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991.
Christopher E. Brehme Patrice McCarron Heather Tetreault 《The Professional geographer》2013,65(1):98-109
As coastlines face increased development pressure, it is important to have the best available spatial information on coastal activities, including commercial fishing. This article describes the creation of a fine-scale spatial representation of lobster fishing activity along the Maine coast of the United States using a combination of participatory geographic information systems (GIS) and dasymetric mapping methods. These methods are employed here to support data collection from a large number of active lobster harvesters while maintaining individual privacy. The resulting representation of the fishery is designed as a planning tool for identifying potential interactions between marine resources and human activities. 相似文献
992.
AbstractWe have contrived a model E(αω) α μ?1ω?p+1(ω 2?ω i 2)?+ for the distribution of internal wave energy in horizontal wavenumber, frequency-space, with wavenumber α extending to some upper limit μ(ω) α ω r-1 (ω 2?ω i 2)½, and frequency ω extending from the inertial frequency ω i to the local Väisälä frequency n(y). The spectrum is portrayed as an equivalent continuum to which the modal structure (if it exists) is not vital. We assume horizontal isotropy, E(α, ω) = 2παE(α1, α2, ω), with α1, α2 designating components of α. Certain moments of E(α1, α2, ω) can be derived from observations. (i) Moored (or freely floating) devices measuring horizontal current u(t), vertical displacement η(t),…, yield the frequency spectra F (u,η,…)(ω) = ∫∫ (U 2, Z 2,…)E(α1, ∞2, ω) dα1 dα2, where U, Z,… are the appropriate wave functions. (ii) Similarly towed measurements give the wavenumber spectrum F (…)(α1) = ∫∫… dα2 dω. (iii) Moored measurements horizontally separated by X yield the coherence spectrum R(X, ω) which is related to the horizontal cosine transform ∫∫ E(α1, α2 ω) cos α1 Xdα1 dα1. (iv) Moored measurements vertically separated by Y yield R(Y, ω) and (v) towed measurements vertically separated yield R(Y, α1), and these are related to similar vertical Fourier transforms. Away from inertial frequencies, our model E(α, ω) α ω ?p-r for α ≦ μ ω ω r, yields F(ω) ∞ ω ?p, F(α1) ∞ α1 ?q, with q = (p + r ? 1)/r. The observed moored and towed spectra suggest p and q between 5/3 and 2, yielding r between 2/3 and 3/2, inconsistent with a value of r = 2 derived from Webster's measurements of moored vertical coherence. We ascribe Webster's result to the oceanic fine-structure. Our choice (p, q, r) = (2, 2, 1) is then not inconsistent with existing evidence. The spectrum is E(∞, ω) ∞ ω ?1(ω 2?ω i 2 ?1, and the α-bandwith μ ∞ (ω 2?ω i 2)+ is equivalent to about 20 modes. Finally, we consider the frequency-of-encounter spectra F([sgrave]) at any towing speed S, approaching F(ω) as S ≦ S o, and F(α1) for α1 = [sgrave]/S as S ≧ S o, where S o = 0(1 km/h) is the relevant Doppler velocity scale. 相似文献
993.
Tenley M. Conway Christopher C. Wellen 《International journal of geographical information science》2013,27(10):1613-1631
Biogeographers have developed a new generation of statistical models called presence-only models, which require no data concerning the absence of a species and do not assume that the absence of a species indicates habitat unsuitability. Both characteristics are especially useful when modeling a species that is actively spreading across a landscape. Although urban expansion is sometimes equated to an invading species, the applicability of presence-only models has not yet been explored when modeling urban growth. This article compares predictions of urban growth using a presence-only model (ecological niche factor analysis) and a more traditional presence–absence model (logistic regression). An additional model used pseudo-absence sites, from the presence-only model output, as input into the presence–absence model. The models were applied to New Jersey's Barnegat Bay Watershed. Overall, the traditional presence–absence model performed the best, although the presence-only model was sufficiently similar to warrant further exploration of presence-only models when no reliable absence data (i.e., locations where no conversion occurred) exists. However, due to data-formatting requirements of the presence-only model, it is difficult to accommodate data pertaining to administrative boundaries, which are inherently Boolean. Finally, the output based on the pseudo-absence approach overpredicted urban conversion when compared to the other approaches. 相似文献
994.
Christopher J. Amante 《International journal of geographical information science》2013,27(11):2188-2217
ABSTRACTFuture sea-level rise will likely expand the inland extent of storm surge inundation and, in turn, increase the vulnerability of the people, properties and economies of coastal communities. Modeling future storm surge inundation enhanced by sea-level rise uses numerous data sources with inherent uncertainties. There is uncertainty in (1) hydrodynamic storm surge models, (2) future sea-level rise projections, and (3) topographic digital elevation models representing the height of the coastal land surface. This study implemented a Monte Carlo approach to incorporate the uncertainties of these data sources and model the future 1% flood zone extent in the Tottenville neighborhood of New York City (NYC) in a probabilistic, geographical information science (GIS) framework. Generated spatiotemporal statistical products indicate a range of possible future flood zone extents that results from the uncertainties of the data sources and from the terrain itself. Small changes in the modeled land and water heights within the estimated uncertainties of the data sources results in larger uncertainty in the future flood zone extent in low-lying areas with smaller terrain slope. An interactive web map, UncertainSeas.com, visualizes these statistical products and can inform coastal management policies to reduce the vulnerability of Tottenville, NYC to future coastal inundation. 相似文献
995.
Joachim W. Stock Christopher S. Boxe Ralph Lehmann J. Lee Grenfell A. Beate C. Patzer Heike Rauer Yuk L. Yung 《Icarus》2012,219(1):13-24
The chemical composition of a planetary atmosphere plays an important role for atmospheric structure, stability, and evolution. Potentially complex interactions between chemical species do not often allow for an easy understanding of the underlying chemical mechanisms governing the atmospheric composition. In particular, trace species can affect the abundance of major species by acting in catalytic cycles. On Mars, such cycles even control the abundance of its main atmospheric constituent CO2. The identification of catalytic cycles (or more generally chemical pathways) by hand is quite demanding. Hence, the application of computer algorithms is beneficial in order to analyze complex chemical reaction networks. Here, we have performed the first automated quantified chemical pathways analysis of the Martian atmosphere with respect to CO2-production in a given reaction system. For this, we applied the Pathway Analysis Program (PAP) to output data from the Caltech/JPL photochemical Mars model. All dominant chemical pathways directly related to the global CO2-production have been quantified as a function of height up to 86 km. We quantitatively show that CO2-production is dominated by chemical pathways involving HOx and Ox. In addition, we find that NOx in combination with HOx and Ox exhibits a non-negligible contribution to CO2-production, especially in Mars’ lower atmosphere. This study reveals that only a small number of chemical pathways contribute significantly to the atmospheric abundance of CO2 on Mars; their contributions to CO2-production vary considerably with altitude. This analysis also endorses the importance of transport processes in governing CO2-stability in the Martian atmosphere. Lastly, we identify a previously unknown chemical pathway involving HOx, Ox, and HO2-photodissociation, contributing 8% towards global CO2-production by chemical pathways using recommended up-to-date values for reaction rate coefficients. 相似文献
996.
David J. JOSWIAK Donald E. BROWNLEE Graciela MATRAJT Andrew J. WESTPHAL Christopher J. SNEAD Zack GAINSFORTH 《Meteoritics & planetary science》2012,47(4):471-524
Abstract– Transmission electron microscopy examination of 87 large fragments from 16 carrot‐shaped and bulbous Stardust (SD) tracks was performed to study the range and diversity of materials present in comet Wild 2. Olivines and low‐Ca pyroxenes represent the largest proportions of fragments observed; however, a wide range of minerals and rocks were found including probable ferromagnesian, Al‐rich and Si‐rich chondrule fragments, a refractory inclusion, possible matrix mineral/lithic clasts, and probable condensate minerals. These materials, combined with fine‐grained components in the tracks, are analogous to components in unequilibrated chondrite meteorites and cluster interplanetary dust particles (IDPs). Two unusual lithologies in the bulbous tracks are only observed in chondritic porous IDPs and may have direct links to IDPs. The absence of phyllosilicates indicates that comet Wild 2 may be a “dry” comet that did not accrete or form significant amounts of hydrated phases. Some large mineral fragments in the SD tracks are analogous to large mineral IDPs. The large variations of the coarse‐grained components within and between all 16 tracks show that comet Wild 2 is mineralogically diverse and unequilibrated on nearly all scales and must have accreted materials from diverse source regions that were widely dispersed throughout the solar nebula. 相似文献
997.
Huaxia Yao Timothy Field Christopher McConnell Andy Beaton April L. James 《水文研究》2018,32(12):1894-1908
Snow water equivalent (SWE) is an important indicator used in hydrology, water resources, and climate change impact. There are various methods of estimating SWE (falling in 3 categories: indirect sensors, empirical models, and process‐based models), but few studies that provide comparison across these different categories to help users make decisions on monitoring site design or method selection. Five SWE estimation methods were compared against manual snow course data collected over 2 years (2015–2016) from the Dorset Environmental Science Centre, including the gamma‐radiation‐based CS725 sensor, 3 empirical estimation models (Sexstone snow density model, McCreight & Small snow density model, and a meteorology‐based model), and the University of British Columbia Watershed Model snow energy‐balance model. Snow depth, density, and SWE were measured at the Dorset Environmental Science Centre weather station in south‐central Ontario, on a daily basis over 6 winters from 2011 to 2016. The 2 snow density‐based models, requiring daily snow depth as input, gave the best performance (R2 of .92 and .92 for McCreight & Small and Sexstone models, respectively). The CS725 sensor that receives radiation coming from soil penetrating the snowpack provided the same performance (R2 = .92), proving that the sensor is an applicable method, although it is expensive. The meteorology‐based empirical model, requiring daily climate data including temperature, precipitation and solar radiation, gave the poorest performance (R2 = .77). The energy‐balance‐based University of British Columbia Watershed Model snow module, only requiring climate data, worked better than the empirical meteorology‐based model (R2 = .9) but performed worse than the density models or CS725 sensor. Given differences in application objectives, site conditions, and budget, this comparison across SWE estimation methods may help users choose a suitable method. For ongoing and new monitoring sites, installation of a CS725 sensor coupled with intermittent manual snow course measurements (e.g., weekly) is recommended for further SWE method estimation testing and development of a snow density model. 相似文献
998.
Trond Slagstad Evgeniy Kulakov Christopher L. Kirkland Nick M. W. Roberts Morgan Ganerd 《地学学报》2019,31(5):430-437
The Grenville, Sveconorwegian, and Sunsas orogens are typically inferred to reflect collision between Laurentia, Baltica, and Amazonia at ca. 1.0 Ga, forming a central portion of the Rodinia supercontinent. This triple‐junction configuration is often nearly identical in otherwise diverse Rodinia reconstructions. However, available geological data suggest that although the Grenville and Sveconorwegian provinces shared a similar tectonic evolution from pre‐1.8 to ca. 1.5 Ga, they record distinctly different tectonic histories leading up to, during, and possibly following Grenville–Sveconorwegian orogenesis. Moreover, palaeomagnetic data suggest the two continents were separated at peak orogenesis, further invalidating any direct correlation. A number of possible interpretations are permissible with available geological and palaeomagnetic data, of which a “classic” triple‐junction configuration appears least likely. In contrast to the commonly inferred intertwined Proterozoic evolution of Baltica and Laurentia, the possibility remains that they were unrelated for a billion years between 1.5 and 0.45 Ga. 相似文献
999.
Aurélie Genries Walter Finsinger Hans Asnong Yves Bergeron Christopher Carcaillet Michelle Garneau Christelle Hély Adam A. Ali 《第四纪科学杂志》2012,27(7):745-756
We analysed charcoal and pollen from sediments obtained from two lakes in the northwestern mixed‐wood Canadian boreal forest in order to reconstruct fire‐return intervals and vegetation dynamics over the last 8000 years. Sites were selected with contrasting soil properties (mesic versus dry‐sandy soils), allowing an estimation of the potential influence of soils on long‐term vegetation and fire dynamics. The sites likely experienced fewer fires during the period extending from 8000 to 4000 cal. a BP than over the last 4000 years. At both sites, eastern white pine (Pinus strobus) populations were most extensive shortly after deglaciation, with vegetation later shifting towards mixed woodlands with less P. strobus and more extensive Picea and Pinus banksiana populations. This gradual vegetation shift was probably induced by the establishment of colder and moister conditions along with a fire‐regime change. In spite of the parallel long‐term vegetation trajectories, vegetation composition differed between the two sites in both the past and present. Whereas Picea was more abundant at the mesic site, the fire‐adapted P. banksiana populations were more extensive at the sandy‐soil site. These differences in vegetation composition indicate that, in addition to climate changes and fire occurrence, soil properties also influenced vegetation dynamics. A likely increase in fire frequency in the Canadian boreal forest during the 21st century might therefore favour the expansion of these two disturbance‐adapted trees with spatial heterogeneity in the populations due to varying soil types. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
1000.
Ravindra Dwivedi Thomas Meixner Jennifer C. McIntosh P.A. Ty Ferr Christopher J. Eastoe Guo‐Yue Niu Rebecca L. Minor Greg A. Barron‐Gafford Jon Chorover 《水文研究》2019,33(4):476-494
High‐elevation mountain catchments are often subject to large climatic and topographic gradients. Therefore, high‐density hydrogeochemical observations are needed to understand water sources to streamflow and the temporal and spatial behaviour of flow paths. These sources and flow paths vary seasonally, which dictates short‐term storage and the flux of water in the critical zone (CZ) and affect long‐term CZ evolution. This study utilizes multiyear observations of chemical compositions and water residence times from the Santa Catalina Mountains Critical Zone Observatory, Tucson, Arizona to develop and evaluate competing conceptual models of seasonal streamflow generation. These models were tested using endmember mixing analysis, baseflow recession analysis, and tritium model “ages” of various catchment water sources. A conceptual model involving four endmembers (precipitation, soil water, shallow, and deep groundwater) provided the best match to observations. On average, precipitation contributes 39–69% (55 ± 16%), soil water contributes 25–56% (41 ± 16%), shallow groundwater contributes 1–5% (3 ± 2%), and deep groundwater contributes ~0–3% (1 ± 1%) towards annual streamflow. The mixing space comprised two principal planes formed by (a) precipitation‐soil water‐deep groundwater (dry and summer monsoon season samples) and (b) precipitation‐soil water‐shallow groundwater (winter season samples). Groundwater contribution was most important during the wet winter season. During periods of high dynamic groundwater storage and increased hydrologic connectivity (i.e., spring snowmelt), stream water was more geochemically heterogeneous, that is, geochemical heterogeneity of stream water is storage‐dependent. Endmember mixing analysis and 3H model age results indicate that only 1.4 ± 0.3% of the long‐term annual precipitation becomes deep CZ groundwater flux that influences long‐term deep CZ development through both intercatchment and intracatchment deep groundwater flows. 相似文献