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See detailImpact of ancient charcoal kilns on chemical properties of several forest soils after 2 centuries
Dufey, Joseph; Hardy, Brieuc; Cornelis, Jean-Thomas ULiege

in Geophysical Research Abstracts (2014)

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See detailRecent increases in Stratospheric HCl: Stratospheric Dynamics versus the Montreal Protocol
Chipperfield, M.P.; Mahieu, Emmanuel ULiege; Notholt, J. et al

in Geophysical Research Abstracts (2014), 16

Long-lived chlorine-containing source gases, such as chlorofluorocarbons (CFCs), are transported into the stratosphere where they decompose and cause ozone depletion. Increases in chlorine during the ... [more ▼]

Long-lived chlorine-containing source gases, such as chlorofluorocarbons (CFCs), are transported into the stratosphere where they decompose and cause ozone depletion. Increases in chlorine during the 1970s-1990s resulted in long-term ozone decreases, especially in the polar regions. Following the implementation of the Montreal Protocol, the near-surface chlorine loading was observed to peak in 1993 and, since then, to decrease in line with expectations. After release from source gases in the stratosphere, chlorine mainly forms the reservoir HCl, providing an alternative method for monitoring the progress of the Montreal Protocol. A maximum in stratospheric HCl was observed around 1996, followed by decay at a rate close to 1%/year, consistent with the tropospheric chlorine peak and known transport timescales. However, we will present total column observations from ground-based FTIR instruments which show an unexpected and significant upturn in stratospheric HCl around 2007 in the northern hemisphere. Height-resolved observations from satellite instruments (HALOE, MLS, ACE) confirm this increase and show that it occurs in the lower stratosphere. These observations contrast with the ongoing monotonic decrease of near-surface chlorine source gases. Using 3-D model simulations (TOMCAT/SLIMCAT and KASIMA) we attribute this trend anomaly to a slowdown in the NH atmospheric circulation, causing air in the lower stratosphere to become more aged with a larger relative conversion of source gases to HCl. An important conclusion is that the Montreal Protocol is still on track and will still lead to long-term decreases in stratospheric chlorine. This dynamical variability could also significantly affect the evolution of stratospheric ozone and must be accounted for when searching for signs of ozone recovery. [less ▲]

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See detailMicropaleontology and chemostratigraphy of the Neoproterozoic Mbuji-Mayi Supergroup, Democratic Republic of Congo.
Kabamba Baludikay, Blaise ULiege; Bekker, Andrey; Baudet, Daniel et al

in Geophysical Research Abstracts (2014), 16(EGU2014),

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See detailDEM time series of an agricultural watershed
Pineux, Nathalie ULiege; Lisein, Jonathan ULiege; Swerts, Gilles ULiege et al

in Geophysical Research Abstracts (2014), 16

the field data come from plot scale studies, the watershed scale seems to be more appropriate to understand them. Currently, small unmanned aircraft systems and images treatments are improving. In this ... [more ▼]

the field data come from plot scale studies, the watershed scale seems to be more appropriate to understand them. Currently, small unmanned aircraft systems and images treatments are improving. In this way, 3D models are built from multiple covering shots. When techniques for large areas would be to expensive for a watershed level study or techniques for small areas would be too time consumer, the unmanned aerial system seems to be a promising solution to quantify the erosion and deposition patterns. The increasing technical improvements in this growth field allow us to obtain a really good quality of data and a very high spatial resolution with a high Z accuracy. In the center of Belgium, we equipped an agricultural watershed of 124 ha. For three years (2011-2013), we have been monitoring weather (including rainfall erosivity using a spectropluviograph), discharge at three different locations, sediment in runoff water, and watershed microtopography through unmanned airborne imagery (Gatewing X100). We also collected all available historical data to try to capture the “long-term” changes in watershed morphology during the last decades: old topography maps, soil historical descriptions, etc. An erosion model (LANDSOIL) is also used to assess the evolution of the relief. Short-term evolution of the surface are now observed through flights done at 200m height. The pictures are taken with a side overlap equal to 80%. To precisely georeference the DEM produced, ground control points are placed on the study site and surveyed using a Leica GPS1200 (accuracy of 1cm for x and y coordinates and 1.5cm for the z coordinate). Flights are done each year in December to have an as bare as possible ground surface. Specific treatments are developed to counteract vegetation effect because it is know as key sources of error in the DEM produced by small unmanned aircraft systems. The poster will present the older and more recent changes of relief in this intensely exploited watershed and notably show how unmanned airborne imagery might be of help in DEM dynamic modelling to support soil conservation research. [less ▲]

