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Data from various stations having different measurement record periods between 1988 and 2007 are analyzed to investigate the surface ozone concentration, long-term trends, and seasonal changes in and around Ireland. Time series statistical analysis is performed on the monthly mean data using seasonal and trend decomposition procedures and the Box-Jenkins approach (autoregressive integrated moving average). In general, ozone concentrations in the Irish region are found to have a negative trend at all sites except at the coastal sites of Mace Head and Valentia. Data from the most polluted Dublin city site have shown a very strong negative trend of -0.33 ppb/yr with a 95% confidence limit of 0.17 ppb/yr (i.e., -0.33 +/- 0.17) for the period 2002-2007, and for the site near the city of Cork, the trend is found to be -0.20 +/- 0.11 ppb/yr over the same period. The negative trend for other sites is more pronounced when the data span is considered from around the year 2000 to 2007. Rural sites of Wexford and Monaghan have also shown a very strong negative trend of -0.99 +/- 0.13 and -0.58 +/- 0.12, respectively, for the period 2000-2007. Mace Head, a site that is representative of ozone changes in the air advected from the Atlantic to Europe in the marine planetary boundary layer, has shown a positive trend of about +0.16 +/- 0.04 ppb per annum over the entire period 1988-2007, but this positive trend has reduced during recent years (e. g., in the period 2001-2007). Cluster analysis for back trajectories are performed for the stations having a long record of data, Mace Head and Lough Navar. For Mace Head, the northern and western clean air sectors have shown a similar positive trend (+0.17 +/- 0.02 ppb/yr for the northern sector and +0.18 +/- 0.02 ppb/yr for the western sector) for the whole period, but partial analysis for the clean western sector at Mace Head shows different trends during different time periods with a decrease in the positive trend since 1988 indicating a deceleration in the ozone trend for Atlantic air masses entering Europe.

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

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) nucleationviaOIO activation by H2SO4and (3) nucleationviaOIO activation by H2SO4plus condensation of a low-volatility organic vapour. Peak OIO and H2SO4vapour concentrations were both limited to6×106molecules cm-3at noontime while the peak organic vapour concentration was limited to12×106molecules cm-3. All simulations produced significant concentrations of new particles in the Aitken mode. From a base case particle concentration of 222 cm-3at radii >15 nm, increases in concentrations to 366 cm-3were predicted from the OIO-OIO case, 722 cm-3for the OIO-H2SO4case, and 1584 cm-3for the OIO-H2SO4case 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.

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 cm−3. The highest marine air concentrations occurred in polar air masses in which a 15 nm nucleation mode, with concentration of 1100 cm−3, 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 values 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.

The detailed mechanism of secondary new particle formation in the atmosphere is still under debate. It is proposed that particle formation happens via 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 (Hyytiälä, 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.

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 observations 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.

The chemical composition of marine aerosols as a function of their size is an important parameter for the evaluation of their impact on the global climate system. In this work we model 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 yr-1, compared to 24 Tg fine yr-1 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., JRC.DDG.H.2-Climate change

[1] 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 in 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 abundance. New particle formation bursts were frequently observed during daytime hours with the concentrations up to 4.5 × 105 particles cm−3 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 new-particle formation from higher order condensable iodine oxides.

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 of Mace Head, Ireland, show a chemical composition trend that is influenced by the oceanic biological activity cycle, in agreement with other observations. Laboratory experiments show that sea-spray 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.

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 22 m 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 onO3fluxes was found to be wind speed. Measured fluxes were of the same magnitude as reported in previous open ocean studies ranging from approximately+0.2to−0.5 μgm−2 s−1(−0.017 μgm−2 s−1on average, corresponding to a deposition velocity of 0.25 mms−1or a surface resistance of 4.13 smm−1). 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.

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 in-situ ozone deposition measurements and using a preliminary representation of organic chemistry. Results show insensitivity of ambient ozone concentrations modelled by the chemical-enhanced 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 2.5–500 M molec , leading to a mixing-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.

The Mulcahy (Mulcahy et al., 2008) power-law parameterization, derived at the coastal Atlantic station Mace 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 550 nm and 860 nm 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 2–18 m s−1. 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 and Mulcahy at higher wind speeds (>15 m s−1), where MODIS-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.

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 respective 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.

Size segregated atmospheric aerosol composition, over the radius range 0.05μm ≤ r ≤ 1.5μm, is inferred using an optical particle counter equipped with a high temperature heater tube cycling through temperatures from 20°C to 870°C. The volatility system infers the presence of common atmospheric constituents such as H2SO4, (NH4)2SO4, NaCl, and soot carbon. This system has been successfully used to determine the physico-chemical characteristics of accumulation mode aerosol associated with air masses of different origin. Results from ship-borne and ground based measurements are presented. For continental and modified maritime air, (NH4)2SO4 was observed to be the dominant species, whilst H2SO4 was more abundant in Arctic aerosol. Sea-salt aerosol accounts for ≈75% of accumulation mode particle concentration for maritime aerosol in periods of high wind speeds. We also show that soot carbon can be identified in polluted air using this technique.

The aerosol optical depth (AOD) and Angstrom 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 Angstrom 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 Angstrom 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 (tau(500) = 0.19 +/- 0.12) is comparable with the clean marine AOD. The continental Angstrom 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.

High time resolution aerosol mass spectrometry measurements were conducted during a field campaign at Mace Head Research Station, Ireland, in June 2007. Observations on one particular day of the campaign clearly indicated advection of aerosol from volcanoes and desert plains in Iceland which could be traced with NOAA Hysplit air mass back trajectories and satellite images. In conjunction with this event, elevated levels of sulphate and light absorbing particles were encountered at Mace Head. While sulphate concentration was continuously increasing, nitrate levels remained low indicating no significant contribution from anthropogenic pollutants. Sulphate concentration increased about 3.8 μg m −3 in comparison with the background conditions. Corresponding sulphur flux from volcanic emissions was estimated to about 0.3 TgS yr −1 , suggesting that a large amount of sulphur released from Icelandic volcanoes may be distributed over distances larger than 1000 km. Overall, our results corroborate that transport of volcanogenic sulphate and dust particles can significantly change the chemical composition, size distribution, and optical properties of aerosol over the North Atlantic Ocean and should be considered accordingly by regional climate models.

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 x [OIO](2)), activation of clusters by OIO (A x [OIO]) and sulphuric acid-induced activation of clusters containing OIO (B x [OIO] x [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 10(9) cm(-3). 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.

Marine aerosols have a key role in the climate system. They influence the radiative forcings by direct and indirect effects. In this study the influence of marine aerosols over the North‐East Atlantic is determined for January and June 2003 using an advanced regional climate model which has been incorporated with atmospheric chemistry, detailed aerosol dynamics and a cloud droplet activation model. Results reveal dramatic influence of marine aerosols in the formation of cloud droplet number concentration.

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, O-3, CH4, N2O and particles in the size range 1 nm-10 mu m including organic and inorganic chemical species. The main focus of the review is 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 O-3 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. (C) 2009 Published by Elsevier Ltd.

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. (C) 2009 Elsevier Ltd. All rights reserved.

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 accumulation 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-SO4-2, 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 comparison 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.

This paper describes results of a reasonably extensive series of ambient aerosol measurements conducted for the first time from Mace Head, on the west coast of Ireland. Aerosol size distributions (0.045 < radius, r < 1.5 micrometres (μm)) and basic meteorological parameters were measured under both maritime, modified maritime and continental air mass conditions. It was found that the shape of the size distribution spectra is dependent on air mass source.

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 (K. Values of Ware presented for wind speeds Lip 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). Citation: Callaghan, A., G. de Leeuw, L. Cohen, and C. D. O'Dowd (2008), Relationship of oceanic whitecap coverage to wind speed and wind history, Geophys. Res. Lett., 35, L23609, doi: 10.1029/2008GL036165.

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 mu m. 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.

[1] 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 Angstrom 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.

[1] 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 (FPM1 = 0.000096*U4.23). 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.

[1] 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.

[1] This study presents a novel approach to develop a combined organic-inorganic sub-micron sea-spray source function for inclusion in large-scale models. It requires wind speed and surface ocean chlorophyll-a concentration as input parameters. The combined organic-inorganic source function is implemented in the REMOTE regional climate model and sea-spray fields are predicted with particular focus on the North East Atlantic. The model predictions using the new source functions compare well with observations of total sea-spray mass and organic carbon fraction in sea-spray aerosol. During winter (periods of low oceanic biological activity), sea-salt dominates the sea-spray mass while in summer (when biological activity is high), water soluble organic carbon contributes between 60–90% of the submicron sea-spray mass.

This paper summarizes an evaluation of model simulations with a regional scale atmospheric climate-chemistry/ aerosol model called REMOTE, which has been extended by a microphysical aerosol module. Model results over Europe are presented and compared with available measurements in surface air focusing on the European distribution and variability of primary and secondary aerosols. Additionally, model results obtained with detailed aerosol microphysics are compared to those based on an aerosol bulk mass approach revealing the impact of dry deposition fluxes on atmospheric burden concentration. An improved determination of elevated ozone and sulfate concentrations could be achieved by considering a diurnal cycle in the anthropogenic emission fluxes. Deviation between modelled and measured organic carbon concentrations can be mainly explained by missing formation of secondary organic aerosols and deficiencies in emission data. Changing residential heating practices in Europe, where the use of wood is no longer restricted to rural areas, need to be considered in emission inventories as well as vegetation fire emissions which present a dominant source of organic carbon., JRC.DDG.H.2-Climate change

An Optical Particle Counter (OPC) has been designed with a single ellipsoid reflector as the main optical element. Photodiodes with low noise transimpedance are used to detect forward and backscatter responses of particles scattering laser light (685 nm) at the ellipsoid focus. The Zemax® ray tracing program has been used to estimate the OPC's light collection efficiency. The design process has included modeling the optical response of various lenses, reflector coatings, and laser wavelengths. Simulations show that our OPC with a single ellipsoid reflector has 58.2% total efficiency for collecting forward and backscattered light.

The current knowledge in primary and secondary marine aerosol formation is reviewed. For primary marine aerosol source functions, recent source functions have demonstrated a significant flux of submicrometre particles down to radii of 20 nm. Moreover, the source functions derived from different techniques up to 10 μm have come within a factor of two of each other. For secondary marine aerosol formation, recent advances have identified iodine oxides and isoprene oxidation products, in addition to sulphuric acid, as contributing to formation and growth, although the exact roles remains to be determined. While a multistep process seems to be required, isoprene oxidation products are more likely to participate in growth and sulphuric acid is more likely to participate in nucleation. Iodine oxides are likely to participate in both nucleation and growth.

International audience; A light aircraft was equipped with a bank of Condensation Particle Counters (CPCs) (50% cut from 3?5.4?9.6 nm) and a nano-Scanning Mobility Particle Sizer (nSMPS) and deployed along the west coast of Ireland, in the vicinity of Mace Head. The objective of the exercise was to provide high resolution micro-physical measurements of the coastal nucleation mode in order to map the spatial extent of new particle production regions and to evaluate the evolution, and associated growth rates of the coastal nucleation-mode aerosol plume. Results indicate that coastal new particle production is occurring over most areas along the land-sea interface with peak concentrations at the coastal plume-head in excess of 106 cm?3. Pseudo-Lagrangian studies of the coastal plume evolution illustrated significant growth of new particles to sizes in excess of 8 nm approximately 10 km downwind of the source region. Close to the plume head (?1, decreasing gradually to 53?72 nm h?1 at 3 km. Further along the plume, at distances up to 10 km, the growth rates are calculated to be 17?32 nm h?1. Growth rates of this magnitude suggest that after a couple of hours, coastal nucleation mode particles can reach significant sizes where they can contribution to the regional aerosol loading.

C.D. O’Dowd and P.E. Wagner (eds.), Nucleation and Atmospheric Aerosols, 1064–1069. © Springer 2007 Abstract An alternative method for the estimation of chemical aerosol fluxes, based on a vertical concentration gradient measurement, has been developed and executed at the coastal research station in Mace Head, Ireland. Total gravimetric PM1.0 mass, sea salt and water insoluble organic carbon (WINSOC) concentration profiles showed a net production, while nssSO 4 and water soluble organic carbon (WSOC) concentration profiles showed a net removal at the surface. It was concluded that WSOC was predominantly of secondary origin, while WINSOC was predominantly of primary origin. Potential influence of the surf zone emissions was limited to 5–20% and the measured fluxes were characteristic of the coastal zone of up to 5 km. Sea salt concentration and mass flux relationships with the wind speed were established and fitted with power function (C = a*U b). A comparison with the mass flux, derived from eddy correlation measurements yielded good agreement.

Seasonal physicochemical characteristics of North Atlantic marine aerosols are presented for the period from January 2002 to June 2004. The aerosol size distribution modal diameters show seasonal variations, 0.031 mu m in winter and 0.049 mu m in summer for the Aitken mode and 0.103 mm in winter and 0.177 mu m in summer for the accumulation mode. The accumulation mode mass also showed a seasonal variation, minimum in winter and maximum in summer. A supermicron sized particle mode was found at 2 mm for all seasons showing 30% higher mass concentration during winter than summer resulting from higher wind speed conditions. Chemical analysis showed that the concentration of sea salt has a seasonal pattern, minimum in summer and maximum in winter because of a dependency of sea-salt load on wind speeds. By contrast, the non-sea-salt (nss) sulphate concentration in fine mode particles exhibited lower values during winter and higher values during midsummer. The water soluble organic carbon (WSOC) and total carbon (TC) analysis also showed a distinctive seasonal pattern. The WSOC concentration during the high biological activity period peaked at 0.2 mu gC m(-3), while it was lower than 0.05 mu gC m(-3) during the low biological activity period. The aerosol light scattering coefficient showed a minimum value of 5.5 Mm(-1) in August and a maximum of 21 Mm(-1) in February. This seasonal variation was due to the higher contribution of sea salt in the MBL during North Atlantic winter. By contrast, aerosols during late spring and summer exhibited larger angstrom parameters than winter, indicating a large contribution of the biogenically driven fine or accumulation modes. Seasonal characteristics of North Atlantic marine aerosols suggest an important link between marine aerosols and biological activity through primary production of marine aerosols.

Primary marine aerosol fluxes were measured using eddy covariance (EC), a condensation particle counter (CPC) and an optical particle counter (OPC) with a heated inlet. The later was used to discriminate between sea salt and total aerosol. Measurements were made from the 25 m tower at the research station Mace Head at the Irish west coast, May to September 2002. The aerosol fluxes were dominated by upward fluxes, sea spray from bubble bursting at the ocean surface. The sea salt aerosol number emissions increased two orders of magnitude with declining diameter from 1 to 0.1 μm where it peaked at values of 105 to 107 particles m−2s−1. The sea salt emissions increased at all sizes in the wind range 4 to 22 ms−1, in consistency with a power function of the wind speed. The sea salt emission data were compared to three recent sub micrometer sea salt source parameterisations. The best agreement was with Mårtensson et al. (2003), which appear to apply from 0.1 to 1.1 μm diameters in temperate water (12°C) as well as tropical water (25°C). The total aerosol emissions were independent of the wind speed below 10 ms−1, but increased with the wind above 10 ms−1. The aerosol volume emissions were larger for the total aerosol than for the sea salt at all wind speeds, while the sea salt number emissions approached the total number emissions at 15 ms−1. It is speculated that this is caused by organic carbon in the surface water that is depleted at high wind speeds. The data are consistent with an internal aerosol mixture of sea salt, organic carbon and water. Using the aerosol model by Ellison et al. (1999) (a mono-layer of organic carbon surrounding a water-sea-salt brine) we show that the total and sea salt aerosol emissions are consistent. This predict that the organic carbon fraction increase with decreasing diameter from a few % at 1 μm over 50% at about 0.5 μm to about 90% at 0.1 μm, in consistency with simultaneous chemical data by Cavalli et al. (2004). The combined models of Mårtensson et al. (2003) and Ellison et al. (1999) reproduce the observed total aerosol emissions and offer an approach to model the organic sea spray fraction.

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 0.4–40 nm. These measurements allow us to characterize freshly nucleated charged particles with diameter below 3 nm. The analysis shows that bursts of intermediate ions (1.6–7 nm) are a frequent phenomenon in marine coastal environment. Nucleation evens occurred during most of the measurement days. We classified the nucleation burst events. Particle formation and growth events mostly coincided with the presence of low tide. Small ions concentrations appear to be strongly dependent on the variations of meteorological parameters including wind speed and direction.

During the summer of 2006 a measurement campaign was conducted on a ship in the North Atlantic. We measured the concentration, size distribution and hygroscopicity of the atmospheric aerosol particles. The size distribution consisted of two separate modes, one peaking at 50 nm and the other at 200 nm. Based on the hygroscopicity measurements, the first mode was internally mixed and had a hygro- scopic growth factor of 1.6-1.7. In the afternoon of 13 June we observed a mode of small particles, which grew during the evening to 30-40 nm. These particles are believed to be secondary particles, which would make this a very rare observation. Further analysis will be made once more supporting data becomes available.

Organic marine aerosol (of both primary and secondary origin) represents a potentially important component of the marine biota and climate feedback system involving aerosols and clouds (O’Dowd et al., 2004; Cavalli et al., 2004). In order to assess the potential influence of costal environment on marine aerosol chemical composition, both organic and inorganic, two parallel aerosol data sets, collected in two campaigns in the framework of the EC project MAP, are compared in this work. The field experiments have been carried out from June 5 and July 5 2006, during the period of high oceanic biological activity at Mace Head Atmospheric Research Station (costal site) and on board of the oceanographic vessel “Celtic Explorer” (open ocean site). At both the sites the sampling has been fixed approximately at 10 m height above the sea level. Aerosol samples were collected, under clean conditions (Cavalli et al., 2004) by means of 8stages Berner impactors equipped with tedlar foils, collecting particles in eight size fractions between 0.060 and 16 μm diameter. In order to obtain a detailed chemical characterization of organic fraction, aerosol samples were also collected by high volume virtual impactors, segregating fine (a. d. less than 1 μm diameter ) and coarse particles (a. d. between 1 and 10 μm diameter ) on quartz filters. Three parallel aerosol samples were collected during the campaigns as a result of sampling time of the order of 50 hours each. WSOC (Water Soluble Organic Carbon) and main inorganic ions analyses were performed on tedlar foils, while high volume samples were used for Total Carbon (TC) analyses and for organics chemical characterization (HPLC fractionation, HNMR functional group analyses and tensioactive properties analysis). Non-sea-salt (nss) sulphate is the dominant species in submicron fraction in both samples sets, showing a similar trend both in coastal and in open ocean samples. For each stage of the fine fraction coastal site samples show an average nssSO4 concentration higher than the open ocean samples. On the contrary, average WSOC concentration in the fine fraction is very similar for samples collected at Mace Head Station and at the open ocean site. The ratio between WSOC and WIOC (Water Insoluble Organic Carbon) is slightly lower in samples collected at the coastal site, being WSOC the dominant fraction of organics in both samples sets. Coarse fraction is dominated by sea salt in all the size intervals; however, in terms of absolute mass the coastal samples result enriched in sea salt as compared to open ocean samples. Concerning WSOC chemical characterization, HNMR analyses show that functional groups distribution in samples collected during the cruise is consistent with the one of samples collected at Mace Head Station, suggesting the same chemical composition and the same origin. Moreover, the investigation of tensioactive properties of fine fraction isolated WSOC highlights the same behaviour for both samples collected in middle ocean and at the coastal site. In conclusion, our results show strong similarity between aerosol physico-chemical properties at coastal station and open ocean site , especially for the main organic components thus excluding potential effects of the shore line environment on marine organic aerosol.

Aerosol dynamical simulations of coastal new particle formation have been performed in order to investigate the nucleation and growth mechanisms in this environment. In the simulations, it is assumed that the nucleating vapour is iodine dioxide. Both Eulerian and Lagrangian type simulations have been performed and compared to observations. We have found it difficult to achieve the observed, enormous growth rates, and simulations agree with the experiments only when OIO concentration is very high and growth time has been prolonged

The present work reviews the state of knowledge on organic marine aerosol, starting with an historic overview of the topic from the early 1970s to the most recent years. New results from the MAP-EU project are then reported, showing the main features of the organic fraction, and illustrating how primary and secondary components of marine aerosols can be distinguished by means of chemical analysis. The findings also have potential implications for the atmospheric chemis- try of aerosol particles and clouds.

Chemical composition of TSP matter has been studied during long-term measurement campaign at Mace Head during 2001–2004. Aerosol particles in clean marine air masses were sampled in parallel with continuous samples to reveal relative contribution of natural sources. Inorganic composition changes revealed strong seasonal patterns, with dominant contribution of sea salt (40–95%) and anthropogenic nitrate. Natural biogenic sources contributed significantly to total aerosol budget. Wind speed and sea salt mass relationship has been examined and used to predict nssSO4 concentration in marine environment. Predicted nssSO4 was overestimated by 34%, but correlation between predicted and measured values was 0.61 at P << 0.01.