References of "Müller, J.-F"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailLong-term evolution and seasonal modulation above Jungfraujoch (46.5°N, 8.0°E): Optimisation of the retrieval strategy, comparison with model and independant observations
Bader, Whitney ULg; Stavrakou, T; Muller, J-F et al

in Atmospheric Measurement Techniques. Papers in Open Discussion (2014), 7

Methanol (CH3OH) is the second most abundant organic compound in the Earth's atmosphere after methane. In this work, we present the first long-term time series of methanol total, lower tropospheric and ... [more ▼]

Methanol (CH3OH) is the second most abundant organic compound in the Earth's atmosphere after methane. In this work, we present the first long-term time series of methanol total, lower tropospheric and upper tropospheric-lower stratospheric partial columns derived from the analysis of high resolution Fourier transform infrared solar spectra recorded at the Jungfraujoch station (46.5° N, 3580 m a.s.l.). The retrieval of methanol is very challenging due to strong absorptions of ozone in the region of the selected υ8 band of CH3OH. Two wide spectral intervals have been defined and adjusted in order to maximize the information content. Methanol does not exhibit a significant trend over the 1995–2012 time period, but a strong seasonal modulation characterized by maximum values and variability in June–July, minimum columns in winter and a peak-to-peak amplitude of 130%. In situ measurements performed at the Jungfraujoch and ACE-FTS occultations give similar results for the methanol seasonal variation. The total and lower tropospheric columns are also compared with IMAGESv2 model simulations. There is no systematic bias between the observations and IMAGESv2 but the model underestimates the peak-to-peak amplitude of the seasonal modulations. [less ▲]

Detailed reference viewed: 6 (3 ULg)
Full Text
See detailLong-term evolution and seasonal modulation above Jungfraujoch (46.5°N, 8.0°E): Optimisation of the retrieval strategy, comparison with model and independant observations
Bader, Whitney ULg; Stavrakou, J; Muller, J-F et al

Poster (2014, May)

Methanol (CH3OH) is the second most abundant organic compound in the Earth’s atmosphere after methane. In this work, we present the first long-term time series of methanol total, lower tropospheric and ... [more ▼]

Methanol (CH3OH) is the second most abundant organic compound in the Earth’s atmosphere after methane. In this work, we present the first long-term time series of methanol total, lower tropospheric and upper tropospheric-lower stratospheric partial columns derived from the analysis of high resolution Fourier transform infrared solar spectra recorded at the Jungfraujoch station (46.5°N, 3580 m a.s.l.). The retrieval of methanol is very challenging due to strong absorptions of ozone in the region of the selected 8 band of CH3OH. Two wide spectral intervals have been defined and adjusted in order to maximize the information content. Methanol does not exhibit a significant trend over the 1995-2012 time period, but a strong seasonal modulation characterized by maximum values and variability in June-July, minimum columns in winter and a peak-to-peak amplitude of 130 %. In situ measurements performed at the Jungfraujoch and ACE-FTS occultations give similar results for the methanol seasonal variation. The total and lower tropospheric columns are also compared with IMAGESv2 model simulations. There is no systematic bias between the observations and IMAGESv2 but the model underestimates the peak-to-peak amplitude of the seasonal modulations. [less ▲]

Detailed reference viewed: 7 (2 ULg)
Full Text
Peer Reviewed
See detailAbiotic and biotic control of methanol exchanges in a temperate mixed forest
Laffineur, Quentin ULg; Aubinet, Marc ULg; Schoon, N. et al

in Atmospheric Chemistry and Physics (2012), 12

Methanol exchanges over a mixed temperate forest in the Belgian Ardennes were measured for more than one vegetation season using disjunct eddy-covariance by a mass scanning technique and Proton Transfer ... [more ▼]

