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261.
Multivariate Prediction of Total Water Storage Changes Over West Africa from Multi-Satellite Data 总被引:1,自引:1,他引:0
Ehsan Forootan Jürgen Kusche Ina Loth Wolf-Dieter Schuh Annette Eicker Joseph Awange Laurent Longuevergne Bernd Diekkrüger Michael Schmidt C. K. Shum 《Surveys in Geophysics》2014,35(4):913-940
West African countries have been exposed to changes in rainfall patterns over the last decades, including a significant negative trend. This causes adverse effects on water resources of the region, for instance, reduced freshwater availability. Assessing and predicting large-scale total water storage (TWS) variations are necessary for West Africa, due to its environmental, social, and economical impacts. Hydrological models, however, may perform poorly over West Africa due to data scarcity. This study describes a new statistical, data-driven approach for predicting West African TWS changes from (past) gravity data obtained from the gravity recovery and climate experiment (GRACE), and (concurrent) rainfall data from the tropical rainfall measuring mission (TRMM) and sea surface temperature (SST) data over the Atlantic, Pacific, and Indian Oceans. The proposed method, therefore, capitalizes on the availability of remotely sensed observations for predicting monthly TWS, a quantity which is hard to observe in the field but important for measuring regional energy balance, as well as for agricultural, and water resource management. Major teleconnections within these data sets were identified using independent component analysis and linked via low-degree autoregressive models to build a predictive framework. After a learning phase of 72 months, our approach predicted TWS from rainfall and SST data alone that fitted to the observed GRACE-TWS better than that from a global hydrological model. Our results indicated a fit of 79 % and 67 % for the first-year prediction of the two dominant annual and inter-annual modes of TWS variations. This fit reduces to 62 % and 57 % for the second year of projection. The proposed approach, therefore, represents strong potential to predict the TWS over West Africa up to 2 years. It also has the potential to bridge the present GRACE data gaps of 1 month about each 162 days as well as a—hopefully—limited gap between GRACE and the GRACE follow-on mission over West Africa. The method presented could also be used to generate a near-real-time GRACE forecast over the regions that exhibit strong teleconnections. 相似文献
262.
This Special Issue on “Mass Distribution and Mass Transport in the Earth System: Recent Scientific Progress due to Interdisciplinary Research” reports a number of findings resulting from a collaborative effort run from 2006 until 2013, in the framework of the DFG Priority Program 1257 “Mass Distribution and Mass Transport in the Earth System”. Contributions have been arranged along five lines, i.e. (1) improvements in geodesy: satellite mass monitoring through gravimetry and altimetry, (2) applications in large-scale hydrology, (3) applications in solid Earth research, (4) applications in cryospheric research, (5) applications in ocean sciences. 相似文献
263.
Analysis of spatial and temporal extreme monsoonal rainfall over South Asia using complex networks 总被引:2,自引:1,他引:1
We present a detailed analysis of summer monsoon rainfall over the Indian peninsular using nonlinear spatial correlations. This analysis is carried out employing the tools of complex networks and a measure of nonlinear correlation for point processes such as rainfall, called event synchronization. This study provides valuable insights into the spatial organization, scales, and structure of the 90th and 94th percentile rainfall events during the Indian summer monsoon (June–September). We furthermore analyse the influence of different critical synoptic atmospheric systems and the impact of the steep Himalayan topography on rainfall patterns. The presented method not only helps us in visualising the structure of the extreme-event rainfall fields, but also identifies the water vapor pathways and decadal-scale moisture sinks over the region. Furthermore a simple scheme based on complex networks is presented to decipher the spatial intricacies and temporal evolution of monsoonal rainfall patterns over the last 6 decades. 相似文献
264.
Karsten Osenbrück Jürgen Sültenfuß Stephan M. Weise 《Geochimica et cosmochimica acta》2009,73(4):911-289
Groundwater is an important and often exclusive water resource in arid and semi-arid regions. The aim of the present paper was to gain insight into the processes and conditions that control the deterioration of groundwater quality in the semi-arid Kalahari of Botswana. Measurements of 3He, 4He, 20Ne, 22Ne, and of 14C of dissolved inorganic carbon (DIC) were combined with existing isotopic and hydrochemical data to investigate groundwater from the Ntane Sandstone Aquifer, which is affected by high nitrate concentrations of non-anthropogenic origin. All groundwater samples revealed neon concentrations in excess to air-saturated water, which we attributed to the addition of excess air during recharge. Neon concentrations ranged from values close to air saturation for 14C DIC rich samples (up to 80.5%MC) up to values of 90% in excess to air-saturated water for lower 14C DIC contents (2.6-61.3%MC). A strong linear correlation of excess Ne with nitrate concentrations suggests an intimate connection between groundwater quality and the processes and conditions during groundwater recharge. Low groundwater recharge rates under present-day semi-arid conditions are associated with low amounts of excess Ne and elevated nitrate concentrations. In contrast to this, higher excess Ne values in groundwater of lower 14C DIC and nitrate contents indicate that the high quality groundwater end-member presumably is related to higher groundwater table fluctuations during wetter climatic conditions in the past. We attribute the decline in groundwater quality with respect to nitrate to a decreasing rate and temporal variability of groundwater recharge, and to concurrent changes in biogeochemical activities following a transition to a drier climate during the Holocene. Under such conditions, a much stronger decrease in groundwater recharge compared to the release of nitrate from soil organic matter may result in elevated nitrate concentrations in the vadose zone and groundwater. This implies a strong impact of climate change on the transport of solutes like nitrate through the vadose zone which needs to be considered in predictions of future groundwater quality. 相似文献
265.
John Menzies Jürgen M. Reitner 《Proceedings of the Geologists' Association. Geologists' Association》2019,130(2):196-209
Tills from an exposure in Wildschönau Valley, northern Austria were examined using microsedimentological techniques. The tills exhibit a range of microstructures indicative of soft sediment deformation within temperate subglacial bed conditions. The tills can be subdivided at the macroscale into a lower grey and upper red till both of which exhibit some sedimentological variations; however, at the micro-level the tills appear essentially identical. The microstructures in the tills are illustrative of structures developed during deformation both during and following their emplacement. Of note are the microshears within these tills that are demonstrative of changes in applied stress. Both low (<25°) and high angle (>25°) microshears were mapped and their fabric data analyzed. The microshears show a change in stress levels ascending through successive till units. The changes in stress are demonstrative of spatially and temporally changing rheological conditions undergone by the subglacial tills during deformation, ongoing deposition/ emplacement and stress localization. These findings indicate that microstructures reveal local deformation conditions in tills and a more detailed micro-history of paleo-stress. 相似文献
266.
Effect of water on the fluorine and chlorine partitioning behavior between olivine and silicate melt
Bastian?JoachimEmail authorView authors OrcID profile André?Stechern Thomas?Ludwig Jürgen?Konzett Alison?Pawley Lorraine?Ruzié-Hamilton Patricia?L.?Clay Ray?Burgess Christopher?J.?Ballentine 《Contributions to Mineralogy and Petrology》2017,172(4):15
Halogens show a range from moderate (F) to highly (Cl, Br, I) volatile and incompatible behavior, which makes them excellent tracers for volatile transport processes in the Earth’s mantle. Experimentally determined fluorine and chlorine partitioning data between mantle minerals and silicate melt enable us to estimate Mid Ocean Ridge Basalt (MORB) and Ocean Island Basalt (OIB) source region concentrations for these elements. This study investigates the effect of varying small amounts of water on the fluorine and chlorine partitioning behavior at 1280?°C and 0.3 GPa between olivine and silicate melt in the Fe-free CMAS+F–Cl–Br–I–H2O model system. Results show that, within the uncertainty of the analyses, water has no effect on the chlorine partitioning behavior for bulk water contents ranging from 0.03 (2) wt% H2O (DCl ol/melt = 1.6?