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Snow fraction is an important component of land surface models and hydrologic models. Information on snow fraction also improves downstream products retrieved from remote sensing: vertical atmosphere profiles, soil moisture, heat fluxes, etc. The uncertainty of the fractional snow cover estimates must be determined, quantified, and reported to consider the suitability of the product for modeling, data assimilation and other applications. The reflectances of snow and non-snow are characterized by a very significant local variability and also by changes from one scene to another. The local snow and non-snow endmembers are approximated by the Normalized Difference Snow Index with a high accuracy. The magnitudes of snow and non-snow Normalized Difference Snow Indexes are scene-specific and calculated on the fly to retrieve snow fraction. The development of the Normalized Difference Snow Index based algorithms to estimate snow fraction including a scene-specific approach taking local snow and non-snow properties into account is considered an optimal way to fractional snow retrieval from moderate resolution optical remote sensing observations. The Landsat reference data are used to estimate the performance of the fractional snow cover algorithms at moderate resolution and to compare the quality of alternative algorithms. The validation results demonstrate that the performance of the algorithms using Normalized Difference Snow Index has advantages. The advantages achieved in snow fraction retrieval lead to improved estimate of snow water equivalent and changes in snow cover state contributing to better modeling of land surface and hydrologic regime. The success of managing water resources on the whole depends on coordinating described investigations with the works of other researchers developing further enhanced models.

关键词： algorithm remote sensing uncertainty validation snow cover fraction

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Hermite-Discontinuous Galerkin Overset Grid Methods for the Scalar Wave Equation

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Communications on Applied Mathematics and Computation 2021年第3期3卷 391-418页

作者： Oleksii Beznosov Daniel appel Department of Mathematics and Statistics The University of New Mexico1 University of New MexicoMSC011115AlbuquerqueNM 87131Mexico Department of Applied Mathematics University of ColoradoUniversity of Colorado 526 UCBBoulderCO 80309USA

We present high order accurate numerical methods for the wave equation that combines efficient Hermite methods with geometrically flexible discontinuous Galerkin methods by using overset *** boundaries we use thin boundary fitted curvilinear grids and in the volume we use Cartesian grids so that the computational complexity of the solvers approaches a structured Cartesian Hermite *** many other overset methods we do not need to add artificial dissipation but we find that the built-in dissipation of the Hermite and discontinuous Galerkin methods is sufficient to maintain the *** numerical experiments we demonstrate the stability,accuracy,efficiency,and the applicability of the methods to forward and inverse problems.

关键词： Wave equation Overset grids High order Hermite methods Discontinuous Galerkin methods

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Late Holocene Moisture Changes in the Core Area of Arid Central Asia Reflected by Rock Magnetic Records of Glacier Lake Kalakuli Sediments in the Westernmost Tibetan Plateau and their Influences on the Evolution of Ancient Silk Road

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Acta Geologica Sinica(English Edition) 2020年第3期94卷 658-667页

作者： WU Xudong LIU Xingqi Erwin appel College of Environmental Resources and Tourism Capital Normal UniversityBeijing 100048China School of Land Resources and Urban&Rural Planning Hebei Geo UniversityShijiazhuang 050031China Department of Geosciences University of TübingenTübingen 72076Germany

The evolution of Ancient Silk Road(ASR) was deeply influenced by late Holocene moisture changes in Arid Central Asia(ACA). Nevertheless, controversies in Holocene moisture change pattern of ACA and poorly–constrained age models of related studies have made the discussion about late Holocene moisture changes in ACA and their influences on the evolution of ASR difficult. Recently, a high–resolution age model during the late Holocene was established for Kalakuli Lake, a small glacier lake located in the core area of ACA. A thorough rock magnetic investigation was carried out on Kalakuli Lake sediments based on this age model. The magnetic mineral assemblage of Kalakuli Lake sediments is still dominated by primary magnetite despite minor diagenetic effects. Comparisons of rock magnetic records to parameters previously used as indicator of glacier fluctuations suggest that clastic input to Kalakuli Lake was high(low) and magnetic grain size is relatively larger(smaller), when glaciers on Muztagh Ata advanced(retreated). The ARM/SIRM ratio, a magnetic grain size proxy, is directly related to lake hydrodynamics, which are ultimately controlled by glacier fluctuations on Muztagh Ata as the result of regional moisture changes. Late Holocene moisture changes indicated by the ARM/SIRM ratio are consistent with cool/wet and warm/dry oscillations indicated by the unweighted average of biomarker hydrogen isotopic data of the C26 and C28 n–alkanoic acids in a previous study about Kalakuli Lake, most moisture change records of the core area of ACA and winter insolation of the Northern Hemisphere, but opposite to Asian monsoon evolution. Given Asian monsoon and the westerlies are mutually inhibited, we propose that late Holocene moisture changes in the core area of ACA were controlled by the intensity of Asian monsoon versus the westerlies under the governance of solar insolation. Generally increased moisture since the late Holocene indicated by the ARM/SIRM ratio favored cultural e

关键词： moisture changes rock magnetic records Kalakuli Lake Arid Central Asia Ancient Silk Road

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Relationship between magnetic parameters and heavy element contents of arable soil around a steel company,Nanjing

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Science China Earth Sciences 2010年第3期53卷 411-418页

作者： BLAHA U ROESLER W appel E Institute for Geosciences University of Tübingen

Magnetic parameters and element contents were determined in core NJ008 collected from the uppermost ca. 40 cm in a steel company in southwest Nanjing. The results showed that magnetic susceptibility (χ), saturation isothermal remanent magnetization (SIRM) and anhysteretic remanent magnetization (ARM) were enhanced in the uppermost 20 cm, with a mean magnetic susceptibility value of 112.5×10-8 m3 kg-1. Below 20 cm, χ decreased sharply with a mean value of 27.8×10-8m3 kg-1. Low-coercivity minerals such as magnetite dominate in arable soils, while the relative content of antiferromagnetic minerals increases below 20 cm. Heavy metals (Ni, Cu, Fe, Pb, V, and Zn) have similar vertical trends as χ. Principal component analysis reveals common high loadings of the same factor for magnetic concentration parameters (χ, ARM, and SIRM) and elements (Ni, Cu, Fe, Pb, V, and Zn) with an excellent linear correlation (0.69≤R≤0.98) between them. Magnetic susceptibility of paddy soil core NJ013, which had the same parent material as NJ008 but was far from pollution sources, showed stable values of magnetic concentration parameters along the whole core. Absolute values correspond to the so-called magnetic background value (below 20 cm) of NJ008. This indicates that pesticide and fertilizer had little effect on magnetic signals of the upper part of core NJ008 and the extremely enhanced magnetic concentration parameters originate from the steel company emission. Although, the arable soil does not reveal the pollution history and transportation due to annual ploughing, the significant linear relationship between magnetic concentration parameters and heavy metal contents suggests that magnetic parameters can serve as a proxy for quickly detecting soil metallic pollution and estimating the extent of contamination.

关键词： steel company soil heavy metal magnetic parameters

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The enhanced element enrichment in the supercritical states of granite–pegmatite systems

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Acta Geochimica 2019年第3期38卷 335-349页

作者： Rainer Thomas Paul Davidson Karen appel Section 3.6.Chemistry and Physics of Earth Materials Helmholtz-Centre Potsdam German Research Centre for Geoscience – GFZ CODES Centre for Ore Deposit and Earth Sciences School of Natural Sciences University of Tasmania High Energy Density scientific instrument European X-Ray Free-Electron Laser Facility GmbH

In this paper, we show that supercritical fluids have a greater significance in the generation of pegmatites,and for ore-forming processes related to granites than is usually assumed. We show that the supercritical melt or fluid is a silicate phase in which volatiles; principally H_2O are completely miscible in all proportions at magmatic temperatures and pressures. This phase evolves from felsic melts and changes into hydrothermal fluids, and its unique properties are particularly important in sequestering and concentrating low abundance elements, such as metals. In our past research, we have focused on processes observed at upper crustal levels, however extensive work by us and other researchers have demonstrated that supercritical melt/fluids should be abundant in melting zones at deep-crustal levels too. We propose that these fluids may provide a connecting link between lower and upper crustal magmas,and a highly efficient transport mechanism for usually melt incompatible elements. In this paper, we explore the unique features of this fluid which allow the partitioning of variouselements and compounds, potentially up to extreme levels,and may explain various features both of mineralization and the magmas that produced them.

关键词： Granites Pegmatites Supercritical state Extreme element enrichment

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