The relation between degree-2160 spectral models of Earth’s gravitational and topographic potential: a guide on global correlation measures and their dependency on approximation effects     

Christian?HirtEmail author  Moritz?Rexer  Sten?Claessens  Reiner?Rummel 《Journal of Geodesy》2017,91(10):1179-1205

Comparisons between high-degree models of the Earth’s topographic and gravitational potential may give insight into the quality and resolution of the source data sets, provide feedback on the modelling techniques and help to better understand the gravity field composition. Degree correlations (cross-correlation coefficients) or reduction rates (quantifying the amount of topographic signal contained in the gravitational potential) are indicators used in a number of contemporary studies. However, depending on the modelling techniques and underlying levels of approximation, the correlation at high degrees may vary significantly, as do the conclusions drawn. The present paper addresses this problem by attempting to provide a guide on global correlation measures with particular emphasis on approximation effects and variants of topographic potential modelling. We investigate and discuss the impact of different effects (e.g., truncation of series expansions of the topographic potential, mass compression, ellipsoidal versus spherical approximation, ellipsoidal harmonic coefficient versus spherical harmonic coefficient (SHC) representation) on correlation measures. Our study demonstrates that the correlation coefficients are realistic only when the model’s harmonic coefficients of a given degree are largely independent of the coefficients of other degrees, permitting degree-wise evaluations. This is the case, e.g., when both models are represented in terms of SHCs and spherical approximation (i.e. spherical arrangement of field-generating masses). Alternatively, a representation in ellipsoidal harmonics can be combined with ellipsoidal approximation. The usual ellipsoidal approximation level (i.e. ellipsoidal mass arrangement) is shown to bias correlation coefficients when SHCs are used. Importantly, gravity models from the International Centre for Global Earth Models (ICGEM) are inherently based on this approximation level. A transformation is presented that enables a transformation of ICGEM geopotential models from ellipsoidal to spherical approximation. The transformation is applied to generate a spherical transform of EGM2008 (sphEGM2008) that can meaningfully be correlated degree-wise with the topographic potential. We exploit this new technique and compare a number of models of topographic potential constituents (e.g., potential implied by land topography, ocean water masses) based on the Earth2014 global relief model and a mass-layer forward modelling technique with sphEGM2008. Different to previous findings, our results show very significant short-scale correlation between Earth’s gravitational potential and the potential generated by Earth’s land topography (correlation +0.92, and 60% of EGM2008 signals are delivered through the forward modelling). Our tests reveal that the potential generated by Earth’s oceans water masses is largely unrelated to the geopotential at short scales, suggesting that altimetry-derived gravity and/or bathymetric data sets are significantly underpowered at 5 arc-min scales. We further decompose the topographic potential into the Bouguer shell and terrain correction and show that they are responsible for about 20 and 25% of EGM2008 short-scale signals, respectively. As a general conclusion, the paper shows the importance of using compatible models in topographic/gravitational potential comparisons and recommends the use of SHCs together with spherical approximation or EHCs with ellipsoidal approximation in order to avoid biases in the correlation measures.  相似文献   

Antibetische Faltungen im Gibraltarbogen     

Moritz M. Blumenthal 《International Journal of Earth Sciences》1935,26(6):424-429

Zusammenfassung In einer zu den inneren Gebirgsketten der betischen Cordilleren extern gelegenen Zone stellen sich vielerorts Faltungen von zum Teil bedeutendem Ausmaß ein, die gegen den Hauptstamm des Gebirges gerichtet sind; sie werden als antibetische Faltungen bezeichnet. Solche finden sich auch in dem Flyschgebiet auf der Außenseite des Bogens von Gibraltar. Sie ordnen sich westlich Algeciras in eine Faltenschar ein, deren Konvexität im Grundriß gegen E gerichtet ist.  相似文献   

The effect of natural disasters on FDI attraction: a sector-based analysis over time and space     

Neise  Thomas  Sohns  Franziska  Breul  Moritz  Revilla Diez  Javier 《Natural Hazards》2022,110(2):999-1023

Natural Hazards - Extensive research has addressed the question of why some countries are able to attract a large amount of foreign direct investment (FDI), while others are not. Until now, this...  相似文献   

Spectral analysis of the Earth’s topographic potential via 2D-DFT: a new data-based degree variance model to degree 90,000   总被引：5，自引：4，他引：1  

Moritz Rexer  Christian Hirt 《Journal of Geodesy》2015,89(9):887-909

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Experimental observations of aquifer storage and recovery in brackish aquifers using multiple partially penetrating wells     

