Modeling halogen chemistry in the marine boundary layer 1. Cloud‐free MBL

Glasow, R. von; Sander, R.; Bott, Andreas; Crutzen, Paul J.

doi:10.1029/2001jd000942

Cited by 207 publications

(309 citation statements)

References 92 publications

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“…The cycle is initiated with the oxidation of X − in sea salt to form HOX by reaction with OH, O 3 , or HSO 5 − (ref 14). Aerosol acidity determines the displacement of HCl and the equilibrium between HOCl and Cl 2 (eq 2).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Multiphase Halogen Chemistry in the Tropical Atlantic Ocean

Sommariva

Glasow

2012

Environ. Sci. Technol.

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We used a one-dimensional model to simulate the chemical evolution of air masses in the tropical Atlantic Ocean, with a focus on halogen chemistry. The model results were compared to the observations of inorganic halogen species made in this region. The model could largely reproduce the measurements of most chlorine species, especially under unpolluted conditions, but overestimated sea salt chloride, BrCl, and bromine species. Agreement with the measurements could be improved by taking into account the reactivity with aldehydes and the effects of dimethyl sulfide (DMS) and Saharan dust on aerosol pH; a hypothetical HOX → X − aqueous-phase reaction could also improve the agreement with measured Cl 2 and HOCl, especially under semipolluted conditions. The results also showed that halogens speciation and concentrations are very sensitive to cloud processing. The model was used to calculate the impact of the observed levels of halogens: Cl atoms accounted for 5.4−11.6% of total methane sinks and halogens (mostly bromine and iodine) accounted for 35−40% of total ozone destruction. ■ INTRODUCTIONThe tropical marine boundary layer (MBL) is a region of particular interest for atmospheric chemistry: high levels of solar radiation, along with high temperatures and relative humidities, result in a highly oxidizing environment. It is estimated that the tropical atmosphere accounts for up to 80% of the global oxidation of methane (the second most important greenhouse gas) and that ∼25% of the global oxidation of methane occurs in the tropical MBL. 1 Halogen species (chlorine, bromine, iodine) are known to play an important role in the chemical processes of the MBL, particularly with regard to the nitrogen and ozone cycles, sulfur chemistry and particle formation: an overview of halogen chemistry and its impact on atmospheric chemical processes can be found in ref 2. Measurements of these species in the tropical region are sparse, but a number of recent studies 3−13 have reported observations of several halogen species in the tropical Atlantic Ocean. These studies suggested that halogen chemistry is responsible for a large fraction (∼30%) of ozone destruction in the Tropics 6 and up to 7% of the global methane destruction. 9 In this paper, we used the one-dimensional chemical model MISTRA to study halogen chemistry in the tropical Atlantic Ocean and the evolution of the chemical composition of air masses traveling across the ocean to the islands of Cape Verde, 900 km West of the coast of Africa. We compared the model results to the database of published observations of halogen species from this region with the objective of testing our understanding of halogen chemistry and of quantifying the impact of the observed halogens levels on ozone (O 3 ) and methane (CH 4 ). ■ METHODSModel. MISTRA is a one-dimensional model of the MBL. The model includes a description of meteorological and microphysical processes in the MBL and is described in detail in refs 14 and 15. Version 7.4.1 of MISTRA includes a number of improvement...

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Section: ■ Results and Discussionmentioning

confidence: 99%

Multiphase Halogen Chemistry in the Tropical Atlantic Ocean

Sommariva

Glasow

2012

Environ. Sci. Technol.

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“…ClO is with typically 10% (about 5 pmol mol À1 at ground level) the next important contributor to daytime Cl x , its importance increases with time (less than 2% on the first day) and altitude (up to 30% at the top of the MBL, see Cl 2 ). Like BrO, ClO peaks in the morning and late afternoon (about 10 pmol mol À1 , see explanation in von Glasow et al [2002]). In NOON the partitioning is different on the first day, as significantly higher NO x levels are present than in the runs where model start is at midnight, therefore in this run, ClONO 2 contributes about 36% to Cl x on the first day.…”

Section: Chlorine Release and Speciationmentioning

confidence: 99%

“…[5] We used the one-dimensional marine boundary layer model MISTRA [von Glasow et al, 2002]. It includes detailed chemistry in the gas and particulate phase (sulfate and sea salt aerosol), comprising the most important reactions of H, O, C, N, S, Cl, and Br.…”

Section: Model Descriptionmentioning

confidence: 99%

Reactive chlorine in the marine boundary layer in the outflow of polluted continental air: A model study

Pechtl

Glasow

2007

Geophysical Research Letters

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[1] Results from a numerical one-dimensional model show that continental pollution that is advected over the ocean leads to substantial acid displacement from newly emitted sea salt aerosol. Oxidation of HCl by OH and cycling between the gas and aerosol phase lead to a build-up of nighttime Cl 2 mixing ratios of up to 90 pmol mol À1 in our base scenario and 125 pmol mol À1 in a sensitivity study with high wind speeds. Therefore the recirculation of continental airmasses over the ocean and back to the coast might explain previous measurements of high nighttime Cl 2 in onshore winds. Furthermore, the model runs suggest a substantial contribution of daytime Cl-radical chemistry to the oxidation of volatile organic compounds under these conditions. Citation: Pechtl, S., and R. von , Reactive chlorine in the marine boundary layer in the outflow of polluted continental air: A model study, Geophys. Res. Lett., 34, L11813,

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“…Strong westerlies prevail most of the year in the Patagonian latitudinal belt leading to high sea salt production only partly counterbalanced by the increase of this vertical concentration gradient with increasing wind speed. Thus significant amounts of sea salt aerosol are expected to reach the inversion layer and act as cloud condensation nuclei while a smaller submicronic part reaches the free troposphere along with halogens and sulfur species [Von Glascow andSander, 2002, Clarke andKapustin, 2002]. The San Valentín summit area is less than 100 km away from the Pacific Ocean coast and may be part of the year close to the top of the stratiform cloud coverage which controls the marine boundary layer during a large part of the year in southern South America as suggested by an ongoing and preliminary study aiming at estimating the elevation of the clouds layer relatively to the San Valentín summit using satellite pictures (F. Maignan, personal communication).…”

Section: Marine Inputs and Deuterium Excess: Complementary Markers Ofmentioning

confidence: 99%

A promising location in Patagonia for paleoclimate and paleoenvironmental reconstructions revealed by a shallow firn core from Monte San Valentín (Northern Patagonia Icefield, Chile)

et al. 2008

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International audienceThe study of past climate variability from ice core investigations has been largely developed both in polar areas over the past decades and, more recently, in tropical regions, specifically along the South American Andes between 0° and 20°S. However a large gap still remains at mid-latitudes in the Southern Hemisphere. In this framework, a 15.3-m long shallow firn core has been extracted in March 2005 from the summit plateau of Monte San Valentín (3747 m, 46°35′S, 73°19′W) in the Northern Patagonia Icefield to test its potential for paleoclimate and paleoenvironmental reconstructions. The firn temperature is −11.9°C at 10-m depth allowing to expect well preserved both chemical and isotopic signals, unperturbed by water percolation. The dating of the core, on the basis of a multi-proxy approach combining annual layer counting and radionuclide measurements, shows that past environment and climate can be reconstructed back to the mid-1960s. A mean annual snow accumulation rate of 36 ± 3 cm year−1 (i.e., 19 ± 2 g cm−2 year−1) is inferred, with a snow density varying between 0.35 and 0.6 g cm−3, which is much lower than accumulation rates previously reported in Patagonia at lower elevations. Here, we present and discuss high-resolution profiles of the isotopic composition of the snow and selected chemical markers. These data provide original information on environmental conditions prevailing over Southern Patagonia in terms of air masses trajectories and origins and biogeochemical reservoirs. Our main conclusion is that the San Valentín site is not only influenced by air masses originating from the southern Pacific and directly transported by the prevailing west winds but also by inputs from South American continental sources from the E–NE, sometimes mixed with circumpolar aged air masses, the relative influence of these two very distinct source areas changing at the interannual timescale. Thus this site should offer a wealth of information regarding (South) Pacific, Argentinian NE–E areas and Antarctic climate variability

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Modeling halogen chemistry in the marine boundary layer 1. Cloud‐free MBL

Cited by 207 publications

References 92 publications

Multiphase Halogen Chemistry in the Tropical Atlantic Ocean

Multiphase Halogen Chemistry in the Tropical Atlantic Ocean

Reactive chlorine in the marine boundary layer in the outflow of polluted continental air: A model study

A promising location in Patagonia for paleoclimate and paleoenvironmental reconstructions revealed by a shallow firn core from Monte San Valentín (Northern Patagonia Icefield, Chile)

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