Climatological aspects of convective parameters from the NCAR/NCEP reanalysis   总被引：1，自引：0，他引：1  

Harold E. Brooks  Aaron R. Anderson  Kathrin Riemann  Irina Ebbers  Heather Flachs 《Atmospheric Research》2007,83(2-4):294-305

Annual cycles of convectively important atmospheric parameters have been computed for a variety of from the National Center for Atmospheric Research (NCAR)/National Centers for Environmental Prediction (NCEP) global reanalysis, using 7 years of reanalysis data. Regions in the central United States show stronger seasonality in combinations of thermodynamic parameters than found elsewhere in North America or Europe. As a result, there is a period of time in spring and early summer when climatological mean conditions are supportive of severe thunderstorms.The annual cycles help in understanding the large-scale processes that lead to the combination of atmospheric ingredients necessary for strong convection. This, in turn, lays groundwork for possible changes in distribution of the environments associated with possible global climate change.  相似文献   

Hormone loads exported by a tile‐drained agroecosystem receiving animal wastes          下载免费PDF全文

Heather E. Gall  Stephen A. Sassman  Byron Jenkinson  Linda S. Lee  Chad T. Jafvert 《水文研究》2014,28(3):1318-1328

Little is known regarding hormone export from tile‐drained agricultural fields despite the widespread presence of tile drains in the Midwestern United States. By intensively measuring water flow rates and hormone concentrations in four subsurface tile drains and three receiving ditches at a working Midwest farm, hormone fluxes and loads from the tile‐drained fields were quantified. Before and during the 17‐month study period (January 2009 – May 2010), the associated farm fields received various animal waste applications (beef, dairy, poultry, sheep, and swine). Hormones monitored included the estrogens17β‐ and 17α‐estradiol, estrone, and estriol; the natural androgens testosterone, and androstenedione; and the synthetic androgens 17β‐ and 17α‐trenbolone, and trendione. Hormone loads measured in the ditches for three drainage areas during the entire 17‐month study period were in ranges of 16–58 mg/ha for total estrogens, 6.8–19 mg/ha for natural androgens, and 4.2–44 mg/ha for synthetic androgens. Because higher hormone concentrations generally occurred during discrete periods of increased flow, high flow rates often were associated with a disproportionately high hormone flux. For example, 80% of total estrogens and natural androgens exported into the ditches occurred during only 9–26% of the study period, coinciding with the most significant storm events. In addition, hormone fluxes were highest during storm events that occurred shortly after animal waste applications. Therefore, to effectively reduce hormone loads exported to downstream aquatic ecosystems in the absence of any application reduction, the short periods during which high‐flow events occur must be targeted. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Groundwater cooling of a supercomputer in Perth,Western Australia: hydrogeological simulations and thermal sustainability     

Heather A. Sheldon  Peter M. Schaubs  Praveen K. Rachakonda  Michael G. Trefry  Lynn B. Reid  Daniel R. Lester  Guy Metcalfe  Thomas Poulet  Klaus Regenauer-Lieb 《Hydrogeology Journal》2015,23(8):1831-1849

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http://www.sciencedirect.com/science/article/pii/S1674987114000334     

Weronika Gorczyk  Hugh Smithies  Fawna Korhonen  Heather Howard  Raphael Quentin De Gromard 《地学前缘(英文版)》2015,6(1):23-37

The Musgrave Province developed at the nexus of the North,West and South Australian cratons and its Mesoproterozoic evolution incorporates a 100 Ma period of ultra-high temperature(UHT) metamorphism from ca.1220 to ca.1120 Ma.This was accompanied by high-temperature A-type granitic magmatism over an 80 Ma period,sourced in part from mantle-derived components and emplaced as a series of pulsed events that also coincide with peaks in UHT metamorphism.The tectonic setting for this thermal event(the Musgrave Orogeny) is thought to have been intracontinental and the lithospheric architecture of the region is suggested to have had a major influence on the thermal evolution.We use a series of two dimensional,fully coupled thermo-mechanical-petrological numerical models to investigate the plausibility of initiating and prolonging UHT conditions under model setup conditions appropriate to the inferred tectonic setting and lithospheric architecture of the Musgrave Province.The results support the inferred tectonic framework for the Musgrave Orogeny,predicting periods of UHT metamorphism of up to 70 Ma,accompanied by thin crust and extensive magmatism derived from both crustal and mantle sources.The results also appear to be critically dependent upon the specific location of the Musgrave Province,constrained between thicker cratonic masses.  相似文献   

Emerging Geographies of Conservation and Indigenous Land in Australia     

Heather Moorcroft  Michael Adams 《The Australian geographer》2014,45(4):485-504

International examples of interactions between Indigenous peoples and the new conservation paradigm come mainly from developing countries and suggest divisions over priorities. As a Western settler society, Australia is at a critical time in conservation and Indigenous peoples' rights. Innovative approaches to conservation are promoted. The role and influence of non-governmental organisations is increasing. Indigenous peoples' rights to land are recognised and Indigenous involvement in conservation is growing. Yet, despite Australia being considered a leader in these arenas, particularly the latter, there has been little analysis of the relationship between innovative approaches to conservation and Indigenous Australians under the new paradigm. This paper describes how the spatial manifestations of approaches under the new conservation paradigm and Indigenous land in Australia are creating new geographies. We identify geographies of overlap, dichotomy and absence. The paper identifies research needs into these geographies, including: examining the influence of ‘recognition’ in engagements between conservation and Indigenous Australians; investigating the impacts of approaches under the new paradigm such as scaling-up, territorialism and differing governance structures on Indigenous Australians; and questioning the social responsibilities of the non-governmental organisations towards Indigenous Australians.  相似文献   

Recent environmental change in an upland reservoir catchment: a palaeoecological perspective     

Jessie Woodbridge  Heather J. Davies  Will H. Blake  Ralph M. Fyfe 《Journal of Paleolimnology》2014,52(3):229-244

Reservoirs provide important water resources and require careful management, through ecological monitoring, to identify and mitigate changes in water quality. Long-term data on vegetation changes and the impacts of human activities on reservoir water chemistry, however, are often limited. Setting restoration targets can therefore be problematic. Palaeoenvironmental research has made little use of reservoir sediments and there is great potential for palaeoecological data to be incorporated into management planning. Diatoms and pollen were analysed in sediment cores from Venford Reservoir, southwest England, to infer pH and land-use changes, respectively, over the last century. Diatom-inferred (DI) pH indicates that reservoir pH declined from ~pH 6.0 in the early part of the record and reached a low between AD 1920 and 1940 (~pH 5.6), which was likely associated with fossil fuel combustion and acid deposition. DI-pH then increased, but values remained relatively low, even in the most recent sediments (~pH 5.7), and the magnitude of inferred pH change over time was small. Land-use changes, such as increased grazing intensity and erosion, and establishment of pine plantations, also likely influenced reservoir water chemistry changes over time. Understanding the impacts of such factors on water chemistry has implications for future catchment land-use planning, which is essential for managing water resources. The pollen record indicates a shift from heather-dominated to grass-dominated vegetation since ~AD 1935–1950, which could be related to increased grazing intensity. The palaeoecological dataset is valuable as a long-term record against which short-term monitoring datasets and future changes can be assessed.  相似文献   

Effects of anthropogenic disturbance on the abundance and size of epibenthic jellyfish Cassiopea spp     

Stoner EW  Layman CA  Yeager LA  Hassett HM 《Marine pollution bulletin》2011,62(5):1109-1114

Jellyfish blooms in pelagic systems appear to be increasing on a global scale because of anthropogenic impacts, but much less is known about the link between human activities and epibenthic jellyfish abundance. The aim of this study was to investigate whether the epibenthic jellyfish, Cassiopea spp., were found in greater abundance, and attained larger sizes, in coastal habitats adjacent to high human population densities compared to sites adjacent to uninhabited areas on Abaco Island, Bahamas. Cassiopea spp. were found to be significantly more dense and larger in areas with high human population densities. Ambient nutrient levels and nutrient content of seagrass were elevated in high human population density sites, and may be one mechanism driving higher abundance and size of Cassiopea spp. Cassiopea spp. may have important effects on community structure and ecosystem function in critical coastal ecosystems (e.g., seagrass beds), and their impacts warrant further study.  相似文献   

A re-appraisal of the stratigraphy and volcanology of the Cerro Galán volcanic system,NW Argentina     

Chris B. Folkes  Heather M. Wright  Raymond A. F. Cas  Shanaka L. de Silva  Chiara Lesti  Jose G. Viramonte 《Bulletin of Volcanology》2011,73(10):1427-1454

