A new U–Pb zircon age and a volcanogenic model for the early Permian Chemnitz Fossil Forest     

Luthardt  Ludwig  Hofmann  Mandy  Linnemann  Ulf  Gerdes  Axel  Marko  Linda  Rößler  Ronny 《International Journal of Earth Sciences》2018,107(7):2465-2489

International Journal of Earth Sciences - The Chemnitz Fossil Forest depicts one of the most completely preserved forest ecosystems in late Paleozoic Northern Hemisphere of tropical Pangaea. Fossil...  相似文献   

Estimating potential evapotranspiration without continuous daily data: possible errors and impact on water balance simulations     

Ludovic Oudin  Lætitia Moulin  Hocine Bendjoudi  Pierre Ribstein 《水文科学杂志》2013,58(2):209-222

Abstract

Alternative approaches to estimating monthly and annual potential evapotranspiration (PE) are explored in cases where daily climate data are not routinely recorded. A database consisting of data from 222 weather stations, representing a wide variety of climatic conditions, is used to draw general conclusions. In addition, two PE formulae with different data requirements are used: the standard FAO-56 Penman-Monteith equation, and a simple temperature-based equation. First, we tested the degree of bias introduced by using climate data averaged over long time periods instead of daily data. Second, we explored the sensitivity of PE estimation with respect to variations in sampling frequency of climate variables. The results show that using mean weather data has only a limited effect on monthly and annual PE estimates. Conversely, imperfect sampling of weather data may bias monthly and to a lesser extent annual PE estimates if the sampling period exceeds 5 and 10 days, respectively. Finally, we tested the impact of erroneous weather data on the simulations of annual actual evapotranspiration obtained with the Budyko model. The impact on the Budyko model outputs depends more on the dryness index of a given location than on annual PE; for regions under water stress, the errors in estimation of actual evapotranspiration are very limited, compared to humid regions where available energy is the dominating factor and the propagation of PE errors is important.

Citation Oudin, L., Moulin, L., Bendjoudi, H. & Ribstein, P. (2010) Estimating potential evapotranspiration without continuous daily data: possible errors and impact on water balance simulations. Hydrol. Sci. J. 55(2), 209–222.  相似文献   

Interannual variability of air temperature inversions in ice-free area of northern James Ross Island,Antarctica     

Ambrožová  Klára  Láska  Kamil  Matějka  Michael  Reuder  Joachim 《Theoretical and Applied Climatology》2022,148(3-4):967-983

Theoretical and Applied Climatology - Air temperature inversions are common features in Antarctica, especially in the interior where they are observed nearly year-round. Large temporal variability...  相似文献   

Hydraulic fracturing in unconventional gas reservoirs: risks in the geological system, part 2   总被引：2，自引：2，他引：0  

Alexander Kissinger  Rainer Helmig  Anozie Ebigbo  Holger Class  Torsten Lange  Martin Sauter  Michael Heitfeld  Johannes Klünker  Wiebke Jahnke 《Environmental Earth Sciences》2013,70(8):3855-3873

Hydraulic fracturing is a method used for the production of unconventional gas resources. Huge amounts of so-called fracturing fluid (10,000–20,000 m³) are injected into a gas reservoir to create fractures in solid rock formations, upon which mobilised methane fills the pore space and the fracturing fluid is withdrawn. Hydraulic fracturing may pose a threat to groundwater resources if fracturing fluid or brine can migrate through fault zones into shallow aquifers. Diffuse methane emissions from the gas reservoir may not only contaminate shallow groundwater aquifers, but also escape into the atmosphere where methane acts as a greenhouse gas. The working group “Risks in the Geological System” as part of ExxonMobil’s hydrofracking dialogue and information dissemination processes was tasked with the assessment of possible hazards posed by migrating fluids as a result of hydraulic fracturing activities. In this work, several flow paths for fracturing fluid, brine and methane are identified and scenarios are set up to qualitatively estimate under what circumstances these fluids would leak into shallower layers. The parametrisation for potential hydraulic fracturing sites in North Rhine-Westphalia and Lower Saxony (both in Germany) is derived from literature using upper and lower bounds of hydraulic parameters. The results show that a significant fluid migration is only possible if a combination of several conservative assumptions is met by a scenario.  相似文献   

