Testate amoebae as estuarine water‐level indicators: modern distribution and the development of a transfer function from a freshwater tidal marsh (Scheldt estuary,Belgium)     

Marijke Ooms  Louis Beyens  Stijn Temmerman 《第四纪科学杂志》2011,26(8):819-828

Little is known about the century‐scale response of water levels in inland estuaries to sea‐level change and human modifications to estuarine morphology. This study explored the ability of using testate amoebae (Protozoa, Rhizopoda) from sediments of a freshwater tidal marsh as indicators of water level in an inland estuary. The hypothesis was that modern testate amoeba assemblages change with surface elevation (approximately the duration of tidal flooding) within a freshwater tidal marsh. Variation in testate amoeba assemblages in relation to multiple environmental variables and sediment characteristics was studied through redundancy analysis. This demonstrated that a significant part of the variation in modern testate amoeba assemblages could be explained by flooding frequency, surface elevation, organic content and particle size of the soil. Transfer functions, partial least squares and weighted average regressions were made to show that testate amoebae can be used for reconstruction of water level (with an accuracy of 0.05 Normalized Elevation). A preliminary test of application of the transfer function to palaeo testate amoeba assemblages showed promising results. Testate amoebae from a freshwater tidal marsh provide a potentially powerful new tool for estuarine water‐level reconstructions. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Studies on groundwater recharge characteristics at a reclaimed land site with an equatorial climate using time‐series and spectral analyses     

Stephen Boon Kean Tan  Eng Ban Shuy  Lloyd Hock Chye Chua  Woon Kang Yee 《水文研究》2007,21(7):939-948

Groundwater recharge studies are essential for investigating the feasibility of using the reclaimed lands in Singapore for subsurface storage and recovery of water. Through time‐series and spectral analyses, net recharge percentages and stress‐filtering characteristics at the reclaimed land were found to depend strongly on the stress transfer velocity, which was a combined function of rainfall pattern and vadose zone thickness. Based on stress transfer velocity, a theory was established to provide logical explanations for the rainfall–recharge relationship, the observed stress‐filtering characteristics and the recharge percentage characteristics at the unconfined sandy aquifer. Although the reclaimed land site has a lithollogically homogeneous soil profile, a non‐uniform recharge pattern was observed to be influenced pronouncedly by the uneven density distribution of bush grasses. Under a bare soil condition, significantly lower recharge percentages were observed for areas under the influence of offshore tides. The unconfined sandy aquifer appears to dampen out the wave propagation of offshore tides rapidly within a short distance from the tidal source, though it has a fairly straight shoreline and is created from highly compacted sand fills. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

滇中喀斯特地区大气降水水汽来源和输送特征          下载免费PDF全文

彭晓红  丁文荣  陈相标 《气象科学》2023,43(6):781-789

本文利用2010—2019年滇中石林县的全球再分析资料，通过HYSPLIT模型的后向轨迹对不同季节和不同高度的水汽来源进行追踪和分析。结果表明：石林县四季的水汽源地和水汽运移路径存在差异。春季水汽主要来源于受高空西风影响的欧亚大陆和非洲北部，夏季水汽主要来源于孟加拉湾，南海和西太平洋海域，秋季水汽主要来源于孟加拉湾—南海和西太平洋，冬季主要来源于欧亚大陆和非洲北部的高空西风、孟加拉湾海域。石林县的水汽通道有阿拉伯海和孟加拉湾—南海、西太平洋、欧亚非大陆、局地五条水汽通道，且春夏秋冬四季的不同高度层的水汽输送通道和水汽贡献率存在较大差异。  相似文献   

Spectral Features of Photon Bubble Models of Ultraluminous X-ray Sources     

Justin D. Finke  Markus Böttcher 《Astrophysics and Space Science》2007,307(1-3):325-327

The nature of Ultraluminous X-ray Sources – X-ray sources which exceed the Eddington luminosity for a ∼10 M _⊙ black hole – remains a mystery. One possible explanation is an inhomogeneous accretion disk around a solar mass black hole where photon transport through radiation-pressure dominated “photon bubbles” can lead to super-Eddington accretion. While previous studies of this model have focused primarily on its radiation-hydrodynamics aspects, here we explore some observational implications of such a model with a Monte Carlo–Fokker Planck radiation transport code.  相似文献   

龙门山断裂带印支期左旋走滑运动及其大地构造成因   总被引：60，自引：6，他引：60  

王二七  陈智梁等 《地学前缘》2001,8(2):375-384

位于青藏高原东缘的龙门山构造呈北东—南西向将松潘—甘孜褶皱带和华南地块分割开。前者主要是由一套巨厚的三叠纪复理石沉积组成 ,分布在古特提斯海的东缘。后者由前寒武纪基底和上覆的古生代和中生代沉积盖层组成。位于汶川—茂汶断裂以东的前龙门山存在一系列倾向北西的逆掩断层 ,它们将许多由元古宙和古生代岩层组成的断片向南东置于四川盆地的中生代红层之上 ,构成典型的薄皮构造。许多研究由此断定松潘—甘孜褶皱带和四川盆地之间在中生代发生过大规模的北西—南东向挤压。然而 ,汶川—茂汶断裂西侧的松潘—甘孜褶皱带内部的挤压构造线大多是垂直于而不是平形于龙门山断裂带 ,这表明当时的挤压应力不是北西—南东向而是北东—南西向。近年来在龙门山构造带内发现 ,在三叠纪时龙门山断裂带在发生推覆的同时还经历过大规模的北东—南西向的左旋走滑运动 ,协调走滑运动的主要构造为汶川—茂汶断裂。走滑运动的成因与松潘—甘孜褶皱带北东—南西向缩短有关。汶川—茂汶断裂的左旋走滑在龙门山的北东端被古特提斯海沿勉略俯冲带的消减和发生在大巴山的古生代 /中生代岩层的褶皱和冲断作用所吸收 ,在龙门山的南西端被古特提斯海沿甘孜—理塘俯冲带的消减和松潘—甘孜三叠纪复理石的褶皱和冲断作用所吸?  相似文献   

Power and changes in the balance between ideology and pragmatism in the right wing Likud Party     

S. Ben-Rafael Galanti  W.E. Aaronson  I. Schnell 《GeoJournal》2001,53(3):263-272

When the Zionist executive abandoned Jewish rights to Trans-Jordanian Palestine, Jabotinsky established the Revisionist movement from which Etzel the Jewish right-wing underground movement in Palestine developed. This was the precursor of the Herut (Freedom) Party, from which the Likud party emerged in September 1973 to challenge the Labour Alignment (headed by the Israel Labour Party). Between the War of Independence (1948) and the signature of the Camp David accords (1978), the Government of Israel came under strong international pressure to solve the problem of the Arab refugees. During this time, dramatic changes took place in Herut's ideology and political status. In 1948, Herut was an outcast political party with a radical ideology, demanding the establishment of a Jewish Commonwealth on both sides of the Jordan. It perceived the Arab refugees to be a potential fifth column and the contiguous Arab states to be inimical. It strenuously opposed the Mapai led political Establishment's willingness to sign Armistice Agreements and make compromises with regard to Arab refugees. After Levi Eshkol replaced Ben-Gurion as the head of Mapai, Herut began to become part of the Israeli consensus and a member of the political Establishment. Herut served in Levy Eshkol's National Crisis Government before and during the 1967 war, and as the major force of Gahal, after the war. Concomitant with this, there were great changes in Herut's expressed ideology, chief among these were the tacit renunciation of trans-Jordan Palestine as part of the Jewish Commonwealth and the explicit acceptance of the Arab refugees as potential citizens of the State of Israel.  相似文献   

亚热带森林岩溶区土壤CO_2迁移动态初步研究     

冉景丞  何师意  曹建华 《贵州地质》2001,(4)

贵州茂兰是研究森林覆盖下岩溶表层系统结构特征、运行规律的重要基地。本文初步研究了该地区碳迁移的若干特征 :(1)土壤剖面中CO2 浓度变化。秋、冬季土下CO2 浓度 ,5 0cm处始终高于 2 0cm处 ,而在春、夏季土壤剖面中CO2 浓度变化幅度大 ,2 0cm处的浓度时常高出5 0cm处。土下 2 0cm、 5 0cm处CO2 浓度在不同季节的变化趋势是夏季 (32 833× 10 - 6、 386 6 6× 10 - 6)春季 (2 4 4 16× 10 - 6,2 880 0× 10 - 6)秋季 (6 4 5 0× 10 - 6) ,142 16× 10 - 6>冬季 (3833× 10 - 6,8833× - 6) ,土下CO2 浓度变化趋势与温度和降雨量有较好的正相关关系。 2 0cm处的CO2 浓度变化与温度的相关系数r =0 89,与降雨量的相关系数r =0 70 ;5 0cm处的CO2 浓度变化与温度的相关系数r =0 6 9,与降雨量的相关系数r =0 6 6。 (2 )土壤呼吸释放CO2 的速率有类似的变化规律 :夏季为 339 6 8mg m- 2 h- 1、为 2 81 74mg m- 2 h- 1、秋季为 2 0 6 5 9mg m- 2 h- 1、冬季为 6 5 5 3mg m- 2 h- 1。年均排放量为 1 96kg m- 2 yr- 1。 (3)随水排泄HCO3 - 1是岩溶表层泉碳迁移的重要组分。表层泉水的HCO3 - 1浓度的季节变化与气温、月降雨量、土下 2 0cm处CO2浓度存在着负相关 ,其相关系数r =- 0 5 7、  相似文献   

来自印度季风区的水汽输送与东亚上空水汽输送和中国夏季降水的关系   总被引：59，自引：3，他引：59  

Zhang Renhe 《大气科学进展》2001,18(5):1005-1017

诊断分析了北半球夏季来自印度季风的水汽输送与东亚上空水汽输送的关系，发现二者之间具有反相变化的特征。印度季风水汽输送偏强（偏弱）时，东亚上空的水汽输送偏弱（偏强），长江中下游降水偏少（偏多）。印度夏季风水汽输送与西太平洋副热带高压强度有显著的相关关系，印度季风水汽输送偏强（偏弱）时，西太平洋副热带高压强度偏弱（偏强），由此导致副高西侧东亚上空向北的水汽输送减弱（增强），使得长江中下游降水偏少（偏多）。对反映热带对流活动的外逸长波辐射（OLR）的分析表明，印度洋上空的对流加热异常不仅能够显著地影响印度季风，也可能对东亚季风产生直接的影响。  相似文献   

镇江市霉变指数预报     

沈兴建  朱筱英  顾永顺  张葵  田永飞  张信龙 《气象》2001,27(12):50-53

统计分析了物品发生霉变的气象条件－－气温、相对湿度、水汽压的气候分布概况，根据有关气象要素的分布特征设计出霉变函数的计算公式和霉变指数查算表，研制霉变指数预测模型并进行决策服务。5个月的实际应用表明，其准确率达97.4%。  相似文献   

地磁短周期变化异常对中国中强地震的响应   总被引：11，自引：0，他引：11  

曾小苹  林云芳 《地震》1995,(1):29-36

我们考察了发生在中国的１１个具有代表性的地震后发现。地震前地磁短周期转换函数的帕金森矢量或韦氏矢量指向震中方向，转换函数│Ａ│或│Ｂ│值明显偏离正常值以及总误差δｚ显著增大，均为未来地震的发生和震中方向提供了判断依据。应用此法，我们成功地预报了Ｍｓ５．１地震。中国地震科技工作者认为，震前地磁短周期变化异常是客观存在的。物理基础是清楚的，是有希望的地震短临预报方法。  相似文献