Area-Averaged Surface Fluxes Over the Litfass Region Based on Eddy-Covariance Measurements     

Frank Beyrich  Jens-Peter Leps  Matthias Mauder  Jens Bange  Thomas Foken  Sven Huneke  Horst Lohse  Andreas Lüdi  Wouter M. L. Meijninger  Dmitrii Mironov  Ulrich Weisensee  Peter Zittel 《Boundary-Layer Meteorology》2006,121(1):33-65

Micrometeorological measurements (including eddy-covariance measurements of the surface fluxes of sensible and latent heat) were performed during the LITFASS-2003 experiment at 13 field sites over different types of land use (forest, lake, grassland, various agricultural crops) in a 20 × 20 km² area around the Meteorological Observatory Lindenberg (MOL) of the German Meteorological Service (Deutscher Wetterdienst, DWD). Significant differences in the energy fluxes could be found between the major land surface types (forest, farmland, water), but also between the different agricultural crops (cereals, rape, maize). Flux ratios between the different surfaces changed during the course of the experiment as a result of increased water temperature of the lake, changing soil moisture, and of the vegetation development at the farmland sites. The measurements over grass performed at the boundary-layer field site Falkenberg of the MOL were shown to be quite representative for the farmland part of the area. Measurements from the 13 sites were composed into a time series of the area-averaged surface flux by taking into account the data quality of the single flux values from the different sites and the relative occurrence of each surface type in the area. Such composite fluxes could be determined for about 80% of the whole measurement time during the LITFASS-2003 experiment. Comparison of these aggregated surface fluxes with area-averaged fluxes from long-range scintillometer measurements and from airborne measurements showed good agreement.  相似文献   

Delayed fractionation of basaltic lavas     

Sven Maaløe  Rolf B. Pedersen  D. James 《Contributions to Mineralogy and Petrology》1988,98(4):401-407

The phenocryst cores of the basaltic lavas from Jan Mayen and Hawaii display a range in compositions. The textural features of the phenocrysts also vary, both euhedral and skeletal phenocrysts are present in the same thin section. Apparently the basaltic magmas underwent crystallization within a temperature interval of 50–200° C before they became fractionated. The fractionates of basaltic lavas are therefore average compositions of the phenocryst assemblages rather than liquidus compositions. This type of fractionation is called delayed fractionation. It is considered that most tholeiitic and alkalic basaltic lavas undergo delayed fractionation.  相似文献   

The generation and shape of feeder dykes from mantle sources     

Sven Maaløe 《Contributions to Mineralogy and Petrology》1987,96(1):47-55

The criterion for fracture propagation suggests that the primary magma generated in the mantle ascends in a stepwise fashion. Initially a pulse of magma forms a dyke above the mantle source and ascends for some distance, whereafter it stops. A subsequent pulse of magma joins the first one, and the ascent of the accumulating body of magma continues for some distance each time a new pulse of magma reaches the body of magma situated in the top of the dyke. In this manner a dyke is formed that may extend either partly or the whole way from the mantle source to the surface. This model may explain the large pressures, up to 2000 bars, that prevail during basaltic eruptions. The calculated shape of the ascending pulses of magma suggests that their heights and widths are similar.  相似文献   

Turbulent exchange above a pine forest,I: Fluxes and gradients     

Ulf Högström  Hans Bergström  Ann-Sofi Smedman  Sven Halldin  Anders Lindroth 《Boundary-Layer Meteorology》1989,49(1-2):197-217

Measurements of gradients of wind, temperature and humidity and of the corresponding turbulent fluxes have been carried out over a sparse pine forest at Jädra»s in Sweden. In order to ascertain that correct gradient estimates were obtained, two independent measuring systems were employed: one system with sensors at 10 fixed levels on a 51 m tower and another with reversing sensors for temperature and humidity, covering the height interval 23 to 32 m. Turbulent fluxes were measured at three levels simultaneously. Data from three field campaigns: in June 1985, June 1987 and September 1987 have been analyzed. The momentum flux is found on the average to be virtually constant from tree top level, at 20 to 50 m. The average fluxes of sensible and latent heat are not so well behaved. The ratio of the non-dimensional gradients of wind and temperature to their corresponding values under ideal conditions (low vegetation) are both found to be small immediately above the canopy (about 0.3 for temperature and 0.4 for wind). With increasing height, the ratios increase, but the values vary substantially with wind direction. The ratios are not found to vary systematically with stability (unstable stratification only studied). The ratio of the non-dimensional humidity gradient to the corresponding non-dimensional potential temperature gradient (equivalent to k _h /k _w ) is found to be unity for (z – d)/L _v less than about –0.1 and about 1.4 for near neutral stratification, but the scatter of the data is very large.  相似文献   

Development of a hydrogeological model description of intrusive rock at different investigation scales: an example from south-eastern Sweden     

Ingvar Rhén  Hans Thunehed  Carl-Axel Triumf  Sven Follin  Lee Hartley  Jan Hermansson  Carl-Henric Wahlgren 《Hydrogeology Journal》2007,15(1):47-69

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Problems associated with luminescence dating of Late Quaternary glacial sediments in the NW Scottish Highlands   总被引：2，自引：0，他引：2  

Sven Lukas  Joel Q.G. Spencer  Ruth A.J. Robinson  Douglas I. Benn   《Quaternary Geochronology》2007,2(1-4):243-248

Linking the timing of glacial episodes and behaviour to climatic shifts that are documented in ice and marine sedimentary archives is key to understanding ocean-land interactions. In the NW Scottish Highlands a large number of closely spaced (‘hummocky’) moraines formed at retreating glacier margins. Independent age control on one palaeo-glacier limit is consistent with the timing of Younger Dryas (YD) glaciation in the area, but adjacent glacier lobes have remained undated due to the lack of sites and material for ¹⁴C dating. Direct dating of ice-marginal moraines using optically stimulated luminescence (OSL) techniques has never been attempted before in Scotland, but if successful, they may be the most appropriate methods for constraining the age of sediment deposition in the absence of organic material. Coarse-grained quartz and K-feldspar minerals from supraglacial sheet flow deposits and glacilacustrine sediments within ice-marginal moraines were analysed using the single-aliquot regenerative-dose (SAR) protocol. Independent age control and clear geomorphological relationships indicate that all samples should yield YD or post-Last Glacial Maximum (LGM) ages. Quartz OSL shine down curves showed low luminescence sensitivity, significant medium-to-slow components, a weak fast component, and scattered SAR data; Linearly Modulated-OSL (LM-OSL) measurements confirmed that the fast component was weak or absent. In contrast, feldspar infrared stimulated luminescence (IRSL) was highly sensitive with excellent SAR data. However, SAR data from 3 mm diameter aliquots of feldspar (200 grains) give higher than expected equivalent doses (D_e) by an order of magnitude. SAR measurements of small clusters of feldspar grains (ranging from 1–8) considerably broaden the apparent D_e distribution, but even the lowest value is about 2–3 times the expected D_e. Two possibilities arise to explain the quartz and feldspar data: (1) that glacial sequences in the NW Highlands re-work inherited (older) glacial deposits and that some of the pre-Devensian existing glacial landforms have only been modified during Devensian glaciation; or (2) that the sedimentary processes operating in these ice-marginal environments are not conducive to adequate bleaching of quartz and feldspar grains. Our study implies that ice-proximal supraglacial sediments from this region in NW Scotland reflect older ages of deposition, but dating YD sediments has not been possible.  相似文献   

Comment on “Stable carbon isotopes in freshwater mussel shells: Environmental record or marker for metabolic activity?” by J. Geist et al. (2005)     

Bernd R. Schöne  David L. Rodland  Jens Fiebig  Sven M. Baier 《Geochimica et cosmochimica acta》2006,70(10):2658-2661

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Timing of Uralian orogenic gold mineralization at Kochkar in the evolution of the East Uralian granite-gneiss terrane     

Jochen Kolb  Sven Sindern  Alexander F. M. Kisters  F. Michael Meyer  Stephan Hoernes  Jens Schneider 《Mineralium Deposita》2005,40(5):473-491