Methanol exchanges over a mixed temperate forest in the Belgian Ardennes were measured for more than one vegetation season using disjunct eddy-covariance by a mass scanning technique and Proton Transfer Reaction Mass Spectrometry (PTR-MS). Half-hourly methanol fluxes were measured in the range of −0.6 μgm−2 s−1 to 0.6 μgm−2 s−1, and net daily methanol fluxes were generally negative in summer and autumn and positive in spring. On average, the negative fluxes dominated (i.e. the site behaved as a net sink), in contrast to what had been found in previous studies. An original model describing the adsorption/desorption of methanol in water films present in the forest ecosystem and the methanol degradation process was developed. Its calibration, based on field measurements, predicted a mean methanol degradation rate of −0.0074 μgm−2 s−1 and a half lifetime for methanol in water films of 57.4 h. Biogenic emissions dominated the exchange only in spring, with a standard emission factor of 0.76 μgm−2 s−1. The great ability of the model to reproduce the long-term evolution, as well as the diurnal variation of the fluxes, suggests that the adsorption/desorption and degradation processes play an important role in the global methanol budget. This result underlines the need to conduct long-term measurements in order to accurately capture these processes and to better estimate methanol fluxes at the ecosystem scale. [less ▲]

Detailed reference viewed: 32 (10 ULg)
Full Text
Peer Reviewed
See detailClear link between drought stress, photosynthesis and biogenic volatile organic compounds in Fagus sylvatica L.
Šimpraga, M.; Verbeeck, H.; Demarcke, M. et al

in Atmospheric Environment (2011), 45(30), 5254-5259

Direct plant stress sensing is the key for a quantitative understanding of drought stress effects on biogenic volatile organic compound (BVOC) emissions. A given level of drought stress might have a ... [more ▼]

Direct plant stress sensing is the key for a quantitative understanding of drought stress effects on biogenic volatile organic compound (BVOC) emissions. A given level of drought stress might have a fundamentally different effect on the BVOC emissions of different plants. For the first time, we continuously quantified the level of drought stress in a young potted beech (Fagus sylvatica L.) with a linear variable displacement transducer (LVDT) installed at stem level in combination with simultaneous measurements of BVOC emissions and photosynthesis rates at leaf level. This continuous set of measurements allowed us to examine how beech alters its pattern of photosynthesis and carbon allocation to BVOC emissions (mainly monoterpenes, MTs) and radial stem growth during the development of drought stress. We observed an increasing-decreasing trend in the MT emissions as well as in the fraction of assimilated carbon re-emitted back into the atmosphere (ranging between 0.14 and 0.01%). We were able to link these dynamics to pronounced changes in radial stem growth, which served as a direct plant stress indicator. Interestingly, we detected a sudden burst in emission of a non-identified, non-MT BVOC species when drought stress was acute (i.e. pronounced negative stem growth). This burst might have been caused by a certain stress-related green leaf volatile, which disappeared immediately upon re-watering and thus the alleviation of drought stress. These results highlight that direct plant stress sensing creates opportunities to understand the overall complexity of stress-related BVOC emissions. [less ▲]

Detailed reference viewed: 19 (2 ULg)
Full Text
Peer Reviewed
See detailComparing monoterpenoid emissions and net photosynthesis of beech (Fagus sylvatica L.) in controlled and natural conditions
Šimpraga; Verbeeck, H.; Demarcke, M. et al

in Atmospheric Environment (2011), 45(17), 2922-2928

Although biogenic volatile organic compounds (BVOCs) only represent a very limited fraction of the plant's carbon (C) budget, they play an important role in atmospheric chemistry for example as a ... [more ▼]

Although biogenic volatile organic compounds (BVOCs) only represent a very limited fraction of the plant's carbon (C) budget, they play an important role in atmospheric chemistry for example as a precursor of tropospheric ozone. We performed a study comparing BVOC emissions of European beech (Fagus sylvatica L.) in controlled and natural environmental conditions. A young and adult beech tree was exposed to short-term temperature variations in growth room conditions and in an experimental forest, respectively. This study attempts to clarify how short-term temperature variations between days influenced the ratio between monoterpenoid (MT) emissions and net photosynthesis (Pn). Within a temperature range of 17-27 °C and 13-23 °C, the MT/Pn carbon ratio increased 10-30 fold for the growth room and forest, respectively. An exponential increasing trend between MT/Pn C ratio and air temperature was observed in both conditions. Beech trees re-emitted a low fraction of the assimilated C back into the atmosphere as MT: 0.01-0.12% and 0.01-0.30% with a temperature rise from 17 to 27 °C and 13-23 °C in growth room and forest conditions, respectively. However, the data showed that the MT/Pn C ratio of young and adult beech trees responded significantly to changes in temperature. [less ▲]

