Pierre Duchatelet

Evolution of a dozen non-CO2 greenhouse gases above central Europe since the mid-1980s

Abstract High-resolution infrared solar observations have been conducted consistently since the mid-1980s at the International Scientific Station of the Jungfraujoch, Switzerland, by the GIRPAS-ULg team (Groupe Infra-Rouge de Physique Atmosphérique et Solaire-University of Liège), and by colleagues from the Belgian Institute for Space Aeronomy and from the Royal Observatory of Belgium, Brussels. These observations were performed with state-of-the-art Fourier transform infrared (FTIR) spectrometers, revealing specific absorption features of over 20 atmospheric gases in the middle-infrared. Related spectrometric analyses have allowed the derivation of their burdens, seasonal and inter-annual variability, as well as their long-term evolution. In addition to updates of long-term changes for CCl2F2, CHClF2, CH4, N2O, SF6, CO, C2H6 and C2H2 already dealt with at previous Non-CO2 Greenhouse Gases (NCGG) symposia, this paper further reports temporal evolutions observed during the past two decades for a series of other source gases, namely OCS, HCN, CCl3F and CCl4, which also have direct or indirect effects on the radiation balance of the troposphere and on the stratospheric ozone layer.

A global inventory of stratospheric fluorine in 2004 based on Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) measurements

[1] Total fluorine (FTOT) in the stratosphere has been determined using Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) measurements of HF, COF2, COClF, CF4, CCl3F (CFC-11), CCl2F2 (CFC-12), CHClF2 (HCFC-22), CCl2FCClF2 (CFC-113), CH3CClF2 (HCFC-142b), CH2FCF3 (HFC-134a), and SF6. The retrieval of HFC-134a (CH2FCF3) from spaceborne measurements had not been carried out prior to this work. Measurements of these species have been supplemented by data from models to extend the altitude range of the profiles and have also been complemented by estimates of 15 minor fluorine species. Using these data, separate fluorine budgets were determined in five latitude zones (60–82N, 30–60N, 30S–30N, 30–60S, and 60–82S) by averaging over the period of February 2004 to January 2005 inclusive, when possible. Stratospheric FTOT profiles in each latitude zone are nearly linear, with mean stratospheric FTOT values ranging from 2.50 to 2.59 ppbv (with a 1s precision of 0.04–0.07 ppbv and an estimated accuracy of 0.15 ppbv) for each zone. The highest mean FTOT value occurred in the tropics, which is qualitatively consistent with increasing levels of stratospheric fluorine and the mean stratospheric circulation pattern.

The exploitation of ground-based Fourier transform infrared observations for the evaluation of tropospheric trends of greenhouse gases over Europe

Abstract Solar absorption measurements using Fourier transform infrared (FTIR) spectrometry carry information about the atmospheric abundances of many constituents, including non-CO2 greenhouse gases. Such observations have regularly been made for many years as a contribution to the Network for the Detection of Stratospheric Change (NDSC). They are the only ground-based remote sensing observations available nowadays that carry information about a number of greenhouse gases in the free troposphere. This work focuses on the discussion of the information content of FTIR long-term monitoring data of some direct and indirect greenhouse gases (CH4, N2O, O3 and CO and C2H6, respectively), at six NDSC stations in Western Europe. This European FTIR network covers the polar to subtropical regions. At several stations of the network, the observations span more than a decade. Existing spectral time series have been reanalyzed according to a common optimized retrieval strategy, in order to derive distinct tropospheric and stratospheric abundances for the above-mentioned target gases. A bootstrap resampling method has been implemented to evaluate trends of the tropospheric burdens of the target gases, including their uncertainties. In parallel, simulations of the target time series are being made with the Oslo CTM2 model: comparisons between the model results and the observations provide valuable information to improve the model and, in particular, to optimize emission estimates that are used as inputs to the model simulations. The work is being performed within the EC project UFTIR. The paper focuses on N2O for which the first trend results have been obtained.

Monitoring of the variability and long-term evolution of tropospheric constituents by Infrared solar absorption spectrometry at the Jungfraujoch, Switzerland.

The GIRPAS (Groupe Infra-Rouge de Physique Atmospherique et Solaire) of the University of Liege (ULg) has continued to produce total vertical column abundances of over 20 telluric constituents above the international scientific station on the Jungfraujoch, Switzerland, as part of its commitment to long-term investigations of the variability and secular evolution of the earths atmosphere above central Europe. Those species of primary relevance for quantifying and understanding stratospheric chemistry processes controlling the ozone layer depletion, stabilisation, as well as its anticipated recovery (thanks to the successive Montreal Protocol updates) are being studied within the frame of the NDSC (Network for the Detection of Stratospheric Change) of which the Jungfraujoch is a primary site for atmospheric monitoring at northern mid-latitudes. The others are source gases of natural and/or anthropogenic origin, affecting both the greenhouse strength as well as the oxidising capacity of the troposphere and are, thus, of interest to the aims of the Kyoto Protocol. The Jungfraujoch studies of the latter and their specific provision for the validation of past, ongoing and coming space sensors of the atmosphere are definitely in line with TROPOSAT objectives, i.e. seeking “Synergistic use of different instrumentation and platforms for tropospheric measurements”, and supporting the “Development of validation strategies for tropospheric satellite data products”. An original set of volume mixing-ratio profiles retrieved automatically from space-based infrared solar occultation measurements by the ATMOS instrument is reported, as it demonstrates that such profiles can be extended reliably down throughout the free troposphere for a large number of important source gases.