Headwaters drive streamflow and lowland tracer export in a large-scale humid tropical catchment     

Christian Birkel  Alicia Correa-Barahona  Marco Martinez-Martinez  Sebastian Granados-Bolaños  Nelson Venegas-Cordero  Kenneth Gutiérrez-García  Sara Blanco-Ramírez  Rafael Quesada-Mora  Vanessa Solano-Rivera  Jasson Mussio-Mora  Andres Chavarría-Palma  Katherine Vargas-Arias  Georgianne W. Moore  Ana Maria Durán-Quesada  Javier Vasquez-Morera  Chris Soulsby  Dörthe Tetzlaff  Edgar Espinoza-Cisneros  Ricardo Sánchez-Murillo 《水文研究》2020,34(18):3824-3841

Headwaters are generally assumed to contribute the majority of water to downstream users, but how much water, of what quality and where it is generated are rarely known in the humid tropics. Here, using monthly monitoring in the data scarce (2,370 km²) San Carlos catchment in northeastern Costa Rica, we determined runoff-area relationships linked to geochemical and isotope tracers. We established 46 monitoring sites covering the full range of climatic, land use and geological gradients in the catchment. Regression and cluster analysis revealed unique spatial patterns and hydrologically functional landscape units. These units were used for seasonal and annual Bayesian tracer mixing models to assess spatial water source contributions to the outlet. Generally, the Bayesian mixing analysis showed that the chemical and isotopic imprint at the outlet is throughout the year dominated by the adjacent lowland catchments (68%) with much less tracer influence from the headwaters. However, the headwater catchments contributed the bulk of water and tracers to the outlet during the dry season (>50%) despite covering less than half of the total catchment area. Additionally, flow volumes seemed to be linearly scaled by area maintaining a link between the headwaters and the outlet particularly during high flows of the rainy season. Stable isotopes indicated mean recharge elevations above the mean catchment altitude, which further supports that headwaters were the primary source of downstream water. Our spatially detailed “snap-shot” sampling enabled a viable alternative source of large-scale hydrological process knowledge in the humid tropics with limited data availability.  相似文献   

Recent developments and the future of low‐T calorimetric investigations in the Earth sciences: Consequences for thermodynamic calculations and databases          下载免费PDF全文

Charles A. Geiger  Edgar Dachs 《Journal of Metamorphic Geology》2018,36(3):283-295

Low‐T calorimetry is an experimental science that measures the thermodynamic function heat capacity, C_p(T), from which the standard third‐law entropy (298.15 K), S°, is calculated. The recent technological development of relaxation calorimetry allows both new experimental strategies and types of C_p investigations to be made, which were previously not possible. The C_p measurements are fast and automated and can be made on mg‐sized mineralogical samples between 2 and 400 K. These advantages, when careful measurement procedures are used, permit better determinations of C_p(T) behaviour. The C_p of synthetic single‐crystal MgO was measured between 5 and 302 K, and S° calculated using relaxation calorimetry to further investigate the method's precision and accuracy. A number of synthetic and natural end‐member or nearly end‐member compositions of silicate garnet were investigated in the past via adiabatic calorimetry, an old and established technique, and more recently and extensively with the relaxation method. First C_p(T) and S° results, using relaxation calorimetry, have been obtained on spessartine (Mn₃Al₂Si₃O₁₂) and knorringite (Mg₃Cr₂Si₃O₁₂). Furthermore, reinvestigations on pyrope (Mg₃Al₂Si₃O₁₂), almandine (Fe₃Al₂Si₃O₁₂), grossular (Ca₃Al₂Si₃O₁₂) and andradite (Ca₃Al₂Si₃O₁₂), often on multiple samples, have resolved uncertainties and certain problems with published thermodynamic data. S° can be affected by various low‐T physical phenomena, such as cooperative magnetic phase transitions or Schottky anomalies at temperatures of <15 K, which were not described fully in some older adiabatic calorimetric studies. New C_p results show that small differences in the thermodynamic behaviour between some natural and synthetic silicates may exist as demonstrated by extensive work on grossular. Important and “new” research questions on the thermodynamic behaviour of minerals are coming to light and are being investigated. The C_p behaviour and S° values for six silicate garnet end‐members are analysed and the latter are compared to the “best fit or optimized” S° values given in various internally consistent thermodynamic databases. Conclusions are drawn on what types and directions of calorimetric study are required in order to obtain better thermodynamic property determinations of minerals, as well as achieving a better understanding of the underlying microscopic physical behaviour that determines the macroscopic C_p and S° functions.  相似文献   

