Further Studies Of Atmospheric Turbulence In Layers Near The Surface: Scaling The Tke Budget Above The Roughness Sublayer   总被引：2，自引：0，他引：2  

Paul Frenzen  Christoph A. Vogel 《Boundary-Layer Meteorology》2001,99(2):173-206

The second of two experimental studies of the TKE budget conducted on sites of different roughness is described, and results are compared. The first took place within a shallow layer above a small field of mostly bare, cultivated soil; the second was carried out above a roughness sublayer of significant depth on an extensive plain of tall dry grass. Budget terms observed in the second study were scaled with a modified u which compensated for effects of an unusually large stress gradient and ensured that the _m functions would be collinear. By showing that the modification becomes negligible in smaller gradients, it is demonstrated that in normal conditions, budgets observed above significant roughness sublayers should be normalized by scaling in terms of the unreduced Reynolds stress at the sublayer's upper surface. This procedure is shown to be consistent with the expectation that TKE budgets in layers near the surface all scale in fundamentally the same way.Other findings include: (1) the fact that most _m functions previously reported are not quite collinear is attributed to a type of overspeeding known to affect three-cup anemometers; (2) revised _m functions, collinear and largely free of the effects of overspeeding, are determined from a well-established characteristic of the linear _m relation for the stable case; (3) data that define collinear _m functions can also be represented with single hyperbolic curves; (4) dissipation is found to be 10 to 15% too small to balance total TKE production in unstable and neutral conditions and to decrease with increasing z/L in thestable regime; and (5) new relations for based on the observed behaviour of the dissipation deficit provide an improved closure for the set of equations that express the budget terms as functions of _m and z/L.  相似文献   

Enhanced red fluorescence emission in the oxygen minimum zone of the Arabian Sea     

Wiebke Breves  Rüdiger Heuermann  Rainer Reuter 《Ocean Dynamics》2003,53(2):86-97

 Depth profiles of fluorescence at several excitation and emission wavelengths were measured along with CTD data during the cruise So119 of RV Sonne in the Arabian Sea from 12 May to 10 June 1997. In addition to chlorophyll fluorescence from phytoplankton in the near-surface layer, the profiles in the oxygen minimum region well below the euphotic zone show enhanced red fluorescence. Red fluorescence intensity is inversely related to the oxygen concentration in intermediate and deep waters. A relationship to characteristic water masses of the region cannot be found in the data, and this holds also with chemical data such as DOC. Absorbance spectra of water samples taken in the oxygen minimum zone show an absorption band at 420 nm wavelength with about 50 nm bandwidth, much weaker than gelbstoff absorbance in the same wavelength range. The absorption band remains stable after sample filtration with 0.45 μm glass fibre filters. Hence, the size of the absorbing matter is in the range of dissolved molecules or particles much smaller than 1 μm. Fluorescence spectra of unfiltered samples with 420 nm excitation show a weak emission band at 600 nm and a more pronounced one at 660 nm wavelength. The trailing edge of the 660 nm band falls into the range of chlorophyll emission, thus giving rise to the observed depth profiles of red fluorescence in the oxygen minimum zone. Red fluorescence measured on samples remain stable during a few hours after sampling even in the presence of oxygen. It is not detectable after several weeks of sample storage in the dark and cannot be reproduced even after depletion of dissolved oxygen. Received: 22 May 2002 / Accepted: 18 February 2003 Responsible Editor: Andreas Oschlies Acknowledgements. This work was supported by a grant from the Federal Minister of Education and Technology, Bonn, within the frame work of the JGOFS Arabian Sea program. We are grateful to the captain and the crew of RV Sonne for their support. We are indebted to Mrs. Kirsten Neumann from the Institute of Marine Chemistry and Biogeochemistry of the University of Hamburg for providing the oxygen data, and to Mr. Nikolai Delling from the same institute for making the DOC and chlorophyll data available to us.  相似文献   

Oxygen isotope composition and geothermometry of granulite to greenschist facies metamorphic rocks: a study from the Neoproterozoic collision-related nappe system, south of São Francisco Craton, SE Brazil     

Maria da Glria M. Garcia  Mrio C. Campos Neto  Anthony E. Fallick 《Journal of South American Earth Sciences》2003,15(8):871-883

Oxygen isotope studies were carried out across units of a Neoproterozoic nappe system, south of São Francisco Craton. A temperature decrease toward the base of the system is found, consistent with a previously recognized inverted metamorphic pattern. The tectonic contact of the basal unit and the reworked southern São Francisco craton show a steep temperature gradient, suggesting that low temperature thrusting acted as the dominant tectonic process. The contrasts between the δ¹⁸O values of the Três Pontas-Varginha and Carmo da Cachoeira nappes and the differences among the samples and minerals are consistent with the preservation of sedimentary isotopic composition during metamorphism. The small differences in the δ¹⁸O values between the undeformed and the deformed calc-silicate samples (1.6‰) suggest that the δ¹⁸O value of mylonitization fluids was close to that which equilibrated with the metamorphic assemblage. The distinct δ¹⁸O values of metapelitic and calc-silicate samples and the great temperature difference from one type to the other indicate that no large-scale fluid interaction processes occurred during metamorphism. Oxygen isotopic estimations of both Três Pontas-Varginha undeformed rocks and Carmo da Cachoeira unaltered equivalents indicate δ¹⁸O values of up to 18‰. Comparison between these values and those from the ‘basement’ orthogneisses (8.3–8.5‰) indicates the latter are not sources for the metapelites.  相似文献   

A biogenic-silica δO record of climatic change during the last glacial–interglacial transition in southwestern Alaska     

Feng Sheng Hu  Aldo Shemesh 《Quaternary Research》2003,59(3):379-385

Despite growing evidence for environmental oscillations during the last glacial–interglacial transition from high latitude, terrestrial sites of the North Pacific rim, oxygen-isotopic records of these oscillations remain sparse. The lack of data is due partially to the paucity of lakes that contain carbonate sediment suitable for oxygen-isotopic analysis. We report here the first record of oxygen-isotopic composition in diatom silica (δ¹⁸O_Si) from a lake in that region. δ¹⁸O_Si increases gradually from 19.0 to 23.5‰ between 12,340 and 11,000 ¹⁴C yr B.P., reflecting marked climatic warming at the end of the last glaciation. Around 11,000 ¹⁴C yr B.P., δ¹⁸O_Si decreases by 1.7‰, suggesting a temperature decrease of 3.5–8.9 °C at the onset of the Younger Dryas (YD) in southwestern Alaska. Climatic recovery began ca. 10,740 ¹⁴C yr B.P., as inferred from the increase of δ¹⁸O_Si to a maximum of 23.9‰ near the end of the YD. Our data reveal that a YD climatic reversal in southwestern coastal areas of Alaska occurred, but the YD climate did not return to full-glacial conditions.  相似文献   

污水渗滤土地处理系统中的复氧方式及效果   总被引：24，自引：0，他引：24  

何江涛  张达政  陈鸿汉  汤鸣皋 《水文地质工程地质》2003,30(1):103-106,109

复氧是困扰人工快渗、构造湿地等污水渗滤土地处理系统已久的问题。国际上目前采用的方法主要有3种：一是采用干湿交替的工作方式进行系统复氧，一是设置通气管对系统内部进行复氧，再一是利用植物的根系对系统内部进行复氧。研究结果表明，干湿交替的工作方式对系统的复氧条件有明显改善，而小水力负荷周期的工作方式对系统的复氧更为有效。通气管的设置通常与间歇性布水工作方式相结合，其效果通常要明显好于单纯采用干湿交替的工作方式。植物根系对系统的复氧，常因植物不同类型面具有不同的氧传输能力，植物根茎所能到达的范围往往决定了系统有效处理部位的大小。  相似文献   

Climate induced temperature effects on growth performance, fecundity and recruitment in marine fish: developing a hypothesis for cause and effect relationships in Atlantic cod (Gadus morhua) and common eelpout (Zoarces viviparus)     

H. O. Prtner  B. Berdal  R. Blust  O. Brix  A. Colosimo  B. De Wachter  A. Giuliani  T. Johansen  T. Fischer  R. Knust  G. Lannig  G. Naevdal  A. Nedenes  G. Nyhammer  F. J. Sartoris  I. Serendero  P. Sirabella  S. Thorkildsen  M. Zakhartsev 《Continental Shelf Research》2001,21(18-19)

