upwelling may alter basic nutrient and carbon fluxes through marine food webs. We show how a 1-month delay in the 2005 spring transition to upwelling-favorable wind stress in the northern California Current Large Marine Ecosystem resulted in numerous anomalies: warm water, low nutrient levels, low primary productivity, and an unprecedented low recruitment of rocky intertidal organisms. The delay was associated with 20- to 40-day wind oscillations accompanying a southward shift of the jet stream. Early in the upwelling season (May-July) off Oregon, the cumulative upwelling-favorable wind stress was the lowest in 20 years, nearshore surface waters averaged 2 degrees C warmer than normal, surf-zone chlorophyll-a and nutrients were 50% and 30% less than normal, respectively, and densities of recruits of mussels and barnacles were reduced by 83% and 66%, respectively. Delayed early-season upwelling and stronger late-season upwelling are consistent with predictions of the influence of global warming on coastal upwelling regions.

  20. El Niño and similar perturbation effects on the benthos of the Humboldt, California, and Benguela Current upwelling ecosystems

    Directory of Open Access Journals (Sweden)

    W. E. Arntz

    2006-01-01

    Full Text Available To a certain degree, Eastern Boundary Current (EBC ecosystems are similar: Cold bottom water from moderate depths, rich in nutrients, is transported to the euphotic zone by a combination of trade winds, Coriolis force and Ekman transport. The resultant high primary production fuels a rich secondary production in the upper pelagic and nearshore zones, but where O2 exchange is restricted, it creates oxygen minimum zones (OMZs at shelf and upper slope (Humboldt and Benguela Current or slope depths (California Current. These hypoxic zones host a specifically adapted, small macro- and meiofauna together with giant sulphur bacteria that use nitrate to oxydise H2S. In all EBC, small polychaetes, large nematodes and other opportunistic benthic species have adapted to the hypoxic conditions and co-exist with sulphur bacteria, which seem to be particularly dominant off Peru and Chile. However, a massive reduction of macrobenthos occurs in the core of the OMZ. In the Humboldt Current area the OMZ ranges between <100 and about 600 m, with decreasing thickness in a poleward direction. The OMZ merges into better oxygenated zones towards the deep sea, where large cold-water mega- and macrofauna occupy a dominant role as in the nearshore strip. The Benguela Current OMZ has a similar upper limit but remains shallower. It also hosts giant sulphur bacteria but little is known about the benthic fauna. However, sulphur eruptions and intense hypoxia might preclude the coexistence of significant mega- und macrobenthos. Conversely, off North America the upper limit of the OMZ is considerably deeper (e.g., 500–600 m off California and Oregon, and the lower boundary may exceed 1000m. The properties described are valid for very cold and cold (La Niña and "normal" ENSO conditions with effective upwelling of nutrient-rich bottom water. During warm (El Niño episodes, warm water masses of low oxygen concentration from oceanic and equatorial regions enter the upwelling

  1. boundary dissipation

    Directory of Open Access Journals (Sweden)

    Mehmet Camurdan

    1998-01-01

    are coupled by appropriate trace operators. This overall model differs from those previously studied in the literature in that the elastic chamber floor is here more realistically modeled by a hyperbolic Kirchoff equation, rather than by a parabolic Euler-Bernoulli equation with Kelvin-Voight structural damping, as in past literature. Thus, the hyperbolic/parabolic coupled system of past literature is replaced here by a hyperbolic/hyperbolic coupled model. The main result of this paper is a uniform stabilization of the coupled PDE system by a (physically appealing boundary dissipation.

  2. GLOBAL WEAKLY DISCONTINUOUS SOLUTIONS TO A KIND OF MIXED INITIAL-BOUNDARY VALUE PROBLEM FOR INHOMOGENEOUS QUASILINEAR HYPERBOLIC SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    GUO Fei

    2007-01-01

    In this paper we study the mixed initial-boundary value problem for inhomogeneous quasilinear hyperbolic systems in the domain D={(t,x)| t≥O,x≥O}.Under the assumption that the source term satisfies the matching condition,a sufficient condition to guarantee the existence and uniqueness of global weakly discontinuous solution is given.

  3. Finite difference method of first boundary problem for quasilinear parabolic systems ( Ⅳ)——Convergence of iteration

    Institute of Scientific and Technical Information of China (English)

    周毓麟; 沈隆钧; 袁光伟

    1997-01-01

    More work is done to study the explicit, weak and strong implicit difference solution for the first boundary problem of quasilinear parabolic system:where u, , and f are m-dimensional vector valued functions, A is an m × m positively definite matrix, and ut = For this problem, the convergence of iteration for the general difference schemes is proved.

  4. EXISTENCE AND NON-EXISTENCE OF GLOBAL SOLUTIONS OF A DEGENERATE PARABOLIC SYSTEM WITH NONLINEAR BOUNDARY CONDITIONS

    Institute of Scientific and Technical Information of China (English)

    Sun Fuqin; Wang Mingxin

    2004-01-01

    In this paper, we study the non-negative solutions to a degenerate parabolic system with nonlinear boundary conditions in the multi-dimensional case.By the upper and lower solutions method, we give the conditions on the existence and non-existence of global solutions.

  5. Existence and Uniqueness of Solutions for the System of Nonlinear Fractional Differential Equations with Nonlocal and Integral Boundary Conditions

    Directory of Open Access Journals (Sweden)

    Allaberen Ashyralyev

    2012-01-01

    Full Text Available In the present study, the nonlocal and integral boundary value problems for the system of nonlinear fractional differential equations involving the Caputo fractional derivative are investigated. Theorems on existence and uniqueness of a solution are established under some sufficient conditions on nonlinear terms. A simple example of application of the main result of this paper is presented.

  6. Boundary Influences on HAB Phytoplankton Ecology in a Stratification-Enhanced Upwelling Shadow

    Science.gov (United States)

    2014-05-13

    contained in 10 mL of sample. Filters were mounted on a glass slide with immersion oil and frozen at -80 "C until enumeration. Samples were defrosted and...blooms: are thin layers the missing connection? Estuaries Coasts: J. CERE 31. 396-401, http://dx.doi.org/10.1007/sl2237-007-9025-4. Moita, M.T., Palma

  7. Numerical methods for stiff systems of two-point boundary value problems

    Science.gov (United States)

    Flaherty, J. E.; Omalley, R. E., Jr.

    1983-01-01

    Numerical procedures are developed for constructing asymptotic solutions of certain nonlinear singularly perturbed vector two-point boundary value problems having boundary layers at one or both endpoints. The asymptotic approximations are generated numerically and can either be used as is or to furnish a general purpose two-point boundary value code with an initial approximation and the nonuniform computational mesh needed for such problems. The procedures are applied to a model problem that has multiple solutions and to problems describing the deformation of thin nonlinear elastic beam that is resting on an elastic foundation.

  8. Uniform blow-up profiles and boundary layer for a parabolic system with localized nonlinear reaction terms

    Institute of Scientific and Technical Information of China (English)

    LI Huiling; WANG Mingxin

    2005-01-01

    This paper deals with the blow-up properties of the solution to a semilinear parabolic system with localized nonlinear reaction terms, subject to the null Dirichlet boundary condition. We first give sufficient conditions for that the classical solution blows up in the finite time, secondly give necessary conditions and a sufficient condition for that two components blow up simultaneously, and then obtain the uniform blow-up profiles in the interior. Finally we describe the asymptotic behavior of the blow-up solution in the boundary layer.

  9. Nonlinear Gulf Stream Interaction with the Deep Western Boundary Current System: Observations and a Numerical Simulation

    Science.gov (United States)

    Dietrich, David E.; Mehra, Avichal; Haney, Robert L.; Bowman, Malcolm J.; Tseng, Yu-Heng

    2003-01-01

    Gulf Stream (GS) separation near its observed Cape Hatteras (CH) separation location, and its ensuing path and dynamics, is a challenging ocean modeling problem. If a model GS separates much farther north than CH, then northward GS meanders, which pinch off warm core eddies (rings), are not possible or are strongly constrained by the Grand Banks shelfbreak. Cold core rings pinch off the southward GS meanders. The rings are often re-absorbed by the GS. The important warm core rings enhance heat exchange and, especially, affect the northern GS branch after GS bifurcation near the New England Seamount Chain. This northern branch gains heat by contact with the southern branch water upstream of bifurcation, and warms the Arctic Ocean and northern seas, thus playing a major role in ice dynamics, thermohaline circulation and possible global climate warming. These rings transport heat northward between the separated GS and shelf slope/Deep Western Boundary Current system (DWBC). This region has nearly level time mean isopycnals. The eddy heat transport convergence/divergence enhances the shelfbreak and GS front intensities and thus also increases watermass transformation. The fronts are maintained by warm advection by the Florida Current and cool advection by the DWBC. Thus, the GS interaction with the DWBC through the intermediate eddy field is climatologically important.

  10. Morphotropic phase boundary and magnetoelastic behaviour in ferromagnetic Tb1-xGdxFe2 system

    Energy Technology Data Exchange (ETDEWEB)

    Adil, Murtaza [School of Sciences, Frontier Institute of Science and Technology, MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory for Mechanical Behaviour of Materials, Xi' an Jiaotong University, Xi' an 710049, China; Yang, Sen [School of Sciences, Frontier Institute of Science and Technology, MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory for Mechanical Behaviour of Materials, Xi' an Jiaotong University, Xi' an 710049, China; Mi, Meng [School of Sciences, Frontier Institute of Science and Technology, MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory for Mechanical Behaviour of Materials, Xi' an Jiaotong University, Xi' an 710049, China; Zhou, Chao [School of Sciences, Frontier Institute of Science and Technology, MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory for Mechanical Behaviour of Materials, Xi' an Jiaotong University, Xi' an 710049, China; Wang, Jieqiong [School of Sciences, Frontier Institute of Science and Technology, MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory for Mechanical Behaviour of Materials, Xi' an Jiaotong University, Xi' an 710049, China; Zhang, Rui [School of Sciences, Frontier Institute of Science and Technology, MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory for Mechanical Behaviour of Materials, Xi' an Jiaotong University, Xi' an 710049, China; Liao, Xiaoqi [School of Sciences, Frontier Institute of Science and Technology, MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory for Mechanical Behaviour of Materials, Xi' an Jiaotong University, Xi' an 710049, China; Wang, Yu [School of Sciences, Frontier Institute of Science and Technology, MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory for Mechanical Behaviour of Materials, Xi' an Jiaotong University, Xi' an 710049, China; Ren, Xiaobing [School of Sciences, Frontier Institute of Science and Technology, MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory for Mechanical Behaviour of Materials, Xi' an Jiaotong University, Xi' an 710049, China; Song, Xiaoping [School of Sciences, Frontier Institute of Science and Technology, MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory for Mechanical Behaviour of Materials, Xi' an Jiaotong University, Xi' an 710049, China; Ren, Yang [X-Ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA

    2015-03-30

    Morphotropic phase boundary (MPB), separating two ferroic phases of different crystal symmetries, has been studied extensively for its extraordinary enhancement of piezoelectricity in ferroelectrics. Based on the same mechanism, we have designed a magnetic MPB in the pseudobinary ferromagnetic system of Tb1-xGdxFe2 and the corresponding crystal structure, magnetic properties, and magnetostriction are explored. With the synchrotron x-ray diffractometry, the structure symmetry of TbFe2-rich compositions is detected to be rhombohedral (R) and that of GdFe2-rich compositions is tetragonal (T) below T-c. With the change of concentration, the value of magnetostriction of the samples changes monotonously, while the MPB composition Tb0.1Gd0.9Fe2, which corresponds to the coexistence of R and T phases, exhibits the maximum magnetization among all available compositions and superposition of magnetostriction behaviour of R and T phases. Our result of MPB phenomena in ferromagnets may provide an effective route to design functional magnetic materials with exotic properties. (C) 2015 AIP Publishing LLC.

  11. Southern Ocean warming delayed by circumpolar upwelling and equatorward transport

    Science.gov (United States)

    Armour, Kyle C.; Marshall, John; Scott, Jeffery R.; Donohoe, Aaron; Newsom, Emily R.

    2016-07-01

    The Southern Ocean has shown little warming over recent decades, in stark contrast to the rapid warming observed in the Arctic. Along the northern flank of the Antarctic Circumpolar Current, however, the upper ocean has warmed substantially. Here we present analyses of oceanographic observations and general circulation model simulations showing that these patterns--of delayed warming south of the Antarctic Circumpolar Current and enhanced warming to the north--are fundamentally shaped by the Southern Ocean's meridional overturning circulation: wind-driven upwelling of unmodified water from depth damps warming around Antarctica; greenhouse gas-induced surface heat uptake is largely balanced by anomalous northward heat transport associated with the equatorward flow of surface waters; and heat is preferentially stored where surface waters are subducted to the north. Further, these processes are primarily due to passive advection of the anomalous warming signal by climatological ocean currents; changes in ocean circulation are secondary. These findings suggest the Southern Ocean responds to greenhouse gas forcing on the centennial, or longer, timescale over which the deep ocean waters that are upwelled to the surface are warmed themselves. It is against this background of gradual warming that multidecadal Southern Ocean temperature trends must be understood.

  12. Coastal upwelling at Cape Frio: Its structure and weakening

    Science.gov (United States)

    Jury, Mark R.

    2017-01-01

    Cape Frio at the Angola-Namibia border, is the northern-most coastal upwelling cell of the Benguela Current ( 17S, 11E) and is sensitive to climate variability. This study provides new insights using daily high resolution satellite and ocean-atmosphere reanalysis datasets in the period 1985-2015. The annual cycle of SST follows two months behind the net heat balance and wind stress curl, reaching a minimum in July-September. Ranking the daily SST record, two intense multi-day upwelling events stand out. The more recent case of 26-29 August 2005 is studied, given the greater density and sophistication of satellite data. A coastal wind jet >10 m s-1 develops next to Cape Frio, with sharp edges imposed by a thermal inversion and the mountainous cape. The cold plume wind stress curl and downward heat fluxes. Leeward of Cape Frio, a wind shadow and poleward currents contribute to phytoplankton blooms. Daily time series 1985-2015 reveal warming SST +.035C/yr and diminishing winds -0.025 m s-1/yr. The trend toward cyclonic winds over Angola and the northern Benguela Current reflects a poleward and offshore shift of the main axis of southeasterly winds.

  13. Outer boundary of major discharge areas of Death Valley regional flow system, Nevada and California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The digital data set delineates the outer boundary of each major discharge area evaluated as part of the study. These areas were used to refine estimates of...

  14. INITIAL-BOUNDARY VALUE PROBLEM FOR THE LANDAU-LIFSHITZ SYSTEM WITH APPLIED FIELD

    Institute of Scientific and Technical Information of China (English)

    Guo Boling; Ding Shijin

    2000-01-01

    In this paper, the existence and partial regularity of weak solution to the initial-boundary value problem of Landau-Lifshitz equations with applied fields in a 2D bounded domain are obtained by the penalty method.

  15. Motion of particles in solar and galactic systems by using Neumann boundary condition

    Science.gov (United States)

    Shenavar, Hossein

    2016-12-01

    A new equation of motion, which is derived previously by imposing Neumann boundary condition on cosmological perturbation equations (Shenavar in Astrophys. Space Sci., 2016a, doi: 10.1007/s10509-016-2676-5), is investigated. By studying the precession of perihelion, it is shown that the new equation of motion suggests a small, though detectable, correction in orbits of solar system objects. Then a system of particles is surveyed to have a better understanding of galactic structures. Also the general form of the force law is introduced by which the rotation curve and mass discrepancy of axisymmetric disks of stars are derived. In addition, it is suggested that the mass discrepancy as a function of centripetal acceleration becomes significant near a constant acceleration 2c1a0 where c1 is the Neumann constant and a0 = 6.59 ×10^{-10} m/s2 is a fundamental acceleration. Furthermore, it is shown that a critical surface density equal to σ0=a0/G, in which G is the Newton gravitational constant, has a significant role in rotation curve and mass discrepancy plots. Also, the specific form of NFW mass density profile at small radii, ρ∝1/r, is explained too. Finally, the present model will be tested by using a sample of 39 LSB galaxies for which we will show that the rotation curve fittings are generally acceptable. The derived mass to light ratios too are found within the plausible bound except for the galaxy F571-8.

  16. Development of ion diagnostic system based on electrostatic probe in the boundary plasma of the JFT-2M tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Uehara, Kazuya; Kawakami, Tomohide [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment; Amemiya, Hiroshi; Hoethker, K.; Cosler, A.; Bieger, W.

    1995-06-01

    An ion diagnostic system using electrostatic probes for measurements in the JFT-2M tokamak boundary plasma has been developed under the collaboration program between KFA and JAERI. The rotating double probe system, on which the Hoethker double probe and Amemiya asymmetric probe can mounted, are manufactured at KFA workshop while the linear driver to support the rotating double probe, the ion toothbrush probe, the Katsumata probe and the cubic Mach probe are developed at JAERI. This report describes the hardware of this probe system for ion diagnostics in the boundary plasma and preliminary data obtained by means of this system. Furthermore, results on the transport are estimated on the basis of these probe data. (author).

  17. The reduction of biological production induced by mesoscale mixing: a modelling study in the Benguela upwelling

    CERN Document Server

    Hernández-Carrasco, Ismael; Hernández-García, Emilio; Garçon, Veronique; López, Cristóbal

    2013-01-01

    Recent studies, both based on remote sensed data and coupled models, showed a reduction of biological productivity due to vigorous horizontal mixing in upwelling systems. In order to better understand this phenomenon, we have considered a system of oceanic flow in the Benguela area coupled with a simple biogeochemical model of Nutrient-Phyto-Zooplankton (NPZ) type. For the flow three different surface velocity fields are considered: one derived from satellite altimetry data, and the other two from a regional numerical model at two different spatial resolutions. We computed horizontal particle dispersion in terms of Lyapunov Exponents, and analyzed their correlations with phytoplankton concentrations. Our modelling approach confirms that in the south Benguela, there is a reduction of biological activity when stirring is increased. Two-dimensional offshore advection seems to be the dominant process involved. In the northern area, other factors not taken into account in our simulation are influencing the ecosyst...

  18. Positive Solutions for (n-1,1-Type Singular Fractional Differential System with Coupled Integral Boundary Conditions

    Directory of Open Access Journals (Sweden)

    Ying Wang

    2014-01-01

    Full Text Available We study the positive solutions of the (n-1,1-type fractional differential system with coupled integral boundary conditions. The conditions for the existence of positive solutions to the system are established. In addition, we derive explicit formulae for the estimation of the positive solutions and obtain the unique positive solution when certain additional conditions hold. An example is then given to demonstrate the validity of our main results.

