Bromoform in tropical Atlantic air from 25°N to 25°S

Carpenter, Lucy J.; Wevill, David; Hopkins, James R.; Dunk, Rachel M.; Jones, C. E.; Hornsby, K. E.; McQuaid, James B.

doi:10.1029/2007gl029893

Cited by 32 publications

(31 citation statements)

References 23 publications

(36 reference statements)

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“…For example, a study by Carpenter et al (2007) measured CHBr 3 concentrations over the eastern Atlantic Ocean between 25 • N and 25 • S, ranging from a minimum of 0.2 ppt to a maximum of 13.3 ppt at 9.5 • N. Similar maximum mixing ratios of CHBr 3 over the tropical northern Atlantic Ocean were observed by Class and Ballschmiter (1988) (14 ppt) and Quack et al (2004) (25 ppt). In the eastern Atlantic Ocean, the bioactive Mauritanian upwelling has been suggested as an important source of reactive organic bromine (Quack et al, 2007a;Carpenter et al, 2007), though ship-borne measurements taken in May/June 2007 found no instances of high atmospheric CH 2 Br 2 or CHBr 3 concentrations (Carpenter et al, 2009). Quack et al (2007b) found that their atmospheric measurements over the tropical North Atlantic Ocean could not be explained solely by emissions from the Mauritanian upwelling and suggested that a West African continental source was necessary.…”

Section: Introductionsupporting

confidence: 59%

“…where observed fluxes of CHBr 3 are more than twice the values in MON at around 30-40 nmol m −2 day −1 (Quack et al, 2007a;Carpenter et al, 2007). However, an extra experiment performed using a CHBr 3 flux of 40 nmol m −2 day −1 over the upwelling region (16-20 • W, 14-20 • N) still does not reproduce the measured high concentrations at Cape Verde.…”

Section: Comparison Of Measured and Modelled Bromocarbon Concentrationsmentioning

confidence: 71%

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Bromocarbons in the tropical marine boundary layer at the Cape Verde Observatory – measurements and modelling

et al. 2009

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Abstract. A new gas chromatograph was used to make measurements of halocarbons at the Cape Verde observatory during late May and early June 2007. The instrument demonstrated its potential for long-term autonomous measurements. Bromoform (CHBr 3 ) exhibits the most variability of all the halocarbons observed, ranging from a background concentration of about 4 ppt to a maximum of >40 ppt during the course of the measurement period. CH 2 Br 2 correlates well with bromoform, suggesting a common regional source. Methyl iodide does not correlate with these bromocarbons, with base levels of around 1-2 ppt and some periods of much higher mixing ratios. Using published bromocarbon emission rates, our chemical transport model studies, presented here, do not reproduce the observations. Local emission magnitudes and CHBr 3 :CH 2 Br 2 ratios must be increased more in line with the recent observations of Yokouchi et al. (2005) to improve the model to measurement comparison. Even when the model reproduces the observed bromocarbons, modelled BrO is much less than recent tropical observations (Read et al., 2008). A sea salt source seems the likely explanation. When high BrO is reproduced, the model agrees much better with the observed ozone changes, including diurnal variation, during the measurement period but it is suggested that a representation of iodine chemistry in the model is also required.Correspondence to: L. M. O'Brien (lmo29@cam.ac.uk)

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Section: Introductionsupporting

confidence: 59%

Section: Comparison Of Measured and Modelled Bromocarbon Concentrationsmentioning

confidence: 71%

Bromocarbons in the tropical marine boundary layer at the Cape Verde Observatory – measurements and modelling

et al. 2009

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“…This suggests that biomass burning is a possible additional source of CHBr 3 . High mixing ratios of CHBr 3 associated with African savannah biomass burning plumes were documented in Carpenter et al (2007). The lack of biomass burning emissions can also explain the lack of variability in simulated CHBr 3 mixing ratios compared with the high variability observed in the INTEX-A mission, during which significant biomass burning plumes were sampled (Turquety et al, 2007;Liang et al, 2007).…”

Section: Chbrmentioning

confidence: 81%

Finding the missing stratospheric Bry: a global modeling study of CHBr3 and CH2Br2

et al. 2010

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Abstract. Recent in situ and satellite measurements suggest a contribution of ∼5 pptv to stratospheric inorganic bromine from short-lived bromocarbons. We conduct a modeling study of the two most important short-lived bromocarbons, bromoform (CHBr 3 ) and dibromomethane (CH 2 Br 2 ), with the Goddard Earth Observing System Chemistry Climate Model (GEOS CCM) to account for this missing stratospheric bromine. We derive a "top-down" emission estimate of CHBr 3 and CH 2 Br 2 using airborne measurements in the Pacific and North American troposphere and lower stratosphere obtained during previous NASA aircraft campaigns. Our emission estimate suggests that to reproduce the observed concentrations in the free troposphere, a global oceanic emission of 425 Gg Br yr −1 for CHBr 3 and 57 Gg Br yr −1 for CH 2 Br 2 is needed, with 60% of emissions from open ocean and 40% from coastal regions. Although our simple emission scheme assumes no seasonal variations, the model reproduces the observed seasonal variations of the short-lived bromocarbons with high concentrations in winter and low concentrations in summer. This indicates that the seasonality of short-lived bromocarbons is largely due to seasonality in their chemical loss and transport. The inclusion Correspondence to: Q. Liang (qing.liang@nasa.gov) of CHBr 3 and CH 2 Br 2 contributes ∼5 pptv bromine throughout the stratosphere. Both the source gases and inorganic bromine produced from source gas degradation (Br VSLS y ) in the troposphere are transported into the stratosphere, and are equally important. Inorganic bromine accounts for half (2.5 pptv) of the bromine from the inclusion of CHBr 3 and CH 2 Br 2 near the tropical tropopause and its contribution rapidly increases to ∼100% as altitude increases. More than 85% of the wet scavenging of Br VSLS y occurs in large-scale precipitation below 500 hPa. Our sensitivity study with wet scavenging in convective updrafts switched off suggests that Br VSLS y in the stratosphere is not sensitive to convection. Convective scavenging only accounts for ∼0.2 pptv (4%) difference in inorganic bromine delivered to the stratosphere.

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“…Quack and Wallace, 2004), except for certain upwelling regions (e.g. Class and Ballschmiter, 1988;Quack et al, 2004;Carpenter et al, 2007), where a high abundance of phytoplankton is expected to account for strong emissions of these bromocarbons. Several studies (e.g.…”

Section: Introductionmentioning

confidence: 99%

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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Bromoform in tropical Atlantic air from 25°N to 25°S

Cited by 32 publications

References 23 publications

Bromocarbons in the tropical marine boundary layer at the Cape Verde Observatory – measurements and modelling

Bromocarbons in the tropical marine boundary layer at the Cape Verde Observatory – measurements and modelling

Finding the missing stratospheric Br<sub>y</sub>: a global modeling study of CHBr<sub>3</sub> and CH<sub>2</sub>Br<sub>2</sub>

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

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Bromoform in tropical Atlantic air from 25°N to 25°S

Cited by 32 publications

References 23 publications

Bromocarbons in the tropical marine boundary layer at the Cape Verde Observatory – measurements and modelling

Bromocarbons in the tropical marine boundary layer at the Cape Verde Observatory – measurements and modelling

Finding the missing stratospheric Br&lt;sub&gt;y&lt;/sub&gt;: a global modeling study of CHBr&lt;sub&gt;3&lt;/sub&gt; and CH&lt;sub&gt;2&lt;/sub&gt;Br&lt;sub&gt;2&lt;/sub&gt;

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

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Product

Resources

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Finding the missing stratospheric Br<sub>y</sub>: a global modeling study of CHBr<sub>3</sub> and CH<sub>2</sub>Br<sub>2</sub>