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121.
122.
A comparison of statistical downscaling and climate change factor methods: impacts on low flows in the River Thames, United Kingdom 总被引:13,自引:0,他引:13
Strategic-scale assessments of climate change impacts are often undertaken using the change factor (CF) methodology whereby future changes in climate projected by General Circulation Models (GCMs) are applied to a baseline climatology. Alternatively, statistical downscaling (SD) methods apply climate variables from GCMs to statistical transfer functions to estimate point-scale meteorological series. This paper explores the relative merits of the CF and SD methods using a case study of low flows in the River Thames under baseline (1961–1990) and climate change conditions (centred on the 2020s, 2050s and 2080s). Archived model outputs for the UK Climate Impacts Programme (UKCIP02) scenarios are used to generate daily precipitation and potential evaporation (PE) for two climate change scenarios via the CF and SD methods. Both signal substantial reductions in summer precipitation accompanied by increased PE throughout the year, leading to reduced flows in the Thames in late summer and autumn. However, changes in flow associated with the SD scenarios are generally more conservative and complex than that arising from CFs. These departures are explained in terms of the different treatment of multidecadal natural variability, temporal structuring of daily climate variables and large-scale forcing of local precipitation and PE by the two downscaling methods. 相似文献
123.
Marcel Zphoris Hubert Holin Franck Lavie Nadine Cenac Michel Cluzeau Olivier Delas Franoise Eideliman Jacqueline Gagneux Alain Gander Corinne Thibord 《Atmospheric Research》2005,74(1-4):581-595
A modified ceilometer has been used during the second Intensive Observation Period (IOP) of the “Expérience sur Site pour COntraindre les Modèles de Pollution atmosphériques et de Transport d'Émission” (ESCOMPTE) to perform continuous remote observations of aerosol accumulations in the first 3 km of the atmosphere. These observations encompassed an episode of intense particulate and photochemical pollution. The submicronic particles density, measured at an altitude of 600 m, went from a very low point of a few tens of particles per cubic centimeter (at the end of a Mistral episode in the free atmosphere) to a high point of more than 4500 particles per cubic centimeter (when pollutants were trapped by thermal inversions).The main result is that this instrument enables a fine documentation of the mixing layer height and of aerosol particles stratifications and circulation. Airborne aerosol measurements have been made above the mountainous region of Mérindol in order to validate in situ the remote sensing measurements. Ozone measurements near the summit of the mountains as well as in the valley were performed in order to correlate aerosol accumulation and ozone concentration. As a notable example, the two-layer aerosol stratification seen in the first 2 days of IOP 2b in that part of the ESCOMPTE domain confirms the results of another team which used backtrajectories. The low-altitude pollution for this timeframe had a local origin (the Fos industrial area), whereas above 500 m, the air masses had undergone regional-scale transport (from north-eastern Spain).The second major result is the highlighting of a pattern, in sea breeze conditions and in this part of the ESCOMPTE experiment zone, of nocturnal aerosol accumulation at an altitude of between 500 and 2000 m, followed by high ozone concentration the next day. 相似文献
124.
Curtis R. Olsen Ingvar L. Larsen Patrick J. Mulholland Karen L. Von Damm Jacqueline M. Grebmeier Linda C. Schaffner Robert J. Diaz Maynard M. Nichols 《Estuaries and Coasts》1993,16(3):683-696
Studies have shown that many chemically-reactive contaminants become associated with fine particles in coastal waters and that the rate, patterns, and extent of contaminant accumulation within estuarine systems are extremely variable. In this paper, we briefly review our findings concerning the accumulation patterns of contaminants in several estuarine systems along the eastern coastline of the United States, and have applied a well-established concept in geology, that is “an equilibrium profile,” to explain the observed large variations in these patterns. We show that fine-particle deposition is the most important factor affecting contaminant accumulation in estuarine areas, and that accumulation patterns are governed by physical processes acting to establish or maintain a sediment surface in dynamic equilibrium with respect to sea level, river discharge, tidal currents, and wave activity. Net long-term particle and particle-associated contaminant accumulations are negliglible in areas where the sediment surface has attained “dynamic equilibrium” with the hydraulic regime. Contaminant, accumulation in these areas primarily occurs by the exchange of contaminant-poor sedimentary particles with contaminant-rich suspended particles during physical or biological mixing of the surface sediment. Virtually the entire estuarine particulate and contaminant load bypasses these “equilibrium” areas to accumulate at extremely rapid in relatively small areas that are temporally out of equilibriums as a result of natural processes or human activities. These relatively small areas serve as major sinks for particles from riverine and marine sources, and for biogenic carbon formed in situ within estuaries or on the inner shelf. 相似文献
125.
