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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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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.


Abstract


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.

Non-Methane hydrocarbon measurements in Ireland Non-Methane hydrocarbon measurements in Ireland

Date added: 08/06/2003
Date modified: 07/27/2009
Filesize: 32.07 kB
Noone, C A.Non-methane hydrocarbon measurements in Ireland [EGU04-A-05179].

Abstract

 

The measurement of non-methane hydrocarbons (NMHCs) has become increasingly important in recent years in light of their role as precursors in the formation of ozone and their potential impact on human health. In this poster, observations of diurnal and seasonal cycles of NMHCs (C$_2$-C$_8$) are reported for measurements observed at Mace Head, Ireland from 2002-2003. The remote coastal research station of Mace Head, Co. Galway is unique in Europe offering an opportunity to study the Northern Hemispheric background atmosphere, as well as emissions from Europe. Continuous ground-based data collected at Mace Head allows air mass characterisation and model estimates of ozone production with polluted
plumes to be made.

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.

The effect of particle size distribution and complex index of refraction of atmospheric aerosols... The effect of particle size distribution and complex index of refraction of atmospheric aerosols...

Date added: 08/01/1981
Date modified: 07/10/2009
Filesize: 1.44 MB
Jennings, S.G. (1981)- The effect of particle size distribution and complex index of refraction of atmospheric aerosols in the visual range. Proc. of the Ninth International Conference in Atmospheric Aerosol, Condensation and Ice Nuclei, Galway University Press, 415 - 420.

Abstract

 

A comprehensive study has been made of the effect of particle size distribution and complex index of refraction on the visual range, with a wavelengrth lamada of 0.55 micrometres. Calculations were performed by using a generalized polydisperse Mie scattering theory, which makes the assumption that the particles are spherical. Several workers have shown that a lognormal distribution can well represent different types of atmospheric aerosol over a wide range of natural conditions. A lognormal distribution wth geometric mean radius rg varying from 0.005 to 10 micrometers and geometric standard deviation sigmag varying from 1.5 up to 3.0 was used in the calculations.

 


 

Seasonal variation of the aerosol light scattering coefficient in marine air of the North-East Atlan Seasonal variation of the aerosol light scattering coefficient in marine air of the North-East Atlan

Date added: 11/17/2011
Date modified: 11/17/2011
Filesize: 677.22 kB

Vaishya, A., S.G. Jennings and C.D. O'Dowd, Seasonal variation of the aerosol light scattering coefficient in marine air of the North-East Atlantic, Adv. Met., Volume 2011, Article ID 170490, doi:10.1155/2011/170490, 2011.

 

  


Aerosol light scattering measurements were carried out using a TSI 3563 Nephelometer at the Mace Head Atmospheric Research Station, on the west coast of Ireland from year 2001–2010. A strong seasonal trend in the aerosol light scattering coefficient at 550nm (σscat), for clean marine air masses, is observed with a high σscat value, [average (geometric mean)] of 35.3Mm1 (29.5Mm1), in January and a low σscat value of 13.7Mm1 (10.2Mm1), in July. This near threefold increase in the σscat value during the winter season is because of the large contribution of wind-speed generated sea-salt particles in the marine boundary layer. A high positive correlation coefficient of 0.82 was found between the percentage occurrence of relatively large A° ngstro¨m exponent (A° ) values (>1.2) and the percentage occurrence of lower σscat values (5–15Mm1) in the summer season. σscat and wind-speed have a high positive correlation coefficient of 0.88 whereas °Aand wind-speed have a negative correlation coefficient of 0.89. °A values during the summer months indicate the dominance of sub-μm particles thus indicating the contribution of non-sea-salt sulphate and organics towards the σscat as these species show an enhanced concentration during the summer months

 

Airborne trace gas measurements over open ocean and coastal regions upwind of Mace Head, Irelan Airborne trace gas measurements over open ocean and coastal regions upwind of Mace Head, Irelan

Date added: 08/06/2003
Date modified: 07/27/2009
Filesize: 13.7 kB

Ruth Purvis, Ally Lewis, Jim McQuaid, "Airborne Trace Gas Measurements Over Open Ocean and Coastal Regions Upwind of Mace Head, Ireland", Geophysical Research Abstracts Volume 5, 2003.


Abstract

 

The spatial distribution of a number of trace species has been determined in marine boundary layer (MBL) and free troposphere (FT) air around the Mace Head Atmospheric Research Station, Ireland. CO and ozone measurements were made onboard NERC Dornier 228-101 research aircraft operated by the Airborne Remote Sensing Facility during the SNAP (Supporting NAMBLEX from an Airborne Platform) campaign in August 2002. High frequency whole air sampling from the aircraft with ground analysis using GC-FID was used for C2 - C6 hydrocarbons mixing ratios. The campaign was conducted in conjunction with the ground based NAMBLEX (North Atlantic Marine Boundary Layer Experiment) campaign carried out at Mace Head. The distribution of trace species was investigated in both coastal regions and above the deep waters beyond the continental shelf. A vertical gradient in concentration of hydrocarbonand sulphur species with known oceanic sources was observed in the MBL over both oceanic regions when compared to anthropogenic tracers such as acetylene and CO. Under clear sky conditions typical maximum mixing ratios were MBL ethene 78 pptV: FT ethene 10 pptV: MBL DMS: 89 pptV: FT DMS 21 pptV. Elevated mixing ratios of species with oceanic origin were observed in the lower most FT in regions experiencing strong convective activity associated with cumulus cells. Vertical profiles centred over the field sit showed good agreement between ground based and airbornehydrocarbon measurements taken within the MBL. The MBL upwind of Mace Head appeared well mixed with respect to both NMHCs, CO and ozone. Above 2 km showed distinct layers with free tropospheric ozone values of 50 ppbV contrasting typical MBL values of less than 30 ppbV. Flights indicate aboundary layer height of approximately 1200 m. The observations confirm that for these species the surface site measurements are generally representative of the marine boundary layer as a whole but not of the air mass above.

