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See detailA Reversal of Long-term Global Trends in Atmospheric Ethane and Propane from North American Oil and Natural Gas Emissions
Helmig, D.; Rossabi, S.; Hueber, J. et al

Conference (2016, May 18)

Ethane, the longest-lived and most abundant non-methane hydrocarbon (NMHC) peaked in the background atmosphere around 1970. This was followed by a ~20% reduction of the atmospheric burden and a resulting ... [more ▼]

Ethane, the longest-lived and most abundant non-methane hydrocarbon (NMHC) peaked in the background atmosphere around 1970. This was followed by a ~20% reduction of the atmospheric burden and a resulting atmospheric downward trend for the next four decades, mostly due to reduced emissions from oil and gas industries and stricter air quality controls. Here, we show that the near 40-year trend of declining global ethane halted between 2005-2010 in most of the Northern Hemisphere (NH), and that since it has reversed. The largest increases in ethane and of the shorter-lived propane are seen in the central and eastern U.S. and immediately downwind, identifying this region as the primary source of increased NMHC emissions. The spatial distribution of observed concentration increases for ethane and propane provides convincing evidence that renewed emissions are primarily associated with the growth of oil and natural gas development in North America. Using source region relationships, emission estimates for increases of co-emitted NMHCs and methane, as well as impacts on tropospheric ozone production have been developed. [less ▲]

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See detailEthane rise associated with North American oil and gas exploitation
Franco, Bruno ULg; Mahieu, Emmanuel ULg; Emmons, Louisa et al

Conference (2016, May 18)

Ethane (C2H6) is mainly emitted in the atmosphere from leakage during production and transport of natural gas, biofuel consumption and biomass burning. As it shares concurrent anthropogenic emission ... [more ▼]

Ethane (C2H6) is mainly emitted in the atmosphere from leakage during production and transport of natural gas, biofuel consumption and biomass burning. As it shares concurrent anthropogenic emission sources with methane (CH4), a better understanding of the atmospheric distribution of C2H6 and any trends in its abundance can be used to better constrain the sources of CH4 from oil and gas activities. Until very recently, the C2H6 abundance in the atmosphere has been declining due to the reduction of fugitive emissions as a result of air pollution abatement measures. However, a renewal of the atmospheric C2H6 burden has been detected over North America and Europe from 2009 onwards. It is attributed to the unprecedented growth in the exploitation of shale gas and tight oil reservoirs in North America. Using time series of C2H6 abundance derived from ground-based high-resolution infrared solar absorption spectra recorded at complementary NDACC FTIR sites, we present here sharp C2H6 rises in the Northern Hemisphere, of up to 5 %/yr since 2009. Using model simulations, we show that the HTAP2 bottom-up inventories for anthropogenic emissions greatly underestimate the observed pre-increase C2H6 abundances and that they are too low by a factor two. We also evaluate new top-down emissions of C2H6 from the North American oil and gas activities, biofuel consumption and biomass burning, derived from space-borne observations of CH4 from GOSAT. We find a good agreement with the observations at the North American mid-latitudinal sites, close to regions with high drilling productivity, but an overestimation at remote sites. We also estimate that the North American C2H6 emissions have increased by 75% over the past six years (2009-2014), annihilating the benefits of more than two decades of successful anthropogenic emission reduction, and that the associated annual CH4 emissions from the North American oil and gas sector grew from 20 to 35 Tg/yr over the same period. [less ▲]

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See detailTropospheric water vapour isotopologue data (H216O, H218O and HD16O) as obtained from NDACC/FTIR solar absorption spectra
Barthlott, Sabine; Schneider, Matthias; Hase, Frank et al

in Earth System Science Data Discussions (2016)

We report on the ground-based FTIR (Fourier Transform InfraRed) tropospheric water vapour isotopologue remote sensing data that have been recently made available via the database of NDACC (Network for the ... [more ▼]