  19. The active disturbance rejection control approach to stabilisation of coupled heat and ODE system subject to boundary control matched disturbance

    Science.gov (United States)

    Guo, Bao-Zhu; Liu, Jun-Jun; AL-Fhaid, A. S.; Younas, Arshad Mahmood M.; Asiri, Asim

    2015-08-01

    We consider stabilisation for a linear ordinary differential equation system with input dynamics governed by a heat equation, subject to boundary control matched disturbance. The active disturbance rejection control approach is applied to estimate, in real time, the disturbance with both constant high gain and time-varying high gain. The disturbance is cancelled in the feedback loop. The closed-loop systems with constant high gain and time-varying high gain are shown, respectively, to be practically stable and asymptotically stable.

  20. Ecology of planktonic cephalopod paralarvae in coastal upwelling systems

    OpenAIRE

    Roura, Álvaro

    2013-01-01

    [spa] Esta tesis es el fruto de tres años de muestreo nocturno de zooplancton en la Ría de Vigo (2008-2010) y dos campañas oceanográficas realizadas sobre la plataforma y el talud continental del noroeste de la Península Ibérica (CAIBEX-I) y del noroeste de África (CAIBEX-III). El objetivo principal de este trabajo era comprender aspectos fundamentales de la ecología de las paralarvas planctónicas del pulpo común, Octopus vulgaris, tales como su dieta en la naturaleza, su distribución en las ...

  1. System for conversion between the boundary representation model and a constructive solid geometry model of an object

    Science.gov (United States)

    Christensen, Noel C.; Emery, James D.; Smith, Maurice L.

    1988-04-05

    A system converts from the boundary representation of an object to the constructive solid geometry representation thereof. The system converts the boundary representation of the object into elemental atomic geometrical units or I-bodies which are in the shape of stock primitives or regularized intersections of stock primitives. These elemental atomic geometrical units are then represented in symbolic form. The symbolic representations of the elemental atomic geometrical units are then assembled heuristically to form a constructive solid geometry representation of the object usable for manufacturing thereof. Artificial intelligence is used to determine the best constructive solid geometry representation from the boundary representation of the object. Heuristic criteria are adapted to the manufacturing environment for which the device is to be utilized. The surface finish, tolerance, and other information associated with each surface of the boundary representation of the object are mapped onto the constructive solid geometry representation of the object to produce an enhanced solid geometry representation, particularly useful for computer-aided manufacture of the object.

  2. Derivative matrices of a skew ray for spherical boundary surfaces and their applications in system analysis and design.

    Science.gov (United States)

    Lin, Psang Dain

    2014-05-10

    In a previous paper [Appl. Opt.52, 4151 (2013)], we presented the first- and second-order derivatives of a ray for a flat boundary surface to design prisms. In this paper, that scheme is extended to determine the Jacobian and Hessian matrices of a skew ray as it is reflected/refracted at a spherical boundary surface. The validity of the proposed approach as an analysis and design tool is demonstrated using an axis-symmetrical system for illustration purpose. It is found that these two matrices can provide the search direction used by existing gradient-based schemes to minimize the merit function during the optimization stage of the optical system design process. It is also possible to make the optical system designs more automatic, if the image defects can be extracted from the Jacobian and Hessian matrices of a skew ray.

  3. A new method of boundary parameter estimation for a two-dimensional diffusion system under noisy observations

    Science.gov (United States)

    Sunahara, Y.; Kojima, F.

    1987-01-01

    The purpose of this paper is to establish a method for identifying unknown parameters involved in the boundary state of a class of diffusion systems under noisy observations. A mathematical model of the system dynamics is given by a two-dimensional diffusion equation. Noisy observations are made by sensors allocated on the system boundary. Starting with the mathematical model mentioned above, an online parameter estimation algorithm is proposed within the framework of the maximum likelihood estimation. Existence of the optimal solution and related necessary conditions are discussed. By solving a local variation of the cost functional with respect to the perturbation of parameters, the estimation mechanism is proposed in a form of recursive computations. Finally, the feasibility of the estimator proposed here is demonstrated through results of digital simulation experiments.

  4. Reduced order models, inertial manifolds, and global bifurcations: searching instability boundaries in nuclear power systems

    Energy Technology Data Exchange (ETDEWEB)

    Suarez-Antola, Roberto, E-mail: roberto.suarez@miem.gub.u, E-mail: rsuarez@ucu.edu.u [Universidad Catolica del Uruguay, Montevideo (Uruguay). Fac. de Ingenieria y Tecnologias. Dept. de Matematica; Ministerio de Industria, Energia y Mineria, Montevideo (Uruguay). Direccion General de Secretaria

    2011-07-01

    One of the goals of nuclear power systems design and operation is to restrict the possible states of certain critical subsystems to remain inside a certain bounded set of admissible states and state variations. In the framework of an analytic or numerical modeling process of a BWR power plant, this could imply first to find a suitable approximation to the solution manifold of the differential equations describing the stability behavior, and then a classification of the different solution types concerning their relation with the operational safety of the power plant. Inertial manifold theory gives a foundation for the construction and use of reduced order models (ROM's) of reactor dynamics to discover and characterize meaningful bifurcations that may pass unnoticed during digital simulations done with full scale computer codes of the nuclear power plant. The March-Leuba's BWR ROM is generalized and used to exemplify the analytical approach developed here. A nonlinear integral-differential equation in the logarithmic power is derived. Introducing a KBM Ansatz, a coupled set of two nonlinear ordinary differential equations is obtained. Analytical formulae are derived for the frequency of oscillation and the parameters that determine the stability of the steady states, including sub- and supercritical PAH bifurcations. A Bautin's bifurcation scenario seems possible on the power-flow plane: near the boundary of stability, a region where stable steady states are surrounded by unstable limit cycles surrounded at their turn by stable limit cycles. The analytical results are compared with recent digital simulations and applications of semi-analytical bifurcation theory done with reduced order models of BWR. (author)

  5. Changes in optical characteristics of surface microlayers hint to photochemically and microbially mediated DOM turnover in the upwelling region off the coast of Peru

    Science.gov (United States)

    Galgani, Luisa; Engel, Anja

    2016-04-01

    The coastal upwelling system off the coast of Peru is characterized by high biological activity and a pronounced subsurface oxygen minimum zone, as well as associated emissions of atmospheric trace gases such as N2O, CH4 and CO2. From 3 to 23 December 2012, R/V Meteor (M91) cruise took place in the Peruvian upwelling system between 4.59 and 15.4° S, and 82.0 to 77.5° W. During M91 we investigated the composition of the sea-surface microlayer (SML), the oceanic uppermost boundary directly subject to high solar radiation, often enriched in specific organic compounds of biological origin like chromophoric dissolved organic matter (CDOM) and marine gels. In the SML, the continuous photochemical and microbial recycling of organic matter may strongly influence gas exchange between marine systems and the atmosphere. We analyzed SML and underlying water (ULW) samples at 38 stations focusing on CDOM spectral characteristics as indicator of photochemical and microbial alteration processes. CDOM composition was characterized by spectral slope (S) values and excitation-emission matrix fluorescence (EEMs), which allow us to track changes in molecular weight (MW) of DOM, and to determine potential DOM sources and sinks. Spectral slope S varied between 0.012 to 0.043 nm-1 and was quite similar between SML and ULW, with no significant differences between the two compartments. Higher S values were observed in the ULW of the southern stations below 15° S. By EEMs, we identified five fluorescent components (F1-5) of the CDOM pool, of which two had excitation/emission characteristics of amino-acid-like fluorophores (F1, F4) and were highly enriched in the SML, with a median ratio SML : ULW of 1.5 for both fluorophores. In the study region, values for CDOM absorption ranged from 0.07 to 1.47 m-1. CDOM was generally highly concentrated in the SML, with a median enrichment with respect to the ULW of 1.2. CDOM composition and changes in spectral slope properties suggested a local

  6. Positive Solutions of Sub-Linear Semi-Positone Boundary Value Problem System%次线性半正微分边值系统的正解

    Institute of Scientific and Technical Information of China (English)

    徐西安

    2008-01-01

    In this paper,we study the existence of positive solutions of a sub-linear semi-positone differential boundary value problems system with positive parameter.We prove that the semipositone differential boundary value problems system has at least one positive solution for the parameter sufficiently large.

  7. How marine upwelling influences the distribution of Artemesia longinaris (Decapoda: Penaeoidea?

    Directory of Open Access Journals (Sweden)

    Gustavo S Sancinetti

    2014-05-01

    Full Text Available Upwelling events can occur in most of the oceans altering the water physical, chemical and sediment conditions and consequently the species communities dwelling the areas. For better understanding the behavior of populations inhabiting upwelling regions, the spatial and temporal distribution of a Penaeoidea shrimp was studied correlating it with the abiotic factors that vary during upwelling and non-upwelling periods in an area under influence of Cabo Frio upwelling. Bottom salinity and temperature, organic matter and sediment type from each station were sampled from March 2008 to February 2010, in six stations located between 5 and 45 m depth. The lowest temperatures were recorded during spring and summer for both years with temperature values lower than 19ºC. A total of 26,466 Artemesia longinaris shrimps were captured mainly in 10-35 m depth. Upwelling periods showed significant differences in abundance in relation to non-upwelling periods. The spatial distribution among stations varied according to the temperature with higher abundance in stations with values between 19 and 21ºC. The highest abundance of A. longinaris was recorded in spring and summer when intrusions of the cold waters of South Atlantic Central Waters (SACW were frequent. Thus, the effect of cold water of SACW boosted by the upwelling was a determinant factor in the spatial and temporal distribution of A. longinaris in the studied region.

  8. Evolution to decay of upwelling and associated biogeochemistry over the southeastern Arabian sea shelf

    Digital Repository Service at National Institute of Oceanography (India)

    Gupta, G.V.M.; Sudheesh, V.; Sudharma, K.V.; Saravanane, N.; Dhanya, V.; Dhanya, K.R.; Lakshmi, G.; Sudhakar, M.; Naqvi, S.W.A.

    (SM). By changing an oligotrophic to a nutrient-replete condition, the upwelling is the major process that regulates the biogeochemistry of this shelf. Its onset is perceptible at 100m depth between January and March. The upwelling reaches the surface...

  9. Aerodynamic heating in gaps of thermal protection system tile arrays in laminar and turbulent boundary layers

    Science.gov (United States)

    Avery, D. E.

    1978-01-01

    An experimental heat-transfer investigation was conducted on two staggered arrays of metallic tiles in laminar and turbulent boundary layers. This investigation was conducted for two purposes. The impingement heating distribution where flow in a longitudinal gap intersects a transverse gap and impinges on a downstream blocking tile was defined. The influence of tile and gap geometries was analyzed to develop empirical relationships for impingement heating in laminar and turbulent boundary layers. Tests were conducted in a high temperature structures tunnel at a nominal Mach number of 7, a nominal total temperature of 1800 K, and free-stream unit Reynolds numbers from 1.0 x 10 million to 4.8 x 10 million per meter. The test results were used to assess the impingement heating effects produced by parameters that include gap width, longitudinal gap length, slope of the tile forward-facing wall, boundary-layer displacement thickness, Reynolds number, and local surface pressure.

  10. Entropy criteria applied to pattern selection in systems with free boundaries

    Science.gov (United States)

    Kirkaldy, J. S.

    1985-10-01

    The steady state differential or integral equations which describe patterned dissipative structures, typically to be identified with first order phase transformation morphologies like isothermal pearlites, are invariably degenerate in one or more order parameters (the lamellar spacing in the pearlite case). It is often observed that a different pattern is attained at the steady state for each initial condition (the hysteresis or metastable case). Alternatively, boundary perturbations and internal fluctuations during transition up to, or at the steady state, destroy the path coherence. In this case a statistical ensemble of imperfect patterns often emerges which represents a fluctuating but recognizably patterned and unique average steady state. It is cases like cellular, lamellar pearlite, involving an assembly of individual cell patterns which are regularly perturbed by local fluctuation and growth processes, which concern us here. Such weakly fluctuating nonlinear steady state ensembles can be arranged in a thought experiment so as to evolve as subsystems linking two very large mass-energy reservoirs in isolation. Operating on this discontinuous thermodynamic ideal, Onsager’s principle of maximum path probability for isolated systems, which we interpret as a minimal time correlation function connecting subsystem and baths, identifies the stable steady state at a parametric minimum or maximum (or both) in the dissipation rate. This nonlinear principle is independent of the Principle of Minimum Dissipation which is applicable in the linear regime of irreversible thermodynamics. The statistical argument is equivalent to the weak requirement that the isolated system entropy as a function of time be differentiable to the second order despite the macroscopic pattern fluctuations which occur in the subsystem. This differentiability condition is taken for granted in classical stability theory based on the 2nd Law. The optimal principle as applied to isothermal and

  11. An urban systems framework to assess the trans-boundary food-energy-water nexus: implementation in Delhi, India

    Science.gov (United States)

    Ramaswami, Anu; Boyer, Dana; Singh Nagpure, Ajay; Fang, Andrew; Bogra, Shelly; Bakshi, Bhavik; Cohen, Elliot; Rao-Ghorpade, Ashish

    2017-02-01

    This paper develops a generalizable systems framework to analyze the food-energy-water (FEW) nexus from an urban systems perspective, connecting in- and trans-boundary interactions, quantifying multiple environmental impacts of community-wide FEW provisioning to cities, and visualizing FEW supply-chain risks posed to cities by the environment. Delhi’s community-wide food demand includes household consumption by socio-economic-strata, visitors- and industrial food-use. This demand depends 90%, 76%, and 86% on trans-boundary supply of FEW, respectively. Supply chain data reveal unique features of trans-boundary FEW production regions (e.g. irrigation-electricity needs and GHG intensities of power-plants), yielding supply chain-informed coupled energy-water-GHG footprints of FEW provisioning to Delhi. Agri-food supply contributes to both GHG (19%) and water-footprints (72%–82%) of Delhi’s FEW provisioning, with milk, rice and wheat dominating these footprints. Analysis of FEW interactions within Delhi found >75% in-boundary water-use for food is for urban agriculture and >76% in-boundary energy-use for food is from cooking fuels. Food waste-to-energy and energy-intensity of commercial and industrial food preparation are key data gaps. Visualizing supply chains shows >75% of water embodied in Delhi’s FEW supply is extracted from locations over-drafting ground water. These baseline data enable evaluation of future urban FEW scenarios, comparing impacts of demand shifts, production shifts, and emerging technologies and policies, within and outside of cities.

  12. Boltzmann’s Six-Moment One-Dimensional Nonlinear System Equations with the Maxwell-Auzhan Boundary Conditions

    Directory of Open Access Journals (Sweden)

    A. Sakabekov

    2016-01-01

    Full Text Available We prove existence and uniqueness of the solution of the problem with initial and Maxwell-Auzhan boundary conditions for nonstationary nonlinear one-dimensional Boltzmann’s six-moment system equations in space of functions continuous in time and summable in square by a spatial variable. In order to obtain a priori estimation of the initial and boundary value problem for nonstationary nonlinear one-dimensional Boltzmann’s six-moment system equations we get the integral equality and then use the spherical representation of vector. Then we obtain the initial value problem for Riccati equation. We have managed to obtain a particular solution of this equation in an explicit form.

  13. Differential responses of calcifying and non-calcifying epibionts of a brown macroalga to present-day and future upwelling pCO2.

    Directory of Open Access Journals (Sweden)

    Vincent Saderne

    Full Text Available Seaweeds are key species of the Baltic Sea benthic ecosystems. They are the substratum of numerous fouling epibionts like bryozoans and tubeworms. Several of these epibionts bear calcified structures and could be impacted by the high pCO2 events of the late summer upwellings in the Baltic nearshores. Those events are expected to increase in strength and duration with global change and ocean acidification. If calcifying epibionts are impacted by transient acidification as driven by upwelling events, their increasing prevalence could cause a shift of the fouling communities toward fleshy species. The aim of the present study was to test the sensitivity of selected seaweed macrofoulers to transient elevation of pCO2 in their natural microenvironment, i.e. the boundary layer covering the thallus surface of brown seaweeds. Fragments of the macroalga Fucus serratus bearing an epibiotic community composed of the calcifiers Spirorbis spirorbis (Annelida and Electra pilosa (Bryozoa and the non-calcifier Alcyonidium hirsutum (Bryozoa were maintained for 30 days under three pCO2 conditions: natural 460 ± 59 µatm, present-day upwelling1193 ± 166 µatm and future upwelling 3150 ± 446 µatm. Only the highest pCO2 caused a significant reduction of growth rates and settlement of S. spirorbis individuals. Additionally, S. spirorbis settled juveniles exhibited enhanced calcification of 40% during daylight hours compared to dark hours, possibly reflecting a day-night alternation of an acidification-modulating effect by algal photosynthesis as opposed to an acidification-enhancing effect of algal respiration. E. pilosa colonies showed significantly increased growth rates at intermediate pCO2 (1193 µatm but no response to higher pCO2. No effect of acidification on A. hirsutum colonies growth rates was observed. The results suggest a remarkable resistance of the algal macro-epibionts to levels of acidification occurring at present day upwellings in the Baltic

  14. A numerical investigation of the atmosphere-ocean thermal contrast over the coastal upwelling region of Cabo Frio, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Dourado, M. [Departamento de Meteorologia, Universidade Federal de Pelotas, Pelotas RS (Brazil)]. E-mail: marcelo_dourado@ufpel.edu.br; Pereira de Oliveira, A. [Departamento de Ciencias Atmosfericas, Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, Universidade de Sao Paulo, (Brazil)

    2008-01-15

    An one-dimensional atmospheric second order closure model, coupled to an oceanic mixed layer model, is used to investigate the short term variation of the atmospheric and oceanic boundary layers in the coastal upwelling area of Cabo Frio, Brazil (23 degrees Celsius S, 42 degrees Celsius 08' W). The numerical simulations were carried out to evaluate the impact caused by the thermal contrast between atmosphere and ocean on the vertical extent and other properties of both atmospheric and oceanic boundary layers. The numerical simulations were designed taking as reference the observations carried out during the passage of a cold front that disrupted the upwelling regime in Cabo Frio in July of 1992. The simulations indicated that in 10 hours the mechanical mixing, sustained by a constant background flow of 10 m s-1, increases the atmospheric boundary layer in 214 m when the atmosphere is initially 2 K warmer than the ocean (positive thermal contrast observed during upwelling regime). For an atmosphere initially -2 K colder than the ocean (negative thermal contrast observed during passage of the cold front), the incipient thermal convection intensifies the mechanical mixing increasing the vertical extent of the atmospheric boundary layer in 360 m. The vertical evolution of the atmospheric boundary layer is consistent with the observations carried out in Cabo Frio during upwelling condition. When the upwelling is disrupted, the discrepancy between the simulated and observed atmospheric boundary layer heights in Cabo Frio during July of 1992 increases considerably. During the period of 10 hours, the simulated oceanic mixed layer deepens 2 m and 5.4 m for positive and negative thermal contrasts of 2 K and -2 K, respectively. In the latter case, the larger vertical extent of the oceanic mixed layer is due to the presence of thermal convection in the atmospheric boundary layer, which in turn is associated to the absence of upwelling caused by the passage of cold fronts

  15. On preconditioning techniques for dense linear systems arising from singular boundary integral equations

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Ke [Univ. of Liverpool (United Kingdom)

    1996-12-31

    We study various preconditioning techniques for the iterative solution of boundary integral equations, and aim to provide a theory for a class of sparse preconditioners. Two related ideas are explored here: singularity separation and inverse approximation. Our preliminary conclusion is that singularity separation based preconditioners perform better than approximate inverse based while it is desirable to have both features.

  16. A continuum framework for grain boundary diffusion in thin film/substrate systems

    NARCIS (Netherlands)

    Ayas, Can; van der Giessen, Erik

    2010-01-01

    A two-dimensional continuum model is developed for stress relaxation in thin films through grain boundary (GB) diffusion. When a thin film with columnar grains is subjected to thermal stress, stress gradients along the GBs are relaxed by diffusion of material from the film surface into the GBs. The

  17. Existence of global solutions to free boundary value problems for bipolar Navier-Stokes-Possion systems

    Directory of Open Access Journals (Sweden)

    Jian Liu

    2013-09-01

    Full Text Available In this article, we consider the free boundary value problem for one-dimensional compressible bipolar Navier-Stokes-Possion (BNSP equations with density-dependent viscosities. For general initial data with finite energy and the density connecting with vacuum continuously, we prove the global existence of the weak solution. This extends the previous results for compressible NS [27] to NSP.

  18. An abstract approximate controllability result and applications to elliptic and parabolic systems with dynamic boundary conditions

    Directory of Open Access Journals (Sweden)

    Ioan Bejenaru

    2001-07-01

    Full Text Available In this paper we prove an approximate controllability result for an abstract semilinear evolution equation in a Hilbert space and we obtain as consequences the approximate controllability for some classes of elliptic and parabolic problems subjected to nonlinear, possible non monotone, dynamic boundary conditions.

  19. Dirac structures and boundary control systems associated with skew-symmetric differential operators

    NARCIS (Netherlands)

    Le Gorrec, Y.; Zwart, H.J.; Maschke, B.

    2005-01-01

    Associated with a skew-symmetric linear operator on the spatial domain $[a,b]$ we define a Dirac structure which includes the port variables on the boundary of this spatial domain. This Dirac structure is a subspace of a Hilbert space. Naturally, associated with this Dirac structure is an infinite-d

  20. Dirac structures and boundary control systems associated with skew-symmetric differential operators

    NARCIS (Netherlands)

    Le Gorrec, Y.; Zwart, H.J.; Maschke, B.

    2004-01-01

    Associated with a skew-symmetric linear operator on the spatial domain $[a,b]$ we define a Dirac structure which includes the port variables on the boundary of this spatial domain. This Dirac structure is a subspace of a Hilbert space. Naturally, associated to this Dirac structure is infinite dimen

  1. Global existence and blow-up of solutions to a parabolic system with nonlocal sources and boundaries

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    This paper deals with a semi-linear parabolic system with nonlinear nonlocal sources and nonlocal boundaries.By using super-and sub-solution techniques,we first give the sufficient conditions that the classical solution exists globally and blows up in a finite time respectively,and then give the necessary and sufficient conditions that two components u and v blow up simultaneously.Finally,the uniform blow-up profiles in the interior are presented.

  2. Global existence and blow-up of solutions to a parabolic system with nonlocal sources and boundaries

    Institute of Scientific and Technical Information of China (English)

    Ling-hua KONG; Ming-xin WANG

    2007-01-01

    This paper deals with a semi-linear parabolic system with nonlinear nonlocal sources and nonlocal boundaries. By using super- and sub-solution techniques, we first give the sufficient conditions that the classical solution exists globally and blows up in a finite time respectively, and then give the necessary and sufficient conditions that two components u and v blow up simultaneously. Finally, the uniform blow-up profiles in the interior are presented.

  3. Identification of upwelling areas in the Oman Sea Using Satellite Data

    Science.gov (United States)

    Moradi, Masoud

    2016-07-01

    Satellite-derived sea-surface temperature, TOPEX/POSEIDON (T/P) sea-level anomalies (SLAs), modeled wind data, and hydrodynamic data from World Ocean Database were used to characterize the upwelling along the Oman Sea coasts during 2002 - 2012. Principal Component Analysis (PCA) of the satellite-derived sea-surface temperature (SST) shows the first mode affected by upwelling processes, which represents a biannual variability. In addition, the SST shows the upwelling front moving offshore with the development of Southwest (SW) Monsoon in early June. SST shows the persistence of cold upwelling waters for nearly a month after the end of the SW Monsoon within the bays along the Oman coast. TOPEX/POSEIDON SLAs indicate that with the onset of the SW Monsoon, a 30-cm drop in height is observed along the Oman coast associated the presence of the cool upwelled waters. This drop in height sets up a horizontal pressure gradient and results in a compensating along-shore, northeastward flowing, geostrophic current (East Arabian Current) during the SW Monsoon. Similarly, the altimeter data slow an offshore decrease in height during the Northeast (NE) Monsoon, indicating a seasonal reversal in direction of the East Oman Currents with flow to the southwest. The following upwelling characteristics are identified for the Oman upwelling zone: 1- Upwelling zones have seen along Oman and Pakistan coasts and in the western coasts, like Iran, persistent upwelling zones are not available. 2- Upwelling zones along Oman coasts are more persistent and developed than in Pakistan coastal area. 3- Upwelling in the Oman and East Pakistan coasts starts with SW-Monsoon and will developed in the mid-August, adjusted with summer cooling. 4- Along Oman Sea, upwelling zones were developed between Rasal-Haddad and the southern bay. Mean SST during SW-Monsoon is about 22 °C. 5-Waters with temperature about 23°C were upwelled from depth 50-75 m along Oman coasts, and about 50 m along Pakistan coasts. 6

  4. The EarthScope Plate Boundary Observatory Distributed Data Management System

    Science.gov (United States)

    Anderson, G.; Eakins, J.; Hodgkinson, K.; Matykiewicz, J.; Beldyk, M.; Blackman, B.; Boler, F.; Henderson, B.; Hoyt, B.; Lee, E.; Persson, E.; Smith, J.; Torrez, D.; Wright, J.; Jackson, M.; Meertens, C.

    2007-05-01

    EarthScope is an ambitious multi-year project funded by the United States National Science Foundation to explore the structure and dynamics of the North American continent using a wide range of geophysical methods. The Plate Boundary Observatory (PBO), being built by UNAVCO, is the geodetic component of EarthScope, and will comprise 880 continuous GPS stations, 103 borehole strainmeter stations, 28 tiltmeters, and five laser strainmeters; in addition, PBO will manage data for 209 existing GPS stations and 11 GPS stations installed by the USArray segment of EarthScope. As of February 2007, 561 of these stations have been installed. PBO data flow is managed from the PBO Boulder Network Operations Center (NOC), located at UNAVCO Headquarters. Automated systems at the NOC retrieve data from our stations at least daily, monitor the status of the network and alert operators to problems, and pass data on for analysis, archiving, and distribution. Real-time network status can be found at http:pboweb.unavco.org/soh_map. PBO's analysis centers generate high-quality derived data products from PBO raw data. Two centers, at Central Washington University and the New Mexico Institute of Mining and Technology, process raw GPS data to produce initial PBO GPS products including network solutions and station position time series, andthese products are combined by the Analysis Center Coordinator at MIT to produce the official PBO GPS products. Two analysis centers, at UNAVCO's Socorro office and the University of California, San Diego, process data from the PBO borehole and laser strainmeter networks and produce cleaned time series of shear, areal, and linear strain, Earth tides, pore fluid pressure, and other parameters. The UNAVCO Facility archives and distributes all PBO GPS data products and runs a secondary archive offsite; to date, these centers hold more than 2.5 TB of PBO products. The IRIS Data Management Center and Northern California Earthquake Data Center archive and

  5. The Mono Arch, eastern Sierra region, California: Dynamic topography associated with upper-mantle upwelling?

    Science.gov (United States)

    Jayko, A.S.

    2009-01-01

    A broad, topographic flexure localized east of and over the central and southern Sierra Nevada, herein named the Mono Arch, apparently represents crustal response to lithospheric and/or upper-mantle processes, probably dominated by mantle upwelling within the continental interior associated Pacific-North American plate-boundary deformation. This zone of flexure is identified through comparison between the topographic characteristics of the active Cascade volcanic arc and backarc regions with the analogous former arc and backarc in the Sierra Nevada and eastern Sierra Nevada. Serial topographic profiles measured normal to the modern Cascade backarc reveal an accordance of topographic lows defined by valley floors with an average minimum elevation of ???1400-1500m for over 175km to the southeast. Although the accordance drops in elevation slightly to the south, the modern Cascade backarc region is remarkably level, and is characterized by relief up to ???750m above this baseline elevation. By contrast, serial topographic profiles over the former arc and backarc transitions of the eastern Sierra region exhibit a regional anticlinal warping defined by accordant valley floors and by a late Miocene-early Pliocene erosion surface and associated deposits. The amplitude of this flexure above regionally flat baseline elevations to the east varies spatially along the length of the former Sierran arc, with a maximum of ???1000m centred over the Bridgeport Basin. The total zone of flexure is approximately 350km long N-S and 100km wide E-W, and extends from Indian Wells Valley in the south to the Sonora Pass region in the north. Previous geophysical, petrologic, and geodetic studies suggest that the Mono Arch overlies a zone of active mantle upwelling. This region also represents a zone crustal weakness formerly exploited by the middle-to-late Miocene arc and is presently the locus of seismic and volcanic activities. This seismic zone, which lies east of the Sierra Nevada block

  6. Interpretation of horizontal well performance in complicated systems by the boundary element method

    Energy Technology Data Exchange (ETDEWEB)

    Jongkittinarukorn, K.; Tiab, D. [Oklahoma Univ., School of Petroleum and Geological Engineering (United States); Escobar, F. H. [Surcolombiana Univ., Dept. of Petroleum Engineering (Colombia)

    1998-12-31

    A solution obtained by using the boundary element method to simulate pressure behaviour of horizontal wells in complicated reservoir-wellbore configurations is presented. Three different types of well bore and reservoir models were studied, i.e. a snake-shaped horizontal wellbore intersecting a two-layer reservoir with cross flow, a horizontal well in a three-layer reservoir with cross flow, and a vertical well intersecting a two-layer reservoir without cross flow. In each case, special attention was paid to the influence of wellbore inclination angle, the distance from the wellbore to the different boundaries and the permeability ratio. Performance of each of these types of wells are discussed. 9 refs., 18 figs.

  7. Flow patterns and boundary conditions for inlet and outlet conduits of large pump system with low head

    Institute of Scientific and Technical Information of China (English)

    徐磊; 陆伟刚; 陆林广; 董雷; 王兆飞

    2014-01-01

    The flow patterns in the inlet and outlet conduits have a decisive effect on the safe, stable, and highly efficient operation of the pump in a large pumping station with low head. The numerical simulation of three-dimensional (3D) turbulence flow in conduits is an important method to study the hydraulic performance and conduct an optimum hydraulic design for the conduits. With the analyses of the flow patterns in the inlet and outlet conduits, the boundary conditions of the numerical simulation for them can be determined. The main obtained conclusions are as follows: (i) Under normal operation conditions, there is essentially no pre-swirl flow at the impeller chamber inlet of an axial-flow pump system, based on which the boundary condition at the inlet conduit may be defined. (ii) The circulation at the guide vane outlet of an axial-flow pump system has a great effect on the hydraulic performance of the outlet conduit, and there is optimum circulation for the performance. Therefore, it is strongly suggested to design the guide vane according to the optimum circulation. (iii) The residual circulation at the guide vane outlet needs to be considered for the inlet boundary condition of the outlet conduit, and the value of the circulation may be measured in a specially designed test model.

  8. LOTOS: A Proposed Lower Tropospheric Observing System from the Land Surface through the Atmospheric Boundary Layer

    Science.gov (United States)

    Cohn, S. A.; Lee, W. C.; Carbone, R. E.; Oncley, S.; Brown, W. O. J.; Spuler, S.; Horst, T. W.

    2015-12-01

    Advances in sensor capabilities, but also in electronics, optics, RF communication, and off-the-grid power are enabling new measurement paradigms. NCAR's Earth Observing Laboratory (EOL) is considering new sensors, new deployment modes, and integrated observing strategies to address challenges in understanding within the atmospheric boundary layer and the underlying coupling to the land surface. Our vision is of a network of deployable observing sites, each with a suite of complementary instruments that measure surface-atmosphere exchange, and the state and evolution of the boundary layer. EOL has made good progress on distributed surface energy balance and flux stations, and on boundary layer remote sensing of wind and water vapor, all suitable for deployments of combined instruments and as network of such sites. We will present the status of the CentNet surface network development, the 449-MHz modular wind profiler, and a water vapor and temperature profiling differential absorption lidar (DIAL) under development. We will further present a concept for a test bed to better understand the value of these and other possible instruments in forming an instrument suite flexible for multiple research purposes.

  9. Random walks in the quarter plane algebraic methods, boundary value problems, applications to queueing systems and analytic combinatorics

    CERN Document Server

    Fayolle, Guy; Malyshev, Vadim

    2017-01-01

    This monograph aims to promote original mathematical methods to determine the invariant measure of two-dimensional random walks in domains with boundaries. Such processes arise in numerous applications and are of interest in several areas of mathematical research, such as Stochastic Networks, Analytic Combinatorics, and Quantum Physics. This second edition consists of two parts. Part I is a revised upgrade of the first edition (1999), with additional recent results on the group of a random walk. The theoretical approach given therein has been developed by the authors since the early 1970s. By using Complex Function Theory, Boundary Value Problems, Riemann Surfaces, and Galois Theory, completely new methods are proposed for solving functional equations of two complex variables, which can also be applied to characterize the Transient Behavior of the walks, as well as to find explicit solutions to the one-dimensional Quantum Three-Body Problem, or to tackle a new class of Integrable Systems. Part II borrows spec...

  10. Long-term trends of upwelling and impacts on primary productivity in the Alaskan Beaufort Sea

    Science.gov (United States)

    Pickart, Robert S.; Schulze, Lena M.; Moore, G. W. K.; Charette, Matthew A.; Arrigo, Kevin R.; van Dijken, Gert; Danielson, Seth L.

    2013-09-01

    Using a previously established wind proxy for upwelling along the North Slope of Alaska, we examine the interannual to decadal variability in upwelling as well as the climatological monthly trends. The ability of the upwelling to trigger phytoplankton blooms via upward nitrate flux from the halocline is then investigated using data from a moored array together with the proxy. The 70-year record of wind speed from the Barrow, Alaska meteorological station (1941-2010) reveals that strong upwelling events - lasting at least 4 days and exceeding 10 m/s during the storm - occur throughout the year. On average there are 9-10 upwelling events per year, and the number and strength of events has increased over the last 25 years. The low-frequency variability in the upwelling co-varies with previously documented Arctic climate trends, but there is no significant correlation with various high latitude atmospheric indices. There are two seasonal peaks in the occurrence of upwelling, in May and November. The role of the Beaufort High and Aleutian Low in driving the upwelling is investigated using NCEP reanalysis fields. Fluctuations in both of these centers of action contribute to the enhanced winds, and the location of the Aleutian Low storm track plays a key role in the seasonal variability of the upwelling. The upward nitrate flux due to storms in the open water period can account for new primary production that is on par with carbon fixed during the summer growing season in the absence of storms. Evidence from satellite ocean color data of such wind-induced phytoplankton blooms is presented.

  11. DETERMINATION OF EFFICIENCY INDICES PERTAINING TO DEVELOPMENT AND OPERATION OF TRANS-BOUNDARY TRANSPORT AND LOGISTICS SYSTEM

    Directory of Open Access Journals (Sweden)

    Y. A. Kopko

    2011-01-01

    Full Text Available An investigation of the system efficiency requires a special approach in terms of its level, content and interrelations with an external environment. In this regard logistic  systems are rather complicated that consist of a number of service sub-systems and designed at various levels.  Such system complexity requires a development of an efficient mechanism for its design and operation of objects of the trans-boundary transport logistics. The efficiency of the trans-boundary transport and logistic systems (TTLS can be described by a number of cost and physical indicators reflecting both market and traditional approaches. The TTLS have their own peculiar features concerning determination of efficiency that are related with the state regulation set of processes occurring  at border crossings. In order to assess the current operational process it is necessary to apply an index system which pays a special attention to a transport capability due to the TTLS specificity. While planning a custom automotive processing at a border checkpoint there is no need to aspire for an immediate passage of all vehicles by all means. The basic requirement is to maintain a transport capability in the operational zone. Thus an irregularity of incoming vehicles at border crossing points is smoothed out by regulating priorities pertaining to requirements of custom processing while using an urgency function of cargo transportation thereby ensuring an optimal operation of a customs post.

  12. Design of optical systems using derivatives of rays: derivatives of variable vector of spherical boundary surfaces with respect to system variable vector.

    Science.gov (United States)

    Lin, Psang Dain

    2013-10-20

    A computational scheme based on differential geometry was proposed in a previous study [Appl. Opt.52, 4151 (2013)] for determining the first- and second-order derivative matrices of a skew ray reflected/refracted at a flat boundary surface. The present study extends this methodology to the case of a skew ray reflected/refracted at a spherical boundary surface. The validity of the proposed approach is demonstrated using two retro-reflectors for illustration purposes. The results show that the proposed method provides an effective means of determining the search direction required to minimize the merit function during the optimization stage of the optical system design process.

  13. Biological and oceanographic upwelling indicators at Cabo Frio (RJ

    Directory of Open Access Journals (Sweden)

    Gleyci A. O. Moser

    1997-01-01

    Full Text Available Phytoplankton biomass, chemical parameters and hydrology were studied in a transect 101.6 km long off Cabo Frio (RJ, Southeast Brazil, during summer (December 29 to 31, 1991 and winter (June 27 to 30, 1992. Wind induced upwelling events are frequently observed in the area during summer, becoming rare during winter. By the summer cruise a bloom of phytoplankton was observed in surface, close to the coast, with chlorophyll concentrations reaching 25.55 mg Chl-a m-3, uncoupled from the cold, nutrient rich waters of South Atlantic Central Water (SACW, found below 40 m depth. During the winter cruise, the SACW raised at the surface waters in front of Cabo Frio depicting an upwelling event. However, in spite of high surface nitrate concentrations (up to 7.7 f.1M chlorophyll-a were lower than 2 mg Chl-a m-3. The phytoplankton biomass, meteorological and hydrological data suggest a probable upwelling event immediately before the summer cruise, and an ongoing one during winter time. Cluster analyses and principal component analyses (PCA were applied to summer and winter data, pointing out multidimensional fronts in the area during both seasons.A biomassa fitoplanctônica, parâmetros químicos e hidrologia foram estudadas em um transecto de 101,6 Km ao largo de Cabo Frio, (RJ Brasil, durante o verão (Dezembro 29 a 31, 1991 e inverno (Junho 27 a 30, 1992. Nesta área, eventos de ressurgência induzidos pelo vento são comuns durante o verão, tornando-se mais raros durante o inverno. Durante o período de verão uma floração de fitoplâncton foi observada na superfície próximo ao continente, apresentando um máximo de clorofila-a igual a 25,55 mg Cl-a m'3 desacoplado das águas frias e ricas em nutrientes da Água Central do Atlântico Sul (ACAS, presente abaixo de 40 m. Durante o inverno, a ACAS alcançou a superflcie em frente a Cabo Frio, caracterizando um evento de ressurgência. Entretanto, apesar das altas concentrações de nitrato na superf

  14. Dissipative boundary conditions for 2 × 2 hyperbolic systems of conservation laws for entropy solutions in BV

    Science.gov (United States)

    Coron, Jean-Michel; Ervedoza, Sylvain; Ghoshal, Shyam Sundar; Glass, Olivier; Perrollaz, Vincent

    2017-01-01

    In this article, we investigate the BV stability of 2 × 2 hyperbolic systems of conservation laws with strictly positive velocities under dissipative boundary conditions. More precisely, we derive sufficient conditions guaranteeing the exponential stability of the system under consideration for entropy solutions in BV. Our proof is based on a front tracking algorithm used to construct approximate piecewise constants solutions whose BV norms are controlled through a Lyapunov functional. This Lyapunov functional is inspired by the one proposed in J. Glimm's seminal work [16], modified with some suitable weights in the spirit of the previous works [9,10].

