Geometric consistency for regression model estimation and testing in climatology and meteorology

Abstract

The effects of outliers on linear regression are examined. The sensitivity of classical least‐squares (LS) procedures to outliers is shown to be associated with the geometric inconsistency between the data space and the analysis space. This is illustrated for both estimation and inference. A geometrically consistent procedure based on the Euclidean distance is proposed. This procedure involves the least absolute deviation (LAD) regression and a new permutation test for matched pairs (PTMP). Comparisons made with LS techniques demonstrate that the proposed procedure is more resistant to the existence of outliers in the data set and leads to more intuitive results. Applications and illustrations using meteorological and climatological data are also discussed.     

Applications of computer modeling to the study of the genesis of stratiform sulfide deposits

Stratiform sulfide deposits are considered to have formed at or near the discharge vents of submarine hydrothermal systems. Such deposits constitute an important source of zinc, lead, copper, silver, and gold. They are often divided on the basis of the dominant host-rock lithology into volcanogenic and sediment-hosted types. In terms of their economic base metal contents, volcanogenic deposits contain either Cu and Zn or Zn, Pb, and Cu, whereas sediment-hosted deposits usually contain predominantly Zn and Pb. Mathematical models of the chemical characteristics of stratiform sulfide deposits are based on a program (B)which allows the calculation of the equilibrium distribution of aqueous species in a hydrothermal solution. Program B is front-ended by Program A, which defines the components of the chemical system, and back-ended by Program C, which controls the mode of output of the calculated results. Programs A and C are tailored to the specific problem under investigation. Results of chemical modeling of the two chemically active zones of the hydrothermal system (1. the hydrothermal reservoir in which the ore-forming solutions are generated and, 2. the site of ore deposition)suggest explanations of various characteristics of stratiform sulfide deposits, and include

1. The consistency of the metal associations and metal ratios suggest that ore-forming hydrothermal solutions are saturated with respect to the major metals in the reservoir zone. The chemistry of the solutions is determined mainly by temperature and chemical equilibrium between the hydrothermal solution and the rock-forming minerals of the reservoir.
2. Metal associations and metal ratios corroborate isotopic and other evidence that volcanogenic deposits were formed from hotter hydrothermal systems (> 200°Capprox.)than sediment-hosted (< 200°Capprox.)Metal ratios suggest that the hydrothermal reservoirs were contained in mafic rocks (ferromagnesian-feldspar mineral assemblages)for the Cu-Zn association; in felsic rocks and/or sediments (feldspar-mica; clay mineral assemblages)for the Zn-Pb-Cu association: and in sediments (dominated by clay mineral assemblages)for the Zn-Pb association.
3. Chemical zonation patterns and ore textures characteristics of volcanogenic deposits are explained by rapid cooling of the hydrothermal solution immediately above its discharge vent.
4. Chemical zonation patterns and the fine laminations of sediment-hosted deposits are explained by the comparatively slow degeneration of hydrothermal solutions that have collected as a brine pool on the ocean floor.

     

Deformation and patterns of sedimentation,South San Clemente Basin,California Borderland

Seismic reflection profiling in the South San Clemente Basin and the southern portion of the San Diego Trough has revealed at least six sedimentary units exhibiting varying stages of deformation. Four of the units are interpreted to be marine turbidites supplied by adjacent submarine canyons. Sediments comprising the Descanso Plain and correlative material within the South San Clemente Basin are attributed to a southerly source (Banda Canyon), while the more recent Quaternary turbidites from Coronado Canyon filled the southern San Diego Trough and then spilled over into South San Clemente Basin. The relatively high but intermittent rates of sedimentation, together with shifting sources and areas of deposition, have resulted in sedimentary units that were emplaced in comparatively short episodes but which were subjected to relatively continuous tectonic activity. Consequently, the sedimentary layers of each unit appear uniformly affected by deformation which increases in successively older units.     

Seed biology of Australian arid zone species: Germination of 18 species used for rehabilitation

Revegetation of disturbed land, particularly in arid environments, is often hindered by low seedling establishment. Information on seed biology and germination cues of keystone species is lacking, particularly in arid Australia; a major zone for mining developments. This study investigated seed characteristics and germination of 18 common species required for rehabilitation of disturbed areas at Shark Bay Salt in the Shark Bay World Heritage Area, Western Australia. Untreated seeds of seven species (Aphanopetalum clematideum, Atriplex bunburyana, Austrostipa elegantissima, Melaleuca cardiophylla, Pembertonia latisquamea, Rhagodia baccata, Salsola tragus) exhibited high germination percentages. Seeds of two species (Acacia tetragonophylla, Stylobasium spathulatum) had low imbibition, which increased with hot-water treatment, hence require scarification for germination. Gibberellic acid, smoke water and karrikinolide (a butenolide isolated from smoke) substantially increased germination percentages of three species (Anthocercis littorea, Diplolaena grandiflora, Solanum orbiculatum). Seeds of the remaining six species (Dioscorea hastifolia, Eremophila oldfieldii, Nitraria billardierei, Ptilotus exaltatus, Thryptomene baeckeacea, Zygophyllum fruticulosum) had low germination percentages regardless of treatment. Most species germinated equally well at 26/13 °C and 33/18 °C, however seven species had improved performance at 26/13 °C. This study is significant to land managers and conservation agencies with an interest in optimising germination of arid zone seeds for restoration.