Article

Estimating emissions of HCFC-22 and CFC-11 in China by atmospheric observations and inverse modeling

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

This paper presents the estimation of Chinese emissions of HCFC-22 and CFC-11 in 2009 by an inverse modeling method based on in-situ measurement data from the Shangdianzi Global Atmosphere Watch (GAW) Regional Station (SDZ) and atmospheric transport simulations. After inversion (a-posteriori) estimates of the Chinese emissions in 2009 increased by 6.6% for HCFC-22 from 91.7 (± 83.6) to 98.3 (± 47.4) kt/yr and by 22.5% for CFC-11 from 13 (±12.6) to 15.8 (±7.2) kt/yr compared to an a-priori emission. While the model simulation with a-priori emissions already captured the main features of the observed variability at the measurement site, the model performance (in terms of correlation and mean-square-error) improved using a-posteriori emissions. The inversion reduced the root-mean-square (RMS) error by 4% and 10% for HCFC-22 and CFC-11, respectively.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Wan et al., 25 Fang et al., 19 Wang et al., 20 and Fang et al. 28 are emission estimates for the whole of China. Those from Kim et al., 26 An et al., 27 and Rigby et al. 6 are for eastern China. We have included all of these estimates accepting that we are not always comparing like with like as there was no clear difference between CFC-11 emission estimates for the whole Figure 3). ...
... Seasonal variations in emission ratios in this region are not well constrained. Kim et al.,26 in their estimates of halocarbon emissions from China, assumed 25 Kim et al., 26 An et al., 27 Fang et al., 19 Wang et al., 20 and Fang et al. 28 The 2014−2018 mean is the mean of the seven interspecies correlation estimates in this study. Emissions for the whole of China have filled data points, and emissions for eastern China have clear data points. ...
Article
Full-text available
Recent findings of an unexpected slowdown in the decline of CFC-11 mixing ratios in the atmosphere have led to the conclusion that global CFC-11 emissions have increased over the last decade and have been attributed in part to eastern China. This study independently assesses these findings by evaluating enhancements of CFC-11 mixing ratios in air samples collected in Taiwan between 2014 and 2018. Using the NAME (Numerical Atmospheric Modelling Environment) particle dispersion model we find the likely source of the enhanced CFC-11 observed in Taiwan to be East China. Other halogenated trace gases were also measured and there were positive interspecies correlations between CFC-11 and CHCl3, CCl4, HCFC-141b, HCFC-142b, CH2Cl2 and HCFC-22, indicating co-location of the emissions of these compounds. These correlations in combination with published emission estimates of CH2Cl2 and HCFC-22 from China, and of CHCl3 and CCl4 from eastern China, are used to estimate CFC-11 emissions. Within the uncertainties, these estimates do not differ for eastern China and the whole of China, so we combine them to derive a mean estimate which we refer to as being from ‘(eastern) China’. For 2014-2018 we estimate an emission of 19 ± 5 Gg yr⁻¹ (gigagrams per year) of CFC-11 from (eastern) China, approximately one quarter of global emissions. Comparing this to previously reported CFC-11 emissions estimated for earlier years we estimate CFC-11 emissions from (eastern) China to have increased by 7 ± 5 Gg yr⁻¹ from the 2008-2011 average to the 2014-2018 average, which is 50 ± 40% of the estimated increase in global CFC-11 emissions and is consistent with the emission increases attributed to this region in an earlier study.
... The REBS method introduced by Ruckstuhl et al. (2012) is a statistical method using a robust local regression model to identify background observations from each individual observation station to estimate a baseline curve. In recent years it has been used in various studies to determine a baseline for atmospheric inversions of several GHG species (e.g., An et al., 2012;Brunner et al., 2017;Henne et al., 2016;Schoenenberger et al., 2018;Simmonds et al., 2016;. The REBS method defines observed mixing ratios y(t i ) at each time step t i as the sum of a baseline signal g(t i ), an enhancement due to polluted air masses m(t i ), and the observational error E i : ...
Article
Full-text available
Using the example of sulfur hexafluoride (SF6), we investigate the use of Lagrangian particle dispersion models (LPDMs) for inverse modeling of greenhouse gas (GHG) emissions and explore the limitations of this approach. We put the main focus on the impacts of baseline methods and the LPDM backward simulation period on the a posteriori emissions determined by the inversion. We consider baseline methods that are based on a statistical selection of observations at individual measurement sites and a global-distribution-based (GDB) approach, where global mixing ratio fields are coupled to the LPDM back-trajectories at their termination points. We show that purely statistical baseline methods can cause large systematic errors, which lead to inversion results that are sensitive to the LPDM backward simulation period and can generate unrealistic global total a posteriori emissions. The GDB method produces a posteriori emissions that are far less sensitive to the backward simulation period and that show a better agreement with recognized global total emissions. Our results show that longer backward simulation periods, beyond the often used 5 to 10 d, reduce the mean squared error and increase the correlation between a priori modeled and observed mixing ratios. Also, the inversion becomes less sensitive to biases in the a priori emissions and the global mixing ratio fields for longer backward simulation periods. Further, longer periods might help to better constrain emissions in regions poorly covered by the global SF6 monitoring network. We find that the inclusion of existing flask measurements in the inversion helps to further close these gaps and suggest that a few additional and well-placed flask sampling sites would have great value for improving global a posteriori emission fields.
... Furthermore, given that China has been the largest producer and consumer of HCFCs since 2003, and that production of HCFC-22 accounts for more than 80 % of all Chinese HCFC production (UNEP, 2009), HCFC-22 is the best-suited reference compound for use with China. Additionally, strong Chinese HCFC-22 emissions have been determined from atmospheric observations and inverse modeling in previous studies Li et al., 2011;Stohl et al., 2010;An et al., 2012;Fang et al., 2012), with estimates ranging from 46 to 146 Gg yr −1 over the period 2007-2009. Our estimates of annual HCFC-22 emissions in China for 2008-2015 were independently derived from atmospheric measurements at GSN using an inverse technique based on FLEXible PARTicle dispersion model (FLEXPART) Lagrangian transport model analysis Fang et al., 2014) and ranged from 89 Gg yr −1 in 2011 to 144 Gg yr −1 in 2015. ...
Article
Full-text available
Carbon tetrachloride (CCl4) is a first-generation ozone-depleting substance, and its emissive use and production were globally banned by the Montreal Protocol with a 2010 phase-out; however, production and consumption for non-dispersive use as a chemical feedstock and as a process agent are still allowed. This study uses the high frequency and magnitude of CCl4 pollution events from an 8-year real-time atmospheric measurement record obtained at Gosan station (a regional background monitoring site in East Asia) to present evidence of significant unreported emissions of CCl4. Top-down emissions of CCl4 amounting to 23.6±7.1 Gg yr−1 from 2011 to 2015 are estimated for China, in contrast to the most recently reported, post-2010, Chinese bottom-up emissions of 4.3–5.2 Gg yr−1. The missing emissions ( ∼ 19 Gg yr−1) for China contribute to approximately 54 % of global CCl4 emissions. It is also shown that 89 % ± 6 % of CCl4 enhancements observed at Gosan are related to CCl4 emissions from the production of CH3Cl, CH2Cl2, CHCl3 and C2Cl4 and its usage as a feedstock and process agent in chemical manufacturing industries. Specific sources and processes are identified using statistical methods, and it is considered highly unlikely that CCl4 is emitted by dispersive uses such as old landfills, contaminated soils and solvent usage. It is thus crucial to implement technical improvements and better regulation strategies to reduce evaporative losses of CCl4 occurring at the factory and/or process levels.
... Many studies have attempted to estimate HCFC-22 emissions in China. Stohl et al. (2009Stohl et al. ( , 2010 Kim et al. (2010), An et al. (2012), and Fortems-Cheiney et al. (2013) estimated emissions for 2007, 2009, and 2007e2008, respectively. Fang et al. (2012 estimated HCFC-22 emissions for 2010 based on an interspecies correlation method. ...
Article
Halogenated gases include ozone-depleting substances and greenhouse gases, such as chlorofluorocarbons, halons, hydrochlorofluorocarbons, hydrofluorocarbons, and perfluorinated gases. In situ atmospheric observations of major halogenated gases were conducted at the Shangdianzi (SDZ) background station, China, from October 2020 to September 2021 using ODS5-pro, a newly developed measurement system. The measurement time series of 36 halogenated gases showed occasional pollution events, where background conditions represented 25% (CH2Cl2) to 81% (CF3Cl, CFC-13) of the measurements. The annual mean background mole fractions of most species at SDZ were consistent with those obtained at the Mace Head station in Ireland. The background conditions were distinguished from pollution events, and the enhanced mole fractions were used to estimate the emissions of four categories of fluorinated gases (F-gases) from northern China using a tracer ratio method. The CO2-equivalent (CO2-equiv) emission of F-gases from northern China reached 181 ± 18 Tg year-1 during 2020-2021. Among the four categories of F-gases estimated, SF6 accounted for the highest proportion of CO2-equiv emissions (24%), followed by HFC-23 (22%), HFC-125 (17%), HFC-134a (13%), NF3 (10%), CF4 (5.9%), HFC-143a (3.9%), HFC-32 (3.4%), and HFC-152a (0.2%).
Preprint
Full-text available
Trifluoromethane (CHF3, HFC-23), one of the most potent greenhouse gases among HFCs, is mainly emitted to the atmosphere as a by-product in the production of the ozone depleting legacy refrigerant and chemical feedstock chlorodifluoromethane (CHClF2, HCFC-22). A recent study on global HFC-23 emissions (Stanley et al., 2020) showed significant discrepancies over 2014–2017 between the increase in the observation-derived (top-down) emissions and the 87 % emission reduction expected from capture and destruction processes of HFC-23 at HCFC-22 production facilities mandated by national phase-out plans (bottom-up). However, the actual sources of the increased emissions were not identified. Here, we estimate the regional top-down emissions of HFC-23 for East Asia based on in situ measurements at Gosan, South Korea, and show that the HFC-23 emissions from eastern China have increased from 5.0 ± 0.4 Gg yr-1 in 2008 to 9.5 ± 1.0 Gg yr-1 in 2019. The continuous rise was contrary to the large emissions reduction reported since 2015 under the Chinese hydrochlorofluorocarbons production phase-out management plan (HPPMP). The magnitude of the mismatch between top-down and bottom-up estimates for 2015–2019 in eastern China was ~23.7 ± 3.6 Gg, which accounts for 47 ± 11 % of the global mismatch. Given the location of HCFC-22 production plants in eastern China and the fraction of regional to global HCFC-22 production capacities, the HFC-23 emissions rise in eastern China is most likely associated with known HCFC-22 production facilities and thus, observed discrepancies between top-down and bottom-up emissions could be attributed to unsuccessful factory level HFC-23 abatement and inaccurate quantification of emission reductions.
Article
Full-text available
Hydrochlorofluorocarbons (HCFCs), the main substitutes of chlorofluorocarbons, are regulated by the Montreal Protocol. Chinese HCFC emissions increased fast from the beginning of this century. However, limit reports based on atmospheric measurement are available for years after 2011, an important period when significant changes are expected. Combining atmospheric observations at seven sites across China with a FLEXible PARTicle dispersion model‐based Bayesian inversion technique, we estimate emission magnitudes and changes of four major HCFCs in China during 2011–2017. The emissions of all four HCFCs reached peaks before 2015. Our results agreed well with the reported bottom‐up inventories. The Chinese ozone depletion potential (ODP)‐weighted emission of the three most abundant HCFCs accounted for 37% of global totals from 2011 to 2016. The total emission of HCFC‐22 from China, the European Union, and the United States accounted approximately a half of the global totals, suggesting large HCFC emission emitted from the rest of the world.
Article
Full-text available
The recovery of the stratospheric ozone layer relies on the continued decline in the atmospheric concentrations of ozone-depleting gases such as chlorofluorocarbons¹. The atmospheric concentration of trichlorofluoromethane (CFC-11), the second-most abundant chlorofluorocarbon, has declined substantially since the mid-1990s². A recently reported slowdown in the decline of the atmospheric concentration of CFC-11 after 2012, however, suggests that global emissions have increased3,4. A concurrent increase in CFC-11 emissions from eastern Asia contributes to the global emission increase, but the location and magnitude of this regional source are unknown³. Here, using high-frequency atmospheric observations from Gosan, South Korea, and Hateruma, Japan, together with global monitoring data and atmospheric chemical transport model simulations, we investigate regional CFC-11 emissions from eastern Asia. We show that emissions from eastern mainland China are 7.0 ± 3.0 (±1 standard deviation) gigagrams per year higher in 2014–2017 than in 2008–2012, and that the increase in emissions arises primarily around the northeastern provinces of Shandong and Hebei. This increase accounts for a substantial fraction (at least 40 to 60 per cent) of the global rise in CFC-11 emissions. We find no evidence for a significant increase in CFC-11 emissions from any other eastern Asian countries or other regions of the world where there are available data for the detection of regional emissions. The attribution of any remaining fraction of the global CFC-11 emission rise to other regions is limited by the sparsity of long-term measurements of sufficient frequency near potentially emissive regions. Several considerations suggest that the increase in CFC-11 emissions from eastern mainland China is likely to be the result of new production and use, which is inconsistent with the Montreal Protocol agreement to phase out global chlorofluorocarbon production by 2010.
