Winter daily precipitation variability over the South West Peninsula of England     

I. D. Phillips  H. Denning 《Theoretical and Applied Climatology》2007,87(1-4):103-122

Summary Daily precipitation totals for five consecutive winters (1995–99) were obtained for 127 stations in Devon and Cornwall to explore spatial variations in rainfall. This dataset was assembled with the explicit aim of assessing the appropriateness of current arrangements for daily rainfall forecasts in the SW Peninsula of England. Firstly, the extent to which fundamental geographic variables determine precipitation was investigated by correlating each station’s mean wet day amount (WDA) and percentage of wet days (PERWET) with altitude, latitude, longitude and distance from the coast. Altitude emerged as the most important control on precipitation, with a two-variable multiple linear regression model containing altitude and latitude being able to explain 39.3% (29.8%) of the variance in WDA (PERWET) values. The main spatial modes of variability in the region’s precipitation field were identified by using S mode principal components analysis (PCA). Six PCs were statistically significant and explained 83.4% of the geographic variance in precipitation over Devon and Cornwall. The components were interpreted physically by examining the synoptic flow environment (pressure and wind anomalies) on days with high positive and negative PC scores. Explaining 25.1% of the variance, the most important pattern (PC1) depicts a location’s degree of exposure or shelter in a moist, unstable W–NW airflow. The higher PCs describe modes of variability that accentuate rainfall in East Devon (PC2), Cornwall (PC3), Dartmoor and Bodmin Moor (PC4), South Devon (PC5), and North Cornwall and NW Devon (PC6) relative to other areas of the Peninsula. Finally, a winter precipitation regionalisation was derived by applying agglomerative hierarchical cluster analysis to the PC loadings of the significant components. In most cases, the six coherent precipitation regions do not reflect the familiar administrative or topographic areas used for forecasting, suggesting that forecasts issued on such a basis are likely to be insufficiently detailed and misleading.  相似文献   

The Palaeozoic tectono-metallogenic evolution of the northern Tasman Fold Belt System, Australia: Interplay of subduction rollback and accretion     

I.M.A. Vos  F.P. Bierlein  D. Phillips 《Ore Geology Reviews》2007,30(3-4):277-296

The Tasman Fold Belt System in eastern Australia provides a record of the Palaeozoic geological history and growth of the Australian continent along the proto-Pacific margin of Gondwana inboard of an extensive and long-lived subduction system. The Hodgkinson and Broken River provinces represent prominent geological elements of this system and together form the northern Tasman Fold Belt System. Geochronological age dating of the timing of gold formation in the Amanda Bel Goldfield in the Broken River Province and the Hodgkinson Goldfield in the Hodgkinson Province provides constraints on the occurrence of a deformation and mineralisation episode in the Late Devonian–Early Carboniferous. Integration of these newly-obtained data with petrogenetic constraints and a time–space evaluation of the geological evolution of the Hodgkinson and Broken River provinces, as well as other terranes in the northern Tasman Fold Belt System, allows for the development of a geodynamic model for the Palaeozoic evolution of the northern Tasman Fold Belt System. Our model indicates that three cycles of extension–contraction occurred during the Palaeozoic evolution of the northern Tasman Fold Belt System. Episodes of extension were controlled by rollback of the subduction system along the proto-Pacific margin of Gondwana, whereas episodes of contraction resulted from accretion following the arrival of positively buoyant segments (i.e., micro-continental blocks/oceanic plateaus) at the subducting trench.Our composite interpretative model on the geodynamic evolution of the northern Tasman Fold Belt System integrates the timing of the development of mineral deposits throughout this part of the system and provides a significant advancement in the understanding of Palaeozoic geodynamics along the margin of Gondwana in northeast Australia and allows comparison with the southern part of the Tasman Fold Belt System.  相似文献   

A coupling of mixed and continuous Galerkin finite element methods for poroelasticity II: the discrete-in-time case     

Phillip Joseph Phillips  Mary F. Wheeler 《Computational Geosciences》2007,11(2):145-158

In this paper, we formulate a finite element procedure for approximating the coupled fluid and mechanics in Biot’s consolidation model of poroelasticity. Here, we approximate the pressure by a mixed finite element method and the displacements by a Galerkin method. Theoretical convergence error estimates are derived in a discrete-in-time setting. Of particular interest is the case when the lowest-order Raviart–Thomas approximating space or cell-centered finite differences are used in the mixed formulation and continuous piecewise linear approximations are used for displacements. This approach appears to be the one most frequently applied to existing reservoir engineering simulators.  相似文献   

A coupling of mixed and continuous Galerkin finite element methods for poroelasticity I: the continuous in time case     

Phillip Joseph Phillips  Mary F. Wheeler 《Computational Geosciences》2007,11(2):131-144

In this paper, we formulate a finite element procedure for approximating the coupled fluid and mechanics in Biot’s consolidation model of poroelasticity. Here, we approximate the pressure by a mixed finite element method and the displacements by a Galerkin method. Theoretical convergence error estimates are derived in a continuous in-time setting for a strictly positive constrained specific storage coefficient. Of particular interest is the case when the lowest-order Raviart–Thomas approximating space or cell-centered finite differences are used in the mixed formulation, and continuous piecewise linear approximations are used for displacements. This approach appears to be the one most frequently applied to existing reservoir engineering simulators.  相似文献   

