References of "Hannigan, J. W"
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See detailTROPOMI--Sentinel-5 Precursor formaldehyde validation using an extensive network of ground-based Fourier-transform infrared stations
Vigouroux, C.; Langerock, B.; Bauer Aquino, C. A. et al

in Atmospheric Measurement Techniques (2020), 13(7), 3751--3767

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See detailQuantification of Stratospheric Ozone Recovery Due to Anthropogenic Halogens
Salawitch, R. J.; Tribett, W.; Wales, P. et al

Conference (2020, January 14)

Human release of CFCs and other ozone depleting substances (ODS) has led to a slow, steady erosion of the thickness of the global ozone layer over the past several decades. The ozone layer has begun to ... [more ▼]

Human release of CFCs and other ozone depleting substances (ODS) has led to a slow, steady erosion of the thickness of the global ozone layer over the past several decades. The ozone layer has begun to recover due to actions taken under the Montreal Protocol, which has led to a decrease in the atmospheric abundance of ozone depleting substances. Yet, unreported emissions of CFC-11 have led to a slower than expected decline, and there has been a rise in the atmospheric abundance of chlorinated very short lived (VSL) compounds not regulated under the Montreal Protocol. In this presentation, we examine time series of ozone and halogens from a variety of observational platforms to quantify the attribution of the change in stratospheric ozone that is due to halogens. Our focus is on the extra-polar region: i.e., the state of the ozone layer between 55S and 55N where the vast majority of the world’s population resides. We will quantify the effect of continued release of CFC-11 and the presence of chlorinated VSL species on the recovery of the ozone layer. Additionally, we will use atmospheric observations to evaluate several proposed formulations for defining the quantity known as “Equivalent Effective Stratospheric Chlorine” (EESC) and assess the impact of these formulations on the projected recovery of the ozone layer. [less ▲]

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See detailAtmospheric implications of large C2-C5 alkane emissions from the U.S. oil and gas industry
Tzompa-Sosa, Z; Henderson, B H; Keller, C A et al

in Journal of Geophysical Research. Atmospheres (2019), (2013), 1--22

Emissions of C2-C5 alkanes from the U.S. oil and gas sector have changed rapidly over the last decade. We use a nested GEOS-Chem simulation driven by updated 2011NEI emissions with aircraft, surface and ... [more ▼]

Emissions of C2-C5 alkanes from the U.S. oil and gas sector have changed rapidly over the last decade. We use a nested GEOS-Chem simulation driven by updated 2011NEI emissions with aircraft, surface and column observations to 1) examine spatial patterns in the emissions and observed atmospheric abundances of C2-C5 alkanes over the U.S., and 2) estimate the contribution of emissions from the U.S. oil and gas industry to these patterns. The oil and gas sector in the updated 2011NEI contributes over 80% of the total U.S. emissions of ethane (C2H6) and propane (C3H8), and emissions of these species are largest in the central U.S. Observed mixing ratios of C2-C5 alkanes show enhancements over the central U.S. below 2 km. A nested GEOS-Chem simulation underpredicts observed C3H8 mixing ratios in the boundary layer over several U.S. regions and the relative underprediction is not consistent, suggesting C3H8 emissions should receive more attention moving forward. Our decision to consider only C4-C5 alkane emissions as a single lumped species produces a geographic distribution similar to observations. Due to the increasing importance of oil and gas emissions in the U.S., we recommend continued support of existing long-term measurements of C2-C5 alkanes. We suggest additional monitoring of C2-C5 alkanes downwind of northeastern Colorado, Wyoming and western North Dakota to capture changes in these regions. The atmospheric chemistry modeling community should also evaluate whether chemical mechanisms that lump larger alkanes are sufficient to understand air quality issues in regions with large emissions of these species. [less ▲]

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See detailThe influence of biomass burning on the Arctic: Pan-Arctic FTIR observations and model results
Strong, K; Lutsch, E; Conway, S et al

Poster (2018, September)

Transport of biomass burning emissions into the Arctic can cause episodic enhancements of multiple trace gas species. We present a multi-year time series of the total columns of carbon monoxide (CO ... [more ▼]

Transport of biomass burning emissions into the Arctic can cause episodic enhancements of multiple trace gas species. We present a multi-year time series of the total columns of carbon monoxide (CO), hydrogen cyanide (HCN), and ethane (C2H6) measured using Fourier Transform Infrared (FTIR) solar absorption spectroscopy at six high-latitude sites: Eureka, Nunavut; Ny Alesund, Norway; Thule, Greenland; Kiruna, Sweden; Poker Flat, Alaska; and St. Petersburg, Russia, and at three mid-latitude sites; Zugspitze, Germany; Jungfraujoch, Switzerland; and Toronto, Ontario. For each site, the inter-annual trends and seasonal variabilities of the CO total column time series are determined and enhancements above ambient levels are used to identify possible wildfire pollution events. Correlations of HCN and C2H6 with CO, back-trajectories from HYSPLIT and FLEXPART, and fire locations from the Moderate Resolution Spectroradiometer (MODIS) confirm the detections and identify the source regions. The GEOS-Chem chemical transport model is run in tagged mode to determine the relative contributions to the observed enhancements from continental-scale biomass burning source regions. Exceptional emissions of CO, HCN, C2H6, and ammonia (NH3) from the 2017 North American wildfires were measured at Eureka and Thule, indicating that wildfires may be a major source of NH3 in the summertime high Arctic. The enhancement ratios of the long-lived species HCN and C2H6 are found to be comparable between sites, but for NH3, the enhancement ratios are strongly dependent on the transport patterns of the smoke plumes. Satellite measurements of NH3 from the Infrared Atmospheric Sounding Instrument (IASI) and Cross-track Infrared Sounder (CrIS) are used to examine the spatial and temporal variabilities of NH3. Comparisons to a high-resolution (0.25° x 0.3125°) nested run of GEOS-Chem using emissions from the Global Fire Assimilation System (GFAS) are performed to evaluate the emission inventories and assess the long-range transport of NH3 to the high Arctic. [less ▲]

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See detailTropospheric Ozone Assessment Report: Present-day distribution and trends of tropospheric ozone relevant to climate and global atmospheric chemistry model evaluation
Gaudel, A.; Cooper, O. R.; Ancellet, G. et al

in Elementa: Science of the Anthropocene (2018), 6(1), 39

The Tropospheric Ozone Assessment Report (TOAR) is an activity of the International Global Atmospheric Chemistry Project. This paper is a component of the report, focusing on the present-day distribution ... [more ▼]

The Tropospheric Ozone Assessment Report (TOAR) is an activity of the International Global Atmospheric Chemistry Project. This paper is a component of the report, focusing on the present-day distribution and trends of tropospheric ozone relevant to climate and global atmospheric chemistry model evaluation. Utilizing the TOAR surface ozone database, several figures present the global distribution and trends of daytime average ozone at 2702 non-urban monitoring sites, highlighting the regions and seasons of the world with the greatest ozone levels. Similarly, ozonesonde and commercial aircraft observations reveal ozone’s distribution throughout the depth of the free troposphere. Long-term surface observations are limited in their global spatial coverage, but data from remote locations indicate that ozone in the 21st century is greater than during the 1970s and 1980s. While some remote sites and many sites in the heavily polluted regions of East Asia show ozone increases since 2000, many others show decreases and there is no clear global pattern for surface ozone changes since 2000. Two new satellite products provide detailed views of ozone in the lower troposphere across East Asia and Europe, revealing the full spatial extent of the spring and summer ozone enhancements across eastern China that cannot be assessed from limited surface observations. Sufficient data are now available (ozonesondes, satellite, aircraft) across the tropics from South America eastwards to the western Pacific Ocean, to indicate a likely tropospheric column ozone increase since the 1990s. The 2014–2016 mean tropospheric ozone burden (TOB) between 60˚N–60˚S from five satellite products is 300 Tg ± 4%. While this agreement is excellent, the products differ in their quantification of TOB trends and further work is required to reconcile the differences. Satellites can now estimate ozone’s global long-wave radiative effect, but evaluation is difficult due to limited in situ observations where the radiative effect is greatest. [less ▲]

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See detailObservation and simulation of ethane (C2H6) at 23 FTIR sites
Mahieu, Emmanuel ULiege; Franco, B.; Pozzer, A. et al

Conference (2018, April 11)

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See detailDetection of the long-range transport of wildfire pollution to the Arctic using a network of ground-based FTIR spectrometers, satellite observations and model results
Lutsch, E; Conway, S; Strong, K et al

Conference (2017, December 14)

We present a multi-year time series of the total columns of carbon monoxide (CO), hydrogen cyanide (HCN) and ethane (C2H6) obtained by Fourier Transform Infrared (FTIR) spectrometer measurements at nine ... [more ▼]

We present a multi-year time series of the total columns of carbon monoxide (CO), hydrogen cyanide (HCN) and ethane (C2H6) obtained by Fourier Transform Infrared (FTIR) spectrometer measurements at nine sites. Six are high-latitude sites: Eureka, Nunavut; Ny Alesund, Norway; Thule, Greenland; Kiruna, Sweden; Poker Flat, Alaska and St. Petersburg, Russia and three are mid-latitude sites; Zugspitze, Germany; Jungfraujoch, Switzerland and Toronto, Ontario. For each site, the inter-annual trends and seasonal variabilities of the CO total column time series are accounted for allowing for ambient concentrations to be determined. Enhancements above ambient levels are then used to identify possible wildfire pollution events. Since the abundance of each trace gas species emitted in a wildfire event is specific to the type of vegetation burned and the burning phase, correlations of CO to the other long-lived wildfire tracers HCN and C2H6 allow for further confirmation of the detection of wildfire pollution. Back-trajectories from HYSPLIT and FLEXPART as well as fire detections from the Moderate Resolution Spectroradiometer (MODIS) allow the source regions of the detected enhancements to be determined while satellite observations of CO from the Measurement of Pollution in the Troposphere (MOPITT) and Infrared Atmospheric Sounding Interferometer (IASI) instruments can be used to track the transport of the smoke plume. Differences in travel times between sites allows ageing of biomass burning plumes to be determined, providing a means to infer the physical and chemical processes affecting the loss of each species during transport. Comparisons of ground-based FTIR measurements to GEOS-Chem chemical transport model results are used to investigate these processes, evaluate wildfire emission inventories and infer the influence of wildfire emissions on the Arctic. [less ▲]

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See detailObservation and simulation of ethane (C2H6) at 23 FTIR sites
Mahieu, Emmanuel ULiege; Franco, B; Pozzer, A et al

Poster (2017, December 13)

Ethane is the most abundant non-methane hydrocarbon (NMHC) in the Earth atmosphere. Its main sources are of anthropogenic origin, with globally 62% from leakage during production and transport of natural ... [more ▼]

Ethane is the most abundant non-methane hydrocarbon (NMHC) in the Earth atmosphere. Its main sources are of anthropogenic origin, with globally 62% from leakage during production and transport of natural gas, 20% from biofuel combustion and 18% from biomass burning. In the Southern hemisphere, anthropogenic emissions are lower which makes biomass burning emissions a more significant source. The main removal process is oxidation by the hydroxyl radical (OH), leading to a mean atmospheric lifetime of 2 months. Until recently, a prolonged decrease of its abundance has been documented, at rates of -1 to -2.7%/yr, with global emissions dropping from 14 to 11 Tg/yr over 1984-2010 owing to successful measures reducing fugitive emissions from its fossil fuel sources. However, subsequent investigations have reported on an upturn in the ethane trend, characterized by a sharp rise from about 2009 onwards. The ethane increase is attributed to the oil and natural gas production boom in North America, although significant changes in OH could also be at play.In the present contribution, we report the trend of ethane at 23 ground-based Fourier Transform Infrared (FTIR) sites spanning the 80ºN to 79ºS latitude range. Over 2010-2015, a significant ethane rise of 3-5%/yr is determined for most sites in the Northern Hemisphere, while for the Southern hemisphere the rates of changes are not significant at the 2-sigma uncertainty level. Dedicated model simulations by EMAC (ECHAM5/MESSy Atmospheric Chemistry; ~1.8×1.8 degrees) implementing various emission scenarios are included in order to support data interpretation. The usual underestimation of the NMHCs emissions in the main inventories is confirmed here for RCP85 (Representative Concentration Pathway Database v8.5). Scaling them by 1.5 is needed to capture the background levels of atmospheric ethane. Moreover, additional and significant emissions (~7 Tg over 2009-2015) are needed to capture the ethane rise in the Northern hemisphere. Attributing them to the oil and gas sector and locating them in North America allows EMAC to produce adequate trends in the Northern hemisphere, but not in the Southern hemisphere, where they are overestimated. Possible causes for this difference are discussed. [less ▲]

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See detailAtmospheric free acidity from cloud processing
Franco, Bruno ULiege; Taraborrelli, Domenico; Gromov, Sergey et al

Conference (2017, June 27)

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See detailValidation of MOPITT carbon monoxide using ground-based Fourier transform infrared spectrometer data from NDACC
Buchholz, R. R.; Deeter, M. N.; Worden, H. M. et al

in Atmospheric Measurement Techniques (2017), 10(5), 1927--1956

The Measurements of Pollution in the Troposphere (MOPITT) satellite instrument provides the longest continuous dataset of carbon monoxide (CO) from space. We perform the first validation of MOPITT version ... [more ▼]

The Measurements of Pollution in the Troposphere (MOPITT) satellite instrument provides the longest continuous dataset of carbon monoxide (CO) from space. We perform the first validation of MOPITT version 6 retrievals using total column CO measurements from ground-based remote-sensing Fourier transform infrared spectrometers (FTSs). Validation uses data recorded at 14 stations, that span a wide range of latitudes (80°N to 78°S), in the Network for the Detection of Atmospheric Composition Change (NDACC). MOPITT measurements are spatially co-located with each station, and different vertical sensitivities between instruments are accounted for by using MOPITT averaging kernels (AKs). All three MOPITT retrieval types are analyzed: thermal infrared (TIR-only), joint thermal and near infrared (TIR–NIR), and near infrared (NIR-only). Generally, MOPITT measurements overestimate CO relative to FTS measurements, but the bias is typically less than 10%. Mean bias is 2.4% for TIR-only, 5.1% for TIR–NIR, and 6.5% for NIR-only. The TIR–NIR and NIR-only products consistently produce a larger bias and lower correlation than the TIR-only. Validation performance of MOPITT for TIR-only and TIR–NIR retrievals over land or water scenes is equivalent. The four MOPITT detector element pixels are validated separately to account for their different uncertainty characteristics. Pixel 1 produces the highest standard deviation and lowest correlation for all three MOPITT products. However, for TIR-only and TIR–NIR, the error-weighted average that includes all four pixels often provides the best correlation, indicating compensating pixel biases and well-captured error characteristics. We find that MOPITT bias does not depend on latitude but rather is influenced by the proximity to rapidly changing atmospheric CO. MOPITT bias drift has been bound geographically to within ±0.5%/yr or lower at almost all locations. [less ▲]

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See detailIdentifying long-range transport of wildfire emissions to the Arctic by a network of groundbased FTIR spectrometers, satellite observations and transport models
Lutsch, E; Conway, S; Strong, K et al

Conference (2017, June)

We present a multi-year time series of the total column amounts of carbon monoxide (CO), hydrogen cyanide (HCN) and ethane (C2H6) obtained by Fourier Transform Infrared (FTIR) spectrometer measurements at ... [more ▼]

We present a multi-year time series of the total column amounts of carbon monoxide (CO), hydrogen cyanide (HCN) and ethane (C2H6) obtained by Fourier Transform Infrared (FTIR) spectrometer measurements at ten sites. Six high-latitude sites: Eureka, Nunavut (80.02°N, 86.42°W); Ny Alesund, Norway (78.92°N, 11.93°E); Thule, Greenland (76.53°N, 68.74°W); Kiruna, Sweden (67.84°N, 20.41°E); Poker Flat, Alaska (65.11°N, 147.42°W); St. Petersburg, Russia (59.88°N, 29.83°E) and four mid-latitude sites: Bremen, Germany (53.1°N, 8.8°E); Zugspitze, Germany (47.42°N, 10.98°E); Jungfraujoch, Switzerland (46.55°N, 7.98°E) and Toronto, Ontario (43.66°N, 79.40°W). For each site, enhancements of total column amounts above seasonal means are identified and attributed to wildfire events by HYSPLIT and FLEXPART back-trajectories. Wildfire source locations are identified by the MODIS fire hot spot dataset while satellite measurements of CO total columns from IASI illustrate transport of the smoke plume and allow for further confirmation of the observed enhancement. Using the multi-year time series, inter-annual variability of wildfire events is observed. Differences in travel times of the smoke plume between sites allow for ageing of the plume to be determined providing a means to infer the physical and chemical processes affecting the loss of each species during transport. The varying lifetimes of the species and independent measurements at all sites, along with sensitivities to various source regions given by FLEXPART allow for the transport pathways to the Arctic to be investigated. By accounting for the effect of the ageing of the smoke plumes, the measured FTIR enhancement ratios are corrected to obtain emission ratios and emission factors, which are needed to improve the simulation of fire emissions in chemical transport models. [less ▲]

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See detailObservation and simulation of ethane at 22 FTIR sites
Mahieu, Emmanuel ULiege; Franco, Bruno ULiege; Pozzer, Andrea et al

Conference (2017, May 30)

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See detailRevisiting global fossil fuel and biofuel emissions of ethane
Tzompa-Sosa, Z. A.; Mahieu, Emmanuel ULiege; Franco, Bruno ULiege et al

in Journal of Geophysical Research. Atmospheres (2017), 122(4), 2493--2512

Recent measurements over the Northern Hemisphere indicate that the long-term decline in the atmospheric burden of ethane (C2H6) has ended and the abundance increased dramatically between 2010 and 2014 ... [more ▼]

Recent measurements over the Northern Hemisphere indicate that the long-term decline in the atmospheric burden of ethane (C2H6) has ended and the abundance increased dramatically between 2010 and 2014. The rise in C2H6 atmospheric abundances has been attributed to oil and natural gas extraction in North America. Existing global C2H6 emission inventories are based on outdated activity maps that do not account for current oil and natural gas exploitation regions. We present an updated global C2H6 emission inventory based on 2010 satellite-derived CH4 fluxes with adjusted C2H6 emissions over the U.S. from the National Emission Inventory (NEI 2011). We contrast our global 2010 C2H6 emission inventory with one developed for 2001. The C2H6 difference between global anthropogenic emissions is subtle (7.9 versus 7.2 Tg yr−1), but the spatial distribution of the emissions is distinct. In the 2010 C2H6 inventory, fossil fuel sources in the Northern Hemisphere represent half of global C2H6 emissions and 95% of global fossil fuel emissions. Over the U.S., unadjusted NEI 2011 C2H6 emissions produce mixing ratios that are 14–50% of those observed by aircraft observations (2008–2014). When the NEI 2011 C2H6 emission totals are scaled by a factor of 1.4, the Goddard Earth Observing System Chem model largely reproduces a regional suite of observations, with the exception of the central U.S., where it continues to underpredict observed mixing ratios in the lower troposphere. We estimate monthly mean contributions of fossil fuel C2H6 emissions to ozone and peroxyacetyl nitrate surface mixing ratios over North America of ~1% and ~8%, respectively. [less ▲]

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See detailFirst characterization and validation of FORLI-HNO3 vertical profiles retrieved from IASI/Metop
Ronsmans, G.; Langerock, B.; Wespes, C. et al

in Atmospheric Measurement Techniques (2016), 16

Knowing the spatial and seasonal distributions of nitric acid (HNO3) around the globe is of great interest to apprehend the processes regulating stratospheric ozone, especially in the polar regions ... [more ▼]

Knowing the spatial and seasonal distributions of nitric acid (HNO3) around the globe is of great interest to apprehend the processes regulating stratospheric ozone, especially in the polar regions. Thanks to its unprecedented spatial and temporal sampling, the nadir-viewing Infrared Atmospheric Sounding Interferometer (IASI) allows sounding the atmosphere twice a day globally, with good spectral resolution and low noise. With the Fast Optimal Retrievals on Layers for IASI (FORLI) algorithm, we are retrieving, in near-real time, columns as well as vertical profiles of several atmospheric species, amongst which is HNO3. We present in this paper the first characterization of the FORLI-HNO3 profile products, in terms of vertical sensitivity and error budgets. We show that the sensitivity of IASI to HNO3 is highest in the lower stratosphere (10–20km), where the largest amounts of HNO3 are found, but that the vertical sensitivity of IASI only allows one level of information on the profile (DOFS 1). The sensitivity near the surface is negligible in most cases, and for this reason, a partial column (5–35km) is used for the analyses. Both vertical profiles and partial columns are compared to FTIR ground-based measurements from the Network for the Detection of Atmospheric Composition Change (NDACC) to characterize the accuracy and precision of the FORLI-HNO3 product. The profile validation is conducted through the smoothing of the raw FTIR profiles by the IASI averaging kernels and gives good results, with a slight overestimation of IASI measurements in the Upper Troposphere-Lower Stratosphere (UTLS) at the 6 chosen stations (Thule, Kiruna, Jungfraujoch, Izaña, Lauder and Arrival Heights). The validation of the partial columns (5–35km) is also conclusive with a mean correlation of 0.93 between IASI and the FTIR measurements. An initial survey of the HNO3 spatial and seasonal variabilities obtained from IASI measurements for a one year (2011) data set shows that the expected latitudinal gradient of concentrations from low to high latitudes and the large seasonal variability in polar regions (cycle amplitude around 30% of the seasonal signal, peak-to-peak) are well represented with IASI data. [less ▲]

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See detailSPARC Report on the Mystery of Carbon Tetrachloride
Ahmadzai, H; Bock, R P; Burkholder, J B et al

in Liang, Qing; Newman, Paul A; Reimann, Stefan (Eds.) SPARC Report on the Mystery of Carbon Tetrachloride (2016)

The Montreal Protocol (MP) controls the production and consumption of carbon tetrachloride (CCl4 or CTC) and other ozone-depleting substances (ODSs) for emissive uses. CCl4 is a major ODS, accounting for ... [more ▼]

The Montreal Protocol (MP) controls the production and consumption of carbon tetrachloride (CCl4 or CTC) and other ozone-depleting substances (ODSs) for emissive uses. CCl4 is a major ODS, accounting for about 12% of the globally averaged inorganic chlorine and bromine in the stratosphere, compared to 14% for CFC-12 in 2012. In spite of the MP controls, there are large ongoing emissions of CCl4 into the atmosphere. Estimates of emissions from various techniques ought to yield similar numbers. However, the recent WMO/UNEP Scientific Assessment of Ozone Depletion [WMO, 2014] estimated a 2007-2012 CCl4 bottom-up emission of 1-4 Gg/year (1-4 kilotonnes/year), based on country-by-country reports to UNEP, and a global top-down emissions estimate of 57 Gg/ year, based on atmospheric measurements. This 54 Gg/year difference has not been explained. In order to assess the current knowledge on global CCl4 sources and sinks, stakeholders from industrial, governmental, and the scientific communities came together at the “Solving the Mystery of Carbon Tetrachloride” workshop, which was held from 4-6 October 2015 at Empa in Dübendorf, Switzerland. During this workshop, several new findings were brought forward by the participants on CCl4 emissions and related science. • Anthropogenic production and consumption for feedstock and process agent uses (e.g., as approved solvents) are reported to UNEP under the MP. Based on these numbers, global bottom-up emissions of 3 (0-8) Gg/year are estimated for 2007-2013 in this report. This number is also reasonably consistent with this report’s new industry-based bottom-up estimate for fugitive emissions of 2 Gg/year. • By-product emissions from chloromethanes and perchloroethylene plants are newly proposed in this report as significant CCl4 sources, with global emissions estimated from these plants to be 13 Gg/year in 2014. • This report updates the anthropogenic CCl4 emissions estimation as a maximum of ~25 Gg/year. This number is derived by combining the above fugitive and by-product emissions (2 Gg/year and 13 Gg/year, respectively) with 10 Gg/year from legacy emissions plus potential unreported inadvertent emissions from other sources. • Ongoing atmospheric CCl4 measurements within global networks have been exploited for assessing regional emissions. In addition to existing emissions estimates from China and Australia, the workshop prompted research on emissions in the U.S. and Europe. The sum of these four regional emissions is estimated as 21±7.5a Gg/year, but this is not a complete global accounting. These regional top-down emissions estimates also show that most of the CCl4 emissions originate from chemical industrial regions, and are not linked to major population centres. • The total CCl4 lifetime is critical for calculating top-down global emissions. CCl4 is destroyed in the stratosphere, oceans, and soils, complicating the total lifetime estimate. The atmospheric lifetime with respect to stratospheric loss was recently revised to 44 (36-58) years, and remains unchanged in this report. New findings from additional measurement campaigns and reanalysis of physical parameters lead to changes in the ocean lifetime from 94 years to 210 (157-313) years, and in the soil lifetime from 195 years to 375 (288-536) years. • These revised lifetimes lead to an increase of the total lifetime from 26 years in WMO [2014] to 33 (28-41) years. Consequently, CCl4 is lost at a slower rate from the atmosphere. With this new total lifetime, the global top-down emissions calculation decreases from 57 (40-74) Gg/year in WMO [2014] to 40 (25-55) Gg/year. This estimate is relatively consistent with the independent gradient top-down emissions of 30 (25-35) Gg/year, based upon differences between atmospheric measurements of CCl4 in the Northern and Southern Hemispheres. In addition, this new total lifetime implies an upper limit of 3-4 Gg/year of natural emissions, based upon newly reported observations of old air in firn snow. These new CCl4 emissions estimates from the workshop make considerable progress toward closing the emissions discrepancy. The new industrial bottom-up emissions estimate (15 Gg/year total) includes emissions from chloromethanes plants (13 Gg/year) and feedstock fugitive emissions (2 Gg/year). When combined with legacy emissions and unreported inadvertent emissions, this could be up to 25 Gg/year. Top-down emissions estimates are: global 40 (25-55) Gg/year, gradient 30 (25-35) Gg/year, and regional 21 (14-28) Gg/year. While the new bottom-up value is still less than the aggregated top-down values, these estimates reconcile the CCl4 budget discrepancy when considered at the edges of their uncertainties. [less ▲]

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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 ULiege; Mahieu, Emmanuel ULiege; 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 detailRecent ethane increase above North America: comparison between FTIR measurements and model simulations
Franco, Bruno ULiege; Bader, Whitney ULiege; Mahieu, Emmanuel ULiege et al

Conference (2015, June 11)

Ethane (C2H6) has a large impact on tropospheric composition and air quality because of its involvement in the global VOC (volatile organic compound) – HOx – NOx chemistry responsible for generating and ... [more ▼]

Ethane (C2H6) has a large impact on tropospheric composition and air quality because of its involvement in the global VOC (volatile organic compound) – HOx – NOx chemistry responsible for generating and destroying tropospheric ozone. By acting as a major sink for tropospheric OH radicals, the abundance of C2H6 influences the atmospheric content of carbon monoxide and impacts the lifetime of methane. Moreover, it is an important source of PAN, a thermally unstable reservoir for NOx radicals. On a global scale, the main sources of C2H6 are leakage from the production, transport of natural gas loss, biofuel consumption and biomass burning, mainly located in the Northern Hemisphere. Due to its relatively long lifetime of approximately two months, C2H6 is a sensitive indicator of tropospheric pollution and transport. Using an optimized retrieval strategy (see Franco et al., 2014), we present here a 20-year long-term time series of C2H6 column abundance retrieved from ground-based Fourier Transform InfraRed (FTIR) solar spectra recorded from 1994 onwards at the high-altitude station of Jungfraujoch (Swiss Alps, 46.5° N, 3580 m a.s.l.), part of the Network for the Detection of Atmospheric Composition Change (NDACC, see http://www.ndacc.org). After a regular 1994 – 2008 decrease of the C2H6 amounts, which is very consistent with prior major studies (e.g., Aydin et al., 2011; Simpson et al., 2012) and our understanding of global C2H6 emissions, trend analysis using a bootstrap resampling tool reveals a C2H6 upturn and a statistically-significant sharp burden increase from 2009 onwards (Franco et al., 2014). We hypothesize that this observed recent increase in C2H6 could affect the whole Northern Hemisphere and may be related to the recent massive growth in the exploitation of shale gas and tight oil reservoirs. This hypothesis is supported by measurements derived from solar occultation observations performed since 2004 by the Atmospheric Chemistry Experiment – Fourier Transform Spectrometer (ACE-FTS) instrument and at other NDACC sites, namely Toronto (44° N) and Thule (77° N). Indeed, the recent rates of changes characterizing these data sets are consistent in magnitude and sign with the one derived from the FTIR measurements at Jungfraujoch. In contrast, the ethane time series form Lauder (45° S) shows a monotonic decrease over the last two decades. Investigating both the cause and impact on air quality of the C2H6 upturn should be a high priority for the atmospheric chemistry community. [less ▲]

Detailed reference viewed: 93 (10 ULiège)
See detailRemote sensing of the atmospheric composition in the infrared spectral region within the Network for the Detection of Atmospheric Composition Change (NDACC) and the Total Carbon Column Observing Network (TCCON)
Notholt, Justus; Blumenstock, T; Deutscher, N et al

Conference (2015, May 12)

Remote sensing has been established as a powerful tool in atmospheric research. Throughout the last decades satellite and ground-based remote sensing instruments and methods have been developed to sample ... [more ▼]

Remote sensing has been established as a powerful tool in atmospheric research. Throughout the last decades satellite and ground-based remote sensing instruments and methods have been developed to sample the atmosphere from the microwave to the UV/Vis. The international ground based networks NDACC-IR and TCCON are based on solar absorption spectrometry in the infrared. Both networks consist of more than 30 observations sites around the globe, from the high Arctic through mid-latitudes and the tropics to the southern hemisphere and Antarctica. NDACC concentrates on stratospheric observations in relation to ozone chemistry, in many instances, information on the vertical distribution of the target species is determined. Measured trace gases include O3, HCl, HF, HNO3, ClONO2 and many others. In addition, the tropospheric composition is studied by measuring anthropogenic and biogenic species including HCN, OCS, H2O, CO, CH2O, C2H6, and C2H2. The aim of TCCON is to acquire accurate and precise column-averaged abundances of CO2, CH4, N2O, i.e. atmospheric trace gases which have a very small natural variability. TCCON measurements are linked to WMO calibration scales by comparisons with co-incident in situ profiles measured from aircraft or balloon. Results from both networks have been used in many studies in relation to stratospheric ozone chemistry, air-pollution, and with regard to the carbon-cycle. Long-term series are necessary for trend analysis, gaining insight into annual and longer term variability and placing into context shorter term process studies. Due to the similar observation geometry, the ground-based observations are optimally suitable for satellite and model validation and form an essential part of many satellite projects. They also play an important role in the validation of the Copernicus Atmospheric Monitoring Service. In our contribution we will give an overview on the current status of both networks, ongoing efforts to improve network coverage, precision and accuracy, and several examples of scientific highlights. [less ▲]

Detailed reference viewed: 136 (3 ULiège)
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Peer Reviewed
See detailRecent increase of ethane detected in the remote atmosphere of the Northern Hemisphere
Franco, Bruno ULiege; Bader, Whitney ULiege; Bovy, Benoît ULiege et al

Conference (2015, April 13)

Ethane (C2H6) has a large impact on tropospheric composition and air quality because of its involvement in the global VOC (volatile organic compound) – HOx – NOx chemistry responsible for generating and ... [more ▼]

Ethane (C2H6) has a large impact on tropospheric composition and air quality because of its involvement in the global VOC (volatile organic compound) – HOx – NOx chemistry responsible for generating and destroying tropospheric ozone. By acting as a major sink for tropospheric OH radicals, the abundance of C2H6 influences the atmospheric content of carbon monoxide and impacts the lifetime of methane. Moreover, it is an important source of PAN, a thermally unstable reservoir for NOx radicals. On a global scale, the main sources of C2H6 are leakage from the production, transport of natural gas loss, biofuel consumption and biomass burning, mainly located in the Northern Hemisphere. Due to its relatively long lifetime of approximately two months, C2H6 is a sensitive indicator of tropospheric pollution and transport. Using an optimized retrieval strategy (see Franco et al., 2014), we present here a 20-year long-term time series of C2H6 column abundance retrieved from ground-based Fourier Transform InfraRed (FTIR) solar spectra recorded from 1994 onwards at the high-altitude station of Jungfraujoch (Swiss Alps, 46.5° N, 3580 m a.s.l.), part of the Network for the Detection of Atmospheric Composition Change (NDACC, see http://www.ndacc.org). After a regular 1994 – 2008 decrease of the C2H6 amounts, which is very consistent with prior major studies (e.g., Aydin et al., 2011; Simpson et al., 2012) and our understanding of global C2H6 emissions, trend analysis using a bootstrap resampling tool reveals a C2H6 upturn and a statistically-significant sharp burden increase from 2009 onwards (Franco et al., 2014). We hypothesize that this observed recent increase in C2H6 could affect the whole Northern Hemisphere and may be related to the recent massive growth in the exploitation of shale gas and tight oil reservoirs. This hypothesis is supported by measurements derived from solar occultation observations performed since 2004 by the Atmospheric Chemistry Experiment – Fourier Transform Spectrometer (ACE-FTS) instrument and at other NDACC sites, namely Toronto (44° N) and Thule (77° N). Indeed, the recent rates of changes characterizing these data sets are consistent in magnitude and sign with the one derived from the FTIR measurements at Jungfraujoch. In contrast, the ethane time series form Lauder (45° S) shows a monotonic decrease over the last two decades. Investigating both the cause and impact on air quality of the C2H6 upturn should be a high priority for the atmospheric chemistry community. [less ▲]

Detailed reference viewed: 122 (25 ULiège)