References of "Müller, Jean-François"
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See detailRetrieval of HCHO from MAX-DOAS measurements at the high-altitude alpine station of Jungfraujoch (46.5°N, 8.0°E)
Hendrick, François; Fayt, Caroline; Franco, Bruno ULg et al

Conference (2014, April 30)

Formaldehyde (HCHO) plays an important intermediate role in the atmospheric photo-oxidation pathways. It is produced during the oxidation of methane and many non-methane volatile organic compounds (NMVOCs ... [more ▼]

Formaldehyde (HCHO) plays an important intermediate role in the atmospheric photo-oxidation pathways. It is produced during the oxidation of methane and many non-methane volatile organic compounds (NMVOCs) which participate to the formation of tropospheric ozone and secondary organic aerosols. HCHO is also directly released by biomass burning and fossil fuel combustion and to a lesser extent by vegetation. Measuring this species is therefore of major importance for air quality and climate change monitoring. In this presentation, HCHO near-surface concentrations and vertical column densities are retrieved from MAX-DOAS measurements performed at the high-altitude station of Jungfraujoch (3580m asl) in the Swiss Alps from July 2010 till December 2012. Although being most of the time located in the free troposphere, this station can be temporarily affected by pollution events originating from the valley, leading to a local increase of air pollutant concentrations. The capability of the MAX-DOAS technique to retrieve HCHO in such high-altitude location is investigated. The spatial representativeness and the impact of cloud cover on the measurements is also discussed. For verification purpose, our retrievals are compared to collocated FTIR observations, taking into account the difference in vertical resolution between both techniques. Simulations from the 3D-CTM IMAGES are also used to further assess the observed seasonal and diurnal cycles of HCHO surface concentration and vertical column. [less ▲]

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See detailImpact of diffuse light on isoprene and monoterpene emissions from a mixed temperate forest
Laffineur, Quentin ULg; Aubinet, Marc ULg; Schoon, Niels et al

in Atmospheric Environment (2013), 46(74), 385-392

This study investigated the impact of diffuse light on canopy scale emission of isoprene and monoterpenes measured continuously above a mixed temperate forest, using the disjunct eddy-covariance by mass ... [more ▼]

This study investigated the impact of diffuse light on canopy scale emission of isoprene and monoterpenes measured continuously above a mixed temperate forest, using the disjunct eddy-covariance by mass scanning technique with a proton transfer reaction-mass spectrometer (PTR-MS) instrument. To assess this impact, the relationship between emissions/radiation and emissions/gross primary production (GPP) under clear sky and cloudy conditions were analysed. Under cloudy conditions (high proportion of diffuse radiation), the isoprene and monoterpene fluxes were enhanced compared to clear sky conditions (low proportion of diffuse radiation) at equivalent temperature and above-canopy total radiation. The whole-canopy enzymatic activity of the metabolic isoprene production pathway, however, was suggested to be lower under cloudy conditions than under clear sky conditions at equivalent temperature. The mechanisms behind these observations are probably linked to the better penetration of diffuse radiation in the canopy. Shade leaves/needles receive more radiation in cloudy conditions than in clear sky conditions, thereby inducing the observed effects. [less ▲]

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See detailIsoprene and monoterpene emissions from a mixed temperate forest
Laffineur, Quentin ULg; Heinesch, Bernard ULg; Amelynck, Crist et al

Poster (2011, April 07)

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See detailMeasurement and modeling of methanol deposition/emission in a mixed forest
Laffineur, Quentin ULg; Heinesch, Bernard ULg; Amelynck, Crist et al

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

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See detailFINAL REPORT PHASE II "Impact of Phenology and Environmental Conditions on BVOC Emissions from Forest Ecosystems" "IMPECVOC"
Dewulf, Jo; Joó, Eva; Van Langenhove, Herman et al

Report (2011)

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See detailVOC emissions from a temperate mixed forest in Belgium measured by eddy-covariance
Laffineur, Quentin ULg; Heinesch, Bernard ULg; Aubinet, Marc ULg et al

Poster (2010, May)

Forest ecosystems are known to be important emitters of Biogenic Volatile Organic Compounds (BVOC). They play an important role in the atmospheric chemistry and may contribute to the formation of ozone ... [more ▼]

