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41.
Aiguo Dai W. M. Washington G. A. Meehl T. W. Bettge W. G. Strand 《Climatic change》2004,62(1-3):29-43
The Parallel Climate Model (PCM) has been used in the Accelerated ClimatePrediction Initiative (ACPI) Program to simulate the global climateresponse to projected CO2, sulfate, and other greenhouse gasforcingunder a business-as-usual emissions scenario during the 21st century. In these runs, the oceans were initialized to 1995 conditions by a group from the Scripps Institution of Oceanography and other institutions. An ensemble of three model runs was then carried out to the year 2099 using the projected forcing. Atmospheric data fromthese runs were saved at 6-hourly intervals (hourly for certain criticalfields) to support the ACPI objective of accurately modeling hydrologicalcycles over the western U.S. It is shown that the initialization to1995 conditions partly removes the un-forced oceanic temperature and salinity drifts that occurred in the standard 20th century integration. The ACPI runs show a global surface temperature increase of 3–8 °C over northern high-latitudes by the end of the 21st century, and 1–2 °C over the oceans. This is generally within ±0.1°Cof model runs without the 1995 ocean initialization. The exception is in theAntarctic circumpolar ocean where surface air temperature is cooler in theACPI run; however the ensemble scatter is large in this region. Althoughthe difference in climate at the end of the 21st century is minimalbetween the ACPI runs and traditionally spun up runs, it might be largerfor CGCMs with higher climate sensitivity or larger ocean drifts. Ourresults suggest that the effect of small errors in the oceans (such asthose associated with climate drifts) on CGCM-simulated climate changesfor the next 50–100 years may be negligible. 相似文献
42.
山西省主要河流流域面雨量预报业务流程 总被引:3,自引:1,他引:3
以T213、HLAFS模式、MM5中尺度模式输出的格点资料以及日本降水量格点资料为基础,将影响山西降水的天气动力模型归纳为诊断模型,从中引出多个能够全面反映降水模型特征的综合物理因子;根据各种数值模式输出的降水量预报性能和质量优劣特点,依据数值模式的形势场预报优于要素场预报的现实,构造在不同环流形势背景下,启动不同预报方程的面雨量预报业务流程,有效地遏止了在环流形势调整时预报输出不能快速响应的弱点,提高了点和面雨量预报的准确度。 相似文献
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Coastline configuration and geomorphologic development mode of arc-shaped coast in South China 总被引:1,自引:0,他引:1
1IntroductionArc-shaped bays are quite common on exposed sediment coast in South China, where the crenulate-bay beaches occur with the presence of two consecutive headlands and a predominant wave approach oblique to the alignment of the upcoast and downcoast headlands (Yasso, 1965). Oblique persistent swell striking a shoreline transports sediment alongshore and sculptures a coast into arc-shaped beaches. The shoreline of beach appearance mainly consists of straight segment and shadow segment… 相似文献
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46.
Geochemistry and occurrence of inorganic gas accumulations in Chinese sedimentary basins 总被引:15,自引:0,他引:15
Inorganic gases are commonly seen in eastern China and occasionally in southern China from the shallow water columns above hot and cold springs. The gases contain 68% to nearly 100% CO2, with δ13CCO2 and δ13C1 values in the range of −1.18‰ to −6.00‰ and −19.48‰ to −24.94‰, respectively. All of the 34 large inorganic CO2 and one inorganic methane accumulations discovered in China are distributed in eastern parts of the country, from both onshore and continental shelf basins. No commercial inorganic gas accumulation has been found in central and western China. This is a review of the occurrence and geochemical characteristics of inorganic gas accumulations in Chinese sedimentary basins. A detailed study of gas samples collected from four representative inorganic CO2 pools and one possible inorganic methane pool indicates that inorganic alkane gases typically show δ13C1 values greater than −10‰ versus PDB (mostly −30‰), with a positive stable carbon isotope sequence of δ13C1 < δ 13C2 < δ13C3 < δ 13C4. In contrast, the δ13C1 values of biogenic alkane gases are lighter than −30‰, with a negative isotope sequence (i.e. δ13C1 > δ13C2 > δ 13C3 > δ13C4). Inorganic gases also tend to show less negative δ13CCO2 values (−10‰) than biogenic gases (<−10‰). 相似文献
47.
