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151.
The Rocky Mountains And The Southwest: Using Feature Names To Study Two Iconic Subregions In The American West 下载免费PDF全文
Geographic regions can be defined in many ways, including via physiography, historical development patterns, language, and culture. After broadly surveying different methods of regionalization and their influences on studies of the American West, this article uses a vernacular‐mapping approach to: first, propose distinctive toponyms that are relatively unique to cultures situated in the American Rocky Mountains and Southwest areas; second, map the spatial distributions of these toponyms across the western American landscape; and, third, compare the resulting distributions to the geographies of western businesses that incorporate regional terms into their corporate names. Notably, while the Rocky Mountains and the Southwest are iconic American regions that have captured the imagination for centuries, their cultural geographies are relatively underexplored in the literature. This article makes a modest contribution to this research gap by using geographic information systems (GIS) to map high concentrations of culturally distinctive feature names. The results reveal that the boundaries of vernacular Southwest and Rocky Mountain regions correspond relatively well with boundaries delineated with physiographic characteristics 相似文献
152.
Hsiao-Chung Tsai Russell L. Elsberry 《Asia-Pacific Journal of Atmospheric Sciences》2018,54(3):421-430
An objective technique to detect and predict intensity bifurcation situations in a five-day Weighted Analog Intensity forecast technique for the western North Pacific (WAIP) has been extended to seven days. A hierarchical cluster analysis is applied to the N analog intensities to separate them into two clusters, which are considered to represent a substantial intensity bifurcation if a threshold maximum velocity difference of 15 kt is satisfied. Two important modifications have been made to develop the bifurcation version for seven-day WAIP forecasts. First, the number of track analogs has been increased from 10 analogs to 16 analogs, which results in larger sample sizes and better performance. Second, separate intensity bias corrections are calculated for the two cluster WAIP forecasts rather than using the same 16-analog intensity bias correction. If an always perfect selection of the correct cluster WAIP forecast of each bifurcation situation is made, a substantial improvement in the intensity mean absolute errors is achieved relative to the original WAIP forecasts based on all 16 of the best analogs. These perfect-cluster selection WAIP forecasts have smaller bias errors and are more highly correlated with the verifying intensities at all forecast intervals through 168 h. Furthermore, the Probability of Detection is improved for the perfect-cluster selection and more realistic intensity spreads are specified. A simple guidance-on-guidance technique is demonstrated to assist the forecasters in selecting the correct WAIP cluster forecast in bifurcation situations. 相似文献
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Theoretical studies of glacial outburst floods (jökulhlaups) assume that: (i) intraglacial floodwater is transported efficiently in isolated conduits; (ii) intraglacial conduit enlargement operates proportionally to increasing discharge; (iii) floodwater exits glaciers through pre‐existing ice‐marginal outlets; and (iv) the morphology and positioning of outlets remains fixed during flooding. Direct field observations, together with historical jökulhlaup accounts, confirm that these theoretical assumptions are not always correct. This paper presents new evidence for spatial and temporal changes in intraglacial floodwater routing during jökulhlaups; secondly, it identifies and explains the mechanisms controlling the position and morphology of supraglacial jökulhlaup outlets; and finally, it presents a conceptual model of the controls on supraglacial outbursts. Field observations are presented from two Icelandic glaciers, Skeiðarárjökull and Sólheimajökull. Video footage and aerial photographs, taken before, during and after the Skeiðarárjökull jökulhlaup and immediately after the Sólheimajökull jökulhlaup, reveal changes in floodwater routing and the positioning and morphology of outlets. Field observations confirm that glaciers cannot transmit floodwater as efficiently as previously assumed. Rapid increases in jökulhlaup discharge generate basal hydraulic pressures in excess of ice overburden. Under these circumstances, floodwater can be forced through the surface of glaciers, leading to the development of a range of supraglacial outlets. The rate of increase in hydraulic pressure strongly influences the type of supraglacial outlet that can develop. Steady increases in basal hydraulic pressure can retro‐feed pre‐existing englacial drainage, whereas transient increases in pressure can generate hydraulic fracturing. The position and morphology of supraglacial outlets provide important controls on the spatial and temporal impact of flooding. The development of supraglacial jökulhlaup outlets provides a new mechanism for rapid englacial debris entrainment. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
155.