We report on the ground-based FTIR (Fourier Transform InfraRed) tropospheric water vapour isotopologue remote sensing data that have been recently made available via the database of NDACC (Network for the Detection of Atmospheric Composition Change; ftp://ftp.cpc.ncep.noaa.gov/ndacc/MUSICA/) and via doi:10.5281/zenodo.48902. Currently, data are available for 12 globally distributed stations. They have been centrally retrieved and quality filtered in the framework of the MUSICA project (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water). We explain particularities of retrieving the water vapour isotopologue state (vertical distribution of H162O, H182O and HD16O) and reveal the need for a new meta-data template for archiving such FTIR isotopologue data. We describe the format of different data components and give recommendations for correct data usage. Data are provided as two data types. The first type is best-suited for tropospheric water vapour distribution studies disregarding different isotopologues (comparison with radiosonde data, analyses of water vapour variability and trends, etc.). The second type is needed for analysing moisture pathways by means of {H2O,delta-D}-pair distributions. [less ▲]

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See detailUsing NDACC column measurements of carbonyl sulfide to estimate its sources and sinks
Wang; Marshall, J; Palm, M et al

in Geophysical Research Abstracts (2016, April 19), 18

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See detailEvaluating ethane and methane emissions associated with the development of oil and natural gas extraction in North America
Franco, Bruno ULg; Mahieu, Emmanuel ULg; Emmons, L. K. et al

in Environmental Research Letters (2016), 11(4), 044010

Sharp rises in the atmospheric abundance of ethane (C2H6) have been detected from 2009 onwards in the Northern Hemisphere as a result of the unprecedented growth in the exploitation of shale gas and tight ... [more ▼]

Sharp rises in the atmospheric abundance of ethane (C2H6) have been detected from 2009 onwards in the Northern Hemisphere as a result of the unprecedented growth in the exploitation of shale gas and tight oil reservoirs in North America. Using time series of C2H6 total columns derived from ground-based FTIR observations made at five selected NDACC sites, we characterize the recent C2H6 evolution and determine growth rates of ~5%/yr at mid-latitudes and of ~3%/yr at remote sites. Results from CAM-chem simulations with the HTAP2 bottom-up inventory for anthropogenic emissions are found to greatly underestimate the current C2H6 abundances. Doubling global emissions is required to reconcile the simulations and the observations prior to 2009. We further estimate that North American anthropogenic C2H6 emissions have increased from 1.6 Tg/yr in 2008 to 2.8 Tg/yr in 2014, i.e. by 75% over these six years. We also completed a second simulation with new top-down emissions of C2H6 from North American oil and gas activities, biofuel consumption and biomass burning, inferred from space-borne observations of methane (CH4) from GOSAT. In this simulation, GEOS-Chem is able to reproduce FTIR measurements at the mid-latitudinal sites, underscoring the impact of the North American oil and gas development on the current C2H6 abundance. Finally we estimate that the North American oil and gas emissions of CH4, a major greenhouse gas, grew from 20 to 35 Tg/yr over the period 2008 to 2014, in association with the recent C2H6 rise. [less ▲]

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See detailDiurnal cycle and multi-decadal trend of formaldehyde in the remote atmosphere near 46° N
Franco, Bruno ULg; Marais, Eloise A.; Bovy, Benoît ULg et al

in Atmospheric Chemistry and Physics (2016), 16

Only very few long-term records of formaldehyde (HCHO) exist that are suitable for trend analysis. Furthermore, many uncertainties remain as to its diurnal cycle, representing a large short-term ... [more ▼]

Only very few long-term records of formaldehyde (HCHO) exist that are suitable for trend analysis. Furthermore, many uncertainties remain as to its diurnal cycle, representing a large short-term variability superimposed on seasonal and inter-annual variations that should be accounted for when comparing ground-based observations to e.g., model results. In this study, we derive a multi-decadal time series (January 1988 – June 2015) of HCHO total columns from ground-based high-resolution Fourier transform infrared (FTIR) solar spectra recorded at the high-altitude station of Jungfraujoch (Swiss Alps, 46.5° N, 8.0° E, 3580 m a.s.l.), allowing for the characterization of the mid-latitudinal atmosphere for background conditions. First we investigate the HCHO diurnal variation, peaking around noontime and mainly driven by the intra-day insolation modulation and methane (CH4) oxidation. We also characterize quantitatively the diurnal cycles by adjusting a parametric model to the observations, which links the daytime to the HCHO columns according to the monthly intra-day regimes. It is then employed to scale all the individual FTIR measurements on a given daytime in order to remove the effect of the intra-day modulation for improving the trend determination and the comparison with HCHO columns simulated by the state-of-the-art chemical transport model GEOS-Chem v9-02. Such a parametric model will be useful to scale the Jungfraujoch HCHO columns on satellite overpass times in the framework of future calibration/validation efforts of space borne sensors. GEOS-Chem sensitivity tests suggest then that the seasonal and inter-annual HCHO column variations above Jungfraujoch are predominantly led by the atmospheric CH4 oxidation, with a maximum contribution of 25 % from the anthropogenic non-methane volatile organic compound precursors during wintertime. Finally, trend analysis of the so-scaled 27-year FTIR time series reveals a long-term evolution of the HCHO columns in the remote troposphere to be related with the atmospheric CH4 fluctuations and the short-term OH variability: +2.9 %/yr between 1988 and 1995, -3.7 %/yr over 1996-2002 and +0.8/% yr from 2003 onwards. [less ▲]

