References of "Geophysical Research Abstracts"
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See detailPotential of Shallow Lake Systems to Trace Environmental Changes Caused by Earthquakes
Avsar, Ulas; Boes, X; Hubert, Aurelia ULg et al

in Geophysical Research Abstracts (2007, April), 9

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See detailDevelopment of paleoseismic trench logging and dating techniques: a case study on the Central North Anatolian Fault
Fraser, Jeff; Pigati, J.S.; Hubert, Aurelia ULg et al

in Geophysical Research Abstracts (2007, April), 9

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See detailUnderstanding the irregularity of Seismic cycles: A Case study in Turkey-A Marie Curie Excellence Team Project
Hubert, Aurelia ULg; Boes, X; Fraser, J et al

in Geophysical Research Abstracts (2007, April), 9

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See detailControlling factors of gully erosion in the upper part of the Isser river watershed (Algiers, N. Algeria)
Daoudi, M.; Dewitte, Olivier ULg; Gérard, Paul et al

in Geophysical Research Abstracts (2007), 9

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See detailSynthesis of primary impacts of climate change in Belgium, as an onset to the development of an assessment tool for adaptation measures
Dewals, Benjamin ULg; De Sutter, Renaat; De Smet, Lieven et al

in Geophysical Research Abstracts (2007), 9(11217),

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See detailGround-based FTIR measurements at Ile de La Réunion: Observations, error analysis and comparisons with satellite data.
Senten, Cindy; De Mazière, Martine; Hermans, Christian et al

in Geophysical Research Abstracts (2007), 9

Ground-based Fourier-transform infrared (FTIR) spectroscopy is a powerful remote sensing technique to obtain information on the total column abundances and on the vertical distribution of various ... [more ▼]

Ground-based Fourier-transform infrared (FTIR) spectroscopy is a powerful remote sensing technique to obtain information on the total column abundances and on the vertical distribution of various constituents in the atmosphere. Many of these species are essential for the investigation of important atmospheric phenomena, such as the overall greenhouse effect or the stratospheric ozone decrease and recovery. In the frame of the Network for the Detection of Atmospheric Composition Change (NDACC), such observations have been made since many years at several measurement stations for the worldwide long-term monitoring of the atmospheric composition. In this work, we present the results from two short-term FTIR measurement campaigns in 2002 and 2004 at the Ile de La Réunion (21°S, 55°E), a complementary NDACC site in the subtropics, in the Indian Ocean. All spectra were recorded in solar absorption mode. The results discussed here concern the direct greenhouse gases methane (CH4), nitrous oxide (N2O) and ozone (O3), and the indirect greenhouse gases carbon monoxide (CO) and ethane (C2H6), as well as hydrogen cyanide (HCN) and stratospheric hydrogen chloride (HCl), hydrogen fluoride (HF) and nitric acid (HNO3). For the latter species (HCN, HCl, HF and HNO3), we show time series of total column amounts from the surface up to 60 km. For CO, CH4, N2O and O3, it is possible to derive additionally independent information on a few partial columns; these time series are discussed as well. A complete error budget of the retrieval products is given. Temporary mutually correlated enhancements of CO, C2H6and HCN have been observed. They have been traced back to biomass burning events in southern Africa and Madagascar using the FLEXPART model. Comparisons of our retrievals with correlative data from satellite experiments, such as ACE and MOPITT, and with available ozone soundings, show generally good agreements between the different data sets. [less ▲]

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See detailCarbon balance of two Belgian crops
Moureaux, Christine ULg; Debacq, Alain ULg; Vilret, Amélie et al

in Geophysical Research Abstracts (2006), 8(1),

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See detailAdvanced exploitation of ground-based Fourier transform infrared observations for tropospheric studies over Europe: achievements of the UFTIR project
De Mazière, Martine; Vigouroux, Corinne; Blumenstock, Thomas et al

in Geophysical Research Abstracts (2006), 8

Solar absorption measurements using Fourier transform infrared (FTIR) spectrometry carry information about the atmospheric abundances of many constituents, including information about their vertical ... [more ▼]

