Earth system models of intermediate complexity: closing the gap in the spectrum of climate system models   总被引：10，自引：7，他引：10  

M. Claussen  L. Mysak  A. Weaver  M. Crucifix  T. Fichefet  M.-F. Loutre  S. Weber  J. Alcamo  V. Alexeev  A. Berger  R. Calov  A. Ganopolski  H. Goosse  G. Lohmann  F. Lunkeit  I. Mokhov  V. Petoukhov  P. Stone  Z. Wang 《Climate Dynamics》2002,18(7):579-586

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The Suburbanization of Food Insecurity: An Analysis of Projected Trends in the Atlanta Metropolitan Area     

Jerry Shannon  Mathew E. Hauer  Alexis Weaver  Sarah Shannon 《The Professional geographer》2018,70(1):84-93

Although general patterns of food insecurity in the United States are known, few studies have attempted to estimate small area food security or account for ongoing socioeconomic changes. Here we address these issues by producing small area estimates of food insecurity in the Atlanta metropolitan area using two methodologies: fixed effects modeling and demographic metabolism. In both cases, we use county-level data from the Current Population Survey to determine the association between food insecurity and demographic predictors. These associations are then applied to tract-level data from the 2009 to 2013 American Community Survey and projected data for 2020 to create small area estimates of food insecurity. We find broad consensus between our two methods. For both time periods, food insecurity is highest in southern sections of the city of Atlanta and its neighboring suburbs. Projections to 2020, however, show that food insecurity rates are projected to increase in outer-ring suburbs east and west of the city while decreasing in the urban core. These results highlight the need to further adapt antihunger efforts for often sprawling suburban communities, where poverty rates are increasing but spatial mismatch combined with poor transit access might hinder access to food assistance.  相似文献   

Magnitude and variation in the contribution of bank erosion to the suspended sediment load of the River Severn,UK     

Louise J. Bull 《地球表面变化过程与地形》1997,22(12):1109-1123

The wide range of studies describing the role of bank erosion in fluvial sediment supply have mostly lumped amounts of bank erosion into coarse temporal units, such as years. This paper investigates sediment yields from individual bank erosion events within the upper River Severn, UK (basin area 380 km²). Manual erosion pins and photo-electronic erosion pins were used to estimate bank erosion, and turbidity meters were used to determine suspended sediment transport. At the annual time-scale, the silt-clay fraction of bank-derived sediment accounted for an equivalent of 17 per cent of the suspended load, increasing to an average of 38 per cent at the monthly timescale, and then to an average of 64 per cent at the event timescale. This research highlighted that for an upland catchment, bank erosion was an important supply of suspended sediment, and that for some flood events bank erosion can supply more sediment than is transported. © 1997 John Wiley & Sons, Ltd.  相似文献   

On the generation and decay of the long-period coda energy of large earthquakes          下载免费PDF全文

Xinyu Jiang  Xiaodong Song  Han H.Xia  Richard L.Weaver 《地震科学（英文版）》2021,34(2):103-113

Seismic coda wave is the tail portion of the earthquake record after main arrivals. Studies on the coda usually focus on high-frequency data within several hours after regional events and attribute them to the scattering effect of the heterogeneities inside the earth. Here, we use records of seven large earthquakes at globally distributed seismic stations to examine the decay of long-period (100 s to 300 s) coda in the time window of 10,000 s to 140,000 s after the origin time and fit it with a statistical model. The geometric spreading effect in the estimated initial energy and a location-independent equivalent attenuation coefficient indicate that the long-period coda energy is less affected by the heterogeneity-induced scattering effect than that of shorter-period coda. The coda energy can reach the earth's inner core and can be explained by a 1D earth model, making it more effective for constraining the global attenuation model. It also has the potential to determine the magnitudes of large earthquakes and to explore the interior of planetary bodies.  相似文献   

The daily‐scale entrance dynamics of intermittently open/closed estuaries          下载免费PDF全文

Sarah Louise McSweeney  David M. Kennedy  Ian D. Rutherfurd 《地球表面变化过程与地形》2018,43(4):791-807

