Integrated seismic interpretation of the Carlsberg Fault zone, Copenhagen, Denmark   总被引：1，自引：0，他引：1  

Lars Nielsen  Hans Thybo  Mette I. Jørgensen 《Geophysical Journal International》2005,162(2):461-478

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Determination Of The Surface Drag Coefficient   总被引：1，自引：0，他引：1  

L. Mahrt  Dean Vickers  Jielun Sun  Niels Otto Jensen  Hans Jørgensen  Eric Pardyjak  Harindra Fernando 《Boundary-Layer Meteorology》2001,99(2):249-276

This study examines the dependence of the surface drag coefficienton stability, wind speed, mesoscale modulation of the turbulent flux and method of calculation of the drag coefficient. Data sets over grassland, sparse grass, heather and two forest sites are analyzed. For significantly unstable conditions, the drag coefficient does not depend systematically on z/L but decreases with wind speed for fixed intervals of z/L, where L is the Obukhov length. Even though the drag coefficient for weak wind conditions is sensitive to the exact method of calculation and choice of averaging time, the decrease of the drag coefficient with wind speed occurs for all of the calculation methods. A classification of flux calculation methods is constructed, which unifies the most common previous approaches.The roughness length corresponding to the usual Monin–Obukhovstability functions decreases with increasing wind speed. This dependence on wind speed cannot be eliminated by adjusting the stability functions. If physical, the decrease of the roughness length with increasing wind speed might be due to the decreasing role of viscous effectsand streamlining of the vegetation, although these effects cannot be isolated from existing atmospheric data.For weak winds, both the mean flow and the stress vector often meander significantly in response to mesoscale motions. The relationship between meandering of the stress and wind vectors is examined. For weak winds, the drag coefficient can be sensitive to the method of calculation, partly due to meandering of the stress vector.  相似文献   

The application of the transient electromagnetic method in hydrogeophysical surveys   总被引：3，自引：0，他引：3  

Jens E. Danielsen  Esben Auken  Flemming Jrgensen  Verner Sndergaard  Kurt I. Srensen 《Journal of Applied Geophysics》2003,53(4):181

The transient electromagnetic (TEM) method has been used extensively for hydrogeophysical exploration in Denmark for the past decade. Innovative instrumentation combined with multi-dimensional modelling and interpretational insights based on experience gained through numerous case studies have proven to be a successful strategy. In the case study reported here, the combination revealed an unknown and unexpected buried valley complex. Drill hole data were in good agreement with estimates of both the bearings and depths of valleys defined by the TEM surveys. The Pulled Array Transient Electromagnetic (PATEM) system was built to provide high data density for increased lateral resolution. A High moment Transient Electromagnetic (HiTEM) system was developed for delineation of aquifers to depths up to 300 m. Because both of these systems provide high data density, data quality can be assessed as part of the interpretational strategy. When acquiring TEM measurements in areas as densely populated as the Danish countryside, precautions must be taken to minimize coupling between the TEM system and man-made conductors. Modelling the slope of the flanks of buried valleys has challenged the adequacy of the one-dimensional (1-D) assumption for inversion of TEM data. The study shows that for a valley structure in a low-resistive layer, the 1-D assumption is sufficient to track the presence of rather steep slopes. For a valley structure in a high-resistive layer, however, the insensitivity of the TEM method to resistors makes it difficult to determine a slope with a 1-D inversion, and only the overall structure is defined.  相似文献   

Lidar measurements of plume statistics     

Hans E. Jørgensen  Torben Mikkelsen 《Boundary-Layer Meteorology》1993,62(1-4):361-378

