A New Sensitivity Analysis and Solution Method for Scintillometer Measurements of Area-Averaged Turbulent Fluxes   总被引：1，自引：1，他引：0  

Matthew Gruber  Gilberto J. Fochesatto 《Boundary-Layer Meteorology》2013,149(1):65-83

Scintillometer measurements of the turbulence inner-scale length $l_\mathrm{o }$ l o and refractive index structure function $C_n^2$ C n 2 allow for the retrieval of large-scale area-averaged turbulent fluxes in the atmospheric surface layer. This retrieval involves the solution of the non-linear set of equations defined by the Monin–Obukhov similarity hypothesis. A new method that uses an analytic solution to the set of equations is presented, which leads to a stable and efficient numerical method of computation that has the potential of eliminating computational error. Mathematical expressions are derived that map out the sensitivity of the turbulent flux measurements to uncertainties in source measurements such as $l_\mathrm{o }$ l o . These sensitivity functions differ from results in the previous literature; the reasons for the differences are explored.  相似文献   

Assessing vulnerability due to sea-level rise in Maui, Hawai‘i using LiDAR remote sensing and GIS     

Hannah M. Cooper  Qi Chen  Charles H. Fletcher  Matthew M. Barbee 《Climatic change》2013,116(3-4):547-563

Sea-level rise (SLR) threatens islands and coastal communities due to vulnerable infrastructure and populations concentrated in low-lying areas. LiDAR (Light Detection and Ranging) data were used to produce high-resolution DEMs (Digital Elevation Model) for Kahului and Lahaina, Maui, to assess the potential impacts of future SLR. Two existing LiDAR datasets from USACE (U.S. Army Corps of Engineers) and NOAA (National Oceanic and Atmospheric Administration) were compared and calibrated using the Kahului Harbor tide station. Using tidal benchmarks is a valuable approach for referencing LiDAR in areas lacking an established vertical datum, such as in Hawai‘i and other Pacific Islands. Exploratory analysis of the USACE LiDAR ground returns (point data classified as ground after the removal of vegetation and buildings) indicated that another round of filtering could reduce commission errors. Two SLR scenarios of 0.75 (best-case) to 1.9 m (worst-case) (Vermeer and Rahmstorf Proc Natl Acad Sci 106:21527–21532, 2009) were considered, and the DEMs were used to identify areas vulnerable to flooding. Our results indicate that if no adaptive strategies are taken, a loss ranging from $18.7 million under the best-case SLR scenario to $296 million under the worst-case SLR scenario for Hydrologically Connected (HC; marine inundation) and Hydrologically Disconnected (HD; drainage problems due to a higher water table) areas combined is possible for Kahului; a loss ranging from $57.5 million under the best-case SLR scenario to $394 million under the worst-case SLR scenario for HC and HD areas combined is possible for Lahaina towards the end of the century. This loss would be attributable to inundation between 0.55 km² to 2.13 km² of area for Kahului, and 0.04 km² to 0.37 km² of area for Lahaina.  相似文献   

Studying geoengineering with natural and anthropogenic analogs     

Alan Robock  Douglas G. MacMartin  Riley Duren  Matthew W. Christensen 《Climatic change》2013,121(3):445-458

Solar radiation management (SRM) has been proposed as a possible option for offsetting some anthropogenic radiative forcing, with the goal of reducing some of the associated climatic changes. There are clearly significant uncertainties associated with SRM, and even small-scale experiments that might reduce uncertainty would carry some risk. However, there are also natural and anthropogenic analogs to SRM, such as volcanic eruptions in the case of stratospheric aerosol injection and ship tracks in the case of marine cloud albedo modification. It is essential to understand what we can learn from these analogs in order to validate models, particularly because of the problematic nature of outdoor experiments. It is also important to understand what we cannot learn, as this might better focus attention on what risks would need to be solely examined by numerical models. Stratospheric conditions following a major volcanic eruption, for example, are not the same as those to be expected from intentional geoengineering, both because of confounding effects of volcanic ash and the differences between continuous and impulsive injection of material into the stratosphere. Nonetheless, better data would help validate models; we thus recommend an appropriate plan be developed to better monitor the next large volcanic eruption. Similarly, more could be learned about cloud albedo modification from careful study not only of ship tracks, but of ship and other aerosol emission sources in cloud regimes beyond the narrow conditions under which ship tracks form; this would benefit from improved satellite observing capabilities.  相似文献   