CTBT seismic monitoring using coherent and incoherent array processing     

Kværna  Tormod  Gibbons  Steven J.  Näsholm  Sven Peter 《Journal of Seismology》2021,25(5):1189-1207

Journal of Seismology - The detection and location capability of the International Monitoring System for small seismic events in the continental and oceanic regions surrounding the Sea of Japan is...  相似文献   

Research on geographical education     

Jan Ketil Rød  Per Jarle Sætre  Michael Jones 《Norsk geografisk tidsskrift. Norwegian journal of geography》2013,67(3):117-119

  相似文献   

Pupils' knowledge and awareness of geography when starting upper secondary school in Norway     

Olav Fjær 《Norsk geografisk tidsskrift. Norwegian journal of geography》2013,67(3):135-141

The author, an upper secondary teacher in geography, has conducted various surveys and questionnaires among pupils every year, for 30 years. The article examines his pupils' knowledge of geography when they start upper secondary school. During their first lesson in geography they are presented with a questionnaire designed to test their knowledge of concepts, places, and causal relationships. In addition, they are asked about their perceptions of geography and expectations when they start to study a new subject. The author finds it valuable and important as a teacher to know what his pupils have learned during their lower secondary education because such information could be used to adapt upper secondary education in geography to the pupils' abilities. Further, it is important to motivate, create expectations, and develop awareness of geography. In addition to discussing pupils' knowledge of geography, the article shows briefly how school curricula and geography teaching have changed in Norwegian lower secondary schools since the early 1970s.  相似文献   

Calibration of the New Certified Reference Materials ERM‐AE633 and ERM‐AE647 for Copper and IRMM‐3702 for Zinc Isotope Amount Ratio Determinations     

Kirsten Moeller  Ronny Schoenberg  Rolf‐Birger Pedersen  Dominik Weiss  Shuofei Dong 《Geostandards and Geoanalytical Research》2012,36(2):177-199

The commonly used, but no longer available, reference materials NIST SRM 976 (Cu) and ‘JMC Lyon’ (Zn) were calibrated against the new reference materials ERM^®‐AE633, ERM^®‐AE647 (Cu) and IRMM‐3702 (Zn), certified for isotope amount ratios. This cross‐calibration of new with old reference materials provides a continuous and reliable comparability of already published with future Cu and Zn isotope data. The Cu isotope amount ratio of NIST SRM 976 yielded δ^65/63Cu values of ?0.01 ± 0.05‰ and ?0.21 ± 0.05‰ relative to ERM^®‐AE633 and ERM^®‐AE647, respectively, and a δ^66/64Zn_IRMM‐3702 value of ?0.29 ± 0.05‰ was determined for ‘JMC Lyon’. Furthermore, we separated Cu and Zn from five geological reference materials (BCR‐2, BHVO‐2, BIR‐1, AGV‐1 and G‐2) using a two‐step ion‐exchange chromatographic procedure. Possible isotope fractionation of Cu during chromatographic purification and introduction of resin‐ and/or matrix‐induced interferences were assessed by enriched ⁶⁵Cu isotope addition. Instrumental mass bias correction for the isotope ratio determinations by MC‐ICP‐MS was performed using calibrator‐sample bracketing with internal Ni doping for Cu and a double spike approach for Zn. Our results for the five geological reference materials were in very good agreement with literature data, confirming the accuracy and applicability of our analytical protocol.  相似文献   

Composition and origin of nodules from the ≈20 ka Pomici di Base (PB)-Sarno eruption of Mt. Somma — Vesuvius, Italy     

Rita Klébesz  Robert J. Bodnar  Benedetto De Vivo  Kálmán T?r?k  Annamaria Lima  Paola Petrosino 《Central European Journal of Geosciences》2012,4(2):324-337

Nodules (coarse-grain ??plutonic?? rocks) were collected from the ca. 20 ka Pomici di Base (PB)-Sarno eruption of Mt. Somma-Vesuvius, Italy. The nodules are classified as monzonite-monzogabbro based on their modal composition. The nodules have porphyrogranular texture, and consist of An-rich plagioclase, K-feldspar, clinopyroxene (ferroan-diopside), mica (phlogopite-biotite) ± olivine and amphibole. Aggregates of irregular intergrowths of mostly alkali feldspar and plagioclase, along with mica, Fe-Ti-oxides and clinopyroxene, in the nodules are interpreted as crystallized melt pockets. Crystallized silicate melt inclusions (MI) are common in the nodules, especially in clinopyroxenes. Two types of MI have been identified. Type I consists of mica, Fe-Ti-oxides and/or dark green spinel, clinopyroxene, feldspar and a vapor bubble. Volatiles (CO₂, H₂O) could not be detected in the vapor bubbles by Raman spectroscopy. Type II inclusions are generally lighter in color and contain subhedral feldspar and/or glass and several opaque phases, most of which are confirmed to be oxide minerals by SEM analysis. Some of the opaque-appearing phases that are below the surface may be tiny vapor bubbles. The two types of MI have different chemical compositions. Type I MI are classified as phono-tephrite ?? tephri-phonolite ?? basaltic trachy-andesite, while Type II MI have basaltic composition. The petrography and MI geochemistry led us to conclude that the nodules represent samples of the crystal mush zone in the active plumbing system of Mt. Somma-Vesuvius that were entrained into the upwelling magma during the PB-Sarno eruption.  相似文献   

Erosion mechanisms and sediment sources in a peatland forest after ditch cleaning          下载免费PDF全文

Tapio Tuukkanen  Leena Stenberg  Hannu Marttila  Leena Finér  Sirpa Piirainen  Harri Koivusalo  Bjørn Kløve 《地球表面变化过程与地形》2016,41(13):1841-1853

Ditch cleaning in drained peatland forests increases sediment loads and degrades water quality in headwater streams and lakes. A better understanding of the processes controlling ditch erosion and sediment transport in such systems is a prerequisite for proper peatland management. In order to relate hydrological observations to key erosion processes in headwater peatlands drained for forestry, a two‐year study was conducted in a nested sub‐catchment system (treated with ditch cleaning) and at two reference sites. The treated catchment was instrumented for continuous discharge and turbidity monitoring, erosion pin measurements of changes in ditch bed and banks and time‐integrated sampling of suspended sediment (SS) composition. The results showed that ditch cleaning clearly increased transient suspended sediment concentrations (SSCs) and suspended sediment yields (SSYs), and resulted in temporary storage of loosely deposited organic sediment in the ditch network. After exhaustion of this sediment storage, subaerial processes and erosion from ditch banks became dominant in producing sediment for transport. Recorded SSCs were higher on the rising limbs of event hydrographs throughout the study period, indicating that SS transport was limited by availability of erosion‐prone sediment. A strong positive correlation (R² = 0.84, p < 0.001) between rainfall intensity (above a threshold of 1 mm h^?1) and average SSC obtained on the rising limb of hydrographs for the sub‐catchment showed that soil detachment from ditch banks by raindrop impact can directly increase SSC in runoff. At the main catchment outlet, variation in SSC was best explained (R² = 0.67, p < 0.05) by the linear combination of initial discharge (?), peak discharge (+) and the lag time from initial to peak discharge (?). Based on these factors, ditch cleaning slightly increased peak discharges and decreased transit times in the study catchment. The implications of the results for water pollution management in peatland forests are discussed. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献