Mid-Century Ensemble Regional Climate Change Scenarios for the Western United States   总被引：3，自引：0，他引：3  

L. Ruby Leung  Yun Qian  Xindi Bian  Warren M. Washington  Jongil Han  John O. Roads 《Climatic change》2004,62(1-3):75-113

To study the impacts of climate change on water resources in the western U.S., global climate simulations were produced using the National Center for Atmospheric Research/Department of Energy (NCAR/DOE) Parallel Climate Model (PCM). The Penn State/NCAR Mesoscale Model (MM5) was used to downscale the PCM control (20 years) and three future(2040–2060) climate simulations to yield ensemble regional climate simulations at 40 km spatial resolution for the western U.S. This paper describes the regional simulations and focuses on the hydroclimate conditions in the Columbia River Basin (CRB) and Sacramento-San Joaquin River (SSJ) Basin. Results based on global and regional simulations show that by mid-century, the average regional warming of 1 to 2.5 °C strongly affects snowpack in the western U.S. Along coastal mountains, reduction in annual snowpack was about70% as indicated by the regional simulations. Besides changes in mean temperature, precipitation, and snowpack, cold season extreme daily precipitation increased by 5 to 15 mm/day (15–20%) along theCascades and the Sierra. The warming resulted in increased rainfall at the expense of reduced snowfall, and reduced snow accumulation (or earlier snowmelt) during the cold season. In the CRB, these changes were accompanied by more frequent rain-on-snow events. Overall, they induced higher likelihood of wintertime flooding and reduced runoff and soil moisture in the summer. Changes in surface water and energy budgets in the CRB and SSJ basin were affected mainly by changes in surface temperature, which were statistically significant at the 0.95 confidence level. Changes in precipitation, while spatially incoherent, were not statistically significant except for the drying trend during summer. Because snow and runoff are highly sensitive tospatial distributions of temperature and precipitation, this study shows that (1) downscaling provides more realistic estimates of hydrologic impacts in mountainous regions such as the western U.S., and (2) despite relatively small changes in temperature and precipitation, changes in snowpack and runoff can be much larger on monthly to seasonal time scales because the effects of temperature and precipitation are integrated over time and space through various surface hydrological and land-atmosphere feedback processes. Although the results reported in this study were derived from an ensemble of regional climate simulations driven by a global climate model that displays low climate sensitivity compared with most other models, climate change was found to significantly affect water resources in the western U.S. by the mid twenty-first century.  相似文献   

Ancient magnetic field determinations on selected chondritic meteorites     

Aviva Brecher  Lindy Leung   《Physics of the Earth and Planetary Interiors》1979,20(2-4):361-378

Paleofield intensity determinations involving a comparison of the stable natural remanence (NRM) component with a laboratory thermoremanence (TRM) were carried out on nine chondrites selected in Brecher and Fuhrman (1979a, this issue, hereafter called Paper I), as well as on two manifestly unsuitable controls. To judge their reliability: (1) heat-alteration was monitored by comparing saturation coercivity spectra before and after heating; and (2) the NRM and TRM intensity and stability were compared to those of residual magnetization following zero-field cooling (TRM₀) from above the Curie point of kamacite (Ni---Fe). The latter criterion separates the role of an external magnetic field (of 0.43 Oe) at cooling from intrinsic contributions to magnetic grain alignments, due to accretionary, metamorphic or shock-oriented petrofabrics.

In some chondrites (e.g., Brownfield, H3B; Holyoke, H4C; Farley, H5A), a surprisingly large (10% NRM) and stable TRM₀ proved so similar to NRM and TRM, that sizeable spurious “paleofields” — comparable to paleointensities obtained — were derived by the standard method for zero-field cooling. In other chondrites, with negligible TRM₀ (1% of NRM) and irregular AF demagnetization curves, more reliable paleofield strengths in the range 0.01–0.09 Oe were obtained (e.g., Cavour, H6C). These seem representative of magnetic fields at the end of metamorphism intervals (10⁷ years after accretion) and/or at post-shock cooling. Thus, field strengths obtained from ordinary chondrites are typically weaker (by factors of 10–100) than those reliably determined from carbonaceous chondrites and ureilites, suggesting temporal decay of nebular magnetic fields, from the end of accretion until the end of metamorphism and early catastrophic-collisional stages.  相似文献   

Oil pollution along coastal areas of Hong Kong     

M.T. Cheung  T.Y. Cheng  S.W. Leung  C.C. Lo  L.M. Mak 《Marine pollution bulletin》1979,10(8):228-231

The level of total hydrocarbon in three chosen sites in Hong Kong was determined over a period of 8 months, September 1977 to April 1978. The range of hydrocarbon content is 3.67 ppb to 11.98 ppb. The level of hydrocarbon in Pacific Ocean is 0.016 ppb. The oil pollution in Hong Kong shoreline waters is 230–750 times higher than deep ocean water, but the level is not yet hazardous.  相似文献   

Structural response to exponentially varying harmonic excitations     

A. Y. T. Leung 《地震工程与结构动力学》1985,13(5):677-681

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Computer aided design of underground excavations in jointed rock     

C. F. Leung 《Rock Mechanics and Rock Engineering》1990,23(2):71-89

Summary Stability analysis of rock blocks that may be formed by excavating jointed rock masses is traditionally performed using the stereographic projection technique. However, such technique is prone to human errors, and existing alternative analytical methods are rather tedious and time consuming. In this paper, a computer aided approach is proposed with the prime objective that the entire analysis is automated on a microcomputer. Computer aided design features such as determination of discontinuity orientation based on borehole data, stability analysis of rock blocks involving multiple discontinuity sets, and determination of optimum excavation direction, optimum plunge of rock reinforcement and the most critical direction of earthquake force are provided.  相似文献   

甲壳胺人工皮—CHIMEHERB治疗不同类型创面初步结果     

李良平  娄培友  陈志伟 《中国海洋大学学报(自然科学版)》1989,(Z3)

本文报告了1989年1月至12月使用甲壳胺人工皮治疗94例不同类型创面,其中手部创伤66例,烧伤5例,其它创面17例。结果断层皮肤损伤愈合良好,小面积全层皮肤损伤愈合后有少量疤痕形成,在手外伤中,以指端损伤效果较好,采用此疗法,方法简单,易于推广。  相似文献   

SAR系统不确定性可视化表达及其应用   总被引：3，自引：0，他引：3  

葛咏 王劲峰梁怡  王贞松 《地球信息科学学报》2003,5(3):86-90

SAR在成像过程中由于受到外界环境干扰和机载本身的不稳定等不确定因素的影响 ,直接影响 SAR图像的使用。因此 ,对这些不确定因素分析是十分重要的。目前 ,对于 SAR不确定性研究主要是基于统计方法 ,但这种方法不便于揭示 SAR不确定性产生的机理 ,以及不确定性可视化表达。本文首先从机理的角度讨论了 SAR成像系统误差传递函数 ,在确定了 SAR系统误差传递函数之后 ,着重讨论了在误差传递函数基础上利用虚拟现实技术和系统仿真技术进行 SAR成像系统不确定可视化研究 ,最后给出可视化表达的应用实例。  相似文献   

Field validation, in Scotland and Iceland, of the artificial mussel for monitoring trace metals in temperate seas     

Leung KM  Furness RW  Svavarsson J  Lau TC  Wu RS 《Marine pollution bulletin》2008,57(6-12):790-800

The artificial mussel (AM), a novel chemical sampling device, has been developed for monitoring dissolved trace metals in marine environments. The AM consists of Chelex-100 suspended in artificial seawater within Perspex tubing and enclosed with semi-permeable polyacrylamide gel at both ends. To validate the field performance of the AM in temperate waters, we deployed AMs alongside transplanted blue mussels Mytilus edulis in coastal environments in Scotland (Holy Loch, Loch Fyne, Loch Striven and Millport) and Iceland (Reykjavikurh?fn, Gufunes, South of thornerney, Hofsvik, Hvalfj?rethur and Sandgerethi) for monitoring trace metals. While uptake patterns of Cd between the AM and M. edulis were highly comparable, discrepancies were found in the accumulation profiles of the other metals (Cu, Cr, Pb and Zn), in particular Zn. Nonetheless, the AMs gave a better resolution to accurately reveal the spatial difference in dissolved metal contamination when compared with M. edulis. AMs complement the use of mussels since AMs indicate dissolved metals in seawater, whereas uptake by mussels indicates a mixture of dissolved and particulate metals. Our results also indicated that historical metal exposure of the transplanted M. edulis could significantly confound their metal concentrations especially when the deployment period was short (i.e. <34d). This study suggested that the AM can overcome problems associated with variable biological attributes and pre-exposure history in the mussel, and provides a standardized and representative time-integrated estimate of dissolved metal concentrations in different marine environments.  相似文献   

Adsorption and desorption behaviors of selected endocrine disrupting chemicals in simulated gastrointestinal fluids     

Ying-heng Fei  Kenneth M.Y. Leung  Xiao-yan Li 《Marine pollution bulletin》2014

An in vitro technique using simulated gastrointestinal (GI) fluids was applied to investigate the desorption of selected endocrine disrupting chemicals (EDCs), i.e. bisphenol A (BPA) and 17 α-ethinylestradiol (EE2), from the marine sediment in the digestive environment. The results show that the GI fluids suppressed chemical adsorption and greatly increased the desorption of BPA and EE2 from the sediment. Pepsin in the gastric fluid would compete for the adsorption sites with the adsorbates, and bile salts in the intestinal fluid had a solubilization effect on the chemicals. The amount of chemical release from the sediment in different fluids followed intestinal (fed) > intestinal (fasted) > gastric > saline water. During the dynamic desorption tests, 62% and 21% of sediment-bound BPA and EE2, respectively, could be released into the simulated GI fluids. The enhanced desorption of EDCs from sediment in the digestive system would make the pollutants more bioavailable in the ecosystem.  相似文献   

The occurrence and ecological risks of endocrine disrupting chemicals in sewage effluents from three different sewage treatment plants,and in natural seawater from a marine reserve of Hong Kong   总被引：1，自引：0，他引：1  

Elvis G.B. Xu  Shan Liu  Guang-Guo Ying  Gene J.S. Zheng  Joseph H.W. Lee  Kenneth M.Y. Leung 《Marine pollution bulletin》2014

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