Solar absorption measurements using Fourier transform infrared (FTIR) spectrometry carry information about the atmospheric abundances of many constituents, including information about their vertical distributions in the troposphere and the stratosphere. Such observations have regularly been made since many years as a contribution to the NDSC (Network for the Detection of Stratospheric Change). They are the only ground-based remote sensing observations available nowadays that carry information about key atmospheric trace species in the free troposphere, among which the most important greenhouse gases. The European UFTIR project (Time series of Upper Free Troposphere observations from a European ground-based FTIR network, http://www.nilu.no/uftir) has focused on maximizing the information content of FTIR long-term monitoring data of some direct and indirect greenhouse gases (CH4, N2O, O3,HCFC-22, and CO and C2H6, respectively). The UFTIR network includes six NDSC stations in Western Europe, covering the polar to subtropical regions. At several stations of the network, the observations span more than a decade. Existing spectral time series have been reanalyzed according to a common optimized retrieval strategy, in order to derive distinct tropospheric and stratospheric abundances of the abovementioned target gases. A bootstrap resampling method has been implemented to evaluate trends of the tropospheric and total burdens of the target gases, including their uncertainties. In parallel, simulations of the target time series have been made with the Oslo CTM2 model: comparisons between the model results and the observations provide valuable information to improve the model, and in particular, to optimize emission estimates that are used as inputs to the model simulations, and to explain the observed trends. The final results of the project will be presented, and ways to proceed will be discussed. [less ▲]

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See detailCan sea ice-specific biogeochemical processes support significant air-ice CO2 fluxes?
Delille, Bruno ULg; Lannuzel, Delphine; Schoemann, Véronique et al

in Geophysical Research Abstracts (2006), 8

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See detailModelling the Ligurian Sea ecosystem by means of a 1D couled physical-biogeochemical model. Improvement of model results using sequential data assimilation
Raick, C.; Soetaert, K.; Grégoire, Marilaure ULg

in Geophysical Research Abstracts (2005), 7

A 1D coupled physical-biogeochemical model has been built to study the pelagic food web of the Ligurian Sea (NW Mediterranean Sea). The physical model is the turbulent closure model (version 1D) developed ... [more ▼]

A 1D coupled physical-biogeochemical model has been built to study the pelagic food web of the Ligurian Sea (NW Mediterranean Sea). The physical model is the turbulent closure model (version 1D) developed at the GHER (University of Liège, Belgium). The ecosystem model contains nineteen state variables describing the carbon and nitrogen cycles of the pelagic food web. Silicate is considered as a potential limiting nutrient of diatoms’ growth. The aggregation model described in Kriest and Evans (2000) is used to evaluate the sinking rate of particulate detritus. The model is forced at the air-sea interface by the METEO France meteorological data. The DYFAMED time series data of year 2000 are used to calibrate and validate the biological model (Raick et al., 2005). By combining the numerical model and the available observations, data assimilation techniques are useful to improve the state estimation of the ocean. A Singular Fixed Extended Kalman filter (Pham et al., 1998) has been implemented in this way. Twin experiments are first performed to choose the suitable experimental protocol, which is then applied to perform real data assimilation experiments using DYFAMED data (Raick et al., submitted). To be coupled in a 3D environment, the ecosystem model is too complex. Our ongoing work is to perform a simplification, by studying simplified structures in comparison with the original ecosystem model. The advantage of deriving a simplified model from the complex one, is that we would be able to identify the most important processes of the Ligurian Sea ecosystem. [less ▲]

