Evaporation from boreal reservoirs: A comparison between eddy covariance observations and estimates relying on limited data     

Judith Fournier  Antoine Thiboult  Daniel F. Nadeau  Nikki Vercauteren  François Anctil  Annie-Claude Parent  Ian B. Strachan  Alain Tremblay 《水文研究》2021,35(8):e14335

Hydrological models used for reservoir management typically lack an accurate representation of open-water evaporation and must be run in a scarce data context. This study aims to identify an accurate means to estimate reservoir evaporation with simple meteorological inputs during the open-water season, using long-term eddy covariance observations from two boreal hydropower reservoirs with contrasting morphometry as reference. Unlike the temperate water bodies on which the majority of other studies have focused, northern reservoirs are governed by three distinct periods: ice cover in the cold season, warming in the summer and energy release in the fall. The reservoirs of interest are Eastmain-1 (52°N, mean depth of 11 m) and Romaine-2 (51°N, mean depth of 42 m), both located in eastern Canada. Four approaches are analysed herein: a combination approach, a radiation-based approach, a mass-transfer approach, and empirical methods. Of all the approaches, the bulk transfer equation with a constant Dalton number of 1.2 x 10⁻³ gave the most accurate estimation of evaporation at hourly time steps, compared with the eddy covariance observations (RMSE of 0.06 mm h⁻¹ at Eastmain-1 and RMSE of 0.04 mm h⁻¹ at Romaine-2). The daily series also showed good accuracy (RMSE of 1.38 mm day⁻¹ at Eastmain-1 and RMSE of 0.62 mm day⁻¹ at Romaine-2) both in the warming and energy release phases of the open-water season. The bulk transfer equation, on the other hand, was incapable of reproducing condensation episodes that occurred soon after ice breakup. Basic and variance-based sensitivity analyses were conducted, in particular to measure the variation in performance when the bulk transfer equation was applied with meteorological observations collected at a certain distance (~10–30 km) from the reservoir. This exercise illustrated that accurate estimates of open water evaporation require representative measurements of wind speed and water surface temperature.  相似文献   

OMEGA long wavelength channel: Data reduction during non-nominal stages     

Denis Jouglet  François Poulet  Yves Langevin  Jean-Pierre Bibring  Brigitte Gondet  Mathieu Vincendon  Michel Berthe 《Planetary and Space Science》2009,57(8-9):1032-1042

The Observatoire pour la Minéralogie, l’Eau, les Glaces et l’Activité (OMEGA) instrument is a visible and near-infrared imaging spectrometer on board the European Mars Express (MEx) mission. The on-board calibration (OBC) performed at the beginning of observations on each orbit reveals that the photometric response of the C channel (1.0–2.5 μm) has been very stable since orbit insertion in January 2004. On the contrary the L channel (2.5–5.1 μm) response has varied significantly during the mission, and only orbits for which the response is close to nominal could be used with confidence. The spatial coverage of ice-free surfaces in this wavelength range is consequently limited to only ～30%, mainly during northern spring and summer. This paper presents the empirical method used to derive new instrumental transfer functions (ITF) for the non-nominal orbits. This method consists of analyzing the variation of the signal between several observations of a same region acquired at nominal and non-nominal calibration states. In the cases where the mineralogy and the atmospheric conditions between the two observations are the same, the variation in reflectance spectra is only due to the ITF variation, which provides a new ITF. We then associate these new ITFs with their corresponding OBCs to model a relationship between both. The resulting model enables us to provide a new ITF for each orbit for which the OBC is available. The new ITFs derived for the entire dataset have been validated (1) through a comparison of the C and L channel global albedo trends and (2) through a comparison of the surface temperatures derived from the L channel with those calculated from the General Circulation Model (GCM) numerical simulation of the LMD released in the Martian Climate Database. The non-nominal data processed with adapted ITFs for orbits up to 3050 increase the non-icy surface coverage of Mars to ～70% including all seasons.  相似文献   

Intense fracturing and fracture sealing induced by mineral growth in porous rocks     

Catherine Noiriel  François Renard  Mai-Linh Doan  Jean-Pierre Gratier 《Chemical Geology》2010,269(3-4):197-209

