Approaches for retrieving abundances of methane isotopologues in the frame of the AGACC project from ground-based FTIR observations performed at the Jungfraujoch

Poster (2007, April)

This work has been performed within the frame of AGACC(http://www.oma.be/AGACC/Home.html), a contribution to the Belgian Scientific Support for a Sustainable Development. The project intends to make an ... [more ▼]

This work has been performed within the frame of AGACC(http://www.oma.be/AGACC/Home.html), a contribution to the Belgian Scientific Support for a Sustainable Development. The project intends to make an advanced exploitation of existing ground-based remote-sensing measurements for a selection of atmospheric species that play an important role in the chemistry of the atmosphere and that have a direct or indirect impact on climate. Target species include -among others- lower tropospheric aerosols, H2O, HDO, CH4, HCN and CO. The instrumentation includes 3 types of spectrometers (FTIR, MAXDOAS and Brewer) and one CIMEL sun photometer. These instruments are operated at 3 different sites (Jungfraujoch, Ile de la Réunion and Uccle) and most of them are affiliated with the Network for the Detection of Atmospheric Composition Change (NDACC, formerly NDSC - http://www.ndacc.org), a group dedicated to performing high-quality long-term observations. This contribution will deal with the detection of the isotopologues of methane, a species released to the atmosphere by natural processes (e.g. wetlands, termites) as well as by anthropogenic activities (e.g. fossil fuel exploitation, rice agriculture, biomass burning, etc). Due to its high warming potential and its relatively long chemical lifetime, atmospheric methane is a major greenhouse gas. Methane also affects climate by influencing tropospheric ozone and stratospheric water. The cycle of methane is complex and a thoroughly study of the sources and sinks of its main isotopologue, as well as the other isotopic species, is necessary to characterize it. Isotopic ratios are also useful to differentiate between various sources of atmospheric methane. To study the vertical distribution of methane isotopologues from the high resolution FTIR spectra recorded by the University of Liège instrument at the International Scientific Station of the Jungfraujoch (ISSJ; 46.5°N, 8.0°E, 3580m a.s.l., Swiss Alps), we have selected several 13CH4 lines distributed in the so-called InSb (1-5 µm) and MCT (2-16 µm) spectral ranges. A set of four microwindows has also been selected for the study of CH3D. Using the SFIT-2 v3.91 algorithm, vertical column abundances as well as low-resolution vertical distributions have been retrieved, adjusted from an a priori profile defined on a 41 layers scheme and derived from ACE-FTS space observations. The information content and first preliminary retrieval results will be presented. [less ▲]

Geophysical validation of MIPAS-ENVISAT operational ozone data

in Atmospheric Chemistry and Physics (2007), 7(18), 4807-4867

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), on-board the European ENVIronmental SATellite (ENVISAT) launched on 1 March 2002, is a middle infrared Fourier Transform spectrometer ... [more ▼]