  15. Corona Formation and Heat Loss on Venus by Coupled Upwelling and Delamination

    Science.gov (United States)

    Smrekar, Suzanne E.; Stofan, Ellen R.

    1997-01-01

    Coronae are volcanotectonic features that are unique to Venus and are interpreted to be small-scale upwellings. A model in which upwelling causes delamination at the edge of the plume head, along with deformation of a pre-existing depleted mantel Layer, can produce the full range of topographic forms of coronae. If half of the coronae are active, delamination of the lower lithosphere could account for about 10% of venus's heat loss, with another 15% due to upwelling. Delamination may occur in other geologic enviroment and could help account for 'Venus' heat loss 'deficit'.

  16. Metagenomes of the picoalga Bathycoccus from the Chile coastal upwelling.

    Directory of Open Access Journals (Sweden)

    Daniel Vaulot

    Full Text Available Among small photosynthetic eukaryotes that play a key role in oceanic food webs, picoplanktonic Mamiellophyceae such as Bathycoccus, Micromonas, and Ostreococcus are particularly important in coastal regions. By using a combination of cell sorting by flow cytometry, whole genome amplification (WGA, and 454 pyrosequencing, we obtained metagenomic data for two natural picophytoplankton populations from the coastal upwelling waters off central Chile. About 60% of the reads of each sample could be mapped to the genome of Bathycoccus strain from the Mediterranean Sea (RCC1105, representing a total of 9 Mbp (sample T142 and 13 Mbp (sample T149 of non-redundant Bathycoccus genome sequences. WGA did not amplify all regions uniformly, resulting in unequal coverage along a given chromosome and between chromosomes. The identity at the DNA level between the metagenomes and the cultured genome was very high (96.3% identical bases for the three larger chromosomes over a 360 kbp alignment. At least two to three different genotypes seemed to be present in each natural sample based on read mapping to Bathycoccus RCC1105 genome.

  17. Controlled artificial upwelling in a fjord to combat toxic algae

    Science.gov (United States)

    McClimans, T. A.; Hansen, A. H.; Fredheim, A.; Lien, E.; Reitan, K. I.

    2003-04-01

    During the summer, primary production in the surface layers of some fjords depletes the nutrients to the degree that some arts of toxic algae dominate the flora. We describe an experiment employing a bubble curtain to lift significant amounts of nutrient-rich seawater to the light zone and provide an environment in which useful algae can survive. The motivation for the experiment is to provide a local region in which mussels can be cleansed from the effects of toxic algae. Three 100-m long, perforated pipes were suspended at 40 m depth in the Arnafjord, a side arm of the Sognefjord. Large amounts of compressed air were supplied during a period of three weeks. The deeper water mixed with the surface water and flowed from the mixing region at 5 to 15 m depth. Within a few days, the mixture of nutrient-rich water covered most of the inner portion of Arnafjord. Within 10 days, the plankton samples showed that the artificial upwelling produced the desired type of algae and excluded the toxic blooms that were occurring outside the manipulated fjord arm. The project (DETOX) is supported by the Norwegian ministries of Fisheries, Agriculture and Public Administration.

  18. Proposed Auxiliary Boundary Stratigraphic Section and Point (ASSP) for the base of the Ordovician System at Lawson Cove, Utah, USA

    Science.gov (United States)

    Miller, James F.; Evans, Kevin R.; Ethington, Raymond L.; Freeman, Rebecca; Loch, James D.; Repetski, John E.; Ripperdan, Robert; Taylor, John F.

    2016-01-01

    The Global boundary Stratotype Section and Point (GSSP) for the base of the Ordovician System is at the First Appearance Datum (FAD) of the conodont Iapetognathus fluctivagus at Green Point in Newfoundland, Canada. Strata there are typical graptolitic facies that were deposited near the base of the continental slope.We propose establishing an Auxiliary boundary Stratotype Section and Point (ASSP) at the FAD of I. fluctivagus at the Lawson Cove section in the Ibex area of Millard County, Utah, USA. There, strata consist of typical shelly facies limestones that were deposited on a tropical carbonate platform and contain abundant conodonts, trilobites, brachiopods, and other fossil groups. Cambrian and Ordovician strata in this area are ~5300m thick, with the Lawson Cove section spanning 243m in three overlapping segments. Six other measured and studied sections in the area show stratigraphic relationships similar to those at Lawson Cove. Faunas have been used to divide these strata into 14 conodont and 7 trilobite zonal units. The widespread olenid trilobite Jujuyaspis occurs ~90cm above the proposed boundary at Lawson Cove; this genus is generally regarded as earliest Ordovician. Rhynchonelliform and linguliform brachiopods are common to abundant and are useful for correlation. The FAD of Iapetognathus fluctivagus and occurrences of Jujuyaspis and the Lower Ordovician planktonic graptolite Anisograptus matanensis all occur within a 2.4m interval of strata at a nearby section. Non-biological correlation tools include a detailed sequence stratigraphic classification and a detailed carbon-isotope profile. Especially useful for correlation is a positive 13C excursion peak ~15cm below the proposed boundary horizon. All of these correlation tools form an integrated framework that makes the Lawson Cove section especially useful as an ASSP for global correlation of strata with faunas typical of shallow, warm-water, shelly facies.

  19. A theory of the infinite horizon LQ-problem for composite systems of PDEs with boundary control

    CERN Document Server

    Acquistapace, Paolo; Lasiecka, Irena

    2012-01-01

    We study the infinite horizon Linear-Quadratic problem and the associated algebraic Riccati equations for systems with unbounded control actions. The operator-theoretic context is motivated by composite systems of Partial Differential Equations (PDE) with boundary or point control. Specific focus is placed on systems of coupled hyperbolic/parabolic PDE with an overall `predominant' hyperbolic character, such as, e.g., some models for thermoelastic or fluid-structure interactions. While unbounded control actions lead to Riccati equations with unbounded (operator) coefficients, unlike the parabolic case solvability of these equations becomes a major issue, owing to the lack of sufficient regularity of the solutions to the composite dynamics. In the present case, even the more general theory appealing to estimates of the singularity displayed by the kernel which occurs in the integral representation of the solution to the control system fails. A novel framework which embodies possible hyperbolic components of th...

  20. Observed anomalous upwelling in the Lakshadweep Sea during the summer monsoon season of 2005

    Digital Repository Service at National Institute of Oceanography (India)

    Gopalakrishna, V.V.; Rao, R.R.; Nisha, K.; GirishKumar, M.S.; Pankajakshan, T.; Ravichandran, M.; Johnson, Z.; Girish, K.; Aneeshkumar, N.; Srinath, M.; Rajesh, S.; Rajan, C.K.

    of local and remote forcings are examined to explain the observed anomalous upwelling during SMS of 2005. The equatorward alongshore wind stress (WS) along the KK XBT transect persisted in a transient manner beyond September only during SMS of 2005...

  1. Observational evidence of upwelling off the southwest coast of India during June-July 2006

    Digital Repository Service at National Institute of Oceanography (India)

    Lekshmi, S.; Smitha, B.R.; Revichandran, C.

    Considerable latitudinal variability exists in the forcing mechanisms and intensity of coastal upwelling along the southwest coast of India. Present work is based on the insitu observations conducted onboard FORV Sagar Sampada for 12 days along two...

  2. Upwelling variability along the southern coast of Bali and in Nusa Tenggara waters

    Science.gov (United States)

    Ningsih, Nining Sari; Rakhmaputeri, Noviani; Harto, Agung B.

    2013-03-01

    Spatial and temporal variation of upwelling along the southern coast of Bali and in the Nusa Tenggara waters — Indonesia was studied by using satellite image data of sea surface temperatures and chlorophyll-a from September 1997 to December 2008. This study clearly reveals annual upwelling in the regions from June to October, associated with the southeast monsoon cycle, with the sea surface temperature (chlorophyll-a concentration) being colder (higher) than that during the northwest monsoon. In addition, this study also shows that the upwelling strength is controlled remotely by ENSO and IOD climate phenomena. During El Niño/positive IOD (La Niña/negative IOD) periods, the Bali — Nusa Tenggara upwelling strength increases (decreases).

  3. Ekman Upwelling, METOP ASCAT, 0.25 degrees, Global, Near Real Time

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  4. On an upwelling front along the west coast of India during later part of southwest monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Unnikrishnan, A.S.; Antony, M.K.

    A coastal front, associated with upwelling, is identified from the observed thermal field along the west coast of India during September, 1987. The front, which is seen very clearly upto a depth of about 75 m, has a horizontal gradient...

  5. Upwelling and associated hydrography along the west coast of india during southwest monsoon, 1999

    Digital Repository Service at National Institute of Oceanography (India)

    Maheswaran, P.A.; Rajesh, G.; Revichandran, C.; Nair, K.K.C.

    ) and 1.2 degrees C (off Mangalore) from the farthest stations, indicating the presence of upwelled water near the coast. Well defined thermal, saline and density fronts were visible. Relatively high offshore transport was observed off Kanyakumari...

  6. Ekman Upwelling, QuikSCAT SeaWinds, 0.25 degrees, Global, Science Quality

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes science quality Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  7. The Solution of Two-Point Boundary Value Problem of a Class of Duffing-Type Systems with Non-C1 Perturbation Term

    Directory of Open Access Journals (Sweden)

    Jiang Zhengxian

    2009-01-01

    Full Text Available This paper deals with a two-point boundary value problem of a class of Duffing-type systems with non-C1 perturbation term. Several existence and uniqueness theorems were presented.

  8. Upwelling Dynamics off Monterey Bay: Heat Flux and Temperature Variability, and their Sensitivities

    Science.gov (United States)

    2010-05-01

    Jamieson and the other donors to the Paul E. Gray Endowed Fund for UROP. 5 Table of contents Acknowledgements...viscous stress. In the surface Ekman layer, as the result of these stresses, the net transport is 90 degrees to the right of the wind in the northern...upward fluid motions). Upwelling can also occur in non-coastal areas. Equatorial upwelling occurs due to the opposite directions of Ekman drift

  9. Practical limitations on the use of diurnal temperature signals to quantify groundwater upwelling

    Science.gov (United States)

    Briggs, Martin; Lautz, Laura K.; Buckley, Sean F.; Lane, Jr., John W.

    2014-01-01

    Groundwater upwelling to streams creates unique habitat by influencing stream water quality and temperature; upwelling zones also serve as vectors for contamination when groundwater is degraded. Temperature time series data acquired along vertical profiles in the streambed have been applied to simple analytical models to determine rates of vertical fluid flux. These models are based on the downward propagation characteristics (amplitude attenuation and phase-lag) of the surface diurnal signal. Despite the popularity of these models, there are few published characterizations of moderate-to-strong upwelling. We attribute this limitation to the thermodynamics of upwelling, under which the downward conductive signal transport from the streambed interface occurs opposite the upward advective fluid flux. Governing equations describing the advection–diffusion of heat within the streambed predict that under upwelling conditions, signal amplitude attenuation will increase, but, counterintuitively, phase-lag will decrease. Therefore the extinction (measurable) depth of the diurnal signal is very shallow, but phase lag is also short, yielding low signal to noise ratio and poor model sensitivity. Conversely, amplitude attenuation over similar sensor spacing is strong, yielding greater potential model sensitivity. Here we present streambed thermal time series over a range of moderate to strong upwelling sites in the Quashnet River, Cape Cod, Massachusetts. The predicted inverse relationship between phase-lag and rate of upwelling was observed in the field data over a range of conditions, but the observed phase-lags were consistently shorter than predicted. Analytical solutions for fluid flux based on signal amplitude attenuation return results consistent with numerical models and physical seepage meters, but the phase-lag analytical model results are generally unreasonable. Through numerical modeling we explore reasons why phase-lag may have been over-predicted by the

  10. Global Existence and Blow-up of Solutions for Parabolic Systems Involving Cross-Diffusions and Nonlinear Boundary Conditions

    Institute of Scientific and Technical Information of China (English)

    Xiu Hui YANG; Fu Cai LI; Chun Hong XIE

    2005-01-01

    In this paper, we investigate the positive solutions of strongly coupled nonlinear parabolic systems with nonlinear boundary conditions:({ut-α(u,v)△u=g(u,v),vt-b(u,v)△v=h(u,v),(e)u/(e)(g)=d(u,v),(e)u/(e)(g)=f(u,v),)Under appropriate hypotheses on the functions a, b, g, h, d and f, we obtain that the solutions may exist globally or blow up in finite time by utilizing upper and lower solution techniques.

  11. Extended cubic B-spline method for solving a linear system of second-order boundary value problems.

    Science.gov (United States)

    Heilat, Ahmed Salem; Hamid, Nur Nadiah Abd; Ismail, Ahmad Izani Md

    2016-01-01

    A method based on extended cubic B-spline is proposed to solve a linear system of second-order boundary value problems. In this method, two free parameters, [Formula: see text] and [Formula: see text], play an important role in producing accurate results. Optimization of these parameters are carried out and the truncation error is calculated. This method is tested on three examples. The examples suggest that this method produces comparable or more accurate results than cubic B-spline and some other methods.

  12. Wind-driven upwelling effects on cephalopod paralarvae: Octopus vulgaris and Loliginidae off the Galician coast (NE Atlantic)

    Science.gov (United States)

    Otero, Jaime; Álvarez-Salgado, X. Antón; González, Ángel F.; Souto, Carlos; Gilcoto, Miguel; Guerra, Ángel

    2016-02-01

    Circulation patterns of coastal upwelling areas may have central consequences for the abundance and cross-shelf transport of the larval stages of many species. Previous studies have provided evidences that larvae distribution results from a combination of subtidal circulation, species-specific behaviour and larval sources. However, most of these works were conducted on organisms characterised by small-sized and abundant early life phases. Here, we studied the influence of the hydrography and circulation of the Ría de Vigo and adjacent shelf (NW Iberian upwelling system) on the paralarval abundance of two contrasting cephalopods, the benthic common octopus (Octopus vulgaris) and the pelagic squids (Loliginidae). We sampled repeatedly a cross-shore transect during the years 2003-2005 and used zero inflated models to accommodate the scarcity and patchy distribution of cephalopod paralarvae. The probability of catching early stages of both cephalopods was higher at night. Octopus paralarvae were more abundant in the surface layer at night whereas loliginids preferred the bottom layer regardless of the sampling time. Abundance of both cephalopods increased when shelf currents flowed polewards, water temperature was high and water column stability was low. The probability of observing an excess of zero catches decreased during the year for octopus and at high current speed for loliginids. In addition, the circulation pattern conditioned the body size distribution of both paralarvae; while the average size of the captured octopuses increased (decreased) with poleward currents at daylight (nighttime), squids were smaller with poleward currents regardless of the sampling time. These results contribute to the understanding of the effects that the hydrography and subtidal circulation of a coastal upwelling have on the fate of cephalopod early life stages.

  13. KPP reaction-diffusion systems with loss inside a cylinder: convergence toward the problem with Robin boundary conditions

    CERN Document Server

    Giletti, Thomas

    2010-01-01

    We consider in this paper a reaction-diffusion system under a KPP hypothesis in a cylindrical domain in the presence of a shear flow. Such systems arise in predator-prey models as well as in combustion models with heat losses. Similarly to the single equation case, the existence of a minimal speed c* and of traveling front solutions for every speed c > c* has been shown both in the cases of heat losses distributed inside the domain or on the boundary. Here, we deal with the accordance between the two models by choosing heat losses inside the domain which tend to a Dirac mass located on the boundary. First, using the characterizations of the corresponding minimal speeds, we will see that they converge to the minimal speed of the limiting problem. Then, we will take interest in the convergence of the traveling front solutions of our reaction-di?usion systems. We will show the convergence under some assumptions on those solutions, which in particular can be satis?ed in dimension 2.

  14. Dynamics of wind-driven upwelling off the northeastern coast of Hainan Island

    Science.gov (United States)

    Lin, Peigen; Cheng, Peng; Gan, Jianping; Hu, Jianyu

    2016-02-01

    Both observational and reanalysis sea surface temperature data reveal that upwelling occurs frequently off the northeastern coast of Hainan Island (downstream of the change in topography off Tongluo Cape), which cannot be attributed to the along-shelf wind alone. To identify dynamics of the upwelling, we conduct a numerical experiment using an idealized topography that is simplified from the actual topography off the eastern and northeastern coasts of Hainan Island. The result indicates that the upwelling downstream of the change in topography is associated with onshore cross-isobath transport. Analysis of the vertically integrated momentum balance shows that the upwelling-linked onshore transport is primarily intensified by the along-isobath barotropic pressure gradient force (PGT), but is weakened by the along-isobath baroclinic pressure gradient force (PGC). The along-isobath PGT is linked to the advection of relative vorticity, the bottom stress curl and the gradient of momentum flux in vorticity equation. On the other hand, the PGC-related process is diagnosed by potential vorticity (PV) balance. Similar to the negative PV term from wind stress, the negative PV terms of the joint effect of baroclinicity and relief and the baroclinic bottom pressure torque weaken the upwelling-linked onshore transport downstream of the change in topography. The onshore transport is enhanced by the positive PV from bottom stress. In addition, the cross-isobath forces play an important role in upwelling intensification in the shallow nearshore region.

