Contribution of very short-lived organic substances to stratospheric chlorine and bromine in the tropics – a case study

Laube, Johannes C.; Engel, Andreas; Bönisch, Harald; Möbius, T.; Worton, David R.; Sturges, William T.; Grunow, K.; Schmidt, Ulrich

doi:10.5194/acp-8-7325-2008

Cited by 98 publications

(118 citation statements)

References 29 publications

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“…Wamsley et al (1994) reported CH 2 Br 2 to have an atmospheric lifetime long enough to reach the stratosphere and CHBr 3 (with shorter lifetime) to contribute negligible amounts to stratospheric Br. The results here are also consistent with Laube et al (2008) who, based on observations, deduced CH 2 Br 2 to be the "dominant" very short-lived SG. Their results, along with Schauffler et al (1998), find CH 2 Br 2 to be present up to ∼18.5 km (∼0.15 pptv).…”

Section: Source Gas Injectionsupporting

confidence: 92%

Bromoform and dibromomethane in the tropics: a 3-D model study of chemistry and transport

et al. 2010

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Abstract.We have developed a detailed chemical scheme for the degradation of the short-lived source gases bromoform (CHBr 3 ) and dibromomethane (CH 2 Br 2 ) and implemented it in the TOMCAT/SLIMCAT three-dimensional (3-D) chemical transport model (CTM). The CTM has been used to predict the distribution of the two source gases (SGs) and 11 of their organic product gases (PGs). These first global calculations of the organic PGs show that their abundance is small. The longest lived organic PGs are CBr 2 O and CHBrO, but their peak tropospheric abundance relative to the surface volume mixing ratio (vmr) of the SGs is less than 5%. We calculate their mean local tropospheric lifetimes in the tropics to be ∼7 and ∼2 days (due to photolysis), respectively. Therefore, the assumption in previous modelling studies that SG degradation leads immediately to inorganic bromine seems reasonable.We have compared observed tropical SG profiles from a number of aircraft campaigns with various model experiments. In the tropical tropopause layer (TTL) we find that the CTM run using p levels (TOMCAT) and vertical winds from analysed divergence overestimates the abundance of CH 2 Br 2 , and to a lesser extent CHBr 3 , although the data is sparse and comparisons are not conclusive. Better agreement in the TTL is obtained in the sensitivity run using θ levels (SLIMCAT) and vertical motion from diabatic heating rates. Trajectory estimates of residence times in the two model versions show slower vertical transport in the SLIM-CAT θ-level version. In the p-level model even when we switch off convection we still find significant amounts of the SGs considered may reach the cold point tropopause; the Correspondence to: R. Hossaini (chm3rh@leeds.ac.uk) stratospheric source gas injection (SGI) is only reduced by ∼16% for CHBr 3 and ∼2% for CH 2 Br 2 without convection.Overall, the relative importance of the SG pathway and the PG pathway for transport of bromine to the stratospheric overworld (θ >380 K) has been assessed. Assuming a 10-day washout lifetime of Br y in TOMCAT, we find the delivery of total Br from CHBr 3 to be 0.72 pptv with ∼53% of this coming from SGI. Similary, for CH 2 Br 2 we find a total Br value of 1.69 pptv with ∼94% coming from SGI. We infer that these species contribute ∼2.4 pptv of inorganic bromine to the lower stratosphere with SGI being the dominant pathway. Slower transport to and through the TTL would decrease this estimate.

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Section: Source Gas Injectionsupporting

confidence: 92%

Bromoform and dibromomethane in the tropics: a 3-D model study of chemistry and transport

et al. 2010

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“…During a former balloon flight in June 2005 in Teresina the VSLS mixing ratios (analysed for an air sample at 15.2 km) were considerably lower than those analysed in 2008 at nearly the same altitude (Laube et al, 2008). The total Br org from VSLS was 1.25 ppt, while especially the CHBr 3 contribution was unexpectedly low, with only 0.05 ppt Br org .…”

Section: Comparison and Discussionmentioning

confidence: 78%

“…5.1 we determined total uncertainties of the analysed mixing ratios. This calculation was done similar to the procedure described by Laube et al (2008). Statistical errors during the measurements and the systematic error of the calibration scale of the primary standard gas are considered.…”

Section: Scale Uncertaintiesmentioning

confidence: 99%

“…Very few measurements of these species in the entrance region to the stratosphere have been published to date (e.g. Schauffler et al, 1999;Laube et al, 2008;Liang et al, 2010). Based on organic bromine source gas data in the tropical tropopause layer (TTL) and the results from modeling studies concerning the transport of these gases and their degradation products into the stratosphere, Montzka et al (2011) have determined that brominated VSLS contribute between 1 and 8 ppt to stratospheric inorganic bromine (Br y ).…”

Section: Introductionmentioning

confidence: 99%

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Short-lived brominated hydrocarbons – observations in the source regions and the tropical tropopause layer

et al. 2012

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Abstract. We conducted measurements of the five important short-lived organic bromine species in the marine boundary layer (MBL). Measurements were made in the Northern Hemisphere mid-latitudes (Sylt Island, North Sea) in June 2009 and in the tropical Western Pacific during the TransBrom ship campaign in October 2009. For the one-week time series on Sylt Island, mean mixing ratios of CHBr 3 , CH 2 Br 2 , CHBr 2 Cl and CH 2 BrCl were 2.0, 1.1, 0.2, 0.1 ppt, respectively. We found maxima of 5.8 and 1.6 ppt for the two main components CHBr 3 and CH 2 Br 2 . Along the cruise track in the Western Pacific (between 41 • N and 13 • S) we measured mean mixing ratios of 0.9, 0.9, 0.2, 0.1 and 0.1 ppt for CHBr 3 , CH 2 Br 2 , CHBrCl 2 , CHBr 2 Cl and CH 2 BrCl. Air samples with coastal influence showed considerably higher mixing ratios than the samples with open ocean origin. Correlation analyses of the two data sets yielded strong linear relationships between the mixing ratios of four of the five species (except for CH 2 BrCl). Using a combined data set from the two campaigns and a comparison with the results from two former studies, rough estimates of the molar emission ratios between the correlated substances were: 9/1/0.35/0.35 for CHBr 3 /CH 2 Br 2 /CHBrCl 2 /CHBr 2 Cl. Additional measurements were made in the tropical tropopause layer (TTL) above Teresina (Brazil, 5 • S) in June 2008, using balloon-borne cryogenic whole air sampling technique. Near the level of zero clear-sky net radiative heating (LZRH) at 14.8 km about 2.25 ppt organic bromine was bound to the five short-lived species, making up 13 % of total organic bromine (17.82 ppt). CH 2 Br 2 (1.45 ppt) and CHBr 3 (0.56 ppt) accounted for 90 % of the budget of short-lived compounds in that region. Near the tropopause (at 17.5 km) organic bromine from these substances was reduced to 1.35 ppt, with 1.07 and 0.12 ppt attributed to CH 2 Br 2 and CHBr 3 , respectively.

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“…After the flight, the collected samples are analyzed on the abundance of a long list of trace gases by means of gas chromatography. In this comparison we consider five balloon flights that were performed by the University of Frankfurt (Germany) (e.g., Laube et al, 2008).…”

Section: Cryosampler Datamentioning

confidence: 99%

MIPAS IMK/IAA CFC-11 (CCl₃F) and CFC-12 (CCl₂F₂) measurements: accuracy, precision and long-term stability

et al. 2016

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) and were used to validate MIPAS CFC-11 and CFC-12 products during that time, as well as profiles from the Improved Limb Atmospheric Spectrometer, ILAS-II. In general, we find that MIPAS shows slightly higher values for CFC-11 at the lower end of the profiles (below ∼ 15 km) and in a comparison of HATS ground-based data and MIPAS measurements at 3 km below the tropopause. Differences range from approximately 10 to 50 pptv (∼ 5-20 %) during the RR period. In general, differences are slightly smaller for the FR period. An indication of a slight high bias at the lower end of the profile exists for CFC-12 as well, but this bias is far less pronounced than for CFC-11 and is not as obvious in the relative differences between MIPAS and any of the comparison instruments. Differences at the lower end of the profile (below ∼ 15 km) and in the comparison of HATS and MIPAS measurements taken at 3 km below the tropopause mainly stay within 10-50 pptv (corresponding to ∼ 2-10 % for CFCPublished by Copernicus Publications on behalf of the European Geosciences Union. 3356 E. Eckert et al.: MIPAS IMK/IAA CFC-11 and CFC-12: accuracy, precision and long-term stability 12) for the RR and the FR period. Between ∼ 15 and 30 km, most comparisons agree within 10-20 pptv (10-20 %), apart from ILAS-II, which shows large differences above ∼ 17 km. Overall, relative differences are usually smaller for CFC-12 than for CFC-11. For both species -CFC-11 and CFC-12 -we find that differences at the lower end of the profile tend to be larger at higher latitudes than in tropical and subtropical regions. In addition, MIPAS profiles have a maximum in their mixing ratio around the tropopause, which is most obvious in tropical mean profiles. Comparisons of the standard deviation in a quiescent atmosphere (polar summer) show that only the CFC-12 FR error budget can fully explain the observed variability, while for the other products (CFC-11 FR and RR and CFC-12 RR) only two-thirds to three-quarters can be explained. Investigations regarding the temporal stability show very small negative drifts in MIPAS CFC-11 measurements. These instrument drifts vary between ∼ 1 and 3 % decade −1 . For CFC-12, the drifts are also negative and close to zero up to ∼ 30 km. Above that altitude, larger drifts of up to ∼ 50 % decade −1 appear which are negative up to ∼ 35 km and positive, but of a similar magnitude, above.

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Contribution of very short-lived organic substances to stratospheric chlorine and bromine in the tropics – a case study

Cited by 98 publications

References 29 publications

Bromoform and dibromomethane in the tropics: a 3-D model study of chemistry and transport

Bromoform and dibromomethane in the tropics: a 3-D model study of chemistry and transport

Short-lived brominated hydrocarbons – observations in the source regions and the tropical tropopause layer

MIPAS IMK/IAA CFC-11 (CCl₃F) and CFC-12 (CCl₂F₂) measurements: accuracy, precision and long-term stability

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Contribution of very short-lived organic substances to stratospheric chlorine and bromine in the tropics – a case study

Cited by 98 publications

References 29 publications

Bromoform and dibromomethane in the tropics: a 3-D model study of chemistry and transport

Bromoform and dibromomethane in the tropics: a 3-D model study of chemistry and transport

Short-lived brominated hydrocarbons – observations in the source regions and the tropical tropopause layer

MIPAS IMK/IAA CFC-11 (CCl3F) and CFC-12 (CCl2F2) measurements: accuracy, precision and long-term stability

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MIPAS IMK/IAA CFC-11 (CCl₃F) and CFC-12 (CCl₂F₂) measurements: accuracy, precision and long-term stability