Mapping iron abundances on the surface of Mercury: Predicted spatial resolution of the MESSENGER Gamma-Ray Spectrometer     

Patrick N. Peplowski  David T. Blewett  Brett W. Denevi  Larry G. Evans  David J. Lawrence  Larry R. Nittler  Edgar A. Rhodes  Christina M. Selby  Sean C. Solomon 《Planetary and Space Science》2011,59(13):1654-1658

To illustrate the spatial resolution of measurements of Mercury's surface elemental composition by the Gamma-Ray Spectrometer on the MESSENGER spacecraft after one year of orbital observations, we have simulated a global coverage map of the 846-keV iron gamma-ray count rate. The simulated map suggests that distinct geologic units larger than 800 km in horizontal dimension will be discernable when the difference in Fe abundance between adjacent geologic units exceeds 4 wt%. These results imply that the MESSENGER Gamma-Ray Spectrometer dataset will provide useful information for regional geological studies of the surface of Mercury.  相似文献   

Assessment of global dimming and brightening in IPCC-AR4/CMIP3 models and ERA40   总被引：1，自引：1，他引：0  

Martin Wild  Edgar Schmucki 《Climate Dynamics》2011,37(7-8):1671-1688

Observations indicate that solar radiation incident at the Earth surface underwent substantial decadal variations in the second half of the twentieth century, with a tendency towards reduction from the 1950s to the 1980s (“global dimming”) and a partial recovery thereafter (“brightening”) at widespread locations. The most reliable observational records from the Global Energy Balance Archive (GEBA) are used to evaluate the ability of the climate models participating in CMIP3/IPCC-AR4 as well as the ERA40 reanalysis to reproduce these decadal variations. The results from 23 models and reanalysis are analyzed in five different climatic regions where strong decadal variations in surface solar radiation (SSR) have been observed. Only about half of the models are capable of reproducing the observed decadal variations in a qualitative way, and all models show much smaller amplitudes in these variations than seen in the observations. Largely differing tendencies between the models are not only found under all-sky conditions, but also in cloud-free conditions and in the representation of cloud effects. The ERA40 reanalysis neither reproduces the major decadal variations in SSR, despite strong observational constraints on the temporal evolution of the state of the atmosphere, since time varying aerosol loadings are missing. Climate models and reanalyses are therefore not yet at a stage to provide regionally consistent estimates of decadal changes in SSR. Reproduction of these changes would be essential for an adequate representation of regional scale climate variations and impacts, and short-term (decadal) climate projections.  相似文献   

Are Earth Sciences lagging behind in data integration methodologies?     

Hendrik Paasche  Detlef Eberle  Sonali Das  Antony Cooper  Pravesh Debba  Peter Dietrich  Nontembeko Dudeni-Thlone  Cornelia Gläßer  Andrzej Kijko  Andreas Knobloch  Angela Lausch  Uwe Meyer  Ansie Smit  Edgar Stettler  Ulrike Werban 《Environmental Earth Sciences》2014,71(4):1997-2003

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The formation of an eccentric gap in a gas disc by a planet in an eccentric orbit     

A. Pasha Hosseinbor  Richard G. Edgar  Alice C. Quillen  Amanda LaPage 《Monthly notices of the Royal Astronomical Society》2007,378(3):966-972