Effects of global warming on animal distribution and performance become visible in many marine ecosystems. The present study was designed to develop a concept for a cause and effect understanding with respect to temperature changes and to explain ecological findings based on physiological processes. The concept is based on a wide comparison of invertebrate and fish species with a special focus on recent data obtained in two model species of fish. These fish species are both characterized by northern and southern distribution limits in the North Atlantic: eelpout (Zoarces viviparus), as a typical non-migrating inhabitant of the coastal zone and the cod (Gadus morhua), as a typical inhabitant of the continental shelf with a high importance for fisheries.Mathematical modelling demonstrates a clear significant correlation between climate induced temperature fluctuations and the recruitment of cod stocks. Growth performance in cod is optimal at temperatures close to 10°C, regardless of the population investigated in a latitudinal cline. However, temperature specific growth rates decrease at higher latitudes. Also, fecundity is less in White Sea than in North and Baltic Sea cod or eelpout populations. These findings suggest that a cold-induced shift in energy budget occurs which is unfavorable for growth performance and fecundity. Thermal tolerance limits shift depending on latitude and are characterized by oxygen limitation at both low or high temperatures. Oxygen supply to tissues is optimized at low temperature by a shift in hemoglobin isoforms and oxygen binding properties to lower affinities and higher unloading potential. Protective stimulation of heat shock protein synthesis was not observed.According to a recent model of thermal tolerance the downward shift of tolerance limits during cold adaptation is associated with rising mitochondrial densities and, thus, aerobic capacity and performance in the cold, especially in eurythermal species. At the same time the costs of mitochondrial maintenance reflected by mitochondrial proton leakage should rise leaving a lower energy fraction for growth and reproduction. The preliminary conclusion can be drawn that warming will cause a northern shift of distribution limits for both species with a rise in growth performance and fecundity larger than expected from the Q₁₀ effect in the north and lower growth or even extinction of the species in the south. Such a shift may heavily affect fishing activities in the North Sea.  相似文献   

华南花岗岩类中铁钛副矿物组合与氧逸度关系   总被引：2，自引：0，他引：2  

陈鸣  张成江 《岩石学报》1991,7(2):89-94

华南花岗岩中存在两类矿物组合:(1)铁透闪石 钛铁矿 榍石 磁铁矿 石英;(2)钛铁矿 方解石 石英 磁铁矿 榍石。可通过以下关系分别计算上述两组矿物组合的岩浆氧逸度。组合(1)为: logfo_2=-24940.31/T 9.25 243.43(P-10~5Pa)/T 0.86logfH_2O-0.86logα铁透闪石组合(2)为: logfo_2=-3673.68/T-37.73 590.53(P-10~5Pa)/T 6logfco_2岩浆作用过程的氧逸度(fo_2)是控制磁铁矿、钛铁矿、榍石等铁、钛副矿物形成和稳定的重要因素。  相似文献   

Eolian deposition determined by the oxygen plasma furnace     

P. S. A. Jones 《地球表面变化过程与地形》1984,9(5):479-484

The oxygen plasma furnace enables small samples of clastic sediment to be separated from filter papers at low temperatures without physical or chemical alteration of the sediment. This technique provides a suitable treatment for processing very small samples of alpine eolian sediment, enabling their grain size distribution, mineralogy, and origin to be determined.  相似文献   

Rhinocerotid tooth enamel 18O/16O variability between 23 and 12 Ma in southwestern France     

Ilhem Bentaleb  Cyril Langlois  Céline Martin  Paula Iacumin  Matthieu Carré  Pierre-Olivier Antoine  Francis Duranthon  Issam Moussa  Jean-Jacques Jaeger  Nicholas Barrett  Ron Kandorp 《Comptes Rendus Geoscience》2006,338(3):172-179

The relationship between the oxygen isotope ratio of mammal tooth enamel and that of drinking water was used to reconstruct changes in the Miocene oxygen isotope ratio of rainfall (meteoric water ${\delta }^{18}$O_MW). These, in turn, are related to climatic parameters (temperature, precipitation and evaporation rate). ${\delta }^{18}$O values of rhinocerotid teeth from the Aquitaine Basin (southwestern France) suggest a significant climatic change between 17 and 12 Ma, characterized by cooling together with precipitation increase, in agreement with other terrestrial and oceanic records. To cite this article: I. Bentaleb et al., C. R. Geoscience 338 (2006).  相似文献   

Paleoceanographic evolution of the SW Svalbard margin (76°N) since 20,000 C yr BP     

Tine L. Rasmussen  Erik Thomsen  Simon Jessen  Nalân Koç 《Quaternary Research》2007,67(1):100-114

Two cores from the southwestern shelf and slope of Storfjorden, Svalbard, taken at 389 m and 1485 m water depth have been analyzed for benthic and planktic foraminifera, oxygen isotopes, and ice-rafted debris. The results show that over the last 20,000 yr, Atlantic water has been continuously present on the southwestern Svalbard shelf. However, from 15,000 to 10,000 ¹⁴C yr BP, comprising the Heinrich event H1 interval, the Bølling-Allerød interstades and the Younger Dryas stade, it flowed as a subsurface water mass below a layer of polar surface water. In the benthic environment, the shift to interglacial conditions occurred at 10,000 ¹⁴C yr BP. Due to the presence of a thin upper layer of polar water, surface conditions remained cold until ca. 9000 ¹⁴C yr BP, when the warm Atlantic water finally appeared at the surface. Neither extensive sea ice cover nor large inputs of meltwater stopped the inflow of Atlantic water. Its warm core was merely submerged below the cold polar surface water.  相似文献