The optical jet in 3C 31 on 15 arcsec scales     

J. H. Croston  M. Birkinshaw  E. Conway  R. L. Davies 《Monthly notices of the Royal Astronomical Society》2003,339(1):82-86

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NGC7538 Irs1 N: Modeling a Circumstellar Maser Disk     

M. Pestalozzi  M. Elitzur  J. Conway  R. Booth 《Astrophysics and Space Science》2005,295(1-2):231-236

We present an edge-on Keplerian disk model to explain the main component of the 12.2 and 6.7 GHz methanol maser emission detected toward NGC7538-IRS1N. The brightness distribution and spectrum of the line of bright masers are successfully modeled with high amplification of background radio continuum emission along velocity coherent paths through a maser disk. The bend seen in the position–velocity diagram is a characteristic signature of differentially rotating disks. For a central mass of 30M, suggested by other observations, our model fixes the masing disk to have inner and outer radii of 270 and 750 AU.  相似文献   

Variations in the column-average dry-air mole fractions of CO2 in the vicinity of St. Petersburg     

A. V. Rakitin  A. V. Poberovskii  Yu. M. Timofeev  M. V. Makarova  T. J. Conway 《Izvestiya Atmospheric and Oceanic Physics》2013,49(3):271-275

The results obtained from ground-based spectroscopic measurements of column-average dry-air mole fractions of CO₂ in the atmosphere over the St. Petersburg region are given for the period April 2009–October 2011 (～900 measurement runs, 151 measurement days). These results show significant variations in the CO₂ mixing ratio in the atmosphere over the St. Petersburg region. The minimum value of this mixing ratio (373.1 ppm) was observed on April 27, 2011, and its maximum value (420.8 ppm) was observed on February 10, 2010. The typical seasonal behavior of the CO₂ mixing ratio with its summer minimum was observed in 2009. In July 2010 and 2011, the values of the CO₂ mixing ratio increased apparently due to high air temperatures. In 2010 an additional contribution to this increase in the CO₂ mixing ratio could have been made by strong natural fires.  相似文献   

Future cereal production in China: The interaction of climate change,water availability and socio-economic scenarios   总被引：4，自引：0，他引：4  

Xiong Wei  Conway Declan  Lin Erda  Xu Yinlong  Ju Hui  Jiang Jinhe  Holman Ian  Li Yan 《Global Environmental Change》2009,19(1):34-44

Food production in China is a fundamental component of the national economy and driver of agricultural policy. Sustaining and increasing output to meet growing demand faces significant challenges including climate change, increasing population, agricultural land loss and competing demands for water. Recent warming in China is projected to accelerate by climate models with associated changes in precipitation and frequency of extreme events. How changes in cereal production and water availability due to climate change will interact with other socio-economic pressures is poorly understood. By linking crop and water simulation models and two scenarios of climate (derived from the Regional Climate Model PRECIS) and socio-economic change (downscaled from IPCC SRES A2 and B2) we demonstrate that by the 2040s the absolute effects of climate change are relatively modest. The interactive effects of other drivers are negative, leading to decreases in total production of ?18% (A2) and ?9% (B2). Outcomes are highly dependent on climate scenario, socio-economic development pathway and the effects of CO₂ fertilization on crop yields which may almost totally offset the decreases in production. We find that water availability plays a significant limiting role on future cereal production, due to the combined effects of higher crop water requirements (due to climate change) and increasing demand for non-agricultural use of water (due to socio-economic development). Without adaptation, per capita cereal production falls in all cases, by up to 40% of the current baseline.By simulating the effects of three adaptation scenarios we show that for these future scenarios China is able to maintain per capita cereal production, given reasonable assumptions about policies on land and water management and progress in agricultural technology. Our results are optimistic because PRECIS simulates much wetter conditions than a multi-model average, the CO₂ crop yield response function is highly uncertain and the effects of extreme events on crop growth and water availability are likely to be underestimated.  相似文献   

Progress in global environmental change     

W. Neil Adger  Katrina Brown  Declan Conway 《Global Environmental Change》2010,20(4):547-549

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Debris-flow release processes investigated through the analysis of multi-temporal LiDAR datasets in north-western Iceland     

Costanza Morino  Susan J. Conway  Matthew R. Balme  John Hillier  Colm Jordan  Þorsteinn Sæmundsson  Tom Argles 《地球表面变化过程与地形》2019,44(1):144-159