We investigate the effect of a planet on an eccentric orbit on a two-dimensional low-mass gaseous disc. At a planet eccentricity above the planet's Hill radius divided by its semimajor axis, we find that the disc morphology differs from that exhibited by a disc containing a planet in a circular orbit. An eccentric gap is created with eccentricity that can exceed the planet's eccentricity and precesses with respect to the planet's orbit. We find that a more massive planet is required to open a gap when the planet is on an eccentric orbit. We attribute this behaviour to spiral density waves excited at corotation resonances by the eccentric planet. These act to increase the disc's eccentricity and exert a torque opposite in sign to that exerted by the Lindblad resonances. The reduced torque makes it more difficult for waves driven by the planet to overcome viscous inflow in the disc.  相似文献   

TOWARD AN INTEGRATED APPROACH TO THE GEOGRAPHY OF INTERNATIONAL TRADE     

Edgar C. Conkling  James E. McConnell 《The Professional geographer》1981,33(1):16-25

An increased global interdependence poses both opportunities and obligations for a revitalized geography of international trade. THis subject area has never acquired a satisfactory focurs because its practitioners have taken a limited view of their topic, have neglected related work in other disciplines, and have failed to consider the policy implications of their study. As a remedy, this paper proposes a geography of international trade based upon three interrelated problem areas: the decision-making processes, the spatial fabric, and the space-time metric of world trade.  相似文献   

A review of: “Fluid mechanics and the environment: Dynamical approaches”     

Edgar Knobloch 《地球物理与天体物理流体动力学》2013,107(3-4):329-330

A Collection of Research Papers Written in Commemoration of the 60th Birthday of Sidney Leibovich, edited by J. L. Lumley, Lecture Notes in Physics: Vol 566, Springer-Verlag Berlin Heidelberg New York, 2001. VI+412 pp., DM 149.00, hardbound (ISBN 3-540-41475-4)  相似文献   

Frequency analysis of short‐duration rainfalls     

W. Edgar Watt  Michael J. Nozdryn‐Plotnicki 《大气与海洋》2013,51(4):387-396

Abstract

An investigation was carried out to determine the appropriateness of a probability distribution and fitting technique commonly used in Canada for rainfall frequency analysis.

The extreme value type 1 (EV1) distribution was assessed for three long‐term Canadian stations: Victoria, St Thomas and Québec. The EV1 distribution appears to provide a reasonable fit for durations varying from 5 min to 6 h, but is not clearly superior to another two‐parameter distribution, the lognormal.

The fitting technique, known as modified moments or regression, was assessed by comparing it with three other fitting techniques: moments, maximum likelihood and adjusted maximum likelihood. This comparison was carried out using Monte Carlo simulation techniques over the parameter space deemed to be representative of short duration rainfall data for Canada. In terms of estimating rainfall amounts of specified return period, the modified moments technique was the poorest with regard to both bias and efficiency. In general, the maximum likelihood estimates were the most efficient and were relatively unbiased.  相似文献   

A calorimetric investigation of spessartine: Vibrational and magnetic heat capacity     

Edgar Dachs  Charles A. Geiger  Eric J. Essene 《Geochimica et cosmochimica acta》2009,73(11):3393-3409

The heat capacity (C_p) of two synthetic spessartine samples (Sps) was measured on 20-30 mg-size samples in the temperature range 2-864 K by relaxation calorimetry (RC) and differential scanning calorimetry (DSC). The polycrystalline spessartine samples were synthesized in two different laboratories at high pressures and temperatures from glass and oxide-mixture starting materials and characterized by X-ray powder diffraction and electron-microprobe analysis. The low-temperature heat capacity data show a prominent lambda transition with a peak at 6.2 K, which is interpreted to be the result of a paramagnetic-antiferromagnetic phase transition. The DSC data around ambient T agree excellently with the RC data and can be represented by the C_p polynomial for T > 250 K: