Laboratory modeling of topographic Rossby normal modes     

Stefano Pierini  Adam M. Fincham  Dominique Renouard  Maria Rosaria D&#x;Ambrosio  Henry Didelle 《Dynamics of Atmospheres and Oceans》2002,35(3)

The physical modeling of topographic Rossby normal modes carried out at the “Coriolis” Rotating Platform (Grenoble), is presented. The basic feature of the bottom topography is a linear slope of 4.3 m×2 m delimited by two lateral walls. Since the studied motions are essentially barotropic, homogeneous water was used. Unsheared currents were generated by a simple movement of a wavemaker located in front of the topographic barrier. The conservation of potential vorticity for the currents flowing onto the channel slope produced Rossby waves: reflections at the lateral boundaries then led to the formation of propagating barotropic Rossby normal modes, whose frequencies and spatial structures were selected by the physical system. The currents were measured through the correlation imaging velocimetry (CIV) method, which allowed an extremely detailed synoptic map of the horizontal velocities in an area (13 m²) including the slope to be obtained every 30 s.A variety of experiments were performed in order to provide a complete process study in which the effect of different channel lengths and rotation periods could be tested. Two different lengths of the linear slope, 4.3 and 3.3 m, and rotation periods ranging from 30 to 50 s were considered. The qualitative analysis of the 2D current patterns, and the good agreement found between the measured eigenperiods and the periods obtained by means of a simple analytical model, show that in all cases the first Rossby normal mode was generated. Moreover, numerical simulations based on the shallow-water equations, for a geometry and paddle movements that match closely the experimental setup, allow to calibrate the analytical model and provide useful information on a discrepancy found between experimental and analytical eigenperiods due to an oscillation of the normal mode trajectory.  相似文献   

College students’ consumption, contribution, and risk awareness related to online mapping services and social media outlets: does geography and GIS knowledge matter?     

Adam J. Mathews  Yongmei Lu  Matthew T. Patton  Nathaniel Dede-Bamfo  Junfang Chen 《GeoJournal》2013,78(4):627-639

Location-enabled online tools and/or services (i.e. Google Earth/Maps, Flickr, Facebook check-ins, etc.) have been widely used for distributing and processing geospatial-related data. They attract diverse users to consume and contribute geographic information (GI) in many different forms. This study examines college students’ consumption and contribution of GI through these tools and/or services as well as their perception of risk and privacy. It evaluates the impact of Geographic information systems (GIS) and geography knowledge on the related behavior and perception. Through conducting a survey, it was found that college students’ consumption frequency of GI through the investigated tools and services is positively related to their knowledge in GIS and geography, but their GI contribution is not related. GIS knowledge was found to help raise students’ awareness level of risk. However, this relationship does not translate into students’ concern about potential privacy disclosure or their willingness to share personal location information through using location-enabled online tools and/or services. Discussions on the gap between students’ consumption and contribution of GI through the tools and/or services are shared in the paper as well as possible explanations on the disconnection between their risk awareness, privacy concern, and willingness to share personal information. Future research directions are discussed.  相似文献   

A Review of “Agrarian Angst and Rural Resistance in Contemporary Southeast Asia”     

Adam Lukasiewicz 《The Professional geographer》2013,65(4):546-548

This article addresses the issue of linking temporal and spatial information into a GIS database structure to investigate the land-use changes in a rural-urban region over a thirty-five-year period. More specifically, it describes the application of a programming package developed to build temporal topology in an historical land-use GIS database to efficiently perform spatiotemporal queries. The program was created within the MapInfo environment using MapBasic language. Different types of information, such as the rate of change, the relationship between the change of land use and zoning regulations, and land-use succession were extracted from the database. A user-friendly interface was also developed to easily address spatiotemporal queries to the database. This approach represents a flexible and performing tool for scientists and planners who need to efficiently capture essential spatiotemporal information required for geographical inquiry and decision-making.  相似文献   

Determining the susceptibility of Eucalyptus nitens forests to Coryphodema tristis (cossid moth) occurrence in Mpumalanga,South Africa     

Elhadi Adam  Onisimo Mutanga  Riyad Ismail 《International journal of geographical information science》2013,27(10):1924-1938

The cossid moth, Coryphodema tristis was first noted on Eucalyptus nitens trees in Mpumalanga province, South Africa during July 2004. Currently, the moth poses a major threat to commercial forestry in the country. In this study, selected climatic and topographical variables were used to model the susceptibility of E. nitens forests to cossid moth occurrence, thereby providing insight into the variables that may influence the occurrence and spread of the moth. A zigzag sampling technique was used to survey 5316 ha of E. nitens forests for the presence or absence of the moth. The random forest classification algorithm was then used to model the relationship between the climatic and topographical variables and the occurrence of the cossid moth. Results indicate that four variables that included elevation, maximum temperature for September, maximum temperature for April and the median rainfall for April best explained the presence or absence of C. tristis with an overall accuracy of 82% and a kappa value of 0.63. Partial dependence plots indicated that the areas that have a maximum temperature greater than 23°C in September and 22°C in April are likely to be infested by the cossid moth. The results from this study provide a robust and accurate spatial framework to assist forest managers in focussing their existing monitoring and control efforts to specific E. nitens forested areas that are highly susceptible to C. tristis infestations.  相似文献   

Decoherence time scales for “meteoroid streams”     

Adam PAULS  Brett GLADMAN 《Meteoritics & planetary science》2005,40(8):1241-1256

Abstract— We explore the orbital dynamics of Earth‐crossing objects with the intent to understand the time scales under which an “orbital stream” of material could produce time‐correlated meteorite falls. These “meteoroid streams” have been suggested to be associated with three well‐known meteorite‐dropping fireballs (Innisfree, Peekskill, and P?íbram). We have performed two different analyses of the statistical significance of the “orbital similarity,” in particular calculating how often orbits of the same level of similarity would come from a random sample. Secondly, we have performed extremely detailed numerical integrations related to these three cases, and we find that if they were streams of objects in similar orbits, then they would become “decoherent” (in the sense that the day‐of‐fall of meteorites of these streams become almost random) on time scales of 10⁴–10⁵ yr. Thus, an extremely recent breakup would be required, much more recent that the cosmic ray exposure ages of the recovered falls in each case. We conclude that orbital destruction is too efficient to allow the existence of long‐lived meteoroid streams and that the statistical evidence for such streams is insufficient; random fall patterns show comparable levels of clustering.  相似文献   

Power spectrum normalization and the non-Gaussian halo model     

Adam Amara  Alexandre Refregier 《Monthly notices of the Royal Astronomical Society》2004,351(1):375-383

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The impact of The IGM on high-redshift Lyα emission lines     

Mark Dijkstra  Adam Lidz  J. Stuart B. Wyithe 《Monthly notices of the Royal Astronomical Society》2007,377(3):1175-1186

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Galaxies at the detection limits of deep X-ray surveys     

Richard Griffiths  Takamitsu Miyaji  Adam Knudson 《Astrophysics and Space Science》2003,284(2):961-964

The great sensitivities of the Chandra X-ray Observatory and XMM-Newton are allowing us to explore the X-ray emission from galaxies at moderate to high redshift. By using the stacking method, we show that we can detect the ensemble emission from normal elliptical, spiral and irregular galaxies out to redshifts approaching one. The average X-ray luminosity can then be compared with the results of models of the evolution in the numbers of X-ray binaries and can possibly be used to constrain models of star formation. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

The influence of the wind direction and plants on the variability of topsoil magnetic susceptibility in industrial and urban areas of southern Poland     

Tadeusz Magiera  Henryk Parzentny  Adam Łukasik 《Environmental Earth Sciences》2016,75(3):213

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The distributional and nutritional impacts and mitigation potential of emission-based food taxes in the UK     

Ariane Kehlbacher  Richard Tiffin  Adam Briggs  Mike Berners-Lee  Peter Scarborough 《Climatic change》2016,137(1-2):121-141

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