Statistical and dynamical long-range atmospheric forecasts: experimental comparison and hybridization     

JÉRÔME SARDA  GUY PLAUT  CARLOS PIRES  ROBERT VAUTARD 《地球，A辑:动力气象学与海洋学》1996,48(4):518-537

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Back to the future: reflections and directions of South African marine bioinvasion research     

ME Alexander  CA Simon  CL Griffiths  K Peters  S Sibanda  S Miza 《African Journal of Marine Science》2016,38(1):141-144

Biological invasions continue to increase around the world, with impacts on many coastal marine systems. Here we review the South African marine invasion literature which, despite the field being relatively new, has grown to have significant presence in both the local and international arenas. Of the 79 papers reviewed, 70% focused on the establishment and spread of alien species, with modes of transport and introduction largely overlooked. An emphasis was also apparent towards field studies, in particular survey work, with few experimental studies. The overwhelming majority of papers focused on a single species, the Mediterranean mussel Mytilus galloprovincialis, reflecting the scale of this invasion and the tractable nature of rocky shores as study systems. With the exception of this one species, the impacts of marine alien species have rarely been quantified. We suggest that future research extends the taxonomic coverage of present work and develops a better understanding of the mechanisms of introduction, establishment and spread of marine alien species. Through an experimental approach, the drivers of altered ecological patterns and processes resulting from invasions should be addressed, providing insight into associated impacts. This approach will maintain the local applicability and international relevance of South African marine invasion research.  相似文献   

星载激光光斑影像激光指向变化探测法     

杨雄丹  李国元  王佩贤  陈继溢  莫凡  么嘉棋  金泽林 《测绘学报》1957,49(12):1591-1599

地面光斑足印的定位精度高度依赖于激光指向角的测量精度,星载激光光斑质心提取及其变化规律对激光指向角的分析具有重要的意义。本文基于ICESat/GLAS的激光剖面阵列（laser profile array,LPA）影像数据,首先利用灰度一阶矩阵法提取LPA的质心,精度优于0.3个像素,LPA相对定位精度优于0.11个像素。其次利用傅里叶变换和傅里叶级数拟合对LPA质心坐标的变化进行周期探测和建模分析,结果表明,激光光斑影像的质心坐标存在1.83×10^-4 Hz、3.36×10^-4 Hz、5.19×10^-4 Hz和6.71×10^-4 Hz 4个明显的周期变化,拟合结果的相关性R²达到了0.86,拟合精度可达0.4″,优于0.13个像素,得到了较好的结果。可为我国的高分七号和后续的卫星激光测高数据处理提供参考。  相似文献   

Periodicity in namurian sediments of derbyshire,england (a quantitative sedimentary analysis)     

Richard A. Reyment  John D. Collinson 《Sedimentary Geology》1971

Five facies associations are present in the basin-filling Namurian sediments (Grindslow Shales and Kinderscout Grit) of the southern Central Pennine Basin of England. Visual study of sequences fails to disclose any pattern in the occurrence of facies. A simple mathematical statistical analysis shows that patterns do occur and approximate models can be proposed. The homogeneous siltstones (facies A) occur roughly in accord with a Poisson process model; the striped siltstones (facies B) of the sequence deviate from a renewal process model in many ways and may be most nearly approximated by some process showing trend in the rate of occurrence of events; the sharp-based sandstones (facies C) seem to occur in agreement with some type of renewal process, but not a Poissonian variety. The intervals between the sediment-building periods of these facies categories may be renewal processes of some kind, although all deviate from a simple Poisson model. Owing to the limitations of the data available only tentative conclusions can be drawn.  相似文献   

Ferrous and Ferric Iron in Red Sediments and Their Magnetic Properties     

D. W. Collinson 《Geophysical Journal International》1968,16(5):531-542

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Saldanha Bay,South Africa I: the use of ocean colour remote sensing to assess phytoplankton biomass     

ME Smith  GC Pitcher 《African Journal of Marine Science》2015,37(4):503-512

The efficacy of ocean colour remote sensing in assessing the variability of phytoplankton biomass within Saldanha Bay is examined. Satellite estimates of chlorophyll a (Chl a) were obtained using the maximum peak-height (MPH) algorithm on full-resolution (300?m) data from the Medium Resolution Imaging Spectrometer (MERIS). Subsurface Chl a maxima often occur within Saldanha Bay below the mean detection depth of the satellite (1.5?m) during periods of thermal stratification. Consequently, the MPH product was poorly correlated to in situ data from 4?m depth (r² and average relative percentage difference [RPD] of 0.094 and 53% respectively); however, the coefficient of determination was much improved if limited to in situ data collected under conditions of mixing (r² and RPD of 0.869 and 89%, respectively). Composites of monthly MPH Chl a data reveal mean concentrations consistent with in situ seasonal trends of phytoplankton biomass, confirming the capability of the MPH algorithm to qualitatively resolve surface Chl a distribution within the bay.  相似文献   