Surface-layer aerosol diffusion experiments have been conducted using artificial smoke plume releases at ground level over flat and homogeneously vegetated terrain at the Meppen proving grounds in the Federal Republic of Germany (1989). At fixed downwind locations in the range out to 800 m from the source, instantaneous crosswind plume profiles were detected repetitively at high spatial (1.5 m) and temporal (3 sec) intervals by use of a mini LIDAR system. The experiments were accompanied by measurement of the surface-layer mean wind and turbulence quantities by sonic anemometers. On the basis of measured crosswind concentration profiles, the following statistics were obtained: 1) Mean profile, 2) Root mean square profile, 3) Fluctuation intensities, and 4) Intermittency factors. Furthermore, some experimentally determined probability density functions (pdf's) of the fluctuations are presented. All the measured statistics are referred to a fixed and a moving frame of reference, the latter being defined as a frame of reference from which the (low frequency) plume meander is removed. Finally, the measured statistics are compared with statistics on concentration fluctuations obtained with a simple puff diffusion model (RIMPUFF) developed at Risø.  相似文献   

Diffusive and total oxygen uptake of deep-sea sediments in the eastern South Atlantic Ocean:in situ and laboratory measurements     

Ronnie Nhr Glud  Jens K. Gundersen  Bo Barker Jrgensen  Niels Peter Revsbech  Horst D. Schulz 《Deep Sea Research Part I: Oceanographic Research Papers》1994,41(11-12)

Total O₂ uptake rates were measured by the benthic flux chamber lander ELINOR, and O₂ microprofiles were measured by the profiling lander PROFILUR in the eastern South Atlantic. Diffusive O₂ fluxes through the diffusive boundary layer and the depth distribution of O₂ consumption rates within the sediment were calculated from the obtained microprofiles. The depth integrated O₂ consumption rate agreed closely with the diffusive O₂ uptake at all stations. Total O₂ uptake was 1.2–4.2 times the diffusive O₂ uptake, and the difference correlated with the abundance of macrofauna in the sediment. Diffusive O₂ uptake and O₂-penetration depths correlated with the organic content of the sediments and exhibited an inverse correlation with water depth. Total and diffusive rates of in situ O₂ uptake were higher than previously published data for shelf and abyssal sediments in the Atlantic, but were comparable to rates from upwelling areas in the eastern Pacific. Laboratory measurements on recovered sediment cores showed lower O₂ penetration depths and higher diffusive uptake rates than in situ measurements. The differences increased with increasing water depth. We primarily ascribe this compression of O₂ profiles to a transiently increased temperature during recovery and enhanced microbial activity in decompressed sediment cores. Total O₂ uptake rates measured in the laboratory on macrofauna-rich stations were, in contrast, lower than those measured in situ because of underrepresentation and disturbance of the macrofauna.  相似文献   

The Importance of Posidonia oceanica and Cymodocea nodosa as Contributors of Free Amino Acids in Water and Sediment of Seagrass Beds     

Niels O. G.  Jørgensen  T. Henry  Blackburn  Kai  Henriksen Daniel  Bay 《Marine Ecology》1981,2(2):97-112

Abstract. Dissolved free amino acids (DFAA) were measured in sediment porewater and overlying sea water in seagrass beds of Posidonia oceanica and Cymodocea nodosa at a water depth of 8–10 m in Corsica, France. In the sea water, DFAA concentrations from 0.5 to 1.9μM were found. Lowest concentrations occurred in the afternoon in surface water samples, while higher concentrations were measured in morning surface samples and in all bottom samples. The most abundant amino acids were serine, glycine, and alanine. In the sediment, the upper 4cm contained the highest concentrations of DFAA (177nmol cm^-3 or 367 μM), while lower concentrations (<50nmol cm^-3 or 104 μM) prevailed deeper in the sediment. Glycine, glutamic acid, alanine, and β-alanine were the major components of the DFAA. The photosynthetic activity of the seagrasses influenced sediment porewater pools of DFAA. When a Posidonia bed was covered with a black polyethylene shield, the interstitial amino acids were reduced at a rate of 16nmol cm^-2 h^-1 (0-10cm depth). Conversely, extended daylight (floodlight) increased the DFAA pool in sediment depths below 4 cm. Free amino acids were released to the overlying sea water from both seagrass sediment and individual shoots, the rates being highest in the dark. The present investigation indicates that a substantial portion of the N-cycling of the seagrass sediment includes free amino acids.  相似文献   

