DISCRIMINANT PRINCIPAL COMPONENTS ANALYSIS

When the number of variables exceeds the number of samples, one method of multivariate discriminationis to use principal components analysis to reduce the dimensionality and then to perform canonicalvariates analysis (PC-CVA). This paper proposes an alternative approach in which discriminant analysisis carried out by a weighted principal component analysis of the group means (DPCA). This method doesnot require prior data reduction and produces discriminant factors that are orthogonal in the original dataspace. The theory and performance of the two methods are compared. Although the individual factors ofDPCA are found to be less discriminating than PC-CVA, the overall discrimination, calculated bymultivariate analysis of variance, and the predictive value, estimated by the leaving-one-out error rate,are broadly comparable.     

The relationship between basin and margin thermal evolution assessed by fission track thermochronology: an application to offshore southern Norway

Abstract We use a quantitative model of apatite fission track (AFT) annealing to constrain the thermal evolution of a sedimentary basin and its margin. Apatites deposited in a basin contain several types of information. Provided temperatures remained below ?70°C, they retain much of their provenance thermal signatures and mainly record the thermal evolution of their source area. Above 70°C, the fission tracks in apatite rapidly fade, reflecting the thermal evolution of the basin. Therefore, downhole AFT dates in a well section can in principle be used to assess both the provenance detail (from shallow/cool samples) and the subsequent thermal history in the basin (from the deeper samples). We apply this concept to the south Norwegian offshore and onshore using AFT and ZFT (zircon fission track) data; the latter constrain maximum palaeotemperatures and provide additional provenance information. AFT and ZFT data from three offshore wells in the northern North Sea are shown to contain a record of palaeogeographical and tectonic evolution, closely associated with the Norwegian basement. ZFT data from Middle Triassic sediments suggest a Permian volcanic source. Modelling of AFT data from Jurassic sediments presently residing at temperatures below 70°C indicate rapid cooling during the Late Triassic to Early Jurassic, similar to onshore AFT data. During the Cretaceous minor sediment supply was derived from the Norwegian basement, as evidenced by ZFT ages that do not correlate to the onshore, suggesting that parts of southern Norway were covered with sediments at this time. At the end of the Palaeogene and during the Neogene, the south Norwegian basement again became a major source of elastics. AFT and ZFT data indicate that all wells are presently at maximum temperatures. No significant (> 500 m) erosion events are indicated in the three wells since the Jurassic. AFT data have not yet effectively equilibrated to present-day temperatures as nonzero fission track ages are maintained in sediments currently at temperatures of > 120°C. This implies that the present-day thermal regime has only recently been installed. Probable causes include rapid subsidence and an increase in the geothermal gradient during the last 5 Myr.     

The U.K. Regional Research Laboratory Initiative 1987–1991

Abstract

The Economic and Social Research Council in the United Kingdom (U.K.) established the Regional Research Laboratory (RRL) Initiative in 1987 to improve facilities for data processing in the social sciences. The Trial Phase in 1987, which was modestly funded for 18 months, established four trial sites and a National Co-ordinator. The Main Phase of the Initiative, covering 8 laboratories at 10 locations, was launched in October 1988, following submission and selection of proposals. Although not originally planned as such, the initiative became a Geographical Information Systems (GIS) programme because the best proposals came from geographers and planners skilled in the processing of spatial data and because of interest stimulated by the influential Chorley Report. This article reviews the major aims of the Initiative and the progress reached after two years to September 1990. The initiative was highly effective in stimulating new research and development work that had regional, national and international dimensions. Nevertheless, with the exception of one RLL, funding has not been continued beyond 1991 and the initiative has been replaced by a network of University Departments working to continue the academic work with GIS in the U.K. for the next three years.     

Mass spectrometric dating of flowstones from Stump Cross Caverns and Lancaster Hole,Yorkshire: palaeoclimate implications

A terrestrial flowstone sequence 97 cm thick from Stump Cross Caverns, Yorkshire, has been dated by both mass spectrometric and alpha spectrometric ²³⁸U-²³⁴U-²³⁰Th dating, and is demonstrated to have been deposited predominantly during interstadial periods over the last 170 ka, with no growth in periods of glaciation or within the Oxygen Isotope Stage 5 interglacial. Growth also occurs within Oxygen Isotope Stages 4 and 6, the former possibly correlating with interstadials recognised in high-resolution ice and ocean-core records. Comparison with the timing of growth of a mass spectrometrically dated Lancaster Hole flowstone, also from the same region, demonstrates only limited agreement. These differences are due to two factors limiting deposition at Stump Cross: flooding of the cave passage in warm periods, and the development of continuous permafrost or glacier cover in periods of severe climatic deterioration. Deposition at Lancaster Hole was controlled by limitations in ground-water supply rather than flooding of the cave passage. The results presented here demonstrate that in addition to regional palaeoclimate factors, local site conditions may limit speleothem growth. We conclude that in future palaeoclimate studies, the growth record from several coeval speleothem samples must be considered before a regional palaeoclimate interpretation can be made.     

Towards a framework for learning with GIS: The case of Urban World, a hypermap learning environment based on GIS

Off-the-shelf GIS toolboxes are inadequate for pedagogic purposes. Urban World , an Arc View application, attempts to address this shortcoming by including special features designed to foster student progress towards a better understanding of urban environments. This paper provides context for the Urban World system in an active, authentic learning environment for students of urban geography and planning at junior and senior levels in undergraduate curricula at universities in the United States. The paper describes the rationale for, and implementation of, several components of Urban World : a special graphid user interface; productivity tools for facilitating the acquisition of practical skills of mapping and spatial analysis; tools for accessing, undertaking, and submitting homework assignments in a paper-less class; and various devices for assisting students to undertake spatial reasoning. GIS are Seen as an enabling technology for improving understanding by means of engaging students in empirical analysis. Spatial problem solvers and decision makers reach sound conclusions by employing reasoning skills applied to well-formed databases; scientific research makcs progress with sound reasoning of many types. The effective teaching and learning about the geography of our world requires a strong foundation of spatid reasoning.     