Boundary layer concentrations and landscape scale emissions of volatile organic compounds in early s Boundary layer concentrations and landscape scale emissions of volatile organic compounds in early s

Date added: 08/01/2007
Date modified: 07/10/2009
Filesize: 579.61 kB

Happanala, S., J. Rinne, H. Hakola, L. Laakso, H. Lihavainen, R. Janson, C O’Dowd and M Kulmala. Boundary layer concentrations and landscape scale emissions of volatile organic compounds in early spring. Atmos. Chem.. Phys., Atmos. Chem. Phys., 7, 1869–1878, 2007.


Abstract


Boundary layer concentrations of several volatile organic compounds (VOC) were measured during two campaigns
in springs of 2003 and 2006. The measurements were conducted over boreal landscapes near SMEAR II measurement
station in Hyyti¨al¨a, Southern Finland. In 2003 the measuremens were performed using a light aircraft and in
2006 using a hot air balloon. Isoprene concentrations were low, usually below detection limit. This can be explained
by low biogenic production due to cold weather, phenological stage of the isoprene emitting plants, and snow cover.
Monoterpenes were observed frequently. The average total monoterpene concentration in the boundary layer was
33 pptv. Many anthropogenic compounds such as benzene, xylene and toluene, were observed in high amounts. Ecosystem scale surface emissions were estimated using a simple mixed box budget methodology. Total monoterpene emissions varied up to 80μgm−2 h−1, -pinene contributing typically more than two thirds of that. These emissions were somewhat higher that those calculated using emission algorithm. The highest emissions of anthropogenic compounds were those of p/m xylene.

.

Coastal new particle formation Environmental conditions and aerosol physico-chemical characteristics during nucleation bursts Coastal new particle formation Environmental conditions and aerosol physico-chemical characteristics during nucleation bursts

Date added: 07/31/2002
Date modified: 07/27/2009
Filesize: 1.31 MB
Colin D. O'Dowd, Kaarle Hämeri, Jyrki Mäkelä, Minna Väkeva, Pasi Aalto, Gerrit de Leeuw, Gerard Kunz, Harald Berresheim, Hans-Christen Hansson, Edo Becker, Andrew G. Allen, Roy M. Harrion, Christoph Kleefeld, Michael Geever, S. Gerard Jennings, Harald Berresheim, and Markku Kulmala.Coastal new particle formation: Environmental conditions and aerosol physico-chemical characteristics during nucleation bursts. J. Geophys. Res. 107, 10.1029/2000JD000206, 2002.

Abstract


Nucleation mode aerosol was characterized during coastal nucleation events at Mace Head during intensive New Particle Formation and Fate in the Coastal Environment (PARFORCE) field campaigns in September 1998 and June 1999. Nucleation events were observed almost on a daily basis during the occurrence of low tide and solar irradiation. In September 1998, average nucleation mode particle concentrations were 8600 cm−3 during clean air events and 2200 cm−3 during polluted events. By comparison, during June 1999, mean nucleation mode concentrations were 27,000 cm−3 during clean events and 3350 cm−3 during polluted conditions. Peak concentrations often reached 500,000–1,000,000 cm−3 during the most intense events and the duration of the events ranged from 2 to 8 hours with a mean of 4.5 hours. Source rates for detectable particle sizes (d > 3 nm) were estimated to be between 104 and 106 cm−3 s−1 and initial growth rates of new particles were as high as 0.1–0.35 nm s−1 at the tidal source region. Recently formed 8 nm particles were subjected to hygroscopic growth and were found to have a growth factor of 1.0–1.1 for humidification at 90% relative humidity. The low growth factors implicate a condensable gas with very low solubility leading to detectable particle formation. It is not clear if this condensable gas also leads to homogeneous nucleation; however, measured sulphuric acid and ammonia concentration suggest that ternary nucleation of thermodynamically stable sulphate clusters is still likely to occur. In clear air, significant particle production (>105 cm−3) was observed with sulphuric acid gas-phase concentration as low as 2 × 106 molecules cm−3 and under polluted conditions as high as 1.2 × 108 molecules cm−3.

Modelling OH, HO2, and RO2 radicals in the marine boundary layer 1. Model construction and compa Modelling OH, HO2, and RO2 radicals in the marine boundary layer 1. Model construction and compa

Date added: 08/06/1999
Date modified: 07/27/2009
Filesize: 1.29 MB

Carslaw, N., D. J. Creasey, D. E. Heard, A. C. Lewis, J. B. McQuaid, M. J. Pilling, P. S. Monks, B. J. Bandy, and S. A. Penkett (1999), Modeling OH, HO2, and RO2 radicals in the marine boundary layer 1. Model construction and comparison with field measurements, J. Geophys. Res., 104(D23), 30,241–30,255.


