Periodic variation of the north-south asymmetry of solar activity phenomena     

V. K. Verma 《Journal of Astrophysics and Astronomy》2000,21(3-4):173-176

We report here a study of various solar activity phenomena occurring in both north and south hemispheres of the Sun during solar cycles 8–23. In the study we have used sunspot data for the period 1832–1976, flare index data for the period 1936-1993, Hα flare data 1993–1998 and solar active prominences data for the period 1957–1998. Earlier Verma reported long-term cyclic period in N-S asymmetry and also that the N-S asymmetry of solar activity phenomena during solar cycles 21, 22, 23 and 24 will be south dominated and the N-S asymmetry will shift to north hemisphere in solar cycle 25. The present study shows that the N-S asymmetry during solar cycles 22 and 23 are southern dominated as suggested by Verma.  相似文献   

Recent increase of DIC in the western North Pacific     

Tsuneo Ono  Yutaka W. Watanabe  Shuichi Watanabe   《Marine Chemistry》2000,72(2-4)

The temporal variation of the total dissolved inorganic carbon (DIC) content in the western North Pacific is investigated by comparing the DIC distribution obtained from the data sets of three different periods, the GEOSECS data observed in 1973, the CO₂ dynamics Cruise data observed in 1982, and recent Japanese data sets observed during the early 1990s. The overall feature of the signal of temporal DIC change during 1973 and early 1990s agreed with that of former studies, and did not significantly change with the calculation scheme (the grid-selection method vs. the multiple regression method). The observed increase in DIC among the different time scales showed a good inner consistency, which also indicates the stability of the method used in the DIC change calculation. The apparent rate of increase of the DIC inventory in the upper 1000 m water column, however, differed significantly by the data set used for the calculation: It was 5.6±2.4 g C/m²/year, based on the data comparison between 1982 and the early 1990s, while it became 7.6±2.4 g C/m²/year when based on the data between 1973 and the early 1990s. This result provides us an information about the data-dependency on the former estimation of temporal DIC change.  相似文献   

辽西金-羊盆地土城子组层序地层学   总被引：2，自引：2，他引：0  

邢德和  孙春林  孙跃武  张立东  郭胜哲  张长捷  彭艳东  贾斌  陈树旺  丁秋红 《地质与资源》2006,15(3):166-173

辽西金-羊（金岭寺-羊山）盆地土城子组为一套红色陆相碎屑岩组合.据其岩层垂向叠置规律及不整合面特征,可划分出3个Ⅲ级旋回层序,14个Ⅳ级旋回层序及各旋回层序所对应的冲积扇、滨湖、浅湖、最大湖泛面、风成沙漠沉积体系.这些沉积体系的有规律叠置,构成了土城子期3次湖扩张-湖萎缩沉积序列,其顶、底为明显的不整合面所界定.通过对旋回层序的划分和对比,建立了辽西金-羊盆地土城子组层序地层格架,从而揭示了中生代侏罗纪上统土城子组沉积期的盆地演化规律.  相似文献   

黄河上游径流丰枯变化特征及其环流背景   总被引：7，自引：4，他引：3  

蓝永超  沈永平  林纾  张世强  畅俊杰 《冰川冻土》2006,28(6):950-955

为了揭示影响黄河上游径流丰枯变化的气候因子,为径流的长期、超长期预报与水资源的规划利用提供依据,利用相关台站的降水、径流观测资料,分析了黄河上游汛期径流的丰枯变化特征及其环流背景.结果表明:黄河上游(唐乃亥以上)流域丰、枯水段基本上是交替出现的,总体上枯水持续时间多于丰水,一个完整的丰枯循环周期大约在18 a左右.黄河上游径流的丰、枯,与大气环流的异常有着非常密切的关系,其中,西太平洋副热带高压偏西、偏强、偏北,青藏高原中部地区有西风槽存在是黄河上游汛期降水偏多、径流偏丰的两个重要因素.因此,基于汛期流量的丰枯与其所对应的环流背景之间的联系,可根据前期环流的演变特征对黄河上游汛期流量的丰枯做出大致预测.  相似文献   

