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991.
本文推导出来悬浮泥沙遥感定量的统一式,其形式包含了Gordon关系式和负指数关系式,其它各悬浮泥沙的关系式可看作是该统一式的近似。由多个例子的计算表明统一式的相关性和精度要高于目前国内外使用的悬浮泥沙定量的遥感模式。该统一式被成功地应用于珠江口伶仃洋的遥感定量分析中。 相似文献
993.
作者在研究中发现水系的展布集中于区域内主要的活动断裂带方向及其正交方向上,并且断裂带活动程度越高,这种集中越明显,在文中,运用岩石破裂试验结果及水系展布受构造活动影响的观点对此进行讨论。 相似文献
994.
995.
An extreme value analysis of the flow of Burbage Brook is carried out by modelling peaks over a high threshold. The aims are to illustrate recently developed statistical techniques and to report on interesting features of the flow of the brook over a 58-year period. Peak flows are found to show marked seasonal variation and a downward trend. Then-year return level is estimated for various values ofn, and the reliability of the estimates is assessed. 相似文献
996.
997.
A sediment budget is constructed for the Lower Mississippi River prior to the introduction of most human modifications. Components of the budget are derived from historical data including Mississippi River Commission hydrographic survey maps for the period from 1877 to 1924. A quantitative estimate of major sediment sources, sinks and storage locations in the Lower Mississippi Valley suggest that the most important sediment source was from bank caving and that at least 50 per cent more sediment was deposited in short-term channel storage than in longer-term overbank storage. The budget indicates that the proportion of sediment transported as bedload was significantly greater than previously estimated. The magnitude and variability of these sediment budget components are discussed. The results of the study suggest that prior to modifications the river was aggrading over much of its length. 相似文献
998.
东亚夏季风每年给中国东部地区带来充沛的降水,是中国水资源的主要来源,同时也常常给中国造成严重的洪涝灾害。东亚夏季风水汽输送的强度、影响范围和持续性在极端暴雨过程中起着关键的作用。这支夏季风气流的水汽输送带可称为东亚季风水汽输送带,与国际上近期提出的"大气河"概念相近,但又不完全相同。东亚夏季风水汽输送带是东亚夏季风最具地区性的特征,也是东亚地区夏季大暴雨和洪涝的制造者。本文根据近百年来的资料,综合评述了东亚夏季风水汽输送带的特征和形成原因,并以海河、黄河、淮河与长江近百年最强的5次持续大暴雨过程为例,分析了季风水汽输送带的重要作用。最后,提出气候变暖可以通过4个方面影响全球水循环,包括气候变暖后大气可容纳更多的水汽、大气环流发生变化、辐射强迫改变以及气溶胶影响的区域性等,这些变化都会对季风水汽输送带产生重要影响。 相似文献
999.
Zinzuni Jurado-Chichay Scott K. Rowland George P. L. Walker 《Bulletin of Volcanology》1996,57(7):471-482
Pyroclastic cones along the southwest coast of Mauna Loa volcano, Hawai'i, have a common structure: (a) an early formed circular outer rim 200–400 m in diameter composed mostly of scoria and lapilli, and (b) one or more later-formed inner rims composed almost exclusively of dense spatter. The spatter activity locally fed short lava flows that ponded within the outer rims. Based on various lines of evidence, these cones are littoral in origin: relationships between the cones and associated flows; the degassed nature of the pyroclasts; and (although not unequivocal) the position of the cones relative to known eruptive vent locations on Mauna Loa. Additional support for the littoral interpretation comes from their similarity to (smaller) littoral cones that have been observed forming during the ongoing Kilauea eruption. The structure of these Mauna Loa cones, however, contrasts with that of standard Hawaiian littoral cones in that there is (or once was) a complete circle of pyroclastic deposits. Furthermore, they are large even though associated with tubefed phoehoe flows instead of 'a'. The following origin is proposed: An initial flow of tube-fed phoehoe into the ocean built a lava delta with a base of hyaloclastite. Collapse of an inland portion of the active tube into the underlying wet hyaloclastites or a water-filled void allowed sufficient mixing of water and liquid lava to generate strong explosions. These explosions broke through the top of the flow and built up the outer scoria/lapilli rims on the solid carapace of the lava delta. Eventually, the supply of water diminished, the explosions declined in intensity to spattering, and the initial rim was filled with spatter and lava. 相似文献
1000.
A 911-m-long sediment core from Lake Biwa, Japan, provides a record of organic matter delivery and accumulation in this large lake during a succession of tectonic and climatic changes dating back to the latest Pliocene. Sediments deposited since 430 ky are profundal; older sediments vary in setting between shallow-water and fluviodeltaic conditions, with occasional deep-water intervals. C/N ratios identify algal production as the dominant source of organic matter throughout the core, although the proportion of land-derived contributions episodically increases in the fluviodeltaic and shallow-water sediments. Rates of organic matter delivery and burial in lake sediments change in response to glacial-interglacial climate changes over the past 430 ky. Sediments deposited during interglacial intervals have organic carbon mass accumulation rates up to 9 times greater than those from glacial intervals, reflecting interglacial climates that were wetter than glacial climates. Algal production of organic matter increased during interglacial times because of greater wash-in of soil nutrients, and organic matter preservation was enhanced because of faster sedimentation rates. 相似文献