Late Holocene effective precipitation variations in the maritime regions of south-west Scandinavia     

R. De Jong  D. Hammarlund  A. Nesje 《Quaternary Science Reviews》2009,28(1-2):54-64

At present, the climate in south-west Scandinavia is predominantly controlled by westerlies carrying moist Atlantic air, which forms a main source of precipitation in all seasons. Past variations in the ratio between precipitation and evaporation (effective precipitation) from terrestrial sites, however, may indicate changes in the degree of maritime influence. Palaeoclimatic archives in this region are thus ideally situated to study past changes in atmospheric circulation patterns. In this study, multi-proxy comparisons of records from three peat bogs and two lakes are used to reconstruct regional-scale variations of effective precipitation in south-west Sweden during the Late Holocene. The total aeolian sediment influx into two peat bogs is used as a proxy for storm activity. The frequency of storm phases increases strongly after ca 2500 cal yrs BP. Dry conditions occur on a regional scale around 4800–4400, 2000–1700, 1300–1000, 700–500 and 300–100 cal yrs BP. In addition, a comparison to winter precipitation reconstructed from four Norwegian glaciers shows similar variations during the past ca 2000 years. This indicates that the climate in both regions was controlled by large-scale atmospheric circulation dynamics of the North Atlantic region. The strong variability of effective precipitation and storm activity after ca 2500 cal yrs BP indicates a highly variable climate.  相似文献   

Selection of Suitable Window Size for Speckle Reduction and Deblurring using SOFM in Polarimetric SAR Images     

Sanjay Shitole  Shaunak De  Y. S. Rao  B. Krishna Mohan  Anup Das 《Journal of the Indian Society of Remote Sensing》2015,43(4):739-750

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Environmental reconstructions of the upper 500 m of the southern Indian Ocean over the last 40 ka using Radiolarian (Protista) proxies     

John Rogers  Patrick De Deckker 《Quaternary Science Reviews》2011,30(7-8):876-886

In 2007, we demonstrated that radiolarians are proxies for a wide range of oceanic physico-chemical properties from the surface to depths of up to 500 m below sea level. In this study, our results are refined and Correspondence Analysis (CA) scores derived from census counts of radiolarian subfossils from southern Indian Ocean core-tops are correlated with the physico-chemical properties of the region obtained from the 2005 World Ocean Database.Calibration and regression techniques are employed to reconstruct palaeoenvironmental conditions spanning the last 40 ka for four Indian Ocean cores MD88-769 [46°04′S 90°06′E], MD88-770 [46°01′S 96°27′E], MD94-102 [43°30′S 79°50′E], and MD94-103 [45°35′S 86°31′E], all from close to the Southeast Indian Ridge. For the first time, reconstructions of temperature, salinity, dissolved oxygen, and the silicate, nitrate, and phosphate concentrations for a range of water depths are proved possible.Changes of the oceanic environment and the movement of water masses over the last 40 ka, as suggested by these reconstructions, are discussed. During Marine Isotope Stages 2 and 3 (MIS-2 and MIS-3), the water column at some of the core sites has similar characteristics to the waters south of the Polar Front today. At the MIS-1/MIS-2 transition, the development of the Subantarctic Mode Water is apparent. Temperature reconstructions include evidence of the Antarctic Cold Reversal and the Holocene Optimum.  相似文献   

MegaZ-LRG: a photometric redshift catalogue of one million SDSS luminous red galaxies     

Adrian Collister  Ofer Lahav  Chris Blake  Russell Cannon  Scott Croom  Michael Drinkwater  Alastair Edge  Daniel Eisenstein  Jon Loveday  Robert Nichol  Kevin Pimbblet  Roberto De Propris  Isaac Roseboom  Nic Ross  Donald P. Schneider  Tom Shanks  David Wake 《Monthly notices of the Royal Astronomical Society》2007,375(1):68-76

We describe the construction of MegaZ-LRG, a photometric redshift catalogue of over one million luminous red galaxies (LRGs) in the redshift range  0.4 < z < 0.7  with limiting magnitude   i < 20  . The catalogue is selected from the imaging data of the Sloan Digital Sky Survey (SDSS) Data Release 4. The 2dF-SDSS LRG and Quasar (2SLAQ) spectroscopic redshift catalogue of 13 000 intermediate-redshift LRGs provides a photometric redshift training set, allowing use of ann z, a neural network-based photometric-redshift estimator. The rms photometric redshift accuracy obtained for an evaluation set selected from the 2SLAQ sample is  σ _z = 0.049  averaged over all galaxies, and  σ _z = 0.040  for a brighter subsample  ( i < 19.0)  . The catalogue is expected to contain ∼5 per cent stellar contamination. The ann z code is used to compute a refined star/galaxy probability based on a range of photometric parameters; this allows the contamination fraction to be reduced to 2 per cent with negligible loss of genuine galaxies. The MegaZ-LRG catalogue is publicly available on the World Wide Web from http://www.2slaq.info .  相似文献   

Organic matter in sediments of canyons and open slopes of the Portuguese,Catalan, Southern Adriatic and Cretan Sea margins     

Antonio Pusceddu  Silvia Bianchelli  Miquel Canals  Anna Sanchez-Vidal  Xavier Durrieu De Madron  Serge Heussner  Vasilios Lykousis  Henko de Stigter  Fabio Trincardi  Roberto Danovaro 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(3):441-457

We describe the quantitative and compositional (phytopigment, protein, carbohydrate and lipid) patterns of sedimentary organic matter along bathymetric gradients in seven submarine canyons and adjacent open slopes located at four European regions: one along the NE Atlantic and three along the Mediterranean continental margins. The investigated areas are distributed along a putative longitudinal gradient of decreasing primary production from the Portuguese (northeastern Atlantic Ocean), to the Catalan (western Mediterranean Sea), Southern Adriatic (central Mediterranean Sea) and Southern Cretan (eastern Mediterranean Sea) margins. Sediment concentrations of organic matter differed significantly between the Portuguese margin and the Mediterranean regions and also from one study area to the other within the Mediterranean Sea. Differences in quantity and composition of sediment organic matter between canyons and open slopes were limited and significant only in the eutrophic Portuguese margin, where the differences were as large as those observed between regions (i.e. at the mesoscale). These results suggest that the overall trophic status of deep margin sediments is controlled mostly by the primary productivity of the overlying waters rather than by the local topography. Moreover, we also report that the quantity and nutritional quality of sediment organic matter in canyons and adjacent open slopes do not show any consistent depth-related pattern. Only the Nazaré and Cascais canyons in the Portuguese margin, at depths deeper than 500 m, displayed a significant accumulation of labile organic matter. The results of our study underline the need of further investigations of deep margins through sampling strategies accounting for adequate temporal and spatial scales of variability.  相似文献   

仇山酸化钙基膨润土的 27Al和 29Si 魔角旋转核磁共振谱及脱色率研究   总被引：1，自引：0，他引：1  

何宏平  郭九皋  王德强  林鸿福  杨年华  杨保联  李丽云 《地球化学》2001,30(5):470-476

对用不同酸度处理的仇山钙基膨润土进行了化学分析、X射线衍线（XRD）、^27Al和^29Si魔角旋转核磁共振（MAS NMR）、吡啶吸附样品的红外光谱（IR）、比表面积、阳离子交换容量（CEC）和脱色率等测定。结果表明，随着处理酸度的增加和蒙脱石中阳离子的溶出，它的d(001)的衍射强度降低，同时其Si和Al原子局域结构环境发生了显著的改变，Al原子由Al^Ⅵ变成Al^Ⅵ，Si原子由Q^Si(0Al)结构向Q^4Si(0Al)和Q^3Si(1OH)结构转变。八面体片阳离子的溶出和Si,Al原子局域结构环境的转变，显著地增加了比表面积和孔结构；Al^Ⅵ向Al^Ⅵ的转变形成了Lewis酸中心，而Si原子局域结构环境的改变形成了Br φnsted酸中心。膨润土脱色率随处理酸度增加的本质原因是在Si和Al原子局域环境的变化过程中，在其表面分别形成了Brφnsted酸中心和Lewis酸中心。  相似文献   

RS、GPS、TMS相结合在合肥市大房郢水库工程用地测量中的应用     

刘德明  周松泉 《安徽地质》2001,11(4):245-249

为满足合肥市大房郢水库建设及土地管理部门对用地资井的要求，利用航空遥感片对用地现状进行了调查，采用航测解析法配合其它先进测量手段(GPS全球定位系统、TMS全站仪测量系统)确定用地的各类界线。本文介绍了这次工作的技术路线，土地利用现状调查，用地界线的确定，数字影像线划地籍图的编辑及数据汇总等方面的情况。  相似文献   

安徽黄山地区侏罗纪—白垩纪层序地层学特征   总被引：5，自引：0，他引：5  

余心起  王德恩 《现代地质》2001,15(1):27-34

通过 1∶ 5万区域地质调查工作对屯溪—休宁盆地、歙县洪琴盆地、绩溪华阳盆地、祁门盆地各类陆相沉积建造的沉积环境、沉积相、陆相沉积体系域进行了分析描述 ,将侏罗纪—白垩纪地层划分为四级地层层序 ,在层序地层学分析的基础上 ,建立了初步的红盆地层格架  相似文献   

淮安芒硝资源开发现状与发展对策     

高德云  李有才等 《江苏地质》2001,25(1):50-53

淮安芒硝资料的开发利用已使基我国东部新崛起的开采与加工基地，但问题也随之逐渐显现出来，主要是缺乏通盘规划、盲目扩大生产规模、污染环境以及勘查和基础设施跟不上等。就以上问题，作者对淮安芒硝开发提出了相应的对策与建议。  相似文献   

超细白云石矿粉润湿接触角的测定   总被引：9，自引：0，他引：9  

艾德生  李庆丰等 《岩矿测试》2001,20(2):97-99

根据Washburn方程，采用毛细管上升法，自行设计了简单的实验装置。提出了相对润湿接触角的概念，测定了3个超细CaCO3粉体在水中的润湿接触角。  相似文献