Gold mineralization at Kochkar (Urals, Russia) is hosted mainly by quartz lodes, which developed at lithological contacts between mafic dikes and granitoids of the Plast massif during late Carboniferous to early Permian, regional E–W compression in the East Uralian Zone (EUZ). The alteration mineralogy in mafic dikes comprises biotite, actinolite, albite, K-feldspar, quartz, epidote, tourmaline, sericite, pyrite, arsenopyrite, chalcopyrite, sphalerite, fahlores, galena, bismuthinite, and gold, and in Plast granitoids quartz, sericite, calcite, epidote, and ore minerals. Geochemically, an enrichment of Si, K, Rb, Ba, S, base metals, W, and Au can be observed. The ore fluid had δ¹⁸O values between 8.2‰ and 9.5‰ typical for metamorphic or deep magmatic fluids. The tectonometamorphic evolution of the EUZ is marked by peak metamorphic conditions at 635±40°C and 5–6 kbar through 500±20°C during gold mineralization, and 300–350°C and 2–3 kbar. The last event was dated on a late, barren quartz vein formed during greenschist facies metamorphism at 265±3 Ma by the Rb–Sr method. Fluids related to this overprint had a δ¹⁸O value of 5.2‰ and an initial ⁸⁷Sr/⁸⁶Sr ratio of 0.70685 indicating that they are largely equilibrated with metamorphic lithologies of the EUZ. The Plast granitoids and the adjacent Borisov granite, which was dated at 358±23 Ma (U–Pb zircon age), have an adakitic character. This, together with the arc-signature of the mafic dikes, supports the setting of the EUZ within the Valerianovsky continental arc. Eastward subduction of the Uralian Ocean below this arc began during the late Devonian to early Carboniferous. Between 320 and 265 Ma, the oblique closure of the ocean resulted in doming of granitoid massifs in a sinistral transpressional regime, subsequent retrograde gold mineralization during E–W compression and a later greenschist facies overprint. This long-lasting retrograde evolution of the EUZ was caused by the lack of postcollisional collapse. Heat for a “deep-later" type of metamorphism and triggering the auriferous fluid system was supplied by radiogenic heating of an overthickened crust. The greenschist facies overprint at Kochkar and coeval crustal melting in the EUZ was additionally initiated by local external heating of the terrane. This could have been caused by syn- to postcollisional slab rollback or delamination resulting in magmatic underplating of the EUZ, which postdates orogenic gold mineralization at Kochkar. The tectonic interpretation of the EUZ indicates that gold mineralization at Kochkar formed in a mid-crustal environment of a continental magmatic arc at the cessation of active subduction predating post orogenic plutonism.  相似文献   

Assessment of climate change impacts on the hydrology of the Peruvian Amazon–Andes basin     

Waldo Sven Lavado Casimiro  David Labat  Jean Loup Guyot  Sandra Ardoin‐Bardin 《水文研究》2011,25(24):3721-3734

In this article, we propose an investigation of the modifications of the hydrological response of two Peruvian Amazonas–Andes basins in relationship with the modifications of the precipitation and evapotranspiration rates inferred by the IPCC. These two basins integrate around 10% of the total area of the Amazonian basin. These estimations are based on the application of two monthly hydrological models, GR2M and MWB3, and the climatic projections come from BCM2, CSMK3 and MIHR models for A1B and B1 emission scenarios (SCE A1B and SCE B1). Projections are approximated by two simple scenarios (anomalies and horizon) and annual rainfall rates, evapotranspiration rates and discharge were estimated for the 2020s (2008–2040), 2050s (2041–2070) and 2080s (2071–2099). Annual discharge shows increasing trend over Requena basin (Ucayali river), Puerto Inca basin (Pachitea river), Tambo basin (Tambo river) and Mejorada basin (Mantaro river) while discharge shows decreasing trend over the Chazuta basin (Huallaga river), the Maldonadillo basin (Urubamba river) and the Pisac basin (Vilcanota river). Monthly discharge at the outlet of Puerto Inca, Tambo and Mejorada basins shows increasing trends for all seasons. Trends to decrease are estimated in autumn discharge over the Requena basin and spring discharge over Pisac basin as well as summer and autumn discharges over both the Chazuta and the Maldonadillo basins. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

AffectRoute – considering people’s affective responses to environments for enhancing route-planning services     

Haosheng Huang  Silvia Klettner  Manuela Schmidt  Georg Gartner  Sven Leitinger  Andreas Wagner 《International journal of geographical information science》2014,28(12):2456-2473

Humans perceive and evaluate environments affectively. Some places are experienced as unsafe, while some others as attractive and interesting. These affective responses to environments influence people’s daily behavior and decision-making in space, e.g., choosing which route to take, or which place to visit. In this article, we report on a methodology of using people’s affective responses to environments for enhancing computer-based route planning. More specifically, we explore a crowdsourcing approach to model and collect people’s affective responses to environments; an Affect-Space-Model and a mobile application are developed to facilitate this crowdsourcing approach; a routing algorithm (named AffectRoute) is then proposed to aggregate and integrate the collected data for automatic route planning. Evaluation with human participants shows that the routes generated by considering people’s affective responses to environments are significantly preferred over the conventional shortest ones, which are employed in car navigation systems and many online route planners. In conclusion, considering people’s affective responses to environments contributes to the improvement of automatic route planning. The proposed method can be integrated into existing route-planning services (e.g., location-based services) to provide users with more satisfying routing results.  相似文献