Abstract


An observationally constrained box model has been constructed to investigate radical chemistry at the Mace Head Atmospheric Observatory, a remote marine location on the west coast of Ireland. The primary aim of the model has been to model concentrations of the hydroxyl (OH), hydroperoxy (HO2), and the sum of peroxy Σ([HO2]+[RO2]) radicals measured by in situ instruments at this location. The model used in these studies consists of about 1670 reactions and 500 species, and model predictions of radical concentrations have been evaluated against field data. In order to further understand the chemistry, the model has been reduced using sensitivity analysis on both a clean and a semipolluted day. For reduced mechanisms that predict the concentrations of OH and HO2 to within 5% of the full mechanism, the semipolluted day can be represented using 279 species and 986 reactions, and the clean day using 249 species and 894 reactions. A further reduction has been applied whereby the reduced mechanisms predict concentrations of OH and HO2 to within 20% of the full mechanism for the daytime hours. In this way, the OH and HO2 concentrations on the semipolluted day can be represented by 42 species and 64 reactions, and the clean day by 17 species and 25 reactions. We show that these reduced mechanisms are generally applicable for this location under broadly similar conditions. Simple steady state expressions have also been derived to represent the chemistry at this location, allowing the concentrations of OH and HO2 to be deduced analytically. The expressions are based on the reduced mechanisms and on a further analysis of the reaction rates. Finally, an uncertainty analysis has been carried out to quantify the effects of propagation of uncertainties in the rate parameters and constrained concentrations through to the calculated radical concentrations in the model. For model concentrations of OH, HO2, and Σ([HO2]+[RO2]) radicals, the 2σ uncertainties are 31, 21, and 25%, respectively for clean air, and 42, 25, and 27% for semipolluted air.

Deposition in ionic Diffussion Deposition in ionic Diffussion

Date added: 08/07/1968
Date modified: 07/27/2009
Filesize: 1.69 MB

TC OConnor, F Anderson, PJ Nolan, Electrostatic Deposition in ionic Diffussion ,Proceeding of the Royal Irish Academy 1968, Volume 66 Section A No. 5


Abstract

 

Errors in the determination of ionic diffusion coefficients caused by the neglect of electrostatic deposition are examined. Correction formulae applicable to low ionic concentrations are derived for cylindrical channels. These are similiar to the Fuchs formulae for rectangular channels. Formulae applicable in the case of high ionic concentration are also derived.

For singly charged particles the correction tot the diffusion coefficient under the usual experimental conditions is about two or three per cent. The error becomes large when the number electronic charges per ion aproaches 100. Previous Dublin experiments with multiply charged nuclei are examined in this connection and corrections applied. The Corrections do not invalidate the main conclusion of these experiments that the Einstein equation B=D/KT does not apply in the absence of charge equilibrium.

European greenhouse gas emissions estimated from continuous atmospheric measurements and radon 222 at Mace Head, Ireland European greenhouse gas emissions estimated from continuous atmospheric measurements and radon 222 at Mace Head, Ireland

Date added: 07/31/2000
Date modified: 07/24/2009
Filesize: 1.37 MB

Biraud, S., Ciais, P., Ramonet, M., Simmonds, P.G., Kazan, V., Monfray, P., O'Doherty, S., Spain, T.G., and Jennings, S.G. (2000).European greenhouse gas emissions estimated from continuous atmospheric measurements and Radon 222 at Mace Head, Ireland. J. Geophys. Res., 105, 1351-1366.


Abstract


Flux estimates of CO2, CH4, N2O. and CFCs over western Europe have been inferred from continuous atmospheric records of these species at the atmospheric research station of Mace Head, Ireland. We use radon (222Rn) which has a fairly uniform source over continents as a reference compound to estimate unknown sources of other species. The correlation between each species and 222Rn is calculated for a suite of synoptic events that have been selected in the Mace Head record over the period 1996/97. In the following, we describe the method and its uncertainties, and we establish data selection criteria that minimize the influence of local sources over Ireland, in the vicinity of the station, in order to select synoptic events originating from western Europe. We estimate western European flux densities of 45-30 103 kg C km-2 month-1 during wintertime for CO2, of 4.8-3.5 10 kg CH4 km-2 yr-1, 475-330 kg N2O km-2 yr-1. 2.5-1.8 kg CFC-11 km-2 yr-1 for CFC-11, and 4.2-2.9 kg CFC-12 km-2 yr-1 for CFC-12. Our estimates are independent, although in good agreement with those produced by inventories, except for CFC- 1 where our estimate is much lower than the inventory.

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

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

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


Abstract


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

The effect of clouds on aerosol growth in the rural atmosphere The effect of clouds on aerosol growth in the rural atmosphere

Date added: 08/06/2000
Date modified: 07/07/2009
Filesize: 206.46 kB

Colin D. O'Dowd, Jason A. Lowe, Michael H. Smith, The effect of clouds on aerosol growth in the rural atmosphere, Atmospheric ResearchVolume 54, Issue 4, , August 2000, Pages 201-221.


Abstract


Measurements of accumulation mode aerosol in the atmospheric boundary layer under cloudy and cloud-free conditions, and in the lower free troposphere under cloud-free conditions, were conducted over the rural northwest of England. Normalised size distributions in the cloud-free boundary layer (CFBL) and the cloud-free free troposphere (CFFT) exhibited almost identical spectral similarities with both size distributions possessing a concentration peak mode-radius of 0.05 μm or less. By comparison, aerosol distributions observed in cloudy air exhibited a distinctive log-normal distribution with mode-radii occurring at 0.1 μm concomitant with a local minimum at 0.05 μm. The consistent and noticeable difference in spectral features observed between cloudy and cloud-free conditions suggest that a greater amount of gas-to-particle conversion occurs on cloudy days, presumably through in-cloud aqueous phase oxidation processes, leading to larger sized accumulation mode particles. Apart from the distinct difference between cloudy and cloud-free aerosol spectra on cloudy days, aerosol concentration and mass were observed to be significantly enhanced above that of the ambient background in the vicinity of clouds. Volatility analysis during one case of cloud processing indicated an increase in the relative contribution of aerosol mass volatile at temperatures characteristic of sulphuric acid, along with a smaller fraction of more volatile material (possibly nitric acid and/or organic aerosol). Growth-law analysis of possible growth mechanisms point to aqueous phase oxidation of aerosol precursors in cloud droplets as being the only feasible mechanism capable of producing the observed growth. The effect of cloud processing is to alter the cloud condensation nuclei (CCN) supersaturation spectrum in a manner which increases the availability of CCN at lower cloud supersaturations.