Philip T. King Jacqueline Michel Willard S. Moore 《Geochimica et cosmochimica acta》1982,46(7):1173-1182
228Ra, 226Ra, and 222Rn activities were determined on over 150 ground water samples collected from drilled, public water supply wells throughout South Carolina. A wide range of aquifer lithologies were sampled including the crystalline rocks of the Piedmont and sedimentary deposits of the Coastal Plain. A significant linear relationship between log 228Ra and log 226Ra (n = 182, r = 0.83) was indistinguishable between Piedmont and Coastal Plain ground water. Median activity ratios for the Piedmont, 1.2, and Coastal Plain, 1.3, ground water are close to estimated average crustal activity ratios of 1.2 to 1.5 corresponding to Th/U weight ratios of 3.5 to 4.5. A linear correlation was also found between log 222Rn and log 226Ra for Piedmont (n = 68, r = 0.62) and Coastal Plain (n = 89, r = 0.64) ground water. However, the median activity ratio for Piedmont ground water, 6100, was much higher than for Coastal Plain ground water, 230. Higher excess 222Rn activities may be due to greater retention of 226Ra by the chemically active Piedmont aquifers compared to the more inert sand aquifers sampled in the Coastal Plain. The relationship between log 228Ra and log 226Ra was used to predict total Ra () distributions in Appalachian and Atlantic and Gulf Coastal Plain ground water. Predictions estimate that 2.4% of Appalachian and 5.3% of Atlantic and Gulf Coastal Plain ground water supplies contain total Ra activities in excess of the 5 pCi/l limit established by the U.S. Environmental Protection Agency. These predictions also indicate that 40–50% of these ground water wells may be overlooked using the presently suggested screening activity of 3.0 pCi/l of 226Ra for 228Ra analysis. 相似文献
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Marc Javoy Jacqueline Marette Françoise Pineau 《Geochimica et cosmochimica acta》1973,37(9):2017-2019
Partial fluorination experiments developed on a 26 mg sample of Luna 16 fines show a big 18O enrichment in the first oxygen evolved similar to those observed by Epstein and Taylor on Apollo samples and probably related to the high solar wind content of this sample. 相似文献
128.
Manual cutting of marsh vegetation contaminated by oil spills is often debated as a clean-up technique. Cutting oiled marsh vegetation may be proposed to prevent the oiling of sensitive wildlife associated with marshes. Less frequently, oiled marshes may be cut to aid vegetation recovery. This paper reviews several studies of oiled marsh cutting, and presents a case history of the Grand Eagle oil spill, where marsh cutting was used as a clean-up technique. The paper focuses on the effects of cutting on oiled vegetation survival and structural recovery. We conclude that cutting is often detrimental. Marshes should not be cut when impacted by light oils, where high flushing rates are present, or where re-oiling would be likely. Cutting should only be considered for areas where oil may persist, significant impacts to wildlife are likely, and less destructive clean-up techniques have proven insufficient. Seasonality should be considered prior to cutting, since vegetation impacts may be less likely during fall and winter. Concurrent stresses, such as unusual or extreme salinity or hydrological conditions, should also be considered prior to cutting, to avoid stressing oiled vegetation beyond recovery. Finally, if vegetation cutting is used in marsh environments, substrate disturbance should be avoided. 相似文献
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130.
Jacqueline Clements 《The Australian geographer》2018,49(4):537-552
ABSTRACTLimitations in scale, infrastructure and business opportunities in combination with a greater sense of community in small centres require a more diverse understanding of the small city creative economy. Entrepreneurship and business development builds on non-capitalist resources, creative community initiatives, volunteers and community networks. Fostering the creative economy in small cities requires a rethinking of creative narratives that iterate the key role of non-capitalist community resources. I illustrate this argument via a case study of the Blue Mountains Music Festival, in New South Wales, Australia. It examines the gap between creative economy aspirations of a small city government and the reality of creativity ‘on the ground’. The City of the Blue Mountains is a small urban centre on the fringes of metropolitan Sydney and regional New South Wales. Its council has recently adopted a creative industries approach to enhance local employment in line with national and metropolitan creative agendas. The Blue Mountains Music Festival was launched in response to creative economy policy more than 20 years ago, but has now lost this connection as it fails to fit current policy aspirations. The festival is, however, an effective example of how creativity in a small city unfolds, demonstrating that beyond jobs and growth are key matters of non-capitalist community networks and resources. 相似文献