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Journal Publications

This section contains all refereed journal publications that have some connection either with the Mace Head Research Station or with members, both present and past, of the Atmospheric Physics Research Cluster at NUI, Galway.

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Documents

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Overview of the synoptic and pollution situation over Europe during the EUCAARI-LONGREX field campai Overview of the synoptic and pollution situation over Europe during the EUCAARI-LONGREX field campai

Date added: 02/07/2011
Date modified: 02/07/2011
Filesize: 2.98 MB

Hamburger, T., G. McMeeking, A. Minikin, W. Birmili, M. Dall’Osto, C. O’Dowd, H. Flentje, B. Henzing, H. Junninen, A. Kristensson, G. de Leeuw, A. Stohl, J. F. Burkhart, H. Coe, R. Krejci, and A. Petzold



 

Abstract. In May 2008 the EUCAARI-LONGREX aircraft field campaign was conducted within the EUCAARI intensive observational period. The campaign aimed at studying the distribution and evolution of air mass properties on a continental scale. Airborne aerosol and trace gas measurements were performed aboard the German DLR Falcon 20 and the British FAAM BAe-146 aircraft. This paper outlines the meteorological situation over Europe during May 2008 and the temporal and spatial evolution of predominantly anthropogenic particulate pollution inside the boundary layer and the free troposphere. Time series data of six  selected ground stations are used to discuss continuous measurements besides the single flights. The observations encompass total and accumulation mode particle number concentration (0.1–0.8 μm) and black carbon mass concentration as well as several meteorological parameters. Vertical profiles of total aerosol number concentration up to 10 km are compared to vertical profiles probed during previous studies.During the first half of May 2008 an anticyclonic blocking event dominated the weather over Central Europe. It led to increased pollutant concentrations within the centre of the high pressure inside the boundary layer. Due to long-range transport the accumulated pollution was partly advected towards Western and Northern Europe. The measured aerosol number concentrations over Central Europe showed in the boundary layer high values up to 14 000 cm−3 for particles in diameter larger 10 nm and 2300 cm−3 for accumulation mode particles during the high pressure period, whereas the middle free troposphere showed rather low concentrations of particulates. Thus a strong negative gradient of aerosol concentrations between the well mixed boundary layer and the clean middle troposphere occurred.

Contributions of Primary Organic Matter to Marine Aerosol Contributions of Primary Organic Matter to Marine Aerosol

Date added: 01/31/2011
Date modified: 01/31/2011
Filesize: 583.72 kB

Ovadnevaite, J., M. Dall'Osto, D. Ceburnis, C. Monahan, D. Worsnop, C. O’Dowd and H. Berresheim Detecting Very High Contributions of Primary Organic Matter to Marine Aerosol, Geophys. Res. Letts., doi:10.1029/2010GL046083 , 2011.


Using on‐line High‐Resolution Aerosol Mass Spectrometry, we report submicron organic marine aerosol plume concentrations peaking at 3.8 mg m−3. These concentrations are far greater than previously determinedby off‐line techniques and can exceed typica terrestrial concentrations of organic aerosol. The organic mass comprised 77% of the total submicron non‐refractory mass and such plumes were associated with regions of high biological activity and moderately‐high wind speeds over the N.E. Atlantic. High‐resolution mass spectra analysis revealed a unique marine organic aerosol fingerprint, when compared to anthropogenic organic aerosol, and in particular, anthropogenic hydrocarbons. 37% hydrocarbon and 63% oxygenated hydrocarbon speciation was observed for the organic mass, indicating that at least 37% of the organic mass is produced via primary sea‐spray. The hydrocarbon and oxygenated hydrocarbon species were highly correlated (r > 0.99) suggesting a significant, if not dominant, fraction of the oxygenated component is also likely to be sea‐spray in origin.

Explaining global surface aerosol number concentrations in terms of primary emissions and particle f Explaining global surface aerosol number concentrations in terms of primary emissions and particle f

Date added: 01/31/2011
Date modified: 01/31/2011
Filesize: 972.89 kB

Spracklen, D. V., K. S. Carslaw, J. Merikanto, G. W. Mann, S. Pickering, J. A. Ogren, B. Andrews, U. Baltensperger, E. Weingartner, M. Boy, M. Kulmala, H. Lihavainen, J. Hatakka, N. Mihalopoulos, G. Kouvarakis, S. G. Jennings, C. O’Dowd, W. Birmili, A. Wiedensohler, R. Weller, J. Gras, P. Laj, R. Griffin, B. Bonn, and B. Bandy, Explaining global surface aerosol concentrations in terms of primary emissions and particle formation, Atmos. Chem. Phys., 10, 4775–4793, doi:10.5194/acp-10-4775-2010, 2010


 

Abstract

 

We synthesised observations of total particle number (CN) concentration from 36 sites around the world. We found that annual mean CN concentrations are typically 300–2000 cm−3 in the marine boundary layer and free troposphere (FT) and 1000–10 000 cm−3 in the continental boundary layer (BL). Many sites exhibit pronounced seasonality with summer time concentrations a factor of 2–10 greater than wintertime concentrations. We used these CN obser-vations to evaluate primary and secondary sources of particle  number in a global aerosol microphysics model. We found that emissions of primary particles can reasonably reproduce the spatial pattern of observed CN concentration (R2=0.46) but fail to explain the observed seasonal cycle (R2=0.1). The modeled CN concentration in the FT was biased low (normalised mean bias, NMB=−88%) unless a secondary source of particles was included, for example from binary homogeneous nucleation of sulfuric acid and water (NMB=−25%). Simulated CN concentrations in the continental BL were also biased low (NMB=−74%) unless the number emission of anthropogenic primary particles was increased or a mechanism that results in particle formation in the BL was included. We ran a number of simulations where we included  an empirical BL nucleation mechanism either using the activation-type mechanism (nucleation rate, J , proportional to gas-phase sulfuric acid concentration to the power one) or kinetic-type mechanism (J proportional to sulfuric acid to the power two) with a range of nucleation coefficients. We found that the seasonal CN cycle observed at continental BL sites was better simulated by BL particle formation (R2=0.3) than by increasing the number emission from primary anthropogenic sources (R2=0.18). The nucleation constants that resulted in best overall match between model and observed CN concentrations were consistent with values derived in previous studies from detailed case studies at individual sites. In our model, kinetic and activation-type nucleation parameterizations gave similar agreement with observed monthly mean CN concentrations.

 

SimulatingMarine New Particle Formation and Growth Using theM7Modal Aerosol DynamicsModal SimulatingMarine New Particle Formation and Growth Using theM7Modal Aerosol DynamicsModal

Date added: 01/30/2011
Date modified: 01/31/2011
Filesize: 1.28 MB

Monahan, C., H. Vuollekoski, M. Kulmala, C. O’Dowd. Modelling the Contribution of Iodine Oxide to Marine New Particle Formation, Adv. in Meteorol., Article ID 482603, doi:10.1155/2010/482603, 2010.


A modal atmospheric aerosol model (M7) is evaluated in terms of predicting marine new particle formation and growth. Simulations were carried out for three different nucleation schemes involving (1) kinetic self-nucleation of OIO (2) nucleation via OIO activation by H2SO4 and (3) nucleation via OIO activation by H2SO4 plus condensation of a low-volatility organic vapour. Peak OIO and H2SO4 vapour concentrations were both limited to 6 × 106 molecules cm−3 at noontime while the peak organic vapour concentration was limited to 12×106 molecules cm−3. All simulations produced significant concentrations of new particles in the Aitken mode. From a base case particle concentration of 222 cm−3 at radii >15 nm, increases in concentrations to 366 cm−3 were predicted fromthe OIO-OIO case, 722 cm−3 for the OIO-H2SO4 case, and 1584 cm−3 for the OIO-H2SO4 case with additional condensing organic vapours. The results indicate that open ocean new particle production is feasible for clean conditions; however, new particle production becomes most significant when an additional condensable organic vapour is available to grow the newly formed particles to larger sizes. Comparison to sectional model for a typical case study demonstrated good agreement and the validity of using the modal model.

An overview of current issues in the uptake of atmospheric trace gases by aerosols and clouds An overview of current issues in the uptake of atmospheric trace gases by aerosols and clouds

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 1.06 MB

Kolb, C. E., R. A. Cox, J. P. D. Abbatt, M. Ammann, E. J. Davis, D. J. Donaldson, B. C. Garrett, C. George, P. T. Griffiths, D. R. Hanson, M. Kulmala, G. McFiggans, U. Pöschl, I. Riipinen, M. J. Rossi, Y. Rudich, P. E. Wagner, P. M. Winkler, D. R. Worsnop, and C. D. O' Dowd, An overview of current issues in the uptake of atmospheric trace gases by aerosols and clouds, Atmos. Chem. Phys.10, 10561–10605, doi:10.5194/acp-10-10561-2010, 2010.


A workshop was held in the framework of the ACCENT (Atmospheric Composition Change – a European Network) Joint Research Programme on “Aerosols” and the Programme on “Access to Laboratory Data”. The aim of the workshop was to hold “Gordon Conference” type discussion covering accommodation and reactive uptake of water vapour and trace pollutant gases on condensed phase atmospheric materials. The scope was to review and define the current state of knowledge of accommodation coefficients for water vapour on water droplet and ice surfaces, and uptake of trace gas species on a variety of different surfaces characteristic of the atmospheric condensed phase particulate matter and cloud droplets. Twenty-six scientists participated in this meeting through presentations, discussions and the development of a consensus review.  In this review we present an analysis of the state of knowledge on the thermal and mass accommodation coefficient for  water vapour on aqueous droplets and ice and a survey of current state-of the-art of reactive uptake of trace gases on a range of liquid and solid atmospheric droplets and particles. The review recommends consistent definitions of the various parameters that are needed for quantitative representation of the range of  as/condensed surface kinetic processes important for the atmosphere and identifies topics that require  additional research.

EUCAARI ion spectrometer measurements at 12 European sites – analysis of new-particle formation even EUCAARI ion spectrometer measurements at 12 European sites – analysis of new-particle formation even

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 2.55 MB

Manninen, H. E, .T. Nieminen, E. Asmi, S. Gagné, S. Häkkinen, K. Lehtipalo, P. Aalto, M. Vana, A. Mirme, S. Mirme, U. Hõrrak, C. Plass-Dülmer, G. Stange, G. Kiss, A. Hoffer, N. Tör\H{o}, M. Moerman, B. Henzing, G. de Leeuw, M. Brinkenberg, G. N. Kouvarakis, A. Bougiatioti, N. Mihalopoulos, C. O'Dowd, D. Ceburnis, A. Arneth, B. Svenningsson, E. Swietlicki, L. Tarozzi, S. Decesari, M. C. Facchini, W. Birmili, A. Sonntag, A. Wiedensohler, J. Boulon, K. Sellegri, P. Laj, M. Gysel, N. Bukowiecki, E. Weingartner, G. Wehrle, A. Laaksonen, A. Hamed, J. Joutsensaari, T. Petäjä, V.-M. Kerminen, and M. Kulmala, EUCAARI ion spectrometer measurements at 12 European sites – analysis of new-particle formation events,
Atmos. Chem. Phys., 10, 7907–7927, doi:10.5194/acp-10-7907-2010, 2010


  

We present comprehensive results on continuous atmospheric cluster and particle measurements in the size range 

1–42 nm within the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) project. We focused on characterizing the spatial and temporal variation of new particle formation events and relevant particle formation parameters across Europe. Different types of air ion and cluster mobility spectrometers were deployed at 12 field sites across Europe from March 2008 to May 2009. The measurements were conducted in a wide variety of environments, including coastal and continental locations as well as sites at different altitudes (both in the boundary layer and the free troposphere). New particle formation events were detected at all of the 12 field sites during the year-long measurement period. From the data, nucleation and growth rates of newly formed particles were determined for each environment. In a case of parallel ion and neutral cluster measurements, we could also estimate the relative contribution of ion-induced and neutral nucleation to  the total particle formation. The formation rates of charged particles at 2 nm accounted for 1–30% of the corresponding total particle formation rates. As a significant new result, we found out that the total particle formation rate varied much more between the different sites than the formation rate of charged particles. This work presents, so far, the most comprehensive effort to experimentally characterize nucleation and growth of atmospheric molecular clusters and nanoparticles at ground-based observation sites on a continental scale.

Growth Rates During Coastal and Marine New Particle Formation in Western Ireland Growth Rates During Coastal and Marine New Particle Formation in Western Ireland

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 1.75 MB

Ehn, M., H. Vuollekoski, T. Petäjä, V.-M. Kerminen, M. Vana, P. Aalto, G. de Leeuw, D. Ceburnis, R. Dupuy, C. D. O’Dowd and M. Kulmala, Growth Rates During Coastal and Marine New Particle Formation in Western Ireland, J. Geophys. Res., doi:10.1029/2010JD014292, 2010.


Growth rates of new particles during coastal and marine secondary aerosol particle

formation events were studied in western Ireland, both at the Mace Head atmospheric

research station and onboard the R/V 

Production project. Strong new particle formation events are frequently detected at Mace

Head caused by the emission of precursor gases from exposed seaweed during low tide.

Although these events were usually only detected as a mode of particles at a certain size, we

were able to link the size of the mode to the growth time of these particles after the initial

formation by combining data from several events measured between January 2006 and

November 2007 with an air ion spectrometer. Typically, the early growth rates were

extremely high, reaching values of several hundred nanometers per hour during the first

seconds. The growth rates rapidly decreased and reached values below 1 nm h 

1 h after nucleation. Our results were reproduced with box model calculations. All the

obtained growth rates could be explained by the model either by varying the precursor

formation time (typically a few seconds) or allowing multiple precursor vapor additions.

From the ship

ocean new particle formation detected in this region. In total, four events were detected

during this period, with three having a variable continental influence. An estimated

average growth rate in marine conditions was 3 nm h

Celtic Explorer as part of the Marine Aerosol 1 within borne measurements, we report the first observations of purely open 1 for these events.

The variation of the mixing state of Saharan dust particles with atmospheric transport. The variation of the mixing state of Saharan dust particles with atmospheric transport.

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 1.65 MB

Dall’Osto, R.M. Harrison, E. J.  Highwood, C. O’Dowd, D. Ceburnis, X. Querol and E. P. Achterberg, The variation of the mixing state of Saharan dust particles with atmospheric transport. Atmos. Env., doi:10.1016/j.atmosenv.2010.05.030, 2010,


Mineral dust is an important aerosol species in the Earth

 

s atmosphere and has a major source within North Africa, of which the Sahara forms the major part. Aerosol Time of Flight Mass Spectrometry (ATOFMS) is first used to determine the mixing state of dust particles collected from the land surface in the Saharan region, showing low abundance of species such as nitrate and sulphate internally mixed with the dust mineral matrix. These data are then compared with the ATOFMS single particle mass spectra of Saharan dust particles detected in the marine atmosphere in the vicinity of the Cape Verde islands, which are further compared with those from particles with longer atmospheric residence sampled at a coastal station at Mace Head, Ireland. Saharan dust particles collected near the Cape Verde  Islands showed increased internally mixed nitrate but no sulphate, whilst Saharan dust particles collected on the coast of Ireland showed a very high degree of internally mixed secondary species including nitrate, sulphate and methanesulphonate. This uptake of secondary species will change the pH  and hygroscopic properties of the aerosol dust and thus can influence the budgets of other reactive gases, as well as influencing the radiative properties of the particles and the availability of metals for

dissolution

On The Occurrence of Open Ocean Particle Production Events On The Occurrence of Open Ocean Particle Production Events

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 603.03 kB

O’Dowd, C.D, C. Monahan and M. Dall’Osto, On The Occurrence of Open Ocean Particle Production Events, Geophys. Res. Letts., 37, L19805, doi:10.1029/2010GL044679,  2010.


We present new results from the Mace Head coastal station illustrating that open ocean new particle production and growth events occur frequently during periods of high oceanic productivity over the N.E. Atlantic. For the first time, we report events during which a recently 

formed nucleation mode (15 nm diameter) is detected and is observed to grow into an Aitken mode (50 nm diameter) over periods up to 48 hours. A growth rate of 0.8 nm hour1 is estimated in a typical case study, pointing to a source region 700 km offshore. The duration of the growth also suggests the particle production events are occurring over large spatial scales. Analysis of seven yearsof data show occurrence of extended growth events (lasting at least 24 hours) from March to September, with a peak occurrence in May. The events suggest that secondary marine boundary layer aerosol formation contributes to the marine aerosol population.

Contribution of isoprene oxidation products to marine aerosol over the North-East Atlantic Contribution of isoprene oxidation products to marine aerosol over the North-East Atlantic

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 5.12 MB

Anttila, T., Baerbel Langmann, S. Varghese, C. O’Dowd, Contribution of isoprene oxidation products to marine aerosol over the North-East Atlantic,  Adv. in Meteorol., Volume 2010, Article ID 482603,, 2010


Secondary organic aerosol (SOA) formation through isoprene oxidation was investigated with the regional-scale climate model REMOTE. The appliedmodeling scheme includes a treatment formarine primary organic aerosol emissions, aerosolmicrophysics, and SOA formation through the gas/particle partitioning of semivolatile, water-soluble oxidation products. The focus was on SOA formation taking place over the North-East Atlantic during a period of high biological activity. Isoprene SOA concentrations were up to 

5ng m3 over North Atlantic in the base case model runs, and isoprene oxidation made a negligible contribution to the marine organic aerosol (OA) mass. In particular, isoprene SOA did not account for the observed water-soluble organic carbon (WSOC) concentrations over North Atlantic. The performed model calculations, together with results from recent field measurements, imply a missing source of SOA over remote marine areas unless the isoprene oxidation products are considerably less volatile than the current knowledge indicates.

Eddy correlation measurements of ozone fluxes over coastal waters west if Ireland Eddy correlation measurements of ozone fluxes over coastal waters west if Ireland

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 980.87 kB

McVeigh, P., C. O’Dowd, and H. Berresheim, Eddy correlation measurements of ozone fluxes over coastal waters west if Ireland,  Adv. in Meteorol., Volume 2010, Article ID 754941, doi:10.1155/2010/754941, 2010.

 


 Measurements of ozone fluxes using the eddy-correlation (EC) technique were carried out for the first time at the Mace Head atmospheric research station, on the west coast of Ireland between August-October 2009. Vertical exchange of ozone was measured from a tower platform at 22m above mean sea level to study fluxes over coastal waters excluding the tidal region. The results were averaged over 30 min and exhibited predominantly downward but also upward transport of ozone in the boundary layer. Data quality was found to be high based on inspection of cospectra and micrometeorological measurements. During the study period, a major physical influence on O3 fluxes was found to be wind speed. Measured fluxes were of the same magnitude as reported in previous open ocean studies ranging from approximately +0.2 to 0.5 μg m2 s1 (0.017 μg m2 s1 on average, corresponding to a deposition velocity of 0.25mm s1 or a surface resistance of 4.13 s mm1). These results are considered to represent ozone fluxes over shallow coastal waters west of Ireland for conditions during summer and fall not affected by phytoplankton blooms.

Wind Speed Influences on Marine Aerosol Optical Depth Wind Speed Influences on Marine Aerosol Optical Depth

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 2.04 MB

O’Dowd, C., C. Scannell, J. Mulcahy & S. G. Jennings,   Wind Speed Influences on Marine Aerosol Optical Depth. Adv. in Meteorol., Article ID 830846,  2010. doi:10.1155/2010/830846, 2010.


TheMulcahy (Mulcahy et al., 2008) power-law parameterization, derived at the coastal Atlantic stationMace Head, between clean marine aerosol optical depth (AOD) and wind speed is compared to open ocean MODIS-derived AOD versus wind speed. The reported AOD versus wind speed (U) was a function of 

U2. The open ocean MODIS-derived AOD at 550nm and 860nm wavelengths, while in good agreement with the general magnitude of the Mulcahy parameterization, follows a power-law with the exponent ranging from 0.72 to 2.47 for a wind speed range of 2–18ms1. For the four cases examined, some MODIS cases underestimated AOD while other cases overestimated AOD relative to the Mulcahy scheme. Overall, the results from MODIS support the general power-law relationship of Mulcahy, although some linear cases were also encountered in the MODIS dataset. Deviations also arise between MODIS andMulcahy at higher wind speeds (>15ms1), whereMODIS-derived AOD returns lower values as compared to Mulcahy. The results also support the suggestion than wind generated sea spray, under moderately high winds, can rival anthropogenic pollution plumes advecting out into marine environments with wind driven AOD contributing to AOD values approaching 0.3.

Regional-scale Ozone Deposition to North-East Atlantic Waters Regional-scale Ozone Deposition to North-East Atlantic Waters

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 4.87 MB

Coleman, L., S. Varghese, O.P. Tripathi, S G. Jennings, C.D. O’Dowd, Regional-scale Ozone Deposition to North-East Atlantic Waters, Adv. in Meteorol., Volume 2010, Article ID 243701, doi:10.1155/2010/243701 2010.


A regional climate model is used to evaluate dry deposition of ozone over the North East Atlantic. Results are presented for a deposition scheme accounting for turbulent and chemical enhancement of oceanic ozone deposition and a second non-chemical, parameterised gaseous dry deposition scheme. The first deposition scheme was constrained to account for sea-surface ozone-iodide reactions and the sensitivity of modelled ozone concentrations to oceanic iodide concentration was investigated. Simulations were also performed using nominal reaction rate derived from i

n-situ ozone deposition measurements and using a preliminary representation of organic chemistry. Results show insensitivity of ambient ozone concentrations modelled by the chemicalenhanced scheme to oceanic iodide concentrations, and iodide reactions alone cannot account for observed deposition velocities. Consequently, we suggest a missing chemical sink due to reactions of ozone with organic matter at the air-sea interface. Ozone loss rates are estimated to be in the range of 0.5–6 ppb per day. A potentially significant ozone-driven flux of iodine to the atmosphere is estimated to be in the range of 2.5–500Mmolec cm2 s1, leading to amixing-layer enhancement of organo-iodine concentrations of 0.1–22.0 ppt, with an average increase in the N.E. Atlantic of around 4 ppt per day.

Global modelling of the oceanic source of organic aerosols, Global modelling of the oceanic source of organic aerosols,

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 6.71 MB

Myriokefalitakis, S.,  E. Vignati, K. Tsigaridis, C. Papadimas, J. Sciare, N. Mihalopoulos, M. C. Facchini, M. Rinaldi, F. J. Dentener, D. Ceburnis, N. Hatzianastassiou, C.D. O'Dowd, M. van Weele and M. Kanakidou, Global modelling of the oceanic source of organic aerosols, Adv. in Meteorol., Volume 2010, Article ID 939171, doi:10.1155/2010/939171, 2010.