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See detailCarbon budget of a sugar beet crop
Moureaux, Christine ULg; Vilret, Amélie; Delvoye, Sébastien et al

in Geophysical Research Abstracts (2005), 7(1),

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See detailEstimating CO2 flux of croplands for bottom-up carbon budgetting
Moureaux, Christine ULg; Aubinet, Marc ULg; Pattey, E. et al

in Geophysical Research Abstracts (2005), 7(1),

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See detailInefficiency of magma mixing and source heterogeneity in the genesis of granitoids: the example of the Farsund body (southern Norway)
Dupont, Alain; Vander Auwera, Jacqueline ULg; Paquette, Jean-Louis et al

in Geophysical Research Abstracts (2005), 7

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See detailInterannual variations of the carbon monoxide tropospheric burden between 30ºN and 90ºN in 1996-2003: ground-based and satellite measurements, estimate of biomass burning emissions
Yurganov, L. N.; Edwards, D. P.; Grechko, E. I. et al

in Geophysical Research Abstracts (2005), 7(EGU05-A-03850),

Carbon monoxide total column amounts in the atmosphere were measured in the High Northern Hemisphere (30º-90º N, HNH) between January 1996 and December 2003 using Fourier Transform Infrared high ... [more ▼]

Carbon monoxide total column amounts in the atmosphere were measured in the High Northern Hemisphere (30º-90º N, HNH) between January 1996 and December 2003 using Fourier Transform Infrared high resolution spectrometers installed at the NDSC (Network for Detection of Stratospheric Change) sites. A grating spectrometer of moderate resolution was employed for the same purpose at the Zvenigorod Research Station of the Institute of Atmospheric Physics near Moscow. CO mixing ratios were measured in the air samples obtained at the ground-level stations of the CMDL (Climate Modeling and Diagnostic Laboratory, NOAA) network. Total column CO amounts were measured from space by the Terra/MOPITT instrument between March, 2000, and December, 2003 (Edwards et al., 2004). Anomalies of monthly mean CO densities (related to a quiet period of 2000 - 2001) for different sites in the HNH were in agreement. This fact confirmed a good mixing of CO in the Northern Hemisphere on the montly basis that may be expected from a 1.5-2-month-long CO life-time. The data were integrated over the HNH reservoir (0-10 km in altitude and 30º-90º N in latitude) and the CO burden anomalies (in Tg) were analysed using a box model. Two CO sinks were taken into account: i) internal chemical removal in the reaction between CO and OH, and ii) transport of CO into the southertn part of the Northern hemisphere, where CO concentrations are usually lower. OH concentarations were taken from Spivakovsky et al. (2000). The air exchange through the 30º N boundary of the reservoir was estimated using the GEOS-CHEM model with a real meteorology of 1998 (Yurganov et al., 2004). The interannual variations of the sinks were neglected; a corresponding uncertainty in the retrieved source anomaly was estimated to be 20-30%. Since 1996 four years have been found to experience high CO emission of similar magnitude (1996, 1998, 2002, and 2003). During four years (1997, 1999, 2000, and 2001) the emissions were relatively low. Seasonal patterns of the emissions in active years were similar, maxima occured in July-August. However, in 2003 emissions in June-July were higher than in August. These semi-hemisphere averaged emission rates correlate with Siberian forest fire counts detected at night time by the ATSR radiometer of the ERS-2 satellite (R2 =0.51). The early peak of 2003 may be attributed to forest fires in Baikal region, Siberia. An inclusion of fire counts for other areas (Europe, North America) only worsen the correlation; this implies a decisive role of the Siberian fires for polluting the Northern Hemisphere troposphere (cf., Kasischke et al., 2005). It was estimated that the boreal forest fires during active years emit 30-60 Tg CO per month in July-August and 150-200 Tg annually. These emissions may be compared to industrial and transport pollution in the Northern Hemisphere estimated by Kasischke et al. (2005) as 290 Tg CO annually (i.e., 25 Tg monthly). [less ▲]

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See detailModern techniques for flood risk analysis: quasi-3D simulations in a GIS environment
Archambeau, Pierre ULg; Erpicum, Sébastien ULg; Dewals, Benjamin ULg et al

in Geophysical Research Abstracts (2005), 7(09348),

Human beings have continuously attempted to adapt their environment to their needs. However, many natural phenomena still remain challenging to control and the populations must undergo sometimes heavily ... [more ▼]

