References of "Geophysical Research Abstracts"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailRunoff inundation hazard cartography
Pineux, Nathalie ULiege; Degré, Aurore ULiege

in Geophysical Research Abstracts (2012), 14

Between 1998 and 2004, Europe suffered from more than hundred major inundations, responsible for some 700 deaths, for the moving of about half a million of people and the economic losses of at least 25 ... [more ▼]

Between 1998 and 2004, Europe suffered from more than hundred major inundations, responsible for some 700 deaths, for the moving of about half a million of people and the economic losses of at least 25 billions Euros covered by the insurance policies. Within this context, EU launched the 2007/60/CE directive. The inundations are natural phenomenon. They cannot be avoided. Nevertheless this directive permits to better evaluate the risks and to coordinate the management measures taken at member states level. In most countries, inundation maps only include rivers’ overflowing. In Wallonia, overland flows and mudflows also cause huge damages, and must be included in the flood hazard map. Indeed, the cleaning operations for a village can lead to an estimated cost of 11 000 C˙ Average construction cost of retention dams to control off-site damage caused by floods and muddy flows was valued at 380 000C and yearly dredging costs associated with these retention ponds at 15 000C˙ For a small city for which a study was done in a more specific way (Gembloux), the mean annual cost for the damages that can generate the runoff is about 20 000C˙ This cost consists of the physical damages caused to the real estate and movable properties of the residents as well as the emergency operations of the firemen and the city. On top of damages to public infrastructure (clogging of trenches, silting up of retention ponds) and to private property by muddy flows, runoff generates a significant loss of arable land. Yet, the soil resource is not an unlimited commodity. Moreover, sediments’ transfer to watercourses alters their physical and chemical quality. And that is not to mention the increased psychological stress for people. But to map overland flood and mud flow hazard is a real challenge. This poster will present the methodology used to in Wallonia. The methodology is based on 3 project rainfalls: 25, 50 and 100 years return period (consistency with the cartography of the overflowing hazard map), with a rain duration set at 1h. The arable lands are considered as bare, except for the permanent meadows. The worst situation is envisaged, the hydrologic effect of the soil cover in the farming area being variable from a year to another according to the vegetative development and to the cultural operations. The peak discharge is chosen as the more critic parameter because it synthesizes the watershed propensity to stream, its size, and its flow network. The cartographic representation is done in a linear way along the concentrated runoff axes. Whereas this first approach at regional scale includes uncertainties, the aim of this map is currently to prompt consideration of the runoff inundation hazard during the design of urban development projects. [less ▲]

Detailed reference viewed: 52 (18 ULiège)
Full Text
See detailRetrievals of ethane from ground-based high-resolution FTIR solar observations with updated line parameters: determination of the optimum strategy for the Jungfraujoch station.
Bader, Whitney ULiege; Perrin, Agnès; Jacquemart, David et al

in Geophysical Research Abstracts (2012), 14(EGU2012-9126),

Ethane (C2H6) is the most abundant Non-Methane HydroCarbon (NMHC) in the Earth’s atmosphere, with a lifetime of approximately 2 months. C2H6 has both anthropogenic and natural emission sources such as ... [more ▼]