Mineralogy and geochemistry of a Late Permian coal in the Dafang Coalfield, Guizhou, China: influence from siliceous and iron-rich calcic hydrothermal fluids 总被引:16,自引:2,他引:16
Shifeng Dai Chen-Lin Chou Mei Yue Kunli Luo Deyi Ren 《International Journal of Coal Geology》2005,61(3-4):241-258
This paper describes the influence of siliceous and iron-rich calcic low-temperature hydrothermal fluids (LTHF) on the mineralogy and geochemistry of the Late Permian No. 11 Coal (anthracitic, Rr=2.85%) in the Dafang Coalfield in northwestern Guizhou Province, China. The No. 11 Coal has high contents of vein ankerite (10.2 vol.%) and vein quartz (11.4 vol.%), with formation temperatures of 85 and 180 °C, respectively, indicating that vein ankerite and vein quartz were derived from low-temperature calcic and siliceous hydrothermal fluids in two epigenetic episodes. The vein quartz appears to have formed earlier than vein ankerite did, and at least three distinct stages of ankerite formation with different Ca/Sr and Fe/Mn ratios were observed.The two types of mineral veins are sources of different suites of major and trace metals. Scanning electron microscope and sequential extraction studies show that, in addition to Fe, Mg, and Ca, vein ankerite is the dominant source of Mn, Cu, Ni, Pb, and Zn in the coal, and the contents of these five elements are as high as 0.09% and 74.0, 33.6, 185, and 289 μg/g, respectively. In contrast, vein quartz is the main carrier mineral for platinum-group elements (PGEs) Pd, Pt, and Ir in the coal, and the contents of Pd, Pt, and Ir are 1.57, 0.15, and 0.007 μg/g, respectively. Sequential extraction showed a high PGE content in the silicate fraction, up to 10.4 μg/g Pd, 1.23 μg/g Pt, and 0.05 μg/g Ir, respectively. It is concluded that the formation of ankerite and quartz and the anomalous enrichment of trace elements in the No. 11 Coal in the Dafang Coalfield, Guizhou, result from the influx of calcic and siliceous low-temperature hydrothermal fluids. 相似文献
48.
最近30年来,北冰洋海冰和海水发生了急剧变化:海冰覆盖面积减少、冰层变薄、水温升高、淡水输入增加、污染加剧,正威胁着现有与海冰关系密切的生态系统。预期随着变化的持续,与海冰相关的食物链将在部分海域消失并被较低纬度的海洋物种所取代、总初级生产力有望增加并为人类带来更多的渔获量、而北极熊和海象等以海冰作为栖息和捕食场所的大型哺乳动物的生存前景堪忧。今后人类将更为重视对北冰洋生态环境变化规律的认识并加以运用、关注北冰洋特有物种的命运并加以力所能及的保护、评估北冰洋生态系统的变化对人类社会经济的影响以期及早采取应对措施。数据积累是目前制约北极研究的最大障碍,但随着 SEARCH 等大型国际研究计划的实施,对北冰洋生态系统的监测和研究将更为系统和全面。 相似文献
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50.
The cracked chevron notched Brazilian disc (CCNBD) specimen has been suggested by International Society for Rock Mechanics for measuring mode I fracture toughness of rocks. Subsequently, this specimen geometry has been widely extended to conduct mixed mode fracture tests on rocks as well. A straight through crack front during the fracturing process upon the root of the chevron notch is assumed in the testing principle, but has never been thoroughly evaluated before. In this study, for the first time, the progressive rock fracture mechanism of the CCNBD rock specimen under mixed mode loading is numerically simulated. Specimens under representative mixed mode loading angles are modelled; and the assumption of the straight through crack front growth is critically assessed. The results show that not only the notch tip but also the saw-cut chevron notch cracks during the experiments, yielding a prominent twisted front, far from being straight. The crack front never grows up to the root of the notch ligament and the straight through crack front assumption is never satisfied in the realistic rock fracture progress of this chevron notched specimen subjected to mixed mode loads. In contrast, the fracture progress features typical three-dimensional wing cracking towards the loading ends. The numerically observed progressive fracture mechanism reveals that the measuring principle of mixed mode fracture tests employing CCNBD specimens is significantly violated and the measures of both modes I and II fracture toughness are uncertain. 相似文献