From detailed fieldwork and biotite ⁴⁰Ar/³⁹Ar dating correlated with paleomagnetic analyses of lithic clasts, we present a revision of the stratigraphy, areal extent and volume estimates of ignimbrites in the Cerro Galán volcanic complex. We find evidence for nine distinct outflow ignimbrites, including two newly identified ignimbrites in the Toconquis Group (the Pitas and Vega Ignimbrites). Toconquis Group Ignimbrites (~5.60–4.51 Ma biotite ages) have been discovered to the southwest and north of the caldera, increasing their spatial extents from previous estimates. Previously thought to be contemporaneous, we distinguish the Real Grande Ignimbrite (4.68 ± 0.07 Ma biotite age) from the Cueva Negra Ignimbrite (3.77 ± 0.08 Ma biotite age). The form and collapse processes of the Cerro Galán caldera are also reassessed. Based on re-interpretation of the margins of the caldera, we find evidence for a fault-bounded trapdoor collapse hinged along a regional N-S fault on the eastern side of the caldera and accommodated on a N-S fault on the western caldera margin. The collapsed area defines a roughly isosceles trapezoid shape elongated E-W and with maximum dimensions 27 × 16 km. The Cerro Galán Ignimbrite (CGI; 2.08 ± 0.02 Ma sanidine age) outflow sheet extends to 40 km in all directions from the inferred structural margins, with a maximum runout distance of ~80 km to the north of the caldera. New deposit volume estimates confirm an increase in eruptive volume through time, wherein the Toconquis Group Ignimbrites increase in volume from the ~10 km³ Lower Merihuaca Ignimbrite to a maximum of ~390 km³ (Dense Rock Equivalent; DRE) with the Real Grande Ignimbrite. The climactic CGI has a revised volume of ~630 km³ (DRE), approximately two thirds of the commonly quoted value.  相似文献   

Columnar jointing in vapor-phase-altered,non-welded Cerro Galán Ignimbrite,Paycuqui, Argentina     

Heather M. N. Wright  Chiara Lesti  Raymond A. F. Cas  Massimiliano Porreca  José G. Viramonte  Chris B. Folkes  Guido Giordano 《Bulletin of Volcanology》2011,73(10):1567-1582

Columnar jointing is thought to occur primarily in lavas and welded pyroclastic flow deposits. However, the non-welded Cerro Galán Ignimbrite at Paycuqui, Argentina, contains well-developed columnar joints that are instead due to high-temperature vapor-phase alteration of the deposit, where devitrification and vapor-phase crystallization have increased the density and cohesion of the upper half of the section. Thermal remanent magnetization analyses of entrained lithic clasts indicate high emplacement temperatures, above 630°C, but the lack of welding textures indicates temperatures below the glass transition temperature. In order to remain below the glass transition at 630°C, the minimum cooling rate prior to deposition was 3.0 × 10⁻³–8.5 × 10⁻²°C/min (depending on the experimental data used for comparison). Alternatively, if the deposit was emplaced above the glass transition temperature, conductive cooling alone was insufficient to prevent welding. Crack patterns (average, 4.5 sides to each polygon) and column diameters (average, 75 cm) are consistent with relatively rapid cooling, where advective heat loss due to vapor fluxing increases cooling over simple conductive heat transfer. The presence of regularly spaced, complex radiating joint patterns is consistent with fumarolic gas rise, where volatiles originated in the valley-confined drainage system below. Joint spacing is a proxy for cooling rates and is controlled by depositional thickness/valley width. We suggest that the formation of joints in high-temperature, non-welded deposits is aided by the presence of underlying external water, where vapor transfer causes crystallization in pore spaces, densifies the deposit, and helps prevent welding.  相似文献   

Three decades of water quality measurements from the Upper Severn experimental catchments at Plynlimon,Wales: an openly accessible data resource for research,modelling, environmental management and education   总被引：1，自引：0，他引：1  

Colin Neal  Brian Reynolds  Dave Norris  James W. Kirchner  Margaret Neal  Phil Rowland  Heather Wickham  Sarah Harman  Linda Armstrong  Darren Sleep  Alan Lawlor  Clive Woods  Bronwen Williams  Matt Fry  Gwen Newton  Dan Wright 《水文研究》2011,25(24):3818-3830

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