Ethane (C2H6) is the most abundant Non-Methane HydroCarbon (NMHC) in the Earth’s atmosphere, with a lifetime of approximately 2 months. C2H6 has both anthropogenic and natural emission sources such as biomass burning, natural gas loss and biofuel consumption. Oxidation by the hydroxyl radical is by far the major C2H6 sink as the seasonally changing OH concentration controls the strong modulation of the ethane abundance throughout the year. Ethane lowers Cl atom concentrations in the lower stratosphere and is a major source of peroxyacetyl nitrate (PAN) and carbon monoxide (by reaction with OH). Involved in the formation of tropospheric ozone and in the destruction of atmospheric methane through changes in OH, C2H6 is a non-direct greenhouse gas with a net-global warming potential (100-yr horizon) of 5.5. The retrieval of ethane from ground-based infrared (IR) spectra is challenging. Indeed, the fitting of the ethane features is complicated by numerous interferences by strong water vapor, ozone and methane absorptions. Moreover, ethane has a complicated spectrum with many interacting vibrational modes and the current state of ethane parameters in HITRAN (e.g. : Rothman et al., 2009, see http://www.hitran.com) was rather unsatisfactory in the 3 µm region. In fact, PQ branches outside the 2973–3001 cm-1 range are not included in HITRAN, and most P and R structures are missing. New ethane absorption cross sections recorded at the Molecular Spectroscopy Facility of the Rutherford Appleton Laboratory (Harrison et al., 2010) are used in our retrievals. They were calibrated in intensity by using reference low-resolution spectra from the Pacific Northwest National Laboratory (PNNL) IR database. Pseudoline parameters fitted to these ethane spectra have been combined with HITRAN 2004 line parameters (including all the 2006 updates) for all other species encompassed in the selected microwindows. Also, the improvement brought by the update of the line positions and intensities of methyl chloride (CH3Cl) in the 3.4 m region (Bray et al., 2011) will be quantified. The ethane a priori volume mixing ratio (VMR) profile and associated covariance are based on synthetic data from the chemical transport model (CTM) of the University of Oslo. In this contribution, we will present updated ethane total and tropospheric column retrievals, using the SFIT-2 algorithm (v3.91) and high-resolution Fourier Transform Infrared (FTIR) solar absorption observations recorded with a Bruker 120HR instrument, at the high altitude research station of the Jungfraujoch (46.5°N, 8°E, 3580 m asl), within the framework of the Network for the Detection of Atmospheric Composition Change (NDACC, visit http://www.ndacc.org). We will characterize three microwindows encompassing the strongest ethane features after careful selection of a priori VMR profiles, spectroscopic parameters, accounting at best for all interfering species. We will then present the retrieval strategy representative of the best combination of those three characterized micro-windows in order to minimize the fitting residuals while maximizing the information content, the precision and the reliability of the retrieved product. The long-term C2H6 column time series will be produced using the Jungfraujoch observational database. Comparisons with synthetic data produced by two chemical transport model (CHASER and the one of the University of Oslo) will also be presented and analyzed, aiming at the determination and interpretation of long-term trends and interannual variations of ethane at Northern mid-latitudes. [less ▲]

Detailed reference viewed: 346 (31 ULiège)
Full Text
Peer Reviewed
See detailModelling of agricultural diffuse pollution and mitigation measures effectiveness inWallonia (Belgium)
Sohier, Catherine ULiege; Deraedt, Deborah ULiege; Degré, Aurore ULiege

in Geophysical Research Abstracts (2012), 14(EGU2012), 9672

Implementation of European directives in the environmental field and, specially, in the water management field, generates a request from policy-makers for news tools able to evaluate impact of management ... [more ▼]

Implementation of European directives in the environmental field and, specially, in the water management field, generates a request from policy-makers for news tools able to evaluate impact of management measures aiming at reducing pressures on ecosystems. In Wallonia (Southern Region of Belgium), the Nitrate Directive (EEC/676/91) was transposed into the “Walloon action plan for nitrogen sustainable management in agriculture” (PGDA1) in 2002. In 2007, a second plan was launched to reinforce some topics (PGDA2). Furthermore, the goal of “good quality” of surface waters and groundwater imposed by the Water Framework Directive poses new challenges in water management. In this context, a “soil and vadose” hydrological model is used in order to evaluate diffuse pollutions and efficiency of mitigation measures. This model, called EPICgrid, has been developed at catchment scale with an original modular concept on the basis of the field scale “water-soil-plant” EPIC model (Williams J.R., Jones C.A., Dyke P.T. (1984). A modelling approach to determining the relationship between erosion and soil productivity. Transactions of the ASAE. 27, 129-144). The model estimates, for each HRU identified into a 1km2 grid, water and nutrients flows into the plant-soil-vadose zone system (Sohier C., Degré A., Dautrebande S. (2009). From root zone modelling to regional forecasting of nitrate concentration in recharge flows – The case of the Walloon Region (Belgium). Journal of Hydrology, Volume 369, Issues 3-4, 15 May 2009, Pages 350-359). The model is used to make prospective simulations in order to evaluate the impact of measures currently performed to reduce the effect of diffuse pollution on water surface quality and groundwater quality, at regional scale. Response of the soil-vadose zone to agricultural practices modification is analyzed for the deadlines of the Water Framework Directive: 2015, 2021 and 2027, taking into account two climatic scenarios. Simulations results showed that actual measures are not sufficient in some areas and that new actions are necessary. The EPICgrid model was also used to evaluate effectiveness of further measures that could be implemented in order to reduce agricultural diffuse pollution. The increasing of catch crops in vulnerable zones has shown a limited impact in theWalloon context. The modifications of agricultural practices such as crop rotations or mineral fertilizing amounts have shown a more significant impact on water quality. Furthermore, the farmers’ practices are evaluated each year by a measuring campaign of the soil nitrogen residue after harvest. These data allow us to improve the representativeness of the EPICgrid model in areas in which agricultural practices largely differs from regional statistics. [less ▲]

Detailed reference viewed: 61 (14 ULiège)
Full Text
See detailEffect of raingage density, position and interpolation on rainfall-discharge modelling
Ly, Sarann ULiege; Sohier, Catherine ULiege; Charles, Catherine ULiege et al

in Geophysical Research Abstracts (2012), 14(EGU2012), 2592

Precipitation traditionally observed using raingages or weather stations, is one of the main parameters that has direct impact on runoff production. This pPrecipitation data requires a preliminary spatial ... [more ▼]

Precipitation traditionally observed using raingages or weather stations, is one of the main parameters that has direct impact on runoff production. This pPrecipitation data requires a preliminary spatial interpolation prior to hydrological modeling. The accuracy of modelling result is determined bydepends on the accuracy of the interpolated spatial rainfall which differs according to different interpolation methods. The accuracy of the interpolated spatial rainfall is usually determined by cross-validation method. The objective of this study is to assess the different interpolation methods of daily rainfall at the watershed scale through hydrological modelling and to explore the best methods that provides a good long term simulation. Four versions of geostatistics: Ordinary Kriging (ORK), Universal Kriging (UNK), Kriging with External Dridft (KED) and Ordinary Cokriging (OCK) and two types of deterministic methods: Thiessen polygon (THI) and Inverse Distance Weighting (IDW) are used to produce 30-year daily rainfall inputs for a distributed physically-based hydrological model (EPIC-GRID). This work is conducted in the Ourthe and Ambleve nested catchments, located in the Ardennes hilly landscape in the Walloon region, Belgium. The total catchment area is 2908 km², lies between 67 and 693 m in elevation. The multivariate geostatistics (KED and OCK) are also used by incorporating elevation as external data to improve the rainfall prediction. This work also aims at analysing the effect of different raingage densities and position used for interpolation, on the stream flow modelled to get insight in terms of the capability and limitation of the geostatistical methods. The number of raingage varies from 70, 60, 50, 40, 30, 20, 8 to 4 stations located in and surrounding the catchment area. In the latter case, we try to use different positions: around the catchment and only a part of the catchment. The result shows that the simple method like THI fails to capture the rainfall and to produce good flow simulation when using 4 raingages. The KED and UNK are comparable to other methods for a raingage case that in which stations are located around the catchment area, especially in the high elevation catchment but the worst methods for other raingage position cases where the rainfall stations are located only at a part and mostly outside of the catchment area. However, three methods (IDW, ORK and OCK) can overcome this problem since they are more robust and can provide good performance of simulation in all raingage densities. When using 70, 60, 50, 40, 30, 20, 8 raingages in the catchment area (2908 km²), no substantial differences in model performance are observed. [less ▲]

Detailed reference viewed: 105 (16 ULiège)
Full Text
See detailCO2 total column retrieval by mid-IR FT Spectroscopy
Buschmann, M; Dohe, S; Mahieu, Emmanuel ULiege et al

in Geophysical Research Abstracts (2012), 14

Over the last decade ground-based remote sensing measurements of CO2 have been established as an important component in the global observing system for greenhouse gases. Since 2004 the Total Carbon Column ... [more ▼]

Over the last decade ground-based remote sensing measurements of CO2 have been established as an important component in the global observing system for greenhouse gases. Since 2004 the Total Carbon Column Observing Network (TCCON) sites have provided CO2 retrievals in the near-IR region. CO2 can also be retrieved in the mid-IR spectral region and it would be of great benefit to use these spectra to produce CO2-data of sufficient precision. With this, 20 years of additional observations obtained in the mid-IR at a suite of FT-IR sites of the Network Detection of Atmospheric Composition Change (NDACC) will be accessible. We investigated a series of different CO2 microwindows in the mid-IR spectral region and present results from the most promising candidates for a showcase FT-IR site (Ny Alesund). Limitations of the approach are outlined and the feasibility of a future Mid-IR CO2-product of sufficient precision is discussed. [less ▲]

