The Turbulent Lagrangian Time Scale in Forest Canopies Constrained by Fluxes,Concentrations and Source Distributions   总被引：1，自引：1，他引：0  

Vanessa Haverd  Ray Leuning  David Griffith  Eva van Gorsel  Matthias Cuntz 《Boundary-Layer Meteorology》2009,130(2):209-228

One-dimensional Lagrangian dispersion models, frequently used to relate in-canopy source/sink distributions of energy, water and trace gases to vertical concentration profiles, require estimates of the standard deviation of the vertical wind speed, which can be measured, and the Lagrangian time scale, T _L , which cannot. In this work we use non-linear parameter estimation to determine the vertical profile of the Lagrangian time scale that simultaneously optimises agreement between modelled and measured vertical profiles of temperature, water vapour and carbon dioxide concentrations within a 40-m tall temperate Eucalyptus forest in south-eastern Australia. Modelled temperature and concentration profiles are generated using Lagrangian dispersion theory combined with source/sink distributions of sensible heat, water vapour and CO₂. These distributions are derived from a multilayer Soil-Vegetation-Atmospheric-Transfer model subject to multiple constraints: (1) daytime eddy flux measurements of sensible heat, latent heat, and CO₂ above the canopy, (2) in-canopy lidar measurements of leaf area density distribution, and (3) chamber measurements of CO₂ ground fluxes. The resulting estimate of Lagrangian time scale within the canopy under near-neutral conditions is about 1.7 times higher than previous estimates and decreases towards zero at the ground. It represents an advance over previous estimates of T _L , which are largely unconstrained by measurements.  相似文献   

Short-Term Periodicities in Sunspot Activities During the Descending Phase of Solar Cycle 23     

Partha Chowdhury  Manoranjan Khan  P. C. Ray 《Solar physics》2010,261(1):173-191

In the present study, the short-term periodicities in the daily data of the sunspot numbers and areas are investigated separately for the full disk, northern, and southern hemispheres during Solar Cycle 23 for a time interval from 1 January 2003 to 30 November 2007 corresponding to the descending and minimum phase of the cycle. The wavelet power spectrum technique exhibited a number of quasi-periodic oscillations in all the datasets. In the high frequency range, we find a prominent period of 22 – 35 days in both sunspot indicators. Other quasi-periods in the range of 40 – 60, 70 – 90, 110 – 130, 140 – 160, and 220 – 240 days are detected in the sunspot number time series in different hemispheres at different time intervals. In the sunspot area data, quasi-periods in the range of 50 – 80, 90 – 110, 115 – 130, 140 – 155, 160 – 190, and about 230 days were noted in different hemispheres within the time period of analysis. The present investigation shows that the well-known “Rieger periodicity” of 150 – 160 days reappears during the descending phase of Solar Cycle 23, but this is prominent mainly in the southern part of the Sun. Possible explanations of these observed periodicities are delivered on the basis of earlier results detected in photospheric magnetic field time series (Knaack, Stenflo, and Berdyugina in Astron. Astrophys. 438, 1067, 2005) and solar r-mode oscillations.  相似文献   

Reconstruction of a kimberlite eruption,using an integrated volcanological,geochemical and numerical approach: A case study of the Fox Kimberlite,NWT, Canada     

L.A. Porritt  R.A.F. Cas 《Journal of Volcanology and Geothermal Research》2009,179(3-4):241-264

An integrated approach involving volcanology, geochemistry and numerical modelling has enabled the reconstruction of the volcanic history of the Fox kimberlite pipe. The observed deposits within the vent include a basal massive, poorly sorted, matrix supported, lithic fragment rich, eruption column collapse lapilli tuff. Extensive vent widening during the climactic magmatic phase of the eruption led to overloading of the eruption column with cold dense country rock lithic fragments, dense juvenile pyroclasts and olivine crystals, triggering column collapse. > 40% dilution of the kimberlite by granodiorite country rock lithic fragments is observed both in the physical componentry of the rocks and in the geochemical signature, where enrichment in Al₂O₃ and Na₂O compared to average values for coherent kimberlite is seen. The wide, deep, open vent provided a trap for a significant proportion of the collapsing column material, preventing large scale run-away in the form of pyroclastic flow onto the ground surface, although minor flows probably also occurred. A massive to diffusely bedded, poorly sorted, matrix supported, accretionary-lapilli bearing, lithic fragment rich, lapilli tuff overlies the column collapse deposit providing evidence for a late phreatomagmatic eruption stage, caused by the explosive interaction of external water with residual magma. Correlation of pipe morphology and internal stratigraphy indicate that widening of the pipe occurred during this latter stage and a thick granodiorite cobble-boulder breccia was deposited. Ash- and accretionary lapilli-rich tephra, deposited on the crater rim during the late phreatomagmatic stage, was subsequently resedimented into the vent. Incompatible elements such as Nb are used as indicators of the proportion of the melt fraction, or kimberlite ash, retained or removed by eruptive processes. When compared to average coherent kimberlite the ash-rich deposits exhibit ~ 30% loss of fines whereas the column collapse deposit exhibits ~ 50% loss. This shows that despite the poorly sorted nature of the column collapse deposit significant elutriation has occurred during the eruption, indicating the existence of a high sustained eruption column. The deposits within Fox record a complex eruption sequence showing a transition from a probable violent sub-plinian style eruption, driven by instantaneous exsolution of magmatic volatiles, to a late phreatomagmatic eruption phase. Mass eruption rate and duration of the sub-plinian phase of the eruption have been determined based on the dimensions of milled country-rock boulders found within the intra-vent deposits. Calculations show a short lived eruption of one to eleven days for the sub-plinian magmatic phase, which is similar in duration to small volume basaltic eruptions. This is in general agreement with durations of kimberlite eruptions calculated using entirely different approaches and parameters, such as predictions of magma ascent rates in kimberlite dykes.  相似文献   

DEVELOPMENTS IN PHOTOGRAPHIC LENSES     

S. F. Ray 《The Photogrammetric Record》1994,14(83):713-728

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Tectonic Speleogenesis of Devils Hole, Nevada, and Implications for Hydrogeology and the Development of Long, Continuous Paleoenvironmental Records     

Alan C. Riggs  W. J. Carr  Peter T. Kolesar  Ray J. Hoffman 《Quaternary Research》1994,42(3)

Devils Hole, in southern Nevada, is a surface collapse into a deep, planar, steeply dipping fault-controlled fissure in Cambrian limestone and dolostone. The collapse intersects the water table about 15 m below land surface and the fissure extends at least 130 m deeper. Below water, most of the fissure is lined with a >30-cm-thick layer of dense maxillary calcite that precipitated continuously from groundwater for >500,000 yr. The thick mammillary calcite coat implies a long history of calcite-supersaturated groundwaters, which, combined with the absence of dissolutional morphologies, suggests that Devils Hole was not formed by karst processes. Devils Hole is located in a region of active extension; its tectonic origin is shown by evidence of spreading of its planar opening along a fault and by the orientation of its opening and others nearby, perpendicular to the northwest-southeast minimum principal stress direction of the region. Most Quaternary tectonic activity in the area, including seismicity and Quaternary faults and fractures, occurs on or parallel to northeast-striking structures. The hydrogeologic implications of this primarily structural origin are that fracture networks and caves opened by extensional tectonism can act as groundwater flowpaths functionally similar to those developed by karst processes and that, during active extension, transmissivity can be maintained despite infilling by mineral precipitation. Such extensional environments can provide conditions favorable for accumulation of deposits preserving long, continuous paleoenvironmental records. The precipitates in Devils Hole store chronologies of flow system water-level fluctuations, hydrochemistry, a half-million-yr proxy paleoclimate record, evidence of Devils Hole's tectonic origin, and probably atmospheric circulation.  相似文献   

Surface drag contribution to the depth of monsoon depression over Indian region     

Dr. S. P. Ray 《Meteorology and Atmospheric Physics》1982,31(3):237-241

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The Barnacle,Balanus subalbidus,as a salinity bioindicator in the Oligohaline Estuarine Zone     

Michael A. Poirrier  Mickel Ray Partridge 《Estuaries and Coasts》1979,2(3):204-206

The distribution and size of the barnacle Balanus subalbidus were studies along salinity gradients in coastal Louisiana and Mississippi. It was common in gradient estuaries occurring in salinities ranging from near fresh water to 16 ppt. It was the dominant barnacle species in the oligohaline zone, but at salinities above 6 ppt its relative abundance decreased and it was replaced by B. improvicus and B. eburneus. Its low-salinity limit corresponded to the boundary between the oligohaline and fresh water estuarine salinity zones and there was a high negative correlation between size (basal rostral-carinal diameter) and salinity. Its size and distribution could be used to determine prevailing salinity at a site because of its abundance and uniform distribution in oligohaline areas.  相似文献   

The inner city: In search of the problem     

Ray Forrest  John Lloyd  Nick Rogers  Peter Williams 《Geoforum》1979,10(1):109-116

This paper explores the theoretical content of the inner-city debate in Britain and seeks to examine the extent to which the ‘problem’ is either new or primarily economic. It is argued that the inner-city issue, while subject to specific political and ideological forces, is associated with the general processes of uneven capitalist development. In this sense, metropolitan decline is a further manifestation of the relationship between the built environment, the transience of economic activity and social change. More specifically the decline of the inner city relates to the incipient role of Britain in the development of capitalism and its current position in the world economy. The emergence of this as a ‘problem’ for the British state is combined with a convenient spatial determinism, which isolates the inner city as an anomaly even as the search for palliatives is erected to the status of a major social task.  相似文献   

Age of the last major scabland flood of the Columbia Plateau in eastern Washington     

Donal R. Mullineaux  Ray E. Wilcox  Walter F. Ebaugh  Roald Fryxell  Meyer Rubin 《Quaternary Research》1978,10(2):171-180

Pumice layers of set S from Mount St. Helens can be correlated with certain ash beds associated with young flood deposits of the channeled scabland. The correlation points to an age of about 13,000 ¹⁴C yr B.P. for the last major flood to have crossed the scabland. Until recently, the last major episode of flooding was thought to be closer to 20,000 yr B.P., an age inferred chiefly from the relation of the flood to glacial events of the northern Rocky Mountains. Several investigations within the last few years have suggested that the last major flood occurred well after 20,000 yr B.P. Tentative correlations of ash beds of the scabland with set S pumice layers, the relations of flood and glacial events along the northwestern margin of the Columbia Plateau, and a radiocarbon date from the Snake River drainage southeast of the plateau all indicate an age much younger than 20,000 yr. The postulated age of about 13,000 yr B.P. is further supported by a radiocarbon date in the Columbia River valley downstream from the scabland tract. Basal peat from a bog on the Portland delta of Bretz, which is a downvalley deposit of the last major scabland flood, has been dated as 13,080 ± 300 yr B.P. (W-3404).  相似文献   

Structural evolution of the Simla klippe in the lower Himalayas     

K. Naha  S. K. Ray 《International Journal of Earth Sciences》1972,61(3):1050-1086

The rocks of the Jutogh Series in the Simla area have been involved in folding of three generations and metamorphism in two phases. The earliest structures are isoclinal, recumbent/reclined folds (F₁) with a shallow plunge toward east or west where least reoriented. The axial surfaces of these folds have been folded coaxially into open, upright antiforms and synforms (F₂), which become tight to isoclinal in the northern part, causing local involution. The F₁ and F₂ folds have been affected by conjugate and chevron folding (F₃) with an overall NS strike of axial planes, resulting in axial culminations and depressions of the early folds. Axial plane foliation related to F₁ folding and transposition schistosities parallel to the axial planes of the F₂ and F₃ folds are the planar deformation structures that have developed. Cross stratification at one contact of two rock-units suggests that the structure of the Jutogh Series in the largest scale is a recumbent syncline, the peaks of Taradevi, Jutogh and Prospect Hill representing the inverted limb.The Jutogh rocks are surrounded and structurally underlain by the rocks of the Chail Series. The open, synformal nature of the Jutogh-Chail boundary in contrast with the complex fold-geometry within the Jutogh Series, tearing-off of the largescale early folds and sharp break in the first metamorphism at the Jutogh-Chail contact, and widespread cataclasis all along the border prove that the Jutogh Series has been thrust over the Chail Series forming a klippe in the Simla area. Continuation of the second metamorphism and the third folding across the Jutogh thrust indicates that the thrusting preceded F₃ and was broadly coeval with the F₂ movement.An unrestricted southward transport could generate the F₁ recumbent folds. The F₂ folds point to a flattening in the waning phase of the overthrust movement in broadly the same plan of deformation. The F₃ folds indicate a compression in an EW direction in the last phase of deformation.

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Zusammenfassung Die Gesteine der Jutogh-Serie im Gebiet von Simla wurden von drei Faltungs- und zwei Metamorphosephasen betroffen. Die ältesten Strukturen sind isoklinale, liegende bis geneigte Falten (F₁) mit flachem Achsentauchen nach E oder W in den am wenigsten überprägten Bereichen. Die Achsenflächen dieser Falten wurden koaxial zu offenen, aufrechten Anti- und Synformen verbogen (F₂). Im nördlichen Teil werden diese eng bis isoklinal, was zu lokaler Involution führt. Die F₂- und F₂-Falten wurden durch paarige Knicksowie Zickzackfalten (F₃) mit generell N-S-streichenden Achsenflächen überprägt, wodurch in den älteren Falten Achsenkulminationen und -depressionen entstanden. An den Achsenflächen von F₁ ausgerichtete Spaltbarkeit und Umformungsschieferang parallel zu den Achsenflächen von F₂ und F₃ haben sich als planare Deformationsstrukturen entwickelt. Aus der Schrägschichtung am Kontakt zweier Gesteinseinheiten ist zu schließen, daß die Jutogh-Serie im ganzen eine liegende Synklinale bildet. Die Gipfel von Taradevi, Jutogh und Prospect Hill liegen in deren überlapptem Schenkel.Gesteine der Chail-Serie umgeben und unterlagern die Jutogh-Gesteine. Die offene, synformale Grenze zwischen Jutogh und Chail im Gegensatz zu der komplexen Faltengeometrie innerhalb der Jutogh-Serie, das Abreißen großmaßstäblicher alter Falten sowie das scharfe Absetzen der ersten Metamorphosephase am Jutogh-Chail-Kontakt und die verbreitete Kataklase überall an der Grenze beweisen, daß die Jutogh-Serie auf die Chail-Serie überschoben wurde und im Gebiet von Simla eine Klippe bildet. Die Auswirkungen der zweiten Metamorphosephase und der dritten Faltung über die Basis des Jutogh hinweg zeigen an, daß die Überschiebung vor F₃ und annähernd gleichzeitig mit den F₂-Bewegungen einzustufen ist.Die liegenden F₁-Falten konnten durch eine unbehinderte Verschiebung nach Süden entstehen. Die F₂-Falten weisen auf eine Pressung in der Spätphase der Überschiebungsbewegungen mit etwa gleichem Deformationsplan hin. Die F₃-Falten zeigen einen ost-westlichen Zusammenschub während der letzten Deformationsphase an.

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Résumé Les roches de la série Jutogh dans la région de Simla ont subi trois phases de plissement et deux phases de métamorphisme. Les plus anciennes structures sont des plis isoclinaux couchés à déversés (F₁), à faible plongement d'axe vers l'E et l'W dans les parties les moins remaniées. Les surfaces axiales de ces plis ont été reployés suivant les mêmes axes en plis antiformes et synformes, droits et ouverts (F₂). Dans la partie N, ces derniers se resserrent jusqu'à devenir isoclinaux, ce qui conduit à des involutions locales. Les plissements F₁ et F₂ sont remaniés par des plis en chevrons ou en zigzag (F₃) à surface axiale de direction Nord-Sud; il naît de la sorte dans les plis anciens des culminations et des dépressions d'axes. Une fissilité suivant les surfaces axiales de F₁ et une schistosité parallèle aux surfaces axiales de F₂ et F₃ se sont développées en tant que structures planaires de déformation. La stratification entrecroisée au contact des unités lithologiques permet de dire que la Série de Jutogh dans son ensemble constitue un synclinal couché. Les sommets Taradevi, Jutogh et Prospect Hill se trouvent sur le flanc renversé.Les roches de la Série de Chail entourent et forment le substratum des roches de Jutogh. L'allure synforme et ouverte dessinée par la limite entre les Séries de Jutogh et de Chail opposée à la géométrie plissée complexe de l'intérieur de la Série de Jutogh, l'étirement à grande échelle des plis anciens comme aussi la diminution nette de la première phase de métamorphisme au contact Jutogh-Chail et la cataclase générale à leur limite, démontrent que la série de Jutogh a été charriée sur la série de Chail et qu'elle forme un lambeau dans la région de Simla. Les effets de la 2ème phase de métamorphisme et du troisième plissement à partir de la base de la série de Jutogh montrent que le charriage est intervenu avant les mouvements F₃ et à peu près en même temps que les mouvements F₂.Les plis couchés F₁ purent se produire grâce à une poussée sans opposition vers le Sud. Les plis F₂ indiquent un écaillage au cours de la phase tardive des mouvements de charriage suivant le même plan de la déformation. Les plis F₃ montrent une compression Est-Ouest pendant la dernière phase de déformation.

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Jutogh Simla 3 2 . —, , (F₁) E, W . (F₂). , , . F₁ F₂ , (F₃), N-S , . , F₁ F₂ F₃, . , Jutogh . Taradevi, Jutogh Prospect Hill . Chail Jutogh. Jutogh Chail Jutogh, Jutogh/Chail , Jutogh Chail Simla Klippe. Jutogh , , F₃, , F₂. F₁ . F₂ . F₃ , - .

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