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Weather Forecasts are for Wimps: Why Water Resource Managers Do Not Use Climate Forecasts 总被引:3,自引:3,他引:0
Short-term climate forecasting offers the promise of improved hydrologic management strategies. However, water resource managers in the United States have proven reluctant to incorporate them in decision making. While managers usually cite poor reliability of the forecasts as the reason for this, they are seldom able to demonstrate knowledge of the actual performance of forecasts or to consistently articulate the level of reliability that they would require. Analysis of three case studies in California, the Pacific Northwest, and metro Washington DC identifies institutional reasons that appear to lie behind managers reluctance to use the forecasts. These include traditional reliance on large built infrastructure, organizational conservatism and complexity, mismatch of temporal and spatial scales of forecasts to management needs, political disincentives to innovation, and regulatory constraints. The paper concludes that wider acceptance of the forecasts will depend on their being incorporated in existing organizational routines and industrial codes and practices, as well as changes in management incentives to innovation. Finer spatial resolution of forecasts and the regional integration of multi-agency functions would also enhance their usability.The title of this article is taken from an advertising slogan for the Oldsmobile Bravura SUV. 相似文献
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On the redshift cut-off for steep-spectrum radio sources 总被引:1,自引:0,他引:1
Matt J. Jarvis Steve Rawlings Chris J. Willott Katherine M. Blundell Steve Eales Mark Lacy 《Monthly notices of the Royal Astronomical Society》2001,327(3):907-917
We use three samples (3CRR, 6CE and 6C*) selected at low radio frequency to constrain the cosmic evolution in the radio luminosity function (RLF) for the 'most luminous' steep-spectrum radio sources. Though intrinsically rare, such sources give the largest possible baseline in redshift for the complete flux-density-limited samples currently available. Using parametric models to describe the RLF, incorporating distributions in radio spectral shape and linear size, as well as the usual luminosity and redshift, we find that the data are consistent with a constant comoving space density between and . We find that this model is favoured over a model with similar evolutionary behaviour to that of optically selected quasars (i.e., a roughly Gaussian distribution in redshift) with probability ratios of and for spatially flat cosmologies with and respectively. Within the uncertainties, this evolutionary behaviour may be reconciled with the shallow decline preferred for the comoving space density of flat-spectrum sources by Dunlop & Peacock and Jarvis & Rawlings, in line with the expectations of unified schemes. 相似文献
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Shaun Cole Peder Norberg Carlton M. Baugh Carlos S. Frenk Joss Bland-Hawthorn Terry Bridges Russell Cannon Matthew Colless Chris Collins Warrick Couch Nicholas Cross Gavin Dalton Roberto De Propris Simon P. Driver George Efstathiou Richard S. Ellis Karl Glazebrook Carole Jackson Ofer Lahav Ian Lewis Stuart Lumsden Steve Maddox Darren Madgwick John A. Peacock Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2001,326(1):255-273
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The later Telychian (late Llandovery, Silurian) sea-level highstand was a suitable setting for global carbonate deposition and reef growth in epeiric seas. However, evidence from the northwest margin of Yangtze Platform indicates that small carbonate platforms developed in rapidly-subsiding small basins and were principally controlled by muddy clastic input. In particular, sediments of the Ningqiang Formation, late Telychian, usually more than 2000 m thick, are mostly shales, but eight major units of discontinuous (15 km maximum width) and relatively thin (120 m maximum thickness) reef-bearing carbonates, which developed when the sedimentation rate apparently lessened, occur within a relatively short time interval. This interval is between upper griestonensis to