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501.
502.
Elizabeth A. Masden Daniel T. Haydon Robert W. Furness 《Marine pollution bulletin》2010,60(7):1085-1091
Proposals for wind farms in areas of known importance for breeding seabirds highlight the need to understand the impacts of these structures. Using an energetic modelling approach, we examine the effects of wind farms as barriers to movement on seabirds of differing morphology. Additional costs, expressed in relation to typical daily energetic expenditures, were highest per unit flight for seabirds with high wing loadings, such as cormorants. Taking species-specific differences into account, costs were relatively higher in terns, due to the high daily frequency of foraging flights. For all species, costs of extra flight to avoid a wind farm appear much less than those imposed by low food abundance or adverse weather, although such costs will be additive to these. We conclude that adopting a species-specific approach is essential when assessing the impacts of wind farms on breeding seabird populations, to fully anticipate the effects of avoidance flights. 相似文献
503.
The Geology and Petroleum Resources of Kansas: A Review From Alpha to Omega or From the Pleistocene to the Precambrian 总被引:1,自引:0,他引:1
Daniel F. Merriam 《Natural Resources Research》2010,19(4):293-316
The geological story of Kansas is told through the rocks that are present. It is a simple story in generalities but complex
in detail. Knowing the story, gives insight into understanding the occurrence and location of possible economic valuable minerals,
such as petroleum. This is a brief review of Kansas geology with respect to the known occurrence of oil and gas. Kansas is
part of the Midcontinent oil province with oil having been discovered 150 years ago and commercial production commencing in
1873. Although many prospects remain in Kansas, the state has gone from the number 1 producer in the U.S. in 1916 to 8th today.
Exploration for new oil and gas production therefore is going to have to be more imaginative and utilize new approaches and
techniques to find the elusive petroleum. There are possibilities however for the prospector who can search diligently. Although
the big fields probably have been discovered, the prospects today are deeper, in more undetectable traps, and in essentially
untested places. 相似文献
504.
A 1-D General Ocean Turbulence Model that includes the effects of sediment-induced stratification is shown to simulate the observed onshore and offshore migration of a nearshore sandbar. The only two free parameters of the model, the bed reference concentration and the sediment diffusivity, are taken from the literature, rather than tuned to the data used here. The model results suggest that predictions of onshore bar migration, in which wave-induced sediment transport confined to within a few centimeters of the bottom dominates, are not greatly affected by accounting for buoyancy effects. The model results also suggest that both mean flows and waves transport sediment during offshore bar migration, with different components of transport dominating at different cross-shore locations across the bar-trough bathymetry. Neglecting the effects of sediment-induced stratification results in higher model skill during the largest waves, likely because the excess turbulence production simulated by the non-stratified model is counterbalanced by neglected breaking-wave-generated turbulence. Considering both onshore and offshore migration, the model that includes sediment-induced stratification has higher skill than the model without stratification. 相似文献
505.
Michael C. Kelley Geoffrey Crowley Daniel R. Weimer 《Journal of Atmospheric and Solar》2010,72(4):302-308
The magnetic storm on November 2004 was characterized by a high solar wind pressure and thus offers a unique opportunity to test the Hill–Siscoe formula (H–S) for the polar cap potential (PCP). To estimate the polar cap potential, we use the Weimer Statistical Convection Model (WCM), and the Assimilative Mapping of Ionospheric Electrodynamics Model (AMIE), based on ingestion of a number of data sets. H–S is in excellent agreement with WCM, and with AMIE during times when DMSP is used in the latter. The implication is that the AMIE conductivity model yields conductivities that are too high by a factor of 2–3. Both H–S and WCM display saturation effects, although WCM is more severe. The two methods track well until an IEF of about 20 mV/m occurs, where H–S continues to increase while WCM levels off. Even at high electric field values, the pressure increases the denominator of the H–S formula by 60%, keeping the potential lower than its saturation value. There are several H–S points above 250 kV, even up to 400 kV, that are not found in WCM and occur right after a rapid transition from Bz north to south. For Bz north, we find evidence for a saturation effect on the PCP at large IEF, little effect as a function of solar wind velocity, and an increase of the PCP with increasing pressure. This seems to rule out viscous interaction but may involve geometric changes in the high-altitude polar cusp that affect recombination there for Bz north. 相似文献
506.
Danny Arroyo Daniel García Mario Ordaz Mauricio Alexander Mora Shri Krishna Singh 《Journal of Seismology》2010,14(4):769-785
We derive strong ground-motion relations for horizontal components of pseudo-acceleration response spectra from Mexican interplate
earthquakes at rock sites (NEHRP B class) in the forearc region. The functional form is obtained from the analytical solution
of a circular finite-source model. For the regression analysis we use a recently proposed multivariate Bayesian technique.
The resulting model has similar accuracy as those models derived from regional and worldwide subduction-zone databases. However,
there are significant differences in the estimations computed from our model and other models. First, our results reveal that
attenuation in Mexico tends to be stronger than that of worldwide relations, especially for large events. Second, our model
predicts ground motions for large earthquakes at close distances to the source that are considerably larger than the estimations
of global models. Lack of data in this range makes it difficult to identify the most appropriate model for this scenario.
Nevertheless, according to the available data at the city of Acapulco, our model seems to estimate seismic hazard more adequately
than the other models. These new relations may be useful in computing seismic hazard for the Mexican forearc region, where
no similar equations had been yet proposed. 相似文献
507.
Some previous studies demonstrated that model bias has a strong impact on the quality of long-term prognostic model simulations
of the sub-polar North Atlantic Ocean. Relatively strong bias of water mass characteristics is observed in both eddy-permitting
and eddy-resolving simulations, suggesting that an increase of model resolution does not reduce significantly the model bias.
This study is an attempt to quantify the impact of model bias on the simulated water mass and circulation characteristics
in an eddy-permitting model of the sub-polar ocean. This is done through comparison of eddy-permitting prognostic model simulations
with the results from two other runs in which the bias is constrained by using spectral nudging. In the first run, the temperature
and salinity are nudged towards climatology in the whole column. In the second run, the spectral nudging is applied in the
surface 30 m layer and at depths below 560 m only. The biases of the model characteristics of the unconstrained run are similar
to those reported in previous eddy-permitting and eddy-resolving studies. The salinity in the surface and intermediate waters
of the Labrador Sea waters increases with respect to the climatology, which reduces the stability of the water column. The
deep convection in the unconstrained run is artificially intensified and the transport in the sub-polar gyre stronger than
in the observations. In particular, the transport of relatively salty and warm Irminger waters into the Labrador Sea is unrealistically
high. While the water mass temperature and salinity in the run with spectral nudging in the whole column are closest to the
observations, the depth of the winter convection is underestimated in the model. The water mass characteristics and water
transport in the run with spectral nudging in the surface and deep layers only are close to observations and at the same time
represent well the deep convection in terms of its intensity and position. The source of the bias in the prognostic model
run is discussed. 相似文献
508.
Geomorphic monitoring and response to two dam removals: rivers Urumea and Leitzaran (Basque Country,Spain)
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Askoa Ibisate Alfredo Ollero Daniel Ballarín Jesús Horacio Daniel Mora Amaia Mesanza Carles Ferrer‐Boix Vanesa Acín David Granado Juan Pedro Martín‐Vide 《地球表面变化过程与地形》2016,41(15):2239-2255
Dam removal has been demonstrated to be one of the most frequent and effective fluvial restoration actions but at most dam removals, especially of small dams, there has been little geomorphological monitoring. The results of the geomorphological monitoring implemented in two dams in the rivers Urumea and Leitzaran (northern Spain) are presented. The one from the River Urumea, originally 3.5 m high and impounding 500 m of river course, was removed instantaneously whereas that in the River Leitzaran, 12.5 m high, and impounding 1500 m of river course, is in its second phase of a four‐stage removal process. Changes in channel morphology, sediment size and mobility and river bed morphologies were assessed. The monitoring included several different techniques: topographical measurements of the channel, terrestrial laser scanner measurements of river bed and bars, sediment grain size and transport; all of them repeated in four (May, August, November 2011 and May 2012) and five (July and September 2013, April and August 2014 and June 2015) fieldwork campaigns in the River Urumea and River Leitzaran, respectively. Geomorphic responses of both dam removals are presented, and compared. Morphological channel adjustments occurred mainly shortly after dam removals, but with differences among the one removed instantaneously, that was immediate, whereas that conducted by stages took longer. Degradational processes were observed upstream of both dams (up to 1.2 m and 4 m in the River Urumea and River Leitzaran, respectively), but also aggradational processes (pool filling), upstream of Inturia Dam (2.85 m at least). Less evident aggradational processes were observed downstream of the dams (up to 0.37 m and 0.50 m in the River Urumea and River Leitzaran, respectively). Flood events, especially a 100 year flood registered during the monitoring period of Mendaraz Dam removal, reactivated geomorphological processes as incision and bank erosion, whereas longitudinal profile recovery, grain‐size sorting and upstream erosion took longer. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
509.
The aim of this paper is to describe a managing system for a unique Romanian database of historical seismograms and complementary documentation (metadata) and its dissemination and analysis procedure. For this study, 5188 historical seismograms recorded between 1903 and 1957 by the Romanian seismological observatories (Bucharest-Filaret, Foc?ani, Bac?u, Vrincioaia, Câmpulung-Muscel, Ia?i) were used. In order to reconsider the historical instrumental data, the analog seismograms are converted to digital images and digital waveforms (digitization/ vectorialisation). First, we applied a careful scanning procedure of the seismograms and related material (seismic bulletins, station books, etc.). In a next step, the high resolution scanned seismograms will be processed to obtain the digital/numeric waveforms. We used a Colortrac Smartlf Cx40 scanner which provides images in TIFF or JPG format. For digitization the algorithm Teseo2 developed by the National Institute of Geophysics and Volcanology in Rome (Italy), within the framework of the SISMOS Project, will be used. 相似文献
510.
Carlos M. Duarte Daniel J. Conley Jacob Carstensen María Sánchez-Camacho 《Estuaries and Coasts》2009,32(1):29-36
The implicit assumption of many scientific and regulatory frameworks that ecosystems impacted by human pressures may be reverted
to their original condition by suppressing the pressure was tested using coastal eutrophication. The response to nutrient
abatement of four thoroughly studied coastal ecosystems that received increased nutrient inputs between the 1970s and the
1980s showed that the trajectories of these ecosystems were not directly reversible. All four ecosystems displayed convoluted
trajectories that failed to return to the reference status upon nutrient reduction. This failure is proposed to result from
the broad changes in environmental conditions, all affecting ecosystem dynamics, that occurred over the 30 years spanning
from the onset of eutrophication to the reduction of nutrient levels. Understanding ecosystem response to multiple shifting
baselines is essential to set reliable targets for restoration efforts. 相似文献