Matthew J. Genge Luke Alesbrook Natasha V. Almeida Helena C. Bates Phil A. Bland Mark R. Boyd Mark J. Burchell Gareth S. Collins Luke T. Cornwell Luke Daly Hadrien A. R. Devillepoix Matthias van Ginneken Ansgar Greshake Daniel Hallatt Christopher Hamann Lutz Hecht Laura E. Jenkins Diane Johnson Rosie Jones Ashley J. King Haithem Mansour Sarah McMullan Jennifer T. Mitchell Gavyn Rollinson Sara S. Russell Christian Schröder Natasha R. Stephen Martin D. Suttle Jon D. Tandy Patrick Trimby Eleanor K. Sansom Vassilia Spathis Francesca M. Willcocks Penelope J. Wozniakiewicz 《Meteoritics & planetary science》2024,59(5):948-972
Fusion crusts form during the atmospheric entry heating of meteorites and preserve a record of the conditions that occurred during deceleration in the atmosphere. The fusion crust of the Winchcombe meteorite closely resembles that of other stony meteorites, and in particular CM2 chondrites, since it is dominated by olivine phenocrysts set in a glassy mesostasis with magnetite, and is highly vesicular. Dehydration cracks are unusually abundant in Winchcombe. Failure of this weak layer is an additional ablation mechanism to produce large numbers of particles during deceleration, consistent with the observation of pulses of plasma in videos of the Winchcombe fireball. Calving events might provide an observable phenomenon related to meteorites that are particularly susceptible to dehydration. Oscillatory zoning is observed within olivine phenocrysts in the fusion crust, in contrast to other meteorites, perhaps owing to temperature fluctuations resulting from calving events. Magnetite monolayers are found in the crust, and have also not been previously reported, and form discontinuous strata. These features grade into magnetite rims formed on the external surface of the crust and suggest the trapping of surface magnetite by collapse of melt. Magnetite monolayers may be a feature of meteorites that undergo significant degassing. Silicate warts with dendritic textures were observed and are suggested to be droplets ablated from another stone in the shower. They, therefore, represent the first evidence for intershower transfer of ablation materials and are consistent with the other evidence in the Winchcombe meteorite for unusually intense gas loss and ablation, despite its low entry velocity. 相似文献
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Jordan D. Leone W. Steven Holbrook Clifford S. Riebe Jon Chorover Ty P.A. Ferré Bradley J. Carr Russell P. Callahan 《地球表面变化过程与地形》2020,45(12):2998-3010
The porous near-surface layer of the Earth's crust – the critical zone – constitutes a vital reservoir of water for ecosystems, provides baseflow to streams, guides recharge to deep aquifers, filters contaminants from groundwater, and regulates the long-term evolution of landscapes. Recent work suggests that the controls on regolith thickness include climate, tectonics, lithology, and vegetation. However, the relative paucity of observations of regolith structure and properties at landscape scales means that theoretical models of critical zone structure are incompletely tested. Here we present seismic refraction and electrical resistivity surveys that thoroughly characterize subsurface structure in a small catchment in the Santa Catalina Mountains, Arizona, USA, where slope-aspect effects on regolith structure are expected based on differences in vegetation. Our results show a stark contrast in physical properties and inferred regolith thickness on opposing slopes, but in the opposite sense of that expected from environmental models and observed vegetation patterns. Although vegetation (as expressed by normalized difference vegetation index [NDVI]) is denser on the north-facing slope, regolith on the south-facing slope is four times thicker (as indicated by lower seismic velocities and resistivities). This contrast cannot be explained by variations in topographic stress or conventional hillslope morphology models. Instead, regolith thickness appears to be controlled by metamorphic foliation: regolith is thicker where foliation dips into the topography, and thinner where foliation is nearly parallel to the surface. We hypothesize that, in this catchment, hydraulic conductivity and infiltration capacity control weathering: infiltration is hindered and regolith is thin where foliation is parallel to the surface topography, whereas water infiltrates deeper and regolith is thicker where foliation intersects topography at a substantial angle. These results suggest that bedrock foliation, and perhaps by extension sedimentary layering, can control regolith thickness and must be accounted for in models of critical zone development. © 2020 John Wiley & Sons, Ltd. 相似文献
158.
A moving-grid finite-element model has been developed to model numerically the vertically integrated properties of the atmospheric boundary layer (ABL) in one dimension. The model equations for mean wind velocity and potential temperature are combined with a surface energy budget and predictive equations for boundary-layer height to simulate both stable and unstable ABLs. The nodal position defining the top of the boundary layer is one of the model unknowns and is determined by boundary-layer dynamics. The finite-element method, being an integral method, has advantages of accurate representation of both bulk values and their vertical derivatives, the latter being essential properties of the nocturnal boundary layer. Compared with observations and results of other models, the present model predicts bulk properties very well while retaining a simple and economical form.Journal Paper No. J-12996 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, Project No. 2779. 相似文献
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Late‐glacial environmental and climatic implications are inferred from an insect fauna from organic sediments infilling a palaeochannel on the banks of the River Têt, eastern Pyrénées, France. A pine cone in association with the insect fauna has been radiocarbon dated to 10 920 ± 60 yr BP, namely close to the Allerød – Younger Dryas boundary. Two distinct insect associations appear to be recognisable here. One is an assemblage typical of the high altitude forest and a second is characteristic of an alpine grassland. The close coexistence of these two assemblages is attributed to the climatic cooling towards the start of the Younger Dryas Stadial, when the forest cover broke up into remnant patches interspersed by alpine grassland. It is suggested that in a region of such high relief a mosaic of habitats may have been caused by patchy differences in insolation aspect, especially during a period of climatic deterioration. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献