Detailed reference viewed: 45 (5 ULiège)
Full Text
Peer Reviewed
See detailMicro and macroscopic investigation to quantify tillage impact on soil hydrodynamic behaviour
Beckers, Eléonore ULiege; Roisin, Chrsitian; Plougonven, Erwan ULiege et al

in Geophysical Research Abstracts (2012), 14

Nowadays, tillage simplification is an increasing practice. Many advantages are cited in the literature, such as energy saving, soil conservation etc. Agricultural management practices influence soil ... [more ▼]

Nowadays, tillage simplification is an increasing practice. Many advantages are cited in the literature, such as energy saving, soil conservation etc. Agricultural management practices influence soil structure, but consequent changes in soil hydrodynamic behaviour at the field scale are still not well understood. Many studies focus only on macroscopic measurements which do not provide mechanistic explanations. Moreover, research shows divergent conclusions over structure modification. The aim of this work is to fill this gap by quantifying soil structure modification depending on tillage intensity through both macroscopic and microscopic measurements, the latter improving our comprehension of the fundamental mechanisms involved. [less ▲]

Detailed reference viewed: 70 (33 ULiège)
Full Text
See detailLong-term series of tropospheric water vapour amounts and HDO/H2O ratio profiles above Jungfraujoch
Lejeune, Bernard ULiege; Mahieu, Emmanuel ULiege; Schneider, Matthias et al

in Geophysical Research Abstracts (2012), 14

Water vapour is a crucial climate variable involved in many processes which widely determine the energy budget of our planet. In particular, water vapour is the dominant greenhouse gas in the Earth’s ... [more ▼]

Water vapour is a crucial climate variable involved in many processes which widely determine the energy budget of our planet. In particular, water vapour is the dominant greenhouse gas in the Earth’s atmosphere and its radiative forcing is maximum in the middle and upper troposphere. Because of the extremely high variability of water vapour concentration in time and space, it is challenging for the available relevant measurement techniques to provide a consistent data set useful for trend analyses and climate studies. Schneider et al. (2006a) showed that ground-based Fourier Transform Infrared (FTIR) spectroscopy, performed from mountain observatories, allows for the detection of H2O variabilities up to the tropopause. Furthermore, the FTIR measurements allow the retrieval of HDO amounts and therefore the monitoring of HDO/H2O ratio profiles whose variations act as markers for the source and history of the atmospheric water vapour. In the framework of the MUSICA European project (Multi-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water, http://www.imk-asf.kit.edu/english/musica.php), a new approach has been developed and optimized by M. Schneider and F. Hase, using the PROFFIT algorithm, to consistently retrieve tropospheric water vapour profiles from high-resolution ground-based infrared solar spectra and so taking benefit from available long-term data sets of ground-based observations. The retrieval of the water isotopologues is performed on a logarithmic scale from 14 micro-windows located in the 2600-3100 cm-1 region. Other important features of this new retrieval strategy are: a speed dependant Voigt line shape model, a joint temperature profile retrieval and an interspecies constraint for the HDO/H2O profiles. In this contribution, we will combine the quality of the MUSICA strategy and of our observations, which are recorded on a regular basis with FTIR spectrometers, under clear-sky conditions, at the NDACC site (Network for the Detection of Atmospheric Composition Change, http://www.ndacc.org) of the Jungfraujoch International Scientific Station (Swiss Alps, 46.5°N, 8.0°E, 3580m asl). Information content analysis of the retrieved H2O products allows us to produce a long-term trend from 1996 to 2011 for different tropospheric levels. We will compare the annual cycle of tropospheric HDO/H2O ratio profiles with those already produced at other sites (Schneider et al., 2010). We will also focus on the diurnal variability of water vapour to determine a time limit in the inter-comparison of different water vapour measurement techniques. [less ▲]