Intermittently open/closed estuaries (IOCE) are a dynamic form of estuary characterised by periodic entrance closure to the ocean. Entrance closure is a function of the relative balance between on and offshore sediment transport with closures occurring during periods of low fluvial discharge whereby the estuary ebb‐tidal prism is reduced. Although the broad scale processes of entrance closure are becoming better understood, there remains limited knowledge on channel morphodynamics during an individual closure event. In this study, the entrance dynamics of three IOCE on the coast of Victoria, Australia, were monitored over a daily timescale following both artificial and natural openings. The influence of changing marine and fluvial conditions on the relative sedimentation rate within the entrance channel was examined. IOCE in Victoria showed two distinct modes of entrance closure: (a) lateral accretion, whereby the estuary gradually closes by longshore drift‐driven spit growth during low river flows; and (b) vertical accretion, where the channel rapidly aggrades under high (> 2 m), near‐normal waves. During storms, when fluvial discharge and wave heights simultaneously increase, large swells will not always close the mouth due to an increase in the ebb‐tidal prism. The estuary water depth and the maximum channel dimensions following opening were not proportional to the opening duration, with this being a function of the wave and fluvial conditions occurring following lagoon drainage. Based on the findings of this work, implementing a successful artificial entrance opening is dependent on reduced onshore sedimentation rates which occur when wave energy is low (< 2 m Hs) relative to river flow. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

The deglaciation of the western sector of the Irish Ice Sheet from the inner continental shelf to its terrestrial margin     

David H. Roberts  Colm Ó Cofaigh  Colin K. Ballantyne  Matthew Burke  Richard C. Chiverrell  David J. A. Evans  Chris D. Clark  Geoff A. T. Duller  Jeremy Ely  Derek Fabel  David Small  Rachel K. Smedley  S. Louise Callard 《Boreas: An International Journal of Quaternary Research》2020,49(3):438-460

This paper provides a new deglacial chronology for retreat of the Irish Ice Sheet from the continental shelf of western Ireland to the adjoining coastline, a region where the timing and drivers of ice recession have never been fully constrained. Previous work suggests maximum ice-sheet extent on the outer western continental shelf occurred at ~26–24 cal. ka BP with the initial retreat of the ice marked by the production of grounding-zone wedges between 23–21.1 cal. ka BP. However, the timing and rate of ice-sheet retreat from the inner continental shelf to the present coast are largely unknown. This paper reports 31 new terrestrial cosmogenic nuclide (TCN) ages from erratics and ice-moulded bedrock and three new optically stimulated luminescence (OSL) ages on deglacial outwash. The TCN data constrain deglaciation of the near coast (Aran Islands) to ~19.5–18.5 ka. This infers ice retreated rapidly from the mid-shelf after 21 ka, but the combined effects of bathymetric shallowing and pinning acted to stabilize the ice at the Aran Islands. However, marginal stability was short-lived, with multiple coastal sites along the Connemara/Galway coasts demonstrating ice recession under terrestrial conditions by 18.2–17. ka. This pattern of retreat continued as ice retreated eastward through inner Galway Bay by 16.5 ka. South of Galway, the Kilkee–Kilrush Moraine Complex and Scattery Island moraines point to late stage re-advances of the ice sheet into southern County Clare ~14.1–13.3 ka, but the large errors associated with the OSL ages make correlation with other regional re-advances difficult. It seems more likely that these moraines are the product of regional ice lobes adjusting to internal ice-sheet dynamics during deglaciation in the time window 17–16 ka.  相似文献   

Soil water movement and nutrient cycling in semi-arid rangeland: vegetation change and system resilience     

Andy J. Dougill  A. Louise Heathwaite  David S. G. Thomas 《水文研究》1998,12(3):443-459

