Investigating the influence of aquifer heterogeneity on the potential for thermal free convection in the Yarragadee Aquifer,Western Australia     

Dylan J. Irvine  Heather A. Sheldon  Craig T. Simmons  Adrian D. Werner  Cedric M. Griffiths 《Hydrogeology Journal》2015,23(1):161-173

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Quantifying Changes in Extreme Weather Events in Response to Warmer Global Temperature     

Travis R. Moore  H. Damon Matthews  Christopher Simmons  Martin Leduc 《大气与海洋》2015,53(4):412-425

Global warming is expected to affect both the frequency and severity of extreme weather events, though projections of the response of these events to climate warming remain highly uncertain. The range of changes reported in the climate modelling literature is very large, sometimes leading to contradictory results for a given extreme weather event. Much of this uncertainty stems from the incomplete understanding of the physics of extreme weather processes, the lack of representation of mesoscale processes in coarse-resolution climate models, and the effect of natural climate variability at multi-decadal time scales. However, some of the spread in results originates simply from the variety of scenarios for future climate change used to drive climate model simulations, which hampers the ability to make generalizations about predicted changes in extreme weather events. In this study, we present a meta-analysis of the literature on projected future extreme weather events in order to quantify expected changes in weather extremes as a function of a common metric of global mean temperature increases. We find that many extreme weather events are likely to be significantly affected by global warming. In particular, our analysis indicates that the overall frequency of global tropical cyclones could decrease with global warming but that the intensity of these storms, as well as the frequency of the most intense cyclones could increase, particularly in the northwestern Pacific basin. We also found increases in the intensity of South Asian monsoonal rainfall, the frequency of global heavy precipitation events, the number of North American severe thunderstorm days, North American drought conditions, and European heatwaves, with rising global mean temperatures. In addition, the periodicity of the El Niño–Southern Oscillation may decrease, which could, in itself, influence extreme weather frequency in many areas of the climate system.  相似文献   

Groundwater modelling in decision support: reflections on a unified conceptual framework     

John Doherty  Craig T. Simmons 《Hydrogeology Journal》2013,21(7):1531-1537

Groundwater models are commonly used as basis for environmental decision-making. There has been discussion and debate in recent times regarding the issue of model simplicity and complexity. This paper contributes to this ongoing discourse. The selection of an appropriate level of model structural and parameterization complexity is not a simple matter. Although the metrics on which such selection should be based are simple, there are many competing, and often unquantifiable, considerations which must be taken into account as these metrics are applied. A unified conceptual framework is introduced and described which is intended to underpin groundwater modelling in decision support with a direct focus on matters regarding model simplicity and complexity.  相似文献   

Existence and stability of symmetric periodic simultaneous binary collision orbits in the planar pairwise symmetric four-body problem     

Lennard F. Bakker  Tiancheng Ouyang  Duokui Yan  Skyler Simmons 《Celestial Mechanics and Dynamical Astronomy》2011,110(3):271-290

We analytically prove the existence of a symmetric periodic simultaneous binary collision orbit in a regularized planar pairwise symmetric equal mass four-body problem. This is an extension of our previous proof of the analytic existence of a symmetric periodic simultaneous binary collision orbit in a regularized planar fully symmetric equal mass four-body problem. We then use a continuation method to numerically find symmetric periodic simultaneous binary collision orbits in a regularized planar pairwise symmetric 1, m, 1, m four-body problem for m between 0 and 1. Numerical estimates of the the characteristic multipliers show that these periodic orbits are linearly stability when 0.54 ≤ m ≤ 1, and are linearly unstable when 0 < m ≤ 0.53.  相似文献   

The compleat Darcy: new lessons learned from the first English translation of Les Fontaines Publiques de la Ville de Dijon     

Sharp JM  Simmons CT 《Ground water》2005,43(3):457-460

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Using quantitative indicators to evaluate results from variable-density groundwater flow models   总被引：1，自引：1，他引：0  