认识偏心率周期的地层古气候意义   总被引：15，自引：0，他引：15  

李前裕  田军  汪品先 《地球科学》2005,30(5):519-528

介绍了偏心率周期在地层和古气候研究方面的新发展.现有地球轨道模式对250Ma以来的轨道运算误差能控制在0.2%之内, 使基于偏心率周期来划分地层年代成为可能.新的国际标准地层年代表以405ka长偏心率周期为基础来划分主要地层界线.新生代将包括E1-E162偏心率长周期, 底界年龄(65.5±0.3) Ma.这一地层年代表的建立, 标志着轨道地层学时代的到来.偏心率的100ka短周期和405ka长周期在诸多地质记录中都有反映, 特别是来自深海钻孔的物理化学古气候指标.很多古气候重大事件往往发生在偏心率周期的弱振幅时期, 表明弱振幅时期易受其他因素的干扰影响, 这些因素包括碳储库、冰盖和海平面变化、电磁场, 以及区域构造重组等等.越来越多的研究发现碳同位素在偏心率周期上与地球轨道驱动相关, 且常领先于氧同位素的变化, 表明热带碳循环过程是影响全球气候变化的关键因素之一.   相似文献   

Hydrograph separation to improve understanding of Dissolved Organic Carbon Dynamics in Headwater catchments          下载免费PDF全文

V. Chaplot  O. Ribolzi 《水文研究》2014,28(21):5354-5366

Dissolved organic carbon (DOC) is a key component of the global carbon cycle, but, to date, large uncertainties still exist on its source and fate in first‐order streams. In a 23 ha rangeland and steep‐slope headwater of South Africa, our aim was to quantify the contribution of overland flow (OF), soil water (SW) and ground water (GW) to DOC fluxes (DOC_F), and to interpret the results in terms of DOC sources and fate. The average 2010–2011 DOC concentration (DOC_C) at the catchment outlet was 4.7 mg C l^?1 with a standard error of ±2.5 mg C l^?1, which was significantly lower than in SW (15.2 ± 1.6 mg C l^?1) and OF (11.9 ± 0.8 mg C l^?1), but higher than in GW (2.3 ± 0.6 mg C l^?1). Based on end‐member mixing using Si and Na concentration in the water compartments, the average SW contribution to DOC_F was 66.4%, followed by OF (30.0%) and GW (3.6%). The resulting estimated DOC_F at the catchment outlet was 8.05 g C m² y^?1. This was much higher than the observed value of 2.80 g C m² y^?1, meaning that 5.25 g C m² y^?1 or 65% of the DOC is lost during its downslope and/or downstream transport to the catchment outlet. Complementary investigations revealed that the DOC_C in SW dropped from 15.2 ± 1.6 to 2.6 ± 0.3 mg C l^?1 during its downslope transport to the river system, which corresponded to a net loss of 5.10 g C m² y^?1, or 97% of the catchment DOC losses. These results on DOC sources and potential fate in headwaters are expected to improve our understanding of the impact of hydrology on the global C‐cycle. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Influence of melt‐freeze‐cycles on the radionuclide transport in homogeneous laboratory snowpack          下载免费PDF全文

Kerstin Hürkamp  Stefanie Tafelmeier  Jochen Tschiersch 《水文研究》2017,31(6):1360-1370

Radionuclides released to the environment and deposited with or onto snow can be stored over long time periods if ambient temperature stays low, particularly in glaciated areas or high alpine sites. The radionuclides will be accumulated in the snowpack during the winter unless meltwater runoff at the snow base occurs. They will be released to surface waters within short time during snowmelt in spring. In two experiments under controlled melting conditions of snow in the laboratory, radionuclide migration and runoff during melt‐freeze‐cycles were examined. The distribution of Cs‐134 and Sr‐85 tracers in homogeneous snow columns and their fractionation and potential preferential elution in the first meltwater portions were determined. Transport was associated with the percolation of meltwater at ambient temperatures above 0 °C after the snowpack became ripe. Mean migration velocities in the pack were examined for both nuclides to about 0.5 cm hr^?1 after one diurnal melt‐freeze‐cycle at ambient temperatures of ?2 to 4 °C. Meltwater fluxes were calculated with a median of 1.68 cm hr^?1. Highly contaminated portions of meltwater with concentration factors between 5 and 10 against initial bulk concentrations in the snowpack were released as ionic pulse with the first meltwater. Neither for caesium nor strontium preferential elution was observed. After recurrent simulated day‐night‐cycles (?2 to 4 °C), 80% of both radionuclides was released with the first 20% of snowmelt within 4 days. 50% of Cs‐134 and Sr‐85 were already set free after 24 hr. Snowmelt contained highest specific activities when the melt rate was lowest during the freeze‐cycles due to concentration processes in remaining liquids, enhanced by the melt‐freeze‐cycling. This implies for natural snowpack after significant radionuclide releases, that long‐time accumulation of radionuclides in the snow during frost periods, followed by an onset of steady meltwater runoff at low melt rates, will cause the most pronounced removal of the contaminants from the snow cover. This scenario represents the worst case of impact on water quality and radiation exposure in aquatic environments.  相似文献   

