Pulling apart: new perspectives on the spatial dimensions of neighbourhood income disparities in Canadian cities

Journal of Geographical Systems - The spatial configurations of changes in the distribution of incomes within Canada’s eight largest metropolitan areas are examined using a new approach based...     

A comparison of rainfall estimation techniques for sub-Saharan Africa

Interpolated rain-gauge data were compared to Meteosat-based precipitation estimates for sub-Saharan Africa. Validation was carried out using a dataset from a very dense gauge network in South Africa, on a point-to-pixel (PO–PI) as well as on a pixel-to-pixel (PI–PI) basis. Error criteria computed at the gauged pixels indicate that overall the interpolated estimates perform similarly to the satellite-based data: they provide good estimates of lower but underestimate larger precipitation amounts. It is concluded that the satellite estimates are more fitted for the operational modelling of processes such as surface runoff and soil erosion, especially in the developing areas where resources are scarce.     

香港九龙大坑东地下蓄水方案数值研究

香港九龙大坑东地下蓄水方案(Tai Hang Tung Storage Scheme-THTSS)是香港西九龙渠道改善二期计划的一个重要组成部分,其目标是解决香港九龙繁华拥挤、人口稠密的商业中心旺角一带的洪水淹没问题。THTSS即是在经常洪水淹没区域(大坑东和界限街水渠交接处)上游足球场下面建立一个100 000 m3的地下蓄水池。本文建立了一个能处理明渠缓流和急流、封闭管道有压流、侧流堰和渠道汇合处过渡流于一体的一维水力数学模型,用1:22正态物理模型恒定流下的结果进行验证。数值模型计算了在50年一遇暴雨下,非恒定洪水在不同的侧流堰方案下的流动过程。结合物理模型试验结果,选择最佳的地下蓄水方案。计算结果表明,大坑东地下蓄水方案确实能加强旺角地区地洪水控制能力,并能通过50年一遇暴雨的洪水。     

Mg isotope heterogeneity in the Allende meteorite measured by UV laser ablation-MC-ICPMS and comparisons with O isotopes

First results from a new UV laser ablation MC-ICPMS method for measuring Mg isotope ratios in situ in meteoritical materials show that there are mass-dependent variations in δ²⁵Mg and δ²⁶Mg up to 1.5 ‰ per amu in chondrules and 0.3‰ per amu in a CAI from the Allende meteorite. In both cases the mass-dependent fractionation is associated with alteration. Comparisons with laser ablation O isotope data indicate that incorporation of pre-existing grains of forsterite with distinct Mg and O isotopic compositions and post-formation alteration both contributed to the variability in Mg isotope ratios in the chondrules, resulting in a correlation between high δ²⁵Mg and low Δ¹⁷O. The laser ablation analyses of the CAI show that high-precision determinations of both δ²⁵Mg and δ²⁶Mg can be used to discriminate features of the ²⁶Al-²⁶Mg isotope system that are relevant to chronology from those that result from element mobility.     

Geoscience of ancient Mediterranean harbours

Although much has been written on the subject of ancient Mediterranean harbours, the relatively new area of harbour geoarchaeology remains dispersed in the geoscience and archaeological literature. Over a decade of research has amassed rich and varied datasets of anthropogenically forced coastal evolution, with a remarkable number of between-site analogies. This new research field also shows the rich potential of geoscience to reconcile important archaeological questions. No single publication, however, has yet drawn on these geological patterns to yield a detailed overview suitable for geoscientists and environmental archaeologists. The aim of this review article is to (1) discuss how ancient harbours have come to be preserved in the geological record; (2) expound the basic principles and palaeoenvironmental tools underpinning ancient harbour geoarchaeology; (3) outline some of the most significant research advances made; and (4) discuss a new chrono-stratigraphic model applicable to harbour sequences.     

Modelling the effects of porous media deformation on the propagation of water-table waves in a sandy unconfined aquifer

This paper examines the influence of porous media deformation on water-table wave dispersion in an unconfined aquifer using a numerical model which couples Richards’ equation to the poro-elastic model. The study was motivated by the findings of Shoushtari et al. (J Hydrol 533:412–440, 2016) who were unable to reproduce the observed wave dispersion in their sand flume data with either numerical Richards’ equation models (assuming rigid porous media) or existing analytic solutions. The water-table wave dispersion is quantified via the complex wave number extracted from the predicted amplitude and phase profiles. A sensitivity analysis was performed to establish the influence of the main parameters in the poro-elastic model, namely Young’s modulus (E) and Poisson’s ratio (ν). For a short oscillation period (T?=?16.4 s), the phase lag increase rate (k _i) is sensitive to the chosen values of E and ν, demonstrating an inverse relationship with both parameters. Changes in the amplitude decay rate (k _r), however, were negligible. For a longer oscillation period (T?=?908.6 s), variations in the values of E and ν resulted in only small changes in both k _r and k _i. In both the short and long period cases, the poro-elastic model is unable to reproduce the observed wave dispersion in the existing laboratory data. Hence porous media deformation cannot explain the additional energy dissipation in the laboratory data. Shoushtari SMH, Cartwright N, Perrochet P, Nielsen P (2016) The effects of oscillation period on groundwater wave dispersion in a sandy unconfined aquifer: sand flume experiments and modelling. J Hydrol 533:412–440.     

Reconstruction and visualisation of melt topology in veined microdioritic enclaves

A number of xenocrystic microdioritic enclaves within the Ross of Mull Granite contain narrow veins of monzonitic material that have formed through the selective partial fusion of granitic magma mechanically incorporated into the microdiorite magma. Field evidence suggests that, as melting of the granitic material ensued, a monzonitic melt formed and exfiltrated from the surrounding microdioritic matrix resulting in Saffman–Taylor instabilities and the development of viscous fingering phenomena. The monzonitic melt network is now preserved as monzonitic veins. Mechanical serial sectioning through a representative veined microdioritic enclave shows that: (a) the topology of the veins is complex but crudely polyhedral, (b) there is porosity (monzonitic melt fraction) variation throughout the length of the veined enclave and (c) that the monzonitic veins are interconnected in three dimensions. Using image analysis software, the total porosity of individual veined enclave sections has been estimated, along with the variation in porosity with depth. Three dimensional rendering and animation software has been used to reconstruct and visualise the monzonitic melt network using Apple QuickTime™ software. The above method provides a cheap and powerful way of visualising remnant macroscopic transport properties (such as connectivity and melt topology) in partially molten igneous rocks.Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.     

Effects of atmospheric stability conditions on heat fluxes from small water surfaces in (semi-)arid regions

Atmospheric stability conditions over the water surface can affect the evaporative and convective heat fluxes from the water surface. Atmospheric instability occurred 72.5% of the time and resulted in 44.7 and 89.2% increases in the average and maximum estimated evaporation, respectively, when compared to the neutral condition for a small shallow lake (Binaba) in Ghana. The proposed approach is based on the bulk-aerodynamic transfer method and the Monin-Obukhov similarity theory (MOST) using standard meteorological parameters measured over the surrounding land. For water surface temperature, a crucial parameter in heat flux estimation from water surfaces, an applicable method is proposed. This method was used to compute heat fluxes and compare them with observed heat fluxes. The heat flux model was validated using sensible heat fluxes measured with a 3-D sonic anemometer. The results show that an unstable atmospheric condition has a significant effect in enhancing evaporation alongside the sensible heat flux from water surfaces.