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  • Springer  (135,292)
  • Copernicus  (9,615)
  • American Chemical Society (ACS)
  • American Meteorological Society
  • 2015-2019  (108,707)
  • 2000-2004  (39,745)
  • 1980-1984
  • 1970-1974
  • 1960-1964
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  • 2019  (108,707)
  • 2004  (39,745)
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  • 2015-2019  (108,707)
  • 2000-2004  (39,745)
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  • 1960-1964
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  • 1
    Keywords: communication ; design ; dynamics ; environment ; network ; physics ; power transmission ; radio ; satellite ; simulation ; technology ; transmission
    Description / Table of Contents: The 17 chapters of this book grew out of the tutorial lectures given by leading world-class experts at the NATO Advanced Research Workshop “Effects of Space Weather on Technology Infrastructure” - ESPRIT, which was held in Rhodes on March 25-29, 2004. All manuscripts were refereed and subsequently meticulously edited by the editor to ensure the highest quality for this monograph. I owe particular thanks to the lecturers of the ESPRIT Advanced Research Workshop for producing these excellent tutorial reviews, which convey the essential knowledge and the latest advances in our field. Due to the breadth, extensive literature citations and quality of the reviews we expect this publication to serve extremely well as a reference book. Multimedia material referring to individual chapters of the book is accessible on the accompanying CD. The aim of ESPRIT was to assess existing knowledge and identify future actions regarding monitoring, forecasting and mitigation of space weather induced malfunction and damage of vital technological systems operating in space and on the ground.
    ISBN: 9781402027543
    Language: English
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  • 2
    Description / Table of Contents: Prof. Dr. -Ing. Wolfgang Spyra Brandenburg University of Technology in Cottbus, Germany The demilitarization and conversion of military properties wor- wide has been a topic of growing importance since the end of the Cold War. The slowing of the arms race brought on by weapons treaties and relaxed tensions between NATO and Warsaw Pact nations caused sto- piles of conventional weapons to become superfluous. The need to process and dispose of such weapons began more quickly in NATO countries. This demilitarization process began shortly after the reunification of Germany and was largely completed by the mid to late 1990’s. The remaining process, no small task in itself, of converting lands formerly used by the military into safe and environmentally acceptable landscapes may continue for decades to come. Due to a lack of resources and technology, the process of demilitarization in the former Warsaw Pact countries has launched more slowly. In 2002 both Georgia and Moldova finished projects which destroyed their stocks of liquid ballistic missile components. Both these projects were carried out through the cooperative support of trans-national organizations, private contractors, and research institutions. The Republic of Azerbaijan now finds itself at the beginning of its demilitarization process. Stored at the country’s military depots are over 2000 tons of missile fuels, oxidizer, and chemical additives. This hazardous waste is kept in tanks intended only for temporary transport and storage.
    Pages: Online-Ressource (X, 148 pages)
    ISBN: 9781402023811
    Language: English
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  • 3
    Unknown
    London ; New York : Springer
    Decision engineering  
    Keywords: Decision making, Mathematical models. ; Decision making, Methodology.
    Pages: ix, 172 p.
    ISBN: 1-85233-864-4
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  • 4
    Keywords: Semantic Web, Congresses.
    Pages: x, 145 p.
    ISBN: 3-540-25982-1
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  • 5
    Publication Date: 2020-10-22
    Description: The storage concession "Minerbio Stoccaggio" (Bologna, Northern Italy) covers a 69 km 2 area, 65% of hich is located in the Minerbio municipality. Since 1979, a microseismic network for the monitoring of seismicity, eventually induced by gas storage activities, has been installed in this area. The network was operated by Stogit S.p.A, a subsidiary company of Snam, which is the largest storage operator in Italy. In 2016, the microseismic network, consisting of three surface stations and one 100-m-deep borehole sensor with minimum interstation distances of about 3.0 km, was integrated with 12 regional stations installed in an 80 × 80 km 2 area centered on the surface projection of the reservoir. In 2018, the microseismic network was enhanced by adding one surface and three 150-m-deep borehole stations. In this work, we evaluate the detection improvement of the microseismic network, integrated with the regional stations. We define two crustal volumes for earthquake detection: the inner domain of detection, IDD (10 × 10 × 5) km 3 , within which we should ensure the highest network performance, and the extended domain of detection, EDD (22 × 22 × 11) km 3 . By comparing the simulated power spectral density of hypothetical seismic sources located in EDD with the average power spectra of ambient seismic noise observed at each station site, we calculate detection and localization thresholds for the two above-mentioned networks. Under unfavourable noise conditions, we find that the present operative seismic network allows locating earthquakes with M L ≥ 0.8 occurring at the depth of the reservoir and with M L ≥ 1.0 if located within IDD.
    Description: Funding information This study received financial support from BComune di Minerbio^ under the grant BSperimentazione ILG Minerbio^ (grant number 0913.010)
    Description: Published
    Description: 967–977
    Description: 3SR TERREMOTI - Attività dei Centri
    Description: JCR Journal
    Keywords: Induced seismicity ; Earthquake detection ; Ambient seismic noise ; Microseismic monitoring ; MiSE ; oilfield monitoring guidelines
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
    Publication Date: 2020-09-07
    Description: This paper presents an original multidisciplinary (geological-structural-geomorphological and seismological) study aimed at investigating the origin of diffused seismic damages affecting several ancient buildings in the Roman port city of Ostia. We also evaluate the possibility to relate these damages to a previously hypothesized ENE-WSW trending fault, bordering the morphological height upon which the Ostia town was founded. Aimed at this scope, we performed seismic noise measures (by using 14 seismic stations) that show no significantly different response and lack of significant ground motion differential amplifications. The coexistence of (i) no local geological heterogeneities and (ii) low amplification of spectral ratios in the recorded seismic signals seems to exclude that the observed seismic damage may be the consequence of significant site effects. When also the large distance from the strongest Apennine’s seismogenic source areas is considered, the possibility that the observed damage may be the consequence of local events should be considered. We discuss the potentiality of the ENE-WSW trending fault as the source of the observed seismic damages, highlighting the supporting evidence as well as the uncertainties of such interpretation.
    Description: Published
    Description: 833–851
    Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 7
    Publication Date: 2020-09-07
    Description: This work describes the analysis of the strong-motion data from the Engineering Strong Motion database (ESM, http://esm.mi.ingv.it), aimed at: (1) extract a dataset of accelero- metric waveforms recorded during the 2016–2017 Central Italy seismic sequence; (2) iden- tify the recording stations to be used as reference sites for further seismological analysis; (3) select the records to be used as input for seismic microzonation of higher level at 137 municipalities. Firstly, a residual analysis is carried out on the extracted dataset to perform: (1) the quality check of the waveforms recorded by temporary networks installed soon after the occurrence of the rst main shock (M 6.0, 24 August 2016); (2) the estimation of the site-to-site residual term for each recording station with the aim of recognising potential reference rock sites. Finally, the software REXELite, integrated within the ESM website, is adopted to select suites of spectrum-compatible accelerograms, that will be used as input for calculating site ampli cations through 1D and 2D simulations at sites which suf- fered the greatest damage. The results of this work demonstrate the success of the synergy among Italian institutions. The setup of key infrastructures, such as emergency networks and data repositories, together with the knowledge developed during national projects, turned out to be successful in terms of timely intervention during the emergency phase and the planning of the post-emergency.
    Description: Published
    Description: 5533–5551
    Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
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    Copernicus
    In:  EPIC3Earth System Science Data Discussions https://doi.org/10.5194/essd-2019-66, Copernicus, pp. 1-39
    Publication Date: 2019-05-02
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , notRev
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  • 9
    Publication Date: 2019-04-10
    Description: Our knowledge on distribution, habitats and behavior of Southern Ocean fishes living at water depths beyond scuba-diving limits is still sparse, as it is difficult to obtain quantitative data on these aspects of their biology. Here, we report the results of an analysis of seabed images to investigate species composition, behavior, spatial distribution and preferred habitats of demersal fish assemblages in the southern Weddell Sea. Our study was based on a total of 2736 high-resolution images, covering a total seabed area of 11,317 m2, which were taken at 13 stations at water depths between 200 and 750 m. Fish were found in 380 images. A total of 379 notothenioid specimens were recorded, representing four families (Nototheniidae, Artedidraconidae, Bathydraconidae, Channichthyidae), 17 genera and 25 species. Nototheniidae was the most speciose fam- ily, including benthic species (Trematomus spp.) and the pelagic species Pleuragramma antarctica, which was occasionally recorded in dense shoals. Bathydraconids ranked second with six species, followed by artedidraconids and channichthyids, both with five species. Most abundant species were Trematomus scotti and T. lepidorhinus among nototheniids, and Dol- loidraco longedorsalis and Pagetopsis maculatus among artedidraconids and channichthyids, respectively. Both T. lepi- dorhinus and P. maculatus preferred seabed habitats characterized by biogenous debris and rich epibenthic fauna, whereas T. scotti and D. longedorsalis were frequently seen resting on fine sediments and scattered gravel. Several fish species were recorded to make use of the three-dimensional structure formed by epibenthic foundation species, like sponges, for perching or hiding inside. Nesting behavior was observed, frequently in association with dropstones, in species from various families, including Channichthyidae (Chaenodraco wilsoni and Pagetopsis macropterus) and Bathydraconidae (Cygnodraco mawsoni).
    Repository Name: EPIC Alfred Wegener Institut
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  • 10
    Publication Date: 2020-01-21
    Description: A new 21.3m firn core was drilled in 2015 at a coastal Antarctic high-accumulation site in Adélie Land (66.78◦ S; 139.56◦ E, 602 m a.s.l.), named Terre Adélie 192A (TA192A). The mean isotopic values (−19.3 ‰ ± 3.1 ‰ for δ18O and 5.4 ‰±2.2 ‰ for deuterium excess) are consistent with other coastal Antarctic values. No significant isotope–temperature relationship can be evidenced at any timescale. This rules out a simple interpretation in terms of local temperature. An observed asymmetry in the δ18O seasonal cycle may be explained by the precipitation of air masses coming from the eastern and western sectors in autumn and winter, recorded in the d-excess signal showing outstanding values in austral spring versus autumn. Significant positive trends are observed in the annual d-excess record and local sea ice extent (135–145◦ E) over the period 1998–2014. However, process studies focusing on resulting isotopic compositions and particularly the deuterium excess–δ18O relationship, evidenced as a potential fingerprint of moisture origins, as well as the collection of more isotopic measurements in Adélie Land are needed for an accurate interpretation of our signals.
    Repository Name: EPIC Alfred Wegener Institut
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  • 11
    Publication Date: 2019-08-12
    Repository Name: EPIC Alfred Wegener Institut
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  • 12
    Publication Date: 2020-03-01
    Repository Name: EPIC Alfred Wegener Institut
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  • 13
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    Springer
    In:  EPIC3The Ecosystem of Kongsfjorden, Svalbard, The Ecosystem of Kongsfjorden, Svalbard, Cham, Springer, 566 p., pp. 537-562, ISBN: 978-3-319-46425-1
    Publication Date: 2020-07-08
    Description: Due to its year-round accessibility and excellent on-site infrastructure, Kongsfjorden and the Ny-Ålesund Research and Monitoring Facility have become established as a primary location to study the impact of environmental change on Arctic coastal ecosystems. Due to its location right at the interface of Arctic and Atlantic oceanic regimes, Kongsfjorden already experiences large amplitudes of variability in physico/chemical conditions and might, thus, be considered as an early warning indicator of future changes, which can then be extrapolated in a pan-Arctic perspective. Already now, Kongsfjorden represents one of the best-studied Arctic fjord systems. However, research conducted to date has concentrated largely on small disciplinary projects, prompting the need for a higher level of integration of future research activities. This contribution, thus, aims at identifying gaps in knowledge and research priorities with respect to ecological and adaptive responses to Arctic ecosystem changes. By doing so we aim to provide a stimulus for the initiation of new international and interdisciplinary research initiatives.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Inbook , peerRev
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  • 14
    Publication Date: 2020-07-10
    Description: The timing and intensity of snowmelt processes on sea ice are key drivers determining the seasonal sea-ice energy and mass budgets. In the Arctic, satellite passive microwave and radar observations have revealed a trend towards an earlier snowmelt onset during the last decades, which is an important aspect of Arctic amplification and sea ice decline. Around Antarctica, snowmelt on perennial ice is weak and very different than in the Arctic, with most snow surviving the summer. Here we compile time series of snowmelt-onset dates on seasonal and perennial Antarctic sea ice from 1992 to 2014/15 using active microwave observations from European Remote Sensing Satellite (ERS-1/2), Quick Scatterometer (QSCAT) and Advanced Scatterometer (ASCAT) radar scatterometers. We define two snowmelt transition stages: A weak backscatter rise indicating the initial warming and destructive metamorphism of the snowpack (pre-melt), followed by a rapid backscatter rise indicating the onset of thaw-freeze cycles (snowmelt). Results show large interannual variability with an average pre-melt onset date of 29 November and melt onset of 10 December, respectively, on perennial ice, without any significant trends over the study period, consistent with the small trends of Antarctic sea ice extent. There was a latitudinal gradient from early snowmelt onsets in mid-November in the northern Weddell Sea to late (end-December) or even absent snowmelt conditions in the southern Weddell Sea. We show that QSCAT Ku-band (13.4 GHz signal frequency) derived pre-melt and snowmelt onset dates are earlier by 20 and 18 days, respectively, than ERS and ASCAT C-band (5.6 GHz) derived dates. This offset has been considered when constructing the time series. Snowmelt onset dates from passive microwave observations (37 GHz) are later by 14 and 6 days than those from the scatterometers, respectively. Based on these characteristic differences between melt onset dates observed by different microwave wavelengths, we developed a conceptual model which illustrates how the seasonal evolution of snow temperature profiles may affect different microwave bands with different penetration depths. These suggest that future multi-frequency active/passive microwave satellite missions could be used to resolve melt processes throughout the vertical snow column of thick snow on perennial Antarctic sea ice.
    Repository Name: EPIC Alfred Wegener Institut
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  • 15
    Publication Date: 2020-01-27
    Description: Although quantitative isotope data from speleothems has been used to evaluate isotope-enabled model simulations, currently no consensus exists regarding the most appropriate methodology through which to achieve this. A number of modelling groups will be running isotope-enabled palaeoclimate simulations in the framework of the Coupled Model Intercomparison Project Phase 6, so it is timely to evaluate different approaches to using the speleothem data for data–model comparisons. Here, we illustrate this using 456 globally distributed speleothem δ18O records from an updated version of the Speleothem Isotopes Synthesis and Analysis (SISAL) database and palaeoclimate simulations generated using the ECHAM5-wiso isotope-enabled atmospheric circulation model. We show that the SISAL records reproduce the first-order spatial patterns of isotopic variability in the modern day, strongly supporting the application of this dataset for evaluating model-derived isotope variability into the past. However, the discontinuous nature of many speleothem records complicates the process of procuring large numbers of records if data–model comparisons are made using the traditional approach of comparing anomalies between a control period and a given palaeoclimate experiment. To circumvent this issue, we illustrate techniques through which the absolute isotope values during any time period could be used for model evaluation. Specifically, we show that speleothem isotope records allow an assessment of a model’s ability to simulate spatial isotopic trends. Our analyses provide a protocol for using speleothem isotope data for model evaluation, including screening the observations to take into account the impact of speleothem mineralogy on δ18O values, the optimum period for the modern observational baseline and the selection of an appropriate time window for creating means of the isotope data for palaeo-time-slices.
    Repository Name: EPIC Alfred Wegener Institut
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  • 16
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    Copernicus
    In:  EPIC3Climate of the Past, Copernicus, 15(6), pp. 1913-1937, ISSN: 1814-9332
    Publication Date: 2020-01-27
    Description: We present here the first results, for the preindustrial and mid-Holocene climatological periods, of the newly developed isotope-enhanced version of the fully coupled Earth system model MPI-ESM, called hereafter MPI-ESM-wiso. The water stable isotopes H16O, H18O and HDO have been implemented into all components of the coupled model setup. The mid-Holocene provides the opportunity to evaluate the model response to changes in the seasonal and latitudinal distribution of insolation induced by different orbital forcing conditions. The results of our equilibrium simulations allow us to evaluate the performance of the isotopic model in simulating the spatial and temporal variations of water isotopes in the different compartments of the hydrological system for warm climates. For the preindustrial climate, MPI-ESM-wiso reproduces very well the observed spatial distribution of the isotopic content in precipitation linked to the spatial variations in temperature and precipitation rate. We also find a good model–data agreement with the observed distribution of isotopic composition in surface seawater but a bias with the presence of surface seawater that is too 18O-depleted in the Arctic Ocean. All these results are improved compared to the previous model version ECHAM5/MPIOM. The spatial relationships of water isotopic composition with temperature, precipitation rate and salinity are consistent with observational data. For the preindustrial climate, the interannual relationships of water isotopes with temperature and salinity are globally lower than the spatial ones, consistent with previous studies. Simulated results under mid-Holocene conditions are in fair agreement with the isotopic measurements from ice cores and continental speleothems. MPI-ESM-wiso simulates a decrease in the isotopic composition of precipitation from North Africa to the Tibetan Plateau via India due to the enhanced monsoons during the mid-Holocene. Over Greenland, our simulation indicates a higher isotopic composition of precipitation linked to higher summer temperature and a reduction in sea ice, shown by positive isotope–temperature gradient. For the Antarctic continent, the model simulates lower isotopic values over the East Antarctic plateau, linked to the lower temperatures during the mid-Holocene period, while similar or higher isotopic values are modeled over the rest of the continent. While variations of isotopic contents in precipitation over West Antarctica between mid-Holocene and preindustrial periods are partly controlled by changes in temperature, the transport of relatively 18O-rich water vapor near the coast to the western ice core sites could play a role in the final isotopic composition. So, more caution has to be taken about the reconstruction of past temperature variations during warm periods over this area. The coupling of such a model with an ice sheet model or the use of a zoomed grid centered on this region could help to better describe the role of the water vapor transport and sea ice around West Antarctica. The reconstruction of past salinity through isotopic content in sea surface waters can be complicated for regions with strong ocean dynamics, variations in sea ice regimes or significant changes in freshwater budget, giving an extremely variable relationship between the isotopic content and salinity of ocean surface waters over small spatial scales. These complicating factors demonstrate the complexity of interpreting water isotopes as past climate signals of warm periods like the mid-Holocene. A systematic isotope model intercomparison study for further insights on the model dependency of these results would be beneficial.
    Repository Name: EPIC Alfred Wegener Institut
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  • 17
    Publication Date: 2019-11-26
    Description: Modern Society needs interactive public discussion to provide an effective way of focusing on hydrological hazards and their consequences. Embracing a holistic Earth system Science approach, we experiment since 2004 different stimulating educational/communicative model which emotionally involves the participants to raise awareness on the social dimension of the disaster hydrogeological risk reduction, pointing out that human behavior is the crucial factor in the degree of vulnerability and the likelihood of disasters taking place. The implementation of strategies for risk mitigation must include educational aspects, as well as economical and societal ones. Education is the bridge between knowledge and understanding and the key to raise risk perception. Children’s involvement might trigger a chain reaction that reinforce and spread the culture of risk. No matter how heavy was the rain that hit our land in the past and recent seasons, we still are not prepared. If on one hand we need to fight against worsening Global Warming that trigger extreme meteorological events, we should also work on sustainable land use and promote landscape preservation. Since science can work on improving knowledge of phenomena, technology can provide modern tool to reduce the impact of disasters, children and adults education is the flywheel to provide the change. We present here two cases selected among the wide range of educational activities that we have tested and to which more than 2,000 students and adults have participated within a period of 12 years. They include learn-by-playing, hands-on, emotional-learning activities, open questions seminars, learning paths, curiosity-driven approaches, special venues and science outreach.
    Description: Sendai Partnerships 2015-2025
    Description: Published
    Description: Ljubljana (Slovenia)
    Description: 2TM. Divulgazione Scientifica
    Keywords: Natural hazard ; Hydrogeological risk ; Prevention ; Participatory approach ; Awareness raising ; Resilience ; Hydrogeological Risk prevention
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Conference paper
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  • 18
    Publication Date: 2020-03-23
    Description: The systematic study of biological basis of behavior and of the process involved in economical choices has outlined a new paradigm of research: neuroeconomics. Now the intersection between neuroscience, psychology and economics, neuroeconomics presents itself as an alternative to the neoclassical vision on economics, according to which the homo oeconomicus acts within the bonds of a formalizing rationality tending to the maximization of the anticipated utility. Brain imagining methods have shown that the decision-making processes activate the frontal lobe and the limbic system above all, a big circonvolution running through the callous body on the medial surface of the hemispheres, extending itself down, responsible for the regulation of emotional phenomena. Reinforcing such a tendency, we find the injury paradigm. It was observed that frontal lobe injuries harm the capacity of making advantageous decisions either in one’s own behalf or in others, as well as decisions according to the social conventions. In this paper, we will try to show that if, by the one hand, the neuro visual methods have given us a great amount of data, on the other hand, using them uncritically, with the recurrent confusion between “correlation” and “causal relation”—contemporary microevents indicate only simple correlations, and no cause-effect relation—risks to stress the relevant explanatory gap regarding the abstract ideal of understanding the nature of the brain.
    Description: Published
    Description: 135-141
    Description: 2TM. Divulgazione Scientifica
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 19
    Publication Date: 2019-03-11
    Description: This paper investigates whether and how depressive disorders affect speech and in particular timing strategies for speech pauses (empty and filled pauses, as well as, phoneme lengthening). The investigation is made exploiting read and spontaneous narratives . The collected data are from 24 subjects, divided into two groups (depressed and control) asked to read a tale, as well as, spontaneously report on their daily activities. Ten different frequency and duration measures for pauses and clauses are proposed and have been collected using the PRAAT software on the speech recordings produced by the participants. A T-Student test for independent samples was applied on the collected frequency and duration measures in order to ascertain whether significant differences between healthy and depressed speech measures are observed. In the “spontaneous narrative” condition, depressed patients exhibited significant differences in: the average duration of their empty pauses, the average frequency, and the average duration of their clauses. In the read narratives, only the average pause’s frequency of the clauses was significantly lower in the depressed subjects with respect to the healthy ones. The results suggest that depressive disorders affect speech quality and speech production through pause and clause durations, as well as, clause quantities. In particular, the significant differences in clause quantities (observed both in the read and spontaneous narratives), suggest a strong general effect of depressive symptoms on cognitive and psychomotor functions. Depressive symptoms produce changes in the planned timing of pauses, even when reading, modifying the timing of pausing strategies.
    Description: Published
    Description: 73-82
    Description: 5TM. Informazione ed editoria
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 20
    Publication Date: 2019-04-01
    Description: t The role of riverine freshwater inflow on the Central Mediterranean Overturning Circulation (CMOC) was studied using a high-resolution ocean model with a complete distribution of rivers in the Adriatic and Ionian catchment areas. The impact of river runoff on the Adriatic and Ionian Sea basins was assessed by a twin experiment, with and without runoff, from 1999 to 2012. This study tries to show the connection between the Adriatic as a marginal sea containing the downwelling branch of the anti-estuarine CMOC and the large runoff occurring there. It is found that the multiannual CMOC is a persistent anti-estuarine structure with secondary estuarine cells that strengthen in years of large realistic river runoff. The CMOC is demonstrated to be controlled by wind forcing at least as much as by buoyancy fluxes. It is found that river runoff affects the CMOC strength, enhancing the amplitude of the secondary estuarine cells and reducing the intensity of the dominant anti-estuarine cell. A large river runoff can produce a positive buoyancy flux without switching off the antiestuarine CMOC cell, but a particularly low heat flux and wind work with normal river runoff can reverse it. Overall by comparing experiments with, without and with unrealistically augmented runoff we demonstrate that rivers affect the CMOC strength but they can never represent its dominant forcing mechanism and the potential role of river runoff has to be considered jointly with wind work and heat flux, as they largely contribute to the energy budget of the basin. Looking at the downwelling branch of the CMOC in the Adriatic basin, rivers are demonstrated to locally reduce the volume of Adriatic dense water formed in the Southern Adriatic Sea as a result of increased water stratification. The spreading of the Adriatic dense water into the Ionian abyss is affected as well: dense waters overflowing the Otranto Strait are less dense in a realistic runoff regime, with respect to no runoff experiment, and confined to a narrower band against the Italian shelf with less lateral spreading toward the Ionian Sea center. 1
    Description: Published
    Description: 1675-1703
    Description: 4A. Oceanografia e clima
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 21
    Publication Date: 2019-03-27
    Description: The first in situ measurements of seawater density that referred to a geographical position at sea and time of the year were carried out by Count Luigi Ferdinando Marsili between 1679 and 1680 in the Adriatic Sea, Aegean Sea, Marmara Sea, and the Bosporus. Not only was this the first investigation with documented oceanographic measurements carried out at stations, but themeasurements were described in such an accurateway that the authorswere able to reconstruct the observations in modern units. These first measurements concern the ‘‘specific gravity’’ of seawaters (i.e., the ratio between fluid densities). The data reported in the historical oceanographic treatise Osservazioni intorno al Bosforo Tracio (Marsili) allowed the reconstruction of the seawater density at different geographic locations between 1679 and 1680. Marsili’s experimental methodology included the collection of surface and deep water samples, the analysis of the samples with a hydrostatic ampoule, and the use of a reference water to standardize the measurements.Acomparison of reconstructed densities with present-day values shows an agreement within 10%–20% uncertainty, owing to various aspects of the measurement methodology that are difficult to reconstruct from the documentary evidence. Marsili also measured the current speed and the depth of the current inversion in the Bosporus, which are consistent with the present-day knowledge. The experimental data collected in the Bosporus enabledMarsili to enunciate a theory on the cause of the two-layer flow at the strait, demonstrated by his laboratory experiment and later confirmed by many analytical and numerical studies.
    Description: American Meteorological Society.
    Description: Published
    Description: 845 - 860
    Description: 4A. Oceanografia e clima
    Description: JCR Journal
    Keywords: Ocean ; Density currents ; Measurements ; Ship observations
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 22
    Publication Date: 2019-03-11
    Description: Humans have very high requirements and expectations when communicating through speech, other than simplicity, flexibility and easiness of interaction. This is because voice interactions do not require cognitive efforts, attention, and memory resources. Voice technologies are however still constrained to use cases and scenarios giving the existing limitations of speech synthesis and recognition systems. Which is the status of nonlinear speech processing techniques and the steps made for cross-fertilization among disciplines? This chapter will provide a short overview trying to answer the above question.
    Description: Published
    Description: 5-11
    Description: 5TM. Informazione ed editoria
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 23
    Publication Date: 2019-12-09
    Description: Since the past decade, geodetic techniques are widely used to gain important information for the monitoring and modeling of the deformation of the Earth at different length and time scales. Although the GNSS derived estimates of the Earth crust velocity are becoming more and more reliable, advanced data analysis techniques are needed to recognize geophysical features in the GNSS time-series, e.g., non linear behaviors, discontinuities in the signal and in its derivative, i.e., in the velocity. Unfortunately these phenomena are often hidden in the time-series noise and external information, as seismic events, are not always known. The main focus of this work is the detection of signal discontinuities in GNSS time-series through the use of advanced analysis techniques: the wavelets, the Bayesian and the variational methods. The Mumford and Shah (Commun Pure Appl Math 42:577–685, 1989) and the Blake and Zisserman (Visual reconstruction, 1987) variational models for signal segmentation can detect signal discontinuities in an explicitly way. The Blake and Zisserman (Visual reconstruction, 1987) model can also detect discontinuities of the signal first derivative, i.e., velocity abrupt changes can be detected. At first, to prove and assess the capability to detect discontinuities correctly, the methods have been applied to some Cascadia (North America) time-series, characterized by well known aseismic deformations. A second test area has been taken into account: the Calabrian Arc subduction zone, in southern Italy. The analyzed Italian GNSS time-series are characterized by very weak and noisy signals and the geodynamic of the area is mostly unknown. When present, discontinuities are expected to be very small and compatible with the signal noise. This motivates the use of advanced data analysis techniques to investigate the presence of discontinuities. At the moment, the analysis of the Italian time-series has revealed several discontinuities which nature cannot be labeled easily as geophysical or geodetic.
    Description: Published
    Description: 627-634
    Description: 2T. Deformazione crostale attiva
    Keywords: Subduction Zone ; Discontinuity point ; Slow slip event ; signal discontinuity ; Cascadia Subduciton zone
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 24
    Publication Date: 2019-12-02
    Description: Algorithms based on artificial intelligence (AI) have had a strong development in recent years in different research fields of earth science such as seismology and volcanology. In particular, they have been applied to the study of the volcanic eruptive products of the recent activity of Mount Etna volcano. This work presents an application of the self-organizing map (SOM) neural networks to perform a clustering analysis on petrographic patterns of rocks of Somma–Vesuvius and Campi Flegrei volcanoes, in the Neapolitan area. The goal is to highlight possible affinity between the magmatic reservoirs of these two volcanic complexes. The SOM is known for its ability to cluster data by using intrinsic similarity measures without any previous information about their distribution. Moreover, it allows an easy understandable data visualization by using a two-dimensional map. The SOM has been tested on a geochemical dataset of 271 samples, consisting of 134 samples of Campi Flegrei eruptions (named CF), 24 samples of Somma–Vesuvius effusive eruptions (VF), 73 samples of Somma–Vesuvius explosive eruptions (VX), and finally 40 samples of “foreign” eruptions (ET), included to verify the neural net classification capability. After a pre-processing phase, applied to have a more appropriate data representation as input for the SOM, each sample has been encoded through a vector of 23 features, containing information about major bulk components, trace elements, and Sr isotopic ratio. The resulting SOM identifies three main clusters, and in particular, the foreign patterns (ET) are well separated from the other ones being mainly grouped in a single node. In conclusion, the obtained results suggest the ability of SOM neural network to associate volcanic rock suites on the basis of their geochemical imprint and can be consistent with the hypothesis that there might be a common magma source beneath the whole Neapolitan area.
    Description: Published
    Description: 55-60
    Description: 3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 25
    Publication Date: 2020-03-23
    Description: This paper investigates the ability of adolescents (aged 13–15 years) and young adults (aged 20–26 years) to decode affective bursts culturally situated in a different context (Francophone vs. South Italian). The effects of context show that Italian subjects perform poorly with respect to the Francophone ones revealing a significant native speaker advantage in decoding the selected affective bursts. In addition, adolescents perform better than young adults, particularly in the decoding and intensity ratings of affective bursts of happiness, pain, and pleasure suggesting an effect of age related to language expertise.
    Description: Published
    Description: 1TM. Formazione
    Keywords: Affective bursts ; Age and cultural effects
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 26
    Publication Date: 2019-03-04
    Description: Many marine gastropods show species-specific behavioral responses to different predators, but less is known about the mechanisms influencing differences or similarities in specific responses. Herein, we examined whether two limpet species, Scurria viridula (Lamarck, 1819) and Fissurella latimarginata (Sowerby, 1835), show species- and size-specific similarities or differences in their reaction to predatory seastars and crabs. Both S. viridula and F. latimarginata reacted to their main seastar predators with escape responses. In contrast, both limpets did not flee from common crab predators, but, instead, fastened to the rock. All tested size classes of both limpet species reacted in a similar way, escaping from seastars, but clamping onto the rock in response to crabs. Limpets could reach velocities sufficient to outrun their specific seastar predators, but they were not fast enough to escape crabs. Experiments with limpets of different shell conditions (with and without shell damage) indicated that F. latimarginata with a damaged shell showed “accommodation movements” (slow movements away from stimulus) in response to predatory crabs. In contrast, intact F. latimarginata and all S. viridula (intact and damaged) clamped the shell down to the substratum. The response details suggest that the keyhole limpet F. latimarginata is more sensitive to predators (faster reaction time, longer escape distances, and higher proportion of reacting individuals) than S. viridula, possibly because the morphology of F. latimarginata (the relationship of its shell size and structure to its total body size) makes this species more vulnerable to predation. Our study suggests that chemically mediated effects of seastar and crab predators result in contrasting behavioral responses of both limpet species, independent of their habitat and morphology. Despite the different characteristics of the limpet species and the identity of predators, the limpets react in comparable ways to similar predator types.
    Repository Name: EPIC Alfred Wegener Institut
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  • 27
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    Copernicus
    In:  EPIC3EGU General Assembly 2019, 2019-04-08-2019-04-12Copernicus
    Publication Date: 2021-02-16
    Description: In this study, we present results obtained from modelling the mid-Pliocene warm period using the Community Earth System Models (COSMOS, version: COSMOS-landveg r2413, 2009) with the two different sets of boundary conditions prescribed for the two phases of the Pliocene Model Intercomparison Project (PlioMIP). Boundary conditions, model forcing, and modelling methodology of the two phases of PlioMIP, tagged PlioMIP1 and PlioMIP2,differ considerably in palaeogeography, in particular with regards to the state of ocean gateways, ice-masks, vegetation and topography. Further differences between model setups as suggested for PlioMIP1 and PlioMIP2 consider updates to the concentration of atmospheric carbon dioxide (CO2), that is specified as 405 and 400 parts per million by volume (ppmv) for PlioMIP1 and PlioMIP2, respectively, as well as minor differences in the concentrations of methane (CH4) and nitrous oxide (N2O) due to changes in the protocol of the Paleoclimate Model Intercomparison Project (PMIP) from phase 3 to phase 4. With this manuscript, we bridge the gap between our contributions to PlioMIP1 (Stepanek and Lohmann, 2012) and PlioMIP2 (Stepanek et al., 2019). We highlight some of the effects that differences in the chosen Mid-Pliocene model setup (PlioMIP2 vs. PlioMIP1) have on the climate state as derived with the COSMOS, as this information will be valuable in the framework of the model-model and model-data-comparison within PlioMIP2. We evaluate the model sensitivity to improved mid-Pliocene boundary conditions using PlioMIP’s core mid-Pliocene experiments for PlioMIP1 and PlioMIP2, and present further simulations where we test model sensitivity to variations in palaeogeography, orbit and concentration of CO2. Firstly,we highlight major changes in boundary conditions from PlioMIP1 to PlioMIP2 and also the limitations recorded from the initial effort. The results derived from of our simulations show that COSMOS simulates a mid-Pliocene climate state that is 0.08 K colder in PlioMIP2, if compared to PlioMIP1. On one hand, high-latitude warming,which is supported by proxy evidence of the mid-Pliocene, is underestimated in simulations of both PlioMIP1 andPlioMIP2. On the other hand, spatial variations in surface air temperature (SAT), sea surface temperature (SST) as well as the distribution of sea ice suggest improvement of simulated SAT and SST in PlioMIP2 if employing the updated palaeogeography. The PlioMIP2 Mid-Pliocene simulation produces warmer SSTs in the Arctic and North Atlantic Ocean than derived from the respective PlioMIP1 climate state. The difference in prescribed CO2accountsfor 1.1 K of warming in the Arctic, leading to an ice-free summer in the PlioMIP1 simulation, and a quasi-ice-free summer in PlioMIP2. Furthermore, employing different orbital forcings in simulating the Mid-Pliocene lead to pronounced annual and seasonal variations, which is not accounted for by marine and terrestrial reconstruction of the time-slice.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 28
    Publication Date: 2020-01-21
    Description: The Antarctic temperature changes over the past millennia remain more uncertain than in many other continental regions. This has several origins: (1) the number of high-resolution ice cores is small, in particular on the East Antarctic plateau and in some coastal areas in East Antarctica; (2) the short and spatially sparse instrumental records limit the calibration period for reconstructions and the assessment of the methodologies; (3) the link between isotope records from ice cores and local climate is usually complex and dependent on the spatial scales and timescales investigated. Here, we use climate model results, pseudo-proxy experiments and data assimilation experiments to assess the potential for reconstructing the Antarctic temperature over the last 2 millennia based on a new database of stable oxygen isotopes in ice cores compiled in the frame- work of Antarctica2k (Stenni et al., 2017). The well-known covariance between δ18O and temperature is reproduced in the two isotope-enabled models used (ECHAM5/MPI-OM and ECHAM5-wiso), but is generally weak over the different Antarctic regions, limiting the skill of the reconstructions. Furthermore, the strength of the link displays large variations over the past millennium, further affecting the potential skill of temperature reconstructions based on statistical methods which rely on the assumption that the last decades are a good estimate for longer temperature reconstructions. Using a data assimilation technique allows, in theory, for changes in the δ18O–temperature link through time and space to be taken into account. Pseudoproxy experiments confirm the benefits of using data assimilation methods instead of statistical methods that provide reconstructions with unrealistic variances in some Antarctic subregions. They also confirm that the relatively weak link between both variables leads to a limited potential for reconstructing temperature based on δ18O. However, the reconstruction skill is higher and more uniform among reconstruction methods when the reconstruction target is the Antarctic as a whole rather than smaller Antarctic subregions. This consistency between the methods at the large scale is also observed when reconstructing temperature based on the real δ18O regional composites of Stenni et al. (2017). In this case, temperature reconstructions based on data assimilation confirm the long-term cooling over Antarctica during the last millennium, and the later onset of anthropogenic warming compared with the simulations without data assimilation, which is especially visible in West Antarctica. Data assimilation also allows for models and direct observations to be reconciled by reproducing the east–west contrast in the recent temperature trends. This recent warming pattern is likely mostly driven by internal variability given the large spread of individual Paleoclimate Modelling Intercomparison Project (PMIP)/Coupled Model Intercomparison Project (CMIP) model realizations in simulating it. As in the pseudoproxy framework, the reconstruction methods perform differently at the subregional scale, especially in terms of the variance of the time series produced. While the potential benefits of using a data assimilation method instead of a statistical method have been highlighted in a pseudoproxy framework, the instrumental series are too short to confirm this in a realistic setup.
    Repository Name: EPIC Alfred Wegener Institut
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  • 29
    Publication Date: 2021-08-16
    Description: Ice-wedge polygons are common features of lowland tundra in the continuous permafrost zone and prone to rapid degradation through melting of ground ice. There are many interrelated processes involved in ice-wedge thermokarst and it is a major challenge to quantify their influence on the stability of the permafrost underlying the landscape. In this study we used a numerical modelling approach to investigate the degradation of ice wedges with a focus on the influence of hydrological conditions. Our study area was Samoylov Island in the Lena River delta of northern Siberia, for which we had in situ measurements to evaluate the model. The tailored version of the CryoGrid 3 land surface model was capable of simulating the changing microtopography of polygonal tundra and also regarded lateral fluxes of heat, water, and snow. We demonstrated that the approach is capable of simulating ice-wedge degradation and the associated transition from a low-centred to a high-centred polygonal microtopography. The model simulations showed ice-wedge degradation under recent climatic conditions of the study area, irrespective of hydrological conditions. However, we found that wetter conditions lead to an earlier onset of degradation and cause more rapid ground subsidence. We set our findings in correspondence to observed types of ice-wedge polygons in the study area and hypothesized on remaining discrepancies between modelled and observed ice-wedge thermokarst activity. Our quantitative approach provides a valuable complement to previous, more qualitative and conceptual, descriptions of the possible pathways of ice-wedge polygon evolution. We concluded that our study is a blueprint for investigating thermokarst landforms and marks a step forward in understanding the complex interrelationships between various processes shaping ice-rich permafrost landscapes.
    Repository Name: EPIC Alfred Wegener Institut
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  • 30
    Publication Date: 2022-03-28
    Description: Warming of the Arctic led to an increase in permafrost temperatures by about 0.3 �C during the last decade. Permafrost warming is associated with increasing sediment water content, permeability, and diffusivity and could in the long term alter microbial community composition and abundance even before permafrost thaws. We studied the long-term effect (up to 2500 years) of submarine permafrost warming on microbial communities along an onshore–offshore transect on the Siberian Arctic Shelf displaying a natural temperature gradient of more than 10 �C. We analysed the in situ development of bacterial abundance and community composition through total cell counts (TCCs), quantitative PCR of bacterial gene abundance, and amplicon sequencing and correlated the microbial community data with temperature, pore water chemistry, and sediment physicochemical parameters. On timescales of centuries, permafrost warming coincided with an overall decreasing microbial abundance, whereas millennia after warming microbial abundance was similar to cold onshore permafrost. In addition, the dissolved organic carbon content of all cores was lowest in submarine permafrost after millennial-scale warming. Based on correlation analysis, TCC, unlike bacterial gene abundance, showed a significant rank-based negative correlation with increasing temperature, while bacterial gene copy numbers showed a strong negative correlation with salinity. Bacterial community composition correlated only weakly with temperature but strongly with the pore water stable isotopes �18O and �D, as well as with depth. The bacterial community showed substantial spatial variation and an overall dominance of Actinobacteria, Chloroflexi, Firmicutes, Gemmatimonadetes, and Proteobacteria, which are amongst the microbial taxa that were also found to be active in other frozen permafrost environments. We suggest that, millennia after permafrost warming by over 10 �C, microbial community composition and abundance show some indications for proliferation but mainly reflect the sedimentation history and paleoenvironment and not a direct effect through warming.
    Repository Name: EPIC Alfred Wegener Institut
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  • 31
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2018. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in he balance of salinity variance in a partially stratified estuary: Implications for exchange flow, mixing, and stratification. Journal of Physical Oceanography, 48(12), (2018) 2887-2899., doi: 10.1175/JPO-D-18-0032.1.
    Description: Salinity variance dissipation is related to exchange flow through the salinity variance balance equation, and meanwhile its magnitude is also proportional to the turbulence production and stratification inside the estuary. As river flow increases, estuarine volume-integrated salinity variance dissipation increases owing to more variance input from the open boundaries driven by exchange flow and river flow. This corresponds to the increased efficient conversion of turbulence production to salinity variance dissipation due to the intensified stratification with higher river flow. Through the spring–neap cycle, the temporal variation of salinity variance dissipation is more dependent on stratification than turbulence production, so it reaches its maximum during the transition from neap to spring tides. During most of the transition time from spring to neap tides, the advective input of salinity variance from the open boundaries is larger than dissipation, resulting in the net increase of variance, which is mainly expressed as vertical variance, that is, stratification. The intensified stratification in turn increases salinity variance dissipation. During neap tides, a large amount of enhanced salinity variance dissipation is induced by the internal shear stress near the halocline. During most of the transition time from neap to spring tides, dissipation becomes larger than the advective input, so salinity variance decreases and the stratification is destroyed.
    Description: TW was supported by the National Key R&D Program of China (Grant 2017YFA0604104), National Natural Science Foundation of China (Grant 41706002), Natural Science Foundation of Jiangsu Province (Grant BK20170864), and MEL Visiting Fellowship (MELRS1617). WRG was supported by NSF Grant OCE 1736539. Part of this work is finished during TW’s visit in MEL and WHOI. We would like to acknowledge John Warner for providing the codes of the Hudson estuary model, and Parker MacCready, the editor, and two reviewers for their insightful suggestions on improving the manuscript.
    Description: 2019-06-06
    Keywords: Estuaries ; Dynamics ; Mixing ; Density Currents
    Repository Name: Woods Hole Open Access Server
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  • 32
    Publication Date: 2022-05-25
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Monthly Weather Review 147(1), (2019): 389-406. doi: 10.1175/MWR-D-18-0158.1.
    Description: The quasi-biennial oscillation (QBO) is stratified by stratospheric zonal wind direction and height into four phase pairs [easterly midstratospheric winds (QBOEM), easterly lower-stratospheric winds, westerly midstratospheric winds (QBOWM), and westerly lower-stratospheric winds] using an empirical orthogonal function analysis of daily stratospheric (100–10 hPa) zonal wind data during 1980–2017. Madden–Julian oscillation (MJO) events in which the MJO convective envelope moved eastward across the Maritime Continent (MC) during 1980–2017 are identified using the Real-time Multivariate MJO (RMM) index and the outgoing longwave radiation (OLR) MJO index (OMI). Comparison of RMM amplitudes by the QBO phase pair over the MC (RMM phases 4 and 5) reveals that boreal winter MJO events have the strongest amplitudes during QBOEM and the weakest amplitudes during QBOWM, which is consistent with QBO-driven differences in upper-tropospheric lower-stratospheric (UTLS) static stability. Additionally, boreal winter RMM events over the MC strengthen during QBOEM and weaken during QBOWM. In the OMI, those amplitude changes generally shift eastward to the eastern MC and western Pacific Ocean, which may result from differences in RMM and OMI index methodologies. During boreal summer, as the northeastward-propagating boreal summer intraseasonal oscillation (BSISO) becomes the dominant mode of intraseasonal variability, these relationships are reversed. Zonal differences in UTLS stability anomalies are consistent with amplitude changes of eastward-propagating MJO events across the MC during boreal winter, and meridional stability differences are consistent with amplitude changes of northeastward-propagating BSISO events during boreal summer. Results remain consistent when stratifying by neutral ENSO phase.
    Description: The authors are grateful for the funding provided by the Office of Naval Research Propagation of Intra-Seasonal Tropical Oscillations (ONR PISTON) Award N0001416WX01752 and the USNA Trident Scholar program. The authors also appreciate the helpful comments of the two external reviewers.
    Description: 2019-07-07
    Keywords: Maritime Continent ; Madden-Julian oscillation ; Quasibiennial oscillation
    Repository Name: Woods Hole Open Access Server
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  • 33
    Publication Date: 2019-09-30
    Description: The Global Ocean Data Analysis Project (GLODAP) is a synthesis effort providing regular compilations of surface to bottom ocean biogeochemical data, with an emphasis on seawater inorganic carbon chemistry and related variables determined through chemical analysis of water samples. This update of GLODAPv2, v2.2019, adds data from 116 cruises to the previous version, extending its coverage in time from 2013 to 2017, while also adding some data from prior years. GLODAPv2.2019 includes measurements from more than 1.1 million water samples from the global oceans collected on 840 cruises. The data for the 12 GLODAP core variables (salinity, oxygen, nitrate, silicate, phosphate, dissolved inorganic carbon, total alkalinity, pH, CFC-11, CFC-12, CFC-113, and CCl4) have undergone extensive quality control, especially systematic evaluation of bias. The data are available in two formats: (i) as submitted by the data originator but updated to WOCE exchange format and (ii) as a merged data product with adjustments applied to minimize bias. These adjustments were derived by comparing the data from the 116 new cruises with the data from the 724 quality-controlled cruises of the GLODAPv2 data product. They correct for errors related to measurement, calibration, and data handling practices, taking into account any known or likely time trends or variations. The compiled and adjusted data product is believed to be consistent to better than 0.005 in salinity, 1 % in oxygen, 2 % in nitrate, 2 % in silicate, 2 % in phosphate, 4 µmol kg−1 in dissolved inorganic carbon, 4 µmol kg−1 in total alkalinity, 0.01–0.02 in pH, and 5 % in the halogenated transient tracers. The compilation also includes data for several other variables, such as isotopic tracers. These were not subjected to bias comparison or adjustments. The original data, their documentation and DOI codes are available in the Ocean Carbon Data System of NOAA NCEI (https://www.nodc.noaa.gov/ocads/oceans/GLODAPv2_2019/, last access: 17 September 2019). This site also provides access to the merged data product, which is provided as a single global file and as four regional ones – the Arctic, Atlantic, Indian, and Pacific oceans – under https://doi.org/10.25921/xnme-wr20 (Olsen et al., 2019). The product files also include significant ancillary and approximated data. These were obtained by interpolation of, or calculation from, measured data. This paper documents the GLODAPv2.2019 methods and provides a broad overview of the secondary quality control procedures and results.
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  • 34
    Publication Date: 2019-10-29
    Description: The ozonesonde is a small balloon-borne instrument that is attached to a standard radiosonde to measure profiles of ozone from the surface to 35 km with ∼100-m vertical resolution. Ozonesonde data constitute a mainstay of satellite calibration and are used for climatologies and analysis of trends, especially in the lower stratosphere where satellites are most uncertain. The electrochemical concentration cell (ECC) ozonesonde has been deployed at ∼100 stations worldwide since the 1960s, with changes over time in manufacture and procedures, including details of the cell chemical solution and data processing. As a consequence, there are biases among different stations and discontinuities in profile time series from individual site records. For 22 years the Jülich (Germany) Ozonesonde Intercomparison Experiment (JOSIE) has periodically tested ozonesondes in a simulation chamber designated the World Calibration Centre for Ozonesondes (WCCOS) by WMO. During October–November 2017 a JOSIE campaign evaluated the sondes and procedures used in Southern Hemisphere Additional Ozonesondes (SHADOZ), a 14-station sonde network operating in the tropics and subtropics. A distinctive feature of the 2017 JOSIE was that the tests were conducted by operators from eight SHADOZ stations. Experimental protocols for the SHADOZ sonde configurations, which represent most of those in use today, are described, along with preliminary results. SHADOZ stations that follow WMO-recommended protocols record total ozone within 3% of the JOSIE reference instrument. These results and prior JOSIEs demonstrate that regular testing is essential to maintain best practices in ozonesonde operations and to ensure high-quality data for the satellite and ozone assessment communities.
    Repository Name: EPIC Alfred Wegener Institut
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  • 35
    Publication Date: 2019-10-24
    Description: We present a Lagrangian convective transport scheme developed for global chemistry and transport models, which considers the variable residence time that an air parcel spends in convection. This is particularly important for accurately simulating the tropospheric chemistry of short-lived species, e.g., for determining the time available for heterogeneous chemical processes on the surface of cloud droplets. In current Lagrangian convective transport schemes air parcels are stochastically redistributed within a fixed time step according to estimated probabilities for convective entrainment as well as the altitude of detrainment. We introduce a new scheme that extends this approach by modeling the variable time that an air parcel spends in convection by estimating vertical updraft velocities. Vertical updraft velocities are obtained by combining convective mass fluxes from meteorological analysis data with a parameterization of convective area fraction profiles. We implement two different parameterizations: a parameterization using an observed constant convective area fraction profile and a parameterization that uses randomly drawn profiles to allow for variability. Our scheme is driven by convective mass fluxes and detrainment rates that originate from an external convective parameterization, which can be obtained from meteorological analysis data or from general circulation models. We study the effect of allowing for a variable time that an air parcel spends in convection by performing simulations in which our scheme is implemented into the trajectory module of the ATLAS chemistry and transport model and is driven by the ECMWF ERA-Interim reanalysis data. In particular, we show that the redistribution of air parcels in our scheme conserves the vertical mass distribution and that the scheme is able to reproduce the convective mass fluxes and detrainment rates of ERA-Interim. We further show that the estimated vertical updraft velocities of our scheme are able to reproduce wind profiler measurements performed in Darwin, Australia, for velocities larger than 0.6 m s−1. SO2 is used as an example to show that there is a significant effect on species mixing ratios when modeling the time spent in convective updrafts compared to a redistribution of air parcels in a fixed time step. Furthermore, we perform long-time global trajectory simulations of radon-222 and compare with aircraft measurements of radon activity.
    Repository Name: EPIC Alfred Wegener Institut
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  • 36
    Publication Date: 2019-10-23
    Description: Knowledge on basic biological functions of organisms is essential to understand not only the role they play in the ecosystems but also to manage and protect their populations. The study of biological processes, such as growth, reproduction and physiology, which can be approached in situ or by collecting specimens and rearing them in aquaria, is particularly challenging for deep-sea organisms like cold-water corals. Field experimental work and monitoring of deep-sea populations is still a chimera. Only a handful of research institutes or companies has been able to install in situ marine observatories in the Mediterranean Sea or elsewhere, which facilitate a continuous monitoring of deep-sea ecosystems. Hence, today’s best way to obtain basic biological information on these organisms is (1) working with collected samples and analysing them post-mortem and / or (2) cultivating corals in aquaria in order to monitor biological processes and investigate coral behaviour and physiological responses under different experimental treatments. The first challenging aspect is the collection process, which implies the use of oceanographic research vessels in most occasions since these organisms inhabit areas between ca. 150 m to more than 1000 m depth, and specific sampling gears. The next challenge is the maintenance of the animals on board (in situations where cruises may take weeks) and their transport to home laboratories. Maintenance in the home laboratories is also extremely challenging since special conditions and set-ups are needed to conduct experimental studies to obtain information on the biological processes of these animals. The complexity of the natural environment from which the corals were collected cannot be exactly replicated within the laboratory setting; a fact which has led some researchers to question the validity of work and conclusions drawn from such undertakings. It is evident that aquaria experiments cannot perfectly reflect the real environmental and trophic conditions where these organisms occur, but: (1) in most cases we do not have the possibility to obtain equivalent in situ information and (2) even with limitations, they produce relevant information about the biological limits of the species, which is especially valuable when considering potential future climate change scenarios. This chapter includes many contributions from different authors and is envisioned as both to be a practical “handbook” for conducting cold-water coral aquaria work, whilst at the same time offering an overview on the cold-water coral research conducted in Mediterranean laboratories equipped with aquaria infrastructure. Experiences from Atlantic and Pacific laboratories with extensive experience with cold-water coral work have also contributed to this chapter, as their procedures are valuable to any researcher interested in conducting experimental work with cold-water corals in aquaria. It was impossible to include contributions from all laboratories in the world currently working experimentally with cold-water corals in the laboratory, but at the conclusion of the chapter we attempt, to our best of our knowledge, to supply a list of several laboratories with operational cold-water coral aquaria facilities.
    Repository Name: EPIC Alfred Wegener Institut
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  • 37
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    Springer
    In:  EPIC3Energy Transfers in Atmosphere and Ocean, Energy Transfers in Atmosphere and Ocean, Springer, 1, pp. 87-125, ISBN: 978-3-030-05704-6, ISSN: 2524-4264
    Publication Date: 2020-04-20
    Repository Name: EPIC Alfred Wegener Institut
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  • 38
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 49(7), (2019): 1889-1904, doi:10.1175/JPO-D-19-0053.1.
    Description: A high-resolution numerical model, together with in situ and satellite observations, is used to explore the nature and dynamics of the dominant high-frequency (from one day to one week) variability in Denmark Strait. Mooring measurements in the center of the strait reveal that warm water “flooding events” occur, whereby the North Icelandic Irminger Current (NIIC) propagates offshore and advects subtropical-origin water northward through the deepest part of the sill. Two other types of mesoscale processes in Denmark Strait have been described previously in the literature, known as “boluses” and “pulses,” associated with a raising and lowering of the overflow water interface. Our measurements reveal that flooding events occur in conjunction with especially pronounced pulses. The model indicates that the NIIC hydrographic front is maintained by a balance between frontogenesis by the large-scale flow and frontolysis by baroclinic instability. Specifically, the temperature and salinity tendency equations demonstrate that the eddies act to relax the front, while the mean flow acts to sharpen it. Furthermore, the model reveals that the two dense water processes—boluses and pulses (and hence flooding events)—are dynamically related to each other and tied to the meandering of the hydrographic front in the strait. Our study thus provides a general framework for interpreting the short-time-scale variability of Denmark Strait Overflow Water entering the Irminger Sea.
    Description: MAS was supported by the National Science Foundation (NSF) under Grants OCE-1558742 and OCE-1534618. RSP, PL, and DM were supported by NSF under Grants OCE-1558742 and OCE-1259618. WJvA was supported by the Helmholtz Infrastructure Initiative FRAM. TWNH and MA were supported by NSF under Grants OCE-1633124 and OCE-118123.
    Description: 2020-07-01
    Keywords: Baroclinic flows ; Frontogenesis/frontolysis ; Meridional overturning circulation ; Ocean dynamics ; Topographic effects
    Repository Name: Woods Hole Open Access Server
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  • 39
    Publication Date: 2022-10-27
    Description: Author Posting. © American Meteorological Society, 2018. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Marine Science and Engineering 6(4), (2018): 144. doi:10.3390/jmse6040144.
    Description: Geochronologies derived from sediment cores in coastal locations are often used to infer event bed characteristics such as deposit thicknesses and accumulation rates. Such studies commonly use naturally occurring, short-lived radioisotopes, such as Beryllium-7 (7Be) and Thorium-234 (234Th), to study depositional and post-depositional processes. These radioisotope activities, however, are not generally represented in sediment transport models that characterize coastal flood and storm deposition with grain size patterns and deposit thicknesses. We modified the Community Sediment Transport Modeling System (CSTMS) to account for reactive tracers and used this capability to represent the behavior of these short-lived radioisotopes on the sediment bed. This paper describes the model and presents results from a set of idealized, one-dimensional (vertical) test cases. The model configuration represented fluvial deposition followed by periods of episodic storm resuspension. Sensitivity tests explored the influence on seabed radioisotope profiles by the intensities of bioturbation and wave resuspension and the thickness of fluvial deposits. The intensity of biodiffusion affected the persistence of fluvial event beds as evidenced by 7Be. Both resuspension and biodiffusion increased the modeled seabed inventory of 234Th. A thick fluvial deposit increased the seabed inventory of 7Be and 234Th but mixing over time greatly reduced the difference in inventory of 234Th in fluvial deposits of different thicknesses.
    Description: The Bureau of Ocean Energy Management (BOEM) provided funding for Birchler, Harris, and Kniskern. During his M.S. program Birchler received additional funds from VIMS’ Office of Academic Studies. This work was partially supported by the U.S. Geological Survey, Coastal and Marine Geology Program.
    Keywords: Numerical model ; Sediment transport ; Marine ; Short-lived radioisotopes
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  • 40
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 32(2), (2019): 549-573. doi: 10.1175/JCLI-D-18-0413.1.
    Description: Time series of surface meteorology and air–sea fluxes from the northern Bay of Bengal are analyzed, quantifying annual and seasonal means, variability, and the potential for surface fluxes to contribute significantly to variability in surface temperature and salinity. Strong signals were associated with solar insolation and its modulation by cloud cover, and, in the 5- to 50-day range, with intraseasonal oscillations (ISOs). The northeast (NE) monsoon (DJF) was typically cloud free, with strong latent heat loss and several moderate wind events, and had the only seasonal mean ocean heat loss. The spring intermonsoon (MAM) was cloud free and had light winds and the strongest ocean heating. Strong ISOs and Tropical Cyclone Komen were seen in the southwest (SW) monsoon (JJA), when 65% of the 2.2-m total rain fell, and oceanic mean heating was small. The fall intermonsoon (SON) initially had moderate convective systems and mean ocean heating, with a transition to drier winds and mean ocean heat loss in the last month. Observed surface freshwater flux applied to a layer of the observed thickness produced drops in salinity with timing and magnitude similar to the initial drops in salinity in the summer monsoon, but did not reproduce the salinity variability of the fall intermonsoon. Observed surface heat flux has the potential to cause the temperature trends of the different seasons, but uncertainty in how shortwave radiation is absorbed in the upper ocean limits quantifying the role of surface forcing in the evolution of mixed layer temperature.
    Description: The deployment of the Woods Hole Oceanographic Institution (WHOI) mooring and RW and JTF were supported by the U.S. Office of Naval Research, Grant N00014-13-1-0453. DS acknowledges support from the Ministry of Earth Sciences under India’s National Monsoon Mission. HS acknowledges support from the Office of Naval Research Grants N00014-13-1-0453 and N00014-17-12398. The deployment of the WHOI mooring was done by RV Sagar Nidhi and the recovery by RV Sagar Kanya; the help of the crew and science parties is gratefully acknowledged as is the ongoing support at NIOT in Chennai and by other colleagues in India of this mooring work. The work of the staff of the WHOI Upper Ocean Process Group in the design, building, deployment, and recovery of the mooring and in processing the data is gratefully acknowledged. The software for the wavelet analysis was provided by Torrence and Compo (1998). Feedback on the paper by Dr. Amit Tandon and two anonymous reviewers is gratefully acknowledged. This paper is dedicated to Dr. Frank Bradley.
    Description: 2019-06-28
    Keywords: Atmosphere-ocean interaction ; Monsoons ; Air-sea interaction ; Surface fluxes
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  • 41
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    American Meteorological Society
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography, 49 (2), (2019): 607-630, doi:10.1175/JPO-D-18-0166.1.
    Description: The Lagrangian motion in the eddy field produced from an unstable retrograde jet along the shelf break is studied from idealized numerical experiments with a primitive equation model. The jet is initially in thermal wind balance with a cross-isobath density gradient and is not subjected to any atmospheric forcing. Over the course of the model integration, the jet becomes unstable and produces a quasi-stationary eddy field over a 2-month period. During this period, the cross-slope flow at the shelf break is characterized by along-slope correlation scales of O(10) km and temporal correlation scales of a few days. The relative dispersion of parcels across isobaths is found to increase with time as tb, where 1 〈 b 〈 2. This mixed diffusive–ballistic regime appears to reflect the combined effects of (i) the short length scales of velocity correlation at the shelf break and (ii) the seaward excursion of monopolar and dipolar vortices. Cross-slope dispersion is greater offshore of the front than inshore of the front, as offshore parcels are both subducted onshore below density surfaces and translated offshore with eddies. Nonetheless, the exchange of parcels across the jet remains very limited on the monthly time scale. Particles originating from the bottom experience upward displacements of a few tens of meters and seaward displacements of O(100) km, suggesting that the eddy activity engendered by an unstable along-slope jet provides another mechanism for bottom boundary layer detachment near the shelf edge.
    Description: The author expresses his gratitude to the researchers who contributed to the development and public dissemination of POM [for a list of contributors, see Mellor (2002) and comments in the source code]. Discussions with Kenneth Brink, Hyodae Seo, and Weifeng Zhang have been helpful. Comments provided by Kenneth Brink on a draft are gratefully acknowledged. The criticism from two anonymous reviewers allowed us to better focus the manuscript and to significantly improve its clarity. This work has been supported by Grant OCE-1556400 from the U.S. National Science Foundation.
    Description: 2020-02-18
    Keywords: Dispersion ; Eddies ; Frontogenesis/frontolysis ; Instability ; Lagrangian circulation/transport ; Jets
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  • 42
    Publication Date: 2022-06-09
    Description: In this paper we describe the macroseismic effects produced by the long and destructive seismic sequence that hit Central Italy from 24 August 2016 to January 2017. Starting from the procedure adopted in the complex field survey, we discuss the characteristics of the building stock and its classification in terms of EMS-98 as well as the issues associated with the intensity assessment due to the evolution of damage caused by multiple shocks. As a result, macroseismic intensity for about 300 localities has been determined; however, most of the intensities assessed for the earthquakes following the first strong shock on 24 August 2016, represent the cumulative effect of damage during the sequence. The earthquake parameters computed from the macroseismic datasets are compared with the instrumental determinations in order to highlight critical issues related to the assessment of macroseismic parameters of strong earthquakes during a seismic sequence. The results also provide indications on how location and magnitude computation can be strongly biased when dealing with historical seismic sequences.
    Description: Presidenza del Consiglio dei Ministri - Dipartimento della Protezione Civile (DPC)
    Description: Published
    Description: 2407–2431
    Description: 4T. Sismicità dell'Italia
    Description: 1SR TERREMOTI - Sorveglianza Sismica e Allerta Tsunami
    Description: 2SR TERREMOTI - Gestione delle emergenze sismiche e da maremoto
    Description: 5SR TERREMOTI - Convenzioni derivanti dall'Accordo Quadro decennale INGV-DPC
    Description: JCR Journal
    Keywords: Central Italy ; 2016–2017 Earthquake sequence ; Cumulative damage ; EMS-98 ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 43
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 49(6), (2019): 1577-1592, doi:10.1175/JPO-D-18-0124.1.
    Description: The main source feeding the abyssal circulation of the North Pacific is the deep, northward flow of 5–6 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1) through the Samoan Passage. A recent field campaign has shown that this flow is hydraulically controlled and that it experiences hydraulic jumps accompanied by strong mixing and dissipation concentrated near several deep sills. By our estimates, the diapycnal density flux associated with this mixing is considerably larger than the diapycnal flux across a typical isopycnal surface extending over the abyssal North Pacific. According to historical hydrographic observations, a second source of abyssal water for the North Pacific is 2.3–2.8 Sv of the dense flow that is diverted around the Manihiki Plateau to the east, bypassing the Samoan Passage. This bypass flow is not confined to a channel and is therefore less likely to experience the strong mixing that is associated with hydraulic transitions. The partitioning of flux between the two branches of the deep flow could therefore be relevant to the distribution of Pacific abyssal mixing. To gain insight into the factors that control the partitioning between these two branches, we develop an abyssal and equator-proximal extension of the “island rule.” Novel features include provisions for the presence of hydraulic jumps as well as identification of an appropriate integration circuit for an abyssal layer to the east of the island. Evaluation of the corresponding circulation integral leads to a prediction of 0.4–2.4 Sv of bypass flow. The circulation integral clearly identifies dissipation and frictional drag effects within the Samoan Passage as crucial elements in partitioning the flow.
    Description: This work was supported by the National Science Foundation under Grants OCE-1029268, OCE-1029483, OCE-1657264, OCE-1657870, OCE-1658027, and OCE-1657795. We thank the captain, crew, and engineers at APL/UW for their hard work and skill.
    Description: 2020-06-11
    Keywords: Abyssal circulation ; Bottom currents ; Boundary currents ; Channel flows ; Mixing ; Transport
    Repository Name: Woods Hole Open Access Server
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  • 44
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 49(9), (2019): 2337-2343, doi:10.1175/JPO-D-19-0097.1.
    Description: The weakly unstable, two-layer model of baroclinic instability is studied in a configuration in which the flow is perturbed at the inflow section of a channel by a slow and periodic perturbation. In a parameter regime where the governing equation would be the Lorenz equations for chaos if the development occurs only in time, the solution behavior becomes considerably more complex as a function of time and downstream coordinate. In the absence of the beta effect it has earlier been shown that the chaotic behavior along characteristics renders the solution nearly discontinuous in the slow downstream coordinate of the asymptotic model. The additional presence of the beta effect, although expunging the chaos for large enough values of the beta parameter, also provides an additional mechanism for abrupt spatial change.
    Description: 2020-02-28
    Keywords: Cyclogenesis/cyclolysis ; Eddies ; Microscale processes/variability ; Stability
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  • 45
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of the Atmospheric Sciences 76(10), (2019): 3013-3027, doi:10.1175/JAS-D-19-0095.1.
    Description: Recently Nakamura and Huang proposed a semiempirical, one-dimensional model of atmospheric blocking based on the observed budget of local wave activity in the boreal winter. The model dynamics is akin to that of traffic flow, wherein blocking manifests as traffic jams when the streamwise flux of local wave activity reaches capacity. Stationary waves modulate the jet stream’s capacity to transmit transient waves and thereby localize block formation. Since the model is inexpensive to run numerically, it is suited for computing blocking statistics as a function of climate variables from large-ensemble, parameter sweep experiments. We explore sensitivity of blocking statistics to (i) stationary wave amplitude, (ii) background jet speed, and (iii) transient eddy forcing, using frequency, persistence, and prevalence as metrics. For each combination of parameters we perform 240 runs of 180-day simulations with aperiodic transient eddy forcing, each time randomizing the phase relations in forcing. The model climate shifts rapidly from a block-free state to a block-dominant state as the stationary wave amplitude is increased and/or the jet speed is decreased. When eddy forcing is increased, prevalence increases similarly but frequency decreases as blocks merge and become more persistent. It is argued that the present-day climate lies close to the boundary of the two states and hence its blocking statistics are sensitive to climate perturbations. The result underscores the low confidence in GCM-based assessment of the future trend of blocking under a changing climate, while it also provides a theoretical basis for evaluating model biases and understanding trends in reanalysis data.
    Description: The main results of this paper emerged from a group project during Rossbypalooza, a student-led summer school at the University of Chicago in June 2018, with the theme of “Understanding climate through simple models.” The authors thank the participants of the summer school for their valuable feedback. Constructive criticisms of the two anonymous reviewers greatly improved the quality of the manuscript. The work is supported by NSF Grants AGS1563307 and AGS1810964
    Keywords: Blocking ; Nonlinear dynamics ; Planetary waves ; Potential vorticity ; Wave breaking ; Climate variability
    Repository Name: Woods Hole Open Access Server
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  • 46
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 49(7), (2019): 1973-1994, doi: 10.1175/JPO-D-18-0194.1.
    Description: Using 18 days of field observations, we investigate the diurnal (D1) frequency wave dynamics on the Tasmanian eastern continental shelf. At this latitude, the D1 frequency is subinertial and separable from the highly energetic near-inertial motion. We use a linear coastal-trapped wave (CTW) solution with the observed background current, stratification, and shelf bathymetry to determine the modal structure of the first three resonant CTWs. We associate the observed D1 velocity with a superimposed mode-zero and mode-one CTW, with mode one dominating mode zero. Both the observed and mode-one D1 velocity was intensified near the thermocline, with stronger velocities occurring when the thermocline stratification was stronger and/or the thermocline was deeper (up to the shelfbreak depth). The CTW modal structure and amplitude varied with the background stratification and alongshore current, with no spring–neap relationship evident for the observed 18 days. Within the surface and bottom Ekman layers on the shelf, the observed velocity phase changed in the cross-shelf and/or vertical directions, inconsistent with an alongshore propagating CTW. In the near-surface and near-bottom regions, the linear CTW solution also did not match the observed velocity, particularly within the bottom Ekman layer. Boundary layer processes were likely causing this observed inconsistency with linear CTW theory. As linear CTW solutions have an idealized representation of boundary dynamics, they should be cautiously applied on the shelf.
    Description: An Australian Research Council Discovery Project (DP 140101322), and a UWA Research Collaboration Award funded this work. T. L. Schlosser acknowledges the support of an Australian Government Research Training Program (RTP) Scholarship. We thank the crew, volunteers and scientists who aided in the field data collection aboard the R/V Revelle, which was funded by the National Science Foundation (OCE-1129763). The continental slope moorings, T4 (M32) and T3 (M44), were also funded by the National Science Foundation (OCE-1129763) and were conceived, planned, and executed by Matthew Alford, Jennifer Mackinnon, Jonathan Nash, Harper Simmons, and Gunnar Voet. We also thank Harper Simmons for the combined R/V Revelle multibeam and Geoscience Australia bathymetry used in this study. We thank the two anonymous reviewers whose comments improved this work.
    Description: 2020-01-16
    Keywords: Australia ; Continental shelf/slope ; Boundary currents ; Dynamics ; Waves, oceanic
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  • 47
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Semper, S., Vage, K., Pickart, R. S., Valdimarsson, H., Torres, D. J., & Jonsson, S. The emergence of the North Icelandic Jet and its evolution from northeast Iceland to Denmark Strait. Journal of Physical Oceanography, 49(10), (2019): 2499-2521, doi:10.1175/JPO-D-19-0088.1.
    Description: The North Icelandic Jet (NIJ) is an important source of dense water to the overflow plume passing through Denmark Strait. The properties, structure, and transport of the NIJ are investigated for the first time along its entire pathway following the continental slope north of Iceland, using 13 hydrographic/velocity surveys of high spatial resolution conducted between 2004 and 2018. The comprehensive dataset reveals that the current originates northeast of Iceland and increases in volume transport by roughly 0.4 Sv (1 Sv ≡ 106 m3 s−1) per 100 km until 300 km upstream of Denmark Strait, at which point the highest transport is reached. The bulk of the NIJ transport is confined to a small area in Θ–S space centered near −0.29° ± 0.16°C in Conservative Temperature and 35.075 ± 0.006 g kg−1 in Absolute Salinity. While the hydrographic properties of this transport mode are not significantly modified along the NIJ’s pathway, the transport estimates vary considerably between and within the surveys. Neither a clear seasonal signal nor a consistent link to atmospheric forcing was found, but barotropic and/or baroclinic instability is likely active in the current. The NIJ displays a double-core structure in roughly 50% of the occupations, with the two cores centered at the 600- and 800-m isobaths, respectively. The transport of overflow water 300 km upstream of Denmark Strait exceeds 1.8 ± 0.3 Sv, which is substantially larger than estimates from a year-long mooring array and hydrographic/velocity surveys closer to the strait, where the NIJ merges with the separated East Greenland Current. This implies a more substantial contribution of the NIJ to the Denmark Strait overflow plume than previously envisaged.
    Description: Six different research vessels were involved in the collection of the data used in this study: RRS James Clark Ross, R/V Knorr, R/V Bjarni Sæmundsson, R/V Håkon Mosby, NRV Alliance, and R/V Kristine Bonnevie. We thank the captain and crew of each of these vessels for their hard work as well as the many watch standers who have sailed on the cruises and helped collect the measurements. We also thank Frank Bahr for processing the VMADCP data collected on NRV Alliance and Magnús Danielsen for the processing of the hydrographic data collected on R/V Bjarni Sæmundsson. We acknowledge Leah Trafford McRaven for assistance with Fig. 1 and two anonymous reviewers for their helpful comments, which improved the manuscript. Funding for the project was provided by the Bergen Research Foundation Grant BFS2016REK01 (K. Våge and S. Semper), the Norwegian Research Council under Grant Agreement 231647 (K. Våge), and the U.S. National Science Foundation Grants OCE-1259618 and OCE-1756361 (R. S. Pickart and D. J. Torres), as well as OCE-1558742 (R. S. Pickart). The dataset is available on PANGAEA under https://doi.pangaea.de/10.1594/PANGAEA.903535.
    Keywords: Ocean ; Continental shelf/slope ; Ocean circulation ; Transport ; Intermediate waters ; In situ oceanic observations
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  • 48
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Schwaha, T., Bernhard, J. M., Edgcomb, V. P., & Todaro, M. A. Aethozooides uraniae, a new deep-sea genus and species of solitary bryozoan from the Mediterranean Sea, with a revision of the Aethozoidae. Marine Biodiversity, 49(4), (2019): 1843-1856, doi: 10.1007/s12526-019-00948-w.
    Description: Bryozoa is a phylum of about 6000 extant species that are almost exclusively colonial. Few species of the uncalcified Gymnolaemata, the ctenostomes, however, show solitary forms that essentially consist of single zooids. Recently, several specimens of a solitary ctenostome bryozoan were encountered for the first time in the deep Mediterranean Sea, at the edge of an anoxic brine lake. Differences in size, tentacle number, and in the variability of cystid appendages set these specimens apart from all other known solitary species. Moreover, additional morphological autapomorphic traits suggest the erection of a novel genus to allocate the new species. Consequently, the new taxon Aethozooides gen. nov. is proposed in virtue of the general resemblance of the Mediterranean specimens with those of the genus Aethozoon Hayward, 1978. Aethozooides uraniae gen. et sp. nov. shows significant variability in the number and location of cystid appendages that range from two on the basal side to one or two on the zooid mid-peristomial position and/or, rarely, on the terminal frontal side. The polypide possesses a distinct, long tentacle crown always carrying 10 tentacles. The prominent retractor muscle consists of numerous bundles that, in contrast to other known gymnolaemates, attach not only to the lophophoral base but also to various parts of the gut. Distally, the aperture shows a set of four apertural muscles including four parieto-vaginal bands. Reviewing the state and diversity of solitary ctenostomes, we propose a revision of the family Aethozoidae to include the genera Franzenella d’Hondt, 1983, Aethozoon, Aethozooides, and two species currently affiliated to the genus Franzenella (F. monniotae and F. radicans) for which we erected the new taxon Solella gen. nov. Keywords
    Description: Open access funding provided by University of Vienna. This study was supported by NSF grants OCE-0849578 to VPE and JMB, OCE-1061391 to JMB and VPE, and The Investment in Science Fund at WHOI.
    Keywords: Ctenostomata ; Lophophore ; Cystid appendages ; Arachnidioidea ; Solella
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  • 49
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Mitchell, S. J., Houghton, B. F., Carey, R. J., Manga, M., Fauria, K. E., Jones, M. R., Soule, S. A., Conway, C. E., Wei, Z., & Giachetti, T. Submarine giant pumice: A window into the shallow conduit dynamics of a recent silicic eruption. Bulletin of Volcanology, 81(7), (2019): 42, doi:10.1007/s00445-019-1298-5.
    Description: Meter-scale vesicular blocks, termed “giant pumice,” are characteristic primary products of many subaqueous silicic eruptions. The size of giant pumices allows us to describe meter-scale variations in textures and geochemistry with implications for shearing processes, ascent dynamics, and thermal histories within submarine conduits prior to eruption. The submarine eruption of Havre volcano, Kermadec Arc, in 2012, produced at least 0.1 km3 of rhyolitic giant pumice from a single 900-m-deep vent, with blocks up to 10 m in size transported to at least 6 km from source. We sampled and analyzed 29 giant pumices from the 2012 Havre eruption. Geochemical analyses of whole rock and matrix glass show no evidence for geochemical heterogeneities in parental magma; any textural variations can be attributed to crystallization of phenocrysts and microlites, and degassing. Extensive growth of microlites occurred near conduit walls where magma was then mingled with ascending microlite-poor, low viscosity rhyolite. Meter- to micron-scale textural analyses of giant pumices identify diversity throughout an individual block and between the exteriors of individual blocks. We identify evidence for post-disruption vesicle growth during pumice ascent in the water column above the submarine vent. A 2D cumulative strain model with a flared, shallow conduit may explain observed vesicularity contrasts (elongate tube vesicles vs spherical vesicles). Low vesicle number densities in these pumices from this high-intensity silicic eruption demonstrate the effect of hydrostatic pressure above a deep submarine vent in suppressing rapid late-stage bubble nucleation and inhibiting explosive fragmentation in the shallow conduit.
    Description: This study was funded primarily through an NSF Ocean grant: OCE-1357443 (SJM, BFH and RJC). MM is supported by NSF EAR 1447559. The μXRT analysis was performed at the Lawrence Berkeley National Lab Advanced Light Source beamline 8.3.2 and the large CT scan by SAS at the University of Texas Austin micro-CT facility. Capillary flow porometry and He-pycnometry were assisted by TG and MRJ at the University of Oregon. Microprobe analysis was conducted at the University of Hawai’i at Mānoa. CEC was supported by post-doctoral research fellowship from the Japan Society for the Promotion of Science (JSPS16788). We would like to thank Kenichiro Tani, Takashi Sano, and Eric Hellebrand for their assistance with geochemical data acquisition, JoAnn Sinton and Wagner Petrographic for thin section preparation, Zachary Langdalen for binary processing of BSE images, Warren M. McKenzie for measuring clast densities, and Dula Parkinson for guidance with the μXRT imaging. We further acknowledge the full scientific team, crew and Jason ROV team (Woods Hole Oceanographic Institute) aboard the R/V Roger Revelle (Scripps Institute of Oceanography) during the MESH expedition in 2015, without whom, this study would not have been possible. Finally, we thank Andrew Harris, Katharine Cashman, Lucia Gurioli and an anonymous reviewer for their insightful and helpful reviews of the manuscript.
    Keywords: Giant pumice ; Submarine volcanism ; Banding ; Tube pumice ; Bubble deformation ; Conduit dynamics
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  • 50
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 32(13), (2019): 3883-3898, doi:10.1175/JCLI-D-18-0735.1.
    Description: While it has generally been understood that the production of Labrador Sea Water (LSW) impacts the Atlantic meridional overturning circulation (MOC), this relationship has not been explored extensively or validated against observations. To explore this relationship, a suite of global ocean–sea ice models forced by the same interannually varying atmospheric dataset, varying in resolution from non-eddy-permitting to eddy-permitting (1°–1/4°), is analyzed to investigate the local and downstream relationships between LSW formation and the MOC on interannual to decadal time scales. While all models display a strong relationship between changes in the LSW volume and the MOC in the Labrador Sea, this relationship degrades considerably downstream of the Labrador Sea. In particular, there is no consistent pattern among the models in the North Atlantic subtropical basin over interannual to decadal time scales. Furthermore, the strong response of the MOC in the Labrador Sea to LSW volume changes in that basin may be biased by the overproduction of LSW in many models compared to observations. This analysis shows that changes in LSW volume in the Labrador Sea cannot be clearly and consistently linked to a coherent MOC response across latitudes over interannual to decadal time scales in ocean hindcast simulations of the last half century. Similarly, no coherent relationships are identified between the MOC and the Labrador Sea mixed layer depth or the density of newly formed LSW across latitudes or across models over interannual to decadal time scales.
    Description: FL and MSL are thankful for the financial support from the National Science Foundation (NSF) Physical Oceanography Program (NSF-OCE-12-59102, NSF-OCE-12-59103). The NCAR contribution was supported by the National Oceanic and Atmospheric Administration (NOAA) Climate Program Office (CPO) under Climate Variability and Predictability Program (CVP) Grant NA13OAR4310138 and by the NSF Collaborative Research EaSM2 Grant OCE-1243015. NCAR is sponsored by the NSF. NPH is supported by NERC programs U.K. OSNAP (NE/K010875) and ACSIS (National Capability, NE/N018044/1). Y-OK is supported by NOAA CPO CVP (NA17OAR4310111) and NSF EaSM2 grant (OCE-1242989). AR is supported by NASA-ROSES Modeling, Analysis and Prediction 2016 NNX16AC93G-MAP. RZ is supported by NOAA/OAR. Argo data were collected and made freely available by the International Argo Program and the national programs that contribute to it (http://www.argo.ucsd.edu, http://argo.jcommops.org). The Argo Program is part of the Global Ocean Observing System (http://doi.org/10.17882/42182). Data from the RAPID-MOCHA-WBTS array funded by NERC, NSF and NOAA are freely available from www.rapid.ac.uk/rapidmoc. We thank Stephen Griffies for providing access to the GFDL-MOM025 COREII simulation output and Matthew Harrison and Xiaoqin Yan for their comments on the manuscript. We also thank the anonymous reviewers for their valuable comments.
    Description: 2020-06-11
    Keywords: North Atlantic Ocean ; Deep convection ; Meridional overturning circulation ; Model comparison
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  • 51
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 49(9), (2019): 2237-2254, doi: 10.1175/JPO-D-18-0181.1.
    Description: A cluster of 45 drifters deployed in the Bay of Bengal is tracked for a period of four months. Pair dispersion statistics, from observed drifter trajectories and simulated trajectories based on surface geostrophic velocity, are analyzed as a function of drifter separation and time. Pair dispersion suggests nonlocal dynamics at submesoscales of 1–20 km, likely controlled by the energetic mesoscale eddies present during the observations. Second-order velocity structure functions and their Helmholtz decomposition, however, suggest local dispersion and divergent horizontal flow at scales below 20 km. This inconsistency cannot be explained by inertial oscillations alone, as has been reported in recent studies, and is likely related to other nondispersive processes that impact structure functions but do not enter pair dispersion statistics. At scales comparable to the deformation radius LD, which is approximately 60 km, we find dynamics in agreement with Richardson’s law and observe local dispersion in both pair dispersion statistics and second-order velocity structure functions.
    Description: This research was supported by the Air Sea Interaction Regional Initiative (ASIRI) under ONR Grant N00014-13-1-0451 (SE and AM) and ONR Grant N00014-13-1-0477 (VH and LC). Additionally, AM and SE thank NSF (Grant OCE-I434788) and ONR (Grant N00014-16-1-2470) for support; VH and LC were further supported by ONR Grant N00014-15-1-2286 and NOAA GDP Grant NA10OAR4320156. We thank Joe LaCasce, Dhruv Balwada, and one anonymous reviewer for helpful comments and discussions that significantly improved this manuscript. The authors thank the captain and crew of the R/V Roger Revelle. The SVP-type drifters are part of the Global Drifter Program and supported by ONR Grant N00014-15-1-2286 and NOAA GDP Grant NA10OAR4320156 and are available under http://www.aoml.noaa.gov/phod/dac/. The Ssalto/Duacs altimeter products were produced and distributed by the Copernicus Marine and Environment Monitoring Service (CMEMS, http://www.marine.copernicus.eu).
    Keywords: Dispersion ; Fronts ; Mesoscale processes ; Subgrid-scale processes ; Trajectories ; Turbulence
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  • 52
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Kelly, M. R., Jr., Neubert, M. G., & Lenhart, S. Marine reserves and optimal dynamic harvesting when fishing damages habitat. Theoretical Ecology, 12(2), (2019): 131-144, doi:10.1007/s12080-018-0399-7.
    Description: Marine fisheries are a significant source of protein for many human populations. In some locations, however, destructive fishing practices have negatively impacted the quality of fish habitat and reduced the habitat’s ability to sustain fish stocks. Improving the management of stocks that can be potentially damaged by harvesting requires improved understanding of the spatiotemporal dynamics of the stocks, their habitats, and the behavior of the harvesters. We develop a mathematical model for both a fish stock as well as its habitat quality. Both are modeled using nonlinear, parabolic partial differential equations, and density dependence in the growth rate of the fish stock depends upon habitat quality. The objective is to find the dynamic distribution of harvest effort that maximizes the discounted net present value of the coupled fishery-habitat system. The value derives both from extraction (and sale) of the stock and the provisioning of ecosystem services by the habitat. Optimal harvesting strategies are found numerically. The results suggest that no-take marine reserves can be an important part of the optimal strategy and that their spatiotemporal configuration depends both on the vulnerability of habitat to fishing damage and on the timescale of habitat recovery when fishing ceases.
    Description: This manuscript is based upon the work supported by the National Science Foundation under Grant No. DEB-1558904 (to MGN) and also supported by the National Institute for Mathematical and Biological Synthesis, an Institute supported by the National Science Foundation through NSF Award #DBI-1300426, with additional support from The University of Tennessee, Knoxville.
    Keywords: Fisheries bioeconomics ; Marine protected areas ; Optimal control ; Destructive fishing ; Ecosystem-based management
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  • 53
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of the Atmospheric and Oceanic Technology 36(10), (2019): 1997-2014, doi: 10.1175/JTECH-D-19-0029.1.
    Description: While land-based high-frequency (HF) radars are the only instruments capable of resolving both the temporal and spatial variability of surface currents in the coastal ocean, recent high-resolution views suggest that the coastal ocean is more complex than presently deployed radar systems are able to reveal. This work uses a hybrid system, having elements of both phased arrays and direction finding radars, to improve the azimuthal resolution of HF radars. Data from two radars deployed along the U.S. East Coast and configured as 8-antenna grid arrays were used to evaluate potential direction finding and signal, or emitter, detection methods. Direction finding methods such as maximum likelihood estimation generally performed better than the well-known multiple signal classification (MUSIC) method given identical emitter detection methods. However, accurately estimating the number of emitters present in HF radar observations is a challenge. As MUSIC’s direction-of-arrival (DOA) function permits simple empirical tests that dramatically aid the detection process, MUSIC was found to be the superior method in this study. The 8-antenna arrays were able to provide more accurate estimates of MUSIC’s noise subspace than typical 3-antenna systems, eliminating the need for a series of empirical parameters to control MUSIC’s performance. Code developed for this research has been made available in an online repository.
    Description: This analysis was supported by NSF Grants OCE-1657896 and OCE-1736930 to Kirincich, OCE-1658475 to Emery and Washburn and OCE-1736709 to Flament. Flament is also supported by NOAA’s Integrated Ocean Observing System through Award NA11NOS0120039. The authors thank Lindsey Benjamin, Alma Castillo, Ken Constantine, Benedicte Dousset, Ian Fernandez, Mael Flament, Dave Harris, Garrett Hebert, Ben Hodges, Victoria Futch, Matt Guanci, and Philip Moravcik for assistance in building, deploying, and operating the radars.
    Description: 2020-04-11
    Keywords: Ocean ; Coastal flows ; Algorithms ; Radars/Radar observations ; Remote sensing
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  • 54
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 32(8), (2019): 2185-2205. doi:10.1175/JCLI-D-18-0538.1.
    Description: Much attention has been paid to the climatic impacts of changes in the Kuroshio Extension, instead of the Kuroshio in the East China Sea (ECS). This study, however, reveals the prominent influences of the lateral shift of the Kuroshio at interannual time scale in late spring [April–June (AMJ)] on the sea surface temperature (SST) and precipitation in summer around the ECS, based on high-resolution satellite observations and ERA-Interim. A persistent offshore displacement of the Kuroshio during AMJ can result in cold SST anomalies in the northern ECS and the Japan/East Sea until late summer, which correspondingly causes anomalous cooling of the lower troposphere. Consequently, the anomalous cold SST in the northern ECS acts as a key driver to robustly enhance the precipitation from the Yangtze River delta to Kyushu in early summer (May–August) and over the central ECS in late summer (July–September). In view of the moisture budget analysis, two different physical processes modulated by the lateral shift of the Kuroshio are identified to account for the distinct responses of precipitation in early and late summer, respectively. First, the anomalous cold SST in the northern ECS induced by the Kuroshio offshore shift is likely conducive to the earlier arrival of the mei-yu–baiu front at 30°–32°N and its subsequent slower northward movement, which may prolong the local rainy season, leading to the increased rain belt in early summer. Second, the persistent cold SST anomalies in late summer strengthen the near-surface baroclinicity and the associated strong atmospheric fronts embedded in the extratropical cyclones over the central ECS, which in turn enhances the local rainfall.
    Description: We appreciate three anonymous reviewers for their thoughtful and constructive comments. This work is supported by the National Key Research and Development Program of China (2016YFA0601804), the National Natural Science Foundation of China (NSFC) Projects (91858102, 41490643, 41490640, 41506009, U1606402) and the OUC–WHOI joint research program (21366).
    Description: 2019-10-01
    Keywords: Continental shelf/slope ; Atmosphere-ocean interaction ; Boundary currents ; Precipitation ; Interannual variability
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  • 55
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 49(4), (2019): 1035-1053, doi:10.1175/JPO-D-18-0136.1.
    Description: Ocean stratification and the vertical extent of the mixed layer influence the rate at which the ocean and atmosphere exchange properties. This process has direct impacts for anthropogenic heat and carbon uptake in the Southern Ocean. Submesoscale instabilities that evolve over space (1–10 km) and time (from hours to days) scales directly influence mixed layer variability and are ubiquitous in the Southern Ocean. Mixed layer eddies contribute to mixed layer restratification, while down-front winds, enhanced by strong synoptic storms, can erode stratification by a cross-frontal Ekman buoyancy flux. This study investigates the role of these submesoscale processes on the subseasonal and interannual variability of the mixed layer stratification using four years of high-resolution glider data in the Southern Ocean. An increase of stratification from winter to summer occurs due to a seasonal warming of the mixed layer. However, we observe transient decreases in stratification lasting from days to weeks, which can arrest the seasonal restratification by up to two months after surface heat flux becomes positive. This leads to interannual differences in the timing of seasonal restratification by up to 36 days. Parameterizing the Ekman buoyancy flux in a one-dimensional mixed layer model reduces the magnitude of stratification compared to when the model is run using heat and freshwater fluxes alone. Importantly, the reduced stratification occurs during the spring restratification period, thereby holding important implications for mixed layer dynamics in climate models as well as physical–biological coupling in the Southern Ocean.
    Description: MdP acknowledges numerous research visits to the Department of Marine Science, University of Gothenburg, and a visit to Woods Hole Oceanographic Institution, which greatly enhanced this work. We thank SANAP and the captain and crew of the S.A. Agulhas II for their assistance in the deployment and retrieval of the gliders. We acknowledge the work of SAMERC-STS for housing, managing, and piloting the gliders. SS was supported by NRF-SANAP Grant SNA14071475720 and a Wallenberg Academy Fellowship (WAF 2015.0186). Lastly, SS thanks the numerous technical assistance, advice, and IOP hosting provided by Geoff Shilling and Craig Lee of the Applied Physics Laboratory, University of Washington.
    Description: 2020-04-11
    Keywords: Atmosphere-ocean interaction ; Fronts ; Oceanic mixed layer ; In situ oceanic observations ; Interannual variability ; Seasonal cycle
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  • 56
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 49(6), (2019): 1639-1649, doi: 10.1175/JPO-D-18-0154.1.
    Description: Using a recently developed asymptotic theory of internal solitary wave propagation over a sloping bottom in a rotating ocean, some new qualitative and quantitative features of this process are analyzed for internal waves in a two-layer ocean. The interplay between different singularities—terminal damping due to radiation and disappearing quadratic nonlinearity, and reaching an “internal beach” (e.g., zero lower-layer depth)—is discussed. Examples of the adiabatic evolution of a single solitary wave over a uniformly sloping bottom under realistic conditions are considered in more detail and compared with numerical solutions of the variable-coefficient, rotation-modified Korteweg–de Vries (rKdV) equation.
    Description: LAO is thankful to Yu. Stepanyants for broad discussions of mutual benefit. KRH was supported by Grant N00014-18-1-2542 from the Office of Naval Research.
    Description: 2020-06-13
    Keywords: Internal waves ; Differential equations ; Nonlinear models ; Ocean models
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  • 57
    Publication Date: 2022-05-26
    Description: Author Posting. © The Author(s), 2019. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in , Zakroff, C., Mooney, T.A. & Berumen, M.L. Dose-dependence and small-scale variability in responses to ocean acidification during squid, Doryteuthis pealeii, development. Marine Biology, (2019), 166: 62. doi:10.1007/s00227-019-3510-8.
    Description: Coastal squids lay their eggs on the benthos, leaving them to develop in a dynamic system that is undergoing rapid acidification due to human influence. Prior studies have broadly investigated the impacts of ocean acidification on embryonic squid, but have not addressed the thresholds at which these responses occur or their potential variability. We raised squid, Doryteuthis pealeii (captured in Vineyard Sound, Massachusetts, USA: 41° 23.370N 70° 46.418´W), eggs in three trials across the breeding season (May - September, 2013) in a total of six chronic pCO2 exposures (400, 550, 850, 1300, 1900, and 2200 ppm). Hatchlings were counted and subsampled for mantle length, yolk volume, hatching time, hatching success, and statolith morphology. New methods for analysis of statolith shape, rugosity, and surface degradation were developed and are presented (with code). Responses to acidification (e.g., reduced mantle lengths, delayed hatching, and smaller, more degraded statoliths) were evident at ~ 1300 ppm CO2. However, patterns of physiological response and energy management, based on comparisons of yolk consumption and growth, varied among trials. Interactions between pCO2 and hatching day indicated a potential influence of exposure time on responses, while interactions with culture vessel highlighted the substantive natural variability within a clutch of eggs. While this study is consistent with, and expands upon, previous findings of sensitivity of the early life stages to acidification, it also highlights the plasticity and potential for resilience in this population of squid.
    Description: This material was based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. 1122374 to CZ. This project was funded by National Science Foundation Grant No. 1220034 to TAM.
    Description: 2020-04-19
    Keywords: cephalopod ; embryo ; hypercapnia ; paralarvae ; statolith ; stress
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    Type: Preprint
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  • 58
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society, 100(5), (2019): 897-908, doi:10.1175/BAMS-D-19-0130.1.
    Description: As states, cities, tribes, and private interests cope with climate damages and seek to increase preparedness and resilience, they will need to navigate myriad choices and options available to them. Making these choices in ways that identify pathways for climate action that support their development objectives will require constructive public dialogue, community participation, and flexible and ongoing access to science- and experience-based knowledge. In 2016, a Federal Advisory Committee (FAC) was convened to recommend how to conduct a sustained National Climate Assessment (NCA) to increase the relevance and usability of assessments for informing action. The FAC was disbanded in 2017, but members and additional experts reconvened to complete the report that is presented here. A key recommendation is establishing a new nonfederal “climate assessment consortium” to increase the role of state/local/tribal government and civil society in assessments. The expanded process would 1) focus on applied problems faced by practitioners, 2) organize sustained partnerships for collaborative learning across similar projects and case studies to identify effective tested practices, and 3) assess and improve knowledge-based methods for project implementation. Specific recommendations include evaluating climate models and data using user-defined metrics; improving benefit–cost assessment and supporting decision-making under uncertainty; and accelerating application of tools and methods such as citizen science, artificial intelligence, indicators, and geospatial analysis. The recommendations are the result of broad consultation and present an ambitious agenda for federal agencies, state/local/tribal jurisdictions, universities and the research sector, professional associations, nongovernmental and community-based organizations, and private-sector firms.
    Description: This report would not have been possible without the support and participation of numerous organizations and individuals. We thank New York State Governor Andrew M. Cuomo for announcing in his 2018 State of the State agenda that the IAC would be reconvened. The New York State Energy Research and Development Authority (Contract ID 123416), Columbia University’s Earth Institute, and the American Meteorological Society provided essential financial support and much more, including sage advice and moral support from John O’Leary, Shara Mohtadi, Steve Cohen, Alex Halliday, Peter deMenocal, Keith Seitter, Paul Higgins, and Bill Hooke. We thank the attendees of a workshop, generously funded by the Kresge Foundation in November of 2017, that laid a foundation for the idea to establish a civil-society-based assessment consortium. During the course of preparing the report, IAC members consulted with individuals too numerous to list here—state, local, and tribal officials; researchers; experts in nongovernmental and community-based organizations; and professionals in engineering, architecture, public health, adaptation, and other areas. We are so grateful for their time and expertise. We thank the members and staff of the National Academy of Sciences, Engineering, and Medicine’s Committee to Advise the U.S. Global Change Research Program for providing individual comments on preliminary recommendations during several discussions in open sessions of their meetings. The following individuals provided detailed comments on an earlier version of this report, which greatly sharpened our thinking and recommendations: John Balbus, Tom Dietz, Phil Duffy, Baruch Fischhoff, Brenda Hoppe, Melissa Kenney, Linda Mearns, Claudia Nierenberg, Kathleen Segerson, Soroosh Sorooshian, Chris Weaver, and Brian Zuckerman. Mary Black provided insightful copy editing of several versions of the report. We also thank four anonymous reviewers for their effort and care in critiquing and improving the report. It is the dedication, thoughtful feedback, expertise, care, and commitment of all these people and more that not only made this report possible, but allow us all to continue to support smart and insightful actions in a changing climate. We are grateful as authors and as global citizens. Author contributions: RM, SA, KB, MB, AC, JD, PF, KJ, AJ, KK, JK, ML, JM, RP, TR, LS, JS, JW, and DZ were members of the IAC and shared in researching, discussing, drafting, and approving the report. BA, JF, AG, LJ, SJ, PK, RK, AM, RM, JN, WS, JS, PT, GY, and RZ contributed to specific sections of the report.
    Repository Name: Woods Hole Open Access Server
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  • 59
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 49(6), (2019):1463-1483, doi: 10.1175/JPO-D-18-0213.1.
    Description: A set of float trajectories, deployed at 1500- and 2500-m depths throughout the deep Gulf of Mexico from 2011 to 2015, are analyzed for mesoscale processes under the Loop Current (LC). In the eastern basin, December 2012–June 2014 had 〉40 floats per month, which was of sufficient density to allow capturing detailed flow patterns of deep eddies and topographic Rossby waves (TRWs), while two LC eddies formed and separated. A northward advance of the LC front compresses the lower water column and generates an anticyclone. For an extended LC, baroclinic instability eddies (of both signs) develop under the southward-propagating large-scale meanders of the upper-layer jet, resulting in a transfer of eddy kinetic energy (EKE) to the lower layer. The increase in lower-layer EKE occurs only over a few months during meander activity and LC eddy detachment events, a relatively short interval compared with the LC intrusion cycle. Deep EKE of these eddies is dispersed to the west and northwest through radiating TRWs, of which examples were found to the west of the LC. Because of this radiation of EKE, the lower layer of the eastern basin becomes relatively quiescent, particularly in the northeastern basin, when the LC is retracted and a LC eddy has departed. A mean west-to-east, anticyclone–cyclone dipole flow under a mean LC was directly comparable to similar results from a previous moored LC array and also showed connections to an anticlockwise boundary current in the southeastern basin.
    Description: The authors were supported by the Department of the Interior, Bureau of Ocean Energy Management (BOEM), Contract M08PC20043 to Leidos, Inc., Raleigh, NC. The authors also wish to acknowledge the enthusiastic support of Dr. Alexis Lugo-Fernández, the BOEM Contracting Officer’s Technical Representative, during the study into the Deep Circulation of the Gulf of Mexico, using Lagrangian Methods. Thanks go to the captains and crews of the R/V Pelican and B/O Justo Sierra, J. Malbrough (LUMCON), J. Singer (Leidos), J. Valdes (WHOI), B. Guest (WHOI), and the CANEK group (CICESE).
    Description: 2020-05-29
    Keywords: Bottom currents ; Eddies ; Instability ; Lagrangian circulation/transport ; Mesoscale processes ; Topographic effects
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  • 60
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Atmospheric and Oceanic Technology 36(4), (2019): 733-744, doi:10.1175/JTECH-D-18-0050.1.
    Description: Sea-Bird Scientific SBE 41CP CTDs are used on autonomous floats in the global Argo ocean observing program to measure the temperature and salinity of the upper ocean. While profiling, the sensors are subject to dynamic errors as they profile through vertical gradients. Applying dynamic corrections to the temperature and conductivity data reduces these errors and improves sensor accuracy. A series of laboratory experiments conducted in a stratified tank are used to characterize dynamic errors and determine corrections. The corrections are adapted for Argo floats, and recommendations for future implementation are presented.
    Description: 2020-04-23
    Keywords: Data processing ; In situ oceanic observations ; Instrumentation/sensors ; oceanic ; Profilers, oceanic
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  • 61
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Weather Climate and Society 11(3), (2019):465-487, doi: 10.1175/WCAS-D-18-0134.1.
    Description: As states, cities, tribes, and private interests cope with climate damages and seek to increase preparedness and resilience, they will need to navigate myriad choices and options available to them. Making these choices in ways that identify pathways for climate action that support their development objectives will require constructive public dialogue, community participation, and flexible and ongoing access to science- and experience-based knowledge. In 2016, a Federal Advisory Committee (FAC) was convened to recommend how to conduct a sustained National Climate Assessment (NCA) to increase the relevance and usability of assessments for informing action. The FAC was disbanded in 2017, but members and additional experts reconvened to complete the report that is presented here. A key recommendation is establishing a new nonfederal “climate assessment consortium” to increase the role of state/local/tribal government and civil society in assessments. The expanded process would 1) focus on applied problems faced by practitioners, 2) organize sustained partnerships for collaborative learning across similar projects and case studies to identify effective tested practices, and 3) assess and improve knowledge-based methods for project implementation. Specific recommendations include evaluating climate models and data using user-defined metrics; improving benefit–cost assessment and supporting decision-making under uncertainty; and accelerating application of tools and methods such as citizen science, artificial intelligence, indicators, and geospatial analysis. The recommendations are the result of broad consultation and present an ambitious agenda for federal agencies, state/local/tribal jurisdictions, universities and the research sector, professional associations, nongovernmental and community-based organizations, and private-sector firms.
    Description: This report would not have been possible without the support and participation of numerous organizations and individuals. We thank New York State Governor Andrew M. Cuomo for announcing in his 2018 State of the State agenda that the IAC would be reconvened. The New York State Energy Research and Development Authority (Contract ID 123416), Columbia University’s Earth Institute, and the American Meteorological Society provided essential financial support and much more, including sage advice and moral support from John O’Leary, Shara Mohtadi, Steve Cohen, Alex Halliday, Peter deMenocal, Keith Seitter, Paul Higgins, and Bill Hooke. We thank the attendees of a workshop, generously funded by the Kresge Foundation in November of 2017, that laid a foundation for the idea to establish a civil-society-based assessment consortium. During the course of preparing the report, IAC members consulted with individuals too numerous to list here—state, local, and tribal officials; researchers; experts in nongovernmental and community-based organizations; and professionals in engineering, architecture, public health, adaptation, and other areas. We are so grateful for their time and expertise. We thank the members and staff of the National Academy of Sciences, Engineering, and Medicine’s Committee to Advise the U.S. Global Change Research Program for providing individual comments on preliminary recommendations during several discussions in open sessions of their meetings. The following individuals provided detailed comments on an earlier version of this report, which greatly sharpened our thinking and recommendations: John Balbus, Tom Dietz, Phil Duffy, Baruch Fischhoff, Brenda Hoppe, Melissa Kenney, Linda Mearns, Claudia Nierenberg, Kathleen Segerson, Soroosh Sorooshian, Chris Weaver, and Brian Zuckerman. Mary Black provided insightful copy editing of several versions of the report. We also thank four anonymous reviewers for their effort and care in critiquing and improving the report. It is the dedication, thoughtful feedback, expertise, care, and commitment of all these people and more that not only made this report possible, but allow us all to continue to support smart and insightful actions in a changing climate. We are grateful as authors and as global citizens. Author contributions: RM, SA, KB, MB, AC, JD, PF, KJ, AJ, KK, JK, ML, JM, RP, TR, LS, JS, JW, and DZ were members of the IAC and shared in researching, discussing, drafting, and approving the report. BA, JF, AG, LJ, SJ, PK, RK, AM, RM, JN, WS, JS, PT, GY, and RZ contributed to specific sections of the report.
    Description: 2020-05-21
    Keywords: North America ; Climate prediction ; Planning ; Policy ; Risk assessment ; Societal impacts
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  • 62
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 49(6), (2019):1619-1637, doi:10.1175/JPO-D-18-0175.1.
    Description: Although the hydrodynamics of river meanders are well studied, the influence of curvature on flow in estuaries, with alternating tidal flow and varying water levels and salinity gradients, is less well understood. This paper describes a field study on curvature effects in a narrow salt-marsh creek with sharp bends. The key observations, obtained during times of negligible stratification, are 1) distinct differences between secondary flow during ebb and flood, with helical circulation as in rivers during ebb and a reversed circulation during flood, and 2) maximum (ebb and flood) streamwise velocities near the inside of the bend, unlike typical river bend flow. The streamwise velocity structure is explained by the lack of a distinct point bar and the relatively deep cross section in the estuary, which means that curvature-induced inward momentum redistribution is not overcome by outward redistribution by frictional and topographic effects. Through differential advection of the along-estuary salinity gradient, the laterally sheared streamwise velocity generates lateral salinity differences, with the saltiest water near the inside during flood. The resulting lateral baroclinic pressure gradient force enhances the standard helical circulation during ebb but counteracts it during flood. This first leads to a reversed secondary circulation during flood in the outer part of the cross section, which triggers a positive feedback mechanism by bringing slower-moving water from the outside inward along the surface. This leads to a reversal of the vertical shear in the streamwise flow, and therefore in the centrifugal force, which further enhances the reversed secondary circulation.
    Description: This project was funded by NSF Grant OCE-1634490. During this work W.M. Kranenburg was supported as USGS Postdoctoral Scholar at Woods Hole Oceanographic Institution. A.M.P. Garcia was supported by the Michael J. Kowalski Fellowship in Ocean Science and Engineering (AMPG), and the Diversity Fellowship of the MIT Office of the Dean of Graduate Education (AMPG). The authors thank Jay Sisson for the technical support and Peter Traykovski for providing the bathymetric data. Also, the suggestions for improvement by Dr. K. Blanckaert and an anonymous reviewer are thankfully acknowledged.
    Keywords: Estuaries ; Advection ; Baroclinic flows ; Barotropic flows
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  • 63
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society 100(5), (2019): 909-912, doi: 10.1175/BAMS-D-18-0319.1.
    Description: The open availability and wide accessibility of digital scientific resources, such as articles and datasets, is becoming the norm for twenty-first-century science. Geoscience researchers are now being asked by funding agencies and scientific publishers to archive and cite data to support open access but often struggle to understand, interpret, and fulfill these requirements. To fulfill the promise of new open data initiatives, 1) scientific resources (e.g., data and software) must be collected and documented properly; 2) repository services, including preservation and storage capabilities, must be maintained, supported, and improved over time; and 3) governance institutions must be established. These issues were discussed in the Geoscience Digital Data Resource and Repository Service (GeoDaRRS) workshop,1 held in August 2018, at NCAR. The workshop brought together more than 60 geoscience researchers, technology experts, scientific publishers, funders, and data repository personnel to discuss data management challenges and opportunities within the geosciences. This included exploring whether new services are needed to complement existing data facilities, particularly in the areas of 1) data management planning support resources and 2) repository services for geoscience researchers who have data that do not fit in any existing repository. More details on the workshop agenda and recommendations are available in the final workshop report (Mayernik et al. 2018).
    Description: The National Science Foundation (NSF) provided the funding support for this workshop. We also thank Cecilia Banner and Elizabeth Faircloth of NCAR for administrative and logistical support.
    Description: 2020-06-04
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  • 64
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 49(6), (2019): 1561-1575, doi:10.1175/JPO-D-19-0002.1.
    Description: Within the pycnocline, where diapycnal mixing is suppressed, both the vertical movement (uplift) of isopycnal surfaces and upward motion along sloping isopycnals supply nutrients to the euphotic layer, but the relative importance of each of these mechanisms is unknown. We present a method for decomposing vertical velocity w into two components in a Lagrangian frame: vertical velocity along sloping isopycnal surfaces and the adiabatic vertical velocity of isopycnal surfaces . We show that , where is the isopycnal slope and is the geometric aspect ratio of the flow, and that accounts for 10%–25% of the total vertical velocity w for isopycnal slopes representative of the midlatitude pycnocline. We perform the decomposition of w in a process study model of a midlatitude eddying flow field generated with a range of isopycnal slopes. A spectral decomposition of the velocity components shows that while is the largest contributor to vertical velocity, is of comparable magnitude at horizontal scales less than about 10 km, that is, at submesoscales. Increasing the horizontal grid resolution of models is known to increase vertical velocity; this increase is disproportionately due to better resolution of , as is shown here by comparing 1- and 4-km resolution model runs. Along-isopycnal vertical transport can be an important contributor to the vertical flux of tracers, including oxygen, nutrients, and chlorophyll, although we find weak covariance between vertical velocity and nutrient anomaly in our model.
    Description: MAF was supported by a National Defense Science and Engineering Graduate Fellowship and AM by NSF OCE-I434788. The authors thank Glenn Flierl and Ruth Curry for helpful conversations, and three anonymous reviewers for comments that improved the manuscript.
    Description: 2020-06-11
    Keywords: Baroclinic flows ; Mesoscale processes ; Small scale processes ; Subgrid-scale processes ; Vertical motion
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  • 65
    Publication Date: 2022-05-26
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Atmospheric and Oceanic Technology 36(9), (2019): 1789-1812, doi:10.1175/JTECH-D-18-0223.1.
    Description: Temporal vertical eddy viscosity coefficient (VEVC) in an Ekman layer model is estimated using an adjoint method. Twin experiments are carried out to investigate the influences of several factors on inversion results, and the conclusions of twin experiments are 1) the adjoint method is a capable method to estimate different kinds of temporal distributions of VEVCs; 2) the gradient descent algorithm is better than CONMIN and L-BFGS for the present problem, although the posterior two algorithms perform better on convergence efficiency; 3) inversion results are sensitive to initial guesses; 4) the model is applicable to different wind conditions; 5) the inversion result with thick boundary layer depth (BLD) is slightly better than thin BLD; 6) inversion results are more sensitive to observations in upper layers than those in lower layers; 7) inversion results are still acceptable when data noise exists, indicating the method can sustain noise to a certain degree; 8) a regularization method is proved to be useful to improve the results for present problem; and 9) the present method can tolerate the existence of balance errors due to the imperfection of governing equations. The methodology is further validated in practical experiments where Ekman currents are derived from Bermuda Testbed Mooring data and assimilated. Modeled Ekman currents coincide well with observed ones, especially for upper layers. The results demonstrate that the assumptions of depth dependence and time dependence are equally important for VEVCs. The feasibility of the typical Ekman model, the imperfection of Ekman balance equations, and the deficiencies of the present method are discussed. This method provides a potential way to realize the time variations of VEVCs in ocean models.
    Description: The authors thank the seven reviewers for the constructive suggestions which have greatly improved the manuscript. Financial support is provided by the National Key Research and Development Plan of China (Grants 2017YFA0604100 and 2017YFC1404000), the National Natural Science Foundation of China (Grants 41876086 and 41806012), Scientific Research Fund of the Second Institute of Oceanography, MNR (Grant JG1819), and the Fundamental Research Funds for the Central Universities of China. Jicai thanks the support of China Scholarship Council for the visiting research in WHOI, and he also thanks the host of WHOI. BTM data are provided by Ocean Physics Laboratory, University of California, Santa Barbara (http://opl.ucsb.edu).
    Description: 2020-03-10
    Keywords: Data assimilation ; Parameterization
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  • 66
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    Springer
    In:  EPIC3Advances in Polar Ecology, The Ecosystem of Kongsfjorden, Svalbard, Springer, pp. 23-46, ISBN: 978-3-319-46423-7
    Publication Date: 2023-06-21
    Description: The Arctic region is considered to be most sensitive to climate change, with warming in the Arctic occurring considerably faster than the global average due to several positive feedback mechanisms contributing to the “Arctic amplification”. Also the maritime and mountainous climate of Svalbard has undergone changes during the last decades. Here, the focus is set on the current atmospheric boundary conditions for the marine ecosystem in the Kongsfjorden area, discussed in the frame of long-term climatic observations in the larger regional and hemispheric context. During the last century, a general warming is found with temperature increases and precipitation changes varying in strength. During the last decades, a strong seasonality of the warming is observed in the Kongsfjorden area, with the strongest temperature increase occurring during the winter season. The winter warming is related to observed changes in the net longwave radiation. Moreover, changes in the net shortwave are observed during the summer period, attributed to the decrease in reflected radiation caused by the retreating snow cover. Another related aspect of radiation is the intensity of solar ultra-violet radiation that is closely coupled to the abundance of ozone in the column of air overhead. The long term evolution of ozone losses in the Arctic and their connection to climate change are discussed.
    Repository Name: EPIC Alfred Wegener Institut
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  • 67
    Publication Date: 2023-02-23
    Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 32(5) (2019): 1551-1571. doi:10.1175/JCLI-D-18-0444.1.
    Description: Previous studies have documented a poleward shift in the subsiding branches of Earth’s Hadley circulation since 1979 but have disagreed on the causes of these observed changes and the ability of global climate models to capture them. This synthesis paper reexamines a number of contradictory claims in the past literature and finds that the tropical expansion indicated by modern reanalyses is within the bounds of models’ historical simulations for the period 1979–2005. Earlier conclusions that models were underestimating the observed trends relied on defining the Hadley circulation using the mass streamfunction from older reanalyses. The recent observed tropical expansion has similar magnitudes in the annual mean in the Northern Hemisphere (NH) and Southern Hemisphere (SH), but models suggest that the factors driving the expansion differ between the hemispheres. In the SH, increasing greenhouse gases (GHGs) and stratospheric ozone depletion contributed to tropical expansion over the late twentieth century, and if GHGs continue increasing, the SH tropical edge is projected to shift further poleward over the twenty-first century, even as stratospheric ozone concentrations recover. In the NH, the contribution of GHGs to tropical expansion is much smaller and will remain difficult to detect in a background of large natural variability, even by the end of the twenty-first century. To explain similar recent tropical expansion rates in the two hemispheres, natural variability must be taken into account. Recent coupled atmosphere–ocean variability, including the Pacific decadal oscillation, has contributed to tropical expansion. However, in models forced with observed sea surface temperatures, tropical expansion rates still vary widely because of internal atmospheric variability.
    Description: We thank Ori Adam, Nick Davis, Isaac Held, Tim Merlis, Lorenzo Polvani, and one anonymous reviewer for helpful comments and suggestions. We thank U.S. CLIVAR and the International Space Science Institute (ISSI) for funding working groups that stimulated this project. We thank all members of the working groups for helpful discussions, and the U.S. CLIVAR and ISSI offices and their sponsoring agencies (NASA,NOAA,NSF,DOE, ESA, Swiss Confederation, Swiss Academy of Sciences, and University of Bern) for supporting these groups and activities.We acknowledge WCRP’sWorking Group on CoupledModelling, which is responsible for CMIP, and we thank the climate modeling groups (Table 2) for producing and making available their model output. For CMIP, the U.S. DOE PCMDI provides coordinating support and led development of software infrastructure in partnership with the Global Organization for Earth System Science Portals.
    Description: 2019-08-06
    Keywords: Hadley circulation ; Climate models ; Reanalysis data ; Multidecadal variability ; Pacific decadal oscillation ; Trends
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  • 68
    Publication Date: 2023-07-05
    Description: Holocene permafrost from ice wedge polygons in the vicinity of large seabird breeding colonies in the Thule District, NW Greenland, was drilled to explore the relation between permafrost aggradation and seabird presence. The latter is reliant on the presence of the North Water Polynya (NOW) in the northern Baffin Bay. The onset of peat accumulation associated with the arrival of little auks (Alle alle) in a breeding colony at Annikitisoq, north of Cape York, is radiocarbon-dated to 4400 cal BP. A thick-billed murre (Uria lomvia) colony on Appat (Saunders Island) in the mouth of the Wolstenholme Fjord started 5650 cal BP. Both species provide marine-derived nutrients (MDNs) that fertilize vegetation and promote peat growth. The geochemical signature of organic matter left by the birds is traceable in the frozen Holocene peat. The peat accumulation rates at both sites are highest after the onset, decrease over time, and were about 2-times faster at the little auk site than at the thick-billed murre site. High accumulation rates induce shorter periods of organic matter (OM) decomposition before it enters the perennially frozen state. This is seen in comparably high C=N ratios and less depleted 13C, pointing to a lower degree of OM decomposition at the little auk site, while the opposite pattern can be discerned at the thick-billed murre site. Peat accumulation rates correspond to 15N trends, where decreasing accumulation led to increasing depletion in 15N as seen in the little-auk-related data. In contrast, the more decomposed OM of the thick-billed murre site shows almost stable 15N. Late Holocene wedge ice fed by cold season precipitation was studied at the little auk site and provides the first stable-water isotopic record from Greenland with mean 18O of 8:00:8, mean D of 36:25:7, mean d excess of 7:70:7, and a 18O-D slope of 7.27, which is close to those of the modern Thule meteoric water line. The syngenetic ice wedge polygon development is mirrored in testacean records of the little auk site and delineates polygon low-center, dry-out, and polygon-high-center stages. The syngenetic permafrost formation directly depending on peat growth (controlled by bird activity) falls within the period of neoglacial cooling and the establishment of the NOW, thus indirectly following the Holocene climate trends.
    Repository Name: EPIC Alfred Wegener Institut
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  • 69
    Publication Date: 2023-11-16
    Description: The paper presents the results of 5 case studies on complex site e ects selected within the project for the level 3 seismic microzonation of several municipalities of Central Italy dam- aged by the 2016 seismic sequence. The case studies are characterized by di erent geo- logical and morphological con gurations: Monte San Martino is located along a hill slope, Montedinove and Arquata del Tronto villages are located at ridge top whereas Capitignano and Norcia lie in correspondence of sediment- lled valleys. Peculiarities of the sites are constituted by the presence of weathered/jointed rock mass, fault zone, shear wave veloc- ity inversion, complex surface and buried morphologies. These factors make the de ni- tion of the subsoil model and the evaluation of the local response particularly complex and di cult to ascertain. For each site, after the discussion of the subsoil model, the results of site response numerical analyses are presented in terms of ampli cation factors and acceleration response spectra in selected points. The physical phenomena governing the site response have also been investigated at each site by comparing 1D and 2D numerical analyses. Implications are deduced for seismic microzonation studies in similar geological and morphological conditions.
    Description: Published
    Description: 5741–5777
    Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica
    Description: JCR Journal
    Keywords: Seismic microzonation ; Ampli cation factors ; Response spectra ; Numerical analyses ; site response
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 70
    Publication Date: 2023-11-21
    Description: This paper describes the seismological analyses performed within the framework of the seismic microzonation study for the reconstruction of 138 municipalities damaged by the 2016–2017 sequence in Central Italy. Many waveforms were recorded over approximately 15 years at approximately 180 instrumented sites equipped with permanent or temporary stations in an area that includes all the damaged localities. Site response was assessed using earthquake and noise recordings at the selected stations through different parameters, such as spectral amplification curves, fundamental resonance frequencies, site-specific response spectra, and average amplification factors. The present study was a collaboration of many different institutions under the coordination of the Italian Center for Seismic Microzonation and its applications. The results were homogenized and gathered into site-specific forms, which represent the main deliverable for the benefit of Italian Civil Protection. It is remarkable that the bulk of this study was performed in a very short period (approximately 2 months) to provide quantitative information for detailed microzonation and future reconstruction of the damaged municipalities.
    Description: Published
    Description: 5553–5593
    Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica
    Description: JCR Journal
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  • 71
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    In:  EPIC3Environmental Science and Technology, American Chemical Society (ACS), 53(15), pp. 8747-8756, ISSN: 0013-936X
    Publication Date: 2024-04-12
    Description: Recent studies pointed to a high ice nucleating activity (INA) in the Arctic sea surface microlayer (SML). However, related chemical information is still sparse. In the present study, INA and free glucose concentrations were quantified in Arctic SML and bulk water samples from the marginal ice zone, the ice-free ocean, melt ponds, and open waters within the ice pack. T50 (defining INA) ranged from −17.4 to −26.8 °C. Glucose concentrations varied from 0.6 to 51 μg/L with highest values in the SML from the marginal ice zone and melt ponds (median 16.3 and 13.5 μg/L) and lower values in the SML from the ice pack and the ice-free ocean (median 3.9 and 4.0 μg/L). Enrichment factors between the SML and the bulk ranged from 0.4 to 17. A positive correlation was observed between free glucose concentration and INA in Arctic water samples (T50(°C) = (−25.6 ± 0.6) + (0.15 ± 0.04)·Glucose(μg/L), RP = 0.66, n = 74). Clustering water samples based on phytoplankton pigment composition resulted in robust but different correlations within the four clusters (RP between 0.67 and 0.96), indicating a strong link to phytoplankton-related processes. Since glucose did not show significant INA itself, free glucose may serve as a potential tracer for INA in Arctic water samples.
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  • 72
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    The European physical journal 39 (2004), S. 169-197 
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We present an analysis, based on a phenomenological set of Generalised Navier-Stokes equations, of Heterodyne Detected Transient Gratings on supercooled molecular liquids of anisotropic molecules. This set of equations generalises equations proven in Franosch, Latz and Pick [24] for the same type of liquids. It also takes into account the three different sources generated by the laser pumping process pertinent for these experiments. We give analytical expressions for the response functions that can be measured using the different polarisation of the experimental set-up. Specialising to the case of parallel polarisation (where longitudinal phonons are launched), we show that each response function is a sum of the same seven “elementary response functions” (ERFs) whose time and temperature evolutions are individually analysed. We also show that the response functions corresponding to two of the sources can be directly connected to the Laplace Transform of a light scattering signal. The ERFs generated by the heat-absorption process, which is the third source, are of a different nature. They do not have the same time and temperature behaviours and they can provide, inter alia, unique information on the rotation-translation coupling function characteristic of these liquids.
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  • 73
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    The European physical journal 39 (2004), S. 199-205 
    ISSN: 1434-6036
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    Topics: Physics
    Notes: Abstract. The superconducting proximity effect is measured in sandwiches of thin Pb films and the alkali metals Cs, Rb, K and Na. The T c -dependence provides information about the interface barriers between Pb and the alkalis. Such a barrier is particularly large in Pb/Cs sandwiches. It is not due to impurities or oxydation. In the presence of a sufficiently strong barrier a special form of the Cooper limit can be applied to calculate the transition temperature of the sandwich.
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  • 74
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    The European physical journal 39 (2004), S. 219-227 
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    Topics: Physics
    Notes: Abstract. We study an atom-phonon coupling model introduced recently for spin-conversion phenomenon. The originality of this model, performed on a linear chain of atoms, is that the elastic force constant values of the spring linking two atoms depends on their electronic states. This leads to introduce naturally in the chain long- and short-range interactions, which appear respectively like a Zeeman and an exchange interactions. The exchange-like interaction can be ferro-, antiferro- or equal to zero. The effects of long-range interactions have already been studied. Here we study those of the short-range interaction. Some parts of the chain phase diagram are analysed and the main features of the experimental behaviours of spin conversion compounds are qualitatively reproduced.
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  • 75
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    The European physical journal 39 (2004), S. 229-234 
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    Topics: Physics
    Notes: Abstract. Within a new class of anthracene-like molecules, namely tetrafluoro-acridines, a systematic study of the structural and optical properties of single crystals of a prototypical member, 1,2,3,4-tetrafluoro-7(N,N)dimethyl-amino-acridine, is illustrated. Single crystals were grown by physical vapour transport using an inert gas flow as carrier, starting from a microcrystalline powder of the pure material. The crystal structure, determined by X ray diffraction, points out that the crystals are monoclinic with molecules stacked along the c axis. The results of atomic force microscopy on the ac face of a single crystal, at both low and molecular resolution, are consistent with the X-ray diffraction data. Preliminary results of the optical properties of the single crystal, in the unique configuration accessible due to the peculiar habit of the samples, are discussed.
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  • 76
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    The European physical journal 39 (2004), S. 241-247 
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    Topics: Physics
    Notes: Abstract. In this paper we introduce a modified lattice Boltzmann model (LBM) with the capability of mimicking a fluid system with dynamic heterogeneities. The physical system is modeled as a one-dimensional fluid, interacting with finite-lifetime moving obstacles. Fluid motion is described by a lattice Boltzmann equation and obstacles are randomly distributed semi-permeable barriers which constrain the motion of the fluid particles. After a lifetime delay, obstacles move to new random positions. It is found that the non-linearly coupled dynamics of the fluid and obstacles produces heterogeneous patterns in fluid density and non-exponential relaxation of two-time autocorrelation function.