松辽盆地嫩江组凝缩层形成机制及其地质意义     

张晨晨  张顺  魏巍  吴朝东 《沉积学报》2015,33(5):891-898

本文应用层序地层学、沉积地质学及盆地动力学分析方法,阐述了松辽盆地嫩江组凝缩层形成机制及其意义。松辽盆地嫩江组底部发育10~15 m厚的凝缩层,其形成机制是在嫩江组强制性水退旋回作用下导致湖盆萎缩,在进积型层序远端湖相区形成浓缩水体的高盐度还原环境,由此沉积了以油页岩为标志、以钟形高电阻为特征的凝缩层。该凝缩层底界面以SB₀₇最大湖泛面为等时边界,向上包含了进积型层序较长的时间跨度,不具等时性,同时来自东部物源向西的强烈进积堵塞了海侵通道,也使松辽盆地嫩江组发生过"海侵事件"的推论无法成立。因此,凝缩层形成机制的认识在松辽盆地层序地层学和沉积地质学领域具有重要的意义。成藏分析认为嫩江组凝缩层既是烃源岩也是区域性盖层,在其上下蕴藏着丰富的油气资源,同时由于强制性水退型层序在钻井及地震上具有易于识别的结构特点,是含油气盆地评价及层系优选的结构性标志。因此,凝缩层的认识不论在层序地层、沉积环境及成藏分析方面都具有重要的理论和实际意义。  相似文献   

干湿交替下水分及氯离子在混凝土中传输的细观数值模拟   总被引：1，自引：0，他引：1       下载免费PDF全文

鲍玖文  王立成 《海洋工程》2014,32(1):68-74

氯离子侵蚀已成为影响海洋及近海环境中混凝土结构耐久性的主要因素。考虑材料组成的非匀质特性,将混凝土看作由粗骨料、硬化水泥砂浆及二者界面过渡区组成的三相复合材料的细观层次方法,是开展物质传输过程研究的新途径。建立非饱和混凝土中氯离子传输的一维非线性对流扩散方程,并利用伽略金加权余数法给出了该方程的有限元形式,采用适用于物质传输的细观格构网络模型开展了水分及氯离子在非饱和混凝土中传输过程及分布规律研究,分析了干湿循环周期和循环机制对水分及氯离子传输性能的影响规律。数值计算结果表明,干湿交替下,相同的干燥时间,非饱和混凝土内水分及氯离子的侵入深度主要取决于湿润时间,而干燥时间和循环周期数则影响混凝土表层氯离子含量,并在混凝土表层10 mm处有浓度集中现象。  相似文献   

盆地埋藏火山机构的地质-地球物理二维精细解剖——以松南腰英台地区营城组一段为例   总被引：2，自引：0，他引：2       下载免费PDF全文

衣健  单玄龙  唐华风  张洋洋  陈玉平 《地球物理学报》2011,54(2):588-596

腰英台地区营城组一段火山岩气藏为火山机构内幕型气藏,其储层分布受火山机构控制.本文以旋回作为时间格架进行火山机构的精细划分.首先通过钻井火山岩岩性、岩相、测井资料识别出的旋回间风化壳和沉积岩夹层等地质界面,地震剖面上全区发育的连续强反射同相轴等划分火山岩的旋回.然后,在旋回内部根据不同钻井岩性、岩相的变化以及火山机构的...  相似文献