±?0.9 × 10?4) to 0.33 (6) wt% H2O (DCl ol/melt = 2.2?±?1.1 × 10?4). Consequently, with the effect of pressure being negligible in the uppermost mantle (Joachim et al. Chem Geol 416:65–78, 2015), temperature is the only parameter that needs to be considered for the determination of chlorine partition coefficients between olivine and melt at least in the simplified iron-free CMAS+F–Cl–Br–I–H2O system. In contrast, the fluorine partition coefficient increases linearly in this range and may be described at 1280?°C and 0.3 GPa with (R 2?=?0.99): \(D_{F}^{\text{ol/melt}}\ =\ 3.6\pm 0.4\ \times \ {{10}^{-3}}\ \times \ {{X}_{{{\text{H}}_{\text{2}}}\text{O}}}\left( \text{wt }\!\!\%\!\!\text{ } \right)\ +\ 6\ \pm \ 0.4\times \,{{10}^{-4}}\). The observed fluorine partitioning behavior supports the theory suggested by Crépisson et al. (Earth Planet Sci Lett 390:287–295, 2014) that fluorine and water are incorporated as clumped OH/F defects in the olivine structure. Results of this study further suggest that fluorine concentration estimates in OIB source regions are at least 10% lower than previously expected (Joachim et al. Chem Geol 416:65–78, 2015), implying that consideration of the effect of water on the fluorine partitioning behavior between Earth’s mantle minerals and silicate melt is vital for a correct estimation of fluorine abundances in OIB source regions. Estimates for MORB source fluorine concentrations as well as chlorine abundances in both mantle source regions are within uncertainty not affected by the presence of water. 相似文献
267.
Among 2187 nights of airglow observations of the OH(6-2) and O2b(0-1) bands from Argentina (mainly from El Leoncito, 32°S 69°W), 132 show airglow brightness jumps (ABJs) of short duration (16 min median). ABJs are supposed to be related to mesospheric bores or similar nonlinear waves. Several occurrence patterns were identified, which a successful explanation must take into account. ABJs occur preferably in the OH layer at 87 km, and are less likely in the O2 layer at 95 km, maybe because ducts prefer lower altitudes. The seasonal distribution of nights when ABJs are observed only in the OH layer clearly shows a winter maximum centered around solstice, and equinox minima. In contrast, the seasonal distribution of ABJ nights in O2 is flat. Most ABJs simultaneously present in OH and O2 show anticorrelated variation between both layers. ABJ nights tend to occur in clusters lasting several days, which probably reflects duct lifetime. 相似文献
268.
Spatial sampling design and covariance-robust minimax prediction based on convex design ideas 总被引:2,自引:2,他引:0
Gunter Spöck Jürgen Pilz 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(3):463-482
This paper presents new ideas on sampling design and minimax prediction in a geostatistical model setting. Both presented
methodologies are based on regression design ideas. For this reason the appendix of this paper gives an introduction to optimum
Bayesian experimental design theory for linear regression models with uncorrelated errors. The presented methodologies and
algorithms are then applied to the spatial setting of correlated random fields. To be specific, in Sect. 1 we will approximate an isotropic random field by means of a regression model with a large number of regression functions
with random amplitudes, similarly to Fedorov and Flanagan (J Combat Inf Syst Sci: 23, 1997). These authors make use of the
Karhunen Loeve approximation of the isotropic random field. We use the so-called polar spectral approximation instead; i.e.
we approximate the isotropic random field by means of a regression model with sine-cosine-Bessel surface harmonics with random
amplitudes and then, in accordance with Fedorov and Flanagan (J Combat Inf Syst Sci: 23, 1997), apply standard Bayesian experimental
design algorithms to the resulting Bayesian regression model. Section 2 deals with minimax prediction when the covariance function is known to vary in some set of a priori plausible covariance
functions. Using a minimax theorem due to Sion (Pac J Math 8:171–176, 1958) we are able to formulate the minimax problem as
being equivalent to an optimum experimental design problem, too. This makes the whole experimental design apparatus available
for finding minimax kriging predictors. Furthermore some hints are given, how the approach to spatial sampling design with
one a priori fixed covariance function may be extended by means of minimax kriging to a whole set of a priori plausible covariance
functions such that the resulting designs are robust. The theoretical developments are illustrated with two examples taken
from radiological monitoring and soil science. 相似文献
269.