DISCUSSION     

Robert S. Guthrie 《Ground water》1997,35(4):562-564

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Resolution Sensitivity and Scaling of Large-Eddy Simulations of the Stable Boundary Layer   总被引：1，自引：5，他引：1  

Robert J. Beare  Malcolm K. Macvean 《Boundary-Layer Meteorology》2004,112(2):257-281

Large-eddy simulations (LES) of the continuously turbulent quasi-equilibrium stable boundary layer (SBL) are conducted with grid lengths in the range of 12.5 m to 2 m, in order to explore resolution sensitivity, and determine at what point grid convergence occurs. The structure of the mean potential temperature, winds, and turbulent fluxes varies significantly over this resolution range. The highest resolution simulations show a significant degree of convergence. The dimensionless momentum diffusivity asymptotes to a value of 0.06, corresponding to a limiting flux Richardson number of 0.15.Using the converged simulations, some scaling hypotheses underpinning first-order and second-order closure models are revisited. The effective Richardson number stability functions of the LES are compared with the forms often used in numerical weather prediction (NWP). The mixing implied by the LES is less than that used in NWP. The commonly used similarity profiles for heat and momentum fluxes, and the scalings for dissipation and pressure covariances are compared with the LES. This information could provide guidance for the next generation of SBL parametrization schemes.  相似文献   

Observational and Numerical Study on the Influence of Large-Scale Flow Direction and Coastline Shape on Sea-Breeze Evolution     

Robert C. Gilliam  Sethu Raman  Dev Dutta S. Niyogi 《Boundary-Layer Meteorology》2004,111(2):275-300

In this study radar, surface observations and numericalsimulations are used to examine the inland penetrationand intensity of the sea breeze during various large-scaleflow regimes along the curved coastline of the Carolinas,U.S.A. The results clearly indicate that the flow directionrelative to the curved coastline has a significant effecton the sea-breeze evolution.Overall, during northerly flow regimes alongthe curved North Carolina coast, observationsand numerical simulations show that the sea-breezefront has a tendency to remain close to the south-facingcoast. During these same flow regimes the frontmoves further inland relative to the east-facingcoast. The sea-breeze front during westerly flowcases progressed further inland relative to the southcoast and less so from the east-facing coastline.South-westerly flow allows the sea breeze to moveinland from both coastlines but the coastal shapeinfluence makes the inland penetration less fromthe easterly facing beaches. During periods of lightonshore flow (south-east), the sea breeze movesconsiderable distances inland but is not discernableuntil later in the afternoon. The simulations indicatedthat the sea-breeze intensity is greatest (least) when thelarge-scale flow direction has an offshore (onshore)component. Model results indicate the existence of astrong front well inland in the late afternoon duringlight onshore flow. Also noted was that the simulatedsea-breeze front develops earlier in the afternoon duringoffshore regimes and later in the day as the large-scaleflow becomes more onshore. It is concluded that thecoastline shape and coast-relative flow direction areimportant factors in determining how the sea-breezecirculation evolves spatially.  相似文献   

The Effects of Climate Change on Water Resources in the West: Introduction and Overview     

Tim Barnett  Robert Malone  William Pennell  Detlet Stammer  Bert Semtner  Warren Washington 《Climatic change》2004,62(1-3):1-11

The results of an experimental `end to end' assessment of the effects of climate change on water resources in the western United States are described. The assessment focuses on the potential effects of climate change over the first half of the 21st century on the Columbia, Sacramento/San Joaquin, and Colorado river basins. The paper describes the methodology used for the assessment, and it summarizes the principal findings of the study. The strengths and weaknesses of this study are discussed, and suggestions are made for improving future climate change assessments.  相似文献   

An accurate and robust multigrid algorithm for 2D forward resistivity modelling   总被引：1，自引：0，他引：1  