Magnetic properties of the Estherville mesosiderite     

D. W. Collinson 《Meteoritics & planetary science》1991,26(1):1-10

Abstract— Evolutionary processes in meteorites and magnetic fields in the early solar system, both spatial and localised in planetary bodies, can leave their imprint in meteorites through the natural remanent magnetization (NRM) and other magnetic properties they impart to them. In the present investigation the Estherville mesosiderite has been studied to enquire whether its magnetic properties can help to resolve any of the uncertainties associated with mesosiderite history and evolution, and to examine evidence for any magnetic fields to which it or its constituent fragments have been subjected. The Estherville sample as received is strongly magnetized, with an initial NRM intensity of 1.4 × 10^?3 Am² kg^?1. The NRM of individual fragments broken from the main mass, when referred to common reference axes, is scattered in direction on a scale which ranges from ～ 1 cm down to ～ 1 mm. Alternating field and thermal demagnetization show a range of magnetic stability among the samples and also some secondary NRM, indicating a variety of magnetic histories. Thermomagnetic analyses of matrix and iron-nickel separates show that the dominant magnetic carriers are kamacite and tetrataenite. The non-coherent directions of NRM within the matrix imply the acquisition of an initial NRM by kamacite in the fragments prior to their final accumulation into the mesosiderite material, and the presence of an ambient magnetic field when the fragment material cooled after its formation. If the tetrataenite carrying the primary NRM was formed from the previously magnetized kamacite/taenite during slow cooling after later metamorphic heating, the maximum temperature during the latter event could not have been higher than ～700 °C or the kamacite would have been remagnetized uniformly or demagnetized, according to whether or nor there was an ambient magnetic field present. Susceptibility anisotropy observations indicate the acquisition of anisotropic properties occurred before final accumulation of the meteorite. Shock and flow processes were probably important in producing foliation and lineation respectively in the fragments resulting from brecciation, and there could also be a contribution from larger metal fragments and/or veins. The scattered NRM of the iron-nickel fragments also indicates magnetization prior to emplacement, therefore favouring introduction in the solid rather than the molten form.  相似文献   

Early fill of the Western Irish Namurian Basin: a complex relationship between turbidites and deltas   总被引：1，自引：0，他引：1  

John D. Collinson  Ole Martinsen  Bente Bakken  Anne Kloster 《Basin Research》1991,3(4):223-242

The Western Irish Namurian Basin developed in Early Carboniferous times as a result of extension across the Shannon Lineament which probably coincides with the lapetus Suture. During the late Dinantian, axial areas of the NE-SW elongate trough became deep, whilst shallow-water limestones were deposited on the flanks. This bathymetry persisted into the Namurian when carbonate deposition ceased. In axial areas, a relatively thick mudstone succession spans earliest Namurian to Chokierian whilst on the northwestern marginal shelf, a thin, condensed Namurian mudstone sequence, in which pre-Chokierian sediments are apparently absent, rests unconformably on the Dinantian. From late Chokierian to early Kinderscoutian, the basin was filled by sand-dominated clastic sediments. Sand deposition began in the axial area with deposition of a thick turbidite sequence, the Ross Formation, which is largely equivalent to the condensed mudstone succession on the flanks. Turbidity currents flowed mainly axially towards the north-east and deposited a sequence lacking well-defined patterns of vertical bed-thickness change. Channels and slide sheets occur towards the top of the formation. The turbidite system seems to have lacked well-defined lobes and stable distributary channels. Overlying the Ross Formation, the Gull Island Formation shows a decreasing incidence of turbidite sandstones at the expense of increasing siltstones. This formation is characterized by major slides and slumps interbedded with undisturbed strata. In the flanking areas of the basin, the formation is thinner, has only a few turbidites in the sequence above the condensed mudstones and contains only one slide sheet. Overall the formation is interpreted as the deposit of a major prograding slope, the lower part representing a ramp upon which turbidites were deposited, the upper part a highly unstable muddy slope lacking any conspicuous feeder channels through which sand might have been transferred to deeper water. Progradation of the slope appears to have been increasingly from the northwestern flank of the trough which is similar to the direction deduced for the overlying deltaic Tullig cyclothem which completes the initial basin fill. Whilst several features of the succession can be explained by envisaging the whole sequence as the product of one linked depositional system, the shifting directions of palaeocurrents and palaeoslope raise problems. The switch from axial to lateral supply casts doubt on the strict application of Walther's Law to the total sequence and seems to demand large avulsive shifts of the delta system on the shelf area to the west.  相似文献   

Experiments relating to the measurement of inhomogeneous remanent magnetism in rock samples     

D. W. Collinson 《Geophysical Journal International》1977,48(2):271-275

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Origin of Remanent Magnetization and Initial Susceptibility of Certain Red Sandstones     

D. W. Collinson 《Geophysical Journal International》1965,9(2-3):203-217

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