Recent decades have seen rapid intensification of cattle production in semi-arid savannah ecosystems, increasingly on formalized ranch blocks. As a result, vegetation community changes have occurred, notably bush encroachment (increased bush dominance) in intensively grazed areas. The exact causes of this vegetation change remain widely debated. Previous studies have suggested: (i) increased leaching of water and nutrients into the subsoil in intensively grazed areas provides deeper rooting bush species with a competitive advantage for soil water and nutrients, and (ii) nutrient leaching may be exacerbated by nutrient inputs from cattle dung and urine. Our research in the Eastern Kalahari showed that in infertile sandy soils both the magnitude of soil water and concentration of soil nutrients leached into the subsoil is largely unaffected by the ecological and biochemical effects of increased cattle use. We found that despite the high soil hydraulic conductivity ( &greaterno;12 cm h⁻¹), relatively high subsoil moisture contents and the restriction of water movement to matrix flow pathways prevent leaching losses beyond the rooting zone of savannah grass species. No significant differences in patterns of soil water redistribution were noted between bush dominant and grass dominant sites. We also found that the low nutrient status of Kalahari soils and leachate movement as matrix flow combine to allow nutrient adsorption on to soil particles. Nutrient adsorption ensures that nitrogen and phosphorus cycling remains topsoil dominated even following the removal of vegetation and direct nutrient inputs in cattle dung and urine. This conclusion refutes environmental change models that portray increases in the leaching of soil water and available nitrogen as a major factor causing bush encroachment. This provides a possible explanation for the now widely cited, but hitherto unexplained, resilience of dryland soils. We suggest that infertile sandy soils appear resilient to changes in soil water distribution and nutrient availability caused by increased cattle use. Hence, soil characteristics contribute to the resilience to permanent ecological change that is increasingly recognized as an attribute of semi-arid rangelands. © 1998 John Wiley & Sons, Ltd.  相似文献   

Simulation of the 2004 tsunami of Les Saintes in Guadeloupe (Lesser Antilles) using new source constraints     

Cordrie  Louise  Gailler  Audrey  Escartin  Javier  Feuillet  Nathalie  Heinrich  Philippe 《Natural Hazards》2020,103(2):2103-2129

Natural Hazards - The arc of the Lesser Antilles is associated with a significant tectonic activity due to the subduction of the Atlantic oceanic plate under the Caribbean plate. Earthquakes in...  相似文献   

Stochastic Radiative Transfer on Modeled Cloud Fields     

Veron  D.E. Weaver  C.P. Veron  F. Foster  M.J. 《Geoscience and Remote Sensing Letters, IEEE》2009,6(2):184-188

Several efforts are currently underway to improve cloud-radiation parameterizations in Global Climate Models (GCMs) by incorporating statistical properties of the cloud field. Although some radiation parameterizations, which are already computationally costly, now incorporate subgrid scale variability in cloud properties, they are not yet capable of using this information in their calculations of the 3-D radiation fields. Before drastic changes are made to such algorithms to incorporate cloud-cloud radiation interactions, the impact of including realistic high-resolution cloud distributions on the shortwave fluxes should be assessed. This letter provides a framework for carrying out such assessments, including a new methodology that blends a stochastic radiative transfer model, high-resolution cloud fields from a mesoscale meteorological model, and a threshold and object identification technique applied to cloud water content fields. This process provides a link between the radiative fluxes calculated in GCMs, where clouds occur at a subgrid scale, and the highly resolved cloud fields in a regional climate model, which can provide cloud field statistics. Two case studies are described herein.  相似文献   

Borehole temperatures, climate change and the pre-observational surface air temperature mean: allowance for hydraulic conditions   总被引：1，自引：0，他引：1  

Louise Bodri  Vladimir Cermak 《Global and Planetary Change》2005,45(4):265-276

Joint analysis of surface air temperature series recorded at weather stations together with the inversion of the temperature-depth profiles logged in the near-by boreholes enables an estimate of the conditions existing prior to the beginning of the meteorological observation, the so-called pre-observational mean (POM) temperature.Such analysis is based on the presumption of pure diffusive conditions in the underground. However, in real cases a certain subsurface fluid movement cannot be excluded and the measured temperature logs may contain an advective component. The paper addresses the correction for the hydraulic conditions, which may have perturbed the climate signal penetrating from the surface into the underground. The method accounts for vertical conductive and vertical advective heat transport in a 1-D horizontally layered stratum and provides a simultaneous evaluation of the POM-temperature together with the estimate of the Darcy fluid velocity. The correction strategy is illustrated on a synthetic example and its use is demonstrated on temperature logs measured in four closely spaced boreholes drilled near Tachlovice (located about 15 km SW of Prague, Czech Republic). The results revealed that in a case of moderately advectively affected subsurface conditions (fluid velocities about 10⁻⁹ m/s), the difference between POM-values assessed for a pure conductive approach and for combined vertical conductive/advective approach may amount up to 0.3–0.5 K, the value comparable with the amount usually ascribed to the 20th century climate warming.  相似文献