spiralis-grandis graptolite biozones, estimated as a c. 2 Ma duration. More than 30 small- to medium-scale patch reefs occur in several parts of the sequence, but only within the carbonate units. Shelly faunas common throughout the sequence reveal water depth to have been shallow during deposition of the Ningqiang Formation equivalent to BA2–3, which has a depth range from low intertidal to the base of the photic zone. BA3 is interpreted as being no more than 60 m deep (Boucot, 1975), which is above normal wave base, frequently affected by storms (Chen et al., 1996), and is regarded as optimum depth for high diversity of Silurian faunas (Boucot, 1975; Brett, 1991). Thus, the rate of sediment accumulation kept pace with basement subsidence, and was a substantial factor for limiting reef growth. Sharp contacts between carbonate units and shales indicate that carbonate units are constrained by frequent inputs of terrigenous debris, as the major cause for termination of carbonate deposition. Therefore, carbonate platforms, and reefs they contained, formed during times when sediment input to the basin lessened and ended when it increased; present evidence does not allow correlation to modeled dry episodes, and we interpret the control to be principally tectonic. Overall, sedimentation in the region was terminated by the end of Telychian time by tectonic uplift of the Yangtze Platform; the southwestward migration of palaeocoastline shows this progression. Sedimentation ceased until Middle Devonian time. Ludlow marine transgression has been recognized in the offshore area of Ningjiang Bay. 相似文献
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Richard M. Conrey Peter R. Hooper Peter B. Larson John Chesley Joaquin Ruiz 《Contributions to Mineralogy and Petrology》2001,141(6):710-732
Mt. Jefferson is an andesite-dacite composite volcano in the Cascade Range, the locus of andesite and dacite-dominated volcanism for at least 1 million years. A large trace element data set for Mt. Jefferson and its surrounding mafic volcanic platform effectively rules out any fractionation based model (FC or AFC) for the generation of Mt. Jefferson andesites. Several incompatible element (Zr, Nb, Y) concentrations decrease in the range from basalt to andesite, and then increase in the range from andesite to rhyodacite. Others (Ba, Rb, La, Th) remain constant or show a slight increase in the basalt to andesite range, with modest increases from andesite to rhyodacite. Systematic variations in highly incompatible element ratios such as Ba/La and Rb/Th suggest magma mixing dominates the trace element signatures. Rhyodacites are isotopically uniform (87Sr/86Sr=0.70325-0.70343; 206Pb/204Pb=18.75-18.85; 18O=6.3ǂ.3), whereas andesite and dacite are more variable (87Sr/86Sr=0.70291-0.70353; 206Pb/204Pb=18.59-18.86; 18O=6.0ǂ.6). Typical basaltic andesite has 87Sr/86Sr=0.70326-0.70358, 206Pb/204Pb=18.78-18.85, and 18O=5.9ǂ.4. Sr-rich (>1,000 ppm) basaltic andesite is more variable (87Sr/86Sr=0.70300-0.70360; 206Pb/204Pb=18.70-18.89; 18O=5.9ǂ.4). The data define mixing arrays with one end member at 87Sr/86Sr=0.7029; 206Pb/204Pb=18.59, another at rhyodacite, and a third at 87Sr/86Sr=0.7036; 206Pb/204Pb=18.89. The first end member is defined by Sr-rich (800-1,200 ppm) andesite with high Al2O3, and low K2O, Ba, and Rb/Th; the third one by K2O- and very Sr-rich (>2,000 ppm) shoshonite. Isotopic data for basalts in northern Oregon preclude any fractionation relationship between basalt and either rhyodacite or Sr-rich andesite (e.g., the minimum 206Pb/204Pb ratio in basalt is 18.83). Considered in light of geophysical models for the Cascades, these data suggest two types of crustal melting beneath the arc. Rhyodacite may be generated at 25-30 km depth by partial melting of arc basalt-like amphibolite at 850-900 °C. Sr-rich andesite may be formed by partial melting of depleted MORB-like mafic granulite at 35-45 km depth at 1,000-1,100 °C. Experimental and REE evidence supports these interpretations as does the restriction of Sr-rich andesite in the Cascades to the area south of the 100 mW/m2 heat flow contour between Mt. Jefferson and Mt. Hood. Thick crust and high heat flow are necessary to produce such andesite. 相似文献