What El Niño can tell us about human health and global climate change     

Simon Hales  Sari Kovats  Alistair Woodward 《Global Change & Human Health》2000,1(1):66-77

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On large-scale flow structures in a gravel-bed river     

Thomas Buffin-Blanger  Andr G. Roy  Alistair D. Kirkbride 《Geomorphology》2000,32(3-4)

Previous studies have suggested the presence of large-scale flow structures in gravel-bed rivers. These structures are pictured as intermittent high-speed wedges separated by regions of lower velocity. However, the characteristics of these structures have not been examined in detail through either visualisation techniques or detailed field measurements. This paper confirms the presence of large-scale flow structures in gravel bed rivers, pictures their sequence and patterns and characterises their mean and individual properties. The analysis relies on a new technique for displaying velocity fluctuations in a space–time matrix that allows one to see the structures as they pass an array of current meters. Streamwise and vertical velocities were measured simultaneously with an array of three electromagnetic current meters. The sampling frequency was 20 Hz. Five velocity profiles of up to 13 1-min series of measurements and one profile of three 20-min measurements were sampled. These data suggest the presence of large wedges of faster fluid joined by regions of slower fluid. Space–time correlation analysis confirmed the presence of vertical coherence of the flow. The average angle of the front of the wedges is 36°. Although individual structures are variable in size and shape, a new detection technique using all three velocity signals simultaneously showed that their average frequency is nine events per minute and their duration is more than 2 s. The high-speed wedges display a complex organisation and do not show a preferred sequence of events as was postulated by previous studies. Because of their duration and size, these high-speed wedges are likely to play a major role in bedload sediment transport.  相似文献   

Linking pollution induced community tolerance (PICT) and microbial community structure in chronically metal polluted estuarine sediments     

Ogilvie LA  Grant A 《Marine environmental research》2008,65(2):187-198

We tested the ability of pollution induced community tolerance (PICT) to detect the effects of chronic metal pollution on estuarine sediment microbial communities, along a gradient spanning two orders of magnitude in metal concentrations. In tandem, we investigated the associated microbial community structure using terminal restriction fragment length polymorphism (T-RFLP). Tolerance of microbes to Cu, measured as IC50 (inhibitory concentration 50%), was strongly correlated with pore water Cu concentration (r(2)=0.842). No strong correlation existed for other metals tested, highlighting the ability of PICT to identify the pollutant causing a toxic effect. There was no correlation between microbial community structure and community tolerance to metals tested, but analysis of community structure did provide some information on reasons for observed PICT response. PICT methodology used here provided a greater strength and consistency of association with pollutant concentration compared to microbial community structure and can be recommended as a sensitive indicator of metal pollution on estuarine sediment microbial communities.  相似文献   

A finite volume discretization of the pressure gradient force using analytic integration   总被引：1，自引：0，他引：1  

Alistair Adcroft  Robert Hallberg  Matthew Harrison 《Ocean Modelling》2008,22(3-4):106-113

Layered ocean models can exhibit spurious thermobaric instability if the compressibility of sea water is not treated accurately enough. We find that previous solutions to this problem are inadequate for simulations of a changing climate. We propose a new discretization of the pressure gradient acceleration using the finite volume method. In this method, the pressure gradient acceleration is exhibited as the difference of the integral “contact” pressure acting on the edges of a finite volume. This integral “contact” pressure can be calculated analytically by choosing a tractable equation of state. The result is a discretization that has zero truncation error for an isothermal and isohaline layer and does not exhibit the spurious thermobaric instability.  相似文献   

School-based indicators of tuna population status     

Dell  James T.; Hobday  Alistair J. 《ICES Journal of Marine Science》2008,65(4):612-622

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Cycling amongst Māori: Patterns,influences and opportunities     

Rhys Jones  Bruce Kidd  Kirsty Wild  Alistair Woodward 《New Zealand geographer》2020,76(3):182-193

This paper outlines the results of mixed-methods research on Māori and cycling. Our findings suggest that Māori cycle at similar rates to Pākehā (NZ European); however conditions may differ, possibly indicating higher levels of “necessity cycling” amongst Māori. Māori experience similar barriers to cycling, including a lack of suitable cycling infrastructure, but these occur against a backdrop of stark social, economic and transport-related inequities. Particular barriers for Māori may include inflexible work conditions, concerns about neighbourhood safety, inadequate provision for social cycling, and lack of access to places of importance to Māori. We identify potential solutions, including more whānau-friendly and culturally safe cycling infrastructure, and cycling programmes designed around Māori commitments to whanaungatanga and kaitiakitanga.  相似文献   

Alternate erosion and deposition in the Yangtze Estuary and the future change     

Zhu  Boyuan  Li  Yitian  Yue  Yao  Yang  Yunping  Liang  Enhang  Zhang  Chuncai  Borthwick  Alistair G. L. 《地理学报(英文版)》2020,30(1):145-163

Journal of Geographical Sciences - The morphological changing trend of the Yangtze Estuary, the largest estuary of Asia, has become a focus of research in recent years. Based on a long series of...  相似文献