Wavelet analysis of inter‐annual variability in the runoff regimes of glacial and nival stream catchments,Bow Lake,Alberta     

Melissa Lafrenire  Martin Sharp 《水文研究》2003,17(6):1093-1118

Continuous wavelet analyses of hourly time series of air temperature, stream discharge, and precipitation are used to compare the seasonal and inter‐annual variability in hydrological regimes of the two principal streams feeding Bow Lake, Banff National Park, Alberta: the glacial stream draining the Wapta Icefields, and the snowmelt‐fed Bow River. The goal is to understand how water sources and flow routing differ between the two catchments. Wavelet spectra and cross‐wavelet spectra were determined for air temperature and discharge from the two streams for summers (June–September) 1997–2000, and for rainfall and discharge for the summers of 1999 and 2000. The diurnal signal of the glacial runoff was orders of magnitude higher in 1998 than in other years, indicating that significant ice exposure and the development of channelized glacial drainage occurred as a result of the 1997–98 El Niño conditions. Early retreat of the snowpack in 1997 and 1998 led to a significant summer‐long input of melt runoff from a small area of ice cover in the Bow River catchment; but such inputs were not apparent in 1999 and 2000, when snow cover was more extensive. Rainfall had a stronger influence on runoff and followed quicker flow paths in the Bow River catchment than in the glacial catchment. Snowpack thickness and catchment size were the primary controls on the phase relationship between temperature and discharge at diurnal time scales. Wavelet analysis is a fast and effective means to characterize runoff, temperature, and precipitation regimes and their interrelationships and inter‐annual variability. The technique is effective at identifying inter‐annual and seasonal changes in the relative contributions of different water sources to runoff, and changes in the time required for routing of diurnal meltwater pulses through a catchment. However, it is less effective at identifying changes/differences in the type of the flow routing (e.g. overland flow versus through flow) between or within catchments. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Late/Middle/Early/Ichnocambrian： a communication-friendly nomenclature for the epochs of a quadripartite Cambrian Period     

Stephen M. Rowland Melissa Hicks 《《幕》》2006,29(2):128-129

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IGU commission on changing rural systems     

Melissa Pearrow 《GeoJournal》1991,24(3):325-326

The International Geographical Union Reports

IGU commission on changing rural systems  相似文献   

A practical approach to grain shape quantification     

Melissa R. Cox  Muniram Budhu 《Engineering Geology》2008,96(1-2):1-16

Grain shape is a key factor affecting the mechanical properties of granular materials. However, grain shape quantification techniques to distinguish one granular material from another have not reached a stage of development for inclusion in modeling the behavior of granular materials. Part of the problem is the equipment of choice for grain shape measurement is the scanning electron microscopes. This is a relatively expensive and complex device. In this paper, we investigate a practical approach using light microscopy to quantify grain shape and to identify the key shape parameters that can distinguish grains. A light microscope was found to produce grain images with sufficient quality for the purpose of observing the grain shape profile. Several grain shape parameters were determined for eight different sands. We found Circularity, Roundness, Compactness, Sphericity, Aspect Ratio and ModRatio to be the key shape parameters that differentiate these sand grains.  相似文献   

Theorizing the digital divide: Information and communication technology use frameworks among poor women using a telemedicine system     

Melissa R. Gilbert  Michele Masucci 《Geoforum》2008,39(2):912-925

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Geochemistry of silicic magmas in the Macolod Corridor, SW Luzon, Philippines: evidence of distinct, mantle-derived, crustal sources for silicic magmas     

Thomas A. Vogel  Timothy P. Flood  Lina C. Patino  Melissa S. Wilmot  Raymond Patrick R. Maximo  Carmencita B. Arpa  Carlo A. Arcilla  James A. Stimac 《Contributions to Mineralogy and Petrology》2006,151(3):267-281