Globalization,Pacific Islands,and the paradox of resilience   总被引：1，自引：0，他引：1  

Matthew Lauer  Simon Albert  Shankar Aswani  Benjamin S. Halpern  Luke Campanella  Douglas La Rose 《Global Environmental Change》2013,23(1):40-50

On April 2nd, 2007 a 12 m tsunami struck Simbo, a relatively remote island in Western Province, Solomon Islands. Although Simbo's population continues to depend on their own food production and small-scale governance regimes regulate access to resources, the island's way of life over the last century has increasingly been affected by processes associated with globalization. In this context of a rapidly globalizing world, this article examines the island's resilience and vulnerability to the tsunami and the adaptive capacities that enabled the response and recovery. The tsunami completely destroyed two villages and damaged fringing coral reefs, but casualties were low and social–ecological rebound relatively brisk. By combining social science methods (household surveys, focus group and ethnographic interviews) and underwater reef surveys we identify a number of countervailing challenges and opportunities presented by globalization that both nurture and suppress the island's resilience to high amplitude, low-frequency disturbances like tsunamis. Analysis suggests that certain adaptive capacities that sustain general system resilience come at the cost of more vulnerability to low-probability hazards. We discuss how communities undergoing increasingly complex processes of change must negotiate these kinds of trade-offs as they manage resilience at multiple spatial and temporal scales. Understanding the shifting dynamics of resilience may be critical for Pacific Island communities who seek to leverage globalization in their favor as they adapt to current social–ecological change and prepare for future large-scale ecological disturbances.  相似文献   

Does the framing of climate policies make a difference to public support? Evidence from UK marginal constituencies     

Matthew Lockwood 《Climate Policy》2013,13(4):1097-1112

Public support for climate policies is essential to underpin their credibility, but evidence suggests that an environmental basis for that support is not strong. It has been suggested that framing climate policies in other terms, such as energy security or job creation, will build a more sustainable political basis for bold climate policies. This approach is explored using data from a survey in 157 UK marginal constituencies. Framing does make a difference to support for the expansion of renewable energy, but not to support for policies on energy efficiency and financial assistance to developing countries. The data also show key differences in levels of support for policies between different socio-demographic and voter groups.  相似文献   

Eridanus – a supergroup in the local Universe?     

Sarah Brough  Duncan A. Forbes  Virginia A. Kilborn  Warrick Couch  Matthew Colless 《Monthly notices of the Royal Astronomical Society》2006,369(3):1351-1374

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Basait generation at the Apollo 12 site,Part 2: Source heterogeneity,multiple melts,and crustal contamination     

Clive R. Neal  Matthew D. Hacker  Gregory A. Snyder  Lawrence A. Taylor  Yun-Gang Liu  Roman A. Schmitt 《Meteoritics & planetary science》1994,29(3):349-361