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  • 77
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    The European physical journal 41 (2004), S. 289-294 
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    Topics: Physics
    Notes: Abstract. We propose a description of the electronic properties of Ce alloys as an inhomogeneous mixture of two components: one containing magnetic Ce ions with an RKKY interaction J H between them, and the other described as a collection of Kondo impurities with exchange interaction J K . Both J H and J K are assumed to depend on a composition parameter X, with a Gaussian distribution around a value X 0 (near to the expectation value of X), related to the experimental composition parameter x of the alloy. When the concentration of the Kondo impurities is large, the specific heat C displays non-Fermi liquid behavior over a wide temperature range. The main qualitative features of C/T as a function of temperature T observed in several Ce alloys are reproduced using simple J H (X) and J K (X) dependences.
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  • 78
    ISSN: 1434-6036
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    Topics: Physics
    Notes: Abstract. The electronic structure of the strongly Coulomb correlated cuprate CuGeO3 has been calculated by the local-density-approximation method (LDA + U). The parameter U was varied from 0 to 8 eV. The results of the band-structure calculations are compared with experimental data obtained by means of X-ray photoelectron and resonant X-ray emission spectroscopy methods (Cu L $\alpha$ and O K $\alpha$ X-ray emission spectra). It is established that a LDA + U calculation with U = 4 eV reproduces well the X-ray photoelectron and X-ray resonant emission spectral data.
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  • 79
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    The European physical journal 41 (2004), S. 365-375 
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    Topics: Physics
    Notes: Abstract. The ground-state energy E 0 of a spin glass is an example of an extreme statistic. We consider the large deviations of this energy for a variety of models when the number of spins N goes to infinity. In most cases, the behavior can be understood qualitatively, in particular with the help of semi-analytical results for hierarchical lattices. Particular attention is paid to the Sherrington-Kirkpatrick model; after comparing to the Tracy-Widom distribution which follows from the spherical approximation, we find that the large deviations give rise to non-trivial scaling laws with N.
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  • 80
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    The European physical journal 41 (2004), S. 377-382 
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    Topics: Physics
    Notes: Abstract. The formulation of the phase-field problem due to Wheeler et al. [Physica D 66, 243 (1993)] has been adopted and extended as a tool for solidification research by many groups around the World. However, an intrinsic problem of this model is that it couples two physically distinct anisotropies, those associated with the surface energy of the solid-liquid interface and attachment kinetics, into a single anisotropy parameter. In this paper we present a simple extension to the Wheeler model in which we show that introducing a complex form of the anisotropy function allows these two physical parameters to be decoupled.
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  • 81
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    The European physical journal 41 (2004), S. 395-412 
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    Topics: Physics
    Notes: Abstract. We introduce new fast canonical local algorithms for discrete and continuous spin systems. We show that for a broad selection of spin systems they compare favorably to the known ones except for the Ising $\pm$ 1 spins. The new procedures use discretization scheme and the necessary information have to be stored in computer memory before the simulation. The models for testing discrete spins are the Ising $\pm$ 1, the general Ising S or Blume-Capel model, the Potts and the clock models. The continuous spins we examine are the O(N) models, including the continuous Ising model (N = 1), the $\phi^4$ Ising model (N = 1), the XY model (N = 2), the Heisenberg model (N = 3), the $\phi^4$ Heisenberg model (N = 3), the O(4) model with applications to the SU(2) lattice gauge theory, and the general O(N) vector spins with $N\ge5$ .
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  • 82
    ISSN: 1434-6036
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    Topics: Physics
    Notes: Abstract. The Tool-Narayanaswamy-Moynihan (TNM) phenomenological model is widely accepted in order to describe the structural relaxation of glasses. However several quantitative discrepancies can be found in the literature that cannot be entirely ascribed to the experimental errors. In this work we compare the predictive power of two recently proposed configurational entropy approaches extending the TNM formalism. Both of them change the treatment of non linearity by adding a free parameter. We use Differential Scanning Calorimetry (DSC) experiments in order to test the models in two different polymers. One of them is a commercial PMMA sample, the other is a side chain liquid crystal azo-benzene polymer properly synthesized for optical nanorecording purposes. Different results were found for the two systems. In the PMMA sample only one of the new models was able to improve the agreement between DSC experiments and theory with respect to the TNM model, whereas in the second polymer both the approaches were able to describe the experiments better than TNM model.
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  • 83
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    The European physical journal 39 (2004), S. 351-356 
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    Topics: Physics
    Notes: Abstract. We explore the effects of spike-timing-dependent plasticity (STDP) on weak signal transmission in a noisy neural network. We first consider the network where an ensemble of independent neurons, which are subjected to a common weak signal, are connected in parallel to a single postsynaptic neuron via excitatory synapses. STDP can make the signal transmission more efficient, and this effect is more prominent when the presynaptic activities exhibit some correlations. We further consider a two-layer network where there are only couplings between two layers and find that postsynaptic neurons can fire synchronously under suitable conditions. Both the reliability and timing precision of neuronal firing in the output layer are remarkably improved with STDP. These results indicate that STDP can play crucial roles in information processing in nervous systems.
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    The European physical journal 39 (2004), S. 357-363 
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    Topics: Physics
    Notes: Abstract. We consider a simple model for the unfolding of RNA tertiary structure under dynamic loading. The opening of such a structure is regarded as a two step process, each corresponding to the overcoming of a single energy barrier. The resulting two-barrier energy landscape accounts for the dependence of the unfolding kinetics on the pulling rate. Furthermore at intermediate force, the two barriers cannot be distinguished by the analysis of the opening kinetic, which turns out to be dominated by a single macro-barrier, whose properties depend non-trivially on the two single barriers. Our results suggest that in pulling experiments on RNA molecule containing tertiary structures, the details of the single kinetic barriers can only be obtained using a low pulling rate value, or in the high force regime.
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    The European physical journal 39 (2004), S. 365-375 
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    Notes: Abstract. Many crystalline networks can be viewed as decorations of triply periodic minimal surfaces. Such surfaces are covered by the hyperbolic plane in the same way that the Euclidean plane covers a cylinder. Thus, a symmetric hyperbolic network can be wrapped onto an appropriate minimal surface to obtain a 3d periodic net. This requires symmetries of the hyperbolic net to match the symmetries of the minimal surface. We describe a systematic algorithm to find all the hyperbolic symmetries that are commensurate with a given minimal surface, and the generation of simple 3d nets from these symmetry groups.
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  • 86
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    The European physical journal 39 (2004), S. 447-451 
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    Notes: Abstract. We study the problem of a magnetic polaron in an one-dimensional antiferromagnetic semiconductor (ferron). We obtain an analytical solution for the distortion produced in the antiferromagnetic structure due to the presence of a charge carrier bound to an impurity. The region in which the charge carrier is trapped is of the order of the lattice constant (small ferron) but the distortion of the magnetic structure extends over a much larger distance. It is shown that the presence of this distortion makes the ferron more stable, and introduces a new length scale in the problem.
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  • 87
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    Notes: Abstract. Nanoparticles of zinc substituted Mg-ferrite with compositions Mg(1-x)Zn x Fe2O4 (x = 0.15, 0.30 and 0.50) having particle sizes in the range 6.4 nm to 21.4 nm prepared by the co-precipitation method were characterized by 57Fe Mössbauer spectroscopy, X-ray diffratometry and AC magnetic susceptibility measurements. Mössbauer measurements at room temperature and down to 20 K clearly indicate presence of superparamagnetic particles in all the samples. AC magnetic susceptibility data show lowering of blocking temperature with decrease of particle size. Superparamagnetic relaxation was observed for larger particle size in samples with higher Zn content, which is attributed to the weakening of A-B exchange interaction in ferrite lattice due to replacement of Fe3 + in tetrahedral site by Zn2 + ions.
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  • 88
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    The European physical journal 37 (2004), S. 465-471 
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    Notes: Abstract. The recently developed energy-scale-dependent Composite Operator Method is applied to the single-impurity Anderson model. A fully self-consistent solution is given and analyzed. At very low temperatures, the density of states presents, on the top of the high-energy background, a Kondo-like peak whose parameter dependence is discussed in detail. The proposed method reproduces the exact results known in the literature with very low numerical effort and it is applicable for arbitrary values of the external parameters.
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  • 89
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    The European physical journal 37 (2004), S. 489-498 
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    Topics: Physics
    Notes: Abstract. The problem of electrostatic potential distribution in superconductors is studied based on the microscopic theory of superconductors. Local chemical potential of the superconductor is introduced, and an approximation is made to BG theory, which is similar to the Thomas-Fermi (TF) method used in quantum mechanics. The electrostatic potential and charge distribution around an isolated vortex in type-II superconductors is discussed within the approximation. A correction to GL theory considering the electrostatic potential distribution is suggested.
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  • 90
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    The European physical journal 42 (2004), S. 113-117 
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    Notes: Abstract. In the present communication we have tried to study the substrate current behavior in the sub-micron devices after solving the second order differential equation using appropriate boundary conditions. Simple and accurate models for maximum lateral field, drain saturation voltage and for ionization length have been developed. The simulation result of ionization length shows a good match with the known result. Analysis also shows that dominant contributor to the error in the ionization length is not only because of the excess saturated voltage but also due to the channel length and the gate to source voltage. For sub-micron devices the saturation region shifts towards the source for higher drain voltage and larger gate oxide thickness.
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    The European physical journal 42 (2004), S. 103-112 
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    Topics: Physics
    Notes: Abstract. We study the motion of envelope solitons on anharmonic atomic chains in the presence of dissipation and thermal fluctuations. We consider the continuum limit of the discrete system and apply an adiabatic perturbation theory which yields a system of stochastic integro-differential equations for the collective variables of the ansatz for the perturbed envelope soliton. We derive the Fokker-Planck equation of this system and search for a statistically equivalent system of Langevin equations, which shares the same Fokker-Planck equation. We undertake an analytical analysis of the Langevin system and derive an expression for the variance of the soliton position Var[x s ] which predicts a stronger than linear time dependence of Var[x s ] (superdiffusion). We compare these results with simulations for the discrete system and find they agree well. We refer to recent studies where the diffusion of pulse solitons were found to exhibit a superdiffusive behaviour on longer time scales.
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    The European physical journal 42 (2004), S. 123-129 
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    Notes: Abstract. Recent theoretical and empirical studies have focused on the topology of large networks of communication/interactions in biological, social and technological systems. Most of them have been studied in the scope of the small-world and scale-free networks’ theory. Here we analyze the characteristics of ant networks of galleries produced in a 2-D experimental setup. These networks are neither small-worlds nor scale-free networks and belong to a particular class of network, i.e. embedded planar graphs emerging from a distributed growth mechanism. We compare the networks of galleries with both minimal spanning trees and greedy triangulations. We show that the networks of galleries have a path system efficiency and robustness to disconnections closer to the one observed in triangulated networks though their cost is closer to the one of a tree. These networks may have been prevented to evolve toward the classes of small-world and scale-free networks because of the strong spatial constraints under which they grow, but they may share with many real networks a similar trend to result from a balance of constraints leading them to achieve both path system efficiency and robustness at low cost.
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    The European physical journal 39 (2004), S. 469-473 
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    Topics: Physics
    Notes: Abstract. We derive the restricted optical-conductivity sum rule for a model with circulating orbital currents. It is shown that an unusual coupling of the vector potential to the interaction term of the model Hamiltonian results in a non-standard form of the sum rule. As a consequence, the temperature dependence of the restricted spectral weight could be compatible with existing experimental data for high-T c cuprates above the critical temperature T c . We extend our results to the superconducting state, and comment on the differences and analogies between these two symmetry-breaking phenomena.
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  • 94
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    Notes: Abstract. Production parameters are important for the production of desirable type of magnetic materials. The feasibility of low coercivity amorphous films production using a novel rotating cryostat (RC) technique for sensor application was investigated. Fe81Co13.5Si3.5C2 and Fe67Co18Si1B14 amorphous films was vaporised using a resistively heated furnace on to a liquid nitrogen cooled polyimide Kapton $^{\rm TM}$ substrate rotated at the speed of 1300 rpm. The Orthogonal design process was applied in order to systematically optimise the deposition process and parameters over the output functions for the production of low coercivity films. The results indicate that the process can be easily optimised at these level settings with the goal of having the low coercivity amorhous films. By comparing the output function differences with standard deviation for coercivity, the effects of all input parameters (furnace shape, furnace power, mass of material and the gap between substrate and source) on coercivity values of films were analysed. Furthermore, the amorphous nature of these films was confirmed by X-ray measurement.
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    The European physical journal 39 (2004), S. 475-481 
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    Topics: Physics
    Notes: Abstract. On the basis of our former work and by means of the decomposition-decimation method, we study the splitting rules for the second hierarchy of the electronic energy spectra for two-dimensional Fibonacci-class quasicrystals with one kind of atom and two bond lengths. It is found that every line of the sub-spectra for n x n and (n + 1) x (n + 1) clusters of FC(n) $(n \geq 2)$ splits according to the type Y‘(n-1)-2-1 and type Y n-2-1 respectively. The one for n x (n + 1) clusters of FC(n) consists of three sub-subbands when $n \le 2$ , and five sub-subbranches when $n \ge 3$ . The general formulae of the number of energy levels for the spectra of the second hierarchy are obtained. The analytical results are confirmed by numerical simulations.
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    The European physical journal 39 (2004), S. 499-512 
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    Notes: Abstract. We present the statistical-mechanical theory of semiflexible polymers based on the connection between the Kratky-Porod model and the quantum rigid rotator in an external homogeneous field, and treatment of the latter using the quantum mechanical propagator method. The expressions and relations existing for flexible polymers can be generalized to semiflexible ones, if one replaces the Fourier-Laplace transform of the end-to-end polymer distance, 1/(k 2/3 + p), through the matrix $\tilde{P}(k,p) = (I + ikDM)^{-1}D$ , where D and M are related to the spectrum of the quantum rigid rotator, and considers an appropriate matrix element of the expression under consideration. The present work provides also the framework to study polymers in external fields, and problems including the tangents of semiflexible polymers. We study the structure factor of the polymer, the transversal fluctuations of a free end of the polymer with fixed tangent of another end, and the localization of a semiflexible polymer onto an interface. We obtain the partition function of a semiflexible polymer in half space with Dirichlet boundary condition in terms of the end-to-end distribution function of the free semiflexible polymer, study the behaviour of a semiflexible polymer in the vicinity of a surface, and adsorption onto a surface.
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    The European physical journal 39 (2004), S. 491-498 
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    Topics: Physics
    Notes: Abstract. Silver nanoparticles embedded in ZnO matrix were deposited onto fused silica substrates using high pressure (~40 Pa) d.c. sputtering techniques. The particle size in the films was tailored by varying the system pressure and substrate temperature, while the metal volume fraction was controlled by adjusting the relative time of sputtering of the targets. Blue-shift of the surface plasmon resonance peak was observed with the reduction in size and volume fraction of metal particles. A surface plasmon peak in the absorption spectra was found to be absent in the films with particle size and metal concentration below a critical value. A sharp absorption edge in the absorbance spectra within the UV-VIS range indicated semiconducting behavior of the ultrafine silver particles. Films deposited at lower substrate temperature showed a narrow distribution of nanoparticles, nearly spherical in shape. Increase in substrate temperature resulted in a non-uniform size and shape in the films due to the agglomeration of the nanoparticles. These size and shape distributions have a profound effect on the optical absorbance spectra and result in a broad and asymmetric surface plasmon band. A shape distribution introduced in the Maxwell-Garnett or Bruggeman effective medium theory was found to give a reasonable description of the experimentally observed optical absorption spectra.
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  • 98
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    Notes: Abstract. We report an experimental study indicating ultrafast creation and annihilation of space-charge domains in a semiconductor superlattice under the action of a THz field. Our experiment was performed for an InGaAs/InAlAs superlattice with the conduction electrons undergoing miniband transport. We applied to a superlattice a dc bias that was slightly smaller than a critical bias necessary for the formation of space-charge domains caused by a static negative differential conductivity. Additionally subjecting the superlattice to a strong THz field, resulted in a dc transport governed by the formation of domains if the frequency of the field was smaller than an upper frequency limit (~3 THz). From this frequency limit for the creation and annihilation of domains we determined the characteristic time of the domain buildup. Our analysis shows that the buildup time of domains in a wide miniband and heavily doped superlattice is limited by the relaxation time due to scattering of the miniband electrons at polar optic phonons. Our results are of importance for both an understanding of ultrafast dynamics of pattern formation in nanostructures and the development of THz electronic devices.
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    The European physical journal 39 (2004), S. 513-519 
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    Topics: Physics
    Notes: Abstract. Directed spiral percolation (DSP), percolation under both directional and rotational constraints, is studied on the triangular lattice in two dimensions (2D). The results are compared with that of the 2D square lattice. Clusters generated in this model are generally rarefied and have chiral dangling ends on both the square and triangular lattices. It is found that the clusters are more compact and less anisotropic on the triangular lattice than on the square lattice. The elongation of the clusters is in a different direction than the imposed directional constraint on both the lattices. The values of some of the critical exponents and fractal dimension are found considerably different on the two lattices. The DSP model then exhibits a breakdown of universality in 2D between the square and triangular lattices. The values of the critical exponents obtained for the triangular lattice are not only different from that of the square lattice but also different form other percolation models.
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    The European physical journal 39 (2004), S. 521-525 
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    Topics: Physics
    Notes: Abstract. A square lattice is introduced into the Penna model for biological aging in order to study the evolution of diploid sexual populations under certain conditions when one single locus in the individual’s genome is considered as identifier of species. The simulation results show, after several generations, the flourishing and coexistence of two separate species in the same environment, i.e., one original species splits up into two on the same territory (sympatric speciation). As well, the mortalities obtained are in a good agreement with the Gompertz law of exponential increase of mortality with age.
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