Remote Sensing Observations of Effects of Mountain Blocking on Travelling Gravity-Shear Waves and Associated Clouds     

Roger F. Reinking  A. Shelby Frisch  Brad W. Orr  David L. Korn  Luc R. Bissonnette  Gilles Roy 《Boundary-Layer Meteorology》2003,109(3):255-284

Trapped Kelvin–Helmholtz (K–H) waves and vortices were monitored as they were generated immediately upwind of a mountain and driven into the barrier by a low-level jet. A stratus cloud visually revealed the embedded, propagating, gravity-shear waves. Interactions of the waves with the mountain were deciphered using remote sensing measurements of the structure, motions, and microphysics within the cloud and conceptual models based on existing theories. The observations show that the mountain acted as a dam to the flow that was primed for, but did not spontaneously induce, the waves. In response to the blocking, the waves spatially developed a pattern of formation, amplification, and breakdown between the upstream flow and the barrier, and altered the associated clouds in the process. Notably, radar signatures of velocity variance depicted organized, intertwined ribbons of relatively large vorticity within the wave layer. These provided measured evidence of the vortex sheet and streamwise vortex tubes predicted by advanced K–Hinstability theory, the three-dimensional version of Scorer's `stripe', the layer of rotational fluid between opposed flows that led to the wave generation. A theory of resonant interaction of wave trains, but with blocking imposed, appears to explain the internal structure of the pile-up of the flow and wave amplification approaching the barrier. Evolution of the supporting atmospheric thermal structure and introduction of a boundary-layer flow reversal follow a current model of blocking, although some features may have developed more directly from wave-driven mixing. The remote sensors also measured the influence of the waves on the cloud liquid water, including a cumulative enlargement of droplets as they were carried through a series of waves.  相似文献   

A groundwater tracing investigation as an aid of locating groundwater monitoring stations on the Mitchell Plain of southern Indiana   总被引：1，自引：0，他引：1  

Wanfang Zhou  Barry F. Beck  Arthur J. Pettit  Brad J. Stephenson 《Environmental Geology》2002,41(7):842-851

. A groundwater tracing study was conducted on the Mitchell Plain of southern Indiana to aid in the design of a karst groundwater monitoring program for a proposed landfill facility. Fluorescein and rhodamine WT dyes were introduced into sinkholes at the project site. On-site fluorometric analyses and concentration-dependent sampling were utilized at springs and a local stream for data resolution while minimizing delays between tracing events. As a result of this investigation, springs including a submerged spring that drain groundwater from the site have been identified and two groundwater monitoring stations have been established. The submerged spring was discovered in the streambed at intersections between prominent joints and solution-enlarged bedding-plane partings. It could not have been identified readily during a typical karst hydrogeologic inventory, nor would it have been detected by analyzing charcoal dye receptors with a spectrofluorophotometer.  相似文献   

Modeling spatial dependence in high spatial resolution hyperspectral data sets     

Daniel A. Griffith 《Journal of Geographical Systems》2002,4(1):43-51

 As either the spatial resolution or the spatial scale for a geographic landscape increases, both latent spatial dependence and spatial heterogeneity also will tend to increase. In addition, the amount of georeferenced data that results becomes massively large. These features of high spatial resolution hyperspectral data present several impediments to conducting a spatial statistical analysis of such data. Foremost is the requirement of popular spatial autoregressive models to compute eigenvalues for a row-standardized geographic weights matrix that depicts the geographic configuration of an image's pixels. A second drawback arises from a need to account for increased spatial heterogeneity. And a third concern stems from the usefulness of marrying geostatistical and spatial autoregressive models in order to employ their combined power in a spatial analysis. Research reported in this paper addresses all three of these topics, proposing successful ways to prevent them from hindering a spatial statistical analysis. For illustrative purposes, the proposed techniques are employed in a spatial analysis of a high spatial resolution hyperspectral image collected during research on riparian habitats in the Yellowstone ecosystem. Received: 25 February 2001 / Accepted: 2 August 2001  相似文献   

Displacement‐based seismic analysis for out‐of‐plane bending of unreinforced masonry walls     

K. Doherty  M. C. Griffith  N. Lam  J. Wilson 《地震工程与结构动力学》2002,31(4):833-850

This paper addresses the problem of assessing the seismic resistance of brick masonry walls subject to out‐of‐plane bending. A simplified linearized displacement‐based procedure is presented along with recommendations for the selection of an appropriate substitute structure in order to provide the most representative analytical results. A trilinear relationship is used to characterize the real nonlinear force–displacement relationship for unreinforced brick masonry walls. Predictions of the magnitude of support motion required to cause flexural failure of masonry walls using the linearized displacement‐based procedure and quasi‐static analysis procedures are compared with the results of experiments and non‐linear time‐history analyses. The displacement‐based procedure is shown to give significantly better predictions than the force‐based method. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Binding of Fe³⁺ by humic materials     

N. Senesi  S.M. Griffith  M. Schnitzer  M.G. Townsend 《Geochimica et cosmochimica acta》1977,41(7):969-976

  相似文献   

The Quaternary     

Philip Gibbard Brad Pillans 《《幕》》2008,31(2):202-202

In late July 2007, some 1100 Quaternary scientists gathered for a week-long conference in the tropical city of Cairns in northeast Australia for the 17th quadrennial congress of the International Union for Quaternary Research （INQUA）. Conference presentations were on topics in such diverse fields as archaeology, stratigraphy, geomorphology, palaeontology, geochemistry, hydrology, climate change and geochronology. To an outsider, the unifying theme of an INQUA Congress may be difficult to grasp, but diversity has always been a characteristic of Quaternary research, more so than for any other major period of the geological time scale.  相似文献   

The geographic distribution of metals in urban soils: the case of Syracuse,NY     

D. A. Griffith  D. L. Johnson  A. Hunt 《GeoJournal》2009,74(4):275-291

A paucity of literature currently exists pertaining to the high-resolution geographic distribution of metal contaminants across urban areas. Thousands of soil samples were collected across Syracuse, NY to secure empirical evidence about such geographic distributions. Metal measurements were made with XRF technology, with quality assessments based upon replicate samples as well as ICP technology summarized here. Both metal covariations and their spatial structure are described, followed by mapping of selected metal measurements based upon sample points, as well as census block group and census tract aggregates. A simple comparison is presented between certain of these empirical results and a selected non-urban landscape (a river floodplain). Finally, implications drawn from the empirical evidence presented include covariation assessments with selected census data that serve as surrogates for poverty.  相似文献   

草地异戊二烯排放通量影响因子的研究   总被引：9，自引：1，他引：8  

白建辉  Brad Baker 《大气科学》2004,28(5):783-794

2002年夏季对中国内蒙古草原挥发性有机物的排放通量进行的首次测量结果表明,其主要成分异戊二烯的排放有明显的日变化和季节变化.采样箱对太阳辐射有非常明显的衰减作用,其衰减率为17%～35%.为准确估算异戊二烯的排放通量,建立其排放模式是非常必要的.基于可见光辐射传输与守恒的观点,在观测数据的基础上建立了异戊二烯排放通量的经验模式.结果表明,对日变化、季节变化和日总量的模拟值与测量值比较一致.在使用箱方法时,应该考虑箱内外辐射、温湿度、水汽含量之差引起的排放通量的差别,特别是箱内外辐射之差所引起排放通量的差别.同时也说明,可见光辐射是影响异戊二烯排放的最主要因子.利用异戊二烯排放通量的日总量与11:00通量之比和可见光辐射日总量与11:00时累计值之比的定量关系,可以由某日11:00的排放通量来推算该日的日总量,其平均相对偏差小于14%.  相似文献   

Carbonate-associated sulfate as a proxy for lake level fluctuations: a proof of concept for Walker Lake, Nevada     

William Berelson  Frank Corsetti  Brad Johnson  Toan Vo  Chris Der 《Journal of Paleolimnology》2009,42(1):25-36

Closed-basin alkaline lakes record climate change particularly well because they generally contain a sedimentary record that is high in carbonate mineral content from which climate proxies can be determined. Various approaches are used to estimate paleo-lake level and volume (δ¹⁸O, dating of “shoreline” tufas, biotic proxies, etc.), yet all carry certain caveats that limit their usefulness. Ultimately, the relationship between the chemistry of the lake, the volume of the lake, and the response of the proxy will determine how well a proxy serves a paleolimnologic purpose. Here, we discuss the use of carbonate-associated sulfate (CAS), the sulfate contained within the lattice of carbonate minerals that precipitate in lake water, as a proxy for lake water chemistry and by extension, lake volume. Walker Lake, an alkaline closed-basin lake in western Nevada, has experienced a well-documented lake-level decline since 1880 and provides a test case for CAS as a lake-level proxy. By extracting the CAS from sedimentary carbonate and tufas that have been age dated, we can relate these values to lake sulfate content based on historical or other proxy data. We confirm that CAS tracks lake sulfate. Our study of sedimentary carbonates demonstrates that CAS is a linear function of lake sulfate through a range of 10–25 mM, which corresponds to a change in lake level of 30 m. As confirmation of the CAS technique, we analyzed a stromatolitic tufa dated using AMS ¹⁴C. The CAS trend in the stromatolite suggested that it grew during a lake-level decline, a result consistent with other proxy data. Finally, laboratory experiments were conducted that demonstrate CAS is monotonically correlated with sulfate concentration and that precipitation kinetics are not likely a major control on CAS in alkaline lakes, but that ionic strength of the solution exerts a strong control on CAS.  相似文献   

Evaluation of pollutant build-up and wash-off from selected land uses at the Port of Brisbane, Australia     

Goonetilleke A  Egodawatta P  Kitchen B 《Marine pollution bulletin》2009,58(2):213-6259

The quality of stormwater runoff from seaports can be an important source of pollution to the marine environment. Currently, little knowledge exists with regards to the pollutant generation capacity specific to seaports as they do not necessarily compare well with conventional urban land use. The research project focussed on the assessment of pollutant build-up and wash-off. The study was undertaken using rainfall simulation and small impervious plots for different port land uses with the results obtained compared to typical urban land uses.The study outcomes confirmed that the Port land uses exhibit comparatively lower pollutant concentrations. However, the pollutant characteristics varied across different land uses. Hence, the provision of stereotypical water quality improvement measures could be of limited value. Particle size <150 μm was predominant in suspended solids. Therefore, if suspended solids are targeted as the surrogate parameter for water quality improvement, this particle size range needs to be removed.  相似文献