Witt  Lilli  M&#;ller  Moritz J.  Gr&#;schke  Maike  Post  Vincent E. A. 《Hydrogeology Journal》2021,29(5):1733-1748

Hydrogeology Journal - Aquifer storage and recovery systems using multiple partially penetrating wells (MPPW-ASR) can form a viable solution to the problem of freshwater buoyancy when using...  相似文献   

Convective heat transfer and the pattern of thermal emission on the gas giants     

Jonathan Aurnou  Moritz Heimpel  Lorraine Allen  Eric King  Johannes Wicht 《Geophysical Journal International》2008,173(3):793-801

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Ultra-high-Degree Surface Spherical Harmonic Analysis Using the Gauss–Legendre and the Driscoll/Healy Quadrature Theorem and Application to Planetary Topography Models of Earth,Mars and Moon     

Moritz Rexer  Christian Hirt 《Surveys in Geophysics》2015,36(6):803-830

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Climate and Forecast Mode Simulations for Antarctica: Implications for Temperature and Wind     

XIN Yufei  Annette RINKE  BIAN Lingen  Klaus DETHLOFF  XIAO Cunde  Moritz MIELKE 《大气科学进展》2010,27(6):1453-1472

Climate and forecast mode simulations with the regional climate model HIRlam-ECHAM(HIRHAM) are evaluated over a pan-Antarctic domain. The ability of the model to simulate temperature and wind profiles in the troposphere is quantified by comparing its results with radiosonde data acquired from the Davis station for January and July 2007. Compared to the climate mode, the forecast mode was found to deliver improved results for temperature and wind simulations at the near surface and in the lower troposphere. The main remaining model bias found was the under-representation of low-level wind jets. Based on ensemble simulations, it is shown that a distinct internal variability is inherent in the climate mode simulations, and associated areas of reduced predictability over Antarctica are identified.  相似文献   

Mineralogy and geochemical environment of formation of the Perama Hill high-sulfidation epithermal Au-Ag-Te-Se deposit, Petrota Graben, NE Greece   总被引：1，自引：0，他引：1  

Panagiotis Christos Voudouris  Vasilios Melfos  Paul G. Spry  Robert Moritz  Constantinos Papavassiliou  George Falalakis 《Mineralogy and Petrology》2011,103(1-4):79-100

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The distribution of nitrate N/N in marine sediments and the impact of benthic nitrogen loss on the isotopic composition of oceanic nitrate     

Moritz F. Lehmann  Daniel M. Sigman  Julie Granger  Greg Cane 《Geochimica et cosmochimica acta》2007,71(22):5384-5404

We report ¹⁵N/¹⁴N ratios of porewater nitrate in sediments from the Bering Sea basin, where microbial nitrate reduction has been identified as a significant sink for fixed nitrogen (N). Strong ¹⁵N enrichment in porewater nitrate is observed as one goes deeper in the sediments and nitrate concentration decreases (δ¹⁵N generally reaches 25-35‰). Analysis of profiles with a one-dimensional diffusion-reaction model yields organism-scale isotope effects for dissimilatory nitrate reduction (ε_cell) of 11‰ to 30‰, in the same range as measured in previous studies of cultures and the marine and lacustrine water column. Estimates of ε_cell, while uncertain, show a negative correlation with bottom water [O₂]; we propose that this relates to the at the depth of denitrification. The N isotope effect at the scale of nitrate sediment-water exchange (ε_app) is ∼0‰ in two unreactive deep sites and is typically <3‰ at more reactive sites at various depths. ε_app is much lower than ε_cell because nitrate consumption is nearly complete at the sediment depth of denitrification, minimizing the escape of ¹⁵N-enriched nitrate from the sediments. In reactive sediments, this is due to rapid denitrification, while in less reactive sediments, it is due to greater diffusive distances for nitrate to the depth of denitrification. The data suggest that low bottom water [O₂] tends to yield more complete expression of ε_cell at the sediment-water scale, due to higher at the depth of denitrification. While porewater ammonium-N isotopes were not measured, our porewater model suggests that, in sediments with high organic matter supply and/or low-[O₂] bottom waters, the efflux and subsequent oxidation of ammonium enriched in ¹⁵N by incomplete nitrification can significantly enhance the total net isotope effect of sedimentary N loss (ε_sed, equivalent to ε_app but including ammonium fluxes). Model analysis of representative sedimentary environments suggests a global mean ε_sed of ∼4‰ (∼2‰ if restricted to seafloor below 1 km depth).  相似文献