Detailed reference viewed: 11 (2 ULg)
Full Text
See detailEffect of seasonality and short-term light and temperature history on monoterpene emissions from European beech (Fagus sylvatica L.)
Demarcke, M.; Amelynck, Crist; Schoon, N. et al

in Hansel, Armin; Dunkl, Jürgen (Eds.) 5th International PTR-MS Conference on Proton Transfer Reaction Mass Spectrometry and its Applications (2011, January)

Branch enclosure measurements of monoterpene emision rates have been performed at different positions in the canopy of a European beech tree in natural environmental conditions. Strong and position ... [more ▼]

Branch enclosure measurements of monoterpene emision rates have been performed at different positions in the canopy of a European beech tree in natural environmental conditions. Strong and position-dependent standard emission rate variations were observed in the course of the growth season. By using the obtained dataset and a modified vesrion of the MEGAN algorithm, the response of the emissions to short-term light and temperature history was investigated [less ▲]

Detailed reference viewed: 31 (0 ULg)
Full Text
See detailWhat can we learn from year-round BVOC disjunct eddycovariance measurements? A case example from a temperate forest
Laffineur, Quentin ULg; Heinesch, Bernard ULg; Schoon, N. et al

in Hansel, Armin; Dunkl, Jürgen (Eds.) 5th International PTR-MS Conference on Proton Transfer Reaction Mass Spectrometry and its Applications (2011, January)

Long term ecosystem-scale biogenic volatile organic compounds (BVOC) flux measurements by disjunct eddy-covariance are needed to determine and characterize the BVOC emissions/depositions from episodic ... [more ▼]

Long term ecosystem-scale biogenic volatile organic compounds (BVOC) flux measurements by disjunct eddy-covariance are needed to determine and characterize the BVOC emissions/depositions from episodic events (budburst, stress) as well as the continuous emission/deposition during vegetation growth and its seasonal evolution in interaction with climate and environment. If the data coverage is sufficient, this technique has the potential to provide a dataset covering the whole spectrum of meteorological and phenological conditions encountered by the studied ecosystem ending in a statistically more robust dataset than what can be provided by other BVOC measurement techniques. In addition, long term measurements allow in Oxygenated VOCs (OVOCs) depositions to be estimated in a realistic manner with is not the case with the enclosure technique. Here we present a year-round campaign of disjunct eddy-covariance BVOC fluxes above a mixed temperate forest performed in the frame of the IMPECVOC (Impact of Phenology and Environmental Conditions on BVOC Emissions from Forest Ecosystems) project. We will analyse the three main BVOC species (isoprene/monoterpenes and methanol) in order to illustrate the interest of long-term flux measurements by investigating the main driving variables and the underlying mechanisms of emission/deposition, how de novo carbon allocation to the isoprene/monoterpenes skeleton structure is altered through the time. For methanol, we will show the importance of deposition on a long-term basis and use an empirical model to discriminate the physical and physiological components of the exchange. [less ▲]

Detailed reference viewed: 36 (4 ULg)
Full Text
Peer Reviewed
See detailFirst space-based derivation of the global atmospheric methanol emission fluxes
Stavrakou, T.; Guenther, A.; Razavi, A. et al

in Atmospheric Chemistry and Physics (2011), 11

Detailed reference viewed: 13 (4 ULg)
Full Text
Peer Reviewed
See detailIsoprene and monoterpene emissions from a mixed temperate forest
Laffineur, Quentin ULg; Aubinet, Marc ULg; Schoon, N. et al

in Atmospheric Environment (2011), 45

Detailed reference viewed: 23 (2 ULg)