Article
Halocarbons are important anthropogenic greenhouse gases (GHGs) due to their long lifetime and large characteristic factors. The present study for the first time assessed the global warming potential (GWP) of fugitive halocarbon emissions from the working face of landfills in China. The national emissions of five major halocarbons (CFC-11, CFC-113, CH2Cl2, CHCl3 and CCl4) from the working face of municipal solid waste landfills in China were provided through observation-based estimations. The fluxes of halocarbons from working face of landfills were observed much higher than covered cells in landfills hence representing the hot spots of landfill emissions. The annual emissions of the halocarbons from landfills in China were 0.02-15.6kt·y(-1), and their GWPs were 128-60,948kt-CO2-eq·y(-1) based on their characteristic factors on a 100-year horizon. CFC-113 was the dominant species owing to its highest releasing rate (i.e. 15.4±19.1g·t(-1)) and largest characteristic factor, resulting in a GWP up to 4036±4855kt-CO2-eq·y(-1). The annual emissions of CFC-113 from landfills (i.e. 0.61kt·y(-1)) made up ∼76% of the total national CFC-113 emissions. The GWPs of halocarbons were estimated ∼14.4% of landfill methane emissions. Therefore, fugitive halocarbons emissions from working face are significant sources of GHGs in landfill sites in China, although they comprise a small fraction of total landfill gases.
Article
SF6 is one of long-lived halogenated greenhouse gases and listed as the restricted emission species in "Kyoto Protocol". Along with the rapid economic development, SF6 emission in China is attracted more attention in the world. For the traditional "bottom-up" method for SF6 emission estimation, the requirements for high accurate and timely updated emission factors and activity data cause many problems for the use of this method. This paper presents the results on the estimation of SF6 emissions in China for the year 2009 by using the Laprange particle dispersion model of FLEXPART, based on the in-situ measurement data obtained from the Shangdianzi regional atomspheric background station (SDZ). The a-posteriori estimations of SF6 emissions in China for the year 2009 is 1.25×103 (0.53×103~1.97×103) t·a-1, which is similar to the results reported by other studies in the literatures. Compared to results with the a-priori emission, the results with the inversion emissions improved with the correlation coefficient increase from 0.37 to 0.43 and the root-mean-square (RMS) decrease by 2.64%.
Article
The high-time-resolution atmospheric mixing ratio data were sampled at Peking University. The data was analyzed and led to the conclusion that HCFC-22 was the proper reference substance; CO, the idiomatic reference, was not suitable for interspecies correlation analysis when dealing with data from urban districts. Based on the observation data of HCFC-142b and HCFC-22 gained from four representative cities (Beijing, Hangzhou, Lanzhou and Guangzhou) in four seasons, China's HCFC-142b emission in 2012 was calculated by interspecies correlation. The result was 16.24 (13.90-18.58) kt, equivalent to 1.06 kt ODP and 37 Tg CO2-eq, taking up 9.78% (ODP) of total HCFCs emission in China or 30.5% of global HCFC-142b emission. Therefore, China's HCFC-142b control would play an important role in phasing out HCFCs domestically and globally.
Article
The inversion method was used to estimate China's HCFC-142b emission by using Lagrangian particle dispersion model FLEXPART combined with the in-situ measurement data obtained from Shangdianzi regional atmospheric background station (SDZ). The Chinese HCFC-142b emissions in 2009 and 2010 were 10.82 kt/a and 15.42 kt/a, accounted for 29.7% and 45.8% of the global emissions, respectively. The spatial distribution of HCFC-142b emission shows high emission rate in Beijing, Tianjin, Sichuan, Shandong and in the middle and lower reaches of the Yangtze River, in consistent with the results by bottom-up method. The correlation coefficients of concentrations simulated from inversion results was higher than those from prior input, increasing from 0.38 to 0.47 in the year of 2009, and from 0.60 to 0.65 in the year of 2010. ©, 2015, Zhongguo Huanjing Kexue/China Environmental Science. All right reserved.
Article
We present in-situ measurements of atmospheric sulfur hexafluoride (SF6) conducted by an automated gas chromatograph-electron capture detector system and a gas chromatography/mass spectrometry system at a regional background site, Shangdianzi, in China, from June 2009 to May 2011, using the System for Observation of Greenhouse gases in Europe and Asia and Advanced Global Atmospheric Gases Experiment (AGAGE) techniques. The mean background and polluted mixing ratios for SF6 during the study period were 7.22×10(-12) (mol/mol, hereinafter) and 8.66×10(-12), respectively. The averaged SF6 background mixing ratios at Shangdianzi were consistent with those obtained at other AGAGE stations located at similar latitudes (Trinidad Head and Mace Head), but larger than AGAGE stations in the Southern Hemisphere (Cape Grim and Cape Matatula). SF6 background mixing ratios increased rapidly during our study period, with a positive growth rate at 0.30×10(-12)year(-1). The peak to peak amplitude of the seasonal cycle for SF6 background conditions was 0.07×10(-12), while the seasonal fluctuation of polluted conditions was 2.16×10(-12). During the study period, peak values of SF6 mixing ratios occurred in autumn when local surface horizontal winds originated from W/WSW/SW/SWS/S sectors, while lower levels of SF6 mixing ratios appeared as winds originated from N/NNE/NE/ENE/E sectors. Copyright © 2014. Published by Elsevier B.V.
Article
Full-text available
Regional ozone pollution has become one of the top environmental concerns in China, especially in those economically vibrant and densely populated regions, such as North China region including Beijing. To address this issue, surface ozone and ancillary data over the period 2004–2006 from the Shangdianzi Regional Background Station in north China were analyzed. Due to the suitable location and valley topography of the site, transport of pollutants from the North China Plain was easily observed and quantified according to surface wind directions. Regional (polluted) and natural (clean) background ozone concentrations were obtained by detailed statistic analysis. Contribution of pollutants from North China Plain to surface ozone at SDZ was estimated by comparing ozone concentrations observed under SW wind conditions and that under NE wind conditions. The average daily accumulated ozone contribution was estimated to be 240 ppb·hr. The average regional contributions to surface ozone at SDZ from the North China Plain were 21.8 ppb for the whole year, and 19.2, 28.9, 25.0, and 10.0 ppb for spring, summer, autumn, and winter, respectively. The strong ozone contribution in summer led to disappearance of the spring ozone maximum phenomenon at SDZ under winds other than from the WNN to E sectors. High winter NOx concentrations in the North China Plain caused negative ozone contribution in winter.
Article
Full-text available
National emission inventories of ozone-depleting substances (ODS) play a key role in the control mechanisms of the Montreal Protocol's emission reduction plans. New quasi-continuous ground-based atmospheric measurements allow us to estimate China's current emissions of the most effective ODS. This serves as an independent validation of China's ODS consumption data reported to the United Nations Environment Programme (UNEP). Emissions of most first-generation ODS have declined in recent years, suggesting compliance with the regulations of China's advanced phase-out program. In contrast the emissions of some second-generation ODS have increased. Because China is currently one of the largest consumers of first generation ODS, the country's upcoming complete phase-out will be crucial for the rate of decline of atmospheric ODS hence the eventual recovery of the stratospheric ozone.
Article
Full-text available
The magnitudes of the ``indirect effects'' that anthropogenic aerosols have on clouds and climate remain uncertain. Past space-based characterizations have compared satellite retrievals of cloud properties with satellite- or model-derived aerosol quantities. The two fields have been taken from air masses displaced from each other either horizontally or vertically. Thus, almost by definition, the cloud retrievals have come from different meteorological regimes than the aerosol to which ostensibly they are related. Because cloud properties depend foremost on meteorology, the difference introduces undesired ambiguity in the comparisons. In this study, we compare Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) cloud retrievals with high spatial and temporal resolution output from a tracer transport model (FLEXPART), enabling colocation of fields of pollution and clouds both vertically and horizontally. Anthropogenic carbon monoxide (CO) is used as a passive pollution tracer, because its concentrations are tied to mixing and pollutant source strength, and they are independent of atmospheric oxidation and removal processes on timescales of weeks to months. Cloud and pollution fields are compared along a downwind axis from the U.S. northeastern seaboard for the duration of the summer 2004 International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) mission. Where the transport model indicates air as being polluted, cloud r e is smaller and cloud optical depth is in some cases higher, at least close to primary source regions. However, within 4 +/- 1 days advection time from the northeastern seaboard, cloud perturbations become negligible, probably because of wet-scavenging of CCN. No conclusive evidence was found for any perturbation to cloud liquid water path by pollution.
Article
Full-text available
1] High‐frequency in‐situ measurements of a wide range of halogenated compounds including chlorofluorocarbons (CFCs), halons, hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), perfluorinated compounds (PFCs), sulfur hexafluoride (SF 6), and other chlorinated and brominated compounds have been made at Gosan (Jeju Island, Korea). Regional emissions of HCFC‐22 (CHClF 2) calculated from inverse modeling were combined with interspecies correlation methods to estimate national emissions for China, a major emitter of industrial halogenated gases. Our results confirm the signs of successful phase‐out of primary ozone‐depleting species such as CFCs, halons and many chlorinated or brominated compounds, along with substantial emissions of replacement HCFCs. Emissions derived for HFCs, PFCs, and SF 6 were compared to published estimates and found to be a significant fraction of global totals. Overall, Chinese emissions of the halogenated compounds discussed here represent 19(14–17)% and 20(15–26)% of global emissions when evaluated in terms of their Ozone Depletion Potentials and 100‐year Global Warming Potentials, respectively. Citation: Kim, J., et al. (2010), Regional atmospheric emissions determined from measure-ments at Jeju Island, Korea: Halogenated compounds from China, Geophys. Res. Lett., 37, L12801, doi:10.1029/2010GL043263.
Article
Full-text available
A new inventory of air pollutant emissions in Asia in the year 2006 is developed to support the Intercontinental Chemical Transport Experiment-Phase B (INTEX-B) funded by the National Aeronautics and Space Administration (NASA). Emissions are estimated for all major anthropogenic sources, excluding biomass burning. We estimate total Asian anthropogenic emissions in the year 2006 as follows: 47.1 Tg SO2, 36.7 Tg NOx, 298.2 Tg CO, 54.6 Tg NMVOC, 29.2 Tg PM10, 22.2 Tg PM2.5, 2.97 Tg BC, and 6.57 Tg OC. We emphasize emissions from China because they dominate the Asia pollutant outflow to the Pacific and the increase of emissions from China since 2000 is of great concern. We have implemented a series of improved methodologies to gain a better understanding of emissions from China, including a detailed technology-based approach, a dynamic methodology representing rapid technology renewal, critical examination of energy statistics, and a new scheme of NMVOC speciation for model-ready emissions. We estimate China's anthropogenic emissions in the year 2006 to be as follows: 31.0 Tg SO2, 20.8 Tg NOx, 166.9 Tg CO, 23.2 Tg NMVOC, 18.2 Tg PM10, 13.3 Tg PM2.5, 1.8 Tg BC, and 3.2 Tg OC. We have also estimated 2001 emissions for China using the same methodology and found that all species show an increasing trend during 2001–2006: 36% increase for SO2, 55% for NOx, 18% for CO, 29% for VOC, 13% for PM10, and 14% for PM2.5, BC, and OC. Emissions are gridded at a resolution of 30 min×30 min and can be accessed at our web site (http://mic.greenresource.cn/intex-b2006).
Article
Full-text available
[1] In this paper we present simulations with a Lagrangian particle dispersion model to study the intercontinental transport of pollution from North America during an aircraft measurement campaign over Europe. The model was used for both the flight planning and a detailed source analysis after the campaign, which is described here with examples from two episodes. Forward calculations of emission tracers from North America, Europe, and Asia were made in order to understand the transport processes. Both episodes were preceded by stagnant conditions over North America, leading to the accumulation of pollutants in the North American boundary layer. Both anthropogenic sources and, to a lesser extent, forest fire emissions contributed to this pollution, which was then exported by warm conveyor belts to the middle and upper troposphere, where it was transported rapidly to Europe. Concentrations of many trace gases (CO, NOy, CO2, acetone, and several volatile organic compounds; O3 in one case) and of ambient atmospheric ions measured aboard the research aircraft were clearly enhanced in the pollution plumes compared to the conditions outside the plumes. Backward simulations with the particle model were introduced as an indispensable tool for a more detailed analysis of the plume's source region. They make trajectory analyses (which, to date, were mainly used to interpret aircraft measurement data) obsolete. Using an emission inventory, we could decompose the tracer mixing ratios at the receptors (i.e., along the flight tracks) into contributions from every grid cell of the inventory. For both plumes we found that emission sources contributing to the tracer concentrations over Europe were distributed over large areas in North America. In one case, sources in California, Texas, and Florida contributed almost equally, and smaller contributions were also made by other sources located between the Yucatan Peninsula and Canada. In the other case, sources in eastern North America, including moderate contributions from forest fires, were most important. The plume's maximum was mainly caused by anthropogenic emissions from the New York area. To our knowledge, this is the first case reported where a pollution plume from a megacity was reliably detected over another continent.
Article
Full-text available
The identification of atmospheric trace species measurements that are representative of well-mixed background air masses is required for monitoring atmospheric composition change at background sites. We present a statistical method based on robust local regression that is well suited for the selection of background measurements and the estimation of associated baseline curves. The bootstrap technique is applied to calculate the uncertainty in the resulting baseline curve. The non-parametric nature of the proposed approach makes it more flexible than other commonly used statistical data filtering methods. Application to carbon monoxide (CO) measured from 1996 to 2009 at the high alpine site Jungfraujoch (Switzerland, 3580 m a.s.l.) demonstrates the feasibility and usefulness of the proposed approach. The determined average annual change for the 1996 to 2009 period as estimated from filtered annual mean CO concentrations is −2.1 ± 1.3 ppb/yr. For comparison, the linear trend of unfiltered CO measurements at Jungfraujoch for this time period is −2.9 ± 1.5 ppb/yr.
Article
Full-text available
During the EU-project Influence of Stratosphere-Troposphere exchange in a Changing Climate on Atmospheric Transport and Oxidation Capacity (STACCATO), a combined approach of a measurement network and numerical simulations was used to estimate the strength and frequency of stratosphere-to-troposphere transport (STT) events and their influence on tropospheric chemistry. Measurements of surface ozone, beryllium-7, and beryllium-10 concentrations and meteorological parameters at four European high mountain stations, as well as atmospheric profiles obtained by ozone soundings and a high-resolution lidar, were carried out. In order to simulate STT events, seven different models have been applied by the STACCATO partners. These are two trajectory models (LAGRANTO and FLEXTRA), a Lagrangian transport model (FLEXPART), a Lagrangian chemistry-transport model (STOCHEM), a Eulerian transport model (TM3), and two general circulation models (ECHAM4 and MA-ECHAM4). In order to investigate the strengths and weaknesses of each of these models and to identify the reasons for their discrepancies, a detailed comparison with measured data is presented in this paper. These models provided fluxes and concentrations of a stratospheric tracer, as well as the vertical profiles of ozone and radionuclides for a stratospheric intrusion case study that occurred over Europe in the year 1996. The comparison of the model results with the measurement data and the satellite observations revealed that all the models captured the general behavior of the event. However, great differences were found in the intensity and spatial development of the simulated intrusion event.
Article
Full-text available
The emissions of three hydrochlorofluorocarbons, HCFC-22 (CHClF2), HCFC-141b (CH3CCl2F) and HCFC-142b (CH3CClF2) and three hydrofluorocarbons, HFC-23 (CHF3), HFC-134a (CH2FCF3) and HFC-152a (CH3CHF2) from five East Asian countries for the year 2008 are determined by inverse modeling. The inverse modeling is based on in-situ measurements of these halocarbons at the Japanese stations Cape Ochi-ishi and Hateruma, the Chinese station Shangdianzi and the South Korean station Gosan. For every station and every 3 h, 20-day backward calculations were made with the Lagrangian particle dispersion model FLEXPART. The model output, the measurement data, bottom-up emission information and corresponding uncertainties were fed into an inversion algorithm to determine the regional emission fluxes. The model captures the observed variation of halocarbon mixing ratios very well for the two Japanese stations but has difficulties explaining the large observed variability at Shangdianzi, which is partly caused by small-scale transport from Beijing that is not adequately captured by the model. Based on HFC-23 measurements, the inversion algorithm could successfully identify the locations of factories known to produce HCFC-22 and emit HFC-23 as an unintentional byproduct. This lends substantial credibility to the inversion method. We report national emissions for China, North Korea, South Korea and Japan, as well as emissions for the Taiwan region. Halocarbon emissions in China are much larger than the emissions in the other countries together and contribute a substantial fraction to the global emissions. Our estimates of Chinese emissions for the year 2008 are 65.3±6.6 kt/yr for HCFC-22 (17% of global emissions extrapolated from Montzka et al., 2009), 12.1±1.6 kt/yr for HCFC-141b (22%), 7.3±0.7 kt/yr for HCFC-142b (17%), 6.2±0.7 kt/yr for HFC-23 (>50%), 12.9±1.7 kt/yr for HFC-134a (9% of global emissions estimated from Velders et al., 2009) and 3.4±0.5 kt/yr for HFC-152a (7%).
Article
Full-text available
The possibility to calculate linear-source receptor relationships for the transport of atmospheric trace substances with a Lagrangian particle dispersion model (LPDM) running in backward mode is shown and presented with many tests and examples. This mode requires only minor modifications of the forward LPDM. The derivation includes the action of sources and of any first-order processes (transformation with prescribed rates, dry and wet deposition, radioactive decay, etc.). The backward mode is computationally advantageous if the number of receptors is less than the number of sources considered. The combination of an LPDM with the backward (adjoint) methodology is especially attractive for the application to point measurements, which can be handled without artificial numerical diffusion. Practical hints are provided for source-receptor calculations with different settings, both in forward and backward mode. The equivalence of forward and backward calculations is shown in simple tests for release and sampling of particles, pure wet deposition, pure convective redistribution and realistic transport over a short distance. Furthermore, an application example explaining measurements of Cs-137 in Stockholm as transport from areas contaminated heavily in the Chernobyl disaster is included.
Article
Full-text available
A new analytical inversion method has been developed to determine the regional and global emissions of long-lived atmospheric trace gases. It exploits in situ measurement data from three global networks and builds on backward simulations with a Lagrangian particle dispersion model. The emission information is extracted from the observed concentration increases over a baseline that is itself objectively determined by the inversion algorithm. The method was applied to two hydrofluorocarbons (HFC-134a, HFC-152a) and a hydrochlorofluorocarbon (HCFC-22) for the period January 2005 until March 2007. Detailed sensitivity studies with synthetic as well as with real measurement data were done to quantify the influence on the results of the a priori emissions and their uncertainties as well as of the observation and model errors. It was found that the global a posteriori emissions of HFC-134a, HFC-152a and HCFC-22 all increased from 2005 to 2006. Large increases (21%, 16%, 18%, respectively) from 2005 to 2006 were found for China, whereas the emission changes in North America (−9%, 23%, 17%, respectively) and Europe (11%, 11%, −4%, respectively) were mostly smaller and less systematic. For Europe, the a posteriori emissions of HFC-134a and HFC-152a were slightly higher than the a priori emissions reported to the United Nations Framework Convention on Climate Change (UNFCCC). For HCFC-22, the a posteriori emissions for Europe were substantially (by almost a factor 2) higher than the a priori emissions used, which were based on HCFC consumption data reported to the United Nations Environment Programme (UNEP). Combined with the reported strongly decreasing HCFC consumption in Europe, this suggests a substantial time lag between the reported time of the HCFC-22 consumption and the actual time of the HCFC-22 emission. Conversely, in China where HCFC consumption is increasing rapidly according to the UNEP data, the a posteriori emissions are only about 40% of the a priori emissions. This reveals a substantial storage of HCFC-22 and potential for future emissions in China. Deficiencies in the geographical distribution of stations measuring halocarbons in relation to estimating regional emissions are also discussed in the paper. Applications of the inversion algorithm to other greenhouse gases such as methane, nitrous oxide or carbon dioxide are foreseen for the future.
Article
Full-text available
Regional ozone pollution has become one of the top environmental concerns in China, especially in those economically vibrant and densely populated regions, such as North China region including Beijing. To address this issue, surface ozone and ancillary data over the period 2004–2006 from the Shangdianzi Regional Background Station in north China were analyzed. Due to the suitable location and valley topography of the site, transport of pollutants from the North China Plain was easily observed and quantified according to surface wind directions. Regional (polluted) and background (clean) ozone concentrations were obtained by detailed statistic analysis. Contribution of pollutants from North China Plain to surface ozone at SDZ was estimated by comparing ozone concentrations observed under SW wind conditions and that under NE wind conditions. The average daily accumulated ozone contribution was estimated to be 240 ppb·hr. The average regional contributions to surface ozone at SDZ from the North China Plain were 21.8 ppb for the whole year, and 19.2, 28.9, 25.0, and 10.0 ppb for spring, summer, autumn, and winter, respectively. The strong ozone contribution in summer led to disappearance of the spring ozone maximum phenomenon at SDZ under winds other than from the NNW to E sectors. The emissions of nitrogen oxide in the North China plain cause a decrease in ozone concentrations in winter.
Article
Full-text available
The Lagrangian particle dispersion model FLEXPART was originally (about 8 years ago) designed for calculating the long-range and mesoscale dispersion of air pollutants from point sources, such as after an accident in a nuclear power plant. In the meantime FLEXPART has evolved into a comprehensive tool for atmospheric transport modeling and analysis. Its application fields were extended from air pollution studies to other topics where atmospheric transport plays a role (e.g., exchange between the stratosphere and troposphere, or the global water cycle). It has evolved into a true community model that is now being used by at least 25 groups from 14 different countries and is seeing both operational and research applications. A user manual has been kept actual over the years and was distributed over an internet page along with the model's source code. In this note we provide a citeable technical description of FLEXPART's latest version (6.2).
Article
Tropospheric accumulation rates of the three most abundant hydrochlorofluorocarbons (HCFCs) were up to two times faster during 2007 than measured in 2003–2004. Tropospheric chlorine from HCFCs increased at 10 pptCl/yr during 2006–2007, up from 6 pptCl/yr in 2003–2004, and offset declines in chlorine from other anthropogenic ozone-depleting substances in 2007 by approximately one-third. Derived global emissions for HCFCs increased by up to 60% since 2004, and, for HCFC-142b, emissions during 2007 were two times larger than projected recently. Measured tropospheric distributions suggest a shift in HCFC emissions to lower latitudes of the Northern Hemisphere. These changes coincide with exponential increases in developing country production and consumption and decreases in other countries. When weighted by direct, 100-yr global warming potentials, HCFC emissions in 2007 amounted to 0.78 GtCO2-equivalents, or 30% larger than the average during 2000–2004, and were approximately 2.6% of fossil-fuel and cement related CO2 emissions.
Article
A new method of trajectory statistics was developed which allows the identification of source areas with higher spatial resolution than other methods. It uses ambient air pollutant concentration measurements at a receptor site and corresponding back trajectories arriving at that site. In a first step, each pollutant concentration is attributed to its trajectory. From this, a first guess “concentration field” is computed which shows potential source areas of the respective pollutant. In an iterative procedure, the concentrations are redistributed along their corresponding trajectories which continuously improves the “concentration field”. The new method was tested with a large set of back trajectories ending at 14 measurement sites of the EMEP network. It was used to identify potential source areas of particulate sulfate. The procedure successfully identified many source areas with a much higher resolution than what would have been achievable with existing methods. The locations of the source areas were compared with the locations of the emission maxima of an emission inventory and a good agreement was found, both qualitatively and quantitatively.
Article
[1] High frequency monitoring of hydrofluorocarbons (HFCs) and some other halocarbons in the atmosphere has been performed at Hateruma Island (lat. 24.1°N, long. 123.8°E), a background site in east Asia. The observed concentrations showed occasional short-term enhancement events over hours to days as well as a clear seasonal variation, being lower in summer than in other seasons. We found that HFC-23 enhancements were closely related to the air transport from China. Using a tagged simulation from three-dimensional transport model and a tracer-ratio technique, the emission rate of HFC-23 from China was estimated to amount to 10 Gg (= 10 000 metric tonnes) per year with an uncertainty of 50%, which could account for two thirds of the total global emission. HFCs emitted from Japan, Korea, and Taiwan were characterized by a predominance of HFC-134a with very little contribution of HFC-23.
Article
The burden of ozone-depleting chemicals in the lower atmosphere has been decreasing since 1994 as a result of the Montreal Protocol. Here we show how individual chemicals have influenced this decline, in order to estimate how the burden could change in the near future. Our measurements of atmospheric concentrations of the persistent, anthropogenic chemicals that account for most ozone-depleting halogens in today's stratosphere show that the decline stems predominantly from the decrease in the atmospheric load of trichloroethane (CH3CCl3), a previously common cleaning solvent. The influence of this chemical on the decline has now peaked, however, and will become much smaller over the next five to ten years. As this influence lessens, a decrease in the burden of ozone-depleting halogen will be sustained only if emissions of other halocarbons fall. Although emissions of most gases regulated by the Montreal Protocol have decreased substantially over the past ten years (refs 4-11), emissions of the potent ozone-depleting gas CBrClF2 (halon-1211) have remained fairly constant during this period, despite stringent limits on production in developed countries since 1994. The consequent atmospheric accumulation of this halon is retarding the decline of ozone-depleting halogens in the atmosphere more than any other persistent gas.
Article
We describe an episode of a stratospheric intrusion into the free troposphere over Europe followed by a long-range transport of ozone from the North American boundary layer. Observational data showed the presence of a thin tongue of stratospheric air in the free troposphere for at least 36 hours. This filament was found in data from two ozone soundings and was recorded continuously for 26 hours by a high-resolution ozone lidar. The stratospheric air also intercepted two high Alpine summits, causing elevated ozone and beryllium 7 concentrations. Trajectory, particle dispersion model, and potential vorticity analyses confirmed the stratospheric nature of the tongue. In the lidar data, following the intrusion, pockets of elevated ozone concentrations (80 –100 ppb) were found in the free troposphere close to the tropopause. The low potential vorticity values and high water vapor content in these ozone-rich pockets and trajectory analyses suggest that the ozone was photochemically produced in the boundary layer over eastern North America, followed by rapid uplifting in a warm conveyor belt over the Atlantic Ocean ahead of a frontal system. This was confirmed by ozone and water vapor measurements aboard commercial airliners crossing the warm conveyor belt. The air mass trajectories in both the stratospheric intrusion and the warm conveyor belt were tightly bundled, emphasizing the importance of the coherency of airstreams for long-range ozone transport.
Article
The halocarbons studied here are chemicals controlled in the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer and its Amendments, which have both high ozone depleting potentials (ODPs) and high global warming potentials (GWPs). These halocarbons are mainly used for refrigeration, air-conditioning, foam blowing, tobacco expansion, aerosol propulsion, solvent cleaning, and fire fighting. China ratified the Montreal Protocol in 1991 and has been implementing the phase-out of halocarbons since then. In this paper, the emissions of halocarbons from China were estimated for 1995–2024 based on the historical consumption, the country program for complying with the Montreal Protocol, and the sector plans for phasing out halocarbons. The results show that China's compliance with the Montreal Protocol contributes greatly to both ozone protection and climate protection.
Article
In-situ measurements of atmospheric chlorofluorocarbons (CFCs) can be used to the assess their global and regional emissions and to check for compliance with phase-out schedules under Montreal protocol and its amendments. The atmospheric mixing ratios of CFC-11 (CCl3F), CFC-12 (CCl2F2) and CFC-113 (CCl2F–CClF2) have been measured by an automated in-situ GC-ECDs system at the regional Chinese Global Atmosphere Watch (GAW) station Shangdianzi (SDZ), from November 2006 to October 2009. The time series for these three principal CFCs showed large episodic events and background conditions occurred for approximately 30% (CFC-11), 52% (CFC-12) and 56% (CFC-113) of the measurements. The mean background mixing ratios for CFC-11, CFC-12 and CFC-113 were 244.8 ppt (parts per trillion, 10−12, molar) 539.6 ppt and 76.8 ppt, respectively, for 2006–2009. The enhanced CFC mixing ratios compared to AGAGE sites such as Trinidad Head (THD), US and Mace Head (MHD), Ireland suggest regional influences even during background conditions at SDZ, which is much closer to highly-populated areas. Between 2006 and 2009 background CFCs exhibited downward trends at rates of −2.0 ppt yr−1 for CFC-11, −2.5 ppt yr−1 for CFC-12 and −0.7 ppt yr−1 for CFC-113. De-trended 3-year average background seasonal cycles displayed small fluctuations with peak-to-trough amplitudes of 1.0 ± 0.02 ppt (0.4%) for background CFC-11, 1.3 ± 2.1 ppt (0.3%) for CFC-12 and 0.2 ± 0.4 ppt (0.3%) for CFC-113. On the other hand, during pollution periods these CFCs showed much larger seasonal cycles of 11.2 ± 10.7 ppt (5%) for CFC-11, 7.5 ± 6.5 ppt (2%) for CFC-12 and 1.0 ± 1.2 ppt (1.2%) for CFC-113, with apparent winter minima and early summer maxima. This enhancement was attributed to prevailing wind directions from urban regions in summer and to enhanced anthropogenic sources during the warm season. In general, horizontal winds from northeast showed negative contribution to atmospheric CFCs loading, whereas South Western advection (urban sector: Beijing) had positive contributions.
Article
A comprehensive validation of FLEXPART, a recently developed Lagrangian particle dispersion model based on meteorological data from the European Centre for Medium-Range Weather Forecasts, is described in this paper. Measurement data from three large-scale tracer experiments, the Cross-Appalachian Tracer Experiment (CAPTEX), the Across North America Tracer Experiment (ANATEX) and the European Tracer Experiment (ETEX) are used for this purpose. The evaluation is based entirely on comparisons of model results and measurements paired in space and time. It is found that some of the statistical parameters often used for model validation are extremely sensitive to small measurement errors and should not be used in future studies. 40 cases of tracer dispersion are studied, allowing a validation of the model performance under a variety of different meteorological conditions. The model usually performs very well under undisturbed meteorological conditions, but it is less skilful in the presence of fronts. The two ETEX cases reveal the full range of the model’s skill, with the first one being among the best cases studied, and the second one being, by far, the worst. The model performance in terms of the statistical parameters used stays rather constant with time over the periods (up to 117 h) studied here. It is shown that the method used to estimate the concentrations at the receptor locations has a significant effect on the evaluation results. The vertical wind component sometimes has a large influence on the model results, but on the average only a slight improvement over simulations which neglect the vertical wind can be demonstrated. Subgrid variability of mixing heights is important and must be accounted for.
Article
High-frequency in situ measurements at Gosan (Jeju Island, Korea) during November 2007 to December 2008 have been combined with interspecies correlation analysis to estimate national emissions of halogenated compounds (HCs) in East Asia, including the chlorofluorocarbons (CFCs), halons, hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF(6)), and other chlorinated and brominated compounds. Our results suggest that overall China is the dominant emitter of HCs in East Asia, however significant emissions are also found in South Korea, Japan and Taiwan for HFC-134a, HFC-143a, C(2)F(6), SF(6), CH(3)CCl(3), and HFC-365mfc. The combined emissions of CFCs, halon-1211, HCFCs, HFCs, PFCs, and SF(6) from all four countries in 2008 are 25.3, 1.6, 135, 42.6, 3.6, and 2.0 kt/a, respectively. They account for approximately 15%, 26%, 29%, 16%, 32%, and 26.5% of global emissions, respectively. Our results show signs that Japan has successfully phased out CFCs and HCFCs in compliance with the Montreal Protocol (MP), Korea has started transitioning from HCFCs to HFCs, while China still significantly consumes HCFCs. Taiwan, while not directly regulated under the MP, is shown to have adapted the use of HFCs. Combined analysis of emission rates and the interspecies correlation matrix presented in this study proves to be a powerful tool for monitoring and diagnosing changes in consumption of HCs in East Asia.
Article
The earth's radiation budget is sensitive to both the macrophysical and microphysical properties of clouds. Anthropogenic aerosols act as cloud condensation nuclei (CCN), and can alter these cloud properties. The effect on the climate system may be significant. In this thesis, the "indirect effects" of pollution aerosol on clouds and climate are characterized using Terra and Aqua MODIS cloud retrievals, and high spatial and temporal output from a tracer transport model (FLEXPART). Cloud properties are colocated both vertically and horizontally with anthropogenic carbon monoxide (CO). CO is considered a passive pollution tracer because its concentrations are tied to mixing and pollutant source strength, and are independent of atmospheric oxidation and removal processes in the model. The use of a passive tracer allows for strict analysis of the sensitivity of cloud properties to pollution and excludes any feedbacks associated with sensitivities of pollution to clouds. Clouds and pollution fields are collected into four adjacent 4° x 4° latitude-longitude boxes over the western Atlantic Ocean, aligned along a downwind axis from the U.S. northeastern seaboard during the summer 2004 International Consortium for Atmospheric Research and Transformation (ICARTT) mission. The alignment of the 4° x 4° boxes allows for an analysis of the magnitude of the "indirect effect" as a function of transport distance and pollution age. Aircraft data from within the box closest to land indicate that measured CO perturbations correspond with lower values cloud droplet effective radii re, and higher droplet number concentrations N. Satellite data show that the mean values of retrieved re are smaller under modeled polluted conditions. In some cases, values of cloud optical thickness rc are larger under polluted air, while there is little to no statistically significant change in cloud liquid water path LWP A preliminary analysis of cloud cover shows no significant changes in fractional cloudiness under polluted conditions for the ICARTT timeframe. The potential for modeled CO plumes to correspond to smaller re and larger xc diminishes with transport distance, and suggests a cloud condensation nuclei (CCN) lifetime under wet scavenging of approximately 4 ± 1 days. Master of Science;
Evaluation of the aerosol indirect effect using satellite, tracer transport model, and aircraft data from the In-ternational Consortium for Atmospheric Research on Transport and Transformation Technical Note: The Lagrangian particle dispersion model FLEXPART version 6.2
  • L Avey
  • T J Garrett
  • Stohl
  • A Stohl
  • C Forster
  • A Frank
  • A Stohl
  • C Forster
  • A Frank
  • A Seibert
  • Wotawa
Avey L, Garrett T J, Stohl A. Evaluation of the aerosol indirect effect using satellite, tracer transport model, and aircraft data from the In-ternational Consortium for Atmospheric Research on Transport and Transformation. J Geophys Res, 2007, 12: D10S33 21 Stohl A, Forster C, Frank A, Stohl A, Forster C, Frank A, Seibert A, Wotawa G. Technical Note: The Lagrangian particle dispersion model FLEXPART version 6.2. Atmos Chem Phys, 2005, 5: 2461–2474
Emissions of ozone-depleting halocarbons from Chi-na Regional atmospheric emissions determined from measurements at Jeju Island, Korea: Halogenated compounds from China
  • F Stordal
  • Dm Cunnold
  • Zhang Xc
  • M Maione
  • F Zhang
  • Simmonds J Huang
  • Kim J Pg
  • Kim Kr A Stohl
  • J Muhle
  • Kim
  • Sk
  • Mk Park
  • Kang
  • Dj
  • G Lee
  • Harth Cm
  • Pk Salameh
  • Li S Weiss Rf
  • Kim J Kim
  • Kr
Stordal F, Cunnold DM, Zhang XC, Maione M, Zhang F, Huang J, Simmonds PG. Emissions of ozone-depleting halocarbons from Chi-na. Geophys Res Lett, 2009, 36: L15823 10 Kim J, Li S, Kim KR, Stohl A, Muhle J, Kim SK, Park MK, Kang DJ, Lee G, Harth CM, Salameh PK, Weiss RF. Regional atmospheric emissions determined from measurements at Jeju Island, Korea: Halogenated compounds from China. Geophy Res Lett, 2010, 37: L12801 11 Li S, Kim J, Kim KR. Emissions of Halogenated compounds in East asia determined from measurements at Jeju island, Korea. Environ Sci Technol, 2011, 45: 5668–5675
Online observation of 12 halogenated greenhouse gases with the method of gas chromatography with electron capture detector (GC ECD) Environmen Chem
  • B Yao
  • L Zhou
  • F Zhang
  • X Zhang
  • L Xu
Asian emissions in 2006 for the NASA INTEX-B mission
  • Q Zhang
  • D G Streets
  • G R Carmichael
  • K He
  • H Huo
  • A Kannari
  • Z Klimont
  • I Park
  • S Reddy
  • D Chen
  • L Duan
  • Y Lei
  • L Wang
  • Z Yao
  • Q. Zhang
  • A. Stohl
Hydrochlorofluorocarbon and hydrofluorocarbon emissions in East Asia determined by inverse modeling
  • A Stohl
  • J Kim
  • S Li
  • O Doherty
  • S Mühle
  • J Salameh
  • P K Saito
  • T Vollmer
  • M K Wan
  • D Weiss
  • R F Yao
  • B Yokouchi
  • Y Zhou
  • A. Stohl
Online observation of 12 halogenated greenhouse gases with the method of gas chromatography with electron capture detector (GC ECD)
  • B Yao
  • L Zhou
  • F Zhang
  • X Zhang
  • L Xu
  • B. Yao