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811.
812.
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
813.
814.
Modeling photochemistry in the stratosphere requires solution of the equationof radiative transfer over an extreme range of wavelengths and atmosphericconditions, from transmission through the Schumann–Runge bands ofO2 in the mesosphere, to multiple scattering from troposphericclouds and aerosols. The complexity and range of conditions makes photolysiscalculations in 3-D chemical transport models computationally expensive. Thisstudy pesents a fast and accurate numerical method, Fast-J2, for calculatingphotolysis rates (J-values) and the deposition of solar flux in stratosphere.Fast-J2 develops an optimized, super-wide 11-bin quadrature for wavelengthsfrom 177 to 291 nm that concatenates with the 7-bin quadrature (291–850nm) already developed for the troposphere as Fast-J. Below 291 nm the effectsof Rayleigh scattering are implemented as a pseudo-absorption, and above 291nm the full multiple-scattering code of Fast-J is used. Fast-J2 calculates themean ultraviolet-visible radiation field for these 18 wavelength binsthroughout the stratosphere, and thus new species and new cross sections canbe readily implemented. In comparison with a standard, high-resolution,multiple-scattering photolysis model, worst-case errors in Fast-J2 do notexceed 5% over a wide range of solar zenith angles, altitudes(0–60 km), latitudes, and seasons where the rates are important inphotochemistry. 相似文献
815.
A comprehensive physical pattern of land-air dynamic and thermal structure on the Qinghai-Xizang Plateau 总被引:11,自引:1,他引:11
According to the boundary layer observations of three stations (Garze, Damxung and Qamdu) and relevant earth satellite, radiosonde and surface observations during the intensive observational period (IOP) of the second Tibetan (Qinghai-Xizang) Plateau Experiment of atmospheric science (TIPEX), the land-air physical process and dynamic model on the Tibetan Plateau were comprehensively analyzed in this study. The dynamic characteristics of boundary layer and the rules of turbulent motion on the plateau were illustrated. The characteristics of distributions of wind speed and direction with mutiple-layer structure and deep convective mixed layer on the plateau, the strong buoyancy effect in turbulent motion on the plateau on which the air density is obviously smaller than on the plain, and the Ekman spiral and its dynamic pump effect of the plateau deep boundary layer have been found. The local static distribution of water vapor and the horizontal advection of water vapor in the plateau boundary layer were studied. The abnomal thermodynamic structure on the plateau surface and boundary layer, including the plateau strong radiation phenomenon and strong heating source characteristics of the middle plateau, was also analyzed. The authors synthesized the above dynamic and thermodynamic structures of both surface and boundary layers on the plateau and posed the comprehensive physical model of the turbulence and convective mixture mechanism on the plateau boundary layer. The characteristics of formation, development and movement for convective cloud cluster over the plateau influencing floods in the Yangtze River area of China were studied. The conceptual model of dynamic and thermodynamic structures of turbulent motion and convective plume related to the frequent occurrence of "pop-corn-like" cloud system is given as well. 相似文献
816.
学习向量量化(LVQ)在地震和爆破识别中的应用 总被引:2,自引:1,他引:2
介绍了竞争神经网络和学习向量量化(LVQ)算法。此算法应用于对北京及周围地区地震和爆破的识别中,在对38个事件的应用中,得到的结果是,误识为3个,结果较好,说明在识别中是有效的。 相似文献
817.
818.
819.
In the Songnen Plain, China, salinization has become increasingly serious and desertification has increased rapidly since
the middle of the twentieth century, restricting the economic growth of the area and threatening the environment. Many factors
can cause the formation of saline–alkali soil, but none of them explain the origin of the substantial amount of soda that
exists in the basin and its distribution pattern. This paper focuses attention on the relationship between the formation of
saline–alkali soil and neotectonic movement, and the climate–tectonic cycle over the geological history of the region. Data
interpreted by Thematic Mapper for two periods of time have been used to analyze changes in the saline–alkali soil. The results
provide a useful tool for demonstrating the relationship between the saline–alkali soil and neotectonic movement, and for
improving the technology and methods used to protect, manage, exploit and utilize the saline–alkali soil. 相似文献
820.
用焦化废水作补水的循环冷却水系统腐蚀控制实验研究 总被引:1,自引:0,他引:1
焦化废水的排放会带来严重的水污染问题,迫切需要将其资源化,用作循环冷却水的补水是其资源化的重要途径。为了防止给循环冷却水系统带来腐蚀,根据水质稳定理论,采用静态和动态实验相结合的方法,研究了焦化废水作补水的循环冷却水系统腐蚀特性及控制技术。结果表明,焦化废水中的污染物造成的系统腐蚀以点蚀为主,应优先使用磷系沉淀膜型缓蚀技术。通过实验优选出的HEDP+Zn2+复合配方,可在传热面上形成牢固的缓蚀膜,缓蚀率达到85.6%,普通碳钢的腐蚀速率为0.105mm/a,满足《工业循环冷却水处理设计规范》(GB50050-95)的要求。实际循环冷却水系统应用证明,使用该复合配方能在循环水浓缩倍数为2~2.2时,经济有效地解决系统的腐蚀问题,为焦化废水的资源化开辟了一条可行的途径。 相似文献