 

A dedicated study of new particle formation and fate in the coastal environment (PARFORCE) Overview of objectives and initial achievements A dedicated study of new particle formation and fate in the coastal environment (PARFORCE) Overview of objectives and initial achievements

Date added: 07/31/2002
Date modified: 07/27/2009
Filesize: 448.25 kB
C. D. O'Dowd, K. Hämeri, J.M. Mäkelä, M. Kulmala, L. Pirjola, H. Berresheim, S.G. Jennings, H-C Hansson, G. de Leeuw, A.G. Allen, C.N. Hewitt, A. Stroh, and Y. Viisanen. A dedicated study of new particle formation and fate in the coastal environment (PARFORCE): Overview of objectives and initial achievements. J. Geophys. Res. 107, 10.1029/2001000555, 2002.

Abstract


A dedicated study into the formation of new particles, New Particle Formation and Fate in the Coastal Environment (PARFORCE), was conducted over a period from 1998 to 1999 at the Mace Head Atmospheric Research Station on the western coast of Ireland. Continuous measurements of new particle formation were taken over the 2-year period while two intensive field campaigns were also conducted, one in September 1998 and the other in June 1999. New particle events were observed on ∼90% of days and occurred throughout the year and in all air mass types. These events lasted for, typically, a few hours, with some events lasting more than 8 hours, and occurred during daylight hours coinciding with the occurrence of low tide and exposed shorelines. During these events, peak aerosol concentrations often exceeded 106 cm−3 under clean air conditions, while measured formation rates of detectable particle sizes (i.e., d > 3 nm) were of the order of 104–105 cm−3 s−1. Nucleation rates of new particles were estimated to be, at least, of the order of 105–106 cm−3 s−1 and occurred for sulphuric acid concentrations above 2 × 106 molecules cm−3; however, no correlation existed between peak sulphuric acid concentrations, low tide occurrence, or nucleation events. Ternary nucleation theory of the H2SO4-H2O-NH3 system predicts that nucleation rates far in excess of 106 cm−3 s−1 can readily occur for the given sulphuric acid concentrations; however, aerosol growth modeling studies predict that there is insufficient sulphuric acid to grow new particles (of ∼1 nm in size) into detectable sizes of 3 nm. Hygroscopic growth factor analysis of recently formed 8-nm particles illustrate that these particles must comprise some species significantly less soluble than sulphate aerosol. The nucleation-mode hygroscopic data, combined with the lack of detectable VOC emissions from coastal biota, the strong emission of biogenic halocarbon species, and the fingerprinting of iodine in recently formed (7 nm) particles suggest that the most likely species resulting in the growth of new particles to detectable sizes is an iodine oxide as suggested by previous laboratory experiments. It remains an open question whether nucleation is driven by self nucleation of iodine species, a halocarbon derivative, or whether first, stable clusters are formed through ternary nucleation of sulphuric acid, ammonia, and water vapor, followed by condensation growth into detectable sizes by condensation of iodine species. Airborne measurements confirm that nucleation occurs all along the coastline and that the coastal biogenic aerosol plume can extend many hundreds of kilometers away from the source. During the evolution of the coastal plume, particle growth is observed up to radiatively active sizes of 100 nm. Modeling studies of the yield of cloud-condensation nuclei suggest that the cloud condensation nuclei population can increase by ∼100%. Given that the production of new particles from coastal biogenic sources occurs at least all along the western coast of Europe, and possibly many other coastlines, it is suggested that coastal aerosols contribute significantly to the natural background aerosol population.

Quasi-Lagrangian investigation into dimethyl sulfide oxidation in maritime air using a combinat Quasi-Lagrangian investigation into dimethyl sulfide oxidation in maritime air using a combinat

Date added: 08/06/2000
Date modified: 07/23/2009
Filesize: 1.6 MB

James, J. D. ; Harrison, Roy M. ; Savage, N. H. ; Allen, A. G. ; Grenfell, J. L. ; Allan, B. J. ; Plane, J. M. C. ; Hewitt, C. N. ; Davison, B. ; Robertson, L.  2000, Quasi-Lagrangian investigation into dimethyl sulfide oxidation in maritime air using a combination of measurements and model, J. Geophys. Res. Vol. 105 , No. D21 , p. 26,379 (2000JD900375)


