References of "Geophysical Research Abstracts"
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See detailPlanet TOPERS: Planets, Tracing the Transfer, Origin, Preservation, and Evolution of Their Reservoirs
Dehant, V.; Van Hoolst, T.; Breuer, D. et al

in Geophysical Research Abstracts (2013, April), 15

An overview is given of the Planet TOPERS project addressing habitability in our solar system.

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See detailSpatial distribution of erosion and deposition on an agricultural watershed
Pineux, Nathalie ULg; Colinet, Gilles ULg; Degré, Aurore ULg

in Geophysical Research Abstracts (2013), 15

To better understand the agricultural landscapes evolution becomes an essential preoccupation and, for this, it is needed to take into account the sediments deposition, in a distributed way. As it is not ... [more ▼]

To better understand the agricultural landscapes evolution becomes an essential preoccupation and, for this, it is needed to take into account the sediments deposition, in a distributed way. As it is not possible in practice to study all terrestrial surfaces in detail by instrumenting sectors to obtain data, models of prediction are valuable tools to control the current problems, to predict the future tendencies and to provide a scientific base to the political decisions. In our case, a landscape evolution model is needed, which aims at representing both erosion and sedimentation and dynamically adjusts the landscape to erosion and deposition by modifying the initial digital elevation model. The Landsoil model (Landscape design for Soil conservation under soil use and climate change), among others, could fulfil this objective. It has the advantage to take the soil variability into account. This model, designed for the analysis of agricultural landscape, is suitable for simulations from parcel to catchment scale, is spatially distributed and event-based. Observed quantitative data are essential (notably to calibrate the model) but still limited. Particularly, we lack observations spatially distributed on the watershed. For this purpose, we choose a watershed in Belgium (Wallonia) which is a 124 ha agricultural zone in the loamy region. Its slopes range from 0% to 9%. To test the predictions of the model, comparisons will be done with: - sediment measurements which are done with water samplings in four points on the site to compare the net erosion results; - sediment selective measurements (depth variation observed along graduated bares placed on site) to compare the erosion and deposition results; - very accurate DSM’s (6,76 cm pixel resolution X-Y) obtained by the drone (Gatewing X100) each winter. Besides planning what the landscape evolution should be, a revision of the soil map (drew in 1958) is organized to compare with the past situation and establish how the landscape moved in 50 years. The first results of the sediment measurements and of the pictures of the drone will be showed in the presentation. [less ▲]

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See detailHydrological and geopedological dynamics of a forested slope
Deraedt, Deborah ULg; Degré, Aurore ULg; Colinet, Gilles ULg

in Geophysical Research Abstracts (2013), 15

Though forested watersheds are really particular in terms of hydrodynamics, most of the hydrological models oversimplify the phenomena involved. More investigations are unavoidable to improve the ... [more ▼]

Though forested watersheds are really particular in terms of hydrodynamics, most of the hydrological models oversimplify the phenomena involved. More investigations are unavoidable to improve the knowledge and the modelling of this environment. Here is the aim of this study. The studied slope is located on the Houille watershed in the West of the Belgian Ardenne (50 1’47”N, 4 53’22”E) on a silty rocky soil. The site is situated under a Douglas fir (Pseudotsuga menziesii (MIRB.) FRANCO) and spruce stand cover (Picea abies (L.) Karst). It is about 160 meters long with a North-West facing slope between 7 and 55%. The goal of the study is : - to characterise the hydrological and pedogeological dynamics along a forested slope, - to compare these dynamics with the tree growth. For the geopedological part of the study, eight pits were dug to describe the soil and take some soil samples used for granulometric, chemical, etc. analysis. We have used geophysical methods (Electrical Resistivity Tomography and Ground Penetrating Radar) to estimate the soil depth. As for the hydrological part of this study, moisture sensors (capacitive and TDR) have been installed in the pits along the slope. A dye tracing test has been performed to underline the preferential flow and the importance of the subsurface flow. Several trees have been equipped with dendrometers and some measures of the LAI and the height of the trees are planned. [less ▲]

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See detailFirst retrievals of HCFC-142b from ground-based high resolution FTIR solar observations: application to high altitude Jungfraujoch spectra
Mahieu, Emmanuel ULg; O'Doherty, Simon; Reimann, Stefan et al

in Geophysical Research Abstracts (2013), 15

Hydrofluorocarbons (HCFCs) are the first substitutes to the long-lived ozone depleting halocarbons, in particular the chlorofluorocarbons (CFCs). Given the complete ban of the CFCs by the Montreal ... [more ▼]

Hydrofluorocarbons (HCFCs) are the first substitutes to the long-lived ozone depleting halocarbons, in particular the chlorofluorocarbons (CFCs). Given the complete ban of the CFCs by the Montreal Protocol, its Amendments and Adjustments, HCFCs are on the rise, with current rates of increase substantially larger than at the beginning of the 21st century. HCFC-142b (CH3CClF2) is presently the second most abundant HCFC, after HCFC-22 (CHClF2). It is used in a wide range of applications, including as a blowing foam agent, in refrigeration and air-conditioning. Its concentration will soon reach 25 ppt in the northern hemisphere, with mixing ratios increasing at about 1.1 ppt/yr [Montzka et al., 2011]. The HCFC-142b lifetime is estimated at 18 years. With a global warming potential of 2310 on a 100-yr horizon, this species is also a potent greenhouse gas [Forster et al., 2007]. First space-based retrievals of HCFC-142b have been reported by Dufour et al. [2005]. 17 occultations recorded in 2004 by the Canadian ACE-FTS instrument (Atmospheric Chemistry Experiment – Fourier Transform Spectrometer, onboard SCISAT-1) were analyzed, using two microwindows (1132.5–1135.5 and 1191.5–1195.5 cm-1). In 2009, Rinsland et al. determined the HCFC-142b trend near the tropopause, from the analysis of ACE-FTS observations recorded over the 2004–2008 time period. The spectral region used in this study extended from 903 to 905.5 cm-1. In this contribution, we will present the first HCFC-142b measurements from ground-based high-resolution Fourier Transform Infrared (FTIR) solar spectra. We use observations recorded at the high altitude station of the Jungfraujoch (46.5°N, 8°E, 3580 m asl), with a Bruker 120HR instrument, in the framework of the Network for the Detection of Atmospheric Composition Change (NDACC, visit http://www.ndacc.org). The retrieval of HCFC-142b is very challenging, with simulations indicating only weak absorptions, lower than 1% for low sun spectra and current concentrations. Among the four microwindows tested, the region extending from 900 to 906 cm-1 proved to be the most appropriate, with limited interferences, in particular from water vapor. A total column time series spanning the 2004-2012 time period will be presented, analyzed and critically discussed. After conversion of our total columns to concentrations, we will compare our results with in situ measurements performed in the northern hemisphere by the AGAGE network. [less ▲]

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See detailInitiation of methane turbulent flux measurements over a grazed grassland in Belgium
Dumortier, Pierre ULg; Aubinet, Marc ULg; Chopin, Henri ULg et al

in Geophysical Research Abstracts (2013), 15

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See detailEstimation of the fascine efficiency in terms of runoff infiltration and sediments deposition
Degré, Aurore ULg; Pineux, Nathalie ULg; Cantreul, Vincent ULg et al

in Geophysical Research Abstracts (2013), 15

Runoff inundations and mudflows are more and more frequent phenomena. In 2011, Belgium had a lot of its municipalities affected by this problematic. Since then, mitigation measures are more and more set ... [more ▼]

Runoff inundations and mudflows are more and more frequent phenomena. In 2011, Belgium had a lot of its municipalities affected by this problematic. Since then, mitigation measures are more and more set up in agricultural watersheds. The fascines are one of these measures which allow to protect the public and private infrastructures and in the same way, which don’t reduce the famers productivity. They consist in branches faggots piled up between two rows of stakes. These linear constructions are mainly put in place across concentrated runoff axis in order to slow down the water and to filter the mud. Only few quantifications of their effectiveness (in terms of flow and concentration water reduction) exist and are however needed to better recommend these types of mitigation measures. Our experiment aims at measuring discharge and mud concentration reduction due to the fascines in a completely defined context. The tests were realised through fascines planted in field border. A watertight surface of 2,45m to 0,80m carries the water to the fascines. Three types of fascines were tested (willow wood fascine, straw fascine, straw compacted fascine), three different water flows were applied (0,5L/s, 3L/s and 6L/s) and three water concentration in dry soil (13g/L, 26g/L, 38g/L) were used. The different factor combinations were tested. The results show that we can expect a reduction of 60% of the flow for the biggest water flows (proportional efficiency with the water flow). The factor interaction study doesn’t allow to see a difference between the type. About the sediment water concentration, the filtration can reach 50%, the fascine with wood faggots showing a better efficiency. Finally, the difference between the fascine type show that straw fascine can support a biggest watershed (25 hectares) than the wood faggot fascine can (5-10 hectares) but during a smaller return period (one year against five years). [less ▲]

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See detailHow adaptation strategies of crops could counteract climate change effects? The case of four catchments in Wallonia, Belgium.
Bauwens, Alexandra ULg; Sohier, Catherine ULg; Degré, Aurore ULg

in Geophysical Research Abstracts (2013), 15

A sharp increase in extreme heat and drought stress is projected in Belgium by the end of the 21st century, with the potential to significantly reduce crops’ yields under current agricultural practices ... [more ▼]

A sharp increase in extreme heat and drought stress is projected in Belgium by the end of the 21st century, with the potential to significantly reduce crops’ yields under current agricultural practices. This contribution uses an agro-hydrological model in order to assess the potential effects of climate evolution on crop development, yield, and water balance for the main agricultural productions in the Meuse catchment. Erosion risk is also evaluated. We show that grasslands and maize yield decrease and yield variability increases under climate change scenarios. The leaf area index study permits to put in emphasis the earlier start of the vegetation due to warmer climate. It appears that all the sensitive stages occur earlier in the season and that crops are negatively affected by summer drought stress. The better understanding of crops development under evolving climate allows us to propose some changes in agricultural practices and to assess their effectiveness. We evaluate different strategies of adaptation in agricultural practices in order to reduce the potential negative effects of climate change on grasslands and maize production. Adaptation strategies proposed are advanced sowing and harvesting date, introduction of a cover crop for maize and advance in the cutting dates for grasslands. In the particular case of the Vesdre catchment, shifting the growth period of maize permits to avoid the water-deficit period and allow increased yield. This shift makes it possible to introduce a cover crop that will drastically reduce winter soil erosion. For grassland, the adjustment of the cutting dates favored the first cut and the earlier start of the vegetation. The second cut is less profitable due to summer drought stress. The vulnerability assessments focused on the main rotation encountered in the cultivated areas and in the difference in the cover type of these crops. [less ▲]

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See detailIdentifying early Earth microfossils in unsilicified sediments
Javaux, Emmanuelle ULg; Asael, Dan; Bekker, Andrey et al

in Geophysical Research Abstracts (2013), 15

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See detailHumidity 3D field comparisons between GNSS tomography, IASI satellite observations and ALARO model
Brenot, Hugues; Champollion, Cedric; Deckmyn, Alex et al

in Geophysical Research Abstracts (2012, April), 14

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See detailRunoff inundation hazard cartography
Pineux, Nathalie ULg; Degré, Aurore ULg

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 ▲]

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See detailLong-term series of tropospheric water vapour amounts and HDO/H2O ratio profiles above Jungfraujoch
Lejeune, Bernard ULg; Mahieu, Emmanuel ULg; 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 ▲]

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See detailModelling of agricultural diffuse pollution and mitigation measures effectiveness inWallonia (Belgium)
Sohier, Catherine ULg; Deraedt, Deborah ULg; Degré, Aurore ULg

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 ▲]

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See detailHow could Mosan agriculture be impacted by climate change and future droughts?
Bauwens, Alexandra ULg; Sohier, Catherine ULg; Deraedt, Deborah ULg 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 ▲]

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See detailHydrological behavior of a forested catena
Deraedt, Deborah ULg; Ridremont, François ULg; Claessens, Hugues ULg 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 ▲]

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See detailMicro and macroscopic investigation to quantify tillage impact on soil hydrodynamic behaviour
Beckers, Eléonore ULg; Roisin, Chrsitian; Plougonven, Erwan ULg 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 ▲]

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See detailCO2 total column retrieval by mid-IR FT Spectroscopy
Buschmann, M; Dohe, S; Mahieu, Emmanuel ULg 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 ▲]

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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 ULg; 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 ▲]

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See detailEffect of raingage density, position and interpolation on rainfall-discharge modelling
Ly, Sarann ULg; Sohier, Catherine ULg; Charles, Catherine ULg 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 ▲]

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See detailSeeking for the optimum retrieval strategy of methanol (CH3OH) from ground-based high-resolution FTIR solar observations recorded at the high-altitude Jungfraujoch station (46.5ºN)
Mahieu, Emmanuel ULg; Bader, Whitney ULg; Lejeune, Bernard ULg et al

in Geophysical Research Abstracts (2012), 14

Methanol (CH3OH) is a key organic compound in the Earth’s troposphere, with reported concentrations of the order of a few ppbv. It is indeed the second most abundant organic atmospheric compound after ... [more ▼]

Methanol (CH3OH) is a key organic compound in the Earth’s troposphere, with reported concentrations of the order of a few ppbv. It is indeed the second most abundant organic atmospheric compound after methane (Jacob et al., 2005). The same authors have estimated its lifetime to a few days. Natural sources of CH3OH include plant growth, oceans, decomposition of plant matter, oxidation of methane,. . . They are complemented by anthropogenic (from vehicles, industry) and biomass burning emissions. Oxidation by the hydroxyl radical is the main sink, leading to the formation of carbon monoxide (CO) and formaldehyde (H2CO) (Rinsland et al., 2009; Stavrakou et al., 2011, and references therein). The first retrievals of methanol from ground-based Fourier Transform Infrared (FTIR) spectra have been reported by Rinsland et al. (2009), using spectra recorded at Kitt Peak (31.9ºN) and a microwindow extending from 992 to 999 cm-1. Soon after, Stavrakou et al. (2011) used another spectral interval from 1029 to 1037 cm-1, for methanol retrievals at Reunion Island (21ºS). In both cases, lines of the strong nu8 band of CH3OH were adjusted, accounting for interferences by several isotopologues of ozone and by water vapor. In this contribution, we will present first retrievals of CH3OH from observations recorded at the high-altitude station of the Jungfraujoch (46.5ºN, 8ºE, 3580 m asl), with a Bruker 120HR spectrometer, in the framework of the Network for the Detection of Atmospheric Composition Change (NDACC, visit http://www.ndacc.org). We will implement existing retrieval approaches –and possibly additional one(s)– to determine which strategy is the most appropriate for our dry high-altitude site. If successful, a long-term CH3OH total column time series will be produced using the Jungfraujoch observational database, and we will perform preliminary investigations to characterize the seasonal and inter-annual variations of this species at northern mid-latitudes. [less ▲]

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See detailSpurrite, tilleyite and associated minerals in the exoskarn zone from Cornet Hill (Metalliferi Massif, Apuseni Mountains, Romania).
Marincea, Stefan ULg; Dumitras, Delia; Calin, Nicolas et al

in Geophysical Research Abstracts (2012), 14

Detailed reference viewed: 32 (4 ULg)