Detailed reference viewed: 217 (20 ULiège)
Full Text
Peer Reviewed
See detailHydrological behavior of a forested catena
Deraedt, Deborah ULiege; Ridremont, François ULiege; Claessens, Hugues ULiege et al

in Geophysical Research Abstracts (2012), 14

At the time when the significance of water becomes more than obvious, we realize the utility of models that describe hydrological phenomena and that permit the optimization of water management. The soil ... [more ▼]

At the time when the significance of water becomes more than obvious, we realize the utility of models that describe hydrological phenomena and that permit the optimization of water management. The soil properties, as they have an influence both on hydrology and on plant development, are an element really essential in this type of model. But, as for tree characteristics, these properties are spatially and temporally variable. Therefore this research will specially focus on the case of forested slopes. The study will be divided into three parts. The first will characterize the vertical and the horizontal heterogeneity of the structural and hydrodynamic properties of soil. To do this, in addition to the analysis of the soil sampled along the slope, moisture sensors will be installed on different places on a slope and on different depths. For the greatest part it will be capacitive sensors whose values will be confirmed by TDR sensors. Each sensor will be inserted to cover the largest pedological and topographic variability. The second part of the study will permit to characterize the water flux repartition into the horizons down the slope. We will therefore apply a dye to surface on the top of the slope. The bottom of the slope will be equipped with an experimental system which collects water for each soil layer. The third parts will deal with the forest stand heterogeneity along the slope. We will measure characteristics such as tree height, roots repartition, stem circumference and also for different periods of the year, leaf area index (LAI). At the end of the research, we will measure tree rings for a dendrochronolocical study. The collected data will be analyzed to determine the slope effects on the soil properties, on the water flux distribution into the soil layer and on the tree characteristics. Afterwards the relations and the interactions can be conceptualized and introduced into a physical hydrological model. The studied slope is located on the Houille watershed in the West of the Belgian Ardenne. The site is situated under a Douglas fir cover (Pseudotsuga menziesii (MIRB.) FRANCO). It is about 170 meters long with an average slope of 25%. There are only few studies that attempt to connect physical models and the tree growth at the slope scale, leaving a vast untapped investigation area in the hydrological modelling. The study of this variability would afford possibility to improve hydrological models. From the point of view of the climate change, such a model would e.g. determine the best adapted species to each forest site. [less ▲]

Detailed reference viewed: 56 (28 ULiège)
Full Text
Peer Reviewed
See detailHow could Mosan agriculture be impacted by climate change and future droughts?
Bauwens, Alexandra ULiege; Sohier, Catherine ULiege; Deraedt, Deborah ULiege et al

in Geophysical Research Abstracts (2012), 14

Despite the great uncertainties regarding the future climatic context, lots of studies have focused on hydrological effects of climate change on the Meuse catchment. It appears that both winter high flows ... [more ▼]

Despite the great uncertainties regarding the future climatic context, lots of studies have focused on hydrological effects of climate change on the Meuse catchment. It appears that both winter high flows and summer low flows could be exacerbated. Climate change and its impacts on hydrology will thus affect various socio-economic sectors. High flows have been widely studied compared to low-flows. This poster will put the emphasis on a methodology developed in order to study impacts of droughts on agriculture. Agriculture is among the most impacted sectors due to climate change. The consequences could be both positive as negative in accordance with the range of predicted changes and the adaptation capacity of agricultural systems. Most of the existing studies related to climate change on agriculture focused on specific territory. Within the AMICE Interreg IVB project, a transnational approach has been developed to assess droughts impacts on agriculture through the Meuse basin. The project’s previous works gave us a common scenario of climate trends and of the evolution of the hydrology in the Meuse basin. The methodology is based on the use of a physically-based model able to simulate the water-soil-plant continuum (derived from EPIC model). In order to be transferable from one country to another, the methodology proposed used data available at the basin scale. The UE soil data base was complemented with local information on agricultural practices and statistics. Three crops have been studied: maize, wheat and barley. The basic cultural calendar is supposed to be the same for the different countries. The methodology developed permits to study the evolution of yields, leaf area index, crops stress due to excess or lack of water through time under different scenarios build up in the frame of the project. It appears that corn is negatively affected by climate change, and thus despite the CO2 fertilization effect. Wheat and barley have similar behavior and are positively affected by climate change and CO2 fertilization. Leaf Area Index study reveals that the different crops start earlier and reach earlier maturity. These first results will be completed with other economic sectors’analysis like drinkable water production, electricity production and navigation. Therefore, the project will progress towards a better understanding of economic effects of future droughts and low-flows. [less ▲]