Abstract


Using a combination of field measurement data and a modified photochemical box model, strong evidence is presented to suggest that the rate of daytime oxidation of dimethyl sulfide (DMS) by OH radicals is insufficient to describe the measured conversion. Quasi-Lagrangian measurements were made at two sites in the eastern Atlantic (Research Vessel and Mace Head Research Station, Ireland) as part of the Atmospheric Chemistry Studies in the Oceanic Environment (ACSOE) program. Periods of connected flow between the two sites were identified, air parcel transit times were estimated, and measurements of the main DMS oxidation products (MSA, SO2, and nss-SO42-) were compared with model predictions to establish whether the model's chemical mechanism could account for observed changes. The main finding was that during daytime periods with maritime air masses, the model failed to predict a sufficient increase in DMS oxidation products during the estimated transit time. This was despite a tendency to overprediction of the progress of nitrogen chemistry during air mass advection, and independent checks on the model estimates of hydroxyl radical concentrations through measurements. In the light of this, the involvement of halogen species (most probably halogen oxides) or heterogeneous oxidation processes is tentatively suggested as the cause of enhanced daytime DMS oxidation in the marine boundary layer (MBL). Increasing the rate constant for the OH + DMS reaction by a factor of 3.3 (as a crude way of simulating parallel channels of DMS oxidation) permitted model results to reproduce the measurements very much more closely.

 

PRODUCTION OF METHANOL, ACETONE AND. ACETALDEHYDE DURING LONG-RANGE. TRANSPORT PRODUCTION OF METHANOL, ACETONE AND. ACETALDEHYDE DURING LONG-RANGE. TRANSPORT

Date added: 08/07/2003
Date modified: 08/07/2008
Filesize: 32.63 kB
Stanton, J.C.; Pilling, M.J.; Hopkins, J.R.; Lewis, A.C.Production of methanol, acetone and acetaldehyde during long-range transport [EGU04-A-07457].

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

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

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


  

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

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

Relationship between visible extinction absorption and mass concentration of carbonaceous smokes Relationship between visible extinction absorption and mass concentration of carbonaceous smokes

Date added: 07/31/1980
Date modified: 07/22/2009
Filesize: 1.99 MB

Jennings, S.G., and Pinnick, R.G. (1980)- Relationships between visible extinction, absorption and mass concentration of carbonaceous smokes. Atmos. Environ., 14, 1123-1129.


Abstract


A linear relation, independent of the size distribution, between visible and near-i.r. extinction coefficient σe(m−1) and mass concentration M (gm−3) of carbonaceous smokes is predicted. For a wavelength λ = 0.55μm the relation is σe/M = 9.5m2g−1, assuming a particle density of 2gcm−3. The relation is in good agreement with measurements on coal-fired stack plumes, oil smoke, soot and diesel exhaust that are available in the literature. A similar relationship between carbonaceous smoke visible and near-i.r. absorption coefficient σa, and mass concentration is also derived. The relations suggest that integrated mass concentration along a path within a carbonaceous smoke cloud can be inferred from measurement of the transmission from one end of the path to the other, and that the mass concentration at a particular location in the cloud can be determined from an in situ measurement of aerosol absorption at that location with a visible or near-i.r. laser spectrophone.

Mass Measurements Of Aerosol at macehead on the west coast of Ireland Mass Measurements Of Aerosol at macehead on the west coast of Ireland

Date added: 07/31/1994
Date modified: 07/24/2009
Filesize: 1.91 MB

McGovern F.M., Krasenbrink, A., Jennings, S.G., Georgi, B., Spain, T.G., Below, M., and O'Connor , T.C. (1994) Mass measurements of aerosol at Mace Head on the west coast of Ireland. Atmos. Environ, 28, 1311 -1318.


Abstract


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

Advance, 12 the growth of snowflakes and hail Advance, 12 the growth of snowflakes and hail

Date added: 06/01/1972
Date modified: 08/01/2008
Filesize: 330.33 kB

Intercomparison of formaldehyde measurements in clean and polluted atmospheres Intercomparison of formaldehyde measurements in clean and polluted atmospheres

Date added: 08/06/2000
Date modified: 07/24/2009
Filesize: 222.47 kB

Cardenas, L.M., Brassington, D.J., Allan, B.J., Coe, H., Alicke, B., Platt, U., Wilson, K.M., Plane, J.M.C. and Penkett, S.A., 2000. Intercomparison of formaldehyde measurements in clean and polluted atmospheres. Journal of Atmospheric Chemistry 37, pp. 53–80.


Abstract


Three different techniques used tomeasure atmospheric formaldehyde were compared duringa field campaign carried out at a clean maritime siteon the West coast of Ireland. Two spectroscopictechniques Differential Optical AbsorptionSpectroscopy (DOAS) and Tunable Diode Laser AbsorptionSpectroscopy (TDLAS), together with a glass coil/Hantzschreaction/fluorescence technique, wereemployed for measurements of atmospheric formaldehydeof the order of a few hundred pptv. The betteragreement was observed between the fluorescence andDOAS instruments.Two DOAS instruments were compared to the glasscoil/Hantzsch reaction/fluorescence technique at asemi-polluted site on the North Norfolk coast, U.K.,where concentrations of formaldehyde were observed atlevels up to 4 ppbv. A very good agreement wasobserved between the two instruments.The glass coil/Hantzsch reaction/fluorescence and theTDLAS instruments were also deployed simultaneously inorder to measure indoor air inside a mobile laboratorylocated at the Imperial College Silwood Park site nearAscot, U.K. The doors of the mobile laboratory wereleft open in order to obtain the backgroundformaldehyde concentrations. Closing them afterwardsallowed us to observe the increase in concentrationsas a result of indoor emissions. The agreement betweenthe two instruments was outstanding (correlationcoefficient was 99%).The results from this study showed that of the fourinstruments included in this intercomparison the glasscoil/Hantzsch reaction/fluorescence technique provedthe most suitable for continuous measurements offormaldehyde in the background atmosphere.

