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61.
Hounkpè Jean Diekkrüger Bernd Afouda Abel A. Sintondji Luc Olivier Crepin 《Natural Hazards》2019,98(3):1021-1050
Natural Hazards - We analysed in the work how change in land use/land cover influences on flood characteristics (frequency and magnitude) using a model inter-comparison approach, statistical... 相似文献
62.
Abel Amirbekyan Volker Michel Frederik J. Simons † 《Geophysical Journal International》2008,174(2):617-628
We present a mathematical framework and a new methodology for the parametrization of surface wave phase-speed models, based on traveltime data. Our method is neither purely local, like block-based approaches, nor is it purely global, like those based on spherical harmonic basis functions. Rather, it combines the well-known theory and practical utility of the spherical harmonics with the spatial localization properties of spline basis functions. We derive the theoretical foundations for the application of harmonic spherical splines to surface wave tomography and summarize the results of numerous numerical tests illustrating the performance of a practical inversion scheme based upon them. Our presentation is based on the notion of reproducing-kernel Hilbert spaces, which lends itself to the parametrization of fully 3-D tomographic earth models that include body waves as well. 相似文献
63.
Abel Guihou Sylvain Pichat Sìlvia Nave Aline Govin Laurent Labeyrie Elisabeth Michel Claire Waelbroeck 《Earth and Planetary Science Letters》2010,289(3-4):520-529
Our study gives new constraints on the response of Atlantic Meridional Overturning Circulation (AMOC) export to various forcings during the Last Glacial Inception. The decay corrected excess sedimentary (231Pa/230Th) activity ratio (hereafter referred to as (Pa/Th)) has been measured over that period in two deep cores from the Western (SU90-11, 44°04′N, 40°01′W, 3645 m) and Eastern (MD01-2446, 39°03′N, 12°37′W, 3547 m) basins of the North Atlantic. Both records display significant changes despite the relatively short half-life of 231Pa (~ 32 kyr) compared to the period we investigate. The (Pa/Th) variability does not correlate to changes in local opal flux normalized to 230Th. Moreover, the (Pa/Th) profiles display a high degree of coherency with indirect proxies of AMOC activity such as the benthic foraminifera δ13C and the mid-latitude summer Sea Surface Temperature in nearby reference cores. These additional pieces of evidence support our interpretation of the (Pa/Th) as reflecting AMOC export. The (Pa/Th) repeatedly underwent rapid changes during the Last Glacial Inception associated with the extension of ice rafted detritus in the North Atlantic, highlighting the control of ice-sheet dynamics through freshwater forcing on AMOC export. AMOC export remains large during periods of ice-sheet growth and its decreases lag the Northern Hemisphere summer insolation forcing. AMOC modulation appears driven by ice-sheet dynamics, itself driven by the seasonal insolation gradient between low and high Northern Hemisphere latitudes and the associated intensity of the meridional oceanic and atmospheric circulation. 相似文献
64.
Modelling blue and green water availability under climate change in the Beninese Basin of the Niger River Basin,West Africa
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Djigbo Félicien Badou Bernd Diekkrüger Evison Kapangaziwiri Mamadou L. Mbaye Yacouba Yira Emmanuel A. Lawin Ganiyu T. Oyerinde Abel Afouda 《水文研究》2018,32(16):2526-2542
The aim of this study was to quantify climate change impact on future blue water (BW) and green water (GW) resources as well as the associated uncertainties for 4 subbasins of the Beninese part of the Niger River Basin. The outputs of 3 regional climate models (HIRHAM5, RCSM, and RCA4) under 2 emission scenarios (RCP4.5 and RCP8.5) were downscaled for the historical period (1976–2005) and for the future (2021–2050) using the Statistical DownScaling Model (SDSM). Comparison of climate variables between these 2 periods suggests that rainfall will increase (1.7% to 23.4%) for HIRHAM5 and RCSM under both RCPs but shows mixed trends (?8.5% to 17.3%) for RCA4. Mean temperature will also increase up to 0.48 °C for HIRHAM5 and RCSM but decrease for RCA4 up to ?0.37 °C. Driven by the downscaled climate data, future BW and GW were evaluated with hydrological models validated with streamflow and soil moisture, respectively. The results indicate that GW will increase in all the 4 investigated subbasins, whereas BW will only increase in one subbasin. The overall uncertainty associated with the evaluation of the future BW and GW was quantified through the computation of the interquartile range of the total number of model realizations (combinations of regional climate models and selected hydrological models) for each subbasin. The results show larger uncertainty for the quantification of BW than GW. To cope with the projected decrease in BW that could adversely impact the livelihoods and food security of the local population, recommendations for the development of adequate adaptation strategies are briefly discussed. 相似文献
65.
Francisco J. Sierro Nils Andersen Maria A. Bassetti Serge Bern Miquel Canals Jason H. Curtis Bernard Dennielou Jose Abel Flores Jaime Frigola Beatriz Gonzalez-Mora Joan O. Grimalt David A. Hodell Gwenael Jouet Marta Prez-Folgado Ralph Schneider 《Quaternary Science Reviews》2009,28(25-26):2867-2881
Direct traces of past sea levels are based on the elevation of old coral reefs at times of sea level highstands. However, these measurements are discontinuous and cannot be easily correlated with climate records from ice cores. In this study we show a new approach to recognizing the imprint of sea level changes in continuous sediment records taken from the continental slope at locations that were continuously submerged, even during periods of sea level lowstand. By using a sediment core precisely synchronized with Greenland ice cores, we were able to recognize major floods of the Mediterranean continental shelf over the past 270 kyr. During the last glacial period five flooding events were observed at the onset of the warmest Greenland interstadials. Consistent correspondence between warm climate episodes and eustatic sea level rises shows that these global flooding events were generated by pronounced melting of the Northern Hemisphere ice sheets, due to rapid intensification of Atlantic Meridional Overturning Circulation.The method described in this study opens a new perspective for inter-hemispheric synchronization of marine climate records if applied in other continental margins from the Southern Hemisphere or the equatorial regions. 相似文献
66.
Russell Main Moses Azong Cho Renaud Mathieu Martha M. O’Kennedy Abel Ramoelo Susan Koch 《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(6):751-761
Quantifying photosynthetic activity at the regional scale can provide important information to resource managers, planners and global ecosystem modelling efforts. With increasing availability of both hyperspectral and narrow band multispectral remote sensing data, new users are faced with a plethora of options when choosing an optical index to relate to their chosen or canopy parameter. The literature base regarding optical indices (particularly chlorophyll indices) is wide ranging and extensive, however it is without much consensus regarding robust indices. The wider spectral community could benefit from studies that apply a variety of published indices to differing sets of species data. The consistency and robustness of 73 published chlorophyll spectral indices have been assessed, using leaf level hyperspectral data collected from three crop species and a variety of savanna tree species. Linear regression between total leaf chlorophyll content and bootstrapping were used to determine the leafpredictive capabilities of the various indices. The indices were then ranked based on the prediction error (the average root mean square error (RMSE)) derived from the bootstrapping process involving 1000 iterative resampling with replacement. The results show two red-edge derivative based indices (red-edge position via linear extrapolation index and the modified red-edge inflection point index) as the most consistent and robust, and that the majority of the top performing indices (in spite of species variability) were simple ratio or normalised difference indices that are based on off-chlorophyll absorption centre wavebands (690–730 nm). 相似文献
67.
David J. Abel Beng Chin Ooi Kian-Lee Tan Soon Huat Tan 《International journal of geographical information science》2013,27(4):353-371
Many geographical applications access data from multiple disparate repositories such as file systems, Geographical Information Systems and database management systems which contain data able to be interrelated. Existing approaches that either built a single repository that contain all the required data or simply interconnect these repositories have not been well received. In this paper, we present the design of the Virtual GIS, a system for distributed spatial data processing in heterogeneous environments. The Virtual GIS is an integrated system that provides all the essential facilities for integrating and retrieving data from multiple component systems.The system isparticularly aimed at extensibility and scalability through distributing the processing load across the component systems and a global frontend. The object-oriented data model is adopted as a common data model to ensure meaningful data sharing. We also employ the fivelevel schema architecture of Sheth and Larson as the framework for system integration. Finally, queries are processed using a five-phase query processing approach. 相似文献
68.
Abel Guihou Sylvain Pichat Aline Govin Silvia Nave Elisabeth Michel Jean-Claude Duplessy Philippe Telouk Laurent Labeyrie 《Quaternary Science Reviews》2011,30(13-14):1576-1582
The Atlantic Meridional Overturning Circulation (AMOC) is a key feature of the climate system. However, its role during climate change is still poorly constrained particularly during an Interglacial to Glacial climate transition and the associated global cooling. We present here the first reconstruction of the evolution of the vertical structure of the rate of the AMOC from the Last Interglaciation to the subsequent glaciation (128,000–60,000 years ago) based on sedimentary (231Pa/230Th) records. We show a deep AMOC during the interglacial warmth Marine Isotope Stage (MIS) 5.5 and a shallower glacial one during glacial MIS 4. The change between these two patterns occurred mostly during the glacial inception, i.e. the transition from MIS 5.5 to MIS 5.4. Our data show that AMOC was enhanced during this latter transition as a consequence of a large increase of the overturning rate of the Intermediate Waters, above 2500 m. We suggest that this AMOC pattern required a reinforced Gulf Stream-North Atlantic Current system that ultimately supported ice-sheet growth by providing heat and moisture to the Northern high latitudes. From MIS 5.4 to MIS 5.1, the AMOC was broadly continuous below 2000 m and supported periods of ice-sheet growth. As a result, a glacial AMOC is triggered at the beginning of MIS 4 due to the extension of ice-sheet and the subsequent reorganization of deep-water formation. This study highlights the role of intermediate waters as a major player during climate change. 相似文献
69.
Acidification is the most common water quality problem in lakes created from previous open cast lignite mines. Aeration of
aquifers and dump materials from mining activities causes pyrite oxidation. Pyrite oxidation products are stored in pore water,
minerals and at the exchange complexes of the aquifers and dump sediments. Rainfall runoff transports sediments on the dump
slope into the lakes. Elutriation of these sediments whithin the lakes releases either acid-producing or acid-neutralizing
agents. At a test site south of Leipzig, the annual erosion rates were quantified by water erosion models (RUSLE, EROSION
2D, PEPP) and field measurements. They ranged from 300 up to 900 tons per hectare. Hydrogen ion equivalent release or binding
at the sediment elutriation was computed from laboratory analysis of the pore-water quality, ion exchange complex and mineral
composition of the sediment. Two of the three investigated sediments contained 3 mmol (eq) acidity per 100 g dry sediment
and revealed saturation with respect to jarosite, jurbanite and gypsum. In the third sediment, 6 mmol (eq) alkalinity per
100 g dry sediment was obtained. The annual net acidity influx was calculated to be about 0.5 million mol (eq) for the lake
of the test site.
Received: 2 November 1998 · Accepted: 26 January 1999 相似文献
70.
Erich F. Abel 《Marine Ecology》1993,14(4):291-312
Abstract. The blennies of the Mediterranean Sea were observed in nature by snorkeling and SCUBA diving. Particular attention was paid to their changeable basic patterns and colouring alternations as effected by ecological and ethological factors. Additionally, the tendency for colour change was tested in differently coloured tanks. These experiments failed to demonstrate the striking adaptations seen in the natural environment, except for a remarkable reaction to black and white. The summary of all known reports is supported by colour illustrations; the problems of the colouring alternations are discussed. 相似文献