Robert Moucha  Richard C. Bailey 《Geophysical Prospecting》2004,52(3):197-212

We present an adaptation of the full multigrid algorithm in DC resistivity modelling in an effort to increase its accuracy. There is a great difficulty with conventional multigrid solvers in representing the physics of an arbitrary distribution of electrical conductivity on a very coarse grid. In general, conventional rectangular finite‐difference or 5‐point approximations of Poisson's equation cannot represent, at a coarse grid level, the effective anisotropy on a coarse scale which results from fine structure in the model. An exception to this generalization occurs when the principal axes of structural anisotropy are aligned with the coordinate axis. Additional and similarly generated problems arise when a coarse cell is obliged to represent fine structure containing very high conductivity contrasts. We have developed an adaptation of the usual resistive‐network representation of the continuum, which avoids some of these problems, and have compared it with the traditional resistive network currently used. The network adaptation consists of replacing the usual 5‐point Laplacian operator stencil used on the finite‐difference grid with a 9‐point stencil, and the conductivity scalar with a 6‐parameter conductivity parametrization. This parametrization permits representation of arbitrarily orientated anisotropy as well as more complex behaviour related to high conductivity contrasts. The importance of multigrid solvers does not lie in their speed at forward modelling (which is comparable with other methods), but rather in their potential for inverse modelling. Inverse solvers which proceed by refinement of an initially very coarse solution can, in principle, take time only linearly proportional to the number of gridpoints in the final desired model.  相似文献   

Submarine Ground Water Discharge and Salt Penetration Across the Sea Floor   总被引：1，自引：0，他引：1  

Henry Bokuniewicz  Meagen Pollock  John Blum  Robert Wilson 《Ground water》2004,42(7):983-989

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Heating in the solar atmosphere     

Robert Erdélyi 《Astronomy& Geophysics》2004,45(4):4.34-4.37

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The making of Stars 'R' Us!     

Serena Viti  Wendy Brown  Martin McCoustra  Helen Fraser  Nigel Mason  Robert Massey 《Astronomy& Geophysics》2004,45(6):6.22-6.24

The team behind a successful project to broaden the understanding of astrochemistry – Serena Viti, Wendy Brown, Martin McCoustra, Helen Fraser, Nigel Mason and Robert Massey – recount how they went about it and what benefits resulted.  相似文献   

Fate and Transport of Pharmaceuticals and Endocrine Disrupting Compounds During Ground Water Recharge     

Robert W. Masters  Ingrid M. Verstraeten  Thomas Heberer 《Ground Water Monitoring & Remediation》2004,24(2):54-57

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Physical disturbance creates bacterial dominance of benthic biological communities in tropical deltaic environments of the Gulf of Papua   总被引：1，自引：0，他引：1  

Josephine Y. Aller  Robert C. Aller 《Continental Shelf Research》2004,24(19):2395

Unlike many reactive continental shelf mud deposits in temperate regions, bacteria and microfauna rather than macrofauna typically dominate benthic biomass and activities over large areas of the Gulf of Papua (GoP) deltaic complex, Papua New Guinea. During mid NW monsoon periods (Jan–Feb), macrofaunal densities at Gulf stations were relatively low (), large macroinfauna were absent (upper 25 cm), and small (), surface deposit-feeding polychaetes and tubiculous amphipods were dominant, reflecting a frequently destabilized seabed and high sedimentation/erosion rates. Although frequent physical disturbance generally inhibits development of macrobenthic communities, some regions of the Gulf deposits are periodically colonized and extensively bioturbated during quiescent periods, as shown by preserved biogenic sedimentary structures. Bacterial inventories integrated over the top 20 cm were extremely variable within each sub region of the clinoform complex. A possible bimodal pattern with bathymetric depth and distance offshore may occur: lowest-inventories within the sandy, proximal Fly River delta, an open Gulf inner topset zone (10–20 m) having sites of relatively high inventories, an open Gulf mid-topset region with intermediate values and less extreme variation, and the outer topset—upper foreset zone (40–50 m) where highest values are attained (). Various measures of microbial activity, including measures proportional to the cellular rRNA content and the proportion of dividing cells, indicate extremely productive populations over the upper 1-m of the seabed throughout the Gulf of Papua region. Bacterial biomass (0–20 cm) including data of Alongi et al. (1991, 1992, 1995) varied from a low of in intertidal mud banks to a high of in the topset—foreset zone. Macrofaunal biomass did not exceed in any sampled region, ranging from 0.009±0 to with no obvious correlation with bathymetric depth (1–63 m). Meiofaunal biomass was generally an order of magnitude lower than macrofaunal biomass. Relatively elevated bacterial biomass and high turnover rates are consistent with high measured rates of benthic remineralization, presumably reflecting the rapid response time of bacteria to physical reworking, the associated entrainment of organic substrate, and flushing of metabolites. Solute exchange is also enhanced below the directly mixed surface region, possibly producing ‘far field’ stimulation of microbes in underlying deposits. Physical reworking and reoxidation of sediments between 10 and 50 m water depth maintain suboxic, nonsulfidic conditions in the upper 0.5–1 m despite active microbial communities and high benthic remineralization rates.  相似文献