Awadhesh Prasad  Craig T. Simmons 《Hydrogeology Journal》2005,13(5-6):905-914

Variable-density transport models are typically tested by comparing model output with the results of three standard test cases: (1) the HYDROCOIN Level 1, Case 5 salt dome problem—Organisation for Economic Co-operation and Development (OECD 1988), (2) the Henry (1964) approximate analytic solution for steady-state saltwater intrusion and (3) the Elder (1967) problem for complex natural convection where fluid flow is driven purely by fluid-density differences. The complex flow phenomena that result in many variable-density flow problems often means that the intercode testing (and the evaluation of results from variable-density flow models more generally) is largely limited to a visual inspection of isochlor distributions. Visual inspection can often be quite subjective, prone to errors and may not allow easy detection of discrepancies, especially when they are small. Moreover, a match of certain isochlors at a number of prescribed time intervals does not necessarily enure the model is adequately tested. Recently, the well-studied Elder problem has been the subject of significant discussion in the research literature. Authors such as Diersch and Kolditz (2002) have shown that the solutions obtained to the Elder problem are dependent upon the level of grid discretization used. Simpson and Clement (2003) stated that the results of the Elder problem can only be matched in a qualitative sense because the problem is highly sensitive to discretization. In this paper, a number of quantitative indicators are developed that can be used for a more rigorous quantitative evaluation of results of variable-density flow models. They may also find application in future model benchmarking practice.

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Resumen Los modelos de transporte de densidad variable se prueban típicamente mediante la comparación de los resultados del modelo con los resultados de tres casos de prueba estándar: (1) el problema de domo de sal HYDROCOIN nivel 1, caso 5—Organización de desarrollo y cooperación económica (OECD 1988), (2) la solución analítica aproximada de Henry (1964) para la intrusión de sal en estado constante y (3) el problema de Elder (1967) para la convexión natural compleja donde el flujo de fluido es determinado únicamente por las diferencias de densidad entre fluidos. Los fenómenos de flujo complejo que resultan en varios problemas de flujo de densidad variable con frecuencia significan que las pruebas de intercodificación (y la evaluación de resultados de modelos de flujo de densidad variable más generalmente) se limita principalmente a una inspección visual de las distribuciones de la intrusión de agua salada. La inspección visual con frecuencia puede ser bastante subjetiva, propensa a errores y es posible que no permita detectar fácilmente las discrepancias, especialmente cuando son pequeñas. Más aún, la concordancia de ciertas intrusiones de agua salada en un número de intervalos de tiempo prescritos no necesariamente asegura que el modelo haya sido probado adecuadamente. Recientemente, el bien estudiado problema de Elder ha sido objeto de discusiones siginificativas en la literatura de investigación. Los autores tales como Diersch y Kolditz (2002) han mostrado que las soluciones obtenidas para el problema Elder dependen del nivel de discretización de mallas utilizado. Simpson y Clement (2003) afirman que los resultados del probelma de Elder se pueden corrobar únicamente en un sentido cualitativo porque el problema es sumamente sensible a la discretización. En este artículo se ha desarrollado un número de indicadores cuantitativos que pueden ser utlizados para una evaluación cuantitativa más rigurosa de los resultados de los modelos de flujo de densidad variable. Es posible que también se puedan aplicar en el futuro para prácticas de modelos de benchmarking.

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Résumé Utilisation dindicateurs quantitatifs pour lévaluation de modèles découlement à densité variable de leau souterraine. On évalue généralement les modèles de transport à densité variable en comparant les résultats obtenus grâce à ces modèles aux résultats de trois essais standards: (1) le problème «dôme de sel» HYDROCOIN, niveau 1, cas 5—Organisation de coopération et de développement économiques (OCDE 1988), (2) la solution analytique approximative de Henry (1964) pour lintrusion deau salée en régime permanent, et (3) le problème de Elder (1976) pour la convection naturelle complexe, où lécoulement du fluide est engendré par les seules différences de densité. Les phénomènes complexes découlement qui résultent de plusieurs problèmes découlement à densité variable signifient souvent que la comparaison entre codes (et lévaluation des résultats des modèles découlement à densité variable en général) est largement limitée à linspection visuelle des isocontours. Linspection visuelle peut souvent être assez subjective, elle peut comporter des erreurs, et il peut être difficile, par ce moyen, de détecter des différences, surtout lorsquelles sont faibles. De plus, la vérification des isocontours pour un nombre déterminé dintervalles de temps ne garantit pas que le modèle ait été mis à lépreuve de façon satisfaisante. Récemment, le modèle élaboré de Elder a été lobjet de plusieurs discussions significatives dans la littérature de la recherche. Des auteurs comme Diersch and Kolditz (2002) ont démontré que les solutions obtenues pour le problème dElder dépendaient du niveau de discrétisation du maillage utilisé. Simpson et Clement (2003) ont affirmé que les résultats du problème dElder pouvaient seulement être comparés dune manière qualitative, puisque la discrétisation influe de manière marquée sur le problème. Dans cet article, une série dindicateurs quantitatifs sont mis sur pied pour permettre une utilisation plus rigoureuse de lévaluation quantitative des résultats de modèles découlement à densité variable. Ces indicateurs pourraient également trouver leur utilité dans la pratique de la calibration des modèles.Utilización de indicadores cuantitativos para evaluar los resultados de modelos de flujo de aguas subterráneas de densidad variable.

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Evidence for material between Saturn's A and F rings from the Voyager 2 photopolarimeter experiment     

A.L. Graps  A.L. Lane  L.J. Horn  K.E. Simmons 《Icarus》1984,60(2):409-415

The region in the Saturn system between the F ring and the outer edge of the A ring is an area that appears, in images from the imaging experiment, to be virtually devoid of material except for three small satellites. Near the orbit of 1980S28, Atlas—the innermost satellite—the Voyager Photopolarimeter Stellar Occultation data show a discontinuity in count rate which marks a boundary between the tenuous materials near the outer edge of the A ring and the orbit of Atlas. The data pertaining to this region have been examined with the aid of statistics and models generated from other similar ring structures. It is concluded that the discontinuity is real, implying the existence of tenuous material of normal optical depth of 0.01 to 0.006 in this region.  相似文献   

The Local Articulation of Policy Conflict: Land Use,Environment, and Amerindian Rights in Eastern Amazonia     

Cynthia S. Simmons 《The Professional geographer》2002,54(2):241-258

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Manufactured home building regulations and the February 2, 2007 Florida tornadoes     

Kevin M. Simmons  Daniel Sutter 《Natural Hazards》2008,46(3):415-425

The Department of Housing and Urban Development (HUD) and the state of Florida implemented new wind load and tie-down regulations for manufactured homes following Hurricane Andrew. This article examines the effect of the new regulations on the likelihood that occupants of mobile homes would survive a tornado. On February 2, 2007, three tornadoes struck central Florida, resulting in 21 deaths in Lake County, all in manufactured homes. The deaths occurred almost exclusively in homes rated as leveled by the county tax appraiser. Manufactured homes built to the new regulations, however, were significantly less likely to be leveled. Regression analysis finds that manufactured homes built to the post-Andrew requirements were 79% less likely to be leveled than homes built prior to the HUD Code in 1976, and 68% less likely to be leveled than homes built after 1976 but before the 1994 wind load regulations. Construction of all manufactured homes in the tornado paths to the wind load and tie-down requirements could have reduced fatalities by 70%.

Daniel Sutter (Corresponding author)Email:

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Beyond hydrogeologic evidence: challenging the current assumptions about salinity processes in the Corangamite region, Australia     

P. G. Dahlhaus  J. W. Cox  C. T. Simmons  C. M. Smitt 《Hydrogeology Journal》2008,16(7):1283-1298

In keeping with the standard scientific methods, investigations of salinity processes focus on the collection and interpretation of contemporary scientific data. However, using multiple lines of evidence from non-hydrogeologic sources such as geomorphic, archaeological and historical records can substantially add value to the scientific investigations. By using such evidence, the validity of the assumptions about salinity processes in Australian landscapes is challenged, especially the assumption that the clearing of native vegetation has resulted in rising saline groundwater in all landscapes. In the Corangamite region of south-west Victoria, salinity has been an episodic feature of the landscapes throughout the Quaternary and was present at the time of the Aboriginal inhabitants and the first pastoral settlement by Europeans. Although surface-water salinity has increased in some waterways and the area of salinised land has expanded in some landscapes, there is no recorded evidence found which supports significant rises in groundwater following widespread land-use change. In many areas, salinity is an inherent component of the region’s landscapes, and sustains world-class environmental assets that require appropriate salinity levels for their ecological health. Managing salinity requires understanding the specific salinity processes in each landscape.  相似文献