Segregation and Interpretation of Ozone and Carbon Monoxide Measurements by Air Mass Origin at Segregation and Interpretation of Ozone and Carbon Monoxide Measurements by Air Mass Origin at

Date added: 08/07/1997
Date modified: 07/23/2009
Filesize: 252.17 kB

Simmonds, PG, Seuring, S, Nickless, G, et al , Segregation and interpretation of ozone and carbon monoxide measurements by air mass origin at the TOR Station Mace Head, Ireland from 1987 to 1995, J ATMOS CHEM, 1997, Vol: 28, Pages: 45 - 59, ISSN: 0167-7764


Abstract


Three independent methods have been used to sort the ozone, carbon monoxide, and other radiatively important trace gases measured at Mace Head, Ireland, and thereby distinguish clean air masses transported over the North Atlantic from the more polluted air masses which have recently travelled from the European continent. Over the period April 1987-June 1995 the Northern Hemisphere surface ozone baseline concentrations exhibited a mean concentration of 34.8 ppb, with a small positive trend (+0.19 ppb yr-1), while the corresponding trend in air originating from the polluted European areas was negative (-0.39 ppb yr-1). Carbon monoxide measurements from March 1990 to December 1994 showed negative trends for both the unpolluted (-0.17 ppb yr-1) and polluted data (-13.6 ppb yr-1). Overall the continent of Europe was shown to be a small net sink of 2.6 ppb for all occasions when European air was transported to the North Atlantic.

 

CCN measurements at Mace Head, on the West Coast of Ireland CCN measurements at Mace Head, on the West Coast of Ireland

Date added: 08/07/1998
Date modified: 07/27/2009
Filesize: 60.19 kB

G. Mc Sweeney, S.G. Jennings, M. Geever, CCN measurements at Mace Head, on the West Coast of Ireland, Journal of Aerosol Science, Volume 29, Supplement 1, Proceedings of the 1998 International Aerosol Conference Part 1, September 1998, Page S199, ISSN 0021-8502, DOI: 10.1016/S0021-8502(98)00297-3.


Abstract

Particle deposition in ventilation duct onto three-dimensional roughness elements Particle deposition in ventilation duct onto three-dimensional roughness elements

Date added: 08/01/2002
Date modified: 07/03/2009
Filesize: 133.69 kB
A.C.K. Lai, M.A. Byrne, A.J.H. Goddard, Particle deposition in ventilation duct onto three-dimensional roughness elements, Building and Environment, 37, No .10, 939-945, 2002.

Abstract


Gaining insights on particle deposition onto ventilation duct has many important applications. One key pathway by which outdoor polluted air enters the indoor environment is through mechanical ventilation ducts. An experimental system was designed for the study of particle deposition on regular arrays of uniform elements (in the form of discrete protrusions) in a turbulent ventilation duct flow using monodisperse tracer small particles, in the range 0.7–7.1 μm. The Reynolds number for the test conditions was 44,000 in the 150 mm square duct. Four different types of uniform roughness elements were tested. Compared to earlier measurements in the same duct system involving smooth or ribbed surfaces, a significant increase (up to 74 times) in deposition velocity onto the regular roughness elements is observed.

Analysis of PM2.5 particulate mass concentrations during 1999 at Mace Head Analysis of PM2.5 particulate mass concentrations during 1999 at Mace Head

Date added: 08/07/2000
Date modified: 07/27/2009
Filesize: 148.23 kB

Kleefeld S.; Jennings S.G., Analysis of PM2.5 particulate mass concentrations during 1999 at Mace Head, Journal of Aerosol Science, Volume 31, Supplement 1, September 2000 , pp. 731-732(2)


Abstract


In recent years, the quality of air we breathe has become a significant factor in the environment, with ncreasing interest in the properties of both indoor and outdoor air. Ambient air particles, in addition to gaseous species, are important components in the assessment of air quality, since there is increasing evidence for an association between adverse health effects and the levels of particulate air pollution. Especially the finer particle fraction PMz.5 (particulate mass concemrations with a 50% cut-off diameter of 2.5 pro) is able to penetrate deep into the respiratory system of humans and is best correlated with acute mortality and morbidity findings in urban areas (Oberd6rster et al., 1995). Few measurements of PM2.5 mass concentrations exist for urban areas (e.g. Chan et al., 1999, Chow et al., 1996), but no information is available so far for clean marine air concentrations in the North Atlantic region. Information on background concentrations of PM2.~ mass concentrations as well as on their sources is essential in the interpretation of urban particulate air pollution. Within this study PMz.~ mass concentrations are presented for a clean air site at the Atmospheric Research Station at Mace Head, Cama, (53019 ' N, 9054 ' W) on the west coast of Ireland for the year 1999, and a source identification is performed.

Intercomparison of elemental concentrations in total and size-fractionated aerosol samples coll Intercomparison of elemental concentrations in total and size-fractionated aerosol samples coll

Date added: 08/07/1995
Date modified: 07/24/2009
Filesize: 1.12 MB

Francois F., Maenhaut W., Colin J.L., Losno R., Schulz M., Stahlschmidt T., Spokes L.,
Jickells T., Intercomparison of Elemental Concentrations in Total and Size-Fractionated
Aerosol Samples Collected During the Mace Head Experiment, April 1991, Atmos. Environ.
29, 1995, 837-849.


