Overview of the geophysical data derived from long-term FTIR monitoring activities at the Jungfraujoch NDACC site (46.5ºN) and the PYGCHEM project

Poster (2013, May 07)

We present an overview of the geophysical data deduced from long-term monitoring activities conducted at the Jungfraujoch station by the University of Liège. Typical results and trend investigations are ... [more ▼]

We present an overview of the geophysical data deduced from long-term monitoring activities conducted at the Jungfraujoch station by the University of Liège. Typical results and trend investigations are presented for hydrogen chloride (HCl) and carbonyl sulfide (OCS). We further display and briefly describe time series for new target gases, namely methanol (CH3OH) and HCFC-142b. We also show some preliminary results for ammonia (NH3) and peroxyacetyl nitrate (PAN). Finally, we present the PyGChem project, a Python interface to the GEOS-Chem model currently under development at ULg. [less ▲]

Tumor microenvironment converts plasmacytoid dendritic cells into immunosuppressive/tolerogenic cells: insight into the molecular mechanisms

in Journal of Leukocyte Biology (2013), 93

Human pDCs represent a rare population of circulating cells characterized by a rapid and massive TLR-dependent secretion of type I IFN in response to pathogenic agents or danger signals. Through their ... [more ▼]

Human pDCs represent a rare population of circulating cells characterized by a rapid and massive TLR-dependent secretion of type I IFN in response to pathogenic agents or danger signals. Through their capacity to bring together innate and adaptive immunity and to secrete soluble factors controlling cancer development, these cells could represent important actors in antitumor immunity. However, accumulating evidence suggests that pDCs recruited to the tumor microenvironment often display a nonactivated state and are associated with the development and maintenance of immunosuppression. Here, we present an overview of neoplastic lesions associated with an infiltration of immunosuppressive/ tolerogenic pDC. Moreover, as the proper response of pDC against cancer depends on a critical balance between immune-activating and immune-suppressing mechanisms, we summarize current knowledge about the molecular pathways developed by tumors to prevent antitumoral pDC immune responses. A better understanding of the mechanisms regulating pDC function in tumors could aid in the development of new therapies. Indeed, effective cancer vaccines or therapies could combine immunoactivating strategies (i.e., TLR agonists) with elimination of immune-suppressing mechanisms, leading to pDC reprogramming and thus, allowing tumor rejection in a clinical setting. [less ▲]

Dendritic cells in Barrett's carcinogenesis: an inadequate environment for antitumor immunity?

Conference (2013)

Ground-based remote sensing of tropospheric water vapour isotopologues within the project MUSICA

in Atmospheric Measurement Techniques (2012), 5(2012), 3007-3027

Within the project MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water), long-term tropospheric water vapour isotopologue data records are provided for ... [more ▼]

Within the project MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water), long-term tropospheric water vapour isotopologue data records are provided for ten globally distributed ground-based mid-infrared remote sensing stations of the NDACC (Network for the Detection of Atmospheric Composition Change). We present a new method allowing for an extensive and straightforward characterisation of the complex nature of such isotopologue remote sensing datasets. We demonstrate that the MUSICA humidity profiles are representative for most of the troposphere with a vertical resolution ranging from about 2 km (in the lower troposphere) to 8 km (in the upper troposphere) and with an estimated precision of better than 10%. We find that the sensitivity with respect to the isotopologue composition is limited to the lower and middle troposphere, whereby we estimate a precision of about 30‰ for the ratio between the two isotopologues HD16O and H216O. The measurement noise, the applied atmospheric temperature profiles, the uncertainty in the spectral baseline, and the cross-dependence on humidity are the leading error sources. We introduce an a posteriori correction method of the cross-dependence on humidity, and we recommend applying it to isotopologue ratio remote sensing datasets in general. In addition, we present mid-infrared CO2 retrievals and use them for demonstrating the MUSICA network-wide data consistency. In order to indicate the potential of long-term isotopologue remote sensing data if provided with a well-documented quality, we present a climatology and compare it to simulations of an isotope incorporated AGCM (Atmospheric General Circulation Model). We identify differences in the multi-year mean and seasonal cycles that significantly exceed the estimated errors, thereby indicating deficits in the modeled atmospheric water cycle. [less ▲]

Analysis of stratospheric NO2 trends above Jungfraujoch using ground-based UV-visible, FTIR, and satellite nadir observations

in Atmospheric Chemistry and Physics (2012), 12

The trend in stratospheric NO2 column at the NDACC (Network for the Detection of Atmospheric Composition Change) station of Jungfraujoch (46.5°N, 8.0°E) is assessed using ground-based FTIR and zenith ... [more ▼]

The trend in stratospheric NO2 column at the NDACC (Network for the Detection of Atmospheric Composition Change) station of Jungfraujoch (46.5°N, 8.0°E) is assessed using ground-based FTIR and zenith-scattered visible sunlight SAOZ measurements over the period 1990 to 2009 as well as a composite satellite nadir data set constructed from ERS-2/GOME, ENVISAT/SCIAMACHY, and METOP-A/GOME-2 observations over the 1996–2009 period. To calculate the trends, a linear least squares regression model including explanatory variables for a linear trend, the mean annual cycle, the quasi-biennial oscillation (QBO), solar activity, and stratospheric aerosol loading is used. For the 1990–2009 period, statistically indistinguishable trends of -3.7±1.1%/decade and -3.6±0.9%/decade are derived for the SAOZ and FTIR NO2 column time series, respectively. SAOZ, FTIR, and satellite nadir data sets show a similar decrease over the 1996–2009 period, with trends of -2.4±1.1%/decade, -4.3±1.4%/decade, and -3.6±2.2%/decade, respectively. The fact that these declines are opposite in sign to the globally observed +2.5%/decade trend in N2O, suggests that factors other than N2O are driving the evolution of stratospheric NO2 at northern mid-latitudes. Possible causes of the decrease in stratospheric NO2 columns have been investigated. The most likely cause is a change in the NO2/NO partitioning in favor of NO, due to a possible stratospheric cooling and a decrease in stratospheric chlorine content, the latter being further confirmed by the negative trend in the ClONO2 column derived from FTIR observations at Jungfraujoch. Decreasing ClO concentrations slows the NO+ ClO -> NO2 + Cl reaction and a stratospheric cooling slows the NO+O3 -> NO2 +O2 reaction, leaving more NOx in the form of NO. The slightly positive trends in ozone estimated from ground- and satellitebased data sets are also consistent with the decrease of NO2 through the NO2 +O3 -> NO3 +O2 reaction. Finally, we cannot rule out the possibility that a strengthening of the Dobson-Brewer circulation, which reduces the time available for N2O photolysis in the stratosphere, could also contribute to the observed decline in stratospheric NO2 above Jungfraujoch. [less ▲]

First steps of a new methodology for integrating ground-based ozone profile data

Poster (2012, August)

A new methodology is developed for integrating complementary ground-based data sources to provide consistent ozone vertical distribution time series as well as tropospheric and stratospheric ozone partial ... [more ▼]

A new methodology is developed for integrating complementary ground-based data sources to provide consistent ozone vertical distribution time series as well as tropospheric and stratospheric ozone partial columns. Primary results are presented for the Alpine station of the Network for the Detection of Atmospheric Composition Changes (NDACC). Ozone measurements from the lidar at Haute-Provence Observatory, the microwave spectrometer at Bern and the FTIR spectrometer at the Jungfrauch station are used for this purpose. First step is to evaluate the validity domain of ozone profile data considered here by assessing instrumental error and vertical resolution. Each instrument has its own vertical resolution; therefore adjustments need to be done for the creation of an homogeneous data set. Indeed, because of the higher resolution of lidar measurements, smoothing of the data is necessary for the comparison with FTIR and microwave measurements. However, smoothing the data induces a loss of scientific information. Therefore a compromise has to be established and discussed. The various intercomparisons provide an evaluation of the differences due to instrumental error and atmospheric variability. The statistical method used for combining the different measurements in order to obtain ozone vertical profile time series consistent with total ozone measurements is then discussed. [less ▲]

Retrievals of ethane from groundbased highresolution FTIR solar observations with updated line parameters: determination of the optimum strategy for the Jungfraujoch station.

Scientific conference (2012, June 01)

Ethane (C2H6) is the most abundant Non-Methane HydroCarbon (NMHC) in the Earth’s atmosphere, with a lifetime of approximately 2 months. Its main sources are biomass burning, natural gas loss and biofuel ... [more ▼]

Ethane (C2H6) is the most abundant Non-Methane HydroCarbon (NMHC) in the Earth’s atmosphere, with a lifetime of approximately 2 months. Its main sources are biomass burning, natural gas loss and biofuel consumption. Oxidation by the hydroxyl radical is the major C2H6 sink as it controls its strong modulation throug the year. C2H6 is involved in the formation of tropospheric O3 and in the destruction of atmospheric methane through changes in OH. C2H6 is an indirect greenhouse gas with a net-global warming potential of 5.5 (100-yr horizon). Updates of retrieval parameters such as the spectroscopic linelists have been recently published. We will therefore characterize three µ-windows encompassing the strongest C2H6 features after careful selection of these new parameters, accounting at best for all interfering species. The aim is to lessen the fitting residuals while maximizing the information content, the precision and the reliability of the retrieved product. We will present updated C2H6 total and tropospheric column time series, using the SFIT-2 algorithm (v3.91) and high-resolution Fourier Transform Infrared (FTIR) solar absorption spectra recorded with a Bruker 120HR instrument, at the high altitude research station of the Jungfraujoch (46.5°N, 8.0°E, 3580 m asl), within the framework of the Network for the Detection of Atmospheric Composition Change (NDACC, http://www.ndacc.org). Comparisons with synthetic data produced by chemical transport models will also be presented. [less ▲]

Retrieval of methanol (CH3OH) above the high-altitude Jungfraujoch station (46.5ºN): preliminary total column time series, long-term trend and seasonal modulation

Poster (2012, June)

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. Its lifetime is estimated 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). The first reported retrievals of methanol used a microwindow extending from 992 to 999 cm-1 or from 1029 to 1037 cm-1. In both cases, lines of the strong ν8 band of CH3OH were adjusted, accounting for interferences by several isotopologues of ozone and by water vapor. In this contribution, we present first retrievals of CH3OH from observations recorded at the high-altitude station of the Jungfraujoch (46.5°N, 8°E, 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). A strategy maximizing the information content and combining the 992-999 and 1029-1037 cm-1 domains has been set up and used. A preliminary long-term CH3OH total column time series derived from the Jungfraujoch observational database allows us to investigate the seasonal variation and long-term trend of this species at northern mid-latitudes. [less ▲]

Observed and simulated time evolution of HCl, ClONO2, and HF total column abundances

in Atmospheric Chemistry and Physics (2012), 12(7), 3527--3556

Time series of total column abundances of hydrogen chloride (HCl), chlorine nitrate (ClONO2), and hydrogen fluoride (HF) were determined from ground-based Fourier transform infrared (FTIR) spectra ... [more ▼]

Time series of total column abundances of hydrogen chloride (HCl), chlorine nitrate (ClONO2), and hydrogen fluoride (HF) were determined from ground-based Fourier transform infrared (FTIR) spectra recorded at 17 sites belonging to the Network for the Detection of Atmospheric Composition Change (NDACC) and located between 80.05°N and 77.82°S. By providing such a near-global overview on ground-based measurements of the two major stratospheric chlorine reservoir species, HCl and ClONO2, the present study is able to confirm the decrease of the atmospheric inorganic chlorine abundance during the last few years. This decrease is expected following the 1987 Montreal Protocol and its amendments and adjustments, where restrictions and a subsequent phase-out of the prominent anthropogenic chlorine source gases (solvents, chlorofluorocarbons) were agreed upon to enable a stabilisation and recovery of the stratospheric ozone layer. The atmospheric fluorine content is expected to be influenced by the Montreal Protocol, too, because most of the banned anthropogenic gases also represent important fluorine sources. But many of the substitutes to the banned gases also contain fluorine so that the HF total column abundance is expected to have continued to increase during the last few years. The measurements are compared with calculations from five different models: the two-dimensional Bremen model, the two chemistry-transport models KASIMA and SLIMCAT, and the two chemistry-climate models EMAC and SOCOL. Thereby, the ability of the models to reproduce the absolute total column amounts, the seasonal cycles, and the temporal evolution found in the FTIR measurements is investigated and inter-compared. This is especially interesting because the models have different architectures. The overall agreement between the measurements and models for the total column abundances and the seasonal cycles is good. Linear trends of HCl, ClONO2, and HF are calculated from both measurement and model time series data, with a focus on the time range 2000–2009. This period is chosen because from most of the measurement sites taking part in this study, data are available during these years. The precision of the trends is estimated with the bootstrap resampling method. The sensitivity of the trend results with respect to the fitting function, the time of year chosen and time series length is investigated, as well as a bias due to the irregular sampling of the measurements. The measurements and model results investigated here agree qualitatively on a decrease of the chlorine species by around 1%yr-1. The models simulate an increase of HF of around 1%yr-1. This also agrees well with most of the measurements, but some of the FTIR series in the Northern Hemisphere show a stabilisation or even a decrease in the last few years. In general, for all three gases, the measured trends vary more strongly with latitude and hemisphere than the modelled trends. Relative to the FTIR measurements, the models tend to underestimate the decreasing chlorine trends and to overestimate the fluorine increase in the Northern Hemisphere. At most sites, the models simulate a stronger decrease of ClONO2 than of HCl. In the FTIR measurements, this difference between the trends of HCl and ClONO2 depends strongly on latitude, especially in the Northern Hemisphere. [less ▲]

Echecs

E-print/Working paper (2012)

Echecs est un roman inédit de Jean-Philippe Toussaint, antérieur à La Salle de bain. Il est ici édité avec un apparat critique: variantes et notes critiques.