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Multidisciplinary Analysis (multidisciplinary + analysis)

Distribution by Scientific Domains

Earth and Environmental Science	71%

Selected Abstracts

Decomposition and parallelization strategies for solving large-scale MDO problems

GAMM - MITTEILUNGEN, Issue 2 2007
M. Grauer
During previous years, structural optimization has been recognized as a useful tool within the discriptines of engineering and economics. However, the optimization of large-scale systems or structures is impeded by an immense solution effort. This was the reason to start a joint research and development (R& D) project between the Institute ofMechanics and Control Engineering and the Information and Decision Sciences Institute within the Research Center for Multidisciplinary Analyses and Applied Structural Optimization (FOMAAS) on cluster computing for parallel and distributed solution of multidisciplinary optimization (MDO) problems based on the OpTiX-Workbench. Here the focus of attention will be put on coarsegrained parallelization and its implementation on clusters of workstations. A further point of emphasis was laid on the development of a parallel decomposition strategy calles PARDEC, for the solution of very complex optimization problems which cannot be solved efficiently by sequential integrated optimization. The use of the OptiX-Workbench together with the FEM ground water simulation system FEFLOWis shown for a special water management problem. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Evolution of the stable water isotopic composition of the rain sampled along Sahelian squall lines,

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue S1 2010
Camille Risi
Abstract In the Tropics, the stable isotopic composition (HDO, HO) of precipitation is strongly modulated by convective activity. To better understand how convective processes impact the precipitation isotopic composition, we analyze the isotopic composition of rain collected during the passage of four squall lines over the Sahel (Niamey, Niger) in August 2006 during the African Monsoon Multidisciplinary Analysis (AMMA) campaign. The high-frequency sampling (5,10 min) of the precipitation allows us to investigate the evolution of the precipitation isotopic composition in different phases of the squall lines. Despite a large variability among the different squall lines, some robust isotopic features appear: the W shape of the ,18O evolution and the deuterium excess decrease in the first part of the stratiform zone. To understand more quantitatively how convective processes impact the precipitation isotopic composition, a simple stationary two-dimensional transport model including a representation of cloud microphysics and isotopic fractionation is developed and forced by three-dimensional winds retrieved from the Massachusetts Institute of Technology (MIT) radar on 11 August 2006. The model reproduces the robust observed features and a large sensitivity to the squall-line dynamics. This model suggests that the main controlling factors of the isotopic evolution are (1) squall-line dynamics, especially the downward advection of air at the rear of the squall lines, affecting the vapour composition and, by isotopic equilibration, the subsequent precipitation composition and (2) rain re-evaporation. This suggests that water isotopes have the potential to better constrain squall-line dynamics and rain re-evaporation, and to evaluate the representation of convective processes in numerical models. Copyright © 2009 Royal Meteorological Society [source]

4D-Var assimilation of MERIS total column water-vapour retrievals over land

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 644 2009
Peter Bauer
Abstract Experiments with the active assimilation of total column water-vapour retrievals from Envisat MERIS observations have been performed at the European Centre for Medium-Range Weather Forecasts (ECMWF), focusing on the summer 2006 African Monsoon Multidisciplinary Analysis (AMMA) field campaign period. A mechanism for data quality control, observation error definition and variational bias correction has been developed so that the data can be safely treated within 4D-Var, like other observations that are currently assimilated in the operational system. While data density is limited due to the restriction to daylight and cloud-free conditions, a systematic impact on mean moisture analysis was found, with distinct regional and seasonal features. The impact can last 1--2 days into the forecast but has little effect on forecast accuracy in terms of both moisture and dynamics. This is mainly explained by the weak dynamic activity in the areas of largest data impact. Analysis and short-range forecast evaluation with radiosonde observations revealed a strong dependence on radiosonde type. Compared with Vaisala RS92 observations, the addition of MERIS total column water-vapour observations produced neutral to positive impact, while contradictory results were obtained when all radiosonde types were used in generating the statistics. This highlights the issue of radiosonde moisture biases and the importance of sonde humidity bias correction in numerical weather prediction (NWP). Copyright © 2009 Royal Meteorological Society [source]

Sediment sequences and paleosols in the Kyichu Valley, southern Tibet (China), indicating Late Quaternary environmental changes

ISLAND ARC, Issue 3 2009
Knut Kaiser
Abstract The Tibetan Plateau is highly sensitive to environmental changes and affects the settings of a far larger territory in Central Asia and beyond. Thus, knowledge on past environmental changes in that area is essential. Even though the Kyichu (Lhasa River) Valley and its tributaries is an easily accessible area, the Late Quaternary landscape evolution of southern Tibet is in general scarcely known. Therefore, 12 sedimentary sections in the middle and lower catchment were subjected to multidisciplinary analyses (sedimentology, paleopedology, AMS 14C and luminescence dating, and charcoal determination) aiming at results on regional paleoenvironmental changes. At the altitude studied (3600,4000 m above sealevel), no glacial relics could be detected, indicating that the valley positions have been unglaciated since the Last Interglacial. The lack of fluvial,lacustrine structures above the floodplain is due to the aggradational character of this tectonically (sub-)active valley, which caused an alluvial burying of older valley bottoms. During the Late Pleistocene the mouth area of the Kyichu was occupied by a lake which was part of a larger dam-lake in the superordinate Yarlung Zhangbo Valley. On the valley flanks, loesses were predominantly deposited before the Last Glacial Maximum (LGM), whereas eolian sands were predominantly deposited around and after the LGM. Paleosols of Last Interglacial, Last Glacial and Holocene ages regularly occur at terrestrial sites representing temperate to cool and humid to semiarid conditions during soil formation. Ages of colluvial sediments indicate that the widespread barren valley slopes were primarily formed by Late Pleistocene erosion followed by a secondary Holocene erosion phase. Charcoal spectra indicate a Late Holocene change from a forest environment to a pastoral environment with sparse grasses, herbs and dwarf shrubs. It is assumed that the Late Holocene environmental changes, such as loss of forests/woodlands and erosion, have at least been reinforced by humans, enhancing a regional climatic aridification and cooling trend. [source]

Using the ,protective environment' framework to analyse children's protection needs in Darfur

DISASTERS, Issue 4 2009
Alastair Ager
A major humanitarian concern during the continuing crisis in Darfur, Sudan, has been the protection of children, although there has been little in the way of comprehensive analysis to guide intervention. Founded on a situational analysis conducted between October 2005 and March 2006, this paper documents the significant threats to children's well-being directly linked to the political conflict. It demonstrates the role of non-conflict factors in exacerbating these dangers and in promoting additional protection violations, and it uses the ,protective environment' framework (UNICEF Sudan, 2006a) to identify systematic features of the current environment that put children at risk. This framework is shown to provide a coherent basis for assessment and planning, prompting broad, multidisciplinary analysis, concentrating on preventive and protective action, and fostering a systemic approach (rather than placing an undue focus on the discrete needs of ,vulnerable groups'). Constraints on its present utility in emergency settings are also noted. [source]

Characterization and provenance of the slabs of the Puigseslloses Megalith, Barcelona, Spain

GEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 2 2010
Enric Vicens
The Puigseslloses megalith tomb (Barcelona, Spain) is located on the summit of a hill in the Vic Plain where the sedimentary rocks that were used in its construction do not crop out. A sedimentological and petrological characterization of the monument's slabs and a multidisciplinary analysis of the outcropping materials in nearby areas has allowed the identification of three possible source areas associated with the Paleogene Banyoles Marls Formation and the Folgueroles Sandstone Formation and allows us to propose possible routes by which the slabs were transported from the catchment site to the place where the monument was built. In addition, the lithology and position of different slabs within the megalith denote the intention to separate the chamber from the corridor by using different types of slab. The position of the monument also reveals that tomb location was more of a priority than proximity to the slab sources. © 2010 Wiley Periodicals, Inc. [source]

Rhone River flood deposits in Lake Le Bourget: a proxy for Holocene environmental changes in the NW Alps, France

BOREAS, Issue 4 2005
Emmanuel Chapron
The Holocene evolution of Rhone River clastic sediment supply in Lake Le Bourget is documented by sub-bottom seismic profiling and multidisciplinary analysis of well-dated sediment cores. Six high-amplitude reflectors within the lacustrine drape can be correlated to periods of enhanced inter- and underflow deposition in sediment cores. Based on the synthesis of major environmental changes in the NW Alps and on the age-depth model covering the past 7500 years in Lake Le Bourget, periods of enhanced Rhone River flood events in the lake can be related to abrupt climate changes and/or to increasing land use since c. 2700 cal. yr BP. For example, significant land use under rather stable climate conditions during the Roman Empire may be responsible for large flood deposits in the northern part of Lake Le Bourget between AD 966 and 1093. However, during the Little Ice Age (LIA), well-documented major environmental changes in the catchment area essentially resulted from climate change and formed basin-wide major flood deposits in Lake Le Bourget. Up to five ,LIA-like' Holocene cold periods developing enhanced Rhone River flooding activity in Lake Le Bourget are documented at c. 7200, 5200, 2800, 1600 and 200 cal. yr BP. These abrupt climate changes were associated in the NW Alps with Mont Blanc glacier advances, enhanced glaciofluvial regimes and high lake levels. Correlations with European lake level fluctuations and winter precipitation regimes inferred from glacier fluctuations in western Norway suggest that these five Holocene cooling events at 45°N were associated with enhanced westerlies, possibly resulting from a persistent negative mode of the North Atlantic Oscillation. [source]