Atmospheric bromoform at Mace Head, Ireland: seasonality and evidence for a peatland source

Abstract. In situ atmospheric observations of bromoform (CHBr3) made over a 2.5 year period at Mace Head, Ireland from May 2001- Dec 2003, including during the NAMBLEX (North Atlantic Marine Boundary Layer Experiment) campaign, show broad maxima from spring until autumn and winter minima, with mixing ratios of 5.3+1.0 pptv (mid March - mid October) and 1.8+0.8 pptv (December-February). This indicates that, unlike CHCl3, which has a summer minimum and winter maximum at Mace Head, local biological sources of CHBr3 have a greater influence on the atmospheric data than photochemical decay during long-range transport. The emission sources are predominantly macroalgal, but we find evidence for a small terrestrial flux from peatland ecosystems, which so far has not been accounted for in the CHBr3 budget. Sharp increases in CHCl3 and CHBr3 concentrations and decreases in O3 concentrations occurred at night when the wind direction switched from an ocean- to a land-based sector (land breeze) and the wind speed dropped to below 5 ms-1. These observations infer a shallow atmospheric boundary layer with increased O3 deposition and concentration of local emissions of both CHCl3 and CHBr3. The ratio of ΔCHCl3/ΔCHBr3 varied strongly according to the prevailing wind direction; from 0.60+0.15 in south-easterly (100-170° and northerly (340-20°) air to 2.5+0.4 in north-easterly (40-70°) air. Of these land-sectors, the south-easterly air masses are likely to be strongly influenced by macroalgal beds along the coast and the emission ratios probably reflect those from seaweeds in addition to land sources. The north-easterly airmasses however had an immediate fetch inland, which locally is comprised of coastal peatland ecosystems (peat bogs and coastal conifer plantations), previously identified as being strong sources of atmospheric CHCl3 under these conditions. Although we cannot entirely rule out other local land or coastal sources, our observations also suggest peatland ecosystem emissions of CHBr3. We use correlations between CHCl3 and CHBr3 during the north-easterly land breeze events in conjunction with previous estimates of local wetland CHCl3 release to tentatively deduce a global wetland CHBr3 source of 20.4(0.4-948) Gg yr-1, which is approximately 7% of the total global source.

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Atmospheric bromoform at Mace Head, Ireland: Evidence for a peatland source

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-5-5935-2005 ◽

2005 ◽

Vol 5 (4) ◽

pp. 5935-5955 ◽

Cited By ~ 2

Author(s):

L. J. Carpenter ◽

D. J. Wevill ◽

S. O’Doherty ◽

G. Spain ◽

P. G. Simmonds

Keyword(s):

Boundary Layer ◽

Wind Direction ◽

Marine Boundary Layer ◽

Land Breeze ◽

Peat Bogs ◽

Mixing Ratios ◽

The North ◽

Prevailing Wind Direction ◽

Atmospheric Observations ◽

Summer Minimum

Abstract. In situ atmospheric observations of bromoform (CHBr3) made over a 2.5 year period at Mace Head, Ireland from May 2001–December 2003, including during the NAMBLEX (North Atlantic Marine Boundary Layer Experiment) campaign, show broad maxima from spring until autumn and winter minima, with mixing ratios of 5.3+1.0 pptv (mid March–mid October) and 1.8+0.8 pptv (December–February). This indicates that, unlike CHCl3, which has a summer minimum and winter maximum at Mace Head, local biological sources of CHBr3 have a greater influence on the atmospheric data than photochemical decay during long-range transport. The emission sources are predominantly macroalgal, but we find evidence for a small terrestrial flux from peatland ecosystems, which so far has not been accounted for in the CHBr3 budget. Sharp increases in CHCl3 and CHBr3 concentrations and decreases in O3 concentrations occurred at night when the wind direction switched from an ocean- to a land-based sector (land breeze) and the wind speed dropped to below 5 ms−1. These observations infer a shallow atmospheric boundary layer with increased O3 deposition and concentration of local emissions of both CHCl3 and CHBr3. The ratio of ΔCHCl3/ΔCHBr3 varied strongly according to the prevailing wind direction; from 0.6+0.1 in south-easterly (100–170°) air to 1.9+0.8 in north-easterly (40–70°) air. Of these land-sectors, the south-easterly air masses are likely to be strongly influenced by macroalgal beds along the coast and the emission ratios probably reflect those from seaweeds in addition to land sources. The north-easterly airmasses however have a fetch predominantly over land, which locally is comprised of coastal peatland ecosystems (peat bogs and coastal conifer plantations), previously identified as being strong sources of atmospheric CHCl3 under these conditions. Although we cannot entirely rule out other local land or coastal sources, our observations also suggest peatland ecosystem emissions of CHBr3. We use correlations between CHCl3 and CHBr3 during the land breeze events in conjunction with previous estimates of local wetland CHCl3 release to tentatively deduce a global wetland CHBr3 source of 26.9 (0.5–1247) Gg yr−1, which is approximately 10% of the total global source.

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Increasing ozone in marine boundary layer inflow at the west coasts of North America and Europe

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-1303-2009 ◽

2009 ◽

Vol 9 (4) ◽

pp. 1303-1323 ◽

Cited By ~ 129

Author(s):

D. D. Parrish ◽

D. B. Millet ◽

A. H. Goldstein

Keyword(s):

Boundary Layer ◽

North America ◽

North American ◽

West Coast ◽

American West ◽

Marine Boundary Layer ◽

North American West ◽

Mixing Ratios ◽

The North ◽

Marine Air

Abstract. An effective method is presented for determining the ozone (O3) mixing ratio in the onshore flow of marine air at the North American west coast. By combining the data available from all marine boundary layer (MBL) sites with simultaneous wind data, decadal temporal trends of MBL O3 in all seasons are established with high precision. The average springtime temporal trend over the past two decades is 0.46 ppbv/yr with a 95% confidence limit of 0.13 ppbv/yr, and statistically significant trends are found for all seasons except autumn, which does have a significantly smaller trend than other seasons. The average trend in mean annual ozone is 0.34±0.09 ppbv/yr. These decadal trends at the North American west coast present a striking comparison and contrast with the trends reported for the European west coast at Mace Head, Ireland. The trends in the winter, spring and summer seasons compare well at the two locations, while the Mace Head trend is significantly greater in autumn. Even though the trends are similar, the absolute O3 mixing ratios differ markedly, with the marine air arriving at Europe in all seasons containing 7±2 ppbv higher ozone than marine air arriving at North America. Further, the ozone mixing ratios at the North American west coast show no indication of stabilizing as has been reported for Mace Head. In a larger historical context the background boundary layer O3 mixing ratios over the 130 years covered by available data have increased substantially (by a factor of two to three), and this increase continues at present, at least in the MBL of the Pacific coast region of North America. The reproduction of the increasing trends in MBL O3 over the past two decades, as well as the difference in the O3 mixing ratios between the two coastal regions will present a significant challenge for global chemical transport models. Further, the ability of the models to at least semi-quantitatively reproduce the longer-term, historical trends may an even greater challenge.

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Two-years of NO<sub>3</sub> radical observations in the boundary layer over the Eastern Mediterranean

Atmospheric Chemistry and Physics ◽

10.5194/acp-7-315-2007 ◽

2007 ◽

Vol 7 (2) ◽

pp. 315-327 ◽

Cited By ~ 39

Author(s):

M. Vrekoussis ◽

N. Mihalopoulos ◽

E. Gerasopoulos ◽

M. Kanakidou ◽

P. J. Crutzen ◽

...

Keyword(s):

Boundary Layer ◽

Marine Boundary Layer ◽

Heterogeneous Reaction ◽

Eastern Mediterranean ◽

North Coast ◽

Data Set ◽

East Europe ◽

Dinitrogen Pentoxide ◽

Mixing Ratios ◽

The North

Abstract. This is the first study that investigates the seasonal variability of nitrate (NO3) radicals in the marine boundary layer over the East Mediterranean Sea. An extensive data set of NO3 radical observations on the north coast of Crete for more than two years (June 2001–September 2003) is presented here. NO3 radicals follow a distinct seasonal dependency with the highest seasonally average mixing ratios in summer (5.6±1.2 pptv) and the lowest in winter (1.2±1.2 pptv). Episodes with high NO3 mixing ratios have been encountered mainly in polluted air masses originating from mainland Greece, Central and East Europe, and Turkey. Ancillary measurements of ozone, nitrogen dioxide (NO2) and meteorological parameters have been conducted and used to reveal possible relationship with the observed NO3 variability. The acquired NO2 nighttime observations provide the up-to-date most complete overview of NO2 temporal variability in the area. The data show correlations of the NO3 nighttime mixing ratios with temperature (positive), relative humidity (negative) and to a lesser extend with O3 (positive). As inferred from these observations, on average the major sink of NO3 radicals in the area is the heterogeneous reaction of dinitrogen pentoxide (N2O5) on aqueous particles whereas the homogeneous gas phase reactions of NO3 are most important during spring and summer. These observations support a significant contribution of NO3 nighttime chemistry to the oxidizing capacity of the troposphere.