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), on-board the European ENVIronmental SATellite (ENVISAT) launched on 1 March 2002, is a middle infrared Fourier Transform spectrometer measuring the atmospheric emission spectrum in limb sounding geometry. The instrument is capable to retrieve the vertical distribution of temperature and trace gases, aiming at the study of climate and atmospheric chemistry and dynamics, and at applications to data assimilation and weather forecasting. MIPAS operated in its standard observation mode for approximately two years, from July 2002 to March 2004, with scans performed at nominal spectral resolution of 0.025 cm(-1) and covering the altitude range from the mesosphere to the upper troposphere with relatively high vertical resolution (about 3 km in the stratosphere). Only reduced spectral resolution measurements have been performed subsequently. MIPAS data were re-processed by ESA using updated versions of the Instrument Processing Facility (IPF v4.61 and v4.62) and provided a complete set of level-2 operational products (geo-located vertical profiles of temperature and volume mixing ratio of H2O, O-3, HNO3, CH4, N2O and NO2) with quasi continuous and global coverage in the period of MIPAS full spectral resolution mission. In this paper, we report a detailed description of the validation of MIPAS-ENVISAT operational ozone data, that was based on the comparison between MIPAS v4.61 (and, to a lesser extent, v4.62) O-3 VMR profiles and a comprehensive set of correlative data, including observations from ozone sondes, ground-based lidar, FTIR and microwave radiometers, remote-sensing and in situ instruments on-board stratospheric aircraft and balloons, concurrent satellite sensors and ozone fields assimilated by the European Center for Medium-range Weather Forecasting. A coordinated effort was carried out, using common criteria for the selection of individual validation data sets, and similar methods for the comparisons. This enabled merging the individual results from a variety of independent reference measurements of proven quality (i.e. well characterized error budget) into an overall evaluation of MIPAS O-3 data quality, having both statistical strength and the widest spatial and temporal coverage. Collocated measurements from ozone sondes and ground-based lidar and microwave radiometers of the Network for the Detection Atmospheric Composition Change (NDACC) were selected to carry out comparisons with time series of MIPAS O-3 partial columns and to identify groups of stations and time periods with a uniform pattern of ozone differences, that were subsequently used for a vertically resolved statistical analysis. The results of the comparison are classified according to synoptic and regional systems and to altitude intervals, showing a generally good agreement within the comparison error bars in the upper and middle stratosphere. Significant differences emerge in the lower stratosphere and are only partly explained by the larger contributions of horizontal and vertical smoothing differences and of collocation errors to the total uncertainty. Further results obtained from a purely statistical analysis of the same data set from NDACC ground-based lidar stations, as well as from additional ozone soundings at middle latitudes and from NDACC ground-based FTIR measurements, confirm the validity of MIPAS O-3 profiles down to the lower stratosphere, with evidence of larger discrepancies at the lowest altitudes. The validation against O-3 VMR profiles using collocated observations performed by other satellite sensors (SAGE II, POAM III, ODIN-SMR, ACE-FTS, HALOE, GOME) and ECMWF assimilated ozone fields leads to consistent results, that are to a great extent compatible with those obtained from the comparison with ground-based measurements. Excellent agreement in the full vertical range of the comparison is shown with respect to collocated ozone data from stratospheric aircraft and balloon instruments, that was mostly obtained in very good spatial and temporal coincidence with MIPAS scans. This might suggest that the larger differences observed in the upper troposphere and lowermost stratosphere with respect to collocated ground-based and satellite O-3 data are only partly due to a degradation of MIPAS data quality. They should be rather largely ascribed to the natural variability of these altitude regions and to other components of the comparison errors. By combining the results of this large number of validation data sets we derived a general assessment of MIPAS v4.61 and v4.62 ozone data quality. A clear indication of the validity of MIPAS O-3 vertical profiles is obtained for most of the stratosphere, where the mean relative difference with the individual correlative data sets is always lower than +/- 10%. Furthermore, these differences always fall within the combined systematic error (from 1 hPa to 50 hPa) and the standard deviation is fully consistent with the random error of the comparison (from 1 hPa to similar to 30-40 hPa). A degradation in the quality of the agreement is generally observed in the lower stratosphere and upper troposphere, with biases up to 25% at 100 hPa and standard deviation of the global mean differences up to three times larger than the combined random error in the range 50-100 hPa. The larger differences observed at the bottom end of MIPAS retrieved profiles can be associated, as already noticed, to the effects of stronger atmospheric gradients in the UTLS that are perceived differently by the various measurement techniques. However, further components that may degrade the results of the comparison at lower altitudes can be identified as potentially including cloud contamination, which is likely not to have been fully filtered using the current settings of the MIPAS cloud detection algorithm, and in the linear approximation of the forward model that was used for the a priori estimate of systematic error components. The latter, when affecting systematic contributions with a random variability over the spatial and temporal scales of global averages, might result in an underestimation of the random error of the comparison and add up to other error sources, such as the possible underestimates of the p and T error propagation based on the assumption of a 1 K and 2% uncertainties, respectively, on MIPAS temperature and pressure retrievals. At pressure lower than 1 hPa, only a small fraction of the selected validation data set provides correlative ozone data of adequate quality and it is difficult to derive quantitative conclusions about the performance of MIPAS O-3 retrieval for the topmost layers. [less ▲]

FTIR Observations at the Jungfraujoch Station for long-term monitoring of the Troposphere and Validation of the Space-based Sensors.

in Burrows, J.; Borrell, P. (Eds.) Measuring Tropospheric Trace Constituents from Space. (2007)

A remotely actuated suntracker protection for harsh environmental conditions.

(2007)

An empirical line-by-line model for the infrared solar transmittance spectrum from 700 to 5000 cm(-1)

in Journal of Quantitative Spectroscopy & Radiative Transfer (2006), 102(3), 450-463

An empirical line-by-line model for the infrared solar transmittance spectrum is presented. The model can be incorporated into radiative transfer codes to allow fast calculation of all relevant emission ... [more ▼]

An empirical line-by-line model for the infrared solar transmittance spectrum is presented. The model can be incorporated into radiative transfer codes to allow fast calculation of all relevant emission and absorption features in the solar spectrum in the mid-infrared region from 700 to 5000 cm(-1). The transmittance is modelled as a function of the diameter of the field-of-view centered on the solar disk: the line broadening due to solar rotation as well as center-to-limb variations in strength and width are taken into account for stronger lines. Applications of the model presented here are in the fields of terrestrial remote sensing in the mid-infrared spectral region when the sun is used as radiation source or scattered solar radiation contributes to the measured signal and in the fields of atmospheric radiative transfer algorithms which compute the propagation of infrared solar radiation in the terrestrial atmosphere. (c) 2006 Elsevier Ltd. All rights reserved. [less ▲]

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

in Proceedings of the 4th International Symposium on Non-CO2 Greenhouse Gases (2006)

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

in Environmental Sciences (2005), 2(2-3), 295-303

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 ... [more ▼]

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 Atmosphrique et Solaire-University of Lige), 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. [less ▲]

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

in Environmental Sciences (2005), 2(2-3), 283-293

Solar absorption measurements using Fourier transform infrared (FTIR) spectrometry carry information about the atmospheric abundances of many constituents, including non-CO2 greenhouse gases. Such ... [more ▼]

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. [less ▲]

The evolution of inorganic chlorine above the Jungfraujoch station: an update.

in Zerefos, C. S. (Ed.) Proceedings of the 20th Quadrennial Ozone Symposium (2004)

Within the frame of the NDSC, the total vertical column abundances of HCl and ClONO2, by far the two most important inorganic chlorine reservoirs at northern mid-latitudes, have been further monitored ... [more ▼]

Within the frame of the NDSC, the total vertical column abundances of HCl and ClONO2, by far the two most important inorganic chlorine reservoirs at northern mid-latitudes, have been further monitored above the Jungfraujoch station (Swiss Alps, 46.5ºN, 8.0ºE, 3580m a.s.l.), by analyzing infrared solar absorption spectra recorded with very high-resolution Fourier spectrometers. The mean temporal evolution of the sum of their monthly mean abundance time series indicates that the total stratospheric inorganic chlorine loading (Cly) has decreased slowly (-0.7+/-0.3%/yr, 1-sigma) since it peaked in late 1996, at the limit of being statistically significant at the 2-sigma level. Comparison with model calculations and with the evolution of surface total organic chlorine will also be discussed. [less ▲]

Post-Mount Pinatubo eruption ground-based infrared stratospheric column measurements of HNO3, NO, and NO2 and their comparison with model calculations

in Journal of Geophysical Research. Atmospheres (2003), 108(D15),

[1] Infrared solar spectra recorded between July 1991 to March 1992 and November 2002 with the Fourier transform spectrometer on Kitt Peak (31.9 degrees N latitude, 111.6 degrees W longitude, 2.09 km ... [more ▼]

[1] Infrared solar spectra recorded between July 1991 to March 1992 and November 2002 with the Fourier transform spectrometer on Kitt Peak (31.9 degrees N latitude, 111.6 degrees W longitude, 2.09 km altitude) have been analyzed to retrieve stratospheric columns of HNO3, NO, and NO2. The measurements cover a decade time span following the June 1991 Mount Pinatubo volcanic eruption and were recorded typically at 0.01 cm(-1) spectral resolution. The measured HNO3 stratospheric column shows a 20% decline from 9.16 x 10(15) molecules cm(-2) from the first observation in March 1992 to 7.40 x 10(15) molecules cm(-2) at the start of 1996 reaching a broad minimum of 6.95 x 10(15) molecules cm(-2) thereafter. Normalized daytime NO and NO2 stratospheric column trends for the full post-Pinatubo eruption time period equal (+ 1.56 +/- 0.45)% yr(-1), 1 sigma, and (+ 0.52 +/- 0.32)% yr(-1), 1 sigma, respectively. The long-term trends are superimposed on seasonal cycles with ~10% relative amplitudes with respect to mean values, winter maxima for HNO3 and summer maxima for NO and NO2. The measurements have been compared with two-dimensional model calculations utilizing version 6.1 Stratospheric Aerosol and Gas Experiment ( SAGE) II sulfate aerosol surface area density measurements through 1999 and extended to the end of the time series by repeating the 1999 values. The model-calculated HNO3, NO, and NO2 stratospheric column time series agree with the measurements to within ~8% after taking into account the vertical sensitivity of the ground-based measurements. The consistency between the measured and model-calculated stratospheric time series confirms the decreased impact on stratospheric reactive nitrogen chemistry of the key heterogeneous reaction that converts reactive nitrogen to its less active reservoir form as the lower-stratospheric aerosol surface area density declined by a factor of ~20 after the eruption maximum. [less ▲]