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See detailStratospheric aerosol - Observations, processes, and impact on climate
Kremser, Stefanie; Thomason, Larry W.; von Hobe, Marc et al

in Reviews of Geophysics (Washington, D.C. : 1985) (2016)

Interest in stratospheric aerosol and its role in climate has increased over the last decade due to the observed increase in stratospheric aerosol since 2000 and the potential for changes in the sulfur ... [more ▼]

Interest in stratospheric aerosol and its role in climate has increased over the last decade due to the observed increase in stratospheric aerosol since 2000 and the potential for changes in the sulfur cycle induced by climate change. This review provides an overview about the advances in stratospheric aerosol research since the last comprehensive assessment of stratospheric aerosol was published in 2006. A crucial development since 2006 is the substantial improvement in the agreement between in situ and space-based inferences of stratospheric aerosol properties during volcanically quiescent periods. Furthermore, new measurement systems and techniques, both in situ and space-based, have been developed for measuring physical aerosol properties with greater accuracy and for characterizing aerosol composition. However, these changes induce challenges to constructing a long-term stratospheric aerosol climatology. Currently, changes in stratospheric aerosol levels less than 20% cannot be confidently quantified. The volcanic signals tend to mask any non-volcanically driven change, making them difficult to understand. While the role of carbonyl sulfide (OCS) as a substantial and relatively constant source of stratospheric sulfur has been confirmed by new observations and model simulations, large uncertainties remain with respect to the contribution from anthropogenic sulfur dioxide (SO2) emissions. New evidence has been provided that stratospheric aerosol can also contain small amounts of non-sulfate matter such as black carbon and organics. Chemistry-climate models have substantially increased in quantity and sophistication. In many models the implementation of stratospheric aerosol processes is coupled to radiation and/or stratospheric chemistry modules to account for relevant feedback processes. [less ▲]

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See detailIntercomparison of in-situ NDIR and column FTIR measurements of CO2 at Jungfraujoch
Schibig, M. F.; Mahieu, Emmanuel ULg; Henne, S. et al

in Atmospheric Chemistry & Physics Discussions (2016), 2016

We compare two CO2 time series measured at the High Alpine Research Station Jungfraujoch (3580 m a.s.l., Switzerland) in the period from 2005 to 2013 with an in-situ surface measurement system using a ... [more ▼]

We compare two CO2 time series measured at the High Alpine Research Station Jungfraujoch (3580 m a.s.l., Switzerland) in the period from 2005 to 2013 with an in-situ surface measurement system using a nondispersive infrared analyzer (NDIR) and a ground-based remote sensing system using solar absorption Fourier Transform Infrared spectrometry (FTIR). Although the two data sets show an absolute shift of about 13 ppm, the slopes of the annual CO2 increase are in good agreement within their uncertainties. They are 2.04 ± 0.07 ppm yr-1 and 1.97 ± 0.05 ppm yr-1 for the FTIR and the NDIR system, respectively. The seasonality of the FTIR and the NDIR system is 4.46 ± 1.11 ppm and 10.10 ± 0.73 ppm, respectively. The difference is caused by a dampening of the CO2 signal with increasing altitude due to mixing processes. While the minima of both data series occur in the middle of August, the maxima of the two datasets differ by about ten weeks, the maximum of the FTIR measurements is in middle of January, whereas the maximum of the NDIR measurements is found at the end of March. Sensitivity analyses revealed that the air masses measured by the NDIR system at the surface of Jungfraujoch are mainly influenced by central Europe, whereas the air masses measured by the FTIR system in the column above Jungfraujoch are influenced by regions as far west as the Caribbean and the United States. [less ▲]

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See detailRetrieval of HCFC-142b (CH3CClF2) from ground-based high-resolution infrared solar spectra: Atmospheric increase since 1989 and comparison with surface and satellite measurements
Mahieu, Emmanuel ULg; Lejeune, Bernard ULg; Bovy, Benoît ULg et al

in Journal of Quantitative Spectroscopy & Radiative Transfer (2016)

We have developed an approach for retrieving HCFC-142b (CH3CClF2) from ground-based high-resolution infrared solar spectra, using its ν7 band Q branch in the 900–906 cm-1 interval. Interferences by HNO3 ... [more ▼]

We have developed an approach for retrieving HCFC-142b (CH3CClF2) from ground-based high-resolution infrared solar spectra, using its ν7 band Q branch in the 900–906 cm-1 interval. Interferences by HNO3, CO2 and H2O have to be accounted for. Application of this approach to observations recorded within the framework of long-term monitoring activities carried out at the northern mid-latitude, high-altitude Jungfraujoch station in Switzerland (46.5°N, 8.0°E, 3580 m above sea level) has provided a total column times series spanning the 1989 to mid-2015 time period. A fit to the HCFC-142b daily mean total column time series shows a statistically-significant long-term trend of (1.23±0.08×1013 molec cm-2) per year from 2000 to 2010, at the 2-σ confidence level. This corresponds to a significant atmospheric accumulation of (0.94±0.06) ppt (1 ppt=10-12) per year for the mean tropospheric mixing ratio, at the 2−σ confidence level. Over the subsequent time period (2010–2014), we note a significant slowing down in the HCFC-142b buildup. Our ground-based FTIR (Fourier Transform Infrared) results are compared with relevant data sets derived from surface in situ measurements at the Mace Head and Jungfraujoch sites of the AGAGE (Advanced Global Atmospheric Gases Experiment) network and from occultation measurements by the ACE-FTS (Atmospheric Chemistry Experiment-Fourier Transform Spectrometer) instrument on-board the SCISAT satellite. [less ▲]

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See detailReversal of Long-Term Trends in Ethane Identified from the Global Atmosphere Watch Reactive Gases Measurement Network
Helmig, Detlev; Buchmann, Brigitte; Carpenter, Lucy et al

Poster (2016, March 02)

Reactive gases play an important role in climate and air pollution issues. They control the self-cleansing capability of the troposphere, contribute to air pollution and acid deposition, regulate the ... [more ▼]

Reactive gases play an important role in climate and air pollution issues. They control the self-cleansing capability of the troposphere, contribute to air pollution and acid deposition, regulate the lifetimes and provide tracers for deciphering sources and sinks for greenhouse gases. Within GAW, the focus is placed on long-term, high-quality observations of ozone (O3), carbon monoxide (CO), volatile organic compounds (VOC), nitrogen oxides (NOx), and sulfur dioxide (SO2). More than 100 stations worldwide carry out reactive gases measurements with data reported to two World Data Centers. The reactive gases program in GAW cooperates The WMO GAW Reactive Gases Program with regional networks and other global monitoring initiatives in order to attain a complete picture of the tropospheric chemical composition. Observations are being made by in-situ monitoring, measurements from commercial routine air-crafts (e.g. IAGOS), column observations, and from flask sampling networks. Quality control and coordination of measurements between participating stations are a primary emphasis. GAW reactive gases data in rapid delivery mode are used to evaluate operational atmospheric composition forecasts in the EU Copernicus Atmospheric Monitoring Service. Oversight of the program is provided by GAW-WMO coordinated Reactive Gases Scientific Advisory Committee (RG-SAG). [less ▲]

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See detailSeasonal variability of surface and column carbon monoxide over megacity Paris, high altitude Jungfraujoch and Southern Hemispheric Wollongong stations
Té, Y; Jeseck, P; Franco, Bruno ULg et al

in Atmospheric Chemistry & Physics Discussions (2016)

Carbon monoxide (CO) is an atmospheric key species due to its toxicity and its impact on the atmospheric oxidizing capacity, both factors affecting air quality. The paper studies the altitude dependent ... [more ▼]

Carbon monoxide (CO) is an atmospheric key species due to its toxicity and its impact on the atmospheric oxidizing capacity, both factors affecting air quality. The paper studies the altitude dependent seasonal variability of CO at the three different sites Paris, Jungfraujoch and Wollongong, with an emphasis on establishing a link between the CO vertical distribution and the nature of CO emission sources. The CO seasonal variability obtained from the total columns and from the free tropospheric partial columns shows a maximum around March-April and a minimum around September-October in the Northern Hemisphere (Paris and Jungfraujoch). In the Southern Hemisphere (Wollongong) this seasonal variability is shifted by about 6 months. Satellite observations by IASI-MetOp and MOPITT instruments confirm this seasonality. Ground-based FTIR is demonstrated to provide useful complementary information due to good sensitivity in the boundary layer. In situ surface measurements of CO volume mixing ratios in Paris and at Jungfraujoch reveal a time-lag of the near surface seasonal variability of about 2 months with respect to the total column variability at the same sites. The chemical transport model GEOS-Chem is employed to interpret our observations. GEOS-Chem sensitivity runs allow identifying the emission sources influencing the seasonal cycle of CO. In Paris and on top of Jungfraujoch, the surface seasonality is mainly driven by anthropogenic emissions, while the total column seasonality is also controlled by air masses transported from distant sources. In the case of Wollongong, where the CO seasonality is mainly affected by biomass burning, no time shift is observed between surface and above the boundary layer. [less ▲]

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See detailHCOOH distributions from IASI for 2008-2014: comparison with ground-based FTIR measurements and a global chemistry-transport model
Pommier, M.; Clerbaux, C.; Coheur, P.-F. et al

in Atmospheric Chemistry & Physics Discussions (2016), 2016

Formic acid (HCOOH) is one of the most abundant volatile organic compounds in the atmosphere. It is a major contributor to rain acidity in remote areas. There are however large uncertainties on its ... [more ▼]

Formic acid (HCOOH) is one of the most abundant volatile organic compounds in the atmosphere. It is a major contributor to rain acidity in remote areas. There are however large uncertainties on its sources and sinks, and HCOOH is misrepresented by global chemistry-transport models. This work presents global distributions from 2008 to 2014 as derived from the measurements of the Infrared Atmospheric Sounding Interferometer (IASI), based on conversion factors between brightness temperature differences and representative retrieved total columns over seven regions: Africa N, Africa S, Amazonia, Atlantic, Australia, Pacific and Russia. The dependence of the thermal contrast is taking account in the conversion method. This conversion presents errors lower than 20 % for total columns ranging between 0.5 and 1 × 1016 molec/cm2 but reaches higher values, up to 78 %, for columns lower than 0.3 × 1016 molec/cm2. Signatures from biomass burning events are highlighted, such as in the Southern Hemisphere and in Russia, as well as biogenic emission sources, e.g. over Eastern US. A comparison between 2008 and 2014 with ground-based FTIR measurements obtained at 4 locations (Maido and Saint-Denis at La Réunion, Jungfraujoch and Wollongong) is shown. Although IASI columns are found to correlate well with FTIR data, a large bias (> 100 %) is found over the two sites at La Réunion. A better agreement is found at Wollongong with a negligible bias. The comparison also highlights the difficulty for IASI to retrieve the total columns over mountainous regions such as Jungfraujoch. A comparison of the retrieved columns with the global chemistry-transport model IMAGESv2 is also presented, showing the good representation of the seasonal and inter-annual cycles over America, Australia, Asia and Siberia. A global model underestimation of the distribution and a misrepresentation of the seasonal cycle over India are also noted. A small positive trend in the IASI columns is also observed over Australia, Amazonia and India over 2008–2014 (from 0.7 to 1.5 %/year), while a decrease of ~ 0.8 %/year is measured over Siberia. [less ▲]

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See detailTowards understanding the variability in biospheric CO2 fluxes: using FTIR spectrometry and a chemical transport model to investigate the sources and sinks of carbonyl sulfide and its link to CO2
Wang, Y.; Deutscher, N. M.; Palm, M. et al

in Atmospheric Chemistry and Physics (2016), 16

Understanding carbon dioxide (CO2) biospheric processes is of great importance because the terrestrial exchange drives the seasonal and interannual variability of CO2 in the atmosphere. Atmospheric ... [more ▼]

Understanding carbon dioxide (CO2) biospheric processes is of great importance because the terrestrial exchange drives the seasonal and interannual variability of CO2 in the atmosphere. Atmospheric inversions based on CO2 concentration measurements alone can only determine net biosphere fluxes, but not differentiate between photosynthesis (uptake) and respiration (production). Carbonyl sulfide (OCS) could provide an important additional constraint: it is also taken up by plants during photosynthesis but not emitted during respiration, and therefore is a potential means to differentiate between these processes. Solar absorption Fourier Transform InfraRed (FTIR) spectrometry allows for the retrievals of the atmospheric concentrations of both CO2 and OCS from measured solar absorption spectra. Here, we investigate co-located and quasi-simultaneous FTIR measurements of OCS and CO2 performed at five selected sites located in the Northern Hemisphere. These measurements are compared to simulations of OCS and CO2 using a chemical transport model (GEOS-Chem). The coupled biospheric fluxes of OCS and CO2 from the simple biosphere model (SiB) are used in the study. The CO2 simulation with SiB fluxes agrees with the measurements well, while the OCS simulation reproduced a weaker drawdown than FTIR measurements at selected sites, and a smaller latitudinal gradient in the Northern Hemisphere during growing season when comparing with HIPPO (HIAPER Pole-to-Pole Observations) data spanning both hemispheres. An offset in the timing of the seasonal cycle minimum between SiB simulation and measurements is also seen. Using OCS as a photosynthesis proxy can help to understand how the biospheric processes are reproduced in models and to further understand the carbon cycle in the real world. [less ▲]

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See detailINVESTIGATING MODEL DEFICIENCIES IN THE GLOBAL BUDGET OF ETHANE
Tzompa-Sosa, Z. A.; Keller, C. A.; Turner, A. J. et al

Poster (2015, December 14)

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See detailNonparametric estimation and bootstrap inference on recent trends in atmospheric ethane
Friedrich, Marina; Reuvers, H.; Smeekes, S. et al

Conference (2015, December 12)

Ethane is the most abundant non-methane hydrocarbon in the Earth's atmosphere and an important precursor of tropospheric ozone. Its monitoring is therefore crucial for the characterization of air quality ... [more ▼]

Ethane is the most abundant non-methane hydrocarbon in the Earth's atmosphere and an important precursor of tropospheric ozone. Its monitoring is therefore crucial for the characterization of air quality and of the transport of tropospheric pollution. Ethane is also an indirect greenhouse gas, influencing the atmospheric lifetime of methane. The main sources of ethane are located in the northern hemisphere, and the dominating emissions are associated to production and transport of natural gas. A preliminary trend analysis was conducted using measurements performed in the Swiss Alps. Over the last two decades, the trend of ethane showed a decline of around 1% per year, thanks to a reduction of fugitive emissions of fossil fuel sources. However, a recent upturn potentially attributed to the massive exploitation of shale gas and tight oil reservoirs in North America was found. The goal is to investigate the presence and form of changes in trend functions using nonparametric techniques. The possible location of such changes is investigated. In addition, nonparametric estimation techniques are used to allow for nonlinear trend functions. Given the nonstandard nature of the measurements we rely on dependent wild bootstrap techniques to conduct inference on possible breaks in linear trends and on nonparametric trend functions. [less ▲]

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See detailRetrieval of ammonia from ground-based FTIR solar spectra
Dammers, Enrico; Vigouroux, C; Palm, M et al

in Atmospheric Chemistry and Physics (2015), 15

We present a retrieval method for ammonia (NH3) total columns from ground-based Fourier Transform InfraRed (FTIR) observations. Observations from Bremen (53.10° N, 8.85° E), Lauder (45.04° S, 169.68° E ... [more ▼]

We present a retrieval method for ammonia (NH3) total columns from ground-based Fourier Transform InfraRed (FTIR) observations. Observations from Bremen (53.10° N, 8.85° E), Lauder (45.04° S, 169.68° E), Reunion (20.9° S, 55.50° E) and Jungfraujoch (46.55° N, 7.98° E) were used to illustrate the capabilities of the method. NH3 mean total columns ranging three orders of magnitude were obtained with higher values at Bremen (mean of 13.47 × 1015 molecules cm-2) to the lower values at Jungfraujoch (mean of 0.18 × 1015 molecules cm-2). In conditions with high surface concentrations of ammonia, as in Bremen, it is possible to retrieve information on the vertical gradient as two layers can be discriminated. The retrieval there is most sensitive to ammonia in the planetary boundary layer, where the trace gas concentration is highest. For conditions with low concentrations only the total column can be retrieved. Combining the systematic and random errors we have a mean total error of 26 % for all spectra measured at Bremen (Number of spectra (N) = 554), 30 % for all spectra from Lauder (N =2412), 25 % for spectra from Reunion (N =1262) and 34 % for spectra measured at Jungfraujoch (N =2702). The error is dominated by the systematic uncertainties in the spectroscopy parameters. Station specific seasonal cycles were found to be consistent with known seasonal cycles of the dominant ammonia sources in the station surroundings. The developed retrieval methodology from FTIR-instruments provides a new way to obtain highly time-resolved measurements of ammonia burdens. FTIR-NH3 observations will be useful for understanding the dynamics of ammonia concentrations in the atmosphere and for satellite and model validation. It will also provide additional information to constrain the global ammonia budget. [less ▲]

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See detailDecrease of carbon tetrachloride (CCl4) over 2004-2013 as inferred from global occultation measurements with ACE-FTS
Mahieu, Emmanuel ULg; Bernath, P. F.; Boone, C. D. et al

Poster (2015, October 05)

In this contribution, we use infrared solar occultation measurements performed by the ACE-FTS (Atmospheric Chemistry Experiment – Fourier Transform Spectrometer) instrument onboard the SCISAT-1 Canadian ... [more ▼]

In this contribution, we use infrared solar occultation measurements performed by the ACE-FTS (Atmospheric Chemistry Experiment – Fourier Transform Spectrometer) instrument onboard the SCISAT-1 Canadian satellite (Bernath et al., 2005). Since its launch in August 2003, this spectrometer has been in continuous operation with no significant degradation of its performance, and global measurements are available from late February 2004 onwards, spanning now more than a decade. [less ▲]

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See detailCurrent trend in carbon tetrachloride from several NDACC FTIR stations
Hannigan, J.; Palm, M.; Conway, S. et al

Conference (2015, October 05)

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See detailPhysicochimie de la pollution atmosphérique
Mahieu, Emmanuel ULg

Conference (2015, September 25)

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See detailAcetylene (C2H2) and hydrogen cyanide (HCN) from IASI satellite observations: global distributions, validation, and comparison with model
Duflot, V.; Wespes, C.; Clarisse, L. et al

in Atmospheric Chemistry and Physics (2015), 15

We present global distributions of C2H2 and hydrogen cyanide (HCN) total columns derived from the Infrared Atmospheric Sounding Interferometer (IASI) for the years 2008–2010. These distributions are ... [more ▼]

We present global distributions of C2H2 and hydrogen cyanide (HCN) total columns derived from the Infrared Atmospheric Sounding Interferometer (IASI) for the years 2008–2010. These distributions are obtained with a fast method allowing to retrieve C2H2 abundance globally with a 5% precision and HCN abundance in the tropical (subtropical) belt with a 10% (25 %) precision. IASI data are compared for validation purposes with ground-based Fourier transform infrared (FTIR) spectrometer measurements at four selected stations. We show that there is an overall agreement between the ground-based and space measurements with correlation coefficients for daily mean measurements ranging from 0.28 to 0.81, depending on the site. Global C2H2 and subtropical HCN abundances retrieved from IASI spectra show the expected seasonality linked to variations in the anthropogenic emissions and seasonal biomass burning activity, as well as exceptional events, and are in good agreement with previous spaceborne studies. Total columns simulated by the Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4) are compared to the ground-based FTIR measurements at the four selected stations. The model is able to capture the seasonality in the two species in most of the cases, with correlation coefficients for daily mean measurements ranging from 0.50 to 0.86, depending on the site. IASI measurements are also compared to the distributions from MOZART-4. Seasonal cycles observed from satellite data are reasonably well reproduced by the model with correlation coefficients ranging from -0.31 to 0.93 for C2H2 daily means, and from 0.09 to 0.86 for HCN daily means, depending on the considered region. However, the anthropogenic (biomass burning) emissions used in the model seem to be overestimated (underestimated), and a negative global mean bias of 1% (16 %) of the model relative to the satellite observations was found for C2H2 (HCN). [less ▲]

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