  15. Potential new production in two upwelling regions of the western Arabian Sea: Estimation and comparison

    Science.gov (United States)

    Liao, Xiaomei; Zhan, Haigang; Du, Yan

    2016-07-01

    Using satellite-derived and in situ data, the wind-driven potential new production (nitrate supply) for the 300 km wide coastal band in two upwelling regions of the western Arabian Sea (AS) during the southwest monsoon is estimated. The upward nitrate flux to the euphotic zone is generally based on the physical processes of coastal transport (Ekman transport and geostrophic transport) and offshore Ekman pumping. The coastal geostrophic current in the western AS influences the upwelling intensity and latitudinal distributions of nitrate supply. The Oman and Somalia upwelling regions have similar level of potential new production (nitrate supply) during the summer monsoon, while the satellite estimates of primary production off Oman are 2 times greater than those off Somalia. The much higher potential f-ratio in the Somalia upwelling region indicates that the primary production could be limited by availability of other macronutrients (e.g., silicate). The correlation analysis of the primary production and the aerosol optical thickness shows that the Oman upwelling region displays a stronger coupling between the atmospheric deposition and the phytoplankton abundance. The high summertime dust levels in the atmosphere are suggested to contribute to the high primary production in the Oman upwelling region.

  16. Growth of the Humboldt Current krill in the upwelling zone off central Chile

    Science.gov (United States)

    Riquelme-Bugueño, Ramiro; Silva-Aburto, Jocelyn; Escribano, Rubén; Peterson, William T.; Schneider, Wolfgang

    2016-11-01

    Temporal variability in the daily growth rate (DGR) of the Humboldt Current krill, Euphausia mucronata, was studied in eighteen incubation experiments off the coast of Dichato, central Chile (36.5°S), carried out in 2011-2014. Intermolt period (IMP) was derived from the molting rate method in order to estimate the DGRs. Mean IMP was 9.2 ± 4.8 days (range: 2.9-18.7 d). Overall mean DGR was 0.03 ± 0.13 mm d- 1. DGR showed a dome-shaped pattern, with a higher mean DGR when upwelling was moderate (0.06 ± 0.04 mm d- 1) than intense (0.01 ± 0.00 mm d- 1) or weak (0.01 ± - 0.01 mm d- 1). This dome-shaped trend was observed in chlorophyll-a concentrations (Chla) at similar upwelling regimens. E. mucronata DGR variability was best explained by a generalized linear model which included the contribution of the Equatorial Subsurface Water, temperature, dissolved oxygen and Chla as predictor variables. Results suggest that E. mucronata is better adapted to grow under upwelling conditions when it can take advantage of high biological productivity, although the species growth is not limited when weak upwelling or even downwelling occurs. Analysis of the duration of the upwelling events suggest that E. mucronata growth is limited (shrinking) when upwellings last > 10 days.

  17. Trends in coastal upwelling intensity during the late 20th century

    Directory of Open Access Journals (Sweden)

    N. Narayan

    2010-09-01

    Full Text Available This study presents linear trends of coastal upwelling intensity in the later part of the 20th century (1960–2001 employing various indices of upwelling, derived from meridional wind stress and sea surface temperature. The analysis was conducted in the four major coastal upwelling regions in the world, which are off North-West Africa, Lüderitz, California and Peru. The trends in meridional wind stress showed a steady increase of intensity from 1960–2001, which was also reflected in the SST index calculated for the same time period. The steady cooling observed in the instrumental records of SST off California substantiated this observation further. It was also noted that the trends in meridional wind stress obtained from different datasets differ substantially from each other. Correlation analysis showed that basin-scale oscillations like the Atlantic Multidecadal Oscillation (AMO and the Pacific Decadal Oscillation (PDO could not be directly linked to the observed increase of upwelling intensity off NW Africa and California respectively. The relationship of the North Atlantic Oscillation (NAO with coastal upwelling off NW Africa turned out to be ambiguous due to a negative correlation between the NAO index and the meridional wind stress and a lack of correlation with the SST index. Our results give additional support to the hypothesis that the coastal upwelling intensity increases globally because of raising greenhouse gas concentrations in the atmosphere and an associated increase of the land-sea pressure gradient and meridional wind stress.

  18. Winter coastal upwelling off northwest Borneo in the South China Sea

    Institute of Scientific and Technical Information of China (English)

    YAN Yunwei; LING Zheng; CHEN Changlin

    2015-01-01

    Winter coastal upwelling off northwest Borneo in the South China Sea (SCS) is investigated by using satellite data, climatological temperature and salinity fields and reanalysis data. The upwelling forms in Decem-ber, matures in January, starts to decay in February and almost disappears in March. Both Ekman trans-port induced by the alongshore winter monsoon and Ekman pumping due to orographic wind stress curl are favorable for the upwelling. Transport estimates demonstrate that the month-to-month variability of Ekman transport and Ekman pumping are both consistent with that of winter coastal upwelling, but Ek-man transport is two times larger than Ekman pumping in January and February. Under the influence of El Niño-Southern Oscillation (ENSO), the upwelling shows remarkable interannual variability: during winter of El Niño (La Niña) years, an anticyclonic (a cyclonic) wind anomaly is established in the SCS, which behaves a northeasterly (southwesterly) anomaly and a positive (negative) wind stress curl anomaly off the north-west Borneo coast, enhancing (reducing) the upwelling and causing anomalous surface cooling (warming) and higher (lower) chlorophyll concentration. The sea surface temperature anomaly (SSTA) associated with ENSO off the northwest Borneo coast has an opposite phase to that off southeast Vietnam, resulting in a SSTA seesaw pattern in the southern SCS in winter.

  19. Deep ocean mass fluxes in the coastal upwelling off Mauritania from 1988 to 2012: variability on seasonal to decadal timescales

    Science.gov (United States)

    Fischer, Gerhard; Romero, Oscar; Merkel, Ute; Donner, Barbara; Iversen, Morten; Nowald, Nico; Ratmeyer, Volker; Ruhland, Götz; Klann, Marco; Wefer, Gerold

    2016-05-01

    A more than two-decadal sediment trap record from the Eastern Boundary Upwelling Ecosystem (EBUE) off Cape Blanc, Mauritania, is analysed with respect to deep ocean mass fluxes, flux components and their variability on seasonal to decadal timescales. The total mass flux revealed interannual fluctuations which were superimposed by fluctuations on decadal timescales. High winter fluxes of biogenic silica (BSi), used as a measure of marine production (mostly by diatoms) largely correspond to a positive North Atlantic Oscillation (NAO) index (December-March). However, this relationship is weak. The highest positive BSi anomaly was in winter 2004-2005 when the NAO was in a neutral state. More episodic BSi sedimentation events occurred in several summer seasons between 2001 and 2005, when the previous winter NAO was neutral or even negative. We suggest that distinct dust outbreaks and deposition in the surface ocean in winter and occasionally in summer/autumn enhanced particle sedimentation and carbon export on short timescales via the ballasting effect. Episodic perturbations of the marine carbon cycle by dust outbreaks (e.g. in 2005) might have weakened the relationships between fluxes and large-scale climatic oscillations. As phytoplankton biomass is high throughout the year, any dry (in winter) or wet (in summer) deposition of fine-grained dust particles is assumed to enhance the efficiency of the biological pump by incorporating dust into dense and fast settling organic-rich aggregates. A good correspondence between BSi and dust fluxes was observed for the dusty year 2005, following a period of rather dry conditions in the Sahara/Sahel region. Large changes of all bulk fluxes occurred during the strongest El Niño-Southern Oscillation (ENSO) in 1997-1999 where low fluxes were obtained for almost 1 year during the warm El Niño and high fluxes in the following cold La Niña phase. For decadal timescales, Bakun (1990) suggested an intensification of coastal upwelling

  20. The seasonal upwellings in the Gulf of Guinea

    Science.gov (United States)

    Verstraete, Jean-Marc

    Observational as well as numerical experiments show that Ekman divergence neither at the equator nor at the coast can explain a significant part of the annual upwelling in the Gulf of Guinea. The remote forcing theory is tested by analyzing both historical data and the FOCAL hydrographic stations (1982-1984). The meteorological data base is analysed as well. Analyses of the thermostad show that waters with the same characteristics as those of the South Atlantic Central Water (SACW) are carried by the equatorial under current (EUC) and the South Equatorial Undercurrent (SEUC) from the western-central equatorial Atlantic at 35° - 29°W towards the thermostad regions in the Gulf of Guinea. The thermostad water is then carried back westward in the two geostrophic compensation flows flanking the EUC at 2° - 3°N and 2° - 3°S. The cooling of the subthermoclinal waters off Abidjan (5°N) and Pointe-Noire (5°S) is related to the advection and vertical spreading of SACW between 500m and 50m in May-June-July. An exceptional warm event occurred in early 1984 in the Gulf of Guinea. The winds collapsed nearly completely all along the equator in January-April 1984. The onset of the African monsoon was late (in July-August 1984), then the monsoon was weaker than climatology in August-October 1984. The equatorial thermocline was observed 50m deeper than climatology in February 1984, then near the surface in July 1984. Sea levels rose over the equatorial Atlantic, the surge reaching about 13cm at 6°E in February 1984, when the western-central equatorial Atlantic was nearly flat. Minimum sea levels occurred in June-July 1984 at 6°E, before the African monsoon. During this event, the maximum speed in the shallow core of the equatorial undercurrent at 4°W and 6°E was nearly insensitive to large changes in the thermal structure (downwelling or upwelling situations). In February-May 1984, we have observed distinct increasing eastward flows at the equator below 250m and minimum

  1. Study of Baffle Boundary and System Parameters on Liquid-Solid Coupling Vibration of Rectangular Liquid-Storage Structure

    Directory of Open Access Journals (Sweden)

    Wei Jing

    2016-01-01

    Full Text Available In order to study the vibration problem of liquid-solid coupling of rectangular liquid-storage structure with horizontal elastic baffle, ignoring the influence of surface gravity wave, two different velocity potential functions corresponding to the liquid above and below the elastic baffle are assumed; based on the theory of mathematical equation and energy method, the formulas of basic frequency of liquid-solid coupling vibration system are derived, the baffle joined to the tank wall with 3 kinds of boundary conditions, namely, four edges simply supported, two opposite edges clamped and two opposite edges simply supported, and four edges clamped; the influence rules of baffle length-width ratio, the ratio of baffle height to liquid level, baffle elastic modulus, baffle density, baffle thickness, and liquid density on the coupling vibration performance are studied. The results show that the frequency of the clamped boundary is minimum; the influences of baffle length-width ratio and relative height on the basic frequency are much greater than that of the other system parameters; the relation between baffle length-width ratio and the frequency is exponential, while baffle relative height has a parabola relation with the frequency; the larger the baffle length-width ratio, the closer the baffle to the liquid level; the coupling frequency will be reduced more obviously.

  2. Exploring the potential of the RPA system SUMO for multipurpose boundary-layer missions during the BLLAST campaign

    Science.gov (United States)

    Reuder, Joachim; Båserud, Line; Jonassen, Marius O.; Kral, Stephan T.; Müller, Martin

    2016-06-01

    In June and July 2011 the RPAS (Remotely Piloted Aircraft System) SUMO (Small Unmanned Meteorological Observer) performed a total number of 299 scientific flights during the BLLAST (Boundary Layer Late Afternoon and Sunset Turbulence) campaign in southern France. Three different types of missions were performed: vertical profiling of the mean meteorological parameters (temperature, humidity and wind), horizontal surveys of the surface temperature and horizontal transects for the estimation of turbulence. The manuscript provides an introduction to the corresponding SUMO operations, including regulatory issues and the coordination of manned and unmanned airborne operations for boundary-layer research that have been pioneered during the BLLAST campaign. The main purpose of the SUMO flight strategy was atmospheric profiling at high temporal resolution. A total of 168 profile flights were performed during the campaign with typically more than 10 flights per Intensive Observational Period (IOP) day. The collected data allow for a detailed study of boundary-layer structure and dynamics and will be used for further analysis, e.g. the determination of profiles of sensible and latent heat fluxes. First, tests of a corresponding method have shown very promising results and have provided surface-flux values in close agreement with those from ground-based eddy-covariance measurements. In addition, 74 horizontal surveys of the IR emission of the surface were performed at altitudes of around 65 m. Each of those surveys covers a typical area of around 1 km2 and allows for an estimation of the surface-temperature variability, important information for the assessment of the heterogeneity of the surface forcing as a function of soil and vegetation properties. The comparison with other surface-temperature measurements shows that the raw data of the airborne and ground observations can differ considerably, but that even a very simple multiple regression method can reduce those

  3. IMPROVEMENT OF ACCURACY OF RADIATIVE HEAT TRANSFER DIFFERENTIAL APPROXIMATION METHOD FOR MULTI DIMENSIONAL SYSTEMS BY MEANS OF AUTO-ADAPTABLE BOUNDARY CONDITIONS

    Directory of Open Access Journals (Sweden)

    K. V. Dobrego

    2015-01-01

    Full Text Available Differential approximation is derived from radiation transfer equation by averaging over the solid angle. It is one of the more effective methods for engineering calculations of radia- tive heat transfer in complex three-dimensional thermal power systems with selective and scattering media. The new method for improvement of accuracy of the differential approximation based on using of auto-adaptable boundary conditions is introduced in the paper. The  efficiency  of  the  named  method  is  proved  for  the  test  2D-systems.  Self-consistent auto-adaptable boundary conditions taking into consideration the nonorthogonal component of the incident to the boundary radiation flux are formulated. It is demonstrated that taking in- to consideration of the non- orthogonal incident flux in multi-dimensional systems, such as furnaces, boilers, combustion chambers improves the accuracy of the radiant flux simulations and to more extend in the zones adjacent to the edges of the chamber.Test simulations utilizing the differential approximation method with traditional boundary conditions, new self-consistent boundary conditions and “precise” discrete ordinates method were performed. The mean square errors of the resulting radiative fluxes calculated along the boundary of rectangular and triangular test areas were decreased 1.5–2 times by using auto- adaptable boundary conditions. Radiation flux gaps in the corner points of non-symmetric sys- tems are revealed by using auto-adaptable boundary conditions which can not be obtained by using the conventional boundary conditions.

  4. Further influence of the eastern boundary on the seasonal variability of the Atlantic Meridional Overturning Circulation at 26N

    Science.gov (United States)

    Baehr, Johanna; Schmidt, Christian

    2016-04-01

    The seasonal cycle of the Atlantic Meridional Overturning Circulation (AMOC) at 26.5 N has been shown to arise predominantly from sub-surface density variations at the Eastern boundary. Here, we suggest that these sub-surface density variations have their origin in the seasonal variability of the Canary Current system, in particular the Poleward Undercurrent (PUC). We use a high-resolution ocean model (STORM) for which we show that the seasonal variability resembles observations for both sub-surface density variability and meridional transports. In particular, the STORM model simulation density variations at the eastern boundary show seasonal variations reaching down to well over 1000m, a pattern that most model simulations systematically underestimate. We find that positive wind stress curl anomalies in late summer and already within one degree off the eastern boundary result -through water column stretching- in strong transport anomlies in PUC in fall, coherent down to 1000m depth. Simultaneously with a westward propagation of these transport anomalies, we find in winter a weak PUC between 200 m and 500m, and southward transports between 600m and 1300m. This variability is in agreement with the observationally-based suggestion of a seasonal reversal of the meridional transports at intermediate depths. Our findings extend earlier studies which suggested that the seasonal variability at of the meridional transports across 26N is created by changes in the basin-wide thermocline through wind-driven upwelling at the eastern boundary analyzing wind stress curl anomalies 2 degrees off the eastern boundary. Our results suggest that the investigation of AMOC variability and particular its seasonal cycle modulations require the analysis of boundary wind stress curl and the upper ocean transports within 1 degree off the eastern boundary. These findings also implicate that without high-resolution coverage of the eastern boundary, coarser model simulation might not fully

  5. Neumann boundary controllability of the Gear-Grimshaw system with critical size restrictions on the spatial domain

    Science.gov (United States)

    Capistrano-Filho, Roberto A.; Gallego, Fernando A.; Pazoto, Ademir F.

    2016-10-01

    In this paper, we study the boundary controllability of the Gear-Grimshaw system posed on a finite domain (0, L), with Neumann boundary conditions: ut + uu_x+u_{xxx} + a v_{xxx} + a_1vv_x+a_2 (uv)_x =0, & {in} (0,L)× (0,T), c v_t +rv_x +vv_x+abu_{xxx} +v_{xxx}+a_2buu_x+a_1b(uv)_x =0, &{in} (0,L)× (0,T), u_{xx}(0,t)=h_0(t), u_x(L,t)=h_1(t), u_{xx}(L,t)=h_2(t), &{in} (0,T), v_{xx}(0,t)=g_0(t), v_x(L,t)=g_1(t), v_{xx}(L,t)=g_2(t), &{in} (0,T), u(x,0)= u^0(x), quad v(x,0)= v^0(x), & {in} (0,L). We first prove that the corresponding linearized system around the origin is exactly controllable in {(L^2(0,L))^2} when h 2( t) = g 2( t) = 0. In this case, the exact controllability property is derived for any L > 0 with control functions {h_0, g_0 in H^{-1/3}(0,T)} and {h_1, g_1in L^2(0,T)}. If we change the position of the controls and consider {h_0(t)=h_2(t)=0} (resp. {g_0(t)=g_2(t)=0)}, we obtain the result with control functions {g_0, g_2in H^{-1/3}(0,T)} and {h_1, g_1in L^2(0,T)} if and only if the length L of the spatial domain (0, L) does not belong to a countable set. In all cases, the regularity of the controls are sharp in time. If only one control act in the boundary condition, {h_0(t)=g_0(t)=h_2(t)=g_2(t)=0} and g 1( t) = 0 (resp. h 1( t) = 0), the linearized system is proved to be exactly controllable for small values of the length L and large time of control T. Finally, the nonlinear system is shown to be locally exactly controllable via the contraction mapping principle, if the associated linearized systems are exactly controllable.

  6. Quantum gravitational effects on boundary

    CERN Document Server

    Park, I Y

    2016-01-01

    Quantum gravitational effects may hold the key to some of the outstanding problems in theoretical physics. In this work we analyze the perturbative quantum effects on the boundary of a gravitational system and Dirichlet boundary condtion imposed at the classical level. Our analysis reveals that for a black hole solution there exists a clash between the quantum effects and Dirichlet boundary condition: the solution of the one-particle-irreducible (1PI) action no longer obeys the Dirichlet boundary condition. The analysis also suggests that the violation of the Dirichlet boundary condition should be tied with a certain mechanism of information storage on the boundary.

  7. Le Chatelier Principle for Out-of-Equilibrium and Boundary-Driven Systems: Application to Dynamical Phase Transitions

    Science.gov (United States)

    Shpielberg, O.; Akkermans, E.

    2016-06-01

    A stability analysis is presented for boundary-driven and out-of-equilibrium systems in the framework of the hydrodynamic macroscopic fluctuation theory. A Hamiltonian description is proposed which allows us to thermodynamically interpret the additivity principle. A necessary and sufficient condition for the validity of the additivity principle is obtained as an extension of the Le Chatelier principle. These stability conditions result from a diagonal quadratic form obtained using the cumulant generating function. This approach allows us to provide a proof for the stability of the weakly asymmetric exclusion process and to reduce the search for stability to the solution of two coupled linear ordinary differential equations instead of nonlinear partial differential equations. Additional potential applications of these results are discussed in the realm of classical and quantum systems.

