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961.
Bias correction methods remove systematic differences in the distributional properties of climate model outputs with respect to observations, often as a means of pre-processing model outputs for use in hydrological impact studies. Traditionally, bias correction is applied at each weather station individually, neglecting the dependence that exists between different sites, which could negatively affect simulations from a distributed hydrological model. In this study, three multi-variate bias correction (MBC) methods—initially proposed to correct the inter-variable correlation or multi-variate dependence of climate model outputs—are used to correct biases in distributional properties and spatial dependence at multiple weather stations. To reveal the benefits of correcting spatial dependence, two distribution-based single-site bias correction methods are used for comparison. The effects of multi-site correction on hydro-meteorological extremes are assessed by driving a distributed hydrological model and then evaluating the model performance in terms of several meteorological and hydrological extreme indices. The results show that the multi-site bias correction methods perform well in reducing biases in spatial correlation measures of raw global climate model outputs. In addition, the multi-site methods consistently reproduce watershed-averaged meteorological variables better than single-site methods, especially for extreme values. In terms of representing hydrological extremes, the multi-site methods generally perform better than the single-site methods, although the benefits vary according to the hydrological index. However, when applying the multi-site methods, the original temporal sequence of precipitation occurrence may be altered to some extent. Overall, all multi-site bias correction methods are able to reproduce the spatial correlation of observed meteorological variables over multiple stations, which leads to better hydrological simulations, especially for extremes. This study emphasizes the necessity of considering spatial dependence when applying bias correction to ccc outputs and hydrological impact studies. 相似文献
962.
963.
Michael A. Dopita Daniela Calzetti Jesús Maíz Apellániz William P. Blair Knox S. Long Max Mutchler Bradley C. Whitmore Howard E. Bond John MacKenty Bruce Balick Marcella Carollo Michael Disney Jay A. Frogel Robert O’Connell Donald Hall Jon A. Holtzman Randy A. Kimble Patrick McCarthy Francesco Paresce Abhijit Saha Alistair R. Walker Joe Silk Marco Sirianni John Trauger Rogier Windhorst Erick Young 《Astrophysics and Space Science》2010,330(1):123-131
We present narrow band, continuum subtracted Hα, [S ii], Hβ, [O iii] and [O ii] data taken with the Wide Field Camera 3 on the Hubble Space Telescope in the nearby dwarf starburst galaxy NGC 4214. From these images, we identify seventeen new planetary nebula candidates, and seven supernova remnant candidates. We use the observed emission line luminosity function of the planetary nebulae to establish a new velocity-independent distance to NGC 4214. We conclude that the PNLF technique gives a reddening independent distance to NGC 4214 of 3.19±0.36 Mpc, and that our current best-estimate of the distance to this galaxy ids 2.98±0.13 Mpc. 相似文献
964.
F. Suzuki-Vidal S. V. Lebedev A. Ciardi S. N. Bland J. P. Chittenden G. N. Hall A. Harvey-Thompson A. Marocchino C. Ning C. Stehle A. Frank E. G. Blackman S. C. Bott T. Ray 《Astrophysics and Space Science》2009,322(1-4):19-23
We report on experiments in which magnetically driven radiatively cooled plasma jets were produced by a 1 MA, 250 ns current pulse on the MAGPIE pulsed power facility. The jets were driven by the pressure of a toroidal magnetic field in a “magnetic tower” jet configuration. This scenario is characterized by the formation of a magnetically collimated plasma jet on the axis of a magnetic “bubble”, confined by the ambient medium. The use of a radial metallic foil instead of the radial wire arrays employed in our previous work allows for the generation of episodic magnetic tower outflows which emerge periodically on timescales of ~30 ns. The subsequent magnetic bubbles propagate with velocities reaching ~300 km/s and interact with previous eruptions leading to the formation of shocks. 相似文献
965.
B. Van Vliet-Lanoe C. Hibsch L. Csontos S. Jegouzo B. Hallégouët M. Laurent A. Maygari D. Mercier P. Voinchet 《International Journal of Earth Sciences》2009,98(5):969-984
The Pénestin section (southern Brittany) presents large regular undulations, commonly interpreted as evidence of periglacial
pingos. It is an upper Neogene palaeoestuary of the Vilaine River reactivated during the middle Quaternary (middle terrace).
It is incised into a thick kaolinitic saprolite and deformed by saprolite diapirs. This paper presents the arguments leading
to a mechanistic interpretation of the deformations at Pénestin. Neither recent transpressive tectonics nor diagnostic evidence
of periglacial pingo have been found despite evidence for a late paleo-permafrost. The major deformational process is shale
diapirism, initially triggered by co-seismic water supply, with further loading and lateral spreading on an already deformed
and deeply weathered basement, which allowed the shale diapirism to develop. Deformations are favoured by the liquefaction
of the saprolite and a seaward mass movement and recorded, rather distant, effects of an earthquake (c. 280 ka B.P.) resulting
from the progressive subsidence of the southern Armorican margin. These deformations triggered by an earthquake are similar
to those induced by classical shale diapirism. They are probably common in tectonically active continental environments with
shallow water table. 相似文献
966.
