Abstract Spectral and spectrally integrated direct beam irradiances measured in Hamilton during the summer of 1981 were used to examine the relationship between the aerosol optical depth τa and Unsworth and Monteith's turbidity coefficient τA, which is a measure of spectrally averaged optical depth. Good correlation was obtained between τa at a wavelength of 0.67 μm and τA, thus confirming experimentally Blanchet's (1982) conclusion from a numerical study. 相似文献
Abstract In the long term, the Kyoto Protocol will be insufficient to stabilize the greenhouse gas (GHG) concentrations in the atmosphere; quantified commitments will also be essential for major developing countries (and the US). International cooperation mechanisms, such as permit trading systems, can help achieve global economic efficiency. However, the initial allocation of emission permits raises many debates on equity. The main objective is to propose a decision aid tool for decision makers, which is capable of providing relevant information on various equitable permit allocation schemes and burden sharing. A dynamic multicriteria model is proposed to share the global quantity of permits among 15 regions, taking into account multiple definitions of equity and regional interests. The World-MARKAL energy model is used to compute the gross reduction cost (before permit exchanges) for each region. Afterward, it is possible to calculate their net reduction costs (after permit exchanges) according to different allocation schemes. A realistic simulation of the tool provides examples of results, i.e. ranges of permit allocations and net costs for each region. Finally, some recommendations are proposed to policy makers to design a decision process adapted to the global context of negotiations. 相似文献
The vertical temperature profile in the atmosphere reflects a balance between radiative and convective processes and interactions with the oceanic and land surfaces. Changes in vertical temperature profiles can affect atmospheric stability, which in turn can impact various aspects of weather systems. In this study, we analyzed recent-past trends of temperature over the Australian region using a homogenized monthly upper-air temperature dataset and four reanalysis datasets (NCEP, ERA-Interim, JRA-55 and MERRA). We also used outputs of 12 historical and future regional climate model (RCM) simulations from the NSW/ACT (New South Wales/Australian Capital Territory) Regional Climate Modelling (NARCliM) project and 6 RCM simulations from the CORDEX (Coordinated Regional Downscaling Experiment) Australasian project to investigate projected changes in vertical temperature profiles. The results show that the currently observed positive trend in the troposphere and negative trend in the lower stratosphere will continue in the future with significant warming over the whole troposphere and largest over the middle to upper troposphere. The increasing temperatures are found to be latitude-dependent with clear seasonal variations, and a strong diurnal variation for the near surface layers and upper levels in tropical regions. Changes in the diurnal variability indicate that near surface layers will be less stable in the afternoon leading to conditions favoring convective systems and more stable in the early morning which is favorable for temperature inversions. The largest differences of future changes in temperature between the simulations are associated with the driving GCMs, suggesting that large-scale circulation plays a dominant role in regional atmospheric temperature change.
The Hackthorne 1 site (southern Tuli Basin, South Africa) is situated on a sand-covered plateau adjacent to the Limpopo River Valley. Although the site is well known for its Stone Age archaeology, the past environmental contexts (particularly sedimentological/geomorphological) are not well known. We examine the Hackthorne sand grain surface textures, so as to provide some insight on the site specific and regional depositional history. Quartz sands at Hackthorne were collected from surface sands and from underlying weathered calcrete. SEM analysis was performed on sand grains, through which several mechanical and chemical microtextures were identified. Microtextures typical of fluvial environments were found only on grains derived from the plateau calcrete host sediment, whilst the surface sands exhibited only textures associated with aeolian environments. The results indicate that the calcrete host sediment is composed of alluvium, and that the surface sands mantling the Hackthorne Plateau are not deflated from the alluvial deposits in the Limpopo Valley, but may rather be derived from distant aeolian sources. The deposition of aeolian sands is consistent with OSL dates which place sand deposition, or remobilization, at 23 and 15 kya, periods in southern Africa associated with increased aridity. 相似文献
Acid saline lake systems in Western Australia may be the best known modern terrestrial analog for the Burns formation on Mars and, thus, provide information about past environments and life on Mars. 相似文献
This study was to investigate the source, mobility and attenuation of As at the New Britannia Mine, Snow Lake, Manitoba. One major source of As contamination was determined to be an arsenopyrite residue stockpile (ARS) containing refractory Au in a waste rock impoundment. It appears that As is still moving through glacial clay at the base of the ARS into a confined aquifer even though the pile was capped in the year 2000. Arsenic is also being mobilized from a deposit of tailings, which formed following spills by previous owners, Nor Acme. Arsenic from the tailings is being mobilized by oxidation of arsenopyrite and reduction of arsenate to the more mobile arsenite by arsenate-reducing bacteria. This contamination is affecting a shallow unconfined aquifer and surface water flowing from the tailings through wetlands towards Snow Lake. Arsenic is being attenuated by adsorption to hydrated ferric oxides (HFO) in the tailings, wetland soils and aquatic plants. Although As in surface water, soils and plants along the flow path from the mine to Snow Lake are above Canadian drinking water guidelines, efficient natural attenuation by HFO in soils and plants of the wetlands have limited the concentration in Snow Lake to below drinking water standards. 相似文献
The overuse of cesarean sections (C-sections) in the United States is a contested issue. The rate of C-section births in 2015 at 32 percent was over double the World Health Organization recommendation of 10 to 15 percent. We employed spatial statistical methods and data visualization techniques to assess the temporal and spatial trends in C-section rates by county across the United States. Although the national rate of C-section remained stable at the beginning and end of this study period, an increase in rates from 1997 to 2009 was reflected simultaneously in national, state, and individual county rates. Local indicators of spatial dependence did not show spatial clustering as being connected to, or driving, the change, yet the visualization methods used here show details on individual county deviance from local temporal trends. By highlighting counties that do not follow the trends of their neighbors, we identify exceptional locations that could help further the study of the determinants of changing C-section rates in the United States. Key Words: cesarean sections, exploratory spatial data analysis, medical geography, spatial statistics.相似文献