Abstract— The petrogenesis of Apollo 12 mare basalts has been examined with emphasis on trace-element ratios and abundances. Vitrophyric basalts were used as parental compositions for the modelling, and proportions of fractionating phases were determined using the MAGFOX program of Longhi (1991). Crystal fractionation processes within crustal and sub-crustal magma chambers are evaluated as a function of pressure. Knowledge of the fractionating phases allows trace-element variations to be considered as either source related or as a product of post-magma-generation processes. For the ilmenite and olivine basalts, trace-element variations are inherited from the source, but the pigeonite basalt data have been interpreted with open-system evolution processes through crustal assimilation. Three groups of basalts have been examined: (1) Pigeonite basalts — produced by the assimilation of lunar crustal material by a parental melt (up to 3% assimilation and 10% crystal fractionation, with an “r” value of 0.3). (2) Ilmenite basalts — produced by variable degrees of partial melting (4–8%) of a source of olivine, pigeonite, augite, and plagioclase, brought together by overturn of the Lunar Magma Ocean (LMO) cumulate pile. After generation, which did not exhaust any of the minerals in the source, these melts experienced closed-system crystal fractionation/accumulation. (3) Olivine basalts — produced by variable degrees of partial melting (5–10%) of a source of olivine, pigeonite, and augite. After generation, again without exhausting any of the minerals in the source, these melts evolved through crystal accumulation. The evolved liquid counterparts of these cumulates have not been sampled. The source compositions for the ilmenite and olivine basalts were calculated by assuming that the vitrophyric compositions were primary and the magmas were produced by non-modal batch melting. Although the magnitude is unclear, evaluation of these source regions indicates that both be composed of early- and late-stage Lunar Magma Ocean (LMO) cumulates, requiring an overturn of the cumulate pile.  相似文献   

Black hole spin in GRS 1915+105   总被引：2，自引：0，他引：2  

Matthew Middleton  Chris Done  Marek Gierli&#;ski  Shane W. Davis 《Monthly notices of the Royal Astronomical Society》2006,373(3):1004-1012

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Spatially resolved spectroscopy of the E+A galaxies in the z= 0.32 cluster AC 114   总被引：1，自引：0，他引：1  

Michael B. Pracy  Warrick J. Couch  Chris Blake  Kenji Bekki  Craig Harrison  Matthew Colless  Harald Kuntschner  Roberto de Propris 《Monthly notices of the Royal Astronomical Society》2005,359(4):1421-1432

We present spatially resolved intermediate-resolution spectroscopy of a sample of 12 E+A galaxies in the   z = 0.32  rich galaxy cluster AC 114, obtained with the FLAMES multi-integral field unit system on the Very Large Telescope (VLT) of the European Southern Observatory. Previous integrated spectroscopy of all these galaxies by Couch & Sharples had shown them to have strong Balmer line absorption and an absence of [O  ii ]λ3727 emission – the defining characteristics of the 'E+A' spectral signature, indicative of an abrupt halt to a recent episode of quite vigorous star formation. We have used our spectral data to determine the radial variation in the strength of Hδ absorption in these galaxies and hence map out the distribution of this recently formed stellar population. Such information provides important clues as to what physical event might have been responsible for this quite dramatic change in star formation activity in the recent past of these galaxies. We find a diversity of behaviour amongst these galaxies in terms of the radial variation in Hδ absorption: four galaxies show little Hδ absorption across their entire extent; it would appear they were misidentified as E+A galaxies in the earlier integrated spectroscopic studies. The remainder show strong Hδ absorption, with a gradient that is either negative (Hδ equivalent width decreasing with radius), flat or positive . By comparison with numerical simulations we suggest that the first of these different types of radial behaviour provides evidence for a merger/interaction origin, whereas the latter two types of behaviour are more consistent with the truncation of star formation in normal disc galaxies with the Hδ gradient becoming increasingly positive with time after truncation. It would seem therefore that more than one physical mechanism is responsible for E+A formation in the same environment.  相似文献   

From Molecular Cores to Stars and Brown Dwarfs     

Matthew R. Bate 《Astrophysics and Space Science》2004,292(1-4):297-307

In this paper, we review the results from numerical simulations that investigate the evolution of molecular cores into stars and brown dwarfs. We begin by discussing the four main processes involved in this evolution, fragmentation, accretion, interactions with discs, and stellar dynamical interactions. We then discuss large-scale calculations in which all of these processes are model simultaneously. Finally, we review results that have been obtained from past magnetohydrodynamical (MHD) calculations of fragmentation and look towards future MHD calculations.  相似文献