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See detailWhich measurement strategies to improve spatial erosion and deposition patterns modelling?
Pineux, Nathalie ULiege; Maugnard, Alexandre; Swerts, Gilles ULiege et al

in Geophysical Research Abstracts (2014), 16

Validation of the erosion models requires field data. To date, many authors continue to highlight the paucity of accurate field observations and long-term enough studies. The fields observations are often ... [more ▼]

Validation of the erosion models requires field data. To date, many authors continue to highlight the paucity of accurate field observations and long-term enough studies. The fields observations are often put aside because these measures are difficult to obtain: weighty experimental devices, climatic dependence, . . . Hence the models are evolving and propose refined calculation procedures including for instance the calculation of landscape evolution. The need of field data therefore increases and new measuring strategies should arise. In the centre of Belgium we choose an agricultural watershed quite representative of the local context. It covers 124 ha of loamy soil with more than 90% of arable land and a weak proportion of forest and artificial lands. The slope ranges between 0 and 9%. Instrumentation on the watershed includes meteorological observations and discharge measurement coupled with water sampling at different outlets. The weather data (radiation, temperature, wind velocity, relative humidity and rainfall) and discharge measurement (comparison between Doppler and pressure sensors) will allow us to model the hydrological behaviour of the catchment. Rainfall readings (tipping buckets) are completed with erosivity readings (disdrometer). Erosivity, together with soil data, land use and agricultural practices observations on field, will be used as entry in the Landsoil model. The sediment samplings at 3 points in the catchment will give an insight of the sediment delivery of 3 subcatchments. The Landsoil model calculates the evolution of the DTM through time. This cannot be compared to measurements at the outlet and requires further data collection. Older elevation data and/or archaeological data are a possible source of information even if their precision remains scarce in our context. 1950’s soil surveys are on the contrary really informative since they detail the horizons depth in a spatial way and can be compared to new observation across the watershed. Coupled with unmanned aerial system, they should allow us to test the model performances and improve our knowledge of the spatial patterns of erosion and deposition. [less ▲]

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See detailComparison of continuous background in-situ and column integrated CO2 observations at Jungfraujoch with an urban site in the city of Bern
Schibig, Michael; Leuenberger, Markus; Nyfeler, Peter et al

in Geophysical Research Abstracts (2014), 16

A six and a half year (January 2005 to May 2011) comparison of CO2 concentration observations has been performed at Jungfraujoch, Switzerland and the city of Bern using two different measurement ... [more ▼]

A six and a half year (January 2005 to May 2011) comparison of CO2 concentration observations has been performed at Jungfraujoch, Switzerland and the city of Bern using two different measurement techniques run by the University of Bern (UBE) and the University of Liege (UL). The UBE systems at Jungfraujoch and Bern are both combined systems for atmospheric oxygen and CO2 measurements. The cryogenically dried air is analysed for CO2 with a Maihak analyser based on the broad-band infrared absorption technique. The measurement frequency is every second but the final reported data are averages of six minute periods. UL is measuring the solar infrared spectrum since 1950 at Jungfraujoch. On its way through the atmosphere, the solar spectrum is modulated depending on the abundant gas species and their amount in the column. Since some gases like CO2 absorb the solar infrared radiation at particular wavelengths and the extinction is proportional to the gas concentration, it is possible to determine the gas concentration in the column above the sensor. At the conference, we will present the three observational records for the six and a half year period. The results show for all three records a distinct, but different seasonality. The seasonalities of the UL and UBE record at Jungfraujoch are lower than the seasonality in the city of Bern, i.e. 4.5 ppm per year and 9 ppm per year for the column and the in- situ record respectively, whereas the seasonality in the city of Bern is 31 ppm per year. Also the maxima and minima of the Jungfraujoch measurements are delayed by several weeks compared to the measurements in the city of Bern. The annual increase of the CO2 concentration of the UBE and UL records of Jungfraujoch are in good agreement with 1.94 ppm per year and 1.90 ppm per year, respectively. The annual increase of the CO2 concentration at the urban site is a bit higher at 2.01 ppm per year. [less ▲]

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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 detailThe interdependent relationship between C dynamics and soil-forming processes in a podzollic chronosequence under a temperate rainforest.
Vermeire, Marie-Liesse; Lavkulich, Les; Cornelis, Jean-Thomas ULiege

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 ULiege; Pineux, Nathalie ULiege; Cantreul, Vincent ULiege 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 detailInitiation of methane turbulent flux measurements over a grazed grassland in Belgium
Dumortier, Pierre ULiege; Aubinet, Marc ULiege; Chopin, Henri ULiege et al

in Geophysical Research Abstracts (2013), 15

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

in Geophysical Research Abstracts (2013), 15

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

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

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 detailFirst retrievals of HCFC-142b from ground-based high resolution FTIR solar observations: application to high altitude Jungfraujoch spectra
Mahieu, Emmanuel ULiege; 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 detailHydrological and geopedological dynamics of a forested slope
Deraedt, Deborah ULiege; Degré, Aurore ULiege; Colinet, Gilles ULiege

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 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 detailRole of land use change in landslide-related sediment fluxes in tropical mountain regions
Guns, Marie; Vanacker, Veerle; Demoulin, Alain ULiege

in Geophysical Research Abstracts (2012), 14

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See detailSpace-time dynamics of soil respiration link to the C pool distribution at the hillslope scale
Wiaux, François; Cornelis, Jean-Thomas ULiege; Van Oost, Kristof et al

in Geophysical Research Abstracts (2012), 14(EGU2012), 7937

Abstract : A crucial issue in soil C dynamics modelling is to develop models suitable for regional scale, but based on local and short-time scale observations. Recent research has illustrated the strong ... [more ▼]

Abstract : A crucial issue in soil C dynamics modelling is to develop models suitable for regional scale, but based on local and short-time scale observations. Recent research has illustrated the strong linkage between SOC dynamics and landscape processes. There is increasing evidence that lateral fluxes of SOC, sediment and water will further enhance the variability of SOC dynamics, especially on agricultural land. Hence, in this study, we aim to improve our understanding of soil C dynamics by quantifying the soil respiration response of carbon pools at different positions along a slope catena, characterized by different soil moisture and temperature conditions and by different SOC stock and C pool distributions. The study was performed on a hillslope in the belgian loamy belt. Time series of soil moisture, temperature and surface CO2 fluxes were monitored on a regular basis (at least once a week, during spring and autumn 2011) along the hillsope, at the soil surface. At the same positions, soil cores (1 to 1.5 m depth) were collected and analyzed for SOC, C distribution (using a chemical fractionation), mineral oxides (oxalate extractions), pH, and texture. Our results show that substantial lateral transport of soil materials takes place along this hillslope, with a continuous burying of surface C and minerals at the bottom of the slope. This results in the development of a colluvial soil with an increasing SOC stock. This colluvial C stock mainly consists of labile C (66%), and this labile C stock in the colluvium is 3.5 higher than the labile C stock at the other slope positions. This stock is thus poorly stabilized and has a higher potential for mineralization. The other part of this C stock is stabilized by organo-mineral associations (19%) or is recalcitrant C (15%). Compared to the other slope positions, this colluvial stable C stock is significant, as it is 1.5 to 2 times higher. The spatial gradient of the measured soil respiration is consistent with the previous C pool distribution observations along the hillslope, since there is a significant higher respiration at the bottom of the slope (colluvial area) than at the other slope positions. The measured temporal dynamics of the soil respiration is explained by moisture and temperature variations. This measured space-time dynamics, completed with further additional field measurement campaigns, will be the basis for calibrating and validating hillslope scale soil C turn-over models. [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 ULiege; Dumitras, Delia; Calin, Nicolas et al

in Geophysical Research Abstracts (2012), 14

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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 ULiege; Bader, Whitney ULiege; Lejeune, Bernard ULiege 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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