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71.
The spatial distribution of snow cover on the central Arctic sea ice is investigated here based on the observations made during the Third Chinese Arctic Expedition. Six types of snow were observed during the expedition: new/recent snow, melt-freeze crust, icy layer, depth hoar, coarse-grained, and chains of depth hoar. Across most measurement areas, the snow surface was covered by a melt-freeze crust 2-3 cm thick, which was produced by alternate strong solar radiation and the sharp temperature decrease over the summer Arctic Ocean. There was an intermittent layer of snow and ice at the base of the snow pack. The mean bulk density of the snow was 304.01±29.00 kg/m3 along the expedition line, and the surface values were generally smaller than those of the subsurface, confirming the principle of snow densification. In addition, the thicknesses and water equivalents of the new/recent and total-layer snow showed a decreasing trend with latitude, suggesting that the amount of snow cover and its spatial variations were mainly determined by precipitation. Snow temperature also presented significant variations in the vertical profile, and ablation and evaporation were not the primary factors in the snow assessment in late summer. The mean temperature of the surface snow was 2.01±0.96°C, which was much higher than that observed in theinterface of snow and sea ice. 相似文献
72.
Abstract This work makes explicit an algebraic expression giving the matrix of transient influence coefficients associated with a one-dimensional semi-confined aquifer model. The domain studied is divided into a series of connected and completely mixed compartments over which the governing equation is discretized. The discrete equations obtained are solved for the compartmental hydraulic head and used to derive the algebraic expression in question. The basic properties of the so-called algebraic influence coefficients are investigated. In particular, their consistency with the exact Green function is highlighted. Finally, the newly derived influence coefficients are applied to a simplified aquifer system in order to formulate and solve the problem of identifying illegal groundwater pumping. 相似文献
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Hydrogeochemical and isotopic study of groundwater in the Habor Lake Basin of the Ordos Plateau,NW China 总被引:2,自引:2,他引:0
Lihe Yin Guangcai Hou Yan Dou Zhengping Tao Ying Li 《Environmental Earth Sciences》2011,64(6):1575-1584
Hydrogeochemistry and isotopes were used to understand the origin and geochemical evolution in the Habor Lake Basin, northwestern
China. Groundwater samples were taken, and the isotopic compositions δD, δ18O and major ions were analyzed. The groundwater can be divided into three types: the Quaternary groundwater, the shallow Cretaceous
groundwater and the deep Cretaceous groundwater. The groundwater chemistry is mainly controlled by the feldspar weathering
and dolomite weathering, the dissolution of Glauber’s salt, and cation exchange. Chemistry of lake water is mainly controlled
by evaporation and precipitation. The stable isotopes of oxygen and hydrogen in groundwater cluster along the local meteoric
water line, indicating that groundwater is of meteoric origin. Comparing with shallow groundwater, deep groundwater is depleted
in heavy isotopes indicating that deep groundwater was recharged during late Pleistocene and Holocene, during which the climate
was more wetter and colder than today. 相似文献
77.
深层气理论分析和深层气潜势研究 总被引:9,自引:3,他引:9
近年来的一些文献表述深层气时在"深层"和"深部"名词概念上容易造成不必要的费解。就沉积层而言,宜将生油主带(生油窗)作为"深"的界限,从此界限开始到基底以上地层范围的天然气统统称为"深层气";就整个地球而言,宜将沉积层结晶基底和该基底以下的天然气统统称为"深部气"。当然,还应更多地注意来源于深部"深生浅储"的"深层气"。深层气的形成与地壳烃类形成的垂直分带性有关。在一定的历史时期和一定的沉积盆地油气形成分带性理论对勘探实践发挥了一定的指导作用,随着油气地质科研和勘探实践的发展,人们逐渐发现了油气形成分带性理论中油相消失和气相生成带开始门限指标的局限性。不同盆地有不同深度的生油主带,因而也有不同深度范围生气主带(干气带)。腐泥型有机质的演化需要更高的活化能,而需更高的温度和更大的深度,其生气主带深于腐殖型有机质源岩层的位置。生气主带有机质演化受多种因素控制,其中温度、深度和时间是重要因素,引起深层温度升高的条件有地球动力和深部热流等。古生界以前的重大生物地质事件为深层气形成准备了有机质及其演化条件,从物质基础上讲,深层气有巨大的资源潜势。油气形成的地球动力学观点及其他新观点为研究深层气提供了新的思路,岩石圈的烃类资源远未枯竭,被发现和开采的资源仅是其中的一部分,更多的需在深部去发掘。 相似文献
78.
“东半球空间环境地基综合监测子午链”(简称子午工程)是我国空间科学领域开工建设的第一个国家重大基础设施项目。子午工程利用沿东半球120°E子午线附近和北纬30°N附近的15个综合性观测台站,运用无线电、地磁、光学和探空火箭等多种探测手段,连续监测地球表面20—30km以上到几百公里的中高层大气、电离层和磁层,以及十几个地球半径以外的行星际的空间环境参数。它将为我国各类用户提供完整、连续、可靠的多学科、多层次的空间环境地基综合监测数据。子午工程总投资1.67亿元,建设期3年,子午工程整体科学寿命预计超过11年。 相似文献
79.
世界天然气水合物研究开发现状和前景 总被引:77,自引:1,他引:76
回顾了世界天然气水合物研究历史,分析了世界气水合物研究现状和开发前景,评价了全球天然气水合物资源潜势,提出了我国对天然气水合物的研究策略。 相似文献
80.
机载雷达定量测雨中雨滴谱参数的优化 总被引:2,自引:0,他引:2
机载雷达可以方便地跟踪观测对象,并且可以观测某些地基雷达较难观测的区域(如海洋),因此近年来在大气遥感领域得到越来越广泛的应用。为了获得一个较好的地面分辨率,机载雷达使用X波段的衰减频率。虽然雷达波受到的衰减通过算法可以进行订正,但由于雨滴谱的范围较宽,使得利用Z-R或k-R经验公式来确定雨强仍具有较大的不确定性。该文应用在西太平洋进行的国际大型科学考察实验TOGA/COARE中1993年1月和2月间取得的机载雷达实测数据进行定量测雨中雨滴谱参数优化的尝试。 相似文献