Silicic volcanic deposits (>65 wt% SiO₂), which occur as domes, lavas and pyroclastic deposits, are relatively abundant in the Macolod Corridor, SW Luzon, Philippines. At Makiling stratovolcano, silicic domes occur along the margins of the volcano and are chemically similar to the silicic lavas that comprise part of the volcano. Pyroclastic flows are associated with the Laguna de Bay Caldera and these are chemically distinct from the domes and lavas at Makiling stratovolcano. As a whole, samples from the Laguna de Bay Caldera contain lower concentrations of MgO and higher concentrations of Fe₂O_3(t) than the samples from domes and lavas. The Laguna de Bay samples are more enriched in incompatible trace elements. The silicic rocks from the domes, Makiling Volcano and Laguna de Bay Caldera all contain high alkalis and high K₂O/Na₂O ratios. Melting experiments of primitive basalts and andesites demonstrate that it is difficult to produce high K₂O/Na₂O silicic magmas by fractional crystallization or partial melting of a low K₂O/Na₂O source. However, recent melting experiments (Sisson et al., Contrib Mineral Petrol 148:635–661, 2005) demonstrate that extreme fractional crystallization or partial melting of K-rich basalts can produce these silicic magmas. Our model for the generation of the silicic magmas in the Macolod Corridor requires partial melting of mantle-derived, evolved, moderate to K-rich, crystallized calc-alkaline magmas that ponded and crystallized in the mid-crust. Major and trace element variations, along with oxygen isotopes and ages of the deposits, are consistent with this model. Electronic Supplementary Material Supplementary material is available for this article at  相似文献   

The scalar politics of translation     

Melissa W Wright 《Geoforum》2002,33(4):413-414

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Geochemical Characterization of Bolivian Formative Earthen Architecture by Wavelength‐Dispersive X‐ray Fluorescence     

Melissa A. Goodman‐Elgar  Nichole S. Bettencourt  Richard Conrey 《Geoarchaeology》2015,30(1):32-58

In this study, we employ wavelength‐dispersive X‐ray fluorescence (WDXRF) to characterize construction materials from Formative civic architecture (1000 B.C.E.–C.E. 400), ethnographic mudbricks, and off‐site controls from the Taraco Peninsula, Bolivia. The preparation of earthen construction materials for civic buildings can shed light on aspects of community development such as labor organization, resource management, and architectural technologies. We apply geochemical results to reconstructing how public buildings were made as communities moved toward socio‐political complexity in this region. However, there are few geochemical studies in the Andes, and little prior scientific analysis of earthen architecture. We therefore tested the efficacy of WDXRF for this region, and developed control materials. Our archaeological samples were selected from two Formative villages, Chiripa and Kala Uyuni. In this study, we performed WDXRF analyses on 63 archaeological and control samples including archaeological floors, walling, plasters, and mortars, as well as contemporary ethnographic walling and topsoils. Elemental signatures for 28 elements clearly distinguished the archaeological flooring, walling, plaster, and mortars from ethnographic and off‐site controls. More subtle variations were detected that distinguish study sites and the different material types. Laboratory‐calibrated multi‐element XRF effectively supports efforts to reconstruct the pathways to social complexity in the Titicaca Basin.  相似文献   

Particulate air pollution from wildfires in the Western US under climate change     

Jia Coco Liu  Loretta J. Mickley  Melissa P. Sulprizio  Francesca Dominici  Xu Yue  Keita Ebisu  Georgiana Brooke Anderson  Rafi F. A. Khan  Mercedes A. Bravo  Michelle L. Bell 《Climatic change》2016,135(3-4):655-668

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Influence of the Mississippi River on <Emphasis Type="Italic">Pseudo-nitzschia</Emphasis> spp. Abundance and Toxicity in Louisiana Coastal Waters     

Sibel Bargu  Melissa M. Baustian  Nancy N. Rabalais  Ross Del Rio  Benjamin Von Korff  R. Eugene Turner 《Estuaries and Coasts》2016,39(5):1345-1356

The presence of domoic acid (DA) toxin from multiple species of Pseudo-nitzschia is a concern in the highly productive food webs of the northern Gulf of Mexico. We documented the Pseudo-nitzschia presence, abundance, blooms, and toxicity over three years along a transect ～100 km west of the Mississippi River Delta on the continental shelf. Pseudo-nitzschia were present throughout the year and occurred in high abundances (>10⁴ cells l^?1) in the early spring months during high Mississippi River (MSR) flow (～20,000 m³ s^?1) but were most abundant (>10⁶ cells l^?1) when MSR discharge was relatively lower among the spring months. A high particulate toxin production (maximum reaching 13 μg DA l^?1) was associated with the high cell abundances and exceeded, by an order of magnitude, prior reports of particulate DA concentrations in Louisiana coastal waters. Differences in Pseudo-nitzschia peak times and its toxicity were correlated mainly with the timing and magnitude of MSR discharge and changes in associated parameters such as nutrient stoichiometry and salinity. A negative relationship between high MSR discharge and Pseudo-nitzschia and particulate DA concentrations was documented. These riverine dynamics have the potential to influence DA contamination in pelagic and benthic food webs in the coastal waters of the northern Gulf of Mexico.  相似文献