Ying Wang Alex L. Sessions Robert J. Nielsen William A. Goddard III 《Geochimica et cosmochimica acta》2009,73(23):7076-7086
Equilibrium 2H/1H fractionation factors (αeq) for various H positions in alkanes, alkenes, ketones, carboxylic acids, esters, alcohols, and ethers were calculated between 0 and 100 °C using vibrational frequencies from ab initio QM calculations (B3LYP/6-311G**). Results were then corrected using a temperature-dependent linear calibration curve based on experimental data for Hα in ketones (Wang et al., 2009). The total uncertainty in reported αeq values is estimated at 10–20‰. The effects of functional groups were found to increase the value of αeq for H next to electron-donating groups, e.g. OR, OH or O(CO)R, and to decrease the value of αeq for H next to electron-withdrawing groups, e.g. (CO)R or (CO)OR. Smaller but significant functional group effects are also observed for Hβ and sometimes Hγ. By summing over individual H positions, we estimate the equilibrium fractionation relative to water to be −90‰ to −70‰ for n-alkanes and around −100‰ for pristane and phytane. The temperature dependence of these fractionations is very weak between 0 and 100 °C. Our estimates of αeq agree well with field data for thermally mature hydrocarbons (δ2H values between −80‰ and −110‰ relative to water). Therefore the observed δ2H increase of individual hydrocarbons and the disappearance of the biosynthetic δ2H offset between n-alkyl and linear isoprenoid lipids during maturation of organic matter can be confidently attributed to H exchange towards an equilibrium state. Our results also indicate that many n-alkyl lipids are biosynthesized with δ2H values that are close to equilibrium with water. In these cases, constant down-core δ2H values for n-alkyl lipids cannot be reliably used to infer a lack of isotopic exchange. 相似文献
967.
This paper introduces the special issue ‘organisational geographies of power’ by examining the theoretical and empirical context for debates. It does this, firstly, with reference to existing theoretical work on what power is and does as well as work on the construction of power relations. Building on this, the paper then, secondly, examines the way relational and production network approaches have incorporated power into work on transnational corporations before, thirdly, considering how work on neoliberalism has studied the construction of spatial power relations. In doing this the paper highlights four important questions for future research relating to the practices and spatiality of power, the exercising of power and the situated effects of power relations. 相似文献
968.
Humberto Marotta Luiz Bento Francisco de A. Esteves Alex Enrich-Prast 《Estuaries and Coasts》2009,32(4):654-660
The purpose of this research was to assess the effects of dredging performed in a marginal wetland colonized by aquatic macrophytes
on eutrophication of the adjacent shallow tropical lake (Imboassica Lake, Brazil). The river mouth of the Imboassica River
that drains into Imboassica Lake had been densely colonized by aquatic vegetation dominated by Typha domingensis (Pers.) when it was dredged. Total and dissolved nitrogen and phosphorus concentrations were measured monthly over 13 years
at four stations in the Imboassica river-lake system. Dredging activities reduced phosphorus and nitrogen retention at the
river mouth and subsequently increased these nutrient stocks in the lake waters. Nutrient retention by non-dredged wetland
was estimated to be ca. 1,200 kg year−1 (87.3 g m−2 year−1) for nitrogen and 60 kg year−1 (4.5 g m−2 year−1) for phosphorus. Our whole-lake approach suggested that dredging might intensify rather than mitigate eutrophication in shallow
tropical lakes when the removal of aquatic macrophytes is coupled to the persistence of anthropogenic nutrient inputs from
the watershed. 相似文献
969.
Charles French Richard Periman Linda Scott Cummings Stephen Hall Melissa Goodman‐Elgar Julie Boreham 《Geoarchaeology》2009,24(5):638-676
We describe a geoarchaeological survey of a 5‐km reach of the Rio Puerco channel and its tributaries, centered on the Guadalupe Ruin, a pueblo of the late 10th–12th centuries A.D. in north‐central New Mexico, with associated pollen, charcoal, micromorphological, and radiocarbon analyses. Severe erosion has drastically bisected the Puerco valley with four primary arroyos entering the western side of the Guadalupe reach of the valley: Tapia, Salado, Guadalupe and “No Name.” We recorded an 11‐m‐tall alluvial sequence marked by four phases of cumulic soil development, interrupted by six major periods of channel entrenchment that occurred at about 4100–3700 B.C. and 2900–2400 B.C., between 2200 B.C. and ca. A.D. 400, pre‐ and post‐ca. A.D. 900–1300, and in the late A.D. 1800s. Relative floodplain stability and associated cumulic soil development occurred prior to ca. 5700 B.C., between ca. 2600 to 2200 B.C. and A.D. 350 and 550, and ca. A.D. 900–1300. Multiple signatures of fires (oxidized sediment and charcoal) were observed in the Arroyo Tapia tributary sequence, especially in deposits dated ca. 6000 and 2600 B.C. These fires may have helped to enhance food resources for game animals by encouraging grass and shrub growth and/or to increase the growth of wild plants and eventually cultigens such as maize. Palynological evidence of maize in the Arroyo Tapia, dated ca. 2600–2200 B.C. may be the earliest thus far identified in the Southwest. © 2009 Wiley Periodicals, Inc. 相似文献
970.
利用ENVISAT/ASAR和ALOS/PALSAR数据,结合两路差分干涉测量技术获得了汶川地震的同震形变信息和震前、震后地面在卫星视线(light of sight,简称LOS)方向上的形变特征。结果表明,汶川地震引起的地面形变范围广,程度大,地震形变沿断层向北北东向扩展,所形成的差分干涉条纹明显。地面的形变特征对于推断断层的性质,研究地震形变和地震发育特征具有重要的参考价值。另外,将同震雷达差分干涉测量的结果与利用USGS发布的汶川地震有限元断层模型(finite fault model)反演的LOS方向的形变进行了对比验证,发现二者在断裂带的上盘具有较好的一致性,但在下盘却有较大的误差。通过不同传感器干涉结果的对比发现,L波段的雷达干涉结果更能够反映汶川大地震在龙门山断裂带附近的地面形变信息。 相似文献