冲绳海槽北部的全新世火山碎屑沉积   总被引：1，自引：0，他引：1  

刘焱光  曹东林  张德玉  孙吉林  石学法 《海洋科学进展》2007,25(1):34-45

分析了冲绳海槽北部的CSH1岩芯沉积物中矿物组成、化学元素质量分数和粒度的变化规律,研究结果表明,在全新世期间,日本九州岛发生了2次大规模火山喷发活动,造成大量的火山物质沉积在冲绳海槽北部。从岩芯最上部的沉积物中可识别出2层火山碎屑沉积,它们都具有沉积物粒径突然变粗、SiO2和Na2O等化合物的质量分数突然增加以及粘土矿物、挥发份、Fe2O3、MgO、CaO和Sr的质量分数迅速下降等特征。沉积物粒度数据的端员分析结果表明,冲绳海槽北部全新世沉积物中的硅酸盐碎屑是由陆源碎屑物质和火山灰按不同的比例混合而成的。有火山物质混入的沉积物的粒度分布多呈现双峰模式,粒度众数值分别为74.3和7.81μm。浮游有孔虫壳体的AMS14C测年结果表明,2层火山碎屑所对应的火山喷发年代分别为7 210和10 870 cal.aBP。其中前者与K-Ah火山的喷发时间一致,后者可能与Kuju火山在12~10 cal.kaBP期间的喷发有关。  相似文献   

Linking climate change perceptions to adaptation and mitigation action     

Sisse Liv Jørgensen  Mette Termansen 《Climatic change》2016,134(1-2):283-297

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Hämatologische,enzymatische und histologische Untersuchungen an Fischen der Weser im Mai 1983     

E. Halsband  I. Halsband  B. Romestand  A. Dzuvi&#x;  B. Radtjkovi&#x;  D. Mari&#x;  S. Jürgensen 《洁净——土壤、空气、水》1985,13(6):669-690

The momentary condition concerning the haematological, physiological, macro-and microscopical constitution of the fishes of the Weser at Grohnde was investigated. The fishes were caught electrically at 22 positions in front of and behind the power-station at Grohnde. In the experiments the blood parameters, the biochemical, enzymatical, parasitological and microscopical changes of several species of fishes were analysed. You can see the details of these changes in the figures and pictures of the publication. It is supposed that organic toxic substances are given into the river in front of the power station, because in this region an industrial undertaking is posted. But also the general water quality of the Weser shows a significant toxicological degree, though the content of salt had been reduced in the former time. One can see that at all positions the blood parameters have changed, we also found haemorrhages in the gills, liver, kidney and spleen, little blood swellings, lymphocysts, necrosis, external and internal parasites, enzymatical changes and inflammations of the liver, kidney and myocard in the fishes. The investigations are being continued.  相似文献   

Strontium-isotope studies of “brown water” (organic-rich groundwater) from Denmark     

Niels Oluf Jørgensen  Jørn Morthorst  Paul Martin Holm 《Hydrogeology Journal》1999,7(6):533-539

 Groundwater from some Quaternary and upper Tertiary aquifers in western Jutland, Denmark, is heavily influenced by "brown water", i.e., groundwater with a high content of naturally occurring dissolved organic matter. Stable-isotope analyses (¹⁸O/¹⁶O and D/H) indicate that both Quaternary and upper Tertiary aquifers are dominated by meteoric water. However, strontium-isotope analyses make it possible to distinguish between water samples from Quaternary and Miocene aquifers. Relatively low ⁸⁷Sr/⁸⁶Sr ratios, i.e., ∼0.7083, in Sr-rich water samples indicate that the majority of dissolved Sr in groundwater from Miocene as well as Quaternary strata is probably derived from Miocene marine skeletal carbonate matter in the subsurface. This situation is probably the result of Quaternary glacial reworking of upper Tertiary material and/or hydraulic contact between Quaternary and Miocene aquifers. A positive correlation between Sr contents and non-volatile organic carbon indicates that the remarkably high contents of organic matter recorded in these aquifers almost certainly are derived from Miocene sources as well. Received, February 1999 / Revised, July 1999 / Accepted, July 1999  相似文献