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Two-years of NO<sub>3</sub> radical observations in the boundary layer over the Eastern Mediterranean

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-6-9517-2006 ◽

2006 ◽

Vol 6 (5) ◽

pp. 9517-9544

Author(s):

M. Vrekoussis ◽

N. Mihalopoulos ◽

E. Gerasopoulos ◽

M. Kanakidou ◽

P. Crutzen ◽

...

Keyword(s):

Boundary Layer ◽

Marine Boundary Layer ◽

Heterogeneous Reaction ◽

Eastern Mediterranean ◽

North Coast ◽

Peroxy Radicals ◽

Data Set ◽

Positive Correlation ◽

Mixing Ratios ◽

The North

Abstract. This is the first study that investigates the seasonal variability of nitrate (NO3) radicals in the marine boundary layer over the East Mediterranean Sea. An extensive data set of NO3 radical observations on the north coast of Crete for more than two years (June 2001–September 2003) is presented here. NO3 radicals follow a distinct seasonal dependency with maximum mixing ratios in summer (5.6±1.2 pptv) and minimum in winter (1.2±1.2 pptv). Episodes with high NO3 mixing ratios have been encountered mainly in polluted air masses originating from mainland Greece, Central and East Europe, and Turkey. Ancillary measurements of ozone, nitrogen dioxide (NO2 and meteorological parameters have been conducted and used to explain the observed NO3 variability. The acquired NO2 nighttime observations provide the up-to-date most complete overview of NO2 temporal variability in the area. The data show that the NO3 nighttime mixing ratios are primarily dependent on NO2 (positive correlation) and relative humidity (negative correlation) and to a lesser extend on temperature (positive correlation). As inferred from these observations, on average the major sink of NO3 radicals in the area is the heterogeneous reaction of dinitrogen pentoxide (N2O5) on aqueous particles whereas the homogeneous gas phase reactions of NO3 are most important during spring and summer. NO 3 chemistry in the area significantly contributes to VOC oxidation and to the nighttime formation of peroxy radicals, nitric acid and particulate nitrate.

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Dynamical and thermodynamical coupling between the North Atlantic subtropical high and the marine boundary layer clouds in boreal summer

Climate Dynamics ◽

10.1007/s00382-017-3750-6 ◽

2017 ◽

Vol 50 (7-8) ◽

pp. 2457-2469 ◽

Cited By ~ 2

Author(s):

Wei Wei ◽

Wenhong Li ◽

Yi Deng ◽

Song Yang ◽

Jonathan H. Jiang ◽

...

Keyword(s):

Boundary Layer ◽

North Atlantic ◽

Marine Boundary Layer ◽

Subtropical High ◽

Boreal Summer ◽

Boundary Layer Clouds ◽

North Atlantic Subtropical High ◽

The North ◽

The North Atlantic

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Oxidation photochemistry in the Southern Atlantic boundary layer: unexpected deviations of photochemical steady state

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-7045-2011 ◽

2011 ◽

Vol 11 (3) ◽

pp. 7045-7093 ◽

Cited By ~ 4

Author(s):

Z. Hosaynali Beygi ◽

H. Fischer ◽

H. D. Harder ◽

M. Martinez ◽

R. Sander ◽

...

Keyword(s):

Boundary Layer ◽

Steady State ◽

Atlantic Ocean ◽

Atmospheric Chemistry ◽

Marine Boundary Layer ◽

Air Pollutant ◽

Photochemical Oxidant ◽

Important Region ◽

Atmospheric Observations ◽

Oxidation Efficiency

Abstract. Ozone (O3) is a photochemical oxidant, an air pollutant and a greenhouse gas. As the main precursor of the hydroxyl radical (OH) it strongly affects the oxidation power of the atmosphere. The remote marine boundary layer (MBL) is considered an important region in terms of chemical O3 loss; however surface-based atmospheric observations are sparse and the photochemical processes are not well understood. To investigate the photochemistry under the clean background conditions of the Southern Atlantic Ocean, ship measurements of NO, NO2, O3, JNO2, J(O1D), HO2, OH, ROx and a range of meteorological parameters were carried out. The concentrations of NO and NO2 measured on board the French research vessel Marion-Dufresne (28° S–57° S, 46° W–34° E) in March 2007, are among the lowest yet observed. The data is evaluated for consistency with photochemical steady state (PSS) conditions, and the calculations indicate substantial deviations from PSS (Φ>1). The deviations observed under low NOx conditions (5–25 pptv) demonstrate a remarkable upward tendency in the Leighton ratio (used to characterize PSS) with increasing NOx mixing ratio and JNO2 intensity. It is a paradigm in atmospheric chemistry that OH largely controls the oxidation efficiency of the atmosphere. However, evidence is growing that for unpolluted low-NOx (NO + NO2) conditions the atmospheric oxidant budget is poorly understood. Nevertheless, for the very cleanest conditions, typical for the remote marine boundary layer, good model agreement with measured OH and HO2 radicals has been interpreted as accurate understanding of baseline photochemistry. Here we show that such agreement can be deceptive and that a yet unidentified oxidant is needed to explain the photochemical conditions observed at 40°–60° S over the Atlantic Ocean.

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The North Atlantic Marine Boundary Layer Experiment(NAMBLEX). Overview of the campaign held at Mace Head, Ireland, in summer 2002

Atmospheric Chemistry and Physics ◽

10.5194/acp-6-2241-2006 ◽

2006 ◽

Vol 6 (8) ◽

pp. 2241-2272 ◽

Cited By ~ 48

Author(s):

D. E. Heard ◽

K. A. Read ◽

J. Methven ◽

S. Al-Haider ◽

W. J. Bloss ◽

...

Keyword(s):

Boundary Layer ◽

North Atlantic ◽

Marine Boundary Layer ◽

Numerical Models ◽

Measurement Data ◽

Air Mass ◽

The North ◽

Trace Species ◽

Wide Range ◽

The North Atlantic

Abstract. The North Atlantic Marine Boundary Layer Experiment (NAMBLEX), involving over 50 scientists from 12 institutions, took place at Mace Head, Ireland (53.32° N, 9.90° W), between 23 July and 4 September 2002. A wide range of state-of-the-art instrumentation enabled detailed measurements of the boundary layer structure and atmospheric composition in the gas and aerosol phase to be made, providing one of the most comprehensive in situ studies of the marine boundary layer to date. This overview paper describes the aims of the NAMBLEX project in the context of previous field campaigns in the Marine Boundary Layer (MBL), the overall layout of the site, a summary of the instrumentation deployed, the temporal coverage of the measurement data, and the numerical models used to interpret the field data. Measurements of some trace species were made for the first time during the campaign, which was characterised by predominantly clean air of marine origin, but more polluted air with higher levels of NOx originating from continental regions was also experienced. This paper provides a summary of the meteorological measurements and Planetary Boundary Layer (PBL) structure measurements, presents time series of some of the longer-lived trace species (O3, CO, H2, DMS, CH4, NMHC, NOx, NOy, PAN) and summarises measurements of other species that are described in more detail in other papers within this special issue, namely oxygenated VOCs, HCHO, peroxides, organo-halogenated species, a range of shorter lived halogen species (I2, OIO, IO, BrO), NO3 radicals, photolysis frequencies, the free radicals OH, HO2 and (HO2+Σ RO2), as well as a summary of the aerosol measurements. NAMBLEX was supported by measurements made in the vicinity of Mace Head using the NERC Dornier-228 aircraft. Using ECMWF wind-fields, calculations were made of the air-mass trajectories arriving at Mace Head during NAMBLEX, and were analysed together with both meteorological and trace-gas measurements. In this paper a chemical climatology for the duration of the campaign is presented to interpret the distribution of air-mass origins and emission sources, and to provide a convenient framework of air-mass classification that is used by other papers in this issue for the interpretation of observed variability in levels of trace gases and aerosols.

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Ozone variability and halogen oxidation within the Arctic and sub-Arctic springtime boundary layer

Atmospheric Chemistry and Physics ◽

10.5194/acp-10-10223-2010 ◽

2010 ◽

Vol 10 (21) ◽

pp. 10223-10236 ◽

Cited By ~ 92

Author(s):

J. B. Gilman ◽

J. F. Burkhart ◽

B. M. Lerner ◽

E. J. Williams ◽

W. C. Kuster ◽

...

Keyword(s):

Boundary Layer ◽

North Atlantic ◽

Marine Boundary Layer ◽

Transport Model ◽

Arctic Basin ◽

The Arctic ◽

Arctic Boundary Layer ◽

Air Masses ◽

The North ◽

The North Atlantic

Abstract. The influence of halogen oxidation on the variabilities of ozone (O3) and volatile organic compounds (VOCs) within the Arctic and sub-Arctic atmospheric boundary layer was investigated using field measurements from multiple campaigns conducted in March and April 2008 as part of the POLARCAT project. For the ship-based measurements, a high degree of correlation (r = 0.98 for 544 data points collected north of 68° N) was observed between the acetylene to benzene ratio, used as a marker for chlorine and bromine oxidation, and O3 signifying the vast influence of halogen oxidation throughout the ice-free regions of the North Atlantic. Concurrent airborne and ground-based measurements in the Alaskan Arctic substantiated this correlation and were used to demonstrate that halogen oxidation influenced O3 variability throughout the Arctic boundary layer during these springtime studies. Measurements aboard the R/V Knorr in the North Atlantic and Arctic Oceans provided a unique view of the transport of O3-poor air masses from the Arctic Basin to latitudes as far south as 52° N. FLEXPART, a Lagrangian transport model, was used to quantitatively determine the exposure of air masses encountered by the ship to first-year ice (FYI), multi-year ice (MYI), and total ICE (FYI+MYI). O3 anti-correlated with the modeled total ICE tracer (r = −0.86) indicating that up to 73% of the O3 variability measured in the Arctic marine boundary layer could be related to sea ice exposure.

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Continental outflow from the US to the upper troposphere over the North Atlantic during the NASA INTEX-NA Airborne Campaign

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-1989-2008 ◽

2008 ◽

Vol 8 (7) ◽

pp. 1989-2005 ◽

Cited By ~ 7

Author(s):

S. Y. Kim ◽

R. Talbot ◽

H. Mao ◽

D. Blake ◽

S. Vay ◽

...

Keyword(s):

Boundary Layer ◽

North Atlantic ◽

The United States ◽

Upper Troposphere ◽

Mixing Ratios ◽

The North ◽

Southeastern Us ◽

The Us ◽

The North Atlantic ◽

Continental Outflow

Abstract. A case of continental outflow from the United States (US) was examined using airborne measurements from NASA DC-8 flight 13 during the Intercontinental Chemical Transport Experiment – North America (INTEX-NA). Mixing ratios of methane (CH4) and carbon monoxide (CO) at 8–11 km altitude over the North Atlantic were elevated to 1843 ppbv and 134 ppbv respectively, while those of carbon dioxide (CO2) and carbonyl sulfide (COS) were reduced to 372.4 ppmv and 411 pptv respectively. In this region, urban and industrial influences were evidenced by elevated mixing ratios and good linear relationships between urban and industrial tracers compared to North Atlantic background air. Moreover, low mixing ratios and a good correlation between COS and CO2 showed a fingerprint of terrestrial uptake and minimal dilution during rapid transport over a 1–2 day time period. Analysis of synoptic conditions, backward trajectories, and photochemical aging estimates based on C3H8/C2H6 strongly suggested that elevated anthropogenic tracers in the upper troposphere of the flight region were the result of transport via convection and warm conveyor belt (WCB) uplifting of boundary layer air over the southeastern US. This mechanism is supported by the similar slope values of linear correlations between long-lived (months) anthropogenic tracers (e.g., C2Cl4 and CHCl3) from the flight region and the planetary boundary layer in the southeastern US. In addition, the aircraft measurements suggest that outflow from the US augmented the entire tropospheric column at mid-latitudes over the North Atlantic. Overall, the flight 13 data demonstrate a pervasive impact of US anthropogenic emissions on the troposphere over the North Atlantic.

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