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Y.L.McHall 《大气科学进展》1992,(3)
The stratospheric worm pools, called the 4-day wave also, are mainly the temperature anomalies in the polar regions of winter hemisphere. It will be shown that their occurrence, propagation speed and specific structure can be explained by the lower frequency coherent heating resulting from the wave interaction in the breaking layers of the stratosphere. Although their vertical phase slope is negligibly small, the warm pools cannot be considered as a barotropic anomaly. 相似文献
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From elements formed in interstellar furnaces to humans peering back at the stars, the evolution of life has been a long, intricate and perhaps inevitable process. Life as we know it requires a planet orbiting a star at just the right distance so that water can exist in liquid form. It needs a rich supply of chemicals and energy sources. On Earth, the combination of chemistry and energy generated molecules that evolved ways of replicating themselves and of passing information from one generation to the next. Thus, the thread of life began. This chart traces the thread, maintained by DNA molecules for much of its history, as it weaves its way through the primitive oceans, gaining strength and diversity along the way. Organisms eventually moved onto the land, where advanced forms, including humans, ultimately arose. Finally, assisted by a technology of its own making, life has reached back out into space to understand its own origins, to expand into new realms, and to seek other living threads in the cosmos. 相似文献
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作者研究三维变系数抛物方程 Douglas交替方向隐格式的稳定性和收敛性。采用 H1能量估计方法 ,证明格式按离散 H1范数是绝对稳定的 ,并且收敛阶为 O(Δ t2 + h2 ) 相似文献
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在南半球赤道地区,太平洋东部沿岸的海面温度相对较冷,这些冷水强烈地影响着赤道大陆气候,在由塔西提/达尔文间不规则的高/低气压所定义的南方诗动的减弱价段,这种气候背景型式强烈地受到改变,在南方涛动减弱阶段,厄尔尼诺事件可能会出现,赤道太平洋水团要比通常温暖。 相似文献
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根据美国国家飓风中心纽曼等人发展的大西洋飓风路径HURRAN模式的思想,我们建立了一个适用于西北太平洋的台风路径客观预报“相似法模式”。依靠四十年台风路径历史资料进行业务试验,结果表明该模式具有可允许的误差范围,且操作简便、计算迅速、效果稳定、可作为西北太平洋台风路径客观预报的一个业务模式投入实际使用。 相似文献
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Metals in contaminated salt marshes are mainly locked in the anaerobic layer of sediments, where they are tightly bound as sulfides and organic complexes. Vascular plants survive in saturated soils in part by pumping O2 into their root zones, changing their microenvironment to an oxic one. This, along with chelating exudates, mobilizes metals, allowing uptake by the roots. We compared the common reed Phragmites australis and cordgrass Spartina alterniflora in lab and field studies for ways in which they handle trace metals. Both plants store most of their metal burden in their roots, but some is transported to aboveground tissues. Spartina leaves contain approximately 2-3 x more Cr, Pb, and Hg than Phragmites leaves, but equivalent Cu and Zn. Furthermore, Spartina leaves have salt glands, so leaf excretion of all metals is twice that of Phragmites. In-depth studies with Hg indicate that Hg excretion correlates with Na release but not with transpiration, which is 2.2 x higher in Phragmites; and that more Hg accumulates in early-appearing leaves than in upper (i.e. later) leaves in both species. Spartina thus makes more metals available to salt marsh ecosystems than Phragmites by direct excretion and via dead leaves which will enter the food web as detritus. 相似文献