A laboratory study of baroclinic instability     

J. E. Hart 《地球物理与天体物理流体动力学》2013,107(1):181-209

Abstract

Experimental and theoretical results are presented for a simple system which exhibits baroclinic instability. We consider the motion of two immiscible fluids with densities ρ ₁ and ρ ₂ contained in a cylinder rotating with angular frequency ω. The motion is driven by a contact lid rotating with frequency ω + ω. In this paper ω, ω, 2(ρ ₂ – ρ ₁)/(ρ ₂ + ρ ₁), and the geometry are such that the interface does not intersect the “ground” (e.g. an almost horizontal boundary). The motions are described by two-layer quasi-geostrophic equations which are identical, except perhaps for the presence of interfacial friction and tension, with those used in meteorology and oceanography. For small enough internal Froude number F = 4ω² L ²/(g(Δρ/ρ)H) or small enough Rossby number ? = ω/2ω the flow is steady and axisymmetric, the velocity field in each layer being determined primarily by frictional effects in top, bottom, and interfacial Ekman layers. For certain (F, ?) the flow becomes non-axisymmetric. The transition points for the case where the basic potential vorticity gradient is due to interface slope alone have been carefully measured and are in very good agreement with a linear instability theory which neglects sidewall effects. Some preliminary observations of supercritical motion, which include repeatable amplitude and wavenumber vacillation, are reported.  相似文献   

On Robust Multi-Year Tidal Prediction Using T_TIDE     

Byun  Do-Seong  Hart  Deirdre Erin 《Ocean Science Journal》2019,54(4):657-671

Ocean Science Journal - A minimum 19 year tidal prediction dataset covering nodal (satellite) modulation effects is required to determine the Lowest Astronomical Tide (LAT) and Highest Astronomical...  相似文献   

The Wide Field Spectrograph (WiFeS)     

Michael Dopita  John Hart  Peter McGregor  Patrick Oates  Gabe Bloxham  Damien Jones 《Astrophysics and Space Science》2007,310(3-4):255-268

This paper describes the Wide Field Spectrograph (WiFeS) under construction at the Research School of Astronomy and Astrophysics (RSAA) of the Australian National University (ANU) for the ANU 2.3 m telescope at the Siding Spring Observatory. WiFeS is a powerful integral field, double-beam, concentric, image-slicing spectrograph designed to deliver excellent throughput, wavelength stability, spectrophotometric performance and superb image quality along with wide spectral coverage throughout the 320–950 nm wavelength region. It provides a 25×38 arcsec field with 0.5 arcsec sampling along each of twenty five 38×1 arcsec slitlets. The output format is optimized to match the 4096×4096 pixel CCD detectors in each of two cameras individually optimized for the blue and the red ends of the spectrum, respectively. A process of “interleaved nod-and-shuffle” will be applied to permit quantum noise-limited sky subtraction. Using VPH gratings, spectral resolutions of 3000 and 7000 are provided. The full spectral range is covered in a single exposure at R=3000, and in two exposures in the R=7000 mode. The use of transmissive coated optics, VPH gratings and optimized mirror coatings ensures a throughput (including telescope atmosphere and detector) >30% over a wide spectral range. The concentric image-slicer design ensures an excellent and uniform image quality across the full field. To maximize scientific return, the whole instrument is configured for remote observing, pipeline data reduction, and the accumulation of calibration image libraries.  相似文献   

Statoliths     

Malcolm B. Hart 《Geology Today》2019,35(3):115-118

Statoliths, in modern cephalopods, are the paired calcareous ‘stones’ that lie in two adjacent cavities (or statocysts) within the cartilage of the head. The stones are generally 0.5–2.0 mm in length and appear to be formed of aragonite. Statoliths often co‐occur with fish otoliths, and being of similar appearance, size, colour, etc., this has caused confusion in the past. It was only towards the latter part of the twentieth century that it was recognized that statoliths could occur as fossils.  相似文献   

Public support for carbon dioxide removal strategies: the role of tampering with nature perceptions     

Wolske  Kimberly S.  Raimi  Kaitlin T.  Campbell-Arvai  Victoria  Hart  P. Sol 《Climatic change》2019,152(3-4):345-361

Climatic Change - Carbon dioxide removal (CDR) describes a suite of controversial approaches to mitigating climate change that involve removing existing carbon dioxide from the atmosphere. Through...  相似文献   

Variation of Mo isotopes from molybdenite in high-temperature hydrothermal ore deposits   总被引：1，自引：0，他引：1  

Ryan Mathur  S. Brantley  A. Anbar  F. Munizaga  V. Maksaev  R. Newberry  J. Vervoort  G. Hart 《Mineralium Deposita》2010,45(1):43-50

