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991.
992.
初步分析中国科学院南海海洋研究所《实验3号》科学考察船在TOGA—COARE IOP连续三个航次中部分CTD和ADCP原始观测资料指出:90-210m间大于35的盐度极值除存在准日周期变化外,在量值上还存在约73d的周期变化。但受资料长度的限制,目前尚无法确定上述周期是否属于稳定周期。在上述深度范围内亦存在较低盐度和温度水体侵入现象,其强度存在10—15d的周期变化。等温线和等密度线常出现振幅达10m以上,周期约3d的振荡,而且有时表现出次中尺度涡(submesoscale eddy)及涡旋链特征。比较风、SST、混合层深度间的关系时发现,风强度和大风维持时间对SST和混合层深度的影响很大,如西风暴发过程可使平均SST降低0.5℃左右,使平均混合层深度加深8m以上。分析西风暴发过程及西风暴发后洋流铅垂变化和洋流随时间变化发现,西风暴发过程导致79m以浅深度上的东向射流,且19m深处流动随时间顺时针改向,79m深处流动随时间逆时针方向改向。 相似文献
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采用合成分析和动力诊断分析及统计方法,利用NCEP资料和常规气象观测资料对造成2009年9月6-20日河南省北中部地区15d连阴雨天气成因进行分析。结果表明:200hPa高空急流的出现并且维持,南亚高压的偏东偏北,副热带高压的偏西略偏北,以及边界层的东北风(或偏东风),是造成此次长连阴雨天气的主要影响因素;200hPa东亚西风急流的正异常与对流层中上层(300hPa)的暖异常在动力关系上相互匹配;湿层浅薄,水汽条件不充沛,冷空气影响的层次偏低是造成连阴雨天气累计降水量偏小的可能原因;温度距平随高度递增使得高云量增加,是形成日照偏少、气温明显偏低的可能原因。 相似文献
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Geochemistry of the Jurassic Mirdita Ophiolite (Albania) and the MORB to SSZ evolution of a marginal basin oceanic crust 总被引:7,自引:0,他引:7
The Middle Jurassic Mirdita Ophiolite in northern Albania is part of an ophiolite belt occurring between the Apulian and Pelagonian subcontinents in the Balkan Peninsula. The upper mantle and crustal units of the Mirdita Ophiolite show major changes in thickness, rock types, and chemical compositions from west to east as a result of its complex evolution in a suprasubduction zone (SSZ) environment. The 3–4-km-thick Western Mirdita Ophiolite (WMO) includes lherzolite–harzburgite, plagioclase–lherzolite, plagioclase–dunite in its upper mantle units and a plutonic complex composed of olivine gabbro, troctolite, ferrogabbro, and gabbro. These peridotites and gabbroic rocks are overlain directly by a 600-m-thick extrusive sequence containing basaltic pillow lavas and hyaloclastites. Sheeted dikes are rare in the WMO. The 12-km-thick Eastern Mirdita Ophiolite (EMO) includes tectonized harzburgite and dunite with extensive chromite deposits, as well as ultramafic cumulates including olivine clinopyroxenite, wehrlite, olivine websterite, and dunite forming a transitional Moho with the overlying lower crustal section. The plutonic rocks are made of pyroxenite, gabbronorite, gabbro, amphibole gabbro, diorite, quartz diorite, and plagiogranite. A well-developed sheeted dike complex has mutually intrusive relations with the underlying isotropic gabbros and plagiogranites and feeds into the overlying pillow lavas. Dike compositions change from older basalt to basaltic andesite, andesite, dacite, quartz diorite, to late-stage andesitic and boninitic dikes as constrained by crosscutting relations. The 1.1-km-thick extrusive sequence comprises basaltic and basaltic andesitic pillow lavas in the lower 700 m, and andesitic, dacitic and rhyodacitic massive sheet flows in the upper 400 m. Rare boninitic dikes and lavas occur as the youngest igneous products within the EMO. The basaltic and basaltic andesitic rocks of the WMO extrusive sequence display MORB affinities with Ti and Zr contents decreasing upsection (TiO2 = 3.5–0.5%, Zr = 300–50 ppm), while Nd(T) (+ 8 to + 6.5) varies little. These magmas were derived from partial melting of fertile MORB-type mantle. Fractional crystallization was important in the evolution of WMO magmas. The low Ti and HREE abundances and Cs and Ba enrichments in the uppermost basaltic andesites may indicate an increased subduction influence in the evolution of the late-stage WMO magmas. Basaltic andesites in the lower 700 m of the EMO volcanic sequence have lower TiO2 ( 0.5%) and Zr ( 50 ppm) contents but Nd(T) values (+ 7 to + 6.5) are similar to those of the WMO lavas. These rocks show variable enrichment in subduction-enriched incompatible elements (Cs, Ba, Th, U, LREE). The basaltic andesites through dacites and boninites within the upper 400 meters of EMO lavas show low TiO2 ( 0.8–0.3%) and Nd(T) (+ 6.5 to + 3.0). The mantle source of these rocks was variably enriched in Th by melts derived from subducted sediments as indicated by the large variations in Ba, K, and Pb contents. EMO boninitic dikes and lavas and some gabbroic intrusions with negative Nd (T) values (− 1.4 and − 4.0, respectively) suggest that these magmas were produced from partial melting of previously depleted, ultra-refractory mantle. The MORB to SSZ transition (from west to east and stratigraphically upwards in the Mirdita Ophiolite and the progression of the Nd(T) values from + 8.0 to − 4.0 towards the east resulted from an eastward shift in protoarc–forearc magmatism, keeping pace with slab rollback in this direction. The mantle flow above the retreating slab and in the arc-wedge corner played a major role in the evolution of the melting column, in which melt generation, aggregation/mixing and differentiation occurred at all levels of the sub-arc/forearc mantle. The SSZ Mirdita Ophiolite evolved during the intra-oceanic collapse and closure of the Pindos marginal basin, which had a protracted tectonic history involving seafloor spreading, protoarc rifting, and trench-continent collision. 相似文献
996.
本文探讨用相对论喷流模型解释BL Lac天体0716+71从射电到γ射线的整修电磁波段的非热辐射。喷流的结构分两个区域描述:内区具有抛物线结构,喷流是加速的;外区具有圆锥形结构,喷流速度恒定。相对论电子的密度和最高能量,以及磁场等参数随距离向外按幂律下降。在此模型中,射电至紫外线起源于相对论电子的同步辐射,而高能的X射线和γ射线则起源于自康普顿散射。辐射的频率越高,产生区域越靠近中央能源机器。辐射 相似文献
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结合传统水准测量的手段,介绍了一种海滩剖面监测的可行方案,并给出了数据处理方法,为威海核电厂工程的选址提供了参考. 相似文献
1000.
中国地壳运动观测网络基准站重力场变化的海潮负荷信号改正问题 总被引:7,自引:0,他引:7
利用最新的全球海潮模型(Csr3.0,Fes95.2,Tpxo2和Csr4.0)和原有的Schwiderski海潮模型以及中国近海海潮数据和标准地球模型负荷格林函数,采用直接褶积积分方法研究了中国地壳运动观测网络25个基准站重力固体潮观测中的海潮负荷效应问题,计算了 8个主要潮汐波的负荷振幅和相位,构制了北京和上海等10个台站重力负荷随时间变化函数。 相似文献