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111.
Konstantin Latychev Jerry X. Mitrovica Jeroen Tromp Robert Moucha 《Earth and Planetary Science Letters》2005,240(2):322-327
Predictions of present day secular variations in the Earth's long wavelength geopotential driven by glacial isostatic adjustment (GIA) have previously been analyzed to infer the radial profile of mantle viscosity and to constrain ongoing cryospheric mass balance. These predictions have been based on spherically symmetric Earth models. We explore the impact of lateral variations in mantle viscosity using a new finite-volume formulation for computing the response of 3-D Maxwell viscoelastic Earth models. The geometry of the viscosity field is constrained from seismic-to-mographic images of mantle structure, while the amplitude of the lateral viscosity variations is tuned by a free parameter in the modeling. We focus on the zonal J˙? harmonics for degrees ? = 2,…,8 and demonstrate that large-scale lateral viscosity variations of two to three orders of magnitude have a modest, 5-10%, impact on predictions of J˙2. In contrast, predictions of higher degree harmonics show a much greater sensitivity to lateral variation in viscosity structure. We conclude that future analyses of secular trends (for degree ? > 2) estimated from ongoing (GRACE, CHAMP) satellite missions must incorporate GIA predictions based on 3-D viscoelastic Earth models. 相似文献
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Spectral mixture analysis (SMA) is an image-processing technique used for the analysis of airborne hyperspectral remote-sensing data which consist of a large number of spectral bands, typically over 100. In this paper the possibilities are examined of using SMA for the analysis of Landsat Thematic Mapper satellite data with only six bands in the visible to shortwave-infrared wavelength. We use data from a semi-arid area in the Sanmatenga province of Burkina Faso, an area known to experience land-degradation problems. In SMA, we assume that pixels in an image consist of one or more homogeneous (uniform in character) or pure surfaces, the so called end-members. The end-members were derived from the image data on the basis of specific image characteristics. Field data was collected to describe the characteristics of these end-members in terms of land cover, soil and degradation phenomena. The end-members derived from the image analysis, although statistically pure in terms of image spectral characteristics, prove to be mixtures at a field scale. This lack of purity is explained by the nature of semi-arid areas which is more heterogeneous than that of most other areas. The SMA yielded cover percentages for the end-members from which an unsupervised classification was made. Comparison of the classification with the results of SMA shows that the latter provides information on the amount and spatial distribution of land characteristics such as land degradation. 相似文献
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S. J. Gibowicz Carlo Denis Manfred Koch Chen Yong Michael Manga Tapan Mukerji Gary Mavko W. Bielski Maria Jeleńska Frazer Tabeart Lucia Lovison-Golob Peter Ketelaar Douglas J. Galpin Carlo Denis M. Ghil C. L. Keppenne Tracey K. Tromp Louis François Zbigniew Sorbjan 《Pure and Applied Geophysics》1995,145(2):363-398
116.
Normal-mode splitting due to inner-core anisotropy 总被引：1，自引：0，他引：1
Jeroen Tromp 《Geophysical Journal International》1995,121(3):963-968
117.
Suspension-feeding bivalves and the fate of primary production: An estuarine model applied to Chesapeake Bay 总被引：1，自引：0，他引：1
A probabilistic mathematical model of bivalve suspension-feeding in estuaries is based on bivalve abundance, filtering capacities, and water mixing parameters. We applied the model to five regions of the upper Chesapeake Bay, ranging from shallow tidal fresh habitats to deep mesohaline habitats, for the years 1985 to 1987. Model results indicated that existing suspension-feeding bivalves could consume more than 50% of annual primary production in shallow freshwater and oligohaline reaches of the upper Chesapeake Bay and Potomac River. In deep mesohaline portions of the Chesapeake Bay and Potomac River, suspension-feeding bivalves could consume only 10% of primary production. Independent estimates of benthic carbon demand based on benthic production supported the model predictions. Hydrodynamics of large estuaries restrict the potential of benthic suspension-feeders to crop phytoplankton production because the width and depth of these estuaries limit transport of pelagic waters to the littoral flanks of the estuaries where benthic suspension-feeders can be abundant. Benthic suspension-feeders are dominant consumers in shallow segments of the Chesapeake Bay system, but are suppressed in deeper segments. The suppression is below that set by hydrodynamic limits, and may be due to periodic hypoxia or other factors. Our results suggest that the proposed use of suspension-feeding bivalves to improve water quality of large estuaries will be limited by the depth and width of the estuary, unless the bivalves are suspended in the water column by artificial means. 相似文献
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Niragira Sanctus D’Haese Marijke Buysse Jeroen Van Orshoven Jos Ndimubandi Jean 《GeoJournal》2021,86(2):865-884
GeoJournal - The global farming conditions have gone profound mutations that steadily increased vulnerability among smallholder farmers. As consequence, rural households have set mechanisms of... 相似文献