  8. Modelling an alkenone-like proxy record in the NW African upwelling

    Directory of Open Access Journals (Sweden)

    X. Giraud

    2006-01-01

    Full Text Available A regional biogeochemical model is applied to the NW African coastal upwelling between 19° N and 27° N to investigate how a water temperature proxy, alkenones, are produced at the sea surface and recorded in the slope sediments. The biogeochemical model has two phytoplankton groups: an alkenone producer group, considered to be coccolithophores, and a group comprising other phytoplankton. The Regional Ocean Modelling System (ROMS is used to simulate the ocean circulation and takes advantage of the Adaptive Grid Refinement in Fortran (AGRIF package to set up an embedded griding system. In the simulations the alkenone temperature records in the sediments are between 1.1 and 2.3°C colder than the annual mean SSTs. Despite the seasonality of the coccolithophore production, this temperature difference is not mainly due to a seasonal bias, nor to the lateral advection of phytoplankton and phytodetritus seaward from the cold near-shore waters, but to the production depth of the coccolithophores. If coretop alkenone temperatures are effectively recording the annual mean SSTs, the amount of alkenone produced must vary among the coccolithophores in the water column and depend on physiological factors (e.g. growth rate, nutrient stress.

  9. Modelling an alkenone-like proxy record in the NW African upwelling

    Directory of Open Access Journals (Sweden)

    X. Giraud

    2006-01-01

    Full Text Available A regional biogeochemical model is applied to the NW African coastal upwelling between 19° N and 27° N to investigate how a water temperature proxy is produced at the sea surface and recorded in the slope sediments. The biological model has two phytoplankton groups, to distinguish an alkenone producer group (considered as coccolithophores from other phytoplankton. The Regional Ocean Modelling System (ROMS is used to simulate the ocean circulation, and takes advantage of the Adaptive Grid Refinement in Fortran (AGRIF package to set up an embedded griding system. The results show that the alkenone-like temperature records in the sediments are between 1.1 and 2.1°C colder compared to the annual mean SSTs. Despite the seasonality of the coccolithophorid production, this temperature difference is not mainly due to a seasonal bias, nor to the lateral advection of phytoplankton and phytodetritus from the cold water domain to most offshore locations, but to the production depth of the coccolithophores. If core-top sediment alkenone-derived temperatures are effectively recording the annual mean SSTs, the quantitative alkenone production in the water column must be inhomogeneous among the coccolithophore population and depend on physiological factors (growth rate, nutrient stress.

  10. Modelling an alkenone-like proxy record in the NW African upwelling

    Science.gov (United States)

    Giraud, X.

    2006-06-01

    A regional biogeochemical model is applied to the NW African coastal upwelling between 19° N and 27° N to investigate how a water temperature proxy, alkenones, are produced at the sea surface and recorded in the slope sediments. The biogeochemical model has two phytoplankton groups: an alkenone producer group, considered to be coccolithophores, and a group comprising other phytoplankton. The Regional Ocean Modelling System (ROMS) is used to simulate the ocean circulation and takes advantage of the Adaptive Grid Refinement in Fortran (AGRIF) package to set up an embedded griding system. In the simulations the alkenone temperature records in the sediments are between 1.1 and 2.3°C colder than the annual mean SSTs. Despite the seasonality of the coccolithophore production, this temperature difference is not mainly due to a seasonal bias, nor to the lateral advection of phytoplankton and phytodetritus seaward from the cold near-shore waters, but to the production depth of the coccolithophores. If coretop alkenone temperatures are effectively recording the annual mean SSTs, the amount of alkenone produced must vary among the coccolithophores in the water column and depend on physiological factors (e.g. growth rate, nutrient stress).

  11. Seasonal variation of upwelling in the Alaskan Beaufort Sea: Impact of sea ice cover

    Science.gov (United States)

    Schulze, Lena M.; Pickart, Robert S.

    2012-06-01

    Data from a mooring array deployed from August 2002 to September 2004 are used to characterize differences in upwelling near the shelf break in the Alaskan Beaufort Sea due to varying sea ice conditions. The record is divided into three ice seasons: open water, partial ice, and full ice. The basic response is the same in each of the seasons. Roughly 8 h after the onset of easterly winds the shelf break jet reverses, followed approximately 10 h later by upwelling of saltier water which is cold near the shelf break (Pacific Winter Water) and warm at depth (Atlantic Water). The secondary circulation at the outer shelf is, to first order, consistent with a two-dimensional Ekman balance of offshore flow in the upper layer and onshore flow at depth. There are, however, important seasonal differences in the upwelling. Overall the response is strongest in the partial ice season and weakest in the full ice season. It is believed that these differences are dictated by the degree to which wind stress is transmitted through the pack-ice, as the strength of the wind-forcing was comparable over the three seasons. An EOF-based upwelling index is constructed using information about the primary flow, secondary flow, and hydrography. The ability to predict upwelling using the wind record alone is explored, which demonstrates that 90% of easterly wind events exceeding 9.5 m s-1 drive significant upwelling. During certain periods the ice cover on the shelf became landfast, which altered the upwelling and circulation patterns near the shelf break.

  12. Role of pulsed winds on detachment of low salinity water from the Pearl River Plume: Upwelling and mixing processes

    Science.gov (United States)

    Chen, Zhaoyun; Pan, Jiayi; Jiang, Yuwu

    2016-04-01

    The detachment of low salinity water (LSW) from the Pearl River plume occurs frequently as revealed by in situ observations and satellite images, and plays an important role in cross-shore transport of the nutrient-rich plume water. In this study, the Regional Ocean Modeling System (ROMS) is used to simulate the LSW detachment process forced by realistic and idealized winds, and to explore its dynamical mechanisms. Modeling results show that the LSW detachment appears under a pulsed southwesterly wind, while tidal mixing modifies the size and salinity of the detached LSW. Strong pulsed wind causes the LSW to separate from the plume and move offshore quickly after the detachment. Under a pulsed northeasterly wind, however, the plume without separation of the LSW moves shoreward, indicating that the LSW detachment is sensitive to wind direction. In the plume region, upwelling develops under the forcing of the pulsed southwesterly wind, which transports high salinity bottom water to the surface layer, while the shear mixing in the upper layer further enhances the surface buoyancy flux, leading to appearance of high salinity water in the surface layer off the Pearl River estuary mouth, cutting off the eastward-spreading plume water, and resulting in the plume LSW detachment. Further analysis shows that the pulsed southwesterly wind induces positive local salinity change rate in the LSW detachment area. The pulsed upwelling-favorable wind with duration of 2-5 days is responsible for the detachment process.

  13. Emerging boundaries

    DEFF Research Database (Denmark)

    Løvschal, Mette

    2014-01-01

    This article proposes a processual ontology for the emergence of man-made, linear boundaries across northwestern Europe, particularly in the first millennium BC. Over a significant period of time, these boundaries became new ways of organizing the landscape and settlements—a phenomenon that has...... of this phenomenon emerged along equivalent trajectories. At the same time, variation in the regional incorporation of these linear phenomena points toward situation-specific applications and independent development....

  14. High Temperature Metamorphism In The Conductive Boundary Layer Of An Intrusion Of Rhyolite Magma In The Krafla Geothermal System, Iceland

    Science.gov (United States)

    Schiffman, P.; Zierenberg, R. A.; Fridleifsson, G. O.; Elders, W. A.; Mortensen, A. K.

    2011-12-01

    A rhyolite magma body within the Krafla geothermal system- encountered at a depth of 2.1 km during drilling of the Iceland Deep Drilling Project's IDDP-1 borehole - is producing high temperature metamorphism within adjacent country rocks. Cuttings recovered during drilling within a few meters of the intrusive contact are undergoing recrystallization into granoblastic, pyroxene hornfelses. In mafic rocks, clinopyroxene-orthopyroxene-plagioclase-magnetite-ilmenite assemblages record temperatures in the range of 800-950°C. Silicic lithologies - mainly older felsitic intrusions -contain pockets of rhyolite melt, quenched to glass during drilling, amongst alkali feldspar, plagioclase, quartz, clinopyroxene, and magnetite. Curiously, no lower grade metamorphic assemblages have been identified in the drill cuttings, and country rocks at distances beyond 30 m of the contact are essentially unaltered. These findings suggest that the intruding rhyolite magma body has created a thin conductive boundary layer above it, but that a contact metamorphic aureole has not as yet developed beyond this. The heat flow across the boundary layer is calculated to be a minimum of 23 W m-2. This flux is capable of supplying steam to a geothermal power plant that can produce approximately 40 MW of electrical generation from a single well that has a measured well-head temperature of up to 415°C.

  15. Modelling of upwelling in the coastal area of Cabo Frio (Rio de Janeiro - Brazil

    Directory of Open Access Journals (Sweden)

    Carlos Carbonel

    1998-01-01

    Full Text Available A 1 1/2 reduced-gravity model is proposed to study the hydrodynamic and thermodynamic features of the coastal upwelling area of Cabo Frio (Rio de Janeiro-Brazil. The vertical structure of the model is described by an active layer overlaying a deep inert layer where the pressure gradient is set to zero. For the upper layer, the model includes the turbulent version of the momentum. continuity and heat equations. The conservation of heat is represented by a transport equation to describe the thermodynamic changes of the sea surface temperature (SST. The solution domain includes open boundaries in which weakly-retlective conditions are prescribed. Solutions are found numerically on a uniform grid and the fundamental equations are approximated by the finite difference method. Numerical experiments are performed to evaluate the dynamic response of the coastal area of Cabo Frio forced by uniform and non-uniform wind fields. The solutions differ considerably depending on the orientation of the winds. East and northeast winds correlate with colder waters in the zonal coastline of this area and the presence of tlows toward Cabo Frio correlates with north wind components. The proposed model is validated with the numerical simulation of an observed event of upwelling, where a time­-dependent and non-uniform wind ficld develops a SST pattern similar as the observations, particularly the extension of the cool water plume in south-west direction and the rapid time variation of the SST.Um modelo de gravidade reduzida de 1 1/2 camada é proposto para estudar as características hidrodinmicas e termodinmicas da área costeira de Cabo Frio (Rio de Janeiro ­Brasil. A estrutura vertical do modelo é descrita por uma camada ativa sobre uma camada profunda sem movimento onde o gradicnte de pressão é zero. Para a camada superior. o modelo incluí a versão turbulenta das equações de momentum, continuidade e calor. A conservação do calor é representada por uma

  16. Using Remotely Piloted Aircraft System to Study the Evolution of the Boundary Layer Related to Fog Events

    Science.gov (United States)

    Roberts, G. C.; Cayez, G.; Ronflé-Nadaud, C.; Albrand, M.; Dralet, J. P.; Momboisse, G.; Nicoll, K.; Seity, Y.; Bronz, M.; Hattenberger, G.; Gorraz, M.; Bustico, A.

    2014-12-01

    Over the past decade, the scientific community has embraced the use of RPAS (remotely piloted aircraft system) as a tool to improve observations of the Earth's surface and atmospheric phenomena. The use of small RPAS (Remotely Piloted Aircraft System) in atmospheric research has increased because of their relative low-cost, compact size and ease of operation. Small RPAS are especially adapted for observing the atmospheric boundary layer processes at high vertical and temporal resolution. To this end, CNRM, ENAC, and ENM have developed the VOLTIGE (Vecteurs d'Observation de La Troposphere pour l'Investigation et la Gestion de l'Environnement) program to study the life cycle of fog with multiple, small RPAS. The instrumented RPAS flights have successfully observed the evolution of the boundary layer and dissipation of fog events. In addition, vertical profiles from the RPAS have been compared with Météo France forecast models, and the results suggest that forecast models may be improved using high resolution and frequent in-situ measurements. Within the VOLTIGE project, a flying-wing RPAS with four control surfaces was developed to separate elevator and aileron controls in order to reduce the pitch angle envelope and improve turbulence and albedo measurements. The result leads to a small RPAS with the capability of flying up to two hours with 150 grams of payload, while keeping the hand-launch capability as a constraint for regular atmospheric research missions. High frequency data logging has been integrated into the main autopilot in order to synchronize navigation and payload measurements, as well as allowing an efficient sensor-based navigation. The VOLTIGE program also encourages direct participation of students on the advancement of novel observing systems for atmospheric sciences, and provides a step towards deploying small RPAS in an operational network. VOLTIGE is funded by the Agence Nationale de Recherche (ANR-Blanc 2012) and supported by Aerospace

  17. Bacterial and Archaeal Communities Variability Associated with Upwelling and Anthropogenic Pressures in the Protection Area of Arraial do Cabo (Cabo Frio region - RJ

    Directory of Open Access Journals (Sweden)

    SERGIO A. COELHO-SOUZA

    2015-09-01

    Full Text Available ABSTRACTUpwelling systems contain a high diversity of pelagic microorganisms and their composition and activity are defined by factors like temperature and nutrient concentration. Denaturing gradient gel electrophoresis (DGGE technique was used to verify the spatial and temporal genetic variability of Bacteria and Archaea in two stations of the Arraial do Cabo coastal region, one under upwelling pressure and another under anthropogenic pressure. In addition, biotic and abiotic variables were measured in surface and deep waters from three other stations between these stations. Six samplings were done during a year and adequately represented the degrees of upwelling and anthropogenic pressures to the system. Principal Component Analysis (PCA showed negative correlations between the concentrations of ammonia and phosphorous with prokaryotic secondary production and the total heterotrophic bacteria. PCA also showed negative correlation between temperature and the abundance of prokaryotic cells. Bacterial and archaeal compositions were changeable as were the oceanographic conditions, and upwelling had a regional pressure while anthropogenic pressure was punctual. We suggest that the measurement of prokaryotic secondary production was associated with both Bacteria and Archaea activities, and that substrate availability and temperature determine nutrients cycling.

  18. Benthic primary production in an upwelling-influenced coral reef, Colombian Caribbean

    Science.gov (United States)

    Bayraktarov, Elisa; Hauffe, Torsten; Pizarro, Valeria; Wilke, Thomas; Wild, Christian

    2014-01-01

    In Tayrona National Natural Park (Colombian Caribbean), abiotic factors such as light intensity, water temperature, and nutrient availability are subjected to high temporal variability due to seasonal coastal upwelling. These factors are the major drivers controlling coral reef primary production as one of the key ecosystem services. This offers the opportunity to assess the effects of abiotic factors on reef productivity. We therefore quantified primary net (Pn) and gross production (Pg) of the dominant local primary producers (scleractinian corals, macroalgae, algal turfs, crustose coralline algae, and microphytobenthos) at a water current/wave-exposed and-sheltered site in an exemplary bay of Tayrona National Natural Park. A series of short-term incubations was conducted to quantify O2 fluxes of the different primary producers during non-upwelling and the upwelling event 2011/2012, and generalized linear models were used to analyze group-specific O2 production, their contribution to benthic O2 fluxes, and total daily benthic O2 production. At the organism level, scleractinian corals showed highest Pn and Pg rates during non-upwelling (16 and 19 mmol O2 m−2 specimen area h−1), and corals and algal turfs dominated the primary production during upwelling (12 and 19 mmol O2 m−2 specimen area h−1, respectively). At the ecosystem level, corals contributed most to total Pn and Pg during non-upwelling, while during upwelling, corals contributed most to Pn and Pg only at the exposed site and macroalgae at the sheltered site, respectively. Despite the significant spatial and temporal differences in individual productivity of the investigated groups and their different contribution to reef productivity, differences for daily ecosystem productivity were only present for Pg at exposed with higher O2 fluxes during non-upwelling compared to upwelling. Our findings therefore indicate that total benthic primary productivity of local autotrophic reef communities is

  19. Benthic primary production in an upwelling-influenced coral reef, Colombian Caribbean

    Directory of Open Access Journals (Sweden)

    Corvin Eidens

    2014-09-01

    Full Text Available In Tayrona National Natural Park (Colombian Caribbean, abiotic factors such as light intensity, water temperature, and nutrient availability are subjected to high temporal variability due to seasonal coastal upwelling. These factors are the major drivers controlling coral reef primary production as one of the key ecosystem services. This offers the opportunity to assess the effects of abiotic factors on reef productivity. We therefore quantified primary net (Pn and gross production (Pg of the dominant local primary producers (scleractinian corals, macroalgae, algal turfs, crustose coralline algae, and microphytobenthos at a water current/wave-exposed and-sheltered site in an exemplary bay of Tayrona National Natural Park. A series of short-term incubations was conducted to quantify O2 fluxes of the different primary producers during non-upwelling and the upwelling event 2011/2012, and generalized linear models were used to analyze group-specific O2 production, their contribution to benthic O2 fluxes, and total daily benthic O2 production. At the organism level, scleractinian corals showed highest Pn and Pg rates during non-upwelling (16 and 19 mmol O2 m−2 specimen area h−1, and corals and algal turfs dominated the primary production during upwelling (12 and 19 mmol O2 m−2 specimen area h−1, respectively. At the ecosystem level, corals contributed most to total Pn and Pg during non-upwelling, while during upwelling, corals contributed most to Pn and Pg only at the exposed site and macroalgae at the sheltered site, respectively. Despite the significant spatial and temporal differences in individual productivity of the investigated groups and their different contribution to reef productivity, differences for daily ecosystem productivity were only present for Pg at exposed with higher O2 fluxes during non-upwelling compared to upwelling. Our findings therefore indicate that total benthic primary productivity of local autotrophic reef

  20. Late Quaternary upper-water column structure in upwelling areas of the South China Sea

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Based on a quantitative analysis of planktonic foraminifera in two gravity cores (17928 and 17954), the history of the upper-water structure of the eastern and western slopes of the South China Sea (SCS) over the last 220 Ka was reconstructed using the transfer function technique. Our results show that lower sea surface temperature (SST) and shallower depth of thermocline (DOT) exist at Core 17928, off Luzon, in the glacial periods; on the contrary, the same situation turned up in the interglacial at Core 17954, off Vietnam. These changes of the upper-water column structure in the two areas are induced by coastal upwelling, which in turn is driven by monsoons, namely, winter monsoon leads to upwelling at the eastern slope, and summer monsoon gives birth to upwelling on the western slope. Moreover, the intensity of upwellings is also closely related to the evolution of the East Asian monsoon. Therefore, we assume that the changes of the upwelling in the two sites indicate strengthenning of winter and su mmer monsoon during the glacial and interglacial periods, respectively.

  1. Intraseasonal coastal upwelling signal along the southern coast of Java observed using Indonesian tidal station data

    Science.gov (United States)

    Horii, Takanori; Ueki, Iwao; Syamsudin, Fadli; Sofian, Ibnu; Ando, Kentaro

    2016-04-01

    Sea level variations along the coasts of Sumatra and Java were investigated to determine the coastal upwelling signal that is linked to local sea surface temperature (SST) variability. We used Indonesian tidal station data together with satellite SST data and atmospheric reanalysis data. The sea level variations along the southern coast of Java have a significant coherence with remote wind, local wind, and local SST variations, with an intraseasonal time scale of 20-50 days. Assuming that a coastal upwelling signal would appear as a sea level drop (SLD), we focused on intraseasonal-scale SLD events in the data. Significant upwelling signals are frequently observed during both the boreal summer and winter. To evaluate the impact of the coastal upwelling on local SST, we examined statistical relationships between sea level and SST variations. The results demonstrated that events that occurred during April-August were associated with local SST cooling. The horizontal distribution of the SST cooling was analogous with annual mean SST, suggesting the importance of intraseasonal-scale coastal upwelling in forming the climatic conditions of the southeastern tropical Indian Ocean.