Nonrenewable resources in economic, social, and environmental sustainability     

Deborah J. Shields 《Natural Resources Research》1998,7(4):251-261

This paper reviews the linkages among energy and mineral resources and economic, social, and environmental sustainability. Nonrenewable resources are shown to be integral components of sustainability, regardless of which paradigmatic definition of the concept is invoked. Potential measures of the degree to which nonrenewable resources contribute to or detract from sustainability are presented. We conclude that a set of such measures should be incorporated in the comprehensive framework of sustainability currently being developed by the Federal government. National scale indicators could be presented within the structure of the seven criteria from the Santiago Declaration, whereas a life cycle or materials flow approach could be used when sustainability of specific resources is at issue.  相似文献   

The impact of vertebrate herbivores on wetland vegetation in Atchafalaya Bay, Louisiana     

D. Elaine Evers  Charles E. Sasser  James G. Gosselink  Deborah A. Fuller  Jenneke M. Visser 《Estuaries and Coasts》1998,21(1):1-13

Delta islands in the Atchafalaya and Wax Lake deltas in Atchafalaya Bay, Louisiana, are in an extremely dynamic successional phase. These islands initially supported large marshes dominated by the pioneering plant species Sagittaria latifolia and Sagittaria platyphylla. A general decrease in vegetated areas has occurred in the delta island marshes in the Atchafalaya Delta since about 1980, while in the Wax Lake Delta portion of the complex the vegetation still flourished. The Atchafalaya Delta provides an interesting setting for the study of herbivory because of the complex interaction of biotic and physical factors operating in this delta. We hypothesized that grazing by herbivores has a marked effect on vegetation in these developing marshes. To test this hypothesis, exclosures were erected on islands in both deltas in September 1985 and January 1986. Each set of exclosure treatments included an openly-grazed control area, an ungrazed area, an area allowing nutria grazing, and one allowing waterfowl grazing in each site. Results of the experiment, based on field sampling of vegetation, indicated decreases in plant biomass and changes in plant species composition in grazed treatments. Waterfowl and nutria reduced biomass aboul equally, but there was a more marked effect in the openly grazed areas. These findings may be extrapolated to sediment diversion areas along the Mississippi River.  相似文献   

Regional retrograde metamorphism of a high grade terrain: the Willyama Complex,Broken Hill,Australia     

G.J. Corbett  G.N. Phillips 《Lithos》1981,14(1):59-73

Retrograde metamorphism has been a major influence in the development of the presently observed lithologies of the Willyama Complex, Broken Hill. Two broad types of retrogression are distinguished: pseudomorphous and kinematic retrogression. The former type of retrogression involves replacement of prograde phases without complete loss of the high grade fabric; hence the prograde assemblage can frequently be inferred. Kinematic retrogression involves the development of a new schistose fabric and, like pseudomorphous retrogression, is commonly related to F₃ deformation. Retrogression was initiated during the waning stage of prograde metamorphism and was accompanied by an influx of aqueous fluid at similar pressure, but lower temperature conditions than prograde metamorphism. The source of the water is believed to be the crystallization of cooling partial melts. The regional nature of this ‘Willyama-style’ of retrogression is attributed to the metasediment-rich nature of the sequence, the high geothermal gradient and the considerable amount of in situ partial melting.  相似文献   

Water activity changes across an amphibolite-granulite facies transition,Broken Hill,Australia     

G. Neil Phillips 《Contributions to Mineralogy and Petrology》1981,75(4):377-386

Phase compositions in pelitic and mafic gneisses place tight constraints on pressure (ranging from 3 up to 6 kb), and, to a lesser extent, on temperature (500° up to 800° C) during prograde regional metamorphism of the Willyama Complex, Broken Hill, SE Australia. These limits allow an evaluation of water activity across the terrain using various equilibria in pelitic and mafic gneisses. The stability of cummingtonite and biotite over much of the terrain places upper limits on temperature, and the presence of syn-metamorphic partial melts in the metasediments places lower limits on a(H₂O). Garnet-biotitesillimanite-K feldspar-quartz relations combined with the partial melting data suggest a decrease in water activity from near 1.0 in the lower grade zones to 0.5±0.2 in the Broken Hill — Little Broken Hill part of the two pyroxene zone. This result is compatible with less precise hornblende-orthopyroxene-clinopyroxene-quartz relations.These P-T-a(H₂O) data from the Willyama Complex support a continuum from amphibolite to granulite facies, as proposed by Binns (1964) and suggest that the higher grade assemblages are formed in response to both higher temperature and lower water activity. The formation of granulite facies terrains by prior crustal dehydration is unsubstantiated in the present example. Instead, the decrease from a(H₂O)-1.0 in the andalusite/sillimanite-muscovite zones to a(H₂O) < 1.0 found at higher grades, is likely to reflect buffering by partial melting and dehydration reactions in the volumetrically dominant metasediments.  相似文献   

Minerals of Brazil: R.R. Franco,A. Leprevost,J.J. Bigarella and A. Bolsanello, 1975. Elsevier,Amsterdam, 3 vols., 426 pp., 869 colour plates,Dfl. 200.00     

F.C. Phillips 《Earth》1975,11(4):369-370

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Effects of stem density upon sediment retention by salt marsh cord grass,Spartina alterniflora loisel   总被引：1，自引：0，他引：1  

Mark L. Gleason  Deborah A. Elmer  Natalie C. Pien  John S. Fisher 《Estuaries and Coasts》1979,2(4):271-273

A laboratory experiment was conducted to determine whether retention of waterborne sand by salt marsh cordgrass, Spartina alterniflora Loisel, is directly related to the number of stems per unit area. Waves generated in a trough washed over a sloping beach planted with S. alterniflora sprigs: a range of stem densities (0–108 stems/m²) was examined in separate trials. The amount of sand accumulated after 60 waves is a positive nonlinear function of stem density. The greatest accretion coincided with the highest stem density tested. Shape of the beach profile was also strongly influenced by the number of stems per m².  相似文献