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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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Charge separation due to water drop and cloud droplet interactions in an electric field Charge separation due to water drop and cloud droplet interactions in an electric field

Date added: 01/01/1975
Date modified: 07/01/2009
Filesize: 2.09 MB
Jennings, S.G. (1975)- Charge separation due to water drop and cloud droplet interactions in an electric field. Quart. J. Roy. Met. Soc., 101, 227-233.   

Measurements were made of the electric charge acquired by drops of mean radius of about 750m, in the presence of a vertical electric field E, the value of which could be varied from 4·5 to 27kV/m. It was found that the average charge acquired by the water drop as a consequence of the inductive process increased from 0·1fC to about 0·25fC as the electric field strength increased from 5kV/m to about 15kV/m, but there-after decreased with increasing values of electric field.
This work suggests that the collisions between polarized rain-drops and cloud droplets in natural clouds could give rise, very effectively, to the production of electric fields of about 30kV/m; but that significantly larger fields could not be produced since all collisions in the higher fields would result in permanent coalescence.

Nolan–Pollak type CN counters in the Vienna aerosol workshop Nolan–Pollak type CN counters in the Vienna aerosol workshop

Date added: 07/31/2002
Date modified: 07/03/2009
Filesize: 321.73 kB

Gras, J.L., J. Podzimek, T.C. O'Connor, K-H Enderle, Nolan-Pollak type CN counters in the Vienna aerosol workshop. Atmos. Res. 62, 239-254, 2002.



Three standard Nolan-Pollak (N-P) and a modified N-P design condensation nucleus (CN) counters were included in the Vienna Workshop on Intercomparison of Condensation Nuclei and Aerosol Particle counters. These counters came from diverse backgrounds, namely programs in USA, Europe and Australia. In this work, principles of the operation and previous history of calibration of the N-P expansion counter are briefly reviewed and comparisons between the particular counters used in the workshop are presented and discussed. Counting agreement was found to be very good between the N-P counters, typically better than ± 12% for a range of aerosol sizes and compositions from a minimum diameter of 4 nm. The independently calibrated GIV CNC-440 (modified N-P type counter) also agreed well with the N-P counters. The minimum size sensitivity of the N-P counter was examined showing a lower detection limit for insoluble (Ag) particles of around 2.6 ± 0.3 nm diameter.

Strong correlation between levels of tropospheric OH and UV-B Strong correlation between levels of tropospheric OH and UV-B

Date added: 04/22/2006
Date modified: 07/27/2009
Filesize: 1.22 MB

Rohrer, F. and H. Berresheim, Strong correlation between levels of tropospheric hydroxyl radicals and solar ultraviolet radiation, Nature, 442, 184-187, 2006.


The most important chemical cleaning agent of the atmosphere is the hydroxyl radical, OH. It determines the oxidizing power of the atmosphere, and thereby controls the removal of nearly all gaseous atmospheric pollutants. The atmospheric supply of OH is limited, however, and could be overcome by consumption due to increasing pollution and climate change, with detrimental feedback effects. To date, the high variability of OH concentrations has prevented the use of local observations to monitor possible trends in the concentration of this species. Here we present and analyse long-term measurements of atmospheric OH concentrations, which were taken between 1999 and 2003 at the Meteorological Observatory Hohenpeissenberg in southern Germany. We find that the concentration of OH can be described by a surprisingly linear dependence on solar ultraviolet radiation throughout the measurement period, despite the fact that OH concentrations are influenced by thousands of reactants. A detailed numerical model of atmospheric reactions and measured trace gas concentrations indicates that the observed correlation results from compensations between individual processes affecting OH, but that a full understanding of these interactions may not be possible on the basis of our current knowledge of atmospheric chemistry. As a consequence of the stable relationship between OH concentrations and ultraviolet radiation that we observe, we infer that there is no long-term trend in the level of OH in the Hohenpeissenberg data set.

A Case Study of Ship Track Formation in a Polluted Marine Boundary Layer A Case Study of Ship Track Formation in a Polluted Marine Boundary Layer

Date added: 08/06/2000
Date modified: 06/30/2009
Filesize: 509.16 kB

Noone, K. J., D. W. Johnson, et al. (2000). "A Case Study of Ship Track Formation in a Polluted Marine Boundary Layer." J. Atmos. Sci. 57(16): 2748-2764.



A case study of the effects of ship emissions on the microphysical, radiative, and chemical properties of polluted marine boundary layer clouds is presented. Two ship tracks are discussed in detail. In situ measurements of cloud drop size distributions, liquid water content, and cloud radiative properties, as well as aerosol size distributions (outside-cloud, interstitial, and cloud droplet residual particles) and aerosol chemistry, are presented. These are related to remotely sensed measurements of cloud radiative properties.

The authors examine the processes behind ship track formation in a polluted marine boundary layer as an example of the effects of anthropogenic particulate pollution on the albedo of marine stratiform clouds.


Accelerated Rates of Rainfall Accelerated Rates of Rainfall

Date added: 07/09/1971
Date modified: 06/30/2009
Filesize: 384.37 kB
P. R. BRAZIER-SMITH, S. G. JENNINGS & J. LATHAM, Accelerated Rates of Rainfall,  Nature 232, 112 - 113 (09 July 1971); doi:10.1038/232112b0



RAINFALL intensity within clouds may be greatly increased by the production of satellite drops when raindrops collide, and this process could explain the extremely high rates of rainfall development reported in certain clouds1,2. We have set out to test this possibility by laboratory experiments.

Measurement of OH and HO2 in the Troposphere Measurement of OH and HO2 in the Troposphere

Date added: 08/06/2003
Date modified: 07/23/2009
Filesize: 669.08 kB

D. E. Heard and M. J. Pilling, "Measurement of OH and HO2 in the troposphere," Chem. Rev. 103, 5163-5198 (2003).


Volatile organic compounds (VOCs), emitted into the atmosphere, react with a range of oxidants, of which the most important are OH, NO3, and ozone. Under most atmospheric conditions, and during the day, the removal of VOCs is dominated by their reaction with OH. This ability of the atmosphere to “cleanse itself”, and to continue doing so into the future, affects many processes. The concentration of methane, and hence its contribution to radiative forcing, is determined by the balance between its rate of emission and the rate of its removal by reaction with OH. The global distribution and seasonal variability of methane depend on the interaction between emission and reaction with OH. Tropospheric oxidation is also responsible for the formation of groundlevel ozone and photochemical smog and for the production of secondary organic aerosols. The spatial distribution and concentrations of oxidants, such as OH, depend on a wide range of factors, including emissions of both volatile organic compounds and nitrogen ooxides and the interaction of atmospheric transport and chemical kinetics. Oxidation is a complex chemical process, which proceeds through a series of partially oxidized intermediates; the primary emitted compounds and the intermediates have a wide range of atmospheric lifetimes, from minutes to years, depending, in most cases, on their rate constants for reaction with OH and the OH  concentration, [OH]. Thus, the concentrations of photochemically active radical precursors, such as acetone in the upper troposphere, depend on their formation by oxidation of VOCs emitted at the surface, their atmospheric lifetimes, and their rate of vertical transport. Clearly, OH plays a central role in tropospheric chemistry. The in situ measurement of its concentration has long been a goal, but its short lifetime and consequently low concentration provide a seriouschallenge. Considerable progress has been made, however, over the last 10 years, and there are now several OH instruments which are actively used for both ground- based and aircraft-based campaigns, employing principally laser-induced fluorescence, laser absorption, and chemical ionization. Some of these instruments can also be used to measure HO2, which is closely coupled to OH; [OH]:[HO2] depends sensitively on the chemical composition of the atmosphere and particularly on the concentrations of VOCs and NOx. The atmospheric lifetime of OH is 1 s or less, and it has been argued that its concentration is determined only by the local concentrations of longer-lived species such as O3, VOCs, and NOx, and is not affected directly by atmospheric transport. Thus, field measurements of [OH] can be interpreted through zero-dimensional chemical box models, in which the concentrations of longer-lived species are constrained to simultaneous, co-located measured values. This approach has led to the use of measurements of [OH], coupled with contemporaneous measurements of other species, as a way of evaluating chemical mechanisms for atmospheric oxidation. The interpretation of the box models has also provided a means of investigating the interaction of component reactions in the chemical mechanisms under a range of differing but representative chemical environments.

Marine aerosol, sea-salt, and the marine sulphur cycle a short review Marine aerosol, sea-salt, and the marine sulphur cycle a short review

Date added: 08/06/1997
Date modified: 07/02/2009
Filesize: 701.66 kB

O'Dowd, C. D., Lowe, J. A. & Smith, M. H. Marine aerosol, sea-salt, and the marine sulphur cycle: A short review. Atmos. Environ. 31, 73−80 (1997)


A short review of the marine aerosol size distribution and the contribution of sea-salt to this distribution is presented. The potential role of sea salt in the marine boundary layer sulphur cycle is highlighted.

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


 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.

Biogenically-driven organic contribution to marine aerosol Biogenically-driven organic contribution to marine aerosol

Date added: 08/01/2004
Date modified: 07/27/2009
Filesize: 296.9 kB

O'Dowd, C.D., M.C. Facchini, F. Cavalli, D. Ceburnis, M. Mircea, S. Decesari, S. Fuzzi, Y.J. Yoon, and J.P. Putaud, Biogenically-driven organic contribution to marine aerosol, Nature, doi:10.1038/nature02959,. 2004.


Marine aerosol contributes significantly to the global aerosol load and consequently has an important impact on both the Earth's albedo and climate. So far, much of the focus on marine aerosol has centred on the production of aerosol from sea-salt1 and non-sea-salt sulphates2, 3. Recent field experiments, however, have shown that known aerosol production processes for inorganic species cannot account for the entire aerosol mass that occurs in submicrometre sizes4, 5, 6. Several experimental studies have pointed to the presence of significant concentrations of organic matter in marine aerosol7, 8, 9, 10, 11. There is some information available about the composition of organic matter12, 13, 14, but the contribution of organic matter to marine aerosol, as a function of aerosol size, as well as its characterization as hydrophilic or hydrophobic, has been lacking. Here we measure the physical and chemical characteristics of submicrometre marine aerosol over the North Atlantic Ocean during plankton blooms progressing from spring through to autumn. We find that during bloom periods, the organic fraction dominates and contributes 63% to the submicrometre aerosol mass (about 45% is water-insoluble and about 18% water-soluble). In winter, when biological activity is at its lowest, the organic fraction decreases to 15%. Our model simulations indicate that organic matter can enhance the cloud droplet concentration by 15% to more than 100% and is therefore an important component of the aerosol–cloud–climate feedback system involving marine biota.

Aerosol light absorption in the North Atlantic trends and seasonal characteristic during the period 1989 to 2003 Aerosol light absorption in the North Atlantic trends and seasonal characteristic during the period 1989 to 2003

Date added: 08/01/2006
Date modified: 07/27/2009
Filesize: 547.6 kB

Junker, C., Jennings, S. G., and Cachier, H.: Aerosol light absorption in the North Atlantic: trends and seasonal characteristics during the period 1989 to 2003, Atmos. Chem. Phys., 6, 1913-1925, 2006


Aerosol light attenuation on quartz fibre filters has been measured since February 1989 at the Mace Head Atmospheric Research station near Carna, Co. Galway, Ireland, using an Aethalometer.

The frequency of occurrence of the hourly averaged aerosol absorption data is found to be bimodally distributed. The two modes result from clean marine air and anthropogenically polluted continental air both being advected to the station dependent on the prevailing wind direction. The hourly averages of the marine portion of the aerosol light absorption are found to follow closely a lognormal distribution with a geometric mean of 0.310 Mm-1. The hourly averages of continental sector aerosol absorption are neither normally nor lognormally distributed and have an arithmetic mean of 6.36 Mm-1, indicating the presence of anthropogenic sources for BC east of the Mace Head station.

The time series of the monthly averaged attenuation coefficient σatt of both marine and continental sector aerosol shows an increase from 1989 to 1997 and a levelling off thereafter.

The monthly maximum of marine sector σatt is found in May. Trend and seasonal characteristics of the clean marine aerosol attenuation coefficients observed at Mace Head appear to be driven by meteorological factors, as indicated by rainfall data and by trends in the North Atlantic Oscillation (NAO) indices. The observed increasing trends of the continental sector σatt from 1989 up to 1997 are possibly related to changes in BC emissions over Ireland, calculated from UNSTAT (2002) fuel consumption data.

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]


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.

Mesure de l'evaporation et de la radiation globale a St. Mortiz Mesure de l'evaporation et de la radiation globale a St. Mortiz

Date added: 08/07/1962
Date modified: 07/23/2009
Filesize: 1.21 MB
T.C O Connor ,Mesure de l'evaporation et de la radiation globale a St. Mortiz , Geofisica e Meteorologia Vol X  1962


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.



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.

Remote Sensing of Air Pollution Remote Sensing of Air Pollution

Date added: 08/07/1979
Date modified: 07/06/2009
Filesize: 1.35 MB

O'Connor T.C,Remote Sensing of Air Pollution , Proceedings of Seminar: Airpollution- Impacts and Controls, National Board for Science and Technology, 1979, pp. 93-96



Recent technological advances have enabled man to extend his remote sensing capabilities from looking at the visible world around him into other parts of the Electromagnetic spectrum and his vantage point from a tower or hill to an orbiting satellite. one can now stufy air pollution problems over widespread areas and at all levels in the atmosphere. The techniques used are reviewed briefly and their application to air pollution in the lower atmosphere considered.

Remote sensing instruments may be categorised by the region of the electromagnetic spectrum concerned; the purpose for which they are used the mode of action as passive or active; the signal recovery and data handling techniques; the platform used - ground, aircraft or satellite; and or fixed location instruments. Remote sensing techniques can be used to study aerosols and/or specific gases. They may be used to study pollution distribution in the horizontal and vertical directions, general air quality, plume tracking, source monitoring and other applications. Their advantages and disadvantages for air quality management are given.

Aerosol and trace gas measurements during the mace head experiment Aerosol and trace gas measurements during the mace head experiment

Date added: 07/31/1996
Date modified: 07/27/2009
Filesize: 999.68 kB

McGovern, F.M., Jennings, S.G., O'Connor, T.C., and Simmonds, P.G. (1996) - Aerosol and trace gas measurements during the Mace Head experiment. Atmos. Environ., 30, 3891 - 3902.


Measurements obtained between the 9th and 23rd of April 1991 at the Mace Head remote maritime station are presented. These measurements were obtained as part of a EUROTRAC Air Sea Exchange intensive measurement campaign. Analysis of variations in the aerosol and trace concentrations is based on inter-comparison of the measured species and use of local meteorological data and back trajectories for the period. While air masses of principally maritime origin were encountered throughout the campaign, typical background maritime conditions only occurred during short periods. Other periods were highly modified by mainly local influences which included local biomass burning and Aitken nuclei(AN) production. The biomass burning was observed to contribute to elevated accumulation mode aerosol (0.1-1.0 μm), black carbon mass concentration, CO, and CH4 levels. The O3 concentrations were variable throughout the measurement period. Reasonable correlations were found between the trace gas data except between O3 and CO during the period influenced by biomass burning when the O3 levels were generally depleted. Very high AN concentrations (> 20,000cm-3) were measured on a number of sampling days, with a distinct dawn effect being observed. The very high AN concentrations occurred during otherwise clean air conditions and also in the presence of combustion aerosols and are principally attributed to photochemical gas-to-particle conversion processes. The conditions under which these events occurred and variations in background conditions are examined.

Modeling sea-salt aerosols in the atmosphere 1. Model development Modeling sea-salt aerosols in the atmosphere 1. Model development

Date added: 08/06/1997
Date modified: 07/23/2009
Filesize: 1.25 MB

Gong, S. L., L. A. Barrie, and J.-P. Blanchet (1997), Modeling sea-salt aerosols in the atmosphere 1. Model development, J. Geophys. Res., 102(D3), 3805–3818.


A simulation of the processes of sea-salt aerosol generation, diffusive transport, transformation, and removal as a function of particle size is incorporated into a one-dimensional version of the Canadian general climate model (GCMII). This model was then run in the North Atlantic between Iceland and Ireland during the period of January-March. Model predictions are compared to observations of sea-salt aerosols selected from a review of available studies that were subjected to strict screening criteria to ensure their representativeness. The number and mass size distribution and the wind dependency of total sea-salt aerosol mass concentrations predicted by the model compare well with observations. The modeled dependence of sea-salt aerosol concentration in the surface layer (χ, μg m−3) on 10-m wind speed (U 10, m s−1) is given by χ = beaU10 . Simulations show that both a and b change with location. The value a and b range from 0.20 and 3.1 for Mace Head, Ireland to 0.26, and 1.4 for Heimaey, Iceland. The dependence of χ on surface wind speed is weaker for smaller particles and for particles at higher altitudes. The residence time of sea-salt aerosols in the first atmospheric layer (0–166 m) ranges from 30 min for large particles (r = 4–8 μm) to ∼60 hours for small particles (r = 0.13–0.25 μm). Although some refinements are required for the model, it forms the basis for comparing the simulations with long-term atmospheric sea-salt measurements made at marine baseline observatories around the world and for a more comprehensive three-dimensional modeling of atmospheric sea-salt aerosols.


Performance of a venturi dilution chamber for sampling 3-20 nm particles Performance of a venturi dilution chamber for sampling 3-20 nm particles

Date added: 08/01/2005
Date modified: 07/23/2009
Filesize: 207.08 kB

Yoon, Y.J., S. Cheevers, S.G. Jennings, C.D. O’Dowd, Performance of a venturi dilution chamber for sampling 3-20 nm particles. J. Aerosol Science, 2005, 36(4), pp 535-540. doi:10.1016/j.jaerosci.2004.10.004


The transmission efficiency of a venturi mixing and dilution system was investigated with laboratory generated aerosol by comparison of two condensation particle counters (CPCs). The transmission efficiency exceeded 95% for particle sizes between 3 and 20 nm. The use of the diluter system is demonstrated through comparison with total concentrations derived from a nano-scanning mobility particle sizer (nSMPS) applied to measuring a rapidly changing atmospheric nucleation mode. The study indicates that the diluted-CPC sampler can resolve rapidly changing, and more intense peaks in excess of 106 cm-3, which are otherwise missing or under-sampled by the nSMPS.

Regional model simulation of North Atlantic cyclones...response to increased sea surface temper Regional model simulation of North Atlantic cyclones...response to increased sea surface temper

Date added: 08/06/2007
Date modified: 07/06/2009
Filesize: 2.79 MB

Semmler, T., S. Varghese, R. McGrath, P. Nolan, S. Wang, P. Lynch, and C. O'Dowd (2008), 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.


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.


Aerosol particle size distribution in the 0.25-5.0 micron radius range in Northern England Aerosol particle size distribution in the 0.25-5.0 micron radius range in Northern England

Date added: 07/30/1977
Date modified: 06/30/2009
Filesize: 1.3 MB

Jennings, S.G., and Elleson, R.K. (1977)- Aerosol size distributions in the 0.25 to 5 micrometre radius range. Atmos. Environ., 11, 361-366.


An analysis has been made of continuous measurements on the particle size distribution of the atmospheric aerosol in five particle radius categories between 0.25 and 5.0 μm. An automatic Royco model 225 optical particle counter together with a digital line printer was used to obtain the measurements at a 10 min sampling frequency from 21 July to 8 September 1975 at Durham Observatory, 2 km SSW of Durham City in the North East of England. Measurements were also taken every 10 min from 15 December to 6 January 1976 on the summit of Great Dun Fell, 842 msl, on the Northern Pennine Range, England.

Diurnal variation associated with the particle number concentration shows maximum concentration from about 02:00–08:00 h BST and a minimum over the period 14:00–20:00 h BST.

The particle size distribution for both the Durham and Great Dun Fell site follows the shape of a Junge log-radius type distribution with slopes β equal to 3.04 and 2.74 respectively. The distributions show that the number concentration over the five radius intervals is an order of magnitude lower at the mountain site of Great Dun Fell than at Durham Observatory.

An analysis of the sampling frequency of particle concentrations showed that the measurements could be made less frequently by factors up to 20, without loss of accurate information.

Microphysical and physico-chemical characterization of atmospheric marine and continental aerosol at mace head Microphysical and physico-chemical characterization of atmospheric marine and continental aerosol at mace head

Date added: 07/31/1997
Date modified: 07/23/2009
Filesize: 1.02 MB

Jennings, S.G., Geever, M. McGovern, F.M., Francis, J., Spain, G. and Donaghy, T. (1997).- Microphysical and physico-chemical characterisation of atmospheric aerosol at Mace Head. Atmos. Environ., 31, 2795-2808.


Measurements of the aerosol particle size, aerosol volume distribution and aerosol volatility (diameter range 0.1-3.0 μm), aerosol mass (diameter range 0.06-16.0 μm), condensation nuclei (CN) and cloud condensation nuclei (CCN), and black carbon (BC) mass concentration at Mace Head during the EU project Background Maritime Contribution to Atmospheric Pollution in Europe (BMCAPE), obtained over four intensive campaigns during the period between November 1993 and August 1994, are presented. Marine air was found to possess mean accumulation mode (ACM) aerosol particle number concentration., N, of between 100 and 160 cm-3 for the winter and summer seasons. Marine ACM mass ranged in value from about 0.8 to 6 μg m-3. Marine air was found to contain black carbon with episodic mean mass concentrations generally in the range 5-40 ng m-3. The impact of black carbon on the marine environment is also reflected by the moderately positive correlation (r2 in the range 0.23-0.44) found between marine ACM number concentration and BC mass loading, with a higher correlation (r2 = 0.55) found for winter continental air. Black carbon accounted for between 0.6% and 1.2% of the ACM mass loading for marine aerosol at Mace Head, increasing to between 4% and 6% for continental air. Arithmetic mean values of ACM number concentration N and BC mass concentration agree quite well with results from a few other investigators of marine atmospheric aerosol in the North Atlantic.

Distribution and Sea-Air Fluxes of Biogenic Trace Gases in the Eastern Atlantic Ocean Distribution and Sea-Air Fluxes of Biogenic Trace Gases in the Eastern Atlantic Ocean

Date added: 08/06/2000
Date modified: 07/27/2009
Filesize: 1.44 MB

Baker, A. R., S. M. Turner, W. J. Broadgate, A. Thompson, G. B. McFiggans, O. Vesperini, P. D. Nightingale, P. S. Liss, and T. D. Jickells (2000), Distribution and Sea-Air Fluxes of Biogenic Trace Gases in the Eastern Atlantic Ocean, Global Biogeochem. Cycles, 14(3), 871–886.


A number of atmospherically important trace gases (dimethyl sulphide (DMS), methyl iodide (CH3I), and nonmethane hydrocarbons (NMHCs)) were measured simultaneously in the eastern Atlantic Ocean during May 1997. This investigation was part of the U.K. Atmospheric Chemistry Studies in the Oceanic Environment (ACSOE) Community Research Program and covered a 200 by 200 nautical mile (1 nautical mile is 1.852 km) area to the west of the Mace Head Atmospheric Research Station on the coast of Ireland. Different spatial and temporal patterns were observed for each of the gases, showing that distinct sources dominate their production in this region: specific species of phytoplankton (DMS), macroalgae (CH3I), total phytoplankton biomass (isoprene), and photochemistry (ethene). Sea-to-air fluxes of the gases are calculated for near and offshore domains, and their temporal variations are discussed. A simple photochemical box model has been used to assess the contributions of the gas fluxes to the levels of the gases observed at Mace Head. Results show that the area studied may constitute a substantial source of DMS, a weak source of CH3I, a small source of ethene at night, and an insignificant source of isoprene to atmospheric levels of these gases measured at Mace Head in western Ireland.


Photochemical ozone formation in north west Europe and its control Photochemical ozone formation in north west Europe and its control

Date added: 08/07/2003
Date modified: 07/23/2009
Filesize: 635.36 kB

DERWENT, R.G., Jenkin, M.E., Saunders, S.M., Pilling, M.J., Simmonds, P.G., Passant, N.R., Dollard, G.J., Dumitrean, P. and Kent, A., 2003: Photochemical ozone formation in north west Europe and its control. Atmos Environ, 37, 1,983-1,991.


A photochemical trajectory model together with a Master Chemical Mechanism and a highly speciated emission inventory for organic compounds have been used to describe the formation of ozone in north west Europe and to identify the most prolific ozone-forming organic compounds. Observations are reviewed to assess the impact of emission controls on their urban volatile organic compound (VOC) concentration trends with time. The observed trends are then used to deduce the likely trends in episodic peak ozone concentrations and to compare them with observed trends in peak ozone concentrations. It is concluded that it is likely that motor vehicle emission controls have brought about a substantial reduction in episodic peak ozone concentrations in north west Europe during the 1990s.


Mace Head Atmospheric Research Station IGActivities Mace Head Atmospheric Research Station IGActivities

Date added: 07/31/1999
Date modified: 07/24/2009
Filesize: 59.08 kB
Jennings, S.G., 1999. Mace Head Atmospheric Research Station. IGACtivities, No. 18, 14-17.



Small particle concentration fluctuations at a coastal site Small particle concentration fluctuations at a coastal site

Date added: 08/01/2002
Date modified: 07/23/2009
Filesize: 877.43 kB
Vana, M., Jennings, S.G., Kleefeld, C., Mirme, A., and Tamm, E., 2002. Small particle concentration fluctuations at a coastal site, Atmos. Res., 63, pp. 247 – 269.


Aerosol size spectra (d=10 nm–10 μm) were measured with an electrical aerosol spectrometer (EAS) at Mace Head on the west coast of Ireland. Several small aerosol particle (diameter 10–32 nm) concentration bursts were observed during the measurement period. Relationships between the events, air mass trajectories, tide height, and meteorological parameters are examined. Series of bursts were observed when a spectral transformation due to subsequent particle growth from 10 to 56–100 nm can be identified in an Eulerian experiment. Particle growth rates of between 1 and 3 nm/h were determined. These bursts appear in cold and comparatively clean arctic or polar air masses with temperature and relative humidity fluctuations, and do not correlate with low tide in some cases. These episodes, similar to those frequently found in the continental boundary layer, are thought to occur over a wide area and, for clear detection, require stable airflow for a few days. Elevated small-particle concentration events are more common during low tide or shortly after, and are typically associated with low wind speeds. Here, the increased shore exposure during low tide is thought to influence the nucleation and the subsequent growth of these aerosol particles. The occurrences of the bursts are found to depend on local wind direction. The highest d=10–32 nm particle concentrations appeared for wind sectors furthest from the tidal regions when the wind direction was 150–160°(south-easterly). Most of the events occurred during daytime when solar irradiation is most intense.

Temporal patterns, sources, and sinks of C8-C16 hydrocarbons in the atmosphere of Mace Head, Ireland Temporal patterns, sources, and sinks of C8-C16 hydrocarbons in the atmosphere of Mace Head, Ireland

Date added: 08/30/2002
Date modified: 03/07/2010
Filesize: 758.23 kB
Sartin, J. H., C. J. Halsall, L. A. Robertson, R. G. Gonard, A. R. MacKenzie, H. Berresheim, and C. N. Hewitt (2002), Temporal patterns, sources, and sinks of C8-C16 hydrocarbons in the atmosphere of Mace Head, Ireland, J. Geophys. Res., 107(D19), 8099, doi:10.1029/2000JD000232.


During the 1999 New Particle Formation and Fate in the Coastal Environment (PARFORCE) field campaign, 16 C8-C16 volatile organic compounds (VOCs) were identified in the coastal atmosphere of Mace Head, Ireland. Sampling took place over 24 days, with 12 VOCs routinely quantified. Concentrations were observed in the low <10–150 parts per trillion by volume range, with levels typically in the order of aldehydes > ketones ≥ n-alkanes. Concentrations of these compounds were also measured in shoreline surface seawater. No relationship was observed between atmospheric concentrations and high/low tide events. Many VOCs revealed a temporal pattern in the atmosphere, with highest concentrations measured during the early morning and lowest concentrations in the afternoon. The strongest pattern was observed for the n-alkanes. However, this was dependent on the prevailing air mass direction and the local meteorology. A Lagrangian box model was applied to assess this diurnal cycle, using seawater emissions as a source (based on the seawater concentrations and observed wind speeds), and depletion via OH radicals and dilution by entrainment as sinks (using measured [OH] and boundary layer height data). The model gave good agreement to the observed concentrations for selected air mass types, predicting the daytime decrease in VOC concentrations due to OH radical chemistry and boundary layer growth, and the subsequent increase in VOC concentrations toward evening as both oxidation chemistry diminished and the mixing layer height fell.

A burning question. Can recent growth rate anomalies in the greenhouse gases be attributed to l A burning question. Can recent growth rate anomalies in the greenhouse gases be attributed to l

Date added: 08/07/2005
Date modified: 06/30/2009
Filesize: 181.92 kB

P.G. Simmonds,A. J.Manning,R.G. Derwent, P. Ciais,M.Ramonet, V. Kazan and D. Ryall, A burning question. Can recent growth rate anomalies in the greenhouse gases be attributed to large-scale biomass burning events?, Atmos. Environ., 2005, 39, 2513–2517.


Simultaneous in situ measurements of carbon dioxide (CO2) and the principal gases linked to biomass burning at the Mace Head Observatory, Ireland, reveal a strong correlation in 1998-99 and 2002-03, both periods with intense global fires. CO2, carbon monoxide (CO), methane (CH4), hydrogen (H2), ozone (O3) and methyl chloride (CH3Cl), all have similar rates of accumulation during these time frames. These perturbations imply a causal relationship between large-scale biomass burning events and the interannual variability of these gases.


Significant growth in surface ozone at Mace Head, Ireland, 1987–2003 Significant growth in surface ozone at Mace Head, Ireland, 1987–2003

Date added: 08/07/2004
Date modified: 07/23/2009
Filesize: 501.27 kB

Significant growth in surface ozone at Mace Head, Ireland, 1987-2003 P.G. Simmonds, R.G. Derwent, A.L. Manning, G. Spain Atmos. Environ., 38, 4769-4778, 2004



Background ozone O3 observations at Mace Head on the west coast of Ireland since 1987 show a significant positive trend of 0.49 ± 0.19 ppb year-1 through to 2003. Increasing trends are observed for all seasons, with the largest trends during the winter season, 0.63±0.31 ppb year-1 and the smallest trends during the summer, 0.39 ± 0.25 ppb year-1. However, this growth rate has not been consistent over time with a major anomaly evident in 1998-1999. This major O3 perturbation is correlated with variations of CO2, CO, CH4, H2 and CH3Cl, which are likely due to large-scale biomass burning events in tropical and boreal regions during 1997-1999 coupled with an intense El Niño event. Over the 16 years of observations background O3 has increased by about 8 ppb (∼ 24%) in the clean oceanic sectors representative of the Northern Hemisphere marine boundary layer.


Concurrent measurements of OH and ultra-fine particles in the coastal atmosphere Concurrent measurements of OH and ultra-fine particles in the coastal atmosphere

Date added: 08/05/1998
Date modified: 07/27/2009
Filesize: 144.75 kB
O'Dowd, C.D., D.J. Creasey, M. Geever, G. McFiggans, D.E. Heard, J.D. Lee, M.J. Pilling, B.J. Whitaker, M.H. Smith, and S.G. Jennings, Concurrent measurements of OH and ultra-fine particles in the coastal atmosphere, J. Aerosol Sci., 29, s611-s612, 1998, (Ser. No. ACP051).



Factors controlling the nucleation of new aerosol particles in the background atmosphere not easily discernible due to the difficulties associated with measuring aerosol precursors leading to aerosol nucleation along with difficulties in determining new particle chemical composition. It is generally assumed that the primary aerosol precursors species are sulphuric acid and water, although other species such as ammonia and organics have also been implicated. Sulphuric acid is produced in the gas phase via the oxidation of SO2 by the OH radical. Further, OH is likely to also be involved in the oxidation of other precursor species leading to homogeneous heteromolecular nucleation. Simultaneous measurements of OH and ultrafine particles were measured at Mace Head during a campaign in May, 1997. The relationship between the occurrence of ultra-fine particles and the concentration of the OH radical is explored. Aerosol measurements were conducted using three condensation nucleus counters: TSI 3025 (r>1.5 nm); TSI 3022 (r>35nm) and TSI 3010 (r>5nm). Deployment of these three instruments allows determination of ultrafine aerosol concentration by examination of the

difference between the three concentrations. The particle counters were configured for 5Hz sampling in single particle mode and thus, the 3022 and 3010 are off scale at concentrations in excess of 10,000 cm-3 while the 3025 is off scale at 160,OOOcm”. It should be noted that at these concentrations, the condensation particle counters are not quantitatively accurate and can only be interpreted as qualitative. OH measurements were undertaken using the recently developed FAGE technique (Creusey et al, 1997). One typical example of coastal nucleation in anthropogenically influenced air at Mace Head is illustrated in Figure 1. Nucleation events are observed under low tide conditions during daytime. On Julian Day 144, massive concentrations of ultrafine particles are seen at midday and during low tide. Particle concentrations exceeded 150,000 cmm3 and occur shortly after the peak in OH concentration. It is interesting that there are two ultrafine particle peaks which coincide with two OH peaks suggesting that the production of new particles is related to availability of the OH radical. O’Dowd et al. (1998) have shown that nucleation occurs in clean air most days at Mace Head and that these nucleation events relate to low tide events. The measurements presented for this campaign also show that nucleation occurs most days under anthropogenically influenced conditions and that these events require low tide and solar irradiation in order to occur. Thus, it appears that under low tide conditions, there is a sufficient source of aerosol precursor material to promote nucleation. However, it is not clear why, on some days when low tide and solar irradiation occur, nucleation does not always occur. The case presented here suggests that when OH concentrations are drastically reduced, aerosol nucleation no longer proceeds suggesting that the oxidation of aerosol precursors by OH is required for nucleation in this environment.

Aerosol Mass measurement at Mace Head on the West coast of Ireland Aerosol Mass measurement at Mace Head on the West coast of Ireland

Date added: 07/31/1992
Date modified: 07/27/2009
Filesize: 1.1 MB

McGovern, F.M., Jennings, S.G., Spain, T.G., O'Connor, T.C., Krasenbrink, A., Georgi, B., and Below, M. (1992)- Aerosol mass measurements at Mace Head on the west coast of Ireland. J. Aerosol Sci., 23, 5953 - 5956.


Aerosol mass/size measurements have been carried out at the Mace Head research station, on the west coast of Ireland, for a period of over two years. Mass/size distributions were obtained in the size range 0.06-10 μm using Berner low-pressure cascade impactor systems. The distributions obtained reflect the different types of air mass which are encountered at Mace Head. Westerly winds are dominant at the site with the associated air masses being typically maritime. Unimodal mass/size distributirns with the peak mass concentration occurring principally in the 2-4 μm size range were characteristic if these conditions. Continental air masses from Europe are typified by mass/size distributions which have peak values in the submicron size range

Ionization equilibrium in aerosols Ionization equilibrium in aerosols

Date added: 01/01/1961
Date modified: 07/24/2009
Filesize: 3.34 MB
O'Connor, T.C. , Flanagan, V.P., Ionization equilibrium in aerosols, Geofisica Pura E Applicata - Milano, Vol. 50 (1961), pp. 148-154.


Theoretical and experimental investigations were made on the time taken to achieve equilibrium charge distribution on Aitken nuclei. Theory indicates that the fraction of nuclei uncharged approaches its equilibrium value exponentially, with an approximate half time value of 0.693Z/4q and experiment gave good agreement with theory. The efficiency of a polonium-210 alpha ray source in producing ionization equilibrium in aerosols was examined and confirmed. The application of the methods described to the determination of the size of nuclei and to other observations in the free atmosphere are discussed.

Scavenging Of Sub-Micrometre Aerosol Particles By Water Drops Scavenging Of Sub-Micrometre Aerosol Particles By Water Drops

Date added: 07/31/1993
Date modified: 07/06/2009
Filesize: 1.36 MB

Byrne, M.A., and Jennings, S.G. (1993). - Scavenging of submicrometre aerosol particles by water drops. Atmos. Environ., 27A, 2099 - 2105.


Experiments were carried out in order to measure the collection efficiencies, E, with which small-sized water drops (of radii between 400 and 500 um) carrying electrical charge, Q (from 5 x 10^-4 to 22 x 10^-11 C) collect monodisperse aerosol particles of radii between 0.35 and 0.88 um. The measured values of collection efficency were within the range 1-6% and were in good agreement with previous results. the measurements show an increase in aerosol particles radius, drop radius and drop charge

The Electrical conductivity within water droplet clouds The Electrical conductivity within water droplet clouds

Date added: 08/01/1975
Date modified: 07/22/2009
Filesize: 1.58 MB
Jennings,S.G.   (1975)- The electrical conductivity within water droplet clouds. Proc.  4th Conf. Static Electrification. Inst. Phys. Conf. Series, No 27,  34-43.



Studies have been made of the reduction of small positive ion concentration, produced by a weak americium alpha source in the presence of small water droplet clouds. The droplet clouds which possessed values of clou-water content ranging from about 1.0 up to 6 g m-3 and mean radius from 0.75 up to approximately 2.25 μm were produced by a steam condenser method which yielded relatively stable clouds.

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.


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.

Ozone and peroxy radical budgets in the marine boundary layer Modeling the effect of NOx Ozone and peroxy radical budgets in the marine boundary layer Modeling the effect of NOx

Date added: 08/06/1999
Date modified: 07/23/2009
Filesize: 971.22 kB

Cox, R. A. (1999), Ozone and peroxy radical budgets in the marine boundary layer: Modeling the effect of NOx, J. Geophys. Res., 104(D7), 8047–8056.


A one-dimensional box model has been formulated to describe the ozone budget and HOx photochemistry in the marine boundary layer. The model includes a simple description of vertical exchange with the free troposphere and the ocean surface, and a photochemical scheme including oxidation of CO and CO4. Model calculations are compared with data collected during the summer season at two midlatitude coastal sites in the northern and southern hemispheres (Mace Head, Ireland, and Cape Grim, Tasmania). Results using small, prescribed NOx concentrations gave compensation points, where ozone loss by photolysis and physical removal is balanced by its production via NOx chemistry, of ∼30 ppt and ∼15 ppt at the two sites, respectively, in line with conclusions from the observational data. Changes in the dependence of peroxy radical concentrations on solar intensity were also in line with observations. The simple model involving CO and CH4 chemistry should be adequate for defining oxidizing capacity in the unpolluted marine boundary layer.


Backscatter and Extinction in Water Clouds Backscatter and Extinction in Water Clouds

Date added: 07/31/1983
Date modified: 06/30/2009
Filesize: 2.64 MB

Pinnick, R.G., Jennings, S.G., Chylek, P., Ham, C., and Grandy, W.T. Jr. (1983)- Backscatter and extinction in water clouds. J. Geophys. Res., 88, 6787-6796.


An approximate relation between the volume extinction coefficient σe and backscatter coefficient σb of atmospheric cloud at visible and near-infrared wavelengths is derived. The relation is only weakly dependent on the size distribution of droplets and has the form σe/σb=(8π/g){1+k-2/3(<r 4/3>/<r2>) -δ[k2(<r4>/<r2>)+k4/3(< r4/2><r4>/<r2><r2>)]} where the extinction efficiency is approximated by a complex-angular-momentum-theory result and the parameters g and δ are determined by approximating a running mean of the backscatter gain by G(x)=g(1+δx2) (x is droplet size parameter and δ<<1), k is the wave number, and <rn> is the nth moment of the droplet size distribution. To zero order the relation is linear and independent of the droplet size distribution σe=[8π/g(λ)]σb where g(λ) is a slowly varying function of wavelength. At a wavelength λ=1.06 μm the relation is σe (km-1)=18.2 σb (km-1sr-1). Predictions made with this simple zero-order approximation are in good agreement (within 50%) with Mie calculations of extinction and backscatter coefficients based on 156 measurements of cloud droplet spectra in cumulus and stratus type clouds. The linear σe-σb relation is also in agreeement with extinction and backscatter measurements made on laboratory-generated fog droplet distributions. The relation suggests that visible or near-infrared extinction coefficients in cloud of unknown type could be inferred from lidar backscatter measurements alone, without knowledge of the cloud droplet size spectra, barring complications arising from multiple scattering contributions to the lidar return.

Air Pollution Measurements at Macehead Air Pollution Measurements at Macehead

Date added: 08/07/1988
Date modified: 07/27/2009
Filesize: 2.14 MB

Importance of organic and black carbon in atmospheric aerosols at Mace Head, on the West Coast of Ireland (53°19′N, 9°54′W) Importance of organic and black carbon in atmospheric aerosols at Mace Head, on the West Coast of Ireland (53°19′N, 9°54′W)

Date added: 07/31/2002
Date modified: 07/24/2009
Filesize: 146.78 kB

Kleefeld, S., Hoffer, A., Krivacsy, and Jennings, S.G., 2002. Importance of organic and black carbon at Mace Head, on the west coast of Ireland (53 019’N, 9 054’W), Atmos. Environ., 36, pp. 4479-4490.


The mass concentrations of total organic carbon (TC) and its chemical fractions, water-soluble organic carbon (WSOC), water-insoluble organic carbon (WISOC), and black carbon (BC), were determined in marine aerosols, which were collected during the period July 1998-September 1999 at the Mace Head Atmospheric Research Station on the west coast of Ireland. In addition, mass concentrations of major inorganic ions, like non-sea-salt (NSS) sulphate, and mass concentrations of dicarboxylic acids have been measured separately within the water-soluble aerosol fraction. The aerosol samples were classified into clean marine aerosol samples and modified marine aerosol samples according to the origin of air masses arriving at Mace Head, and using BC as a tracer for anthropogenic pollution. Following this classification, the data set was further divided into samples taken during summertime and wintertime. An average TC mass concentration of 591±75 ng/m3 was determined for all aerosol samples taken at Mace Head. WSOC was found to be the dominating fraction in modified marine aerosol samples, followed by WISOC and BC, whereas in clean marine aerosol samples WISOC was the main fraction, followed by WSOC, and BC. A comparison of the mass concentration of the water-soluble organic matter to the main water-soluble inorganic component, NSS sulphate, gave an average ratio of 0.72±0.10, which increased to 1.59±0.23 when considering solely clean marine aerosol samples. The dominating dicarboxylic acid found in carbonaceous aerosols at Mace Head was oxalic acid, followed by malonic acid. Both diacids were responsible for about 14±2% of the WSOC (in terms of carbon).

Aerosol distribution over Europe a model evaluation study with Aerosol distribution over Europe a model evaluation study with

Date added: 08/01/2008
Date modified: 07/27/2009
Filesize: 1.41 MB

Langmann, B. Varghese, E. Marmer, E. Vignati, J. Wilson, P. Stier and C. O’Dowd, Aerosol distribution over Europe: A model evaluation study with detailed aerosol microphysics, Atmos. Chem. Phys., in press, 2008.


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.

A model prediction of the yield of CCN from coastal nucleation events A model prediction of the yield of CCN from coastal nucleation events

Date added: 07/31/2002
Date modified: 07/27/2009
Filesize: 352.77 kB
Liisa Pirjola, Colin O'Dowd, Markku Kulmala, A model prediction of the yield of CCN from coastal nucleation events, J. Geophys. Res., 107, 10.1029/2000JD000213, 2002.


The formation and evolution of new particles during coastal nucleation events are examined using the aerosol dynamic and gas-phase chemistry model AEROFOR2. Coastal regions are known to be a strong source of natural aerosol particles and are also strong sources of biogenic vapors which can condense onto aerosol particles, thus resulting in particle growth. A number of model simulations were performed to determine the instantaneous nucleation rate along with the source rate of a generic biogenic vapor leading to the observed particle size distributions which indicate the rapid appearance of ∼105–106 cm−3 nucleation mode particles in this environment. Model calculations suggest values of 3 × 105 cm−3 s−1 to 3 × 106 cm−3 s−1 for the instantaneous nucleation rate and a value of 5 × 107 cm−3 s−1 for the condensable vapor source rate in order to reproduce the observed concentrations. A significant fraction of these new particles survive to grow into cloud condensation nuclei (CCN) sizes for supersaturations typically encountered in boundary layer clouds during subsequent evolution over 3 days under clear-sky conditions, thus contributing to the indirect radiative effect of aerosols. The amount of CCN is mainly affected by coagulation between particles and condensation of the biogenic vapor and, to a lesser extent, by condensation of sulphuric acid formed by DMS oxidation. In all simulated cases, an increase of more than 100% in CCN concentration, for supersaturations >0.35% was observed.

Overview of the international project on biogenic aerosol formation in the boreal forest Overview of the international project on biogenic aerosol formation in the boreal forest

Date added: 07/31/2001
Date modified: 07/22/2009
Filesize: 727.68 kB

Kulmala, M., K. Hämeri, P.P. Aalto, J.M. Makela, L. Pirjola, E.D. Nilsson, G. Buzorius, U. Rannik, M. Dal Maso, W. Seidl, T. Hoffmann, R. Janson, H-C. Hansson, Y. Viisanen, and A. Laaksonen, C.D. O'Dowd, Overview of the international project on biogenic aerosol formation in the boreal forest (BIOFOR), Tellus B, 324-343, 2001.


Aerosol formation and subsequent particle growth in ambient air have been frequently observed at a boreal forest site (SMEAR II station) in Southern Finland. The EU funded project BIOFOR (Biogenic aerosol formation in the boreal forest has focused on: (a) determination of formation mechanisms of aerosol particles in the boreal forest site; (b) verification of emissions of secondary organic aerosols from the boreal forest site; and (c) quantification of the amount of condensable vapours produced in photochemical reactions of biogenic volatile organic compounds (BVOC) leading to aerosol formation. The approach of the project was to combine the continuous measurements with a number of intensive field studies. These field studies were organised in three periods, two of which were during the most intense particle production season and one during a non-event season. Although the exact formation route for 3 nm particles remains unclear, the results can be summarised as follows: Nucleation was always connected to Arctic or Polar air advecting over the site giving conditions for a stable nocturnal boundary layer followed by a rapid formation and growth of a turbulent convective mixed layer closely followed by formation of new particles. The nucleation seems to occur in the mixed layer or entrainment zone. However two more prerequisites seem to be necessary. A certain threshold of high enough sulphuric acid and ammonia concentrations is probably needed as the number of newly formed particles Was correlated with the product of the sulphuric acid production and the ammonia concentrations No such correlation was found with the oxidation products of terpenes. The condensation sink, i.e., effective particle area, is probably of importance as no nucleation was observed at high values of the condensation sink. From measurement of the hygroscopic properties of the nucleation particles it was found that inorganic compounds and hygroscopic organic compounds contributed both to the particle growth during daytime while at night time organic compounds dominated. Emissions rates for several gaseous compounds was determined. Using four independent ways to estimate the amount of the condensable vapour needed for observed growth of aerosol particles we get an estimate of 2-10 × 107 vapour molecules cm-3. The estimations for source rate give 7.5-11 x 104 cm-3 s-1. These results lead to the following conclusions: The most probable formation mechanism is ternary nucleation (water-sulphuric acid-ammonia). After nucleation, growth into observable sizes (≥3 nm) is required before new particles appear. The major part of this growth is probably due to condensation of organic vapours. However, there is lack of direct proof of this phenomenon because the composition of 1-5 nm size particles is extremely difficult to determine using the present state-of-art instrumentation.

Atmospheric mercury distribution in Northern Europe and in Atmospheric mercury distribution in Northern Europe and in

Date added: 08/06/2001
Date modified: 06/30/2009
Filesize: 238.69 kB

I. Wangberg, J. Munthe, N. Pirrone, A. Iverfeldt, E. Bahlman, P. Costa, R. Ebinghaus, X. Feng, R. Ferrara, K. Gardfeldt, H. Kock, E. Lanzillotta, Y. Mamane, F. Mas, E. Melamed, Y. Osnat, E. Prestbo, J. Sommar, S. Schmolke, G. Spain, F. Sprovieri, G. Tuncel, Atmospheric mercury distribution in Northern Europe and in the Mediterranean region, Atmospheric EnvironmentVolume 35, Issue 17, , June 2001, Pages 3019-3025.



Mercury species in air have been measured at five sites in Northwest Europe and at five coastal sites in the Mediterranean region during measurements at four seasons. Observed concentrations of total gaseous mercury (TGM), total particulate mercury (TPM) and reactive gaseous mercury (RGM) were generally slightly higher in the Mediterranean region than in Northwest Europe. Incoming clean Atlantic air seems to be enriched in TGM in comparison to air in Scandinavia. Trajectory analysis of events where high concentrations of TPM simultaneously were observed at sites in North Europe indicate source areas in Central Europe and provide evidence of transport of mercury on particles on a regional scale.


Advances in characterization of size resolved organic matter in marine aerosol over the North Atlantic Advances in characterization of size resolved organic matter in marine aerosol over the North Atlantic

Date added: 08/01/2004
Date modified: 07/27/2009
Filesize: 552.34 kB
Cavalli,F., M.C. Facchini, S. Decesari, M. Mircea, L. Emblico, S. Fuzzi, D. Ceburnis, Y.J. Yoon and C.D. O’Dowd, J.-P. Putaud and A. Dell’Acqua, Advances in characterization of size resolved organic matter in marine aerosol over the North Atlantic, J. Geophys. Res, doi:10.1029/2004JD0051377, 2004.


Size-segregated marine aerosols were collected at Mace Head Atmospheric Research Station (Ireland) during spring and autumn 2002 corresponding with the phytoplankton bloom periods in the North Atlantic. Strict control of the sampling, air mass back trajectory analysis, and analysis of pollutant tracers allowed the selection of a set of samples representative of clean marine conditions. A comprehensive chemical characterization of both (1) water-soluble and water-insoluble organic fraction and (2) water-soluble inorganic ions was performed. The selected samples illustrated a consistent picture in terms of chemical composition. The supermicron mode predominantly comprises sea-salt aerosol with a mass concentration of 10.16 ± 0.80 μg m−3, the remainder being non-sea-salt (nss) sulphate, 0.03 ± 0.01 μg m−3, and nitrate, 0.13 ± 0.04 μg m−3. By comparison, the mass of sea salt, nss sulphate, and nitrate in the submicron mode is found to be 0.39 ± 0.08 μg m−3, 0.26 ± 0.04 μg m−3, and 0.02 ± 0.01 μg m−3, respectively. Water-soluble organic carbon (WSOC) is observed in the submicron mode with a mass concentration of 0.25 ± 0.04 μg m−3, comparable to that of nss sulphate, and in the supermicron mode with a mass concentration of 0.17 ± 0.04 μg m−3. The WSOC to total carbon (TC) ratio is found to be 0.20 ± 0.12 for the submicron fraction and 0.29 ± 0.08 for the supermicron fraction, while the black carbon (BC) to TC ratio is, on average, 0.032 ± 0.001 for both aerosol modes. The remaining carbon, water-insoluble organic carbon, contributes 0.66 ± 0.11 μg m−3 and 0.26 ± 0.06 μg m−3 to the submicron and supermicron modes, respectively and, thus, represents the dominant submicron aerosol species. Furthermore, the WSOC chemical composition comprises mainly aliphatic and only partially oxidized species and humic-like substances, resulting in appreciable surface-active properties. The observed organic matter chemical features (size-dependent concentration, hydrophobic nature of a substantial fraction of the organic matter, and low oxidized and surface-active WSOC species) are consistent with the hypothesis of a primary marine source; bubble-bursting processes, occurring at the surface of the North Atlantic Ocean during phytoplankton blooms, effectively transfer organic matter into marine aerosol particles, particularly enriching the fine-aerosol fraction.

Impact of halogen monoxide chemistry upon boundary layer OH and HO 2 concentrations at a coasta Impact of halogen monoxide chemistry upon boundary layer OH and HO 2 concentrations at a coasta

Date added: 08/06/2005
Date modified: 07/24/2009
Filesize: 187.73 kB

Bloss, W. J.; Lee, J. D.; Johnson, G. P.; Sommariva, R.; Heard, D. E.; Saiz-Lopez, A.; Plane, J. M. C.; McFiggans, G.; Coe, H.; Flynn, M.; Williams, P.; Rickard, A. R.; Fleming, Z. L. Impact of halogen monoxide chemistry upon boundary layer OH and HO2 concentrations at a coastal site Geophys. Res. Lett., Vol. 32, No. 6, L06814 10.1029/2004GL022084


The impact of iodine oxide chemistry upon OH and HO2 concentrations in the coastal marine boundary layer has been evaluated using data from the NAMBLEX (North Atlantic Marine Boundary Layer Experiment) campaign, conducted at Mace Head, Ireland during the summer of 2002. Observationally constrained calculations show that under low NOx conditions experienced during NAMBLEX (NO ≤ 50 pptv), the reaction IO + HO2 → HOI + O2 accounted for up to 40% of the total HO2 radical sink, and the subsequent photolysis of HOI to form OH + I comprised up to 15% of the total midday OH production rate. The XO + HO2 (X = Br, I) reactions may in part account for model overestimates of measured HO2 concentrations in previous studies at Mace Head, and should be considered in model studies of HOx chemistry at similar coastal locations.

Condensation Nuclei In maritime Air Condensation Nuclei In maritime Air

Date added: 08/07/1966
Date modified: 07/27/2009
Filesize: 858.97 kB
O'Connor, Condensation Nuclei in Maritime Air, Journal de Recherches Atmospheriques, Vol II, 2 annee (1966), no 2-3, pp 181-184


Data is reported on the concentration of condensation nuclei, their size and the fraction uncharged, in maritime air at a station on the west coast of Ireland well away from sources of man-made pollution. These are correlated with some meteorological paratmeters and the state of the ocean. These observations were made mainly with on-shore winds and they supplement those of O'Connor, Sharkey and Flanagan, in Q.J..R.M.S., 87,1961,pp. 105-8.

The concentration of nuclei per cm3 varied from about 100 to 12,500 but was usually less than 1,000. The size of the nuclei decreased with increasing concentration with an average value of about 3.5 X 10^-6 cm for their radii. It did not depend markedly on the relative humidity.

Ground-based Retrieval of Continental and Marine Warm Cloud Microphysics Ground-based Retrieval of Continental and Marine Warm Cloud Microphysics

Date added: 08/05/2011
Date modified: 08/05/2011
Filesize: 3.85 MB

Martucci, G. and C.D. O’Dowd, Ground-based Retrieval of Continental and Marine Warm Cloud Microphysics. Atmos, Meas. Techs.. Diss., 4, 4825-4865, doi:10.5194/amtd-4-4825-2011,, 2011

Abstract. A technique for retrieving warm cloud microphysics using synergistic ground based remote sensing instruments is presented. The SYRSOC (SYnergistic Remote Sensing Of Cloud) technique utilises a Ka-band Doppler cloud RADAR, a LIDAR-ceilometer and a multichannel microwave radiometer. SYRSOC retrieves the main microphysical parameters such as cloud droplet number concentration (CDNC), droplets effective radius (reff), cloud liquid water content (LWC), and the departure from adiabatic conditions within the cloud. Two retrievals are presented for continental and marine stratocumulus formed over the Mace Head Atmospheric Research Station. Whilst the continental case exhibited high CDCN (N = 382 cm−3; 10th-to-90th percentile [9.4–842.4] cm−3) and small mean effective radius (reff = 4.3; 10th-to-90th percentile [2.9–6.5] μm), the marine case exhibited low CDNC and large mean effective radius (N = 25 cm−3, 10th-to-90th percentile [1.5–69] cm−3; reff = 25.6 μm, 10th-to-90th percentile [11.2–42.7] μm) as expected since the continental air at this location is typically more polluted than marine air. The large reff of the marine case was determined by the contribution of drizzle drops (large radii and few occurrences) and in fact the modal radius was reffMOD = 12 μm (smaller radius and large occurrences). The mean LWC was comparable for the two cases (continental: 0.19 g m−3; marine: 0.16 g m–3) but the 10th–90th percentile range was wider in marine air (continental: 0.11–0.22 g m−3; marine: 0.01–0.38 g m−3). The calculated algorithm uncertainty for the continental and marine case for each variable was, respectively, σN=141.34 cm−3 and 11.5 cm−3, σreff=0.8 μm and 3.2 μm, σLWC = 0.03 g m−3 and 0.03 g m−3. The retrieved CDNC are compared to the cloud condensation nuclei concentrations and the best agreement is achieved for a super-saturation of 0.1 % in the continental case and between 0.1 %–0.75 % for the marine stratocumulus. The retrieved reff at the top of the clouds are compared to the MODIS satellite reff: 7 μm (MODIS) vs 6.2 μm (SYRSOC) and 16.3 μm (MODIS) vs. 17 μm (SYRSOC) for continental and marine cases, respectively. The combined analysis of the CDNC and the reff, for the marine case shows that the drizzle modifies the droplet size distribution and reff especially if compared to reffMOD. The study of the cloud subadiabaticity and the LWC shows the general sub-adiabatic character of both clouds with more pronounced departure from adiabatic conditions in the continental case due to the shallower cloud depth and more significant mixing with dry tropospheric air.

A modeling study of iodine chemistry in the marine boundary layer A modeling study of iodine chemistry in the marine boundary layer

Date added: 08/06/2000
Date modified: 07/27/2009
Filesize: 1.4 MB

McFiggans, G., J. M. C. Plane, B. J. Allan, L. J. Carpenter, H. Coe, and C. O'Dowd (2000), A modeling study of iodine chemistry in the marine boundary layer, J. Geophys. Res., 105(D11), 14,371–14,385.


An observationally constrained photochemical box model has been developed to investigate the atmospheric chemistry of iodine in the marine boundary layer, motivated by recent measurements of the iodine monoxide (IO) radical (Allan et al., this issue). Good agreement with the time series of IO measured at a midlatitude coastal station was achieved by using a reaction scheme that included recycling of iodine through marine aerosol. The strong diurnal variation in IO observed in the subtropical Atlantic was satisfactorily modeled by assuming a constant concentration of iodocarbons that photolyzed to produce roughly 1 × 104 iodine atoms cm−3 s−1 at midday. The significance of the occurrence of IO at concentrations of up to 4 parts per trillion in the marine boundary layer was then considered from three angles. First, the iodine-catalyzed destruction of ozone was shown to be of a magnitude similar to that caused by odd-hydrogen photochemistry, with up to 13% of the available ozone destroyed per day in a marine air mass. Second, the enrichment factor of iodine in marine aerosol compared with surface seawater was predicted to increase to values of several thousand, in sensible accord with observations. Most of the enrichment should be due to the accumulation of iodate, although other iodine species may also be present, depending on the rate of aerosol recycling. Third, the denoxification of the marine boundary layer was found to be significantly enhanced as a result of aerosol uptake of IONO2, formed from the recombination of IO with NO2.


Airborne measurements of nucleation mode particles I coastal nucleation and growth rates Airborne measurements of nucleation mode particles I coastal nucleation and growth rates

Date added: 08/01/2006
Date modified: 06/30/2009
Filesize: 1.47 MB

O’Dowd, C.D, Y. J. Yoon, W. Junkerman, P. P. Aalto, and H. Lihavainen, Airborne Measurements of Nucleation Mode Particles I: Coastal Atlantic Nucleation Events. Atmos. Chem. Phys. Discuss, 6, 8097-8123, 2006.


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 km) growth rates can be as high as 123–171 nm h−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.

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.

The composition of nucleation and Aitken modes particles during coastal nucleation events evidence f The composition of nucleation and Aitken modes particles during coastal nucleation events evidence f

Date added: 08/01/2006
Date modified: 07/07/2009
Filesize: 3.14 MB

Vaattovaara, P., P. E. Huttunen, Y. J. Yoon, J. Joutsensaari, K. E. J. Lehtinen, C. D. O’Dowd, and A. Laaksonen,The composition of nucleation and Aitken modes particles during coastal nucleation events: evidence for marine secondary organic contribution, Atmos. Chem. Phys. Discuss., 6, 3337–3379, 2006.


Newly-formed nanometer-sized particles have been observed at coastal and marine environments worldwide. Interestingly, organic species have so far not been detected in those newly-formed nucleation mode particles. In this study, we applied the UFO-TDMA (ultrafine organic tandem differential mobility analyzer) method to study the possible existence of an organic fraction in recently formed coastal nucleation mode particles (d<20 nm) at the Mace Head research station. Furthermore, effects of those nucleation events to potential CCN (cloud condensation nuclei) were studied. The coastal events were typical for the Mace Head region and they occurred at low tide conditions during efficient solar radiation and high biological activity (HBA, i.e. a high mass concentration of chlorophyll a of the ocean) in spring 2002. Additionally, a PHA-UCPC (pulse height analyzer ultrafine condensation particle counter) technique was used to study the composition of newly-formed particles formed in low tide conditions during a lower biological activity (LBA, i.e. a lower mass concentration of chlorophyll a of the ocean) in October 2002. The overall results of the UFO-TDMA and the PHA-UCPC measurements indicate that those coastally/marinely formed nucleation mode particles include a remarkable fraction of secondary organic products, beside iodine oxides, which are likely to be responsible for the nucleation. During clean marine air mass conditions, the origin of those secondary organic oxidation compounds can be related to marine/coastal biota and thus a major fraction of the organics may originate from biosynthetic production of alkenes such as isoprene and their oxidation by iodine, hydroxyl radical, and ozone. During modified marine conditions, also anthropogenic secondary organic compounds may contribute to the nucleation mode organic mass, in addition to biogenic secondary organic compounds. Thus, the UFO-TDMA results suggest that the secondary organic compounds may, in addition to being significant contributors to the nucleation mode processes, accelerate the growth of freshly nucleated particles and increase their survival probability to CCN and even larger radiatively active particle sizes. The results give new insights to the coastal/marine particle formation, growth, and properties. The marine biota driven secondary organic contributions to coastal/marine particle formation and composition can be anticipated in other species specific biologically active oceans and fresh-waters areas around the world and thus, they may be significant also to the global radiative bugdet, atmosphere-biosphere feedbacks, and climate change.

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.

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