Human beings have continuously attempted to adapt their environment to their needs. However, many natural phenomena still remain challenging to control and the populations must undergo sometimes heavily damaging consequences. It is consequently essential to study these phenomena in order to assess their potential hazards. In particular, the scope of the present paper focus on floods. The intense floods met these last years showed the importance of this phenomenon as well as its many devastating effects. Thanks to recent important breakthroughs, both in the field of conceptual and numerical modelling of complex flows and in the calculation power of computers, it is henceforth possible to study the effects of potential floods on the basis of numerical simulations, with an accuracy never reached beforehand. The Laboratory of Applied Hydrodynamics and Hydraulic Constructions (HACH) of the University of Liege has always made this kind of study one of its core competencies, thanks to • the development of modern and powerful modelling tools (quasi-three dimensional software for flow simulation by finite volume), • the use of a broad range of data enabling a proper representation of the studied fields (topography, occupation of the ground...) • the systematic validation of simulation results. These tools are currently intensively used within the framework of a general study of the flood-prone zones of the Walloon area of Belgium, which corresponds to more than 800 km of rivers. [less ▲]

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See detailMagnetic fabrics in jotunite dykes from the Late-Proterozoic Rogaland anorthosite province (SW Norway)
Bolle, Olivier ULg; Besse, Michal; Diot, Hervé

in Geophysical Research Abstracts (2005), 7

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See detailInfluence of the Aral Sea negative water balance on its seasonal circulation and ventilation patterns : use of a 3D hydrodynamic model
Sirjacobs, Damien ULg; Grégoire, Marilaure ULg; Delhez, Eric ULg et al

in Geophysical Research Abstracts (2003, April), 5(09052), 2003509052

Within the context of the EU INCO-COPERNICUS program "Desertification in the Aral Sea Region: A study of the Natural and Anthropogenic Impacts" (Contract IAC2-CT-2000-10023), a large-scale 3D hydrodynamic ... [more ▼]

Within the context of the EU INCO-COPERNICUS program "Desertification in the Aral Sea Region: A study of the Natural and Anthropogenic Impacts" (Contract IAC2-CT-2000-10023), a large-scale 3D hydrodynamic model was adapted to address specifically the macroscale processes affecting the Aral Sea water circulation and ventilation. The particular goal of this research is to simulate the effect of lasting negative water balance on the 3D seasonal circulation, temperature, salinity and water-mixing fields of the Aral Sea. The original Aral Sea seasonal hydrodynamism is simulated with the average seasonal forcings corresponding to the period from 1956 to 1960. This first investigation concerns a period of relative stability of the water balance, before the beginning of the drying process. The consequences of the drying process on the hydrodynamic of the Sea will be studied by comparing this first results with the simulation representing the average situation for the years 1981 to 1985, a very low river flow period. For both simulation periods, the forcing considered are the seasonal fluctuations of wind fields, precipitation, evaporation, river discharge and salinity, cloud cover, air temperature and humidity. The meteorological forcings were adapted to the common optimum one-month temporal resolution of the available data sets. Monthly mean kinetic energy flux and surface tensions were calculated from daily ECMWF wind data. Monthly in situ precipitation, surface air temperature and humidity fields were interpolated from data obtained from the Russian Hydrological and Meteorological Institute. Monthly water discharge and average salinity of the river water were considered for both Amu Darya and Syr Darya river over each simulation periods. The water mass conservation routines allowed the simulation of a changing coastline by taking into account local drying and flooding events of particular grid points. Preliminary barotropic runs were realised (for the 1951-1960 situation, before drying up began) in order to get a first experience of the behaviour of the hydrodynamic model. These first runs provide results about the evolution of the following state variables: elevation of the sea surface, 3D fields of vertical and horizontal flows, 2D fields of average horizontal flows and finally the 3D fields of turbulent kinetic energy. The mean seasonal salinity and temperature fields (in-situ data gathered by the Russian Hydrological and Meteorological Institute) are available for the two simulated periods and will allow a first validation of the hydrodynamic model. Various satellites products were identified, collected and processed in the frame of this research project and will be used for the validation of the model outputs. Seasonal level changes measurements derived from water table change will serve for water balance validation and sea surface temperature for hydrodynamics validation. [less ▲]

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