Debris flows are fast-moving gravity flows of poorly sorted rock and soil, mixed and saturated with water. Debris-flow initiation has been studied using empirical and experimental modelling, but the geomorphic changes, indicative of different triggering processes, are difficult to constrain with field observations only. We identify signatures to distinguish two different debris-flow release styles by integrating high-resolution multi-temporal remote sensing datasets and morphometric analysis. We analyse debris flows sourced above the town of Ísafjörður (Iceland). Two debris-flow triggering processes were previously hypothesised for this site: (i) slope failure, characterised by landslides evolving into debris flows; and (ii) the fire-hose effect, in which debris accumulated in pre-existing, steep-sided bedrock passages is transported by a surge of water. It is unknown which process dominates and determines the local risk. To investigate this question, we compare airborne LiDAR elevation models and aerial photographs collected in 2007 with similar data from 2013. We find that two new debris-flow tracks were created by slope failures. These are characterised by steep sliding surfaces and lateral leveed channels. Slope failure also occurred in two large, recently active tracks, creating the preparatory conditions for the fire-hose effect to mobilise existing debris. These tracks show alternating zones of fill and scour along their length, and debris stored below the source-area at rest angles >35°. Our approach allows us to identify and quantify the morphological changes produced by slope failure release process, which generated the preparatory conditions for the fire-hose effect. As debris flows are rarely observed in action and morphological changes induced by them are difficult to detect and monitor, the same approach could be applied to other landscapes to understand debris-flow initiation in the absence of other monitoring information, and can improve the identification of zones at risk in inhabited areas near hillslopes with potential for debris flows. © 2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

Assessment of institutional capacity to adapt to climate change in transboundary river basins     

Anita Milman  Lisa Bunclark  Declan Conway  William Neil Adger 《Climatic change》2013,121(4):755-770

Responses to climate change in transboundary river basins are believed to depend on national and sub-national capacities as well as the ability of co-riparian nations to communicate, coordinate, and cooperate across their international boundaries. We develop the first framework for assessing transboundary adaptive capacity. The framework considers six dimensions of transboundary river basins that influence planning and implementation of adaptation measures and represents those dimensions using twelve measurable indicators. These indicators are used to assess transboundary adaptive capacity of 42 basins in the Middle East, Mediterranean, and Sahel. We then conduct a cluster analysis of those basins to delineate a typology that includes six categories of basins: High Capacity, Mediated Cooperation, Good Neighbour, Dependent Instability, Self-Sufficient, and Low Capacity. We find large variation in adaptive capacity across the study area; basins in Western Europe generally have higher capacities to address the potential hazards of climate change. Our basin typology points to how climate change adaptation policy interventions would be best targeted across the different categories of basins.  相似文献   

Large-scale sedimentary bedforms and sediment dynamics on a glaciated tectonic continental shelf: Examples from the Pacific margin of Canada     

J. Vaughn Barrie  Kim W. Conway  Kim Picard  H. Gary Greene 《Continental Shelf Research》2009,29(5-6):796-806

The Pacific margin of Canada has been subjected to tectonism, dramatic sea level change and vigorous storm and tidal energy since glacial times resulting in a complex seafloor. Extensive multibeam mapping of this shelf has provided an opportunity to understand how these processes have impacted sedimentology and morphology. Bathymetric restriction of the tidally dominated flow between the inland seas and the open Pacific has resulted in the development of very large subaqueous dune fields and terrace moats. For example, in the southern Strait of Georgia nearly symmetrical dunes with wavelengths between 100 and 300 m, dune heights up to 28 m, cover the seafloor in 170–210 m water depth. In northern Hecate Strait a 72 km² area of large 2D dunes occurs at the transition with Dixon Entrance which opens to the Pacific Ocean and steep (>10°) wave-cut terraces and drowned spits, a result of sea level changes during the Holocene, are now being undercut to generate moats 7 m deep, in a narrowing shelf trough. Currents, with velocities ranging between 0.2 and 2.2 m s^?1, are dominated by semi-diurnal tidal streams that are continually modified by wind and estuarine circulation. There appears to be a clear association of grain size, water depth and flow velocity controlling the size of the subaqueous dunes.  相似文献   

The 2dF Galaxy Redshift Survey: stochastic relative biasing between galaxy populations     

Vivienne Wild  John A. Peacock  Ofer Lahav  Edward Conway  Steve Maddox  Ivan K. Baldry  Carlton M. Baugh  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Shaun Cole  Matthew Colless  Chris Collins  Warrick Couch  Gavin Dalton  Roberto De Propris  Simon P. Driver  George Efstathiou  Richard S. Ellis  Carlos S. Frenk  Karl Glazebrook  Carole Jackson  Ian Lewis  Stuart Lumsden  Darren Madgwick  Peder Norberg  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2005,356(1):247-269

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A possible mechanism governing the production and evolution of Ellerman bombs     

Declan A. Diver  John C. Brown  David M. Rust 《Solar physics》1996,168(1):105-114

A hydrodynamic-magnetofluid hybrid analysis of lower chromospheric shear flows in the Sun may explain the occurrence and time development of Ellerman bombs. The analysis assumes that the erupting material forming the bomb is driven initially by the Kelvin-Helmholtz fluid instability applied to the interface between two atmospheric fluid layers, characterized by a steep density change across the boundary and driven by flow fields around sunspots. The ensuing instability eventually evolves into a magnetofluid phenomenon by virtue of the trapping and bending of the interfacial magnetic field, giving rise to a dense globule of material entering, and persisting in, the upper layers and due to Ohmic dissipation having a significantly enhanced temperature compared with ambient material.  相似文献