Detailed reference viewed: 51 (18 ULiège)
Full Text
See detailO2/Ar and CH4 measurements in sea ice : clues for the key status of sea ice in the climate system
Zhou, Jiayun; Tison, Jean-Louis; Eicken, Hajo et al

in Geophysical Research Abstracts (2011, April 08), 13

Detailed reference viewed: 29 (7 ULiège)
Full Text
See detailCarbon balance of crops: overview of 7 years of investigation
Moureaux, Christine ULiege; Dufranne, Delphine ULiege; Suleau, Marie ULiege et al

in Geophysical Research Abstracts (2011, April 08), 13

Detailed reference viewed: 47 (13 ULiège)
Full Text
See detailManagement effects on net ecosystem carbon and GHG budgets at European crop sites
Ceschia, Eric; Béziat, Pierre; Dejoux, Jean-François et al

in Geophysical Research Abstracts (2011, April 08), 13

Detailed reference viewed: 112 (11 ULiège)
Full Text
See detailMeasurement and modeling of methanol deposition/emission in a mixed forest
Laffineur, Quentin ULiege; Heinesch, Bernard ULiege; Amelynck, Crist et al

in Geophysical Research Abstracts (2011, April 07), 13

Detailed reference viewed: 44 (6 ULiège)
Full Text
Peer Reviewed
See detailMultilayer Analysis of Soil Respiration and its Isotopic Signature in Forest Ecosystem
Goffin, Stéphanie ULiege; Longdoz, Bernard ULiege; Maier, Martin et al

in Geophysical Research Abstracts (2011, April 06), 13

Detailed reference viewed: 57 (25 ULiège)
Full Text
See detailOn the impact of ionospheric variability and disturbances on GNSS-based positioning applications
Stankov, Stanimir; Wautelet, Gilles ULiege; Lejeune, Sandrine et al

in Geophysical Research Abstracts (2011, April), 13(ABS. No EGU2011-12067),

Detailed reference viewed: 38 (5 ULiège)
Full Text
Peer Reviewed
See detailHuman presence at Belle-Roche, in the Ardenne massif (western Europe) : Terrestrial Cosmogenic Nuclides (10Be) dating of fluvial sediments confirms an age of ∼580 ka
Rixhon, Gilles; Braucher, Régis; Bourlès, Didier et al

in Geophysical Research Abstracts (2011), 13

Detailed reference viewed: 15 (1 ULiège)
Full Text
Peer Reviewed
See detailEffects of different spatial interpolators on the estimate of extreme precipitations
Ly, Sarann ULiege; Beckers, Eléonore ULiege; Charles, Catherine ULiege et al

in Geophysical Research Abstracts (2011), 13

The design values of the areal precipitation are needed for engineer to manage vital elements of our infrastructure. The areal precipitation can be generated by different interpolation methods. The ... [more ▼]

The design values of the areal precipitation are needed for engineer to manage vital elements of our infrastructure. The areal precipitation can be generated by different interpolation methods. The problem involves choosing the interpolation method that we should use to estimate the extreme event. This work aimed at analyzing the effects of different interpolation methods on the estimate of extreme events of daily areal precipitations at catchment scale. The extreme rainfalls were estimated using areal daily rainfall interpolated by several interpolation methods (Thiessen polygon, Inverse Distance Weighting, Ordinary Kriging, Universal Kriging, Kriging with an External Drift and Ordinary Cokriging). We used thirty-years-long daily time series and different density of rain gages (from 4 to 70 rain gages). Our study is located in the Ourthe and Ambleve catchment area (2908 km²) in the southern part of Belgium). Spatial interpolation with the geostatistical and Inverse Distance Weighting algorithms outperformed considerably interpolation with the Thiessen polygon. Kriging with an External Drift and Ordinary Cokriging presented the highest Root Mean Square Error between the geostatistical and Inverse Distance Weighting methods. Ordinary Kriging and Inverse Distance Weighting were considered to be the best methods, as they provided smallest Root Mean Square Error for nearly all cases. However, it’s not really the case of extreme estimates for particular return period. The extreme daily rainfall, corresponding to return periods of 25, 50 and 100 years, were computed by fitting of a statistical model to the series of maximum annual precipitation. These estimates were conducted using HYFRAN which allows us to fit 16 different statistical models, in 2 or 3 parameters. The most known are the models of Gumbel, Gamma, Weibull, exponential, Pareto, lognormale, Pearson III and GEV. Our results showed that the behaviour of extreme daily areal rainfall in this area was best described via the Gumbel and lognormal distributions. Using 70 rain gages, little differences in extreme rainfall were observed between the interpolation methods. The estimates from these methods were in the area of 95% confidence intervals of the estimates using the Thiessen polygon. However, when the number of rain gages diminishes, the Universal Kriging and Kriging with External drift methods produced extreme estimates outside the area of 95% confidence intervals of the estimates using the Thiessen polygon with all available stations. The analysis described here provides a means to choose the interpolation method in view to calculate extreme events. It shows to engineers or hydrologists the need for a particular care when working in the regions of sparse data. [less ▲]