Abstract


During an intercomparison field experiment, organized at the Atlantic coast station of Mace Head, Ireland, in April 1991, aerosol samples were collected by four research groups. A variety of samplers was used, combining both high- and low-volume devices, with different types of collection substrates: Hi-Vol Whatman 41 filter holders, single Nuclepore filters and stacked filter units, as well as PIXE cascade impactors. The samples were analyzed by each participating group, using in-house analytical techniques and procedures. The intercomparison of the daily concentrations for 15 elements, measured by two or more participants, revealed a good agreement for the low-volume samplers for the majority of the elements, but also indicated some specific analytical problems, owing to the very low concentrations of the non-sea-salt elements at the sampling site. With the Hi-Vol Whatman 41 filter sampler, on the other hand, much higher results were obtained in particular for the sea-salt and crustal elements. The discrepancy was dependent upon the wind speed and was attributed to a higher collection efficiency of the Hi-Vol sampler for the very coarse particles, as compared to the low-volume devices under high wind speed conditions. The elemental mass size distribution, as derived from parallel cascade impactor samplings by two groups, showed discrepancies in the submicrometer aerosol fraction, which were tentatively attributed to differences in stage cut-off diameters and/or to bounce-off or splintering effects on the quartz impactor slides used by one of the groups. However, the atmospheric concentrations (sums over all stages) were rather similar in the parallel impactor samples and were only slightly lower than those derived from stacked filter unit samples taken in parallel.

 

Increased rates of rainfall production in Electrified clouds Increased rates of rainfall production in Electrified clouds

Date added: 07/30/1973
Date modified: 07/22/2009
Filesize: 822.23 kB

Brazier-Smith, P.R., Jennings, S.G., and Latham, J. (1973)- Increasing rates of rainfall production in electrified clouds. Quart. J. Roy. Met. Soc., 99, 776-779


Abstract

An analysis of rapid increases in condensation nuclei concentrations at a remote coastal site i An analysis of rapid increases in condensation nuclei concentrations at a remote coastal site i

Date added: 08/06/1999
Date modified: 07/27/2009
Filesize: 885.01 kB

Grenfell, J.L., R.M. Harrison, A.G. Allen, J.P. Shi, S.A. Penkett, C.D. O'Dowd, M.H. Smith, M.K. Hill, L. Robertson, C.N. Hewitt, B. Davison, A.C. Lewis, D.J. Creasey, D.E. Heard, K. Hebestreit, B. Alicke and J. James, An analysis of rapid increases in condensation nuclei concentrations at a remote site on the West Irish Coast, J. Geophys.Res., 104, 13,771-13,780, 1999, (Ser. No. ACP073).


Abstract


Massive bursts in condensation nuclei (CN) concentration were recorded at a remote site on the west Irish coast during campaigns in summer 1996 and spring/summer 1997. Number concentrations of 3-7 nm diameter CN were observed to rise daily from 102-103 up to ∼105 /cm3 for 1-3 hours. Data were collected as part of the Atmospheric Chemistry Studies in the Oceanic Environment program. In a previous paper the burst phenomenon was linked to the movement of the tide, and it was suggested that enhanced biogenic emissions occurred near low tide with concomitant rapid homogeneous gas phase CN formation. In this paper possible chemical mechanisms for the burst phenomenon are investigated. Two approaches are adopted. First, by assuming a 20:80 sulfate:water molar composition and calculating the number distribution using data from condensation particle counters, the total mass of CN formed during a burst is evaluated. This is compared with that mass of sulfate produced by OH-initiated dimethyl sulfide (DMS) oxidation. The procedure is termed mass balance. Second, a variety of chemical species are coplotted with tidal height. DMS oxidation is not believed to play a major role in CN formation at this site because (1) the mass balance calculations imply ambient DMS concentrations higher than those observed, and (2) gas phase HCI, HNO3. SO2, and NH3 did not exhibit any discernible correlation with tidal height. Further, none of the suite of observed nonmethane hydrocarbons or DMS showed a tidal relation. No mechanism has to date been convincingly identified for the burst phenomenon.

 

Production of peroxy radicals at night via reactions of ozone and the nitrate radical in the ma Production of peroxy radicals at night via reactions of ozone and the nitrate radical in the ma

Date added: 08/06/2001
Date modified: 07/23/2009
Filesize: 1.44 MB

Salisbury, G., et al. (2001), Production of peroxy radicals at night via reactions of ozone and the nitrate radical in the marine boundary layer, J. Geophys. Res., 106(D12), 12,669–12,687.