Forest ecosystems are known to be important emitters of Biogenic Volatile Organic Compounds (BVOC). They play an important role in the atmospheric chemistry and may contribute to the formation of ozone and aerosols with consequences on air quality and on climate. In order to better understand the effects of environmental parameters on the emissions, micrometeorological flux measurements were carried out above a mixed forest (Fagus sylvatica, Pseudotsuga menziesii, Abies alba, Picea abies) at the Vielsalm experimental site (Belgium) from July to November 2009. The flux measurements were obtained by the eddy-covariance technique using proton transfer reaction mass spectrometry. In our first measurement campaign, among other VOC compounds, isoprene (m/z 69) and monoterpenoid compounds (m/z 137) have been measured continuously with a data coverage of 75 and 58 % respectively, allowing robust statistical analysis. In our analysis, we focused on these two main emissions. A footprint analysis showed that Fagus sylvatica seems to be the main emitter of m/z 137 and Abies alba seems to be the main emitter of m/z 69. BVOCs fluxes present an exponential response to temperature. This response is more pronounced for m/z 69 while it shows the strongest seasonal evolution for m/z 137. A light dependence of m/z 69 and m/z 137 fluxes was observed but the relationship did not exhibit the same behaviour before (hyperbolic relation) and after midday (linear relation). This behaviour difference induced a hysteresis effect on the daily evolution of averaged fluxes. A robust local minimum was also observed just before midday for m/z 69 (less obvious for m/z 137) during July-August period. This minimum is not observed in the CO2 fluxes which are also measured in Vielsalm. The light dependence of BVOC emissions suggests that m/z 69 and m/z 137 emissions are directly linked to the photosynthetic cycle but the presence of the midday local minimum suggests that other processes influence the measured BVOC fluxes. As for the relation with air temperature, a seasonal evolution of flux-light dependence was far more evident for m/z 137 than for m/z 69. This seasonal variation could be explained by a phenological effect. As Fagus sylvatica is the main m/z 137 emitter, its flux is probably influenced by leaves ageing while m/z 69, as mainly emitted by Abies alba, is less influenced by needles ageing. A wind speed dependence of BVOCs fluxes was also observed, the flux increasing linearly with wind speed. This surprising result will be discussed. [less ▲]

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See detailANNUAL SCIENTIFIC REPORT PHASE II "Impact of Phenology and Environmental Conditions on BVOC Emissions from Forest Ecosystems" "IMPECVOC"
Dewulf, Jo; Joó, Eva; Steppe, Kathy et al

Report (2009)

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See detailFINAL REPORT PHASE I "Impact of Phenology and Environmental Conditions on BVOC Emissions from Forest Ecosystems” «IMPECVOC»
Steppe, Kathy; Šimpraga, Maja; Verbeeck, Hans et al

Report (2008)

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See detailComparisons between SCIAMACHY and ground-based FTIR data for total columns of CO, CH4, CO2 and N2O
Dils, Bart; De Mazière, Martine; Muller, Jean-François et al

in Atmospheric Chemistry and Physics (2006), 6

Total column amounts of CO, CH4, CO2 and N2O retrieved from SCIAMACHY nadir observations in its near-infrared channels have been compared to data from a ground-based quasi-global network of Fourier ... [more ▼]

Total column amounts of CO, CH4, CO2 and N2O retrieved from SCIAMACHY nadir observations in its near-infrared channels have been compared to data from a ground-based quasi-global network of Fourier-transform infrared ( FTIR) spectrometers. The SCIAMACHY data considered here have been produced by three different retrieval algorithms, WFM-DOAS (version 0.5 for CO and CH4 and version 0.4 for CO2 and N2O), IMAP- DOAS ( version 1.1 and 0.9 (for CO)) and IMLM (version 6.3) and cover the January to December 2003 time period. Comparisons have been made for individual data, as well as for monthly averages. To maximize the number of reliable coincidences that satisfy the temporal and spatial collocation criteria, the SCIAMACHY data have been compared with a temporal 3rd order polynomial interpolation of the ground-based data. Particular attention has been given to the question whether SCIAMACHY observes correctly the seasonal and latitudinal variability of the target species. The present results indicate that the individual SCIAMACHY data obtained with the actual versions of the algorithms have been significantly improved, but that the quality requirements, for estimating emissions on regional scales, are not yet met. Nevertheless, possible directions for further algorithm upgrades have been identified which should result in more reliable data products in a near future. [less ▲]

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