Mineral precipitation in the pores of a rock may exert a force, which is called crystallization pressure. This process has been studied experimentally and results bring a new look on the way fractures may develop and seal in natural systems. Cylindrical core samples of porous limestone and sandstone were left for several weeks in contact with an aqueous solution saturated with sodium chloride, at 30 or 45 °C, under axial normal stress in the range 0.02–0.26 MPa. The fluid was allowed to rise in the core samples by capillary forces, up to a controlled height where evaporation and precipitation occurred. The uniaxial deformation of the samples was measured using high-resolution displacement sensors. The samples were characterized using computed X-ray tomography, allowing therefore imaging in 3D the intensity and localization of the damage. Two kinds of damage could be observed. Firstly, small rock fragments were peeled from the sample surface. Secondly, and more interestingly, fracture networks developed, by nucleation of microcracks at the interface where evaporation occurred, and propagation to the free surface. Two families of fractures could be identified. A first set of sealed fracture parallel to the evaporation front is directly induced by crystallization pressure. A second fracture network, perpendicular to the evaporation front, accommodates the first set of fractures. An analytical model where fluid flow is coupled to evaporation, vapour transport, and localization of mineral precipitation explains the shape of this fracture network.  相似文献   

Model of molecular structure of the insoluble organic matter isolated from Murchison meteorite     

Sylvie DERENNE  François ROBERT 《Meteoritics & planetary science》2010,45(9):1461-1475

Abstract– The molecular structure of the insoluble organic matter (IOM) from Murchison meteorite has been investigated by our group for several years using a large set of analytical methods including various spectroscopies (Fourier transform infrared spectroscopy, nuclear magnetic resonance, electron paramagnetic resonance, X‐ray absorption near‐edge spectroscopy), high resolution electron microscopy, and thermal (pyrolyses in the presence or not of tetramethylammonium hydroxide) and chemical (RuO₄ oxidation) degradations. Taken together, these techniques provided a wealth of qualitative and quantitative information, from which we derived 11 elemental and molecular parameters on the same IOM residue. In addition to the basic elemental composition, these parameters describe the distribution of the different types of carbon, nitrogen, and sulfur atoms as well as the size of the polyaromatic units. For this molecular structure, we therefore propose a model which fits with these 11 molecular quantitative parameters. Several cosmochemical implications are derived from this structure. Based on the fact that aromatic moieties are highly substituted and aliphatic chains highly branched, it can be anticipated that the synthesis of this IOM occurred through successive additions of single carbon units in the gas‐phase ending by a spontaneous cyclization for chain length ≥7 C. As a whole, these observations favor an organosynthesis in the solar T‐Tauri disk.  相似文献   

Interaction between tectonic and erosion processes on the morphogenesis of an Alpine valley: geological and geophysical investigations in the lower Romanche valley (Belledonne massif, western Alps)     

Olivier Le Roux  Stéphane Schwartz  Jean François Gamond  Denis Jongmans  Pierre Tricart  Michel Sebrier 《International Journal of Earth Sciences》2010,99(2):427-441

In the Belledonne massif, the steep Paleozoic Belledonne Middle Fault (BMF) separates micaschists, displaying numerous landslides, from amphibolites. The massif is incised by the lower Romanche river valley. When crossing the BMF, the valley widens into a lozenge-shaped basin recently interpreted as an active pull-apart type structure associated with a major N110 striking Quaternary fault. Multidisciplinary investigations were carried out in the basin to check if this model has implications on the seismic and landslide hazard assessment. This study demonstrated the existence of a N80 sinistral strike slip Séchilienne Fault Zone (SFZ). This fault zone is suspected to offset the BMF by 375 m across the basin. Geophysical experiments revealed that the bedrock depth increases strongly in the basin, up to 350 m. Our study invalidates the active pull-apart origin of the basin and suggests it results from Quaternary glacial and fluvial erosion processes, magnified by the intersection of two inherited structures, the BMF and the SFZ.  相似文献   

Spaceborne remote sensing of greenhouse gas concentrations     

François-Marie Bréon  Philippe Ciais 《Comptes Rendus Geoscience》2010,342(4-5):412-424

Despite their primary contribution to climate change, there are still large uncertainties on the sources and sinks of the main greenhouse gases: carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O). A better knowledge of these sources is necessary to understand the processes that control them and therefore to predict their variations. Indeed, large feedbacks between climate change and greenhouse gas fluxes are expected during the 21st century. Sources and sinks of these gases generate spatial and temporal gradients that can be measured either in situ or from space. One can then estimate the surface fluxes, either positive or negative, from concentration measurements through a so-called atmospheric inversion. Surface measurements are currently used to estimate the fluxes at continental scales. The high density of spaceborne observations allows potentially a much higher resolution. Several remote sensing techniques can be used to measure atmospheric concentration of greenhouse gases. These techniques have motivated the development of spaceborne instruments, some of them already in space and others under development. However, the accuracy of the current estimates is still not sufficient to improve our knowledge on the greenhouse gases sources and sinks. Rapid improvements are expected during the forthcoming years with a strong implication of the scientific community and the launch of dedicated instruments, optimized for the measurement of CO₂ and CH₄ concentrations.  相似文献   

Lithosphere dynamics and sedimentary basins: the Arabian plate and analogues     

François Roure  Magdalena Scheck-Wenderoth  Abdullah Gahnoog  Tim Pharaoh 《Arabian Journal of Geosciences》2010,3(4):327-329

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Forward kinematic modelling of a regional transect in the Northern Emirates using geological and apatite fission track age constraints on paleo-burial history     

Mihai Tarapoanca  Paul Andriessen  Karine Broto  Louis Chérel  Nadine Ellouz-Zimmermann  Jean-Luc Faure  Anne Jardin  Charles Naville  François Roure 《Arabian Journal of Geosciences》2010,3(4):395-411

This paper aims to simulate the kinematic evolution of a regional transect crossing the Northern Emirates in the northernmost part of the Semail Ophiolite and the Dibba zone, just south of the Musandam Platform exposures. The studied section comprises, from top to bottom and from inner to outer zones, (1) the erosional remnants of the Semail Ophiolite, mainly made up of serpentinized ultramafics in the west and gabbros in the east, (2) high-grade metamorphic rocks which are currently exposed in the core of a nappe anticline near Masafi, (3) far-travelled Hawasina basinal units and Sumeini paleo-slope units of the Dibba Zone, (4) parautochthonous platform carbonates, which are currently well exposed in the Musandam area, and (5) a flexural basin filled with uppermost Cretaceous to Neogene sediments. Two main compressional episodes are generally identified, resulting first in the obduction of the Semail Ophiolite and then in the stacking of underlying platform carbonate units of the former Arabian passive margin, thus accounting for the present architecture of this transect: (1) first, deformation at the plate boundary initiated in the Late Cretaceous, resulting in the obduction of the Semail Ophiolite and the progressive accretion of the Hawasina and Sumeini tectonic wedge on top of the Arabian foreland, leading to a progressive bending of its lithosphere and development of a wide flexural basin; (2) compression resumed during the Neogene, leading to the tectonic stacking of the parautochthonous platform duplexes of Musandam and Margham trends, the development of out-of-sequence thrusts and triangle zones, refolding of the sole thrust of the former Late Cretaceous accretionary wedge and coeval normal (?) high-angle faulting along the contact between the Musandam and Dibba zones. However, seismic profiles and paleo-thermometers also help in identifying another erosional event at the boundary between the Paleogene Pabdeh and the Neogene Fars series. Evidenced by the local erosional truncation of the Pabdeh series in the vicinity of the frontal triangle zone (i.e. the inner part of the former Late Cretaceous foredeep), this Paleogene uplift/unroofing episode is tentatively interpreted here as an evidence for a continuum of compressional deformation lasting from the Late Cretaceous to the Middle Miocene although one may alternatively speculate that it was related to the detachment of the subducted slab. Although carbonate facies are usually not suitable for apatite fission track (AFT) studies, we were able to extract detrital apatites from quartz-bearing Triassic dolomites in the Musandam area. However, the yield and the quality were both poor and too few fission track lengths could be measured, making it difficult to interpret the meaning of the FT ages. The FT dates obtained in this study are therefore compared with those existing in the literature. Fortunately enough, for each sample, at least ten apatite crystals could be used for fission track dating, except for site 6 with only five datable apatite grains. The obtained apatite fission track dates between 28 and 13 Ma, much younger than the Triassic age of the series, are taken to represent reset fission track ages, implying erosion of an up-to-3-km-thick pile of Jurassic–Cretaceous carbonates and Hawasina allochthon during the Neogene. Apatite fission track dates from the ~95 M-old plagiogranites of the Semail complex (Searle and Cox, Geol Mag 139(3):241–255, 2002) obtained in this study and compared with those recently published provide evidences for more than one cooling event. An early unroofing of the ophiolite during the Late Cretaceous is revealed in fission track dates of 72–76 Ma at the top of the ophiolite in the east, which are coeval and also consistent with the occurrence of paleo-soils, rudists and paleo-reefs on top of serpentinized ultramafics in the west. High-pressure rocks at As Sifah in the southeast near Muscat revealed apatite fission track data ranging from ~46 to 63 Ma (Gray et al. 2006). The leucocratic part of the ophiolite (sample UAE 180) yielded comparable young apatite (40.6?±?3.9 Ma) and zircon (46.6?±?4.3 Ma) FT dates. A Cenozoic (~20–21 Ma) exhumation has been determined for the Bani Hamid metamorphic sole in northern Oman, applying low temperature geochronology and combining apatite FT and apatite (U–Th)/He analyses (Gray et al. 2006). In this study, young apatite fission track dates of 20 Ma have also been found but at the base of the ophiolite near Masafi, in the core of the nappe anticline, thus indicating a Neogene age for the refolding of the allochthon and stacking of underlying parautochthonous platform carbonate units. During the subsequent 2D forward Thrustpack kinematic modelling of the regional transect, these AFT data-set has been used, together with available subsurface information, to reconstruct the past architecture of the structural sections through time, accounting for incremental deformation along the various decollement levels, synorogenic sedimentation and erosion, as well as for successive bending and unbending episodes of the Arabian lithosphere.  相似文献   

New constrains on the thickness of the Semail ophiolite in the Northern Emirates     

Charles Naville  Martine Ancel  Paul Andriessen  Patrice Ricarte  François Roure 《Arabian Journal of Geosciences》2010,3(4):459-475

Near-critical angle and refraction studies were performed at IFP as piggyback studies during a wider programme of crustal imagery operated by WesternGeco on behalf of the Ministry of Energy of the United Arab Emirates. The main objective is to illuminate the base of the Semail Ophiolite along part of a regional transect (D1) crossing the Northern Emirates from the Gulf of Oman in the east up to the Arabian Gulf in the west. Results confirm that the sole thrust of the ophiolite has been folded during the Miocene stacking of the underlying Arabian Platform. The thickness of the ophiolite grades from zero in the core of the Masafi tectonic window, up to a maximum of 1.7 km below the axial part of a successor basin which has been preserved on top of the serpentinite west of the current exposure of the main ultramafic bodies. Apatite grains extracted from plagiogranites of the Semail ophiolite also provide evidences for an early unroofing of the gabbros and plagiogranites during the Late Cretaceous, with cooling ages of 72–76 Ma at the top of the ophiolite in the east (not far from the Fujairah coast line), which are coeval and also consistent with the occurrence of Late Cretaceous paleo-soils, rudists and paleo-reef deposits on top of serpentinized ultramafics in the west. Younger cooling ages of 20 Ma have been also found at the base of the ophiolite near Masafi, in the core of the nappe anticline, thus providing a Neogene age for the refolding of the allochthon and stacking of underlying parautochthonous platform carbonate units. These results, together with the occurrence of a thick sedimentary pile illuminated below the metamorphic sole along the north-trending, strike-profile D2 running parallel to the axis of the Masafi window, should stimulate a renewal of the exploration in the central part of the Emirate foothills, where the ophiolite thickness is currently limited, and was already drastically reduced by the end of its Late Cretaceous obduction.  相似文献   

Modern Sphagnumδ13C signatures follow a surface moisture gradient in two boreal peat bogs,James Bay lowlands,Québec     

Julie Loisel  Michelle Garneau  Jean‐François Hélie 《第四纪科学杂志》2009,24(3):209-214

Carbon isotopic composition of Sphagnum macrofossils can potentially be used as a palaeohydrological tool for peat‐based climatic studies since a relationship between Sphagnum δ¹³C values and peatland surface moisture has been presented in previous studies. In order to verify this hypothesis, modern Sphagnum δ¹³C values were measured along a moisture (microtopographic) gradient in two boreal peat bogs. Isotopic measurements were performed on bulk material of S. fuscum, S. magellanicum, S. capillifolium and S. pulchrum. Isotopic variations found within and between Sphagnum species along the microtopographic gradient were compared using analysis of variance. A significant positive correlation (P < 0.0001) was found between Sphagnum δ¹³C values and their position along the surface moisture gradient. Results show that ¹³C‐depleted values are related to low water table depths (WTD), while ¹³C‐enriched values correspond to a water table that is close to the peat surface. Although the mechanisms underlying carbon fractionation processes in mosses are not well understood, we demonstrate that water resistance to CO₂ diffusion is an important fractionation process that is observed in bulk Sphagnum δ¹³C measurements, since drier and wetter samples exhibit consistent and very different isotopic signatures. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献