Detailed reference viewed: 160 (39 ULiège)
Full Text
See detailNMHC Climatology from Central European Mountain Observatories
Plass-Duelmer, C.; Reimann, S.; Wallasch, M. et al

in Geophysical Research Abstracts (2011), 13

NMHC (non-methane hydrocarbons) are a major group of atmospheric trace gases with impact on photochemical processes in the atmosphere, especially oxidant formation with ozone being the most prominent of ... [more ▼]

NMHC (non-methane hydrocarbons) are a major group of atmospheric trace gases with impact on photochemical processes in the atmosphere, especially oxidant formation with ozone being the most prominent of them, and contributions to SOA (secondary organic aerosols). By this, they are coupled to climate issues via the oxidizing capacity of the atmosphere, the greenhouse gas ozone and aerosol effects. NMHC monitoring was initiated in Europe in the “Tropospheric Ozone Research” project (1988-1995), and it was continued in EMEP and GAW (Global Atmosphere Watch) where it is an ongoing initiative which recently has been reinforced (GAW Report 171). In this presentation we will focus on time series from Central European mountain stations (46-49°N, 7-13°E): Hohenpeissenberg (985 m, DWD, Germany, 1998-ongoing), Rigi (1031 m, EMPA, Switzerland, 2003-ongoing), Junfraujoch (3580 m, EMPA, Switzerland, 2000-ongoing, and ULg (FTIR), Belgium, 1984-ongoing), Zugpitze (2650 m, UBA, Germany, 2000-ongoing), Schauinsland (1205 m, FZ-Jülich (1989-94), and UBA, Germany, 2004-ongoing), Brotjacklriegel (1016 m, UBA, Germany, 2000-2004), Donon (775 m, EMD, France, 1997-2007). Most sites used weekly flask samples but also on-line measurements were carried out with higher time resolution within the former TOR project and in the more recent time series at Hohenpeissenberg, Rigi, and Jungfraujoch. All samples were analysed by GC. Additionally to these GC measurements, a time series of column integrated acetylene and ethane by FTIR (Fourier Transform InfraRed spectrometry) is available from Jungfraujoch, from 1984 onwards. We focus here on time series of monthly averages of anthropogenic hydrocarbons over the 1997-2009 time period. They show quite similar patterns among the various stations over the whole period with pronounced seasonal cycles. Significantly lower mixing ratios were measured at the highest elevated sites, the Zugspitze and Jungfraujoch. Differences between the lower mountain sites (775-1200 m) are on first view surprisingly small. Generally, the differences between the high altitude and the other mountain sites are lowest in summer due to enhanced vertical mixing and thermal upslope winds. Downward trends for anthropogenic hydrocarbons are very similar at the various stations and are 2 %/yr for C2-C3 alkanes (+/- 1%), 3-6 %/yr for C4-C7 alkanes (+/- 2%), 2-3%/yr for C2-C3 alkynes and ethene (+/- 2%), 4 % /yr for propene and benzene (+/- 2%), and 5-10%/yr for toluene and xylenes (+/-3 and 5%, respectively). [less ▲]

Detailed reference viewed: 134 (10 ULiège)