  2. Synchronisation of the equatorial QBO by the annual cycle in tropical upwelling in a warming climate

    Science.gov (United States)

    Rajendran, Kylash; Moroz, Irene; Read, Peter; Osprey, Scott

    2016-04-01

    The response of the period of the quasi-biennial oscillation (QBO) to increases in tropical upwelling is considered using a one-dimensional model. We find that the imposition of the annual cycle in tropical upwelling creates substantial variability in the period of the QBO. The annual cycle creates synchronisation regions in the wave forcing space, within which the QBO period locks onto an integer multiple of the annual forcing period. Outside of these regions, the QBO period undergoes discrete jumps as it attempts to find a stable relationship with the oscillator forcing. The resulting set of QBO periods can be either discrete or broad-banded, depending on the intrinsic period of the QBO. We use the same model to study the evolution of the QBO period as the strength of tropical upwelling increases as would be expected in a warmer climate. The QBO period lengthens and migrates closer towards 36 and 48 month locking regions as upwelling increases. The QBO period does not vary continuously with increased upwelling, however, but instead transitions through a series of 2- and 3-cycles before becoming locked to the annual cycle. Some evidence for the cyclical behaviour of the QBO periods in the real atmosphere is presented.

  3. Sporadic Groundwater Upwelling in Deep Martian Craters: Evidence for Lacustrine Clays and Carbonates

    Science.gov (United States)

    Michalski, J. R.; Rogers, A. D.; Wright, S. P.; Niles, P.; Cuadros, J.

    2012-01-01

    While the surface of Mars may have had an active hydrosphere early in its history [1], it is likely that this water retreated to the subsurface early on due to loss of the magnetic field and early atmosphere [2]. This likely resulted in the formation of two distinct aqueous regimes for Mars from the Late Noachian onward: one dominated by redistribution of surface ice and occasional melting of snow/ice [3], and one dominated by groundwater activity [4]. The excavation of alteration minerals from deep in the crust by impact craters points to an active, ancient, deep hydrothermal system [5]. Putative sapping features [6] may occur where the groundwater breached the surface. Upwelling groundwater may also have played a critical role in the formation of massive, layered, cemented sediments in Sinus Meridiani [7,8], in the Valles Marineris [9], and possibly in Gale Crater [10], where the Curiosity Rover will land later this year. Understanding the past distribution, geochemistry, and significance of groundwater on Mars is critical to untangling the origins of deep alteration minerals, Hesperian sulfate deposits, and crater fill deposits at Gale Crater or in other locations.

  4. Study area boundary for the Death Valley regional ground-water flow system, Nevada and California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This digital data set represents the Death Valley regional ground-water flow system (DVRFS) study area which encompasses approximately 100,000-square kilometers in...

  5. The boundary l

    Directory of Open Access Journals (Sweden)

    Muhammad Naseer

    2014-09-01

    Full Text Available The present problem is the steady boundary layer flow and heat transfer of a hyperbolic tangent fluid flowing over a vertical exponentially stretching cylinder in its axial direction. After applying usual boundary layer with a suitable similarity transformation to the given partial differential equations and the boundary conditions, a system of coupled nonlinear ordinary differential equations is obtained. This system of ordinary differential equations subject to the boundary conditions is solved with the help of Runge–Kutta–Fehlberg method. The effects of the involved parameters such as Reynolds numbers, Prandtl numbers, Weissenberg numbers and the natural convection parameter are presented through the graphs. The associated physical properties on the flow and heat transfer characteristics that is the skin friction coefficient and Nusselt numbers are presented for different parameters.

  6. Positive Solutions for System of 2-th Order Sturm-Liouville Boundary Value Problems on time Scales

    Indian Academy of Sciences (India)

    K R Prasad; A Kameswara Rao; B Bharathi

    2014-02-01

    Intervals of the parameters and are determined for which there exist positive solutions to the system of dynamic equations \\begin{align*}(-1)^n u^{^{2n}}(t)+ p(t) f(((t)))=0, & t\\in[a, b],\\\\ (-1)^n^{^{2n}} (t) + q(t)g (u((t))) = 0, & t\\in [a, b],\\end{align*} satisfying the Sturm–Liouville boundary conditions \\begin{align*}& _{i+1}u^{^{2i}}(a)-_{i+1}u^{^{2i+1}}(a)=0, _{i+1}u^{^{2i}}((b))+_{i+1}u^{^{2i+1}}((b))=0,\\\\ & _{i+1}^{^{2i}}(a)-_{i+1}^{^{2i+1}}(a)=0,_{i+1}^{^{2i}}((b))+_{i+1}^{^{2i+1}}((b))=0,\\end{align*} for $0≤ i≤ n-1$. To this end we apply a Guo–Krasnosel’skii fixed point theorem.

  7. Uniform regularity estimates in homogenization theory of elliptic systems with lower order terms on the Neumann boundary problem

    Science.gov (United States)

    Xu, Qiang

    2016-10-01

    In this paper, we mainly employed the idea of the previous paper [34] to study the sharp uniform W 1 , p estimates with 1 general elliptic systems with the Neumann boundary condition on a bounded C 1 , η domain, arising in homogenization theory. Based on the skills developed by Z. Shen in [27] and by T. Suslina in [31,32], we also established the L2 convergence rates on a bounded C 1 , 1 domain and a Lipschitz domain, respectively. Here we found a "rough" version of the first order correctors (see (1.12)), which can unify the proof in [27] and [32]. It allows us to skip the corresponding convergence results on Rd that are the preconditions in [31,32]. Our results can be regarded as an extension of [23] developed by C. Kenig, F. Lin, Z. Shen, as well as of [32] investigated by T. Suslina.

  8. Modeling for mean ion activity coefficient of strong electrolyte system with new boundary conditions and ion-size parameters

    Institute of Scientific and Technical Information of China (English)

    Miyi Li; Tao Fang

    2015-01-01

    A rigorous approach is proposed to model the mean ion activity coefficient for strong electrolyte systems using the Poisson–Boltzmann equation. An effective screening radius similar to the Debye decay length is introduced to define the local composition and new boundary conditions for the central ion. The crystallographic ion size is also considered in the activity coefficient expressions derived and non-electrostatic contributions are neglected. The model is presented for aqueous strong electrolytes and compared with the classical Debye–Hückel (DH) limiting law for dilute solutions. The radial distribution function is compared with the DH and Monte Carlo studies. The mean ion activity coefficients are calculated for 1:1 aqueous solutions containing strong electrolytes composed of alkali halides. The individual ion activity coefficients and mean ion activity coefficients in mixed sol-vents are predicted with the new equations.

  9. Analysis and design of prisms using the derivatives of a ray. Part II: the derivatives of boundary variable vector with respect to system variable vector.

    Science.gov (United States)

    Lin, Psang Dain

    2013-06-20

    To evaluate the merit function of an optical system, it is necessary to determine the first- and second-order derivative matrices of the boundary variable vector with respect to the system variable vector. Accordingly, the present study proposes a computationally efficient method for determining both matrices for optical systems containing only flat boundary surfaces. The validity of the proposed method is demonstrated by means of two illustrative prism design problems. In general, the results show that the proposed method can provide efficient search directions in many gradient-based optical design optimization methods.

  10. The NURBS curves in modelling the shape of the boundary in the parametric integral equations systems for solving the Laplace equation

    Science.gov (United States)

    Zieniuk, Eugeniusz; Kapturczak, Marta; Sawicki, Dominik

    2016-06-01

    In solving of boundary value problems the shapes of the boundary can be modelled by the curves widely used in computer graphics. In parametric integral equations system (PIES) such curves are directly included into the mathematical formalism. Its simplify the way of definition and modification of the shape of the boundary. Until now in PIES the B-spline, Bézier and Hermite curves were used. Recent developments in the computer graphics paid our attention, therefore we implemented in PIES possibility of defining the shape of boundary using the NURBS curves. The curves will allow us to modeling different shapes more precisely. In this paper we will compare PIES solutions (with applied NURBS) with the solutions existing in the literature.

  11. Observations of boundary layer, mixed-phase and multi-layer Arctic clouds with different lidar systems during ASTAR 2007

    Directory of Open Access Journals (Sweden)

    A. Lampert

    2009-07-01

    Full Text Available During the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR, which was conducted in Svalbard in March and April 2007, tropospheric Arctic clouds were observed with two ground-based backscatter lidar systems (micro pulse lidar and Raman lidar and with an airborne elastic lidar. An increase in low-level (cloud tops below 2.5 km cloud cover from 51% to 65% was observed above Ny-Ålesund during the time of the ASTAR campaign. Four different case studies of lidar cloud observations are analyzed: With the ground-based Raman lidar, a pre-condensation layer was observed at an altitude of 2 km. The layer consisted of small droplets with a high number concentration (around 300 cm−3 at low temperatures (−30°C. Observations of a boundary layer mixed-phase cloud by airborne lidar were evaluated with the measurements of concurrent airborne in situ and spectral solar radiation sensors. Two detailed observations of multiply layered clouds in the free troposphere are presented. The first case was composed of various ice layers with different optical properties detected with the Raman lidar, the other case showed a mixed-phase double layer and was observed by airborne lidar.

    The analysis of these four cases confirmed that lidar data provide information of the whole range from subvisible to optically thick clouds. Despite the attenuation of the laser signal in optically thick clouds and multiple scattering effects, information on the geometrical boundaries of liquid water clouds were obtained. Furthermore, the dominating phase of the clouds' particles in the layer closest to the lidar system could be retrieved.

  12. Stabilization of ODE-Schrodinger cascaded systems subject to boundary control matched disturbance

    Directory of Open Access Journals (Sweden)

    Ya-Ping Guo

    2015-09-01

    Full Text Available In this article, we consider the state feedback stabilization of ODE-Schrodinger cascaded systems with the external disturbance. We use the backstepping transformation to handle the unstable part of the ODE, then design a feedback control which is used to cope with the disturbance and stabilize the Schrodinger part. By active disturbance rejection control (ADRC approach, the disturbance is estimated by a constant high gain estimator, then the feedback control law can be designed. Next, we show that the resulting closed-loop system is practical stable, where the peaking value appears in the initial stage and the stabilized result requires that the derivative of disturbance be uniformly bounded. To avoid the peak phenomenon and to relax the restriction on the disturbance, a time varying high gain estimator is presented and asymptotical stabilization of the corresponding closed-loop system is proved. Finally, the effectiveness of the proposed control is verified by numerical simulations.

  13. A multidischarge actuator system for power electrohydrodynamic action on the boundary layer of aerohydrodynamic surfaces

    Science.gov (United States)

    Aleshin, B. S.; Kuryachii, A. P.; Rebrov, I. E.; Khomich, V. Yu.; Chernyshev, S. L.; Yamshchikov, V. A.

    2017-01-01

    We present the results of a study of a new multidischarge actuator system designed for active gas flow control on the basis of a three-electrode circuit with a shielding electrode, in which the role of an accelerating electrode is played by the solid equipotential sheath surface of the wing. The main parameters of the multidischarge actuator system and classical scheme of electrodes are compared—namely, the induced air flow velocity, average integral volume force, average consumed power, and energy efficiency coefficient calculated per unit length of the external electrode.

  14. Variabilidad estacional de cadmio en un sistema de surgencia costera del norte de Chile (Bahía Mejillones del Sur, 23° S Seasonal variability of cadmium in a coastal upwelling system off northern Chile (Mejillones bay, 23° S

    Directory of Open Access Journals (Sweden)

    JORGE VALDÉS

    2006-12-01

    observada en esta razón pueden ser explicados ya sea por una mayor eficiencia en la remoción de PO4 que de Cadmio en las aguas superficiales o una mayor remineralización de cadmio en las aguas subsuperficialesTotal and dissolved cadmium were measured from surface to 100 m water depth, between June 2002 and April 2003, in Mejillones bay. Total and dissolved cadmium range concentration was 0.41-10.7 and 0.08-1.61 nM, respectively. Cadmium profiles and water structure were used to study seasonal variability patterns of this metal in this upwelling system. Oceanographic conditions during this period correspond to a normal (non-El Niño year. Water masses present in this bay correspond to subantartic superficial water, subtropical superficial water and Equatorial subsuperficial water with different degree of mixture and stratification during sampling period. Cadmium profiles showed a classic nutrient-type distribution. Whereas some differences in this profiles could be attributed to a water masses mixing condition into the bay. Multivariate analysis indicates that temporal cadmium variations were associated with chlorophyll-a concentration and temperature fluctuation, indicating that, at this temporal resolution, phytoplanktonic biomass production is the principal factor controlling cadmium concentration in surface waters of Mejillones bay. By other hand, in spite of cadmium being a redox-sensitive metal, any significant influence of dissolved oxygen on this metal were founded, thus microxic condition of bottom water of Mejillones bay is not the principal factor that promotes cadmium flux to the sediments. Cd/PO4 ratio is in agreement with normal values reported for the Chilean coast, and its low values, compared with the northeast Pacific coast, can be explained either by the fact that PO4 is more efficiently removed than cadmium from the surface layer, or that cadmium remineralization is occurring much faster than in the case of PO4

  15. Examples of Systems of Functions Being Riesz Bases in L_{2}(0,1). Application to a Nonlinear Boundary Value Problem

    CERN Document Server

    Zhidkov, P E

    2001-01-01

    We establish examples of systems of functions being Riesz bases in L_{2}(0,1). We then apply this result to improve a theorem presented in [9] showing that an arbitrary "standard" system of solutions of a nonlinear boundary value problem, normalized to 1 in the same space, is a Riesz basis in this space. The proofs in this work are quite elementary.

  16. Uniqueness of the solution of the Gaudin’s equations, which describe a one-dimensional system of point bosons with zero boundary conditions

    Science.gov (United States)

    Tomchenko, Maksim

    2017-02-01

    We show that the system of Gaudin’s equations for quasimomenta k j , which describes a one-dimensional system of spinless point bosons with zero boundary conditions, has the unique real solution for each set of quantum numbers n j .

  17. Cross-shore transport in a daily varying upwelling regime: A case study of barnacle larvae on the southwestern Iberian coast

    Science.gov (United States)

    Trindade, A.; Peliz, A.; Dias, J.; Lamas, L.; Oliveira, P. B.; Cruz, T.

    2016-09-01

    With favored offshore and downstream advection, the question of which physical mechanism may promote onshore transport of larvae in upwelling systems is of central interest. We have conducted a semi-realistic high resolution (0.25 km) numerical study of Lagrangian transports across the inner-shelf under upwelling-favorable wind forcing conditions, focusing on the shelf area of the Southwestern Portuguese coast, in the lee of Cape Sines. We add our findings to several years of biological observations of C. montagui, a planktonic species with higher recruitment during the upwelling peak timely with the daylight flood. Simulations cover a fifteen days period during the summer of 2006. We focused on Spring and Neap tide periods and observed upfront differences between simulations and the in situ observations. However, the model is capable of representing the main dynamics of the region, namely the repetitive character of the inner-shelf currents. We find that the cross-shore flow varies significantly in the daily cycle, and locally within a scale of a few kilometers in association with local topography and the presence of the cape. We consider the region immediately in the lee of the cape to be an upwelling shadow where the larvae became retained, and found that tidally tied migration proves beneficial for successful recruitment during the spring tides period. Our work suggested that the wind is not the only mechanism responsible for the daily variability of the cross-shore exchange. However, its sharp reversal at midday is critical for the advection of larvae towards the coast.

  18. The combined effect of transient wind-driven upwelling and eddies on vertical nutrient fluxes and phytoplankton dynamics along Ningaloo Reef, Western Australia

    Science.gov (United States)

    Zhang, Zhenlin; Lowe, Ryan; Ivey, Greg; Xu, Jiangtao; Falter, James

    2016-07-01

    We investigate the influence of wind stresses, stratification, and coastal mesoscale eddies on upwelling intensity, vertical nutrient fluxes, and phytoplankton biomass on the continental shelf off Ningaloo Reef in northwestern Australia during an austral spring-summer period. A three-dimensional (3-D) hydrodynamic model, ROMS (Regional Ocean Modeling System), was coupled with a four-component nitrogen-based biogeochemical NPZD model (Nitrogen Phytoplankton Zooplankton Detritus) to resolve the shelf circulation as well as the coupled nutrient and phytoplankton dynamics within a broad shelf region surrounding Ningaloo Reef. The simulated currents, temperatures, and chlorophyll a concentrations generally agreed well with both the remotely sensed satellite images and observational data collected during a field experiment from September to November 2010. Scenario tests for an individual wind-driven upwelling event under a variety of hypothetical physical forcing conditions showed that shelf currents and biogeochemical variables were largely a function of wind stress and stratification. However, the functional relationships derived from this single wind event could not be extrapolated to other periods of the upwelling season, due to the additional influence of 3-D mesoscale processes on the shelf. The presence, intensification, and propagation of a coastal anticyclonic eddy during the study period strongly influenced the spatial and temporal variations in nutrient profiles, which in turn caused fluctuations in vertical nutrient fluxes that were largely independent of wind stress. These results emphasize that it is necessary to fully capture the 3-D details of the mesoscale and submesoscale coastal dynamics to properly predict upwelling-induced coastal phytoplankton dynamics in eddy-intensive shelf regions such as Ningaloo Reef.

  19. Boundary Conditions of the High-Investment Human Resource Systems-Small-Firm Labor Productivity Relationship

    Science.gov (United States)

    Chadwick, Clint; Way, Sean A.; Kerr, Gerry; Thacker, James W.

    2013-01-01

    Although a few published, multiindustry, firm-level, empirical studies have linked systems of high-investment or high-performance human resource management practices to enhanced small-firm performance, this stream of strategic human resource management research is underdeveloped and equivocal. Accordingly, in this study, we use a sample of…

  20. Linking mantle upwelling with the lithosphere descent [corrected] and the Japan Sea evolution: a hypothesis.

    Science.gov (United States)

    Ismail-Zadeh, Alik; Honda, Satoru; Tsepelev, Igor

    2013-01-01

    Recent seismic tomography studies image a low velocity zone (interpreted as a high temperature anomaly) in the mantle beneath the subducting Pacific plate near the Japanese islands at the depth of about 400 km. This thermal feature is rather peculiar in terms of the conventional view of mantle convection and subduction zones. Here we present a dynamic restoration of the thermal state of the mantle beneath this region assimilating geophysical, geodetic, and geological data up to 40 million years. We hypothesise that the hot mantle upwelling beneath the Pacific plate partly penetrated through the subducting plate into the mantle wedge and generated two smaller hot upwellings, which contributed to the rapid subsidence in the basins of the Japan Sea and to back-arc spreading. Another part of the hot mantle migrated upward beneath the Pacific lithosphere, and the presently observed hot anomaly is a remnant part of this mantle upwelling.

  1. Analysis of potability conditions of upwelling water in Ubá, MG

    Directory of Open Access Journals (Sweden)

    José Antonio Rodrigues de Souza

    2015-07-01

    Full Text Available In this work we investigated the interference of anthropic activities on the potability of groundwater in the urban area of the city of Ubá, MG. To accomplish this, the physical characteristics (temperature, turbidity and color, chemical (pH, conductivity, chloride, nitrate and hardness and microbiological (total and thermotolerant coliforms of ten upwelling waters were monitored throughout one year. The temperature, pH, color, chloride and hardness of all upwelling waters were considered normal compared to standards of potable water. However, the analyses of turbidity, electrical conductivity, nitrate and total and thermotolerant coliforms indicate contamination by human activities. Overall, the results indicated the occurrence of high environmental degradation, where only 30% of monitored upwelling waters were in accordance with the quality standard, indicating the need for intervention to ensure water quality.

  2. Topology of sustainable management of dynamical systems with desirable states: from defining planetary boundaries to safe operating spaces in the Earth System

    Science.gov (United States)

    Heitzig, Jobst; Kittel, Tim; Donges, Jonathan; Molkenthin, Nora

    2016-04-01

    To keep the Earth System in a desirable region of its state space, such as defined by the recently suggested "tolerable environment and development window", "guardrails", "planetary boundaries", or "safe (and just) operating space for humanity", one not only needs to understand the quantitative internal dynamics of the system and the available options for influencing it (management), but also the structure of the system's state space with regard to certain qualitative differences. Important questions are: Which state space regions can be reached from which others with or without leaving the desirable region? Which regions are in a variety of senses "safe" to stay in when management options might break away, and which qualitative decision problems may occur as a consequence of this topological structure? In this work, we develop a mathematical theory of the qualitative topology of the state space of a dynamical system with management options and desirable states, as a complement to the existing literature on optimal control which is more focussed on quantitative optimization and is much applied in both the engineering and the integrated assessment literature. We suggest a certain terminology for the various resulting regions of the state space and perform a detailed formal classification of the possible states with respect to the possibility of avoiding or leaving the undesired region. Our results indicate that before performing some form of quantitative optimization such as of indicators of human well-being for achieving certain sustainable development goals, a sustainable and resilient management of the Earth System may require decisions of a more discrete type that come in the form of several dilemmas, e.g., choosing between eventual safety and uninterrupted desirability, or between uninterrupted safety and larger flexibility. We illustrate the concepts and dilemmas drawing on conceptual models from climate science, ecology, coevolutionary Earth System modeling

  3. Trophic modeling of Eastern Boundary Current Systems: a review and prospectus for solving the “Peruvian Puzzle”

    Directory of Open Access Journals (Sweden)

    Marc H. Taylor

    2013-04-01

    Full Text Available Eastern Boundary Current systems (EBCSs are among the most productive fishing areas in the world. High primary and secondary productivity supports a large biomass of small planktivorous pelagic fish, “small pelagics”, which are important drivers of production to the entire system whereby they can influence both higher and lower trophic levels. Environmental variability causes changes in plankton (food quality and quantity, which can affect population sizes, distribution and domi-nance among small pelagics. This variability combined with impacts from the fishery complicate the development of management strategies. Consequently, much recent work has been in the development of multispecies trophic models to better understand interdependencies and system dynamics. Despite similarities in extent, structure and primary productivity between EBCSs, the Peruvian system greatly differs from the others in the magnitude of fish catches, due mainly to the incredible production of the anchovy Engraulis ringens. This paper reviews literature concerning EBCSs dynamics and the state-of-the-art in the trophic modeling of EBCSs. The objective is to critically analyze the potential of this approach for system understanding and management and to adapt existing steady-state models of the Peruvian system for use in (future dynamic simulations. A guideline for the construction of trophodynamic models is presented taking into account the important trophic and environmental interactions. In consideration of the importance of small pelagics for the system dynamics, emphasis is placed on developing appropriate model compartmentalization and spatial delineation that facilitates dynamic simulations. Methods of model validation to historical changes are presented to support hypotheses concerning EBCS dynamics and as a critical step to the development of predictive models. Finally, the identification of direct model links to easily obtainable abiotic parameters is

  4. Blurring Boundaries

    DEFF Research Database (Denmark)

    Neergaard, Ulla; Nielsen, Ruth

    2010-01-01

    ; and 3) Services of general interest. In the Blurring Boundaries project, three aspects of the European Social Model have been particularly highlighted: the constitutionalisation of the European Social Model, its multi-level legal character, and the clash between market access justice at EU level...... of welfare functions into EU law both from an internal market law and a constitutional law perspective. The main problem areas covered by the Blurring Boundaries project were studied in sub-projects on: 1) Internal market law and welfare services; 2) Fundamental rights and non-discrimination law aspects...... and distributive justice at national level....

  5. Mantle Plume Upwelling Rates: Evidence from U-Series in Young Ocean Island Basalts

    Science.gov (United States)

    Bourdon, B.; Turner, S. P.; Stracke, A.; Saal, A. E.

    2004-12-01

    U-series disequilibria measured in recent lavas at intraplate volcanoes provide a powerful probe to examine the validity of the plume model. U-Th and U-Pa fractionation produced during melting is a function of the melting rate. In turn, this parameter should scale with mantle upwelling velocities. Simply stated, a larger melting rate (larger mantle upwelling velocity) yields smaller Th and Pa excess relative to their parent nuclides. A number of observations supports this approach: (1) there is a negative correlation between 230Th excess and buoyancy fluxes (2) based on new measurements of 231Pa in the Azores, Iceland and the Galapagos and literature data, we show here that there is also a well defined correlation between 231Pa excess and buoyancy flux (3) For Hawaii, Iceland and the Azores, 230Th excess (or 231Pa excess) increases as a function of the distance from the centre of the `hotspot'. These observations suggests that `hotspot' buoyancy fluxes are associated with a greater melt production per unit of time and that the centre of `hotspot' corresponds to a faster mantle upwelling velocity than its periphery. This is therefore in strong support of a model where ocean islands are associated with faster upwelling at depth. However, there is in fact not a simple relationship between melt productivity and upwelling velocities. Notably, the presence of volatiles, of mafic lithologies or of variably enriched peridotitic source could all affect melting rate and hence U-Th-Pa fractionation. We have considered these issues in great detail using a large data base for the Azores islands. While there are clear variations in mantle source composition, they cannot explain the observations of increasing 231Pa/235U ratio with distance from the centre of the Azores hotspot . If we take into account the effect of water in the source of the Azores, it clearly affects the scaling between U-series fractionation and upwelling velocity but not the overall conclusions.

  6. Identification of variable coefficients for vibrating systems by boundary control and observation

    Institute of Scientific and Technical Information of China (English)

    Jinde CHANG

    2008-01-01

    We consider the identification problem of coefficients for vibrating systems described by a Euler-Bernoulli beam equation or a string equation,with one end clamped and with an input exerted on the other end.For the beam equation,the observations are the velocity and the angle velocity at the free end,While for the string equation,the observation is the velocity at the free end.In the framework of well-posed linear system theory,we show that both the density and the flexural rigidity of the beam,and the tension of the string,can be uniquely determined by the observations for all positive times.Moreover,a general constructive method is developed to show that the mass density and the elastic modulus of the string are not determined by the observation.

  7. Dynamics of ordering processes in annealed dilute systems: Island formation, vacancies at domain boundaries, and compactification

    DEFF Research Database (Denmark)

    Shah, Peter Jivan; Mouritsen, Ole G.

    1990-01-01

    with couplings leading to twofold-degenerate as well as fourfold-degenerate ordering. The models are quenched into a phase-separation region, which makes it possible for both types of ordering to observe the following scenario of ordering processes: (i) early-time nucleation and growth of ordered domains, (ii...... and compactification via coalescence. The domain-size distribution function, which is approximately log-normal, is shown to obey dynamical scaling over a substantial time range for both types of ordering. The growth for the pure systems is found to be described by a power law with the classical growth exponent n=1....... The results of the model study are relevant for the interpretation of experiments on ordering in impure systems and off-stochiometric alloys, grain growth in radiation-damaged materials, and may also shed light on aspects of sintering processes. The finding of a crossover from an algebraic growth law...

  8. Unmanned aircraft system measurements of the atmospheric boundary layer over Terra Nova Bay, Antarctica

    Directory of Open Access Journals (Sweden)

    S. L. Knuth

    2013-02-01

    Full Text Available In September 2009, a series of long-range unmanned aircraft system (UAS flights collected basic atmospheric data over the Terra Nova Bay polynya in Antarctica. Air temperature, wind, pressure, relative humidity, radiation, skin temperature, GPS, and operational aircraft data were collected and quality controlled for scientific use. The data have been submitted to the United States Antarctic Program Data Coordination Center (USAP-DCC for free access (doi:10.1594/USAP/0739464.

  9. Rocky Mountain Arsenal North Boundary Containment/Treatment System Operational Assessment Report for FY87

    Science.gov (United States)

    1988-11-01

    distribucions did not cnange significantly over the two year period. Maximum contaminant concentrations were found in the area during each sampling...offpost wells indicate that DIMP and DBCP concen- trations in the offpost area downgradient of NBS have declined since 1978. Contaminant Concentration in...concentrations of contaminants are generally found along the western half of the control system ii in the area of the original NBS. In general, the contaminant

  10. BOUNDS FOR SOLUTIONS OF A SYSTEM OF LINEAR PARTIAL DIFFERENTIAL EQUATIONS ON DOMAINS WITH BERGMAN-SILOV BOUNDARY,

    Science.gov (United States)

    PARTIAL DIFFERENTIAL EQUATIONS , THEORY), (*COMPLEX VARIABLES, PARTIAL DIFFERENTIAL EQUATIONS ), FUNCTIONS(MATHEMATICS), BOUNDARY VALUE PROBLEMS, INEQUALITIES, TRANSFORMATIONS (MATHEMATICS), TOPOLOGY, SET THEORY

  11. Anomalous magnetoelastic behaviour near morphotropic phase boundary in ferromagnetic Tb1-xNdxCo2 system

    Science.gov (United States)

    Murtaza, Adil; Yang, Sen; Zhou, Chao; Chang, Tieyan; Chen, Kaiyun; Tian, Fanghua; Song, Xiaoping; Suchomel, Matthrew R.; Ren, Y.

    2016-08-01

    In this work, we report a morphotropic phase boundary (MPB) involved ferromagnetic system Tb1-xNdxCo2 and reveal the corresponding structural and magnetoelastic properties of this system. With high resolution synchrotron X-ray diffractometry, the crystal structure of the TbCo2-rich side is detected to be rhombohedral and that of NdCo2-rich side is tetragonal below their respective Curie temperatures TC. The MPB composition Tb0.35Nd0.65Co2 corresponds to the coexistence of the rhombohedral phase (R-phase) and tetragonal phase (T-phase). Contrary to previously reported MPB involved ferromagnetic systems, the MPB composition of Tb0.35Nd0.65Co2 shows minimum magnetization which can be understood as compensation of sublattice moments between the R-phase and the T-phase. Furthermore, magnetostriction of Tb1-xNdxCo2 decreases with increasing Nd concentration until x = 0.8 and then increases in the negative direction with further increasing Nd concentration; the optimum point for magnetoelastic properties lies towards the rhombohedral phase. Our work not only shows an anomalous type of ferromagnetic MPB but also provides an effective way to design functional materials.

  12. Evaluation of ERTS data for certain oceanographic uses. [upwelling, water circulation, and pollution in Great Lakes

    Science.gov (United States)

    Strong, A. E. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. Upwelling along the eastern shore of Lake Michigan was occurring during the 3 and 21 August 1973 visits by ERTS-1. The NOAA-2 VHRR thermal-IR data are being digitized for comparison. Early indications are that these upwellings induced a calcium carbonate precipitate to form in the surface waters. It is most pronounced in the MSS-4 channel. On the lake bottom this jell-like sediment is known as marl and adds to the eutrophication of the lake. This phenomenon may help to explain the varve-like nature of bottom cores that have been observed in the Great Lakes.

  13. The potential role of mass balance models for the management of upwelling ecosystems

    DEFF Research Database (Denmark)

    Jarre, Astrid

    1998-01-01

    Upwelling ecosystems are productive fishing grounds, contributing >30% to the world's catch of marine fish. A set of seven trophic mass balance models of productive subsystems of the four largest upwelling areas is used to demonstrate key features of the modeling process and the analysis...... set of species interactions, and its impact can thus be readily compared to that of other piscivores in the ecosystem. This approach consequently allows us to assess the ecological sustainability of a fishery. It therefore addresses the Code of Conduct for Responsible Fisheries recently published...

  14. Distribution of upwelling index planktonic foraminifera in the sediments of the western continental margin of India

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.

    has been found by Diester-Haass (1976) in the region of Cape Barbas, Northwestern Africa, where upwelling occurs through out tlie year. The correlation coefficient values for planktonic foram inifera with radiolarians shows a positive correlation: r.... Diester-Haass and J. S. Killingle)' (Inn Upwelling 01T North-West Africa: the Holocene decrease as seen in carhon , isotopes and sedimentological indicators. ()('('£//1ologim Actll. l. 1. 3- 17. I ·Colborn J. G. (1975). The thermal structure of the Indian...

  15. Larval fish assemblages across an upwelling front: Indication for active and passive retention

    Science.gov (United States)

    Tiedemann, Maik; Brehmer, Patrice

    2017-03-01

    In upwelling areas, enrichment, concentration and retention are physical processes that have major consequences for larval fish survival. While these processes generally increase larval survival, strong upwelling can also increase mortality due to an offshore transport of larvae towards unfavorable habitats. In 2013 a survey was conducted along the Senegalese coast to investigate the upwelling effect with regard to larval fish assemblages and possible larval fish retention. According to water column characteristics two distinct habitats during an upwelling event were discriminated, i.e. the inshore upwelled water and the transition area over the deepest part of the Senegalese shelf. Along the two areas 42,162 fish larvae were collected representing 133 species within 40 families. Highest larval fish abundances were observed in the inshore area and decreasing abundances towards the transition, indicating that certain fish species make use of the retentive function of the inner shelf area as spawning grounds. Two larval fish assemblages overlap both habitats, which are sharply delimited by a strong upwelling front. One assemblage inhabited the inshore/upwelling area characterized by majorly neritic and pelagic species (Sparidae spp., Sardinella aurita), that seem to take the advantage of a passive retention on the shelf. The second assemblage consisted of a mix of pelagic and mesopelagic species (Engraulis encrasicolus, Carangidae spp. and Myctophidae spp.). Some species of the second assemblage, e.g. horse mackerels (Trachurus trachurus and Trachurus trecae), large finned-lantern fish (Hygophum macrochir) and foureyed sole (Microchirus ocellatus), revealed larval peak occurrences at intermediate and deep water layers, where the near-ground upwelling layer is able to transport larvae back to the shelf. This indicates active larval retention for species that are dominant in the transition area. Diel vertical migration patterns of S. aurita, E. encrasicolus and M

  16. The Atlantic Water boundary current in the Nansen Basin: Transport and mechanisms of lateral exchange

    Science.gov (United States)

    Vâge, Kjetil; Pickart, Robert S.; Pavlov, Vladimir; Lin, Peigen; Torres, Daniel J.; Ingvaldsen, Randi; Sundfjord, Arild; Proshutinsky, Andrey

    2016-09-01

    Data from a shipboard hydrographic survey near 30°E in the Nansen Basin of the Arctic Ocean are used to investigate the structure and transport of the Atlantic Water boundary current. Two high-resolution synoptic crossings of the current indicate that it is roughly 30 km wide and weakly middepth-intensified. Using a previously determined definition of Atlantic Water, the transport of this water mass is calculated to be 1.6 ± 0.3 Sv, which is similar to the transport of Atlantic Water in the inner branch of the West Spitsbergen Current. At the time of the survey a small anticyclonic eddy of Atlantic Water was situated just offshore of the boundary current. The data suggest that the feature was recently detached from the boundary current, and, due to compensating effects of temperature and salinity on the thermal wind shear, the maximum swirl speed was situated below the hydrographic property core. Two other similar features were detected within our study domain, suggesting that these eddies are common and represent an effective means of fluxing warm and salty water from the boundary current into the interior. An atmospheric low-pressure system transiting south of our study area resulted in southeasterly winds prior to and during the field measurements. A comparison to hydrographic data from the Pacific Water boundary current in the Canada Basin under similar atmospheric forcing suggests that upwelling was taking place during the survey. This provides a second mechanism related to cross-stream exchange of heat and salt in this region of the Nansen Basin.

  17. Effect of non-heterogeneous wetwell boundaries on pressure suppression system response. [BWR

    Energy Technology Data Exchange (ETDEWEB)

    McCauley, E.W.; Holman, G.S.; Namatame, K.; Kukita, Y.; Shiba, M.

    1980-08-29

    The Full-Scale Mark II CRT (Containment Response Test) Program is in progress at the Tokai-Mura Establishment of the Japan Atomic Energy Research Institute (JAERI). The primary objective of the on-going CRT Program is to provide a data base for evaluation of the pressure suppression pool (wetwell) hydrodynamic loads associated with a postulated loss-of-coolant accident (LOCA) in the BWR Mark II containment system. The test facility is 1/18 of full scale in volume and has a wetwell which is a full-scale geometric replica of one 20/sup 0/-sector of a reference 1100MWe Mark II.

  18. Unmanned aircraft system measurements of the atmospheric boundary layer over Terra Nova Bay, Antarctica

    Directory of Open Access Journals (Sweden)

    S. L. Knuth

    2012-11-01

    Full Text Available In September 2009, a series of long-range unmanned aircraft system (UAS flights collected basic atmospheric data over the Terra Nova Bay polynya in Antarctica. Air temperature, wind, pressure, relative humidity, radiation, skin temperature, GPS, and operational aircraft data were collected and quality controlled for scientific use. The data has been submitted to the United States Antarctic Program Data Coordination Center (USAP-DCC for free access (doi:10.1594/USAP/0739464.

  19. Blurring Boundaries

    DEFF Research Database (Denmark)

    Neergaard, Ulla; Nielsen, Ruth

    2010-01-01

    This article builds on the results obtained in the so-called Blurring Boundaries project which was undertaken at the Law Department, Copenhagen Business School, in the period from 2007 to 2009. It looks at the sustainability of the Danish welfare state in an EU law context and on the integration ...

  20. Negotiating boundaries

    DEFF Research Database (Denmark)

    Aarhus, Rikke; Ballegaard, Stinne Aaløkke

    2010-01-01

    To move treatment successfully from the hospital to that of technology assisted self-care at home, it is vital in the design of such technologies to understand the setting in which the health IT should be used. Based on qualitative studies we find that people engage in elaborate boundary work to ...