Constraints on the Trace Element Composition of the Archean Mantle Root beneath Somerset Island, Arctic Canada

Peridotites that sample Archean mantle roots are frequentlyincompatible trace element enriched despite their refractorymajor element compositions. To constrain the trace element budgetof the lithosphere beneath the Canadian craton, trace elementand rare earth element (REE) abundances were determined fora suite of garnet peridotites and garnet pyroxenites from theNikos kimberlite pipe on Somerset Island, Canadian Arctic, theirconstituent garnet and clinopyroxene, and the host kimberlite.These refractory mantle xenoliths are depleted in fusible majorelements, but enriched in incompatible trace elements, suchas large ion lithophile elements (LILE), Th, U and light rareearth elements (LREE). Mass balance calculations based on modalabundances of clinopyroxene and garnet and their respectiveREE contents yield discrepancies between calculated and analyzedREE contents for the Nikos bulk rocks that amount to LREE deficienciesof 70–99%, suggesting the presence of small amounts ofinterstitial kimberlite liquid (0·4–2 wt %) toaccount for the excess LREE abundances. These results indicatethat the peridotites had in fact depleted or flat LREE patternsbefore contamination by their host kimberlite. LREE and Sr enrichmentin clinopyroxene and low Zr and Sr abundances in garnet in low-temperatureperidotites (800–1100°C) compared with high-temperatureperidotites (1200–1400°C) suggest that the shallowlithosphere is geochemically distinct from the deep lithospherebeneath the northern margin of the Canadian craton. The Somersetmantle root appears to be characterized by a depth zonationthat may date from the time of its stabilization in the Archean. KEY WORDS: Canada; mantle; metasomatism; peridotite; trace elements     

A HYDROLOGICAL MODEL STUDY OF A FORESTED AND A CUTOVER SLOPE

ABSTRACT

The problem of analysing and predicting the effect of vegetation removal on the hydrological regime or soil water potential on steep slopes was approached through an experimental model set up in a greenhouse. A tilting soil bin positioned at different slope angles simulated a soil layer overlying impervious bedrock, and a forest cover was modelled by a number of small trees. The response of the soil water potential to simulated rain storms was studied first for the forested and later for the cutover slope. Transpiration in the greenhouse was measured by means of phytometers.

The results showed that a forest cover accelerates the soil moisture depletion in a shallow soil mantle regardless of the steepness of the slope. For a storm of given intensity and duration, the recharge phase for the clear-cut slope was therefore much shorter than for the forested one. The slope angle was only responsible for the distribution of recharge and the initial hydrological conditions when drainage had ceased. During the drainage phase the flow in the slope was two-dimensional, whereas it was essentially one-dimensional (i.e. vertical upwards) after field capacity had been reached. At this point the matric suction increased exponentially with time for suctions within the tensiometer range. Within this same range water loss from any point in the soil took place at a constant rate. This result is consistent with field observations.     

Attenuation characteristics of peak acceleration in North China and comparison with those in the eastern part of North America

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Evaluation of High-Resolution WRF Model Simulations of Surface Wind over the West Coast of India

This paper presents results from a statistical validation of the hindcasts of surface wind by a high-reso-ution-mesoscale atmospheric numerical model Advanced Research WRF （ARW3.3）, which is set up to force the operational coastal ocean forecast system at Indian Na- tional Centre for Ocean Information Services （INCOIS）. Evaluation is carried out based on comparisons of day-3 forecasts of surface wind with in situ and remote-sensing data. The results show that the model predicts the surface wind fields fairly accurately over the west coast of India, with high skill in predicting the surface wind during the pre-monsoon season. The model predicts the diurnal variability of the surface wind with reasonable accuracy. The model simulates the land-sea breeze cycle in the coastal region realistically, which is very clearly observed during the northeast monsoon and pre-monsoon season and is less prominent during the southwest monsoon season.     

Depolarization ratio profiling at several wavelengths in pure Saharan dust during SAMUM 2006

Vertical profiles of the linear particle depolarization ratio of pure dust clouds were measured during the Saharan Mineral Dust Experiment (SAMUM) at Ouarzazate, Morocco (30.9°N, –6.9°E), close to source regions in May–June 2006, with four lidar systems at four wavelengths (355, 532, 710 and 1064 nm). The intercomparison of the lidar systems is accompanied by a discussion of the different calibration methods, including a new, advanced method, and a detailed error analysis. Over the whole SAMUM periode pure dust layers show a mean linear particle depolarization ratio at 532 nm of 0.31, in the range between 0.27 and 0.35, with a mean Ångström exponent (AE, 440–870 nm) of 0.18 (range 0.04–0.34) and still high mean linear particle depolarization ratio between 0.21 and 0.25 during periods with aerosol optical thickness less than 0.1, with a mean AE of 0.76 (range 0.65–1.00), which represents a negative correlation of the linear particle depolarization ratio with the AE. A slight decrease of the linear particle depolarization ratio with wavelength was found between 532 and 1064 nm from 0.31 ± 0.03 to 0.27 ± 0.04.