Measurable molybdenum isotope fractionation in molybdenites from different ore deposits through time provides insights into ore genesis and a new technique to identify open-system behavior of Re–Os in molybdenites. Molybdenite samples from six porphyry copper deposits, one epithermal polymetallic vein deposit, four skarns, and three Fe-oxide Cu–Au deposits were analyzed. The δ⁹⁷Mo‰ (where ) for all samples varied from 1.34 ± 0.09‰ to −0.26 ± 0.04‰. This is the largest molybdenum isotopic variation in molybdenite from high-temperature ore deposits recorded to date. δ⁹⁷Mo‰ of molybdenite varies as a function of the deposit type and the rhenium and osmium concentrations of the samples. Isotope values for Mo also vary within the individual deposits. In general, molybdenites from porphyry copper deposits have the lightest values averaging 0.07 ± 0.23‰ (1σ). Molybdenites from the other deposit types average 0.49 ± 0.26‰ (1σ). The variations could be related to the fractionation of Mo into different mineral phases during the ore-forming processes. A comparison of the Mo isotope ratios and the Re–Os ages obtained from the same aliquot may possess a geochronological evaluation tool. Samples that yielded robust ages have different Mo isotopic compositions in comparison to samples that yielded geologically unreasonable ages. Another observed relationship between the Re–Os and Mo isotope data reveals a weak correspondence between Re concentration and Mo isotope composition. Molybdenites with higher concentrations of Re correspond to lighter Mo isotope values.  相似文献   

Dissolved and particulate trace metal fluxes through the central English Channel, and the influence of coastal gyres     

P. J. Statham  S. Leclercq  V. Hart  M. Batt  Y. Auger  M. Wartel  J. Cheftel 《Continental Shelf Research》1999,19(15-16)

Measurements of dissolved Cd, Co, Cu, Mn, Ni, Pb, and Zn have been made on a seasonal basis at five stations on a north–south transect across the central English Channel between Cherbourg and the Isle of Wight. Vertical and horizontal distributions of dissolved Cd, Pb, Cu and Zn are relatively uniform except for sampling sites near the English coast. Dissolved Mn and Co show increased concentrations in the English coastal waters, and for Mn the seasonal trend in concentration follows the pattern seen in the Strait of Dover with higher values in the late summer. Ni and Cu are higher in concentration on the English side, which reflects mainly riverine sources. Measurements were also made of particulate forms of the metals above plus particulate Al, Ca, Fe, Mg, Sr and Ti. Water column concentrations of particulate metals broadly follow the distribution of suspended particulate matter, with highest concentrations near the UK coast. Trace metal concentrations have been integrated with modelled data on fluxes of water to provide estimates of fluxes for these elements into the eastern Channel, and an initial comparison is made with data for fluxes of metals through the Strait of Dover obtained during an earlier study. A major influence on the fluxes of particulate metals through the Isle of Wight-Cherbourg transect is the gyre system to the South east to the Isle of Wight, which has important east to west as well as west to east transport components. For those elements where the dissolved form of the metal dominates, the large flow of water in the central Channel waters leads to major fluxes of the metals towards the east and the Strait of Dover. However, the high suspended particulate matter loadings in the coastal waters and impact of the gyre system lead to net east to west fluxes of particulate Al, Fe, Mn and Ti. Comparison of these fluxes with data on the net west to east transport of these materials through the Strait of Dover infers that there must be a significant supply of these particulate metals to the eastern Channel.  相似文献   

Geoffrey Boulton     

James Rose  Jane K. Hart 《Quaternary Science Reviews》2009,28(7-8):580-583

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Mapping geochemical singularity using multifractal analysis: Application to anomaly definition on stream sediments data from Funin Sheet,Yunnan, China     

Jian Bai  Alok Porwal  Craig Hart  Arianne Ford  Le Yu 《Journal of Geochemical Exploration》2010,104(1-2):1-11

Most conventional statistical methods aiming at defining geochemical concentration thresholds for separating anomalies from background have limited effectiveness in areas with complex geological settings. This paper uses multifractal analysis to combine the characteristics of geochemical frequency distribution and spatial dispersion in order to map geochemical singularities instead of using conventional statistically derived concentration thresholds. The model, termed radius–areal Productivity (r–P) model, employs a stable measure and a scale-increasing method to estimate geochemical singularities spatially on geochemical landscape for delineating potential anomalies. The model is applied to geochemical data of regional stream sediments from the Funin Sheet, Yunnan, China.  相似文献   

Experimental cpx/melt partitioning of 24 trace elements   总被引：46，自引：13，他引：46  

Stanley R. Hart  Todd Dunn 《Contributions to Mineralogy and Petrology》1993,113(1):1-8

Cpx/melt partition coefficients have been determined by ion probe for 24 trace elements at natural levels in an alkali basalt experimentally equilibrated at 1,380°C and 3 GPa. One goal was to intercompare Ds for both high-field-strength elements and rare earth elements (REE) in a single experiment. Relative to the REE spidergram, Hf and Ti show virtually no anomaly, whereas Zr exhibits a major negative anomaly. Other incompatible elements (Ba, K, Nb) fall in the range of published values, as do elements such as Sr, Y, Sc, Cr and V. Pb shows a value intermediate between La and Ce. Values for Be, Li and Ga are reported for the first time, and show that Be is as incompatible as the light REEs whereas Li and Ga are somewhat more compatible than the heavy REE.  相似文献