 


 

The global marine organic aerosol budget is investigated by a 3-dimensional chemistry-transport model considering recently proposed parameterisations of the primary marine organic aerosol (POA) and secondary organic aerosol (SOA) formation from the oxidation of marine volatile organic compounds. MODIS and SeaWiFS satellite data of Chlorophyll-a and ECMWF solar incoming radiation, wind speed, and temperature are driving the oceanic emissions in the model. Based on the adopted parameterisations, the SOA and the submicron POA marine sources are evaluated at about 5 Tg yr

 

1 (1.5 Tg C yr1) and 7 to 8 Tg yr1 (4 Tg C yr1), respectively. The computed marine SOA originates from the dimethylsulfide oxidation (78%), the potentially formed dialkyl amine salts (21%), and marine hydrocarbon oxidation (0.1%). Comparison of calculations with observations indicates an additional marine source of soluble organic carbon that could be partially encountered by marine POA chemical ageing.

Primary and secondary organic marine aerosol and oceanic biological activity: recent results and new Primary and secondary organic marine aerosol and oceanic biological activity: recent results and new

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 672.69 kB

Rinaldi,M., S.Decesari, E. Finessi, L.Giulianelli, C.Carbone, S.Fuzzi, C.D. O'Dowd, D.Ceburnis and M.C. Facchini, Primary and secondary organic marine aerosol and oceanic biological activity: recent results and new perspectives for future studies, Adv. in Meteorol., Volume 2010, Article ID 310682, doi:10.1155/2010/243701, 2010.

 


 

One of the most important natural aerosol systems at the global level is marine aerosol that comprises both organic and inorganic components of primary and secondary origin. The present paper reviews some new results on primary and secondary organic marine aerosol, achieved during the EU project MAP (Marine Aerosol Production), comparing them with those reported in the recent literature.Marine aerosol samples collected at the coastal site ofMaceHead, Ireland, show a chemical composition trend that is influenced by the oceanic biological activity cycle, in agreement with other observations. Laboratory experiments show that seaspray  aerosol from biologically active sea water can be highly enriched in organics, and the authors highlight the need for further studies on the atmospheric fate of such primary organics. With regard to the secondary fraction of organic aerosol, the average  chemical composition and molecular tracer (methanesulfonic-acid, amines) distribution could be successfully characterized by adopting a multitechnique analytical approach.

 Nanoparticles in boreal forest and coastal environment: a comparison of observations and implicatio Nanoparticles in boreal forest and coastal environment: a comparison of observations and implicatio

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 1.15 MB

Lehtipalo, K., Kulmala, M., Sipilä, M., Petäjä, T., Vana, M., Ceburnis, D., Dupuy, R., and O'Dowd, C


Abstract.

 1

 

The detailed mechanism of secondary new particle formation in the atmosphere is still under debate. It is proposed that particle formation happens v a activation of 1–2 nm atmospheric neutral molecular clusters and/or large molecules. Since traditional instrumentation does not reach these sizes, the hypothesis has not yet been verified. By directly measuring particle size distributions down to mobility  diameters of about 1.3 nm with a pulse-height CPC, we  provide evidence of the nucleation mechanism in a coastal environment (Mace Head, Ireland) and in a boreal forest  (Hyyti¨al¨a, Finland). In both places neutral sub-3 nm condensation nuclei (nano-CN) were continuously present, even  when no new particle formation was detected. In Mace Head,  however, the concentration of the nano-CN was far too low to account for the particle formation rates during particle bursts. Thus the results imply that at coastal sites new particle formation initiates, as previously proposed, via homogenous nucleation  from biogenic iodine vapors. In contrast, activation  of pre-existing nano-CN remains a possible explanation in the boreal forest, but the observed concentrations are not the limiting factor for the particle formation events.

 

 

Aerosol properties associated with air masses arriving into the North East Atlantic during the 2008 Aerosol properties associated with air masses arriving into the North East Atlantic during the 2008

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 7.27 MB

Dall’Osto,M.,  D. Ceburnis, G. Martucci, J. Bialek, R. Dupuy, S. G. Jennings, H. Berresheim, J. C. Wenger, R. M. Healy, M. C. Facchini, M. Rinaldi, L. Giulianelli, E. Finessi, D. Worsnop, M. Ehn, J. Mikkil¨a, M. Kulmala, J. Sodeau, and C. D. O’Dowd, , Aerosol properties associated with air masses arriving into the North East Atlantic during the 2008 Mace Head EUCAARI intensive observing period: an overview Atmos. Chem. Phys., 10, 8413-8435, doi:10.5194/acp-10-8413-2010, 2010.


Abstract.

 

As part of the EUCAARI Intensive Observing Period, a 4-week campaign to measure aerosol physical, chemical and optical properties, atmospheric structure, and cloud microphysics was conducted from mid-May to mid-June, 2008 at the Mace Head Atmospheric Research Station, located

at the interface of Western Europe and the N. E. Atlantic and centered on the west Irish coastline. During the campaign, continental air masses comprising both young and aged continental plumes were encountered, along with polar, Arctic and tropical air masses. Polluted-continental aerosol

concentrations were of the order of 3000 cm

 

3, while background marine air aerosol concentrations were between 400– 600 cm3. The highest marine air concentrations occurred in polar air masses in which a 15 nm nucleation mode, with concentration of 1100 cm3, was observed and attributed to open ocean particle formation. Continental air submicron chemical composition (excluding refractory sea salt) was dominated by organic matter, closely followed by sulphate mass.  Although the concentrations and size distribution spectral shape were almost identical for the young and aged continental cases, hygroscopic growth factors (GF) and cloud condensation nuclei (CCN) to total condensation nuclei (CN) concentration ratios were significantly less in the younger pollution plume, indicating a more oxidized organic component to the aged continental plume. The difference in chemical composition and hygroscopic growth factor appear to result in a 40–50% impact on aerosol scattering coefficients and Aerosol Optical Depth, despite almost identical aerosol microphysical properties in both cases, with the higher valuesb been recorded for the more aged case. For the CCN/CN ratio, the highest ratios were seen in the more age plume. In marine air, sulphate mass dominated the sub-micron component, followed by water soluble organic carbon, which, in turn, was dominated by methanesulphonic acid (MSA). Sulphate concentrations were highest in marine tropical air – even higher than in continental air. MSA was present at twice the concentrations of previously-reported concentrations at the same location and the same season. Both continental and marine air exhibited aerosol GFs significantly less than ammonium sulphate aerosol pointing to a significant organic contribution to all air mass aerosol properties.

Effect of instrumental particle sizing resolution on the modelling of aerosol radiative parameters Effect of instrumental particle sizing resolution on the modelling of aerosol radiative parameters

Date added: 03/04/2010
Date modified: 03/04/2010
Filesize: 886.14 kB

Chamaillard, K., S. G.  Jennings, D. Ceburnis, Y.J. Yoon and C. O’Dowd.  Effect of instrumental particle sizing resolution on the modelling of aerosol radiative parameters. doi:10.1016/j.jqsrt.2009.11.005, Journal of Quantitative Spectroscopy and Radiative Transfer Volume 111, Issue 5, 2010, Pages 753-771


 

 Abstract.

 

A more realistic estimation of the scattering and hemispheric backscattering coefficients, ssp and sbsp, and their respective optical cross section, Csca and Cbk, of aerosol particles is presented on the basis of the exact resolution of the width of the size bins of the particle counter instruments when size distribution measurements are used, and, with the exact optical detector instruments ability. The scattering and hemispheric back scattering cross sections, Csca and Cbk, of the particles are averaged over the full size bins of the particle counter instrument, while the sequantities are usually estimated only on the value of the mean geometric diameter of each size bin. Six instruments, the APS, ASASP-X, DMPS,FSSP-100, ELPI, and SMPS frequently used in particle size distribution measurements are reviewed, for spherical sea-salt particles at a wavelength l=0.55 mm. The comparison using the conventional geometric mean diameter versus the use of the full size bin leads to large amount of errors for the optical cross section with non-negligible effects on their respective optical coefficients.The maximal accuracy expected for these optical quantities depend on the particle diameter as well as on the channel width of the instruments, and are also function of the angular detector probe used to measure them..

 


Global scale emission and distribution of sea-spray aerosol: Global scale emission and distribution of sea-spray aerosol:

Date added: 03/03/2010
Date modified: 03/03/2010
Filesize: 1.37 MB

Vignati,, E.,  M. C. Facchini, M. Rinaldi, C. Scannell, D. Ceburnis, J. Sciare, M. Kanakidou, S. Myriokefalitakis, F. Dentener and C. D. O’Dowd , Global scale emission and distribution of sea spray aerosol: sea-salt and organic enrichment, Atmos. Envniron. 44,, doi:10.1016/j.atmosenv.2009.11.013  , 2010.


Abstract

The chemical composition of marine aerosols as a function of their size is an important parameter for theevaluation of their impact on the global climate system. In this work we modelled fine p

article organic matter emitted by sea spray processes and its influence on the aerosol chemical properties at the global scale using the off-line global Chemistry-Transport Model TM5. TM5 is coupled to a microphysical aerosol dynamics model providing size resolved information on particle masses and numbers. The mass of the emitted sea spray particles is partitioned between water insoluble organic matter (WIOM) and sea salt components in the accumulation mode using a function that relates the emitted organic fraction to the surface ocean chlorophyll-a concentrations. The global emission in the sub-micron size range of  organic matter by sea spray process is 8.2 Tg yr1, compared to 24 Tg fine yr1 sea-salt emissions. When  the marine sources are included, the concentrations of modelled primary particulate organic matter (POM) increase mainly over the oceans. The model predictions of WIOM and sea salt are evaluated  against measurements carried out at Mace Head (Northern Hemisphere) and Amsterdam Island  (Southern Hemisphere), showing that in clean marine conditions WIOM marine emissions contribute  significantly to POM values.  
fine particle organic matter emitted by sea spray processes and its influence on the aerosol chemical properties at the global scale using the off-line global Chemistry-Transport Model TM5. TM5 is coupled to a microphysical aerosol dynamics model providing size resolved information on particle masses and numbers. The mass of the emitted sea spray particles is partitioned between water insoluble organic matter (WIOM) and sea salt components in the accumulation mode using a function that relates the emitted organic fraction to the surface ocean chlorophyll-a concentrations. The global emission in the sub-micron size range of  organic matter by sea spray process is 8.2 Tg yr1, compared to 24 Tg fine yr1 sea-salt emissions. When  the marine sources are included, the concentrations of modelled primary particulate organic matter (POM) increase mainly over the oceans. The model predictions of WIOM and sea salt are evaluated  against measurements carried out at Mace Head (Northern Hemisphere) and Amsterdam Island  (Southern Hemisphere), showing that in clean marine conditions WIOM marine emissions contribute  significantly to POM values.
fine particle organic matter emitted by sea spray processes and its influence on the aerosol chemical properties at the global scale using the off-line global Chemistry-Transport Model TM5. TM5 is coupled to a microphysical aerosol dynamics model providing size resolved information on particle masses and numbers. The mass of the emitted sea spray particles is partitioned between water insoluble organic matter (WIOM) and sea salt components in the accumulation mode using a function that relates the emitted organic fraction to the surface ocean chlorophyll-a concentrations. The global emission in the sub-micron size range of  organic matter by sea spray process is 8.2 Tg yr1, compared to 24 Tg fine yr1 sea-salt emissions. When  the marine sources are included, the concentrations of modelled primary particulate organic matter (POM) increase mainly over the oceans. The model predictions of WIOM and sea salt are evaluated  against measurements carried out at Mace Head (Northern Hemisphere) and Amsterdam Island  (Southern Hemisphere), showing that in clean marine conditions WIOM marine emissions contribute  significantly to POM values.

Observations of high concentrations of I2 and IO in coastal air Observations of high concentrations of I2 and IO in coastal air

Date added: 03/03/2010
Date modified: 03/03/2010
Filesize: 299.46 kB

Huang, R.-J., K. Seitz, T. Neary, C. D. O’Dowd, U. Platt, and T. Hoffmann, Observations of high concentrations of I2 and IO in coastal air supporting iodine-oxide driven coastal new particle formation . Geophys. Res. Letts, VOL. 37, L03803, doi:10.1029/2009GL041467, 2010


Abstract.

 Theoretical studies have predicted that concentrations of gaseous I2 and IO of the order of 80–100 ppt and 40–50 ppt, respectively, are required in coastal air to account for photochemically-driven coastal new-particle formation events to occur. However, measurements reported to date  (i.e., 20 ppt I2,  10 ppt IO) have not supported the required model predictions. Here, we present measurements of high concentrations of I2 and IO n N.E. Atlantic marine air on the west coast of Ireland. The maximum mixing ratios of daytime I2 and IO over the seaweed beds during low tide were 302 ppt and 35 ppt, respectively. The I2 distribution=was rather inhomogeneous, even at the inter-tidal zone, but closely related to the macroalgae biomass  bundance. New particle formation bursts were frequently observed during daytime hours with the concentrations up to 4.5  105 particles cm3 during low-tide conditions, and the concentrations of ultra-fine particles were positively correlated with the IO concentrations. Considering the constraints set out in theoretical studies for new particle formation via condensation of condensable iodine oxide vapours, the results reported here clearly demonstrate that the molecular iodine and iodine monoxide concentrations in coastal air are sufficient to meet the theoretical precursor concentrations required to drive intensive coastal newparticle formation from higher order condensable iodine oxides.

The spatial distribution of the reactive iodine species IO from simultaneous active and passive DOAS The spatial distribution of the reactive iodine species IO from simultaneous active and passive DOAS

Date added: 03/02/2010
Date modified: 03/03/2010
Filesize: 1.87 MB

Seitz, K.,  J. Buxmann, D. Pöhler, T. Sommer, J. Tschritter, T. Neary, C. O’Dowd, and U. Platt,  The spatial distribution of the reactive iodine species IO from simultaneous active and passive DOAS observations, Atmos. Chem. Phys., 10, 2117–2128, 2010


 

Abstract. :

We present investigations of the reactive iodine species (RIS) IO, OIO and I
2 in a coastal region from a field  campaign simultaneously employing active long path differential optical absorption spectroscopy (LP-DOAS) as well as passive multi-axis differential optical absorption spectroscopy (MAX-DOAS). The campaign took place at the Martin Ryan Institute (MRI) in Carna, County Galway at the IrishWest Coast about 6 km south-east of the atmospheric research station Mace Head in summer 2007. In order to study the horizontal distribution of the trace gases of interest, we established two almost parallel active LP-DOAS light paths, the shorter of 1034m length just crossing the intertidal area, whereas the longer one of 3946m length also crossed open water during periods of low tide. In addition we operated two passive Mini-MAX-DOAS instruments with the same viewing direction. While neither OIO nor I2 could be unambiguously identified with any of the instruments, IO could be detected with active as well as passive DOAS. The IO column densities seen at both active LP-DOAS light paths are almost the same. Thus it can be concluded that coastal IO is almost exclusively located in the intertidal area, where we detected mixing ratios of up to 29±8.8 ppt (equivalent to pmol/mol). Nucleation events with particle concentrations of 106 cm3 particles were observed each day correlating with high IO mixing ratios. Therefore we feel that our detected IO concentrations confirm the results of model studies, which state that in order to explain such particle bursts, IO mixing ratios of 50 to 100 ppt in so called “hot-spots” are required.

On the representativeness of coastal aerosol studies to open ocean On the representativeness of coastal aerosol studies to open ocean

Date added: 02/12/2010
Date modified: 02/13/2010
Filesize: 1.01 MB

Rinaldi, M., M. C. Facchini, S. Decesari, C. Carbone, E. Finessi, M. Mircea, S. Fuzzi, D. Ceburnis, M. Ehn, M. Kulmala, G. de Leeuw and C. D. O’Dowd, On the representativeness of coastal aerosol studies to open ocean studies: Mace Head – a case study, Atmos. Chem. & Phys., 9, 9635-9646, 2009


Abstract.  

A unique opportunity arose during the MAP project to compare open ocean aerosol measurements with those undertaken at the Mace Head Global Atmosphere Watch Station, a station used for decades for aerosol process research and long-term monitoring. The objective of the present study is to demonstrate that the key aerosol features and processes observed at Mace Head are characteristic of the open ocean, while acknowledging and allowing for spatial and temporal gradients. Measurements were conducted for a 5-week period at Mace Head and offshore, on the Research Vessel Celtic Explorer, in generally similar marine air masses, albeit not in connected-flow scenarios. The results of the study indicate, in terms of aerosol number size distribution, higher nucleation mode particle concentrations at Mace Head than offshore, pointing to a strong coastal  source of new particles that is not representative of the open ocean. The Aitken mode exhibited a large degree of similarity, with no systematic differences between Mace Head and the open ocean, while the  zcumulation mode showed averagely 35% higher concentrations at Mace Head. The higher accumulation mode concentration can be attributed equally to cloud processing and to a coastal enhancement in concentration. Chemical analysis showed similar or even higher offshore concentrations for dominant species, such as nss-SO
2 4 , WSOC, WIOC and MSA. Sea salt concentration differences determined a 40% higher supermicron mass at Mace Head, although this difference can be attributed to a higher  wind speed at Mace Head during the parison period.        Moreover, the relative chemical composition as a function of size illustrated remarkable  similarity. While differences to varying degrees were observed between offshore and coastal  measurements, no convincing evidence was found of local  coastal effects, apart from nucleation mode aerosol, thus confirming the integrity of previously reported marine aerosol characterisation studies at Mace Head.

Atmospheric Composition Change – Global and Regional Air Quality Atmospheric Composition Change – Global and Regional Air Quality

Date added: 11/11/2009
Date modified: 11/11/2009
Filesize: 9.8 MB

Monks, P.S., C. Granier, S. Fuzzi, A. Stohl, M. Williams, H. Akimoto, M. Amman, A. Baklanov, U. Baltensperger, I. Bey, N. Blake, R.S. Blake, K. Carslaw, O.R. Cooper, F. Dentener, D. Fowler, E. Fragkou, G. Frost, S. Generoso, P. Ginoux, V. Grewe, A. Guenther, H.C. Hansson, S. Henne, J. Hjorth, A. Hofzumahaus, H. Huntrieser, I.S.A. Isaksen, M.E. Jenkin, J. Kaiser, M. Kanakidou, Z. Klimont, M. Kulmala, P. Laj, M.G. Lawrence, J.D. Lee, C. Liousse, M. Maione, G. McFiggans, A. Metzger, A. Mieville, N. Moussiopoulos, J.J. Orlando, C. O'Dowd, P.I. Palmer, D.D. Parrish, A. Petzold, U. Platt, U. Poeschl, A.S.H. Prévôt, C.E. Reeves, S. Reimann, Y. Rudich, K. Sellegri, R. Steinbrecher, D. Simpson, H. ten Brink, J. Theloke, G.R. van der Werf, R. Vautard, V. Vestreng, Ch. Vlachokostas and R. vonGlasow, Atmospheric Composition Change – Global and Regional Air Quality, Atmos. Environ.,  doi:10.1016/j.atmosenv.2009.08.021  , 2009


Abstract.

Air quality transcends all scales with in the atmosphere from the local to the global with handovers and feedbacks at each scale interaction. Air quality has manifold effects on health, ecosystems, heritage and climate. In this review the state of scientific understanding in relation to global and regional air quality is outlined. The review discusses air quality, in terms of emissions, processing and transport of trace gases and aerosols. New insights into the characterization of both natural and anthropogenic emissions are reviewed looking at both natural (e.g. dust and lightning) as well as plant emissions. Trends in anthropogenic emissions both by region and globally are discussed as well as biomass burning emissions. In terms of chemical processing the major air quality elements of ozone, non-methane hydrocarbons, nitrogen oxides and aerosols are covered. A number of topics are presented as a way of integrating the process view into the atmospheric context; these include the atmospheric oxidation efficiency, halogen and HOx chemistry, nighttime chemistry, tropical chemistry, heat waves, megacities, biomass burning and the regional hot spot of the Mediterranean. New findings with respect to the transport of pollutants across the scales are discussed, in particular the move to quantify the impact of long-range transport on regional air quality. Gaps and research questions that remain intractable are identified. The review concludes with a focus of research and policy questions for the coming decade. In particular, the policy challenges for concerted air quality and climate change policy (co-benefit) are discussed.

Atmospheric Composition Change: Ecosystems - Atmosphere interactions Atmospheric Composition Change: Ecosystems - Atmosphere interactions

Date added: 11/11/2009
Date modified: 11/11/2009
Filesize: 7.78 MB

Fowler, D., K. Pilegaard, M.A. Sutton, P. Ambus, M. Raivonen, J. Duyzer, D. Simpson, H. Fagerli, S. Fuzzi, J.K. Schjoerring, C. Granier, A. Neftel, I.S.A. Isaksen, P. Laj, M.Maione, P.S. Monks, J. Burkhardt, U. Daemmgen, J. Neirynck, E. Personne, R. Wichink-Kruit, K. Butterbach-Bahl, C. Flechard, J.P. Tuovinen, M. Coyle, G. Gerosa, B. Loubet, N. Altimir, L. Gruenhage, C. Ammann, S. Cieslik, E. Paoletti, T.N. Mikkelsen, H. Ro-Poulsen, P. Cellier, J.N. Cape, L. Horváth, F. Loreto, Ü. Niinemets, P. I. Palmer, J.Rinne, P. Misztal, E. Nemitz, D. Nilsson, S. Pryor, M.W. Gallagher, T. Vesala, U. Skiba, N. Brüeggemann, S. Zechmeister-Boltenstern, J. Williams, C. O’Dowd, M. C. Facchini, G. de Leeuw, A. Flossman, N. Chaumerliac, J.W. Erisman, Atmospheric Composition Change: Ecosystems - Atmosphere interactions, Atmos. Environ., doi:10.1016/j.atmosenv.2009.07.068,  2009


Abstract.

Ecosystems and the atmosphere: This review describes the state of understanding the processes involved in the exchange of trace gases and aerosols between the earth’s surface and the atmosphere. The gases covered include NO, NO2, HONO, HNO3, NH3, SO2, DMS, Biogenic VOC, O3, CH4, N2O and particles in the size range 1 nm–10 mmincluding organic and inorganic chemical species. The main focus of the reviewis on the exchange between terrestrial ecosystems, both managed and natural and the atmosphere, although some new developments in ocean–atmosphere exchange are included. The material presented is biased towards the last decade, but includes earlier work, where more recent developments are limited or absent.  New methodologies and instrumentation have enabled, if not driven technical advances in measurement. These developments have advanced the process understanding and upscaling of fluxes, especially for particles, VOC and NH3. Examples of these applications include mass spectrometric methods, such as  Aerosol Mass Spectrometry (AMS) adapted for field measurement of atmosphere–surface fluxes using micrometeorological methods for chemically resolved aerosols. Also briefly described are some advances in theory and techniques in micrometeorology. For some of the compounds there have been paradigm shifts in approach and application of both techniques and assessment. These include flux measurements over marine surfaces and urban areas using micrometeorological methods and the up-scaling of flux measurements using aircraft and satellite remote sensing. The application of a flux-based approach in assessment of O3 effects on vegetation at regional scales is an important policy linked development secured through improved quantification of fluxes. The coupling of monitoring, modelling and intensive flux measurement at a continental scale within the NitroEurope network represents a quantum development in the application of research teams to address the underpinning science of reactive nitrogen in the cycling between ecosystems and the atmosphere in Europe. Some important developments of the science have been applied to assist in addressing policy questions, which have been the main driver of the research agenda, while other developments in understanding have not been applied to their wider field especially in chemistry-transport models through deficiencies in obtaining appropriate data to enable application or inertia within the modelling community. The paper identifies applications, gaps and research questions that have remained intractable at least since 2000 within the specialized sections of the paper, and where possible these have been focussed on research questions for the coming decade.

 

 

Aerosol Optical Depth in Clean and Polluted Northeast Atlantic Air Aerosol Optical Depth in Clean and Polluted Northeast Atlantic Air

Date added: 11/06/2009
Date modified: 11/06/2009
Filesize: 250.56 kB

Mulcahy, J. P., C. D. O’Dowd, and S. G. Jennings (2009), Aerosol optical depth in clean marine and continental northeast Atlantic air, 114, D20204, doi:10.1029/2009JD011992. J. Geophys. Res.


Abstract.

The aerosol optical depth (AOD) and A ° ngstro¨m exponent for the period 2002–2004 is evaluated for clean marine and continentally influenced air masses over the northeast Atlantic region. Measurements were carried out at the Mace Head atmospheric research station on the west coast of Ireland using a precision filter radiometer which measures the aerosol optical depth at four wavelengths centered at 368, 412, 500, and 862 nm. The clean marine AOD at 500 nm is characterized by a mean value of 0.14 ±0.06, exhibiting relatively small temporal variability. The A ° ngstro¨m exponent was less than 1 for the majority of cases, having an average value of 0.40 ± 0.29 in clean marine conditions. The latter is consistent with the presence of relatively large supermicron particles, such as sea salt dominating the marine aerosol size distribution. The A ° ngstro¨m exponent shows a distinct seasonal cycle in clean marine air, with maximum values being derived in the summer months and minimum values in the winter. In continental air masses, while the range and standard deviation of the AOD is larger than in clean marine conditions, the overall mean AOD (

t500 = 0.19 ± 0.12) is comparable with the clean marine AOD. The continental A ° ngstro¨m exponent is larger, having a mean value of 1.07 ± 0.32. This is attributed to a dominating accumulation mode in the presence of urban-industrial aerosol particles originating mainly from continental Europe. These results demonstrate how the natural marine AOD can rival polluted AOD over the northeast Atlantic region and highlight the importance of the natural marine aerosol contribution over oceans.

Description of a biofluorescence optical particle counter Description of a biofluorescence optical particle counter

Date added: 05/09/2009
Date modified: 07/23/2009
Filesize: 371.82 kB
Ryan, O., R. Greaney, S.G. Jennings and C.D. O’Dowd, Description of a biofluorescence optical particle counter J.Q.S.R.T., DOI: 10.1016/j.jqsrt.2009.01.033, 2009

Abstract

 

A bioaerosol fluorescence detection system is being constructed using an ellipsoid reflector-based optical particle counter. The flux measuring device is to size submicron marine spray aerosol particles smaller than 100nm in diameter. It will simultaneously non-destructively excite and detect fluorescence from organic matter contained in the aerosol. Chlorophyll-a is the primary fluorophor target, used as a marker for detecting phytoplankton (or derivatives thereof) in the particles. Particles have been sized to 500nm in diameter and fluorescence detection testing is underway. The device will aid the quantification and identification of this organic material contained in marine spray aerosols, providing improved inputs into climate models and air quality assessments.

EUCAARI: European Integrated project on Aerosol Cloud Climate and Air Quality interactions EUCAARI: European Integrated project on Aerosol Cloud Climate and Air Quality interactions

Date added: 04/28/2009
Date modified: 11/01/2009
Filesize: 670.53 kB

Kulmala, M., A. Asmi, H. K. Lappalainen, K. S. Carslaw, U. P¨oschl, U. Baltensperger, Ø. Hov, J.-L. Brenquier, S. N. Pandis, M. C. Facchini, H.-C. Hansson, A. Wiedensohler, and C. D. O’Dowd. Introduction: European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) – Integrating aerosol research from nano to global scales, Atmos. Chem. & Phys., 9, 2825-2841, 2009.


Abstract

 

The European Aerosol Cloud Climate and Air Quality Interactions project EUCAARI is an EU Research
Framework 6 integrated project focusing on understanding the interactions of climate and air pollution. EUCAARI works in an integrative and multidisciplinary way from nano to global scale. EUCAARI brings together several leading European research groups, state-of-the-art infrastructure and some key scientists from third countries to investigate the role of aerosol on climate and air quality. Altogether 48 partners from 25 countries are participating in EUCAARI.  
During the first 16 months EUCAARI has built operational systems, e.g. established pan-European measurement network for Lagrangian studies and four stations in developing countries. Also an improved understanding of nanoscale processes (like nucleation) has been implemented in global models. Here we present the research methods, organisation, operations and first results of EUCAARI.

Dual pathways for atmospheric sulfuric acid-water nucleation mechanisms Dual pathways for atmospheric sulfuric acid-water nucleation mechanisms

Date added: 04/08/2009
Date modified: 11/01/2009
Filesize: 988.72 kB
Laaksonen, A.,  M. Kulmala, T. Berndt, F. Stratmann, S. Mikkonen, A. Ruuskanen, K.E.J. Lehtinen, M. Dal Maso, P. Aalto, T. Petäjä, I. Riipinen, R. Janson, F. Arnold, M. Hanke, J.Ücker, B. Umann, K. Sellegri,  C.D. O’Dowd, Y. Viisanen, Dual pathways for atmospheric sulfuric acid-water nucleation mechanisms,, Atmos. Chem. Phys.,  8, 7255–7264, 2008.

Abstract


Atmospheric new particle formation is generally thought to occur due to homogeneous or ion-induced nucleation of sulphuric acid. We compare ambient nucleation rates with laboratory data from nucleation experiments involving either sulphuric acid or oxidized SO2. Atmospheric nucleation occurs at H2SO4 concentrations 2–4 orders of magnitude lower than binary or ternary nucleation rates of H2SO4 produced from a liquid reservoir, and atmospheric H2SO4 concentrations are very well replicated in the SO2 oxidation experiments. We hypothesize these features to be due to the formation of free HSO5 radicals in pace with H2SO4 during the SO2 oxidation. We suggest that at temperatures above 250K these radicals produce nuclei of new aerosols much more efficiently than H2SO4. These nuclei are activated to further growth by H2SO4 and possibly other trace species. However, at lower temperatures the atmospheric relative acidity is high enough for the H2SO4–H2O nucleation to dominate.

Iodine dioxide nucleation simulations in coastal and remote marine environments Iodine dioxide nucleation simulations in coastal and remote marine environments

Date added: 04/08/2009
Date modified: 07/28/2009
Filesize: 685.8 kB
Vuollekoski, H., V.-M. Kerminen, T. Anttila, S.-L. Sihto, M. Vana, M. Ehn, H. Korhonen, G. McFiggans, C. D. O’Dowd and M. Kulmala,,  Iodine dioxide nucleation simulations in coastal and remote marine environments, J. Geophys. Res., 114, D02206, doi:10.1029/2008JD010713, 2008

Abstract

 

Aerosol dynamical box model simulations of coastal new particle formation were performed in order to investigate the nucleation and growth mechanisms in this environment. In the simulations the nucleating vapor was assumed to be iodine dioxide (OIO). Both Eulerian and Lagrangian type simulations were made and compared with observations. We tested three nucleation mechanisms: kinetic nucleation of OIO (K  [OIO]2), activation of clusters by OIO (A  [OIO]) and sulphuric acid-induced activation of clusters containing OIO (B  [OIO]  [H2SO4]). All the nucleation mechanisms provided reasonable results, although the growth of particles due to condensation is inadequate in kinetic nucleation cases as compared with experimental measurements. Growth of newly formed particles could be assisted by any low-volatility vapors should their concentration exceed 109 cm3. Using the obtained values of coefficients K, A, and B we found that nucleation driven by iodine compounds in remote marine areas is possible, but by OIO and H2SO4 alone, only a minor fraction of newly formed particles is likely to reach detectable sizes. Owing to the scavenging by coagulation with background aerosol particles, few of them will likely reach climatically relevant sizes by acting as seed particles for other low-volatility vapors. In order to elucidate the significance of our results, more detailed measurements of OIO source and photolysis rates, dimensions of precursor areas, and particle chemical composition are needed.

Primary submicron marine aerosol dominated by insoluble organic colloids and aggregates Primary submicron marine aerosol dominated by insoluble organic colloids and aggregates

Date added: 04/08/2009
Date modified: 11/01/2009
Filesize: 220.61 kB
Facchini, M.C.,  M. Rinaldi, S. Decesari, C. Carbone, E. Finessi, M. Mircea, S. Fuzzi, D. Ceburnis, R.  Flanagan, E. D. Nillsson, G.  de Leeuw, M. Martino,  J. Woeltjen and C.D. O’ Dowd, Primary submicron marine aerosol dominated by insoluble organic colloids and aggregates,, Geophys. Res. Letts., doi:10.1029/2008GL034210, 2008.

Abstract

 

The chemical properties of sea-spray aerosol particles produced by artificially generated bubbles using oceanic waters were investigated during a phytoplankton bloom in the North Atlantic. Spray particles exhibited a progressive increase in the organic matter (OM) content from 3 ± 0.4% up to 77 ± 5% with decreasing particle diameter from 8 to 0.125 mm. Submicron OM was almost entirely water insoluble (WIOM) and consisted of colloids and aggregates exuded by phytoplankton. Our observations indicate that size dependent transfer of sea water organic material to primary marine particles is mainly controlled by the solubility and surface tension properties of marine OM. The pattern of WIOM and sea-salt content in the different size intervals observed in bubble bursting experiments is similar to that measured in atmospheric marine aerosol samples collected during periods of high biological activity. The results point to a WIOM/sea-salt fingerprint associated with submicron primary marine aerosol production in biologically rich waters.

An important source of marine secondary organic aerosol from biogenic amines, An important source of marine secondary organic aerosol from biogenic amines,

Date added: 04/08/2009
Date modified: 07/23/2009
Filesize: 548.79 kB

Facchini, M.C., S. Decesari, M. Rinaldi, C. Carbone, E. Finessi, M. Mircea, S. Fuzzi, F. Moretti, E. Tagliavini, D. Ceburnis and C. D. O’Dowd, An important source of marine secondary organic aerosol from biogenic amines, Env. Sci. & Tech., 10.1021/es8018385, 2008


Abstract

 

Relevant concentrations of dimethyl- and diethylammonium salts(DMA+andDEA+)weremeasured in submicrometer marine aerosol collected over the North Atlantic during periods of high biological activity (HBA) in clean air masses (median concentration (minimum-maximum))26 (6-56) ngm-3). Much lower concentrations were measured during periods of low biological activity (LBA): 1 (<0.4-20) ng m-3 and when polluted air masses were advected to the sampling site: 2 (<0.2-24) ngm-3.DMA+ andDEA+ are the most abundant organic species, second only to MSA, detected in fine marine particles representing on average 11% of the secondary organic aerosol (SOA)fraction and a dominant part (35% on average) of the watersoluble organic nitrogen (WSON). Several observations support the hypothesis that DMA+ and DEA+ have a biogenic oceanic source and are produced through the reaction of gaseous amines with sulfuric acid or acidic sulfates. Moreover, the water-soluble fraction of nascent marine aerosol particles produced by bubble-bursting experiments carried out in parallel to ambient aerosol sampling over the open ocean showed WSON, DMA+, and DEA+ concentrations always below the detection limit, thus excluding an important primary sea spray source.

 

Whitecap Coverage: Measurements from the North Atlantic Whitecap Coverage: Measurements from the North Atlantic

Date added: 12/10/2008
Date modified: 11/01/2009
Filesize: 198.39 kB
Callaghan, A., G. de Leeuw, L. Cohen, C.D. O’Dowd, Oceanic Whitecap Coverage: Measurements from the North Atlantic, Geophys. Res. Letts., doi:10.1029/2008GL036165, 2008

Abstract

 

Sea surface images obtained during the 2006 Marine Aerosol Production (MAP) campaign in the North East Atlantic were analysed for values of percentage whitecap coverage (W). Values of Ware presented for wind speeds up to circa 23 m s-1. The W data were divided into two overlapping groups and a piecewise,  wind-speed-only parameterization of W is proposed that is valid for wind speeds between 3.70 m s-1 and 23.09 m s-1. Segregation of data points based upon a 2.5 hour wind history acted to decrease data scatter at wind speeds above approximately 9.25 m s-1. At these wind speeds W values were greater for decreasing wind speeds than for increasing wind speeds. No clear wind history effect was observed at wind speeds below 9.25 m s-1

New Directions: Organic matter contribution to marine aerosols and cloud condensation nuclei New Directions: Organic matter contribution to marine aerosols and cloud condensation nuclei

Date added: 10/01/2008
Date modified: 07/28/2009
Filesize: 178.38 kB

Baerbel Langmann, Claire Scannell, Colin O'Dowd, New Directions: Organic matter contribution to marine aerosols and cloud condensation nuclei, Atmospheric Environment, Volume 42, Issue 33, October 2008, Pages 7821-7822, ISSN 1352-2310, DOI: 10.1016/j.atmosenv.2008.09.002.


Abstract

 

Aerosols in the marine atmosphere influence solar irradiation over the world’s ocean directly by backscattering incoming solar radiation and indirectly, by forming cloud condensation nuclei (CCN) thereby affecting the cloud albedo. Charlson et al. (1987) suggested the existence of a feedback mechanism between climate change and the flux of oceanic dimethyl sulfide (DMS), commonly known as the CLAWhypothesis after the four founding authors. According to this hypothesis, DMS produced by marine phytoplankton is ventilated into the marine boundary layer (MBL) and ultimately oxidised to sulfate aerosol which form CCNs.

Highlights of fifty years of atmospheric aerosol research at Mace Head Highlights of fifty years of atmospheric aerosol research at Mace Head

Date added: 09/23/2008
Date modified: 07/23/2009
Filesize: 2.08 MB

O’Connor, T.C., S.G. Jennings, and C.D. O’Dowd, Highlights from 50 years of Aerosol Measurements at Mace Head, Atmos. Res., 90, 338–355, doi:10.1016/j.atmosres.2008.08.014, 2008.


Abstract

 

This paper summarises the development and principal results of fifty years of research on aerosols in the marine atmosphere at Mace Head Atmospheric Research Station on the west coast of Ireland. It concentrates on the sources, physico-chemical properties, number and mass concentrations, size range, volatility and chemical composition of aerosols in different air masses. It also examines optical properties of the aerosols and their long-range transport.

Influence of an increased sea surface temperature on North Atlantic cyclones Influence of an increased sea surface temperature on North Atlantic cyclones

Date added: 09/23/2008
Date modified: 07/23/2009
Filesize: 2.79 MB

Semmler, S. Varghese, R. McGrath, P. Nolan, S. Wang, P. Lynch, C. O'Dowd, Influence of an increased sea surface temperature on North Atlantic cyclones, J. Geophys. Res, D02107, doi/2006JD008213, 2008.


Abstract

 

The influence of an increased sea surface temperature (SST) on the frequency and intensity of cyclones over the North Atlantic is investigated using two data sets from simulations with the Rossby Centre regional climate model RCA3. The model domain comprises large parts of the North Atlantic and the adjacent continents. RCA3 is driven by reanalysis data for May to December 1985–2000 at the lateral and lower boundaries, using SST and lateral boundary temperatures. A realistic interannual variation in tropical storm and hurricane counts is simulated. In an idealized sensitivity experiment, SSTs and boundary condition temperatures at all levels are increased by 1 K to ensure that we can distinguish the SST from other factors influencing the development of cyclones. An increase in the count of strong hurricanes is simulated. There is not much change in the location of hurricanes. Generally weaker changes are seen in the extratropical region
and for the less extreme events. Increases of 9% in the count of extratropical cyclones and 39% in the count of tropical cyclones with wind speeds of at least 18 m/s are found.

Organic matter contribution to marine aerosols and cloud condensation nuclei Organic matter contribution to marine aerosols and cloud condensation nuclei

Date added: 09/23/2008
Date modified: 07/23/2009
Filesize: 158.68 kB

Baerbel Langmann, Claire Scannell, Colin O'Dowd, New Directions: Organic matter contribution to marine aerosols and cloud condensation nuclei, Atmospheric Environment, Volume 42, Issue 33, October 2008, Pages 7821-7822, ISSN 1352-2310, DOI: 10.1016/j.atmosenv.2008.09.002.


Abstract

 

Aerosols in the marine atmosphere influence solar irradiation over the world's ocean directly by backscattering incoming solar radiation and indirectly, by forming cloud condensation nuclei (CCN) thereby affecting the cloud albedo. Charlson et al. (1987) suggested the existence of a feedback mechanism between climate change and the flux of oceanic dimethyl sulfide (DMS), commonly known as the CLAW hypothesis after the four founding authors. According to this hypothesis, DMS produced by marine phytoplankton is ventilated into the marine boundary layer (MBL) and ultimately oxidised to sulfate aerosol which form CCNs.

The change in cloud albedo results in a global temperature perturbation affecting the productivity of the marine biosphere and hence the concentration of oceanic DMS. The authors assumed that non-sea salt (nss) sulfate aerosol as oxidation product of DMS is the major source of CCN over the oceans thereby disregarding the potential of other chemical components of the submicron marine aerosol like sea salt and water soluble and water insoluble organic carbon (OC) to form CCNs. Since the publication of the CLAW hypothesis it has been difficult to prove or disprove the idea, however several studies (e.g. Woodhouse et al., 2008) have elucidated that DMS flux in the MBL alone cannot explain new particle and CCN formation.

In recent years, the role of natural organic aerosol in the marine environment has received increasing attention. Measurements indicate that the increase of the marine biological activity is accompanied by a considerable increase of the contribution of OC to the submicron marine aerosol (e.g. O'Dowd et al., 2004) exceeding the mass fraction of nss sulfate by a factor of more than two. OC aerosols are partly primary aerosols (POC) which are directly released from the ocean and partly secondary aerosols (SOC) which form in the atmosphere through chemical reactions of reactive gases released at the ocean surface. CCNs formed from POC and reactive gases like isoprene should be available much closer to areas with increased marine biological activity than CCNs formed from nss sulfate. Meskhidze and Nenes (2006) argued that SOC aerosols can act as efficient CCNs in the Southern Ocean, even though the authors had to revise their estimates of oceanic isoprene fluxes. Roelofs (2008) showed in a global model study that OC aerosols significantly contribute to marine cloud optical properties and seasonality by estimating a global annual flux of marine organic matter of about 75 Tg C yr−1 (corresponding to 90–135 Tg OC yr−1 depending on the applied conversion factor) whereas Spracklen et al. (2008) provide a global annual oceanic OC emission estimate of around 8 Tg OC yr−1. The very different approaches used by the authors lead to a one order of magnitude difference in the marine OC emissions estimates. As measurements are generally limited spatially and temporally and are only available for selected gases or aerosols, globally, the role of the ocean as a source of photochemical active gases and aerosols remains unclear.

We would like to contribute to an improved understanding of marine OC emissions by presenting a global annual marine OC flux estimate based on a different approach. A combined organic–inorganic submicron sea–spray source function (O'Dowd et al., 2008) is applied globally, where we make use of chlorophyll-a concentration obtained from MODIS Aqua and Terra satellite and wind speed obtained from SeaWinds on QuikSCAT as monthly average input information. The only difference to O'Dowd et al. (2008) is the use of a revised relationship between organic mass and chlorophyll concentration in the current estimate (organic mass [%] = 49.129 × chlorophyll [mg m−3]) because of recent corrections of the chemical analysis. The resulting marine flux of submicron OC aerosols is 2.3 Tg OC yr−1 for 2003 and 2.8 Tg C yr−1 for 2006, with a spatial distribution as shown in Fig. 1. As the submicron OC aerosols are likely internally mixed with sea-salt and therefore are already hygroscopic, they can act as sites for biogenic SOC condensation making them more active as CCN. Estimates for the very high latitudes should be regarded with caution because the satellite sensors have a large margin of errors in these regions. Our estimate of the global annual marine OC flux is in the range of that published by Spracklen et al. (2008), but approximately a factor of 3 lower as only submicron particles are considered here. The global distribution of the marine OC flux by Spracklen et al. (2008) follows the global distribution of chlorophyll-a, whereas high wind speed in the approach presented here leads to increased marine OC emissions in particular in the region of the Antarctic circumpolar current, the North Atlantic and the North Pacific Ocean and considerably lower emissions in the tropics and subtropics where wind speed is generally lower. Further measurements preferably in remote oceanic regions, and measurements and modelling studies on the mechanisms of marine OC production are needed to illuminate the nature and role of marine OC aerosols and their potential to act as CCNs.

Significant enhancement of aerosol optical depth in marine air under high wind conditions Significant enhancement of aerosol optical depth in marine air under high wind conditions

Date added: 09/12/2008
Date modified: 07/06/2009
Filesize: 479.23 kB

Mulcahy, J. P., C. D. O'Dowd, S. G. Jennings, and D. Ceburnis (2008), Significant enhancement of aerosol optical depth in marine air under high wind conditions, Geophys. Res. Lett., 35, L16810, doi:10.1029/2008GL034303.


Abstract


The relationship between the AOD and wind speed (U), obtained at the Mace Head atmospheric research station, is determined for clean marine (Northeast Atlantic) conditions under steady-state wind speed scenarios. AOD measurements were made under much higher wind speed conditions (up to 18 m s−1) than hitherto measured. The AOD is found to be approximately dependent on U2, with a high correlation (r2 = 0.97) determined at all measured wavelengths of 862 nm, 500 nm, 412 nm and 368 nm. A corresponding anti-correlation was observed between the Ångström exponent and wind speed (r2 = 0.93). The results illustrate that under moderate-to-high wind conditions, sea-spray AOD can rival or even exceed that associated with pollution plumes over oceanic regions and can potentially contribute to radiative, dynamical and biogeochemical feedback processes associated with future climate change.

 

Role of the Volatile Fraction of Submicron Marine Aerosol on its Hygroscopic Properties Role of the Volatile Fraction of Submicron Marine Aerosol on its Hygroscopic Properties

Date added: 09/12/2008
Date modified: 07/06/2009
Filesize: 257.12 kB

Sellegri, K., P. Villani, D. Picard, R. Dupuy, C. O’Dowd and P. Laj, Role of the Volatile Fraction of Submicron Marine Aerosol on its Hygroscopic Properties, Atmos. Res., in press, 2008.


Abstract


The hygroscopic growth factor (HGF) of 85 nm and 20 nm marine aerosol particles was measured during January 2006 for a three-week period within the frame of the EU FP6 project MAP (Marine Aerosol Production) winter campaign at the coastal site of Mace Head, using the TDMA technique. The results are compared to aerosol particles produced in a simulation tank by bubbling air through sea water sampled near the station, and through synthetic sea water (inorganic salts). This simulation is assimilated to primary production. Aitken and mode particles (20 nm) and accumulation mode particles (85 nm) both show HGF of 1.92 and 2.01 for particles generated through bubbling in natural and artificial sea water respectively. In the Aitken mode, the marine particles sampled in the atmosphere shows a monomodal HGF slightly lower than the one measured for sea salt particles artificially produced by bubble bursting in natural sea water (HGF = 1.83). This is also the case for the more hygroscopic mode of accumulation mode particles. In addition, the HGF of 85 nm particles observed in the atmosphere during clean marine sectors exhibits half of its population with a 1.4 HGF. An external mixture of the accumulation mode marine particles indicates a secondary source of this size of particles, a partial processing during transport, or an inhomogeneity of the sea water composition. A gentle 90 °C thermo-desorption results in a significant decrease of the number fraction of moderately hygroscopic (HGF = 1.4) particles in the accumulation mode to the benefit of the seasalt mode, pointing to the presence of semi-volatile compounds with pronounced hydrophobic properties. The thermo-desorption has no effect on the HGF of bubble generated aerosols, neither for synthetic or natural sea water, nor on the atmospheric Aitken mode, indicating that these hydrophobic compounds are secondarily integrated in the particulate phase. No difference between night and day samples is observed on the natural marine aerosols regarding hygroscopicity, but a more pronounced sensitivity to volatilization of the 1.4 HGF mode in the accumulation mode is observed during the day.

Flood or Drought: How Do Aerosols Affect Precipitation? Flood or Drought: How Do Aerosols Affect Precipitation?

Date added: 09/12/2008
Date modified: 07/01/2009
Filesize: 1.93 MB

Flood or Drought: How Do Aerosols Affect Precipitation? Daniel Rosenfeld, Ulrike Lohmann, Graciela B. Raga, Colin D. O'Dowd, Markku Kulmala, Sandro Fuzzi, Anni Reissell, and Meinrat O. Andreae (5 September 2008) Science 321 (5894), 1309. [DOI: 10.1126/science.1160606]


Abstract


Aerosols serve as cloud condensation nuclei (CCN) and thus have a substantial effect on cloud properties and the initiation of precipitation. Large concentrations of human-made aerosols have been reported to both decrease and increase rainfall as a result of their radiative and CCN activities. At one extreme, pristine tropical clouds with low CCN concentrations rain out too quickly to mature into long-lived clouds. On the other hand, heavily polluted clouds evaporate much of their water before precipitation can occur, if they can form at all given the reduced surface heating resulting from the aerosol haze layer. We propose a conceptual model that explains this apparent dichotomy.

Applicability of condensation particle counters to measure atmospheric clusters Applicability of condensation particle counters to measure atmospheric clusters

Date added: 09/12/2008
Date modified: 07/10/2009
Filesize: 617.3 kB

Sipilä, M., Lehtipalo, K., Kulmala, M., Petäjä, T., Junninen, H., Aalto, P. P., Manninen, H. E., Kyrö, E.-M., Asmi, E., Riipinen, I., Curtius, J., Kürten, A., Borrmann, S., and O'Dowd, C. D.: Applicability of condensation particle counters to measure atmospheric clusters, Atmos. Chem. Phys., 8, 4049-4060, 2008


Abstract


This study presents an evaluation of a pulse height condensation particle counter (PH-CPC) and an expansion
condensation particle counter (E-CPC) in terms of measuring ambient and laboratory-generated molecular and ion clusters. Ambient molecular cluster concentrations were measured with both instruments as they were deployed in conjunction with an ion spectrometer and other aerosol instruments in Hyyti¨al¨a, Finland at the SMEAR II station between 1 March and 30 June 2007. The observed cluster concentrations varied and ranged from some thousands to 100 000 cm−3. Both instruments showed similar (within a factor of 5) concentrations. An average size of the detected clusters was approximately 1.8 nm. As the atmospheric measurement of sub 2-nm particles and molecular clusters is a challenging task, we conclude that most likely we were unable to detect the smallest clusters. Nevertheless, the reported concentrations are the best estimates to date for minimum cluster concentrations in a boreal forest environment.

MEASUREMENTS OF NON METHANE HYDROCARBONS, DIMETHYL. SULPHIDE AND LIGHTWEIGHT OXYGENATED VOLATILE ORG MEASUREMENTS OF NON METHANE HYDROCARBONS, DIMETHYL. SULPHIDE AND LIGHTWEIGHT OXYGENATED VOLATILE ORG

Date added: 09/04/2008
Date modified: 07/09/2009
Filesize: 5.33 kB

J. Hopkins, K. Read , A. Lewis , J. Stanton and M. Pilling, MEASUREMENTS OF NON METHANE HYDROCARBONS, DIMETHYL. SULPHIDE AND LIGHTWEIGHT OXYGENATED VOLATILE ORGANIC COM-. POUNDS DURING NAMBLEX


Abstract


Marine boundary layer concentrations of C2-C7 non methane hydrocarbons (NMHCs) and lightweight oxygenated volatile organic compounds (o-VOCs) were measured during the NAMBLEX campaign, Mace Head, Ireland during the summer of 2002. A multi-bed, Peltier-cooled adsorbent trap was used to acquire samples every hour and were analysed using an in-situ dual column gas chromatograph coupled with two flame ionisation detectors (GC-FID). The equipment ran almost continuously for the seven weeks of the campaign, between 24th July and 3rd September, and collected data in a variety of meteorological conditions with diverse airmass origins. Average concentrations of acetylene, methanol, acetone and acetaldehyde at the site ranged from 40, 1051, 603 and 256 pptV respectively under clean south-westerly conditions and 154, 1693, 1133 and 530 pptV respectively in polluted easterly air masses. OVOCs were found to dominate the mass of organic species observed at the site under all atmospheric conditions and were also found to be the major organic loss route for hydroxyl radicals. Secondary production through hydrocarbon oxidation was found to be a major source of the measured o-VOCs. The variance of short lived oxygenates such as acetaldehyde was significantly less than for a hydrocarbon species with equivalent OH reactivity. Modelling studies indicate that this may be caused by significant oxygenate production occurring 2-10 days downwind from point of original surface emission. The extended time period over which acetaldehyde is produced appears to result from degradation of longer lived organic reservoir species such as a alcohols and peroxides formed during hydrocarbon oxidation. Evidence of a direct terrestrial emission source for acetaldehyde and acetone was observed during polluted easterly periods. No oceanic source was observed for these compounds.

The North Atlantic Marine Boundary Layer Experiment (NAMBLEX). Discussion The North Atlantic Marine Boundary Layer Experiment (NAMBLEX). Discussion

Date added: 08/30/2008
Date modified: 07/23/2009
Filesize: 8.12 MB

Heard, D. E., K. A. Read, J. Methven, S. Al-Haider, W. J. Bloss, G. P. Johnson, M. J. Pilling, P. W. Seakins, S. C. Smith, R. Sommariva, J. C. Stanton, T. J. Still, B. Brooks, G. De Leeuw, A. V. Jackson, J. B. McQuaid, R. Morgan, M. H. Smith, L. J. Carpenter, N. Carslaw, J. R. Hamilton, J. Hopkins, J. D. Lee, A. C. Lewis, R. M. Purvis, D. J. Wevill, N. Brough, T. Green, G. Mills, S. A. Penkett, J. M. C. Plane, A. Saiz-Lopez, D. Worton, P. S. Monks, Z. Fleming, A. R. Rickard, M. Alfarra, J. D. Allan, K. Bower, H. Coe, M. Cubison, M. Flynn, G. McFiggans, M. Gallagher, E. G. Norton, C. D. O'Dowd, J. Shillito, D. Topping, G. Vaughan, P. Williams, M. Bitter, S. M. Ball, R. L. Jones, I. M. Povey, S. O'Doherty, P. G. Simmonds, A. Allen, R. P. Kinnersley, D. C. S. Beddows, M. Dall'Osto, R. M. Harrison, R. J. Donovan, M. R. Heal, S. G. Jennings, C. Noone and G. Spain, The North Atlantic Marine Boundary Layer Experiment (NAMBLEX). Overview of the campaign held at Mace Head, Ireland, in summer 2002, Atmospheric Chemistry and Physics Discussions, Vol. 5, pp 12177-12254, 2005.


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.

 

Characteristic features of air ions at Mace Head on the west coast of Ireland Characteristic features of air ions at Mace Head on the west coast of Ireland

Date added: 08/07/2008
Date modified: 07/27/2009
Filesize: 917.86 kB

Marko Vana, Mikael Ehn, Tuukka Petaja, Henri Vuollekoski, Pasi Aalto, Gerrit de Leeuw, Darius Ceburnis, Colin D. O'Dowd, Markku Kulmala, Characteristic features of air ions at Mace Head on the west coast of Ireland, Atmospheric Research


Abstract


Coastal nucleation events and behavior of cluster ions were characterized through the measurements of air ion mobility distributions at the Mace Head research station on the west coast of Ireland in 2006. We measured concentrations of cluster ions and charged aerosol particles in the size range of 0.34–40 nm. These measurements allow us to characterize freshly nucleated charged particles with diameters smaller than 3 nm. The analysis shows that bursts of intermediate ions (1.6–7 nm) are a frequent phenomenon in the marine coastal environment. Intermediate ion concentrations were generally close to zero, but during some nucleation episodes the concentrations increased to several hundreds per cm3. Nucleation events occurred during most of the measurement days. We classified all days into one of seven classes according to the occurrence and type of new particle formation. Nucleation events were observed during 207 days in 2006, most prominently in the spring and summer months. Rain-induced events, in turn, were observed during 132 days. Particle formation and growth events mostly coincided with the presence of low tide. Also small cluster ions (0.34–1.6 nm) were characterized. Average concentrations of small ions were 440 cm− 3 for the negative ions and 423 cm− 3 for the positive ions. Average mean mobilities of small ions were 1.86 cm2V− 1s− 1 and 1.49 cm2V− 1s− 1 for the negative and positive polarities, respectively. Concentrations of small ions were observed to be strongly dependent on the variations of meteorological parameters including wind speed and direction.

 

Globally significant oceanic source of organic carbon aerosol Globally significant oceanic source of organic carbon aerosol

Date added: 08/06/2008
Date modified: 07/24/2009
Filesize: 1.07 MB

Spracklen, D. V., S. R. Arnold, J. Sciare, K. S. Carslaw, and C. Pio (2008), Globally significant oceanic source of organic carbon aerosol, Geophys. Res. Lett., 35, L12811, doi:10.1029/2008GL033359.


Abstract


Significant concentrations of organic carbon (OC) aerosol are observed at three oceanic surface sites (Amsterdam Island, Azores and Mace Head). Two global chemical transport models (CTMs) underpredict OC concentrations at these sites (normalised mean bias of −67% and −58%). During periods of high biological activity monthly mean concentrations are underpredicted by a factor of 5–20. At Amsterdam Island and Mace Head, observed OC correlates well (R2 = 0.61–0.77) with back-trajectory weighted chlorophyll-a, suggesting an oceanic OC source driven by biological activity. We use a combination of remote sensed chlorophyll-a, back trajectories and observed OC to derive an empirical relation between chlorophyll-a and the total oceanic OC emission flux. Using the GEOS-chem CTM we show a global oceanic OC emission, from primary and secondary sources, of ∼8 Tg/year matches observations. This emission is comparable in magnitude to the fossil fuel OC source and increases the simulated global OC burden by 20%.

 

Regional climate simulations of North Atlantic cyclones: changes .. in a climate change scenario Regional climate simulations of North Atlantic cyclones: changes .. in a climate change scenario

Date added: 08/06/2008
Date modified: 07/23/2009
Filesize: 4.19 MB

Semmler, S. Varghese, R. McGrath, P. Nolan, S. Wang, P. Lynch, C. O'Dowd, Regional climate simulations of North Atlantic cyclones: changes in frequency and intensity in a climate change scenario, Climate Res. Vol. 36: 1–16, 2008, doi: 10.3354/cr00732,  2008


Abstract

 

Frequency and intensity of cyclones over the North Atlantic are investigated using 2 data sets from simulations with the Rossby Centre regional climate model RCA3. The model domain comprises large parts of the North Atlantic and the adjacent continents. RCA3 is driven by ECHAM5- OM1 general circulation model data for May to December from 1985 to 2000 and May to December from 2085 to 2100 assuming the SRES-A2 emission scenario. We apply an objective algorithm to identify and track tropical and extratropical cyclones, as well as extratropical transition. The simulation
indicates increase in the count of strong hurricanes and extratropical cyclones. Contrasting, and generally weaker, changes are seen for the less extreme events. Decreases of 18% in the count of extratropical cyclones and 13% in the count of tropical cyclones with wind speeds of ≥18 m s–1 can be found. Furthermore, there is a pronounced shift in the tracks of hurricanes and their extratropical transition in November and December—more hurricanes are seen over the Gulf of Mexico, the Caribbean Sea and the western Sargasso Sea and less over the southern North Atlantic.

Ten years of CO2, CH4,CO and N2O fluxes over Western Europe inferred from atmospheric..,Ireland Ten years of CO2, CH4,CO and N2O fluxes over Western Europe inferred from atmospheric..,Ireland

Date added: 08/01/2008
Date modified: 07/23/2009
Filesize: 2.45 MB

Messager, C., Schmidt, M., Ramonet, M., Bousquet, P., Simmonds, P., Manning, A., Kazan, V., Spain, G., Jennings, S. G., and Ciais, P.: Ten years of CO2, CH4, CO and N2O fluxes over Western Europe inferred from atmospheric measurements at Mace Head, Ireland, Atmos. Chem. Phys. Discuss., 8, 1191-1237, 2008


Abstract


We estimated CO2, CH4, CO and N2O emission fluxes over the British Isles and Western Europe using atmospheric radon observations and concentrations recorded at the Mace Head Atmospheric Research Station between 1996 and 2005. We classified hourly concentration data into either long-range European or regional sources from Ireland and UK, by using local wind speed data in conjunction with 222Rn and 212Pb threshold criteria. This leads to the selection of about 7% of the total data for both sectors. We then used continuous 222Rn measurements and assumptions on the surface emissions of 222Rn to deduce the unknown fluxes of CO2, CH4, CO and N2O. Our results have been compared to the UNFCCC, EMEP and EDGAR statistical inventories and to inversion results for CH4. For Western Europe, we found yearly mean fluxes of 4.1±1.5 106 kg CO2 km−2 yr−1 , 11.9±2.0 103 kg CH4 km−2 yr−1, 12.8±4.2 103 kg CO km−2 yr−1 and 520.2±129.2 kg N2O km−2 yr−1, respectively, for CO2, CH4, CO and N2O over the period 1996–2005. The method based upon 222Rn to infer emissions has many sources of systematic errors, in particular its poorly known and variable footprint, uncertainties in 222Rn soil fluxes and in atmospheric mixing of air masses with background air. However, these biases are likely to remain constant in the long-term, which makes the method quite efficient to detect trends in fluxes. Over the last ten years period, the decrease of the anthropogenic CH4, CO and N2O emissions in Europe estimated by inventories (respectively −30%, −35% and −23%) is confirmed by the Mace Head data within 2%. Therefore, the 222Rn method provides an independent way of verification of changes in national emissions derived from inventories. Using European-wide estimates of the CO/CO2 emission ratio, we also found that it is possible to separate the fossil fuel CO2 emissions contribution from the one of total CO2 fluxes. The fossil fuel CO2 emissions and their trends derived in that manner agree very well with inventories.

Study of water-soluble atmospheric humic matter in urban and marine envirorments Study of water-soluble atmospheric humic matter in urban and marine envirorments

Date added: 08/01/2008
Date modified: 07/07/2009
Filesize: 406.61 kB
Krivácsy, Z., Kiss, G., Ceburnis, D., Jennings, G., Maenhaut, W., Salma, I., Shooter, D.,
Study of water-soluble atmospheric humic matter in urban and marine environments,
Atmospheric Research 87 (2008) 1–12.

Abstract


Recently, atmospheric humic matter or humic-like substances (HULIS) have been found in the water-soluble fraction of atmospheric aerosol sampled at different locations. Most of these locations were continental, non-urban sites. Therefore, in this work HULIS was studied in urban and marine environments. The atmospheric concentration varied over a wide range from 0.40 to 5.44 μg m-3, from the clean marine air (Mace Head, Ireland) to the heavily polluted winter urban atmosphere (Christchurch, New Zealand). In terms of carbon, ratio of HULIS was 19-51% of water-soluble organic carbon, and 10-22% of total carbon. Different spectroscopic techniques were applied for the physico-chemical characterisation of HULIS including relative aromaticity and molecular weight. Specific absorbance was observed to be much less variable than specific fluorescence, and consequently UV-VIS spectroscopy at λ>330 nm was recommended for rapid, semi-quantitative determination of HULIS in the water extracts of atmospheric aerosol. Application of a dual filter sampling system at one of the sampling sites has revealed a significant positive sampling artefact which calls for further systematic studies on this subject, and also supports the idea of a secondary organic aerosol formation mechanism of HULIS.

Regional model simulation of North Atlantic cyclones Present climate and idealized response to incre Regional model simulation of North Atlantic cyclones Present climate and idealized response to incre

Date added: 08/01/2008
Date modified: 07/23/2009
Filesize: 2.79 MB
Semmler, T., S. Varghese, R. McGrath, P. Nolan, S. Wang, P. Lynch, and C. O'Dowd, Regional model simulation of North Atlantic cyclones: Present climate and idealized response to increased sea surface temperature, J. Geophys. Res., 113, D02107, doi:10.1029/2006JD008213, 2008.

Abstract

 

The influence of an increased sea surface temperature (SST) on the frequency and intensity of cyclones over the North Atlantic is investigated using two data sets from simulations with the Rossby Centre regional climate model RCA3. The model domain comprises large parts of the North Atlantic and the adjacent continents. RCA3 is driven by reanalysis data for May to December 1985–2000 at the lateral and lower boundaries, using SST and lateral boundary temperatures. A realistic interannual variation in tropical storm and hurricane counts is simulated. In an idealized sensitivity experiment, SSTs and boundary condition temperatures at all levels are increased by 1 K to ensure that we can distinguish the SST from other factors influencing the development of cyclones. An increase in the count of strong hurricanes is simulated. There is not much change in the location of hurricanes. Generally weaker changes are seen in the extratropical region
and for the less extreme events. Increases of 9% in the count of extratropical cyclones and 39% in the count of tropical cyclones with wind speeds of at least 18 m/s are found.

Regional climate model simulations of North Atlantic cyclones frequency and intensity changes Regional climate model simulations of North Atlantic cyclones frequency and intensity changes

Date added: 08/01/2008
Date modified: 07/23/2009
Filesize: 4.19 MB
Semmler, T., S. Varghese, R. McGrath, P. Nolan, S. Wang, P. Lynch, and C. O'Dowd (2008) 'Regional climate model simulations of North Atlantic cyclones: frequency and intensity changes'. Climate Research, 36 :1-16.

Abstract


Frequency and intensity of cyclones over the North Atlantic are investigated using 2 data sets from simulations with the Rossby Centre regional climate model RCA3. The model domain comprises large parts of the North Atlantic and the adjacent continents. RCA3 is driven by ECHAM5- OM1 general circulation model data for May to December from 1985 to 2000 and May to December from 2085 to 2100 assuming the SRES-A2 emission scenario. We apply an objective algorithm to identify and track tropical and extratropical cyclones, as well as extratropical transition. The simulation indicates increase in the count of strong hurricanes and extratropical cyclones. Contrasting, and generally weaker, changes are seen for the less extreme events. Decreases of 18% in the count of extratropical cyclones and 13% in the count of tropical cyclones with wind speeds of ≥18 m s–1 can be found. Furthermore, there is a pronounced shift in the tracks of hurricanes and their extratropical transition in November and December—more hurricanes are seen over the Gulf of Mexico, the Caribbean Sea and the western Sargasso Sea and less over the southern North Atlantic.

Marine aerosol chemistry gradients Elucidating primary and secondary processes and fluxes Marine aerosol chemistry gradients Elucidating primary and secondary processes and fluxes

Date added: 08/01/2008
Date modified: 07/24/2009
Filesize: 260.53 kB

Ceburnis, D., C. D. O'Dowd, G. S. Jennings, M. C. Facchini, L. Emblico, S. Decesari, S. Fuzzi, and J. Sakalys (2008), Marine aerosol chemistry gradients: Elucidating primary and secondary processes and fluxes, Geophys. Res. Lett., 35, L07804, doi:10.1029/2008GL033462.


Abstract


Production mechanisms of aerosol chemical species, in terms of primary and secondary processes, were studied using vertical concentration gradient measurements at the coastal research station in Mace Head, Ireland. Total gravimetric PM1.0 mass, sea salt and water insoluble organic carbon (WIOC) concentration profiles showed a net production at the surface (i.e. primary production), while nssSO4 and water soluble organic carbon (WSOC) concentration profiles showed a net removal at the surface. These observations indicate that WSOC was predominantly of secondary origin and that WIOC was predominantly of primary origin. Derived PM1 mass fluxes compared reasonably well with those previously obtained from an eddy covariance (EC) technique following a power law relationship with the wind speed (F PM1 = 0.000096*U 4.23). For cases with clear primary organic mass fluxes in the flux footprint WIOM mass fluxes ranged between 0.16 and 1.02 ng m−2 s−1 and WIOM/sea salt mass ratio was 0.34–3.6, in good agreement with previous measurements at Mace Head.

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