Abstract


In this paper, a substantial set of simultaneous measurements of the sum of peroxy radicals, [HO2+RO2], NO3, hydrocarbons (HCs), and ozone, taken at Mace Head on the Atlantic coast of Ireland in spring 1997, is presented. Conditions encountered during the experiment ranged from semipolluted air masses advected from Britain and continental Europe to clean air masses off the North and mid-Atlantic, where mixing ratios of pollution tracers approached Northern Hemispheric background mixing ratios. Average mixing ratios of peroxy radicals varied from 2.5 to 5.5 parts per trillion by volume (pptv) at night depending on wind sector, and were observed to decay only very slowly from late afternoon to early morning (0.1–0.5 pptv h−1). Measurements of OH and HO2 on two nights using the Fluorescence Assay by Gas Expansion (FAGE) technique give an upper limit for [OH] of 2.5×105 molecules cm−3 and an average upper limit [HO2]/[HO2+RO2] ratio of 0.27. A modeling study of the 1/e lifetimes of the peroxy radicals, assuming no radical production at night, yielded mean lifetimes of between ∼ 8–23 min for HO2 and 3–18 min for CH3O2. Given these lifetimes, it may be concluded that the peroxy-radical mixing ratios observed could not be maintained without substantial production at night. No significant correlation is observed between measured [HO2+RO2] and [NO3] under any conditions. Calculation of the reaction rates for ozone and NO3 with hydrocarbons (HCs) shows that the ozone-initiated oxidation routes of HCs outweighed those of NO3 in the NE, SE and NW wind sectors. In the SW sector, however, the two mechanisms operated at similar rates on average, and oxidation by NO3 was the dominant route in the westerly sector. The oxidation of alkenes at night by ozone was greater by a factor of 4 than that by NO3 over the whole data set. The HC degradation rates from the three “westerly” sectors, where tracer mixing ratios were relatively low, may be representative of the nighttime oxidative capacity of the marine boundary layer throughout the background Northern Hemisphere. Further calculations using literature values for OH yields and inferred RO2 yields from the ozone-alkene reactions show that peroxy radicals derived from the ozone reactions were likely to make up the major part of the peroxy-radical signal at night (mean value 66%). However, the NO3 source was of similar magnitude in the middle of the night, when [NO3] was generally at its maximum. The estimated total rates of formation of peroxy radicals are much higher under semipolluted conditions (mean 8.0×104 molecules cm−3 s−1 in the SE wind sector) than under cleaner conditions (mean 2.4×104 molecules cm−3 s−1 in the westerly wind sector). A model study using a campaign-tailored box model (CTBM) for semipolluted conditions shows that the major primary sources of OH, HO2, and CH3O2 (the most abundant organic peroxy radical) were the Criegee biradical intermediates formed in the reactions of ozone with alkenes.

 

Aerosol generation by waves breaking on small islands and rocks near the mace head research sta Aerosol generation by waves breaking on small islands and rocks near the mace head research sta

Date added: 08/07/2000
Date modified: 07/27/2009
Filesize: 150.69 kB

Kunz, GJ, CD O'Dowd, G de Leeuw, Aerosol generation by waves breaking on small islands and rocks near the Mace Head research station. European Aerosol Conference, 2000, J. Aerosol. Sci., Suppl 1., 656-657, 2000. [36] Kleefeld, C., S O'Rielly, SG Jennings, E Becker, C O'Dowd, G Kunz and G de Leeuw, Aerosol scattering: relation to primary and secondary aerosol production in the coastal atmosphere during the PARFORCE campaign, European Aerosol Conference, 2000, J. Aerosol. Sci., Suppl 1., 658-659, 2000.


Abstract


Two coastal field experiments (September 1998 and in June 1999) were conducted at Mace Head, Ireland, under the EU-funded PARFORCE (New P__._~icle Formation and Fate in the Coastal Environment) programme which was designed to elucidate the processes which control and promote homogeneous heteromolecular nucleation in the coastal boundary layer. During conditions of westerly winds and after sufficiently long fetch, the Mace Head station is regularly exposed to pure maritime and clean arctic atmospheres. Under these conditions the generation and growth of new particles due to photochemical conversion of biological emissions is seen to occur on almost a daily basis (e.g., O'Dowd et al., 1998 and O'Dowd et al., 1999). During the PARFORCE experiments the TNO Physics and Electronics Laboratory (TNO-FEL) undertook to measure boundary layer dynamics, as determined from the aerosol structures measured with a lidar (light detection and ranging) system. The results revealed the generation of large amounts of sea spray Aerosol by waves breaking on the islands and roCks near the Mace Head station. The location, size and dynamics of these locally generated aerosol plumes were determined from series of consecutive horizontal and vertical scans. The horizontal extent of these aerosol plumes is highly coherent over distances of several kilometres and the vertical extent is generally between a few tens of meters to a few hundreds of meters. In some occasions the aerosol was observed to be taken aloft to the top of the mixed layer at an altitude of about one kilometre.

Interannual and seasonal variability in atmospheric N 2 O Interannual and seasonal variability in atmospheric N 2 O

Date added: 08/06/2007
Date modified: 07/02/2009
Filesize: 673.42 kB

Nevison, C. D., N. M. Mahowald, R. F. Weiss, and R. G. Prinn (2007), Interannual and seasonal variability in atmospheric N2O, Global Biogeochem. Cycles, 21, GB3017, doi:10.1029/2006GB002755.


Abstract


The increase in atmospheric N2O observed over the last century reflects large-scale human perturbations to the global nitrogen cycle. High-precision measurements of atmospheric N2O over the last decade reveal subtle signals of interannual variability (IAV) superimposed upon the more prominent growth trend. Anthropogenic sources drive the underlying growth in N2O, but are probably too monotonic to explain most of the observed IAV. The causes of both seasonal and interannual variability in atmospheric N2O are explored on the basis of comparisons of a 1993–2004 atmospheric transport simulation to observations of N2O at five stations of the Advanced Global Atmospheric Gases Experiment (AGAGE). The complementary tracers chlorofluorocarbons (CFCs) 11 and 12 and SF6 also are examined. The model simulation does not include a stratospheric sink and thus isolates the effects of surface sources and tropospheric transport. Both model and observations yield correlations in seasonal and interannual variability among species, but only in a few cases are model and observed variability correlated to each other. The results suggest that tropospheric transport contributes substantially to observed variability, especially at Samoa station. However, some features of observed variability are not explained by the model simulation and appear more consistent with a stratospheric influence. At Mace Head, Ireland, N2O and CFC growth rate anomalies are weakly correlated to IAV in polar winter lower stratospheric temperature, a proxy for the strength of the mean meridional stratospheric circulation. Seasonal and interannual variability in the natural sources of N2O may also contribute to observed variability in atmospheