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  • Articles  (10)
  • Copernicus  (5)
  • Seismological Society of America (SSA)  (3)
  • Oxford University Press  (2)
  • Geosciences  (10)
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  • Articles  (10)
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  • 1
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    A knowledge-based model for evaluating the impact of gear-based management measures under Europe's new Common Fisheries Policy (2015)
    Oxford University Press
    Details
    Publication Date: 2015-05-30
    Description: A model combining qualitative and historical quantitative data in an innovative rule-based fuzzy cognitive map framework is used to assess and compare the long-term bioeconomic impact of adopting gear modifications aimed at reducing bycatch in the Portuguese crustacean trawl fishery. The impact of codend-related changes (mesh size and shape) and the introduction of a sorting device (sorting grid system) on the main target crustacean species (deepwater rose shrimp Parapenaeus longirostris and Norway lobster Nephrops norvegicus ) and the main fish bycatch species (blue whiting Micromesistius poutassou , horse mackerel Trachurus trachurus , and European hake Merluccius merluccius ) were evaluated. Horse mackerel was the only fish species for which changing codends negatively affected landings per unit of effort by large percentages. The use of a sorting grid system, only evaluated for blue whiting and Norway lobster, led to a strong decrease in landings per unit of effort, especially for the former species. The impact of gear alterations was negligible on fish spawning-stock biomass, but was significant for crustaceans, particularly rose shrimp. A straightforward evaluation of the economic impact (fishers' revenues) of the three bycatch reduction options showed these to be negligible or small.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press
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  • 2
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    Harvesting juveniles of blackspot sea bream (Pagellus bogaraveo) in the Azores (Northeast Atlantic): biological implications, management, and life cycle considerations (2014)
    Oxford University Press
    Details
    Publication Date: 2014-11-18
    Description: Blackspot sea bream ( Pagellus bogaraveo ) is the most important economical resource of Azorean fisheries. Juveniles (age 0 and 1) were detected along island coastlines in nursery grounds that sheltered individuals of up to 13 cm (fork length). Juveniles occurred in coastal areas in all seasons, but higher catch per unit efforts occurred during summer. Larger individuals tended to be caught on the shelves and slopes of the islands and seamounts by the demersal, mixed hook, and line fisheries. Juveniles were exclusively found at inshore areas, while spawners were distributed over offshore areas (islands shelf/slope and seamounts), suggesting an inter-connected cycle of recruitment in coastal areas and ontogenetic migration of juveniles from inshore to offshore areas, while eggs and larvae drift in the opposite direction. Juveniles were found to be targeted by three types of fisheries, amounting to cumulative annual catches of ~36 t. Shore angling was the most important fishing method, followed by bait fishing for tuna and the coastal pelagic live-bait fishery. Fishery managers have enforced several measures to protect juveniles, although our results indicate that effective interdiction of juvenile catch would provide a long-term increase of 15 and 8% in spawning-stock biomass and catch, respectively, as well as ~13% increase in the value of landings. Although this measure could improve the protection of a species in an advanced state of overexploitation, our results showed that a decrease in fishing effort would be necessary to achieve sustainability of the stock.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press
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  • 3
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    Inversion for Focal Mechanisms Using Waveform Envelopes and Inaccurate Velocity Models: Examples from Brazil (2018)
    Seismological Society of America (SSA)
    Details
    Publication Date: 2018
    Description: 〈span〉〈div〉Abstract〈/div〉One of the major challenges for the moment tensor determination is associated with the relatively low‐magnitude events (Mw∼4) recorded by few regional stations at relatively large distances (300–600 km) and analyzed with standard velocity models of the region. Difficulties arise from the fact that synthetics in standard models (e.g., those routinely used in the location) cannot properly match real waveforms and favor the appearance of unmodeled time shifts and amplitude discrepancies (e.g., if VMs are constructed to minimize location residuals, they are not sensitive to uppermost shallow layers, which are insufficiently sampled by rays if shallow sources are missing). The situation is even worse when real waveforms can be matched but the retrieved focal mechanism is incorrect. This article investigates an alternative methodology that is more robust with respect to inappropriate velocity models: the inversion of waveform envelopes. The method is built on an empirical basis. It studies the effects of velocity models on synthetic waveforms and finds that the information about focal mechanism is encoded in the variation of the envelope shapes and amplitudes among the seismogram components. Besides synthetic tests, the method has been tested on real data comprising two earthquakes in Brazil: the 2010 Mw 4.3 Mara Rosa (MR) and the 2017 Mw 4.3 Maranhão earthquakes. When compared with solutions from previous studies, based on many polarities and 〈span〉ad hoc〈/span〉 path‐specific velocity models, we obtained in both cases the same mechanism with a single 1D model and a single‐station polarity constraint. The envelope inversion is a promising technique that might be useful in similar sparse networks, such as the one in Brazil, where standard waveform inversion, in general, is not fully efficient.〈/span〉
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
    Published by Seismological Society of America (SSA)
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  • 4
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    Inversion for Focal Mechanisms Using Waveform Envelopes and Inaccurate Velocity Models: Examples from Brazil (2018)
    Seismological Society of America (SSA)
    Details
    Publication Date: 2018
    Description: 〈span〉〈div〉Abstract〈/div〉One of the major challenges for the moment tensor determination is associated with the relatively low‐magnitude events (Mw∼4) recorded by few regional stations at relatively large distances (300–600 km) and analyzed with standard velocity models of the region. Difficulties arise from the fact that synthetics in standard models (e.g., those routinely used in the location) cannot properly match real waveforms and favor the appearance of unmodeled time shifts and amplitude discrepancies (e.g., if VMs are constructed to minimize location residuals, they are not sensitive to uppermost shallow layers, which are insufficiently sampled by rays if shallow sources are missing). The situation is even worse when real waveforms can be matched but the retrieved focal mechanism is incorrect. This article investigates an alternative methodology that is more robust with respect to inappropriate velocity models: the inversion of waveform envelopes. The method is built on an empirical basis. It studies the effects of velocity models on synthetic waveforms and finds that the information about focal mechanism is encoded in the variation of the envelope shapes and amplitudes among the seismogram components. Besides synthetic tests, the method has been tested on real data comprising two earthquakes in Brazil: the 2010 Mw 4.3 Mara Rosa (MR) and the 2017 Mw 4.3 Maranhão earthquakes. When compared with solutions from previous studies, based on many polarities and 〈span〉ad hoc〈/span〉 path‐specific velocity models, we obtained in both cases the same mechanism with a single 1D model and a single‐station polarity constraint. The envelope inversion is a promising technique that might be useful in similar sparse networks, such as the one in Brazil, where standard waveform inversion, in general, is not fully efficient.〈/span〉
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
    Published by Seismological Society of America (SSA)
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  • 5
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    Incorporating Descriptive Metadata into Seismic Source Zone Models for Seismic-Hazard Assessment: A Case Study of the Azores-West Iberian Region (2014)
    Seismological Society of America (SSA)
    Details
    Publication Date: 2014-06-12
    Description: In probabilistic seismic-hazard analysis (PSHA), seismic source zone (SSZ) models are widely used to account for the contribution to the hazard from earthquakes not directly correlated with geological structures. Notwithstanding the impact of SSZ models in PSHA, the theoretical framework underlying SSZ models and the criteria used to delineate the SSZs are seldom explicitly stated and suitably documented. In this paper, we propose a methodological framework to develop and document SSZ models, which includes (1) an assessment of the appropriate scale and degree of stationarity, (2) an assessment of seismicity catalog completeness-related issues, and (3) an evaluation and credibility ranking of physical criteria used to delineate the boundaries of the SSZs. We also emphasize the need for SSZ models to be supported by a comprehensive set of metadata documenting both the unique characteristics of each SSZ and the criteria used to delineate its boundaries. This procedure ensures that the uncertainties in the model can be properly addressed in the PSHA and that the model can be easily updated whenever new data are available. The proposed methodology is illustrated using the SSZ model developed for the Azores–West Iberian region in the context of the Seismic Hazard Harmonization in Europe project (project SHARE) and some of the most relevant SSZs are discussed in detail. Online Material: Tables describing characteristics and boundaries of the seismic source zones.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
    Published by Seismological Society of America (SSA)
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  • 6
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    Including the sub-grid scale plume rise of vegetation fires in low resolution atmospheric transport models (2006)
    Copernicus
    Details
    Publication Date: 2006-11-17
    Description: We describe and begin to evaluate a parameterization to include the vertical transport of hot gases and particles emitted from biomass burning in low resolution atmospheric-chemistry transport models. This sub-grid transport mechanism is simulated by embedding a 1-D cloud-resolving model with appropriate lower boundary conditions in each column of the 3-D host model. Through assimilation of remote sensing fire products, we recognize which columns have fires. Using a land use dataset appropriate fire properties are selected. The host model provides the environmental conditions, allowing the plume rise to be simulated explicitly. The derived height of the plume is then used in the source emission field of the host model to determine the effective injection height, releasing the material emitted during the flaming phase at this height. Model results are compared with CO aircraft profiles from an Amazon basin field campaign and with satellite data, showing the huge impact that this mechanism has on model performance. We also show the relative role of each main vertical transport mechanisms, shallow and deep moist convection and the pyro-convection (dry or moist) induced by vegetation fires, on the distribution of biomass burning CO emissions in the troposphere.
    Electronic ISSN: 1680-7375
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 7
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    Turbulence dissipation rate derivation for meandering occurrences in a stable planetary boundary layer (2008)
    Copernicus
    Details
    Publication Date: 2008-03-25
    Description: A new formulation for the turbulence dissipation rate ε occurring in meandering conditions has been presented. The derivation consists of a MacLaurin series expansion of a lateral dispersion parameter that represents cases in which turbulence and oscillatory movements associated to the meandering events coexist. The new formulation presents the identical physical premises contained in the classical and largely used one, but the new formulation derived from meandering situations is expressed in terms of the loop parameter m that controls the absolute value of the negative lobe in the meandering autocorrelation function. Therefore, the m magnitude regulates the turbulence dissipation rate. This dissipation rate decreases for cases in which turbulence and low frequency horizontal wind oscillations coexist and increases for a fully developed turbulence. Furthermore, a statistical comparison to observed concentration data shows that the alternative relation for the turbulent dissipation rate occurring in situations of meandering enhanced dispersion is suitable for applications in Lagrangian Stochastic dispersion models.
    Print ISSN: 1680-7316
    Electronic ISSN: 1680-7324
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 8
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    Biomass burning fuel consumption rates: a field measurement database (2014)
    Copernicus
    Details
    Publication Date: 2014-06-05
    Description: Landscape fires show large variability in the amount of biomass or fuel consumed per unit area burned. These fuel consumption (FC) rates depend on the biomass available to burn and the fraction of the biomass that is actually combusted, and can be combined with estimates of area burned to assess emissions. While burned area can be detected from space and estimates are becoming more reliable due to improved algorithms and sensors, FC rates are either modeled or taken selectively from the literature. We compiled the peer-reviewed literature on FC rates for various biomes and fuel categories to better understand FC rates and variability, and to provide a~database that can be used to constrain biogeochemical models with fire modules. We compiled in total 76 studies covering 10 biomes including savanna (15 studies, average FC of 4.6 t DM (dry matter) ha−1), tropical forest (n = 19, FC = 126), temperate forest (n = 11, FC = 93), boreal forest (n = 16, FC = 39), pasture (n = 6, FC = 28), crop residue (n = 4, FC = 6.5), chaparral (n = 2, FC = 32), tropical peatland (n = 4, FC = 314), boreal peatland (n = 2, FC = 42), and tundra (n = 1, FC = 40). Within biomes the regional variability in the number of measurements was sometimes large, with e.g. only 3 measurement locations in boreal Russia and 35 sites in North America. Substantial regional differences were found within the defined biomes: for example FC rates of temperate pine forests in the USA were 38% higher than Australian forests dominated by eucalypt trees. Besides showing the differences between biomes, FC estimates were also grouped into different fuel classes. Our results highlight the large variability in FC rates, not only between biomes but also within biomes and fuel classes. This implies that care should be taken with using averaged values, and our comparison with FC rates from GFED3 indicates that also modeling studies have difficulty in representing the dynamics governing FC.
    Print ISSN: 1810-6277
    Electronic ISSN: 1810-6285
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 9
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    Turbulence dissipation rate derivation for meandering occurrences in a stable planetary boundary layer (2007)
    Copernicus
    Details
    Publication Date: 2007-10-26
    Description: A new formulation for the turbulence dissipation rate ε occurring in meandering conditions has been presented. The derivation consists of a MacLaurin series expansion of a lateral dispersion parameter that represents cases in which turbulence and oscillatory movements associated to the meandering events coexist. The new formulation presents the identical physical premises contained in the classical and largely used one, but the new formulation derived from meandering situations is expressed in terms of the loop parameter m that controls the absolute value of the negative lobe in the meandering autocorrelation function. Therefore, the m magnitude regulates the turbulence dissipation rate. This dissipation rate decreases for cases in which turbulence and low frequency horizontal wind oscillations coexist and increases for a fully developed turbulence. Furthermore, a statistical comparison to observed concentration data shows that the alternative relation for the turbulent dissipation rate occurring in situations of meandering enhanced dispersion is suitable for applications in Lagrangian Stochastic dispersion models.
    Electronic ISSN: 1680-7375
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 10
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    Including the sub-grid scale plume rise of vegetation fires in low resolution atmospheric transport models (2007)
    Copernicus
    Details
    Publication Date: 2007-07-02
    Description: We describe and begin to evaluate a parameterization to include the vertical transport of hot gases and particles emitted from biomass burning in low resolution atmospheric-chemistry transport models. This sub-grid transport mechanism is simulated by embedding a 1-D cloud-resolving model with appropriate lower boundary conditions in each column of the 3-D host model. Through assimilation of remote sensing fire products, we recognize which columns have fires. Using a land use dataset appropriate fire properties are selected. The host model provides the environmental conditions, allowing the plume rise to be simulated explicitly. The derived height of the plume is then used in the source emission field of the host model to determine the effective injection height, releasing the material emitted during the flaming phase at this height. Model results are compared with CO aircraft profiles from an Amazon basin field campaign and with satellite data, showing the huge impact that this mechanism has on model performance. We also show the relative role of each main vertical transport mechanisms, shallow and deep moist convection and the pyro-convection (dry or moist) induced by vegetation fires, on the distribution of biomass burning CO emissions in the troposphere.
    Print ISSN: 1680-7316
    Electronic ISSN: 1680-7324
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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