Correlation methods in fingerprint detection studies   总被引：2，自引：0，他引：2  

B D Santer  T M L Wigley  P D Jones 《Climate Dynamics》1993,8(6):265-276

This investigation addresses two general issues regarding the role of pattern similarity statistics in greenhouse warming detection studies: normalization, and the relative merits of centered versus uncentered statistics. A pattern correlation statistic is used to search for the greenhouse warming signals predicted by five different models in the observed records of land and ocean surface temperature changes. Two forms of this statistic were computed: R (t), which makes use of nonnormalized data, and (t), which employs point-wise normalized data in order to focus the search on regions where the signal-to-noise ratio is large. While there are no trends in the R (t) time series, the time series of (t) show large positive trends. However, it is not possible to infer from the (t) results that the observed pattern of temperature change is, in fact, becoming increasingly similar to the model-predicted signal. This is because point-wise normalization of the observed and simulated mean change fields by a single common field introduces a common factor effect, which means that the quantities being compared should show some similarity a priori. This does not necessarily make normalization inapplicable, because the detection test involves seeking a trend in the similarity statistic. We show, however, that trends in (t) must arise almost completely from the observed data, and cannot be an indicator of increasing observed data/signal similarity. We also compare the information provided by centered statistics such as R(t) and the uncentered C(t) statistic introduced by Barnett. We show that C(t) may be expressed as the weighted sum of two terms, one proportional to R(t) and the other proportional to the observed spatial mean. For near-surface temperatures, the spatial average term dominates over the R(t) term. In this case the use of C(t) is equivalent to the use of spatial-mean temperature. We conclude that at present, the most informative pattern correlation statistic for detection purposes is R(t), the standard product-moment correlation coefficient between the observed and model fields. Our failure to find meaningful trends in R(t) may be due to the fact that the signal is being obscured by the background noise of natural variability, and/or because of incorrect model signals or sensitivities.  相似文献   

Coupling an ocean wave model to an atmospheric general circulation model     

Susanne L Weber  Hans von Storch  Pedro Viterbo  Liana Zambresky 《Climate Dynamics》1993,9(2):63-69

A coupled model, consisting of an ocean wave model and an atmospheric general circulation model (AGCM), is integrated under permanent July conditions. The wave model is forced by the AGCM wind stress, whereas the wind waves modify the AGCM surface fluxes of momentum, sensible and latent heat. We investigate the following aspects of the coupled model: how realistic are the wave fields, how strong is the coupling, and how sensitive is the atmospheric circulation to the spatially and temporally varying wave field. The wave climatology of the coupled model compares favorably with observational data. The interaction between the two models is largest (although weak) in the storm track in the Southern Hemisphere. Young windsea, which is associated with enhanced surface fluxes is generated mostly in the equatorward frontal area of an individual cyclone. However, the enhancement of the surface fluxes is too small to significantly modify the climatological mean atmospheric circulation.This paper was presented at the Second International Conference on Modelling of Global Climate Variability, held in Hamburg 7–11 September 1992 under the auspices of the Max Planck Institute for Meteorology. Guest Editor for these papers is L. Dümenil  相似文献   

Experimental investigation and application of the equilibrium rutile + orthopyroxene = quartz + ilmenite     

Jodie L. Hayob  Steven R. Bohlen  Eric J. Essene 《Contributions to Mineralogy and Petrology》1993,115(1):18-35

Equilibria in the Sirf (Silica-Ilmenite-Rutile-Ferrosilite) system: $${\text{SiO}}_{\text{2}} + ({\text{Mg,Fe}}){\text{TiO}}_{\text{3}} {\text{ + (Mg,Fe)SiO}}_{\text{3}} $$ have been calibrated in the range 800–1100° C and 12–26 kbar using a piston-cylinder apparatus to assess the potential of the equilibria for geobarometry in granulite facies assemblages that lack garnet. Thermodynamic calculations indicate that the two end-member equilibria involving quartz + geikielite = rutile + enstatite, and quartz + ilmenite = rutile + ferrosilite, are metastable. We therefore reversed equilibria over the compositional range Fs_40–70, using Ag₈₀Pd₂₀ capsules with \(f_{{\text{O}}_{\text{2}} } \) buffered at or near iron-wüstite. Ilmenite compositions coexisting with orthopyroxene are \(X_{{\text{MgTiO}}_{\text{3}} }^{{\text{Ilm}}} \) of 0.06 to 0.15 and \(X_{{\text{Fe}}_{\text{2}} {\text{O}}_{\text{3}} }^{{\text{Ilm}}} \) of 0.00 to 0.01, corresponding toK _D values of 13.3, 10.2, 9.0 and 8.0 (±0.5) at 800, 900, 1000 and 1100° C, respectively, whereK _D =(XMg/XFe)^Opx/(XMg/XFe)^Ilm. Pressures have been calculated using equilibria in the Sirf system for granulites from the Grenville Province of Ontario and for granulite facies xenoliths from central Mexico. Pressures are consistent with other well-calibrated geobarometers for orthopyroxeneilmenite pairs from two Mexican samples in which oxide textures appear to represent equilibrium. Geologically unreasonable pressures are obtained, however, where oxide textures are complex. Application of data from this study on the equilibrium distribution of iron and magnesium between ilmenite and orthopyroxene suggests that some ilmenite in deep crustal xenoliths is not equilibrated with coexisting pyroxene, while assemblages from exposed granulite terranes have reequilibrated during retrogression. The Sirf equilibria are sensitive to small changes in composition and may be used for determination of activity/composition (a/X) relations of orthopyroxene if an ilmenite model is specified. A symmetric regular solution model has been used for orthopyroxene in conjunction with activity models for ilmenite available from the literature to calculatea/X relations in orthopyroxene of intermediate composition. Data from this study indicate that FeSiO₃?MgSiO₃ orthopyroxene exhibits small, positive deviations from ideality over the range 800–1100°C.  相似文献   

Stratiform and vein U,Mo and Cu mineralization in the Novoveská Huta area,CSFR     

I. Rojkovič  L. Novotny  M. Háber 《Mineralium Deposita》1993,28(1):58-65

U-Mo and Cu mineralization occurs in horizons as well as in veins in the Permian formations near Novoveská Huta. Ore mineralization is represented by uraninite, U-Ti oxides, coffinite, molybdenite, chalcopyrite, tennantite and pyrite. The isotopic composition of S and C displays a larger variability in the stratiform ores (³⁴S from –32.7 to +2.7 and ¹³C from –27.1 to — 0.5) These data suggest mixing of meteoric solutions with fluids of volcanic origin and a complex history. There is a narrower range of ³⁴S from –18.8 to –4.6 and ¹³C from –6.3 to –2.5% in quartz-carbonate veins with Cu mineralization suggesting a deep source of ore-bearing solutions. The Permian volcanics were a significant source of ore elements.Their contents of U, Mo, Cu and Y are from two to eight times higher than in sedimentary rocks. Accumulations of ore elements in the horizons were formed by the reduction and adsorption processes 240 ± 30 Ma ago according to U-Pb isotopic dating. Due to Alpine tectonism, these low-grade ores (U<0.1 wt%) were remobilized and higher-grade U-Mo ores (U>0.1 wt%) were formed 130 ± 20 Ma ago at temperatures ranging from 110 to 120° C, according to fluid inclusions. Younger veins with Cu mineralization were formed 115 ± 10 Ma according to the model age of Pb at temperatures ranging from 95 to 190°C.  相似文献   

Recreation on public lands in New Zealand — past,present and future     

Kay L. Booth 《GeoJournal》1993,29(3):299-305

Since the turn of the century, recreation has grown as a motivating force in public land administration. Today, the Department of Conservation manages approximately one third of New Zealand's outdoor recreation resources and has the mandate to foster the use of natural and historic resources for recreation, and to allow their use for tourism (Conservation Act 1987:8). This paper traces the emergence of a recreation perspective within public land administration and examines the development of a recreation philosophy and policy within the Department of Conservation. It suggests future directions for outdoor recreation management in New Zealand.  相似文献   

Electron paramagnetic resonance of Sc3+-stabilized CO 3 3− molecule-ion in natural calcite     

R. M. Mineyeva  L. V. Bershov  A. V. Speranskiy 《Physics and Chemistry of Minerals》1993,20(2):136-140

Electron paramagnetic resonance (EPR) spectra of CO ₃ ^3– molecule-ions stabilized by Sc³⁺ in natural calcite were identified and studied at X-band frequencies and room temperature. The principal values of the g-tensor (g _xx= 1.9997, g _yy = 2.0030, g _zz = 1.9972) and the direction cosines of the g and A tensors for CO ₃ ^3– -Sc³⁺ center were found to be close to that for the well-known CO ₃ ^3– -Y³⁺ center. A quantitative comparison of different impurity contents in calcite samples and analysis of the intensities of forbidden transitions were used to identify Sc³⁺. An estimation of the unpaired electron spin density on the nuclei of paramagnetic centers confirms that both centers, CO ₃ ^3– -Sc³⁺ and CO ₃ ^3– -Y³⁺, have the same nature.  相似文献   

硅质碎屑砂岩中胶结物来源的新认识     

杨香华 《地质科技情报》1993,12(4):34-39

分析了浅埋藏砂岩的成岩环境,并从岩石学、矿物学、同位素及质量平衡估算方面论证硅质碎屑砂岩中的胶结物主要来源于砂岩浅埋藏期间的地下水,进而分析浅埋藏带内地下水的流动机制及早期胶结作用对晚期成岩作用的影响。  相似文献   

极性转换期间地球磁场形态学研究   总被引：3，自引：1，他引：2  

朱日祥  丁仲礼 《地球物理学报》1993,36(3):347-359

本文对采自中国黄土高原西峰（35.7°N,107.6°E）和段家坡（34.2°N,109.2°E）两个剖面中黄土层L8和古土壤层S8的1281块定向古地磁样品做了详细的岩石磁学和古地磁学研究.证实了Matuyama-Brunhes（M-B）极性转换带位于L8的中下部.提出了下列观点:1.M-B极性转换过程与地球磁场方向变化相联系的持续时间为3600-4500a,而与地球磁场强度变化相联系的持续时间则为8000-9000a,即强度变化存在“超前和滞后” 效应;2.M-B转换场的形态是由三次快速倒转和一次不成功的倒转构成,或者说,转换场具有快速变换极性的振荡特征;3.M-B转换过程中地球磁场并不是以轴对称的非偶极子场为主,而是偶极子场至少与非偶极子场相当;4.中国黄土-古土壤沉积物所含磁性矿物的主要成分是磁铁矿,它是研究极性转换期间地球磁场详细结构的良好物质.  相似文献   

Isotope and trace element evidence for three component mixing in the genesis of the North Luzon arc lavas (Philippines)   总被引：5，自引：0，他引：5  

F. McDermott  M. J. Defant  C. J. Hawkesworth  R. C. Maury  J. L. Joron 《Contributions to Mineralogy and Petrology》1993,113(1):9-23

Post-3Ma volcanics from the N Luzon arc exhibit systematic variations in ⁸⁷Sr/⁸⁶Sr (0.70327–0.70610), ¹⁴³Nd/¹⁴⁴Nd (0.51302–0.51229) and ²⁰⁸Pb^*/²⁰⁶Pb^* (0.981–1.035) along the arc over a distance of about 500 km. Sediments from the South China Sea west of the Manila Trench also exhibit striking latitudinal variations in radiogenic isotope ratios, and much of the isotopic range in the volcanics is attributed to variations in the sediment added to the mantle wedge during subduction. However, Pb-Pb isotope plots reveal that prior to subduction, the mantle end-member had high 8/4, and to a lesser extent high 7/4, similar to that in MORB from the Indian Ocean and the Philippine Sea Plate. Th isotope data on selected Holocene lavas indicate a source with unusually high Th/U ratios (4.5–5.5). Combined trace element and isotope data require that three end-members were implicated in the genesis of the N Luzon lavas: (1) a mantle wedge end-member with a Dupal-type Pb isotope signature, (2) a high LIL/HFS subduction component interpreted to be a slab-derived hydrous fluid, and (3) an isotopically enriched end-member which reflects bulk addition (<5%) of subducted S China Sea terrigenous sediment. The ⁸⁷Sr/⁸⁶Sr ratios in the volcanics show a restricted range compared with that in the sediments, and this contrasts with ¹⁴³Nd/¹⁴⁴Nd and ²⁰⁸Pb^*/²⁰⁶Pb^*, both of which have similar ranges in the volcanics and sediments. Such differences imply that whereas the isotope ratios of Nd, Pb and Th are dominated by the component from subducted sediment, those of Sr reflect a larger relative contribution from the slab-derived fluid.  相似文献   

Fractional crystallization and zoning in igneous feldspars: ideal water-buffered liquid fractionation lines and feldspar zoning paths     

William L. Brown 《Contributions to Mineralogy and Petrology》1993,113(1):115-125

Diagrams giving plagioclase and sanidine fractionation paths and liquid fractionation lines under conditions of ideal water-buffered fractional crystallization in the ternary feldspar system were constructed graphically using topological reasoning, and experimental data and calculated phase relationships from the literature. The liquidus lines and solidus or solvus paths are unique at constant P and a _{H 2}O. The composition of a liquid evolves with time and moves along a fractionation line by removal of successive crystal fractions, whereas the compositions of each of the crystal fractions lie on and define a solidus or solvus path. Most but not all such water-buffered lines and paths differ only slightly from those in which water is free to build up during crystallization and a _{H 2}O to increase, as in many rocks. Liquid compositions lying along liquidus fractionation lines are not normally preserved, unless erupted as aphyric lavas. The solidus or solvus paths may be preserved either as overgrowth zones in crystals (zoning paths) or as a series of crystal fractions in layered intrusions. The topologies of the lines and paths depend mainly on the nature of the two-feldspar boundary line separating the plagioclase and sanidine fields which is a function of P _{H 2}O or a _{H 2}O at constant P; increases in either progressively lower the liquidi and solidi and cause larger intersections of the solidi with the solvus. One-feldspar solidus paths at high P and a _{H 2}O are simple, whereas they are complex and may bend back on themselves at low P _{H 2}O or low a _{H 2}O at high P. Two-feldspar paths may be simultaneous (cotectic) or sequential (peritectic). The former are simple and do not meet at high P and a _{H 2}O, the critical solution line lying in the gap; they are complex and may bend back or overlap at low P _{H 2}O or low a _{H 2}O at high P, the position of the critical solution line being hard to determine. Liquids which have simultaneously fractionated two feldspars may fractionate only one towards the end, crystallization changing from subsolvus to hypersolvus. Sequential paths may involve overgrowth of an early feldspar by a later one, usually sanidine overgrowths on plagioclase, but plagioclase overgrowths on sanidine occur. These complexities explain in part the difficulties of unravelling the textural and compositional relationships of ternary feldspars in water-poor felsic igneous rocks (even in the absence of alteration or complex magma dynamics) and of trying to deduce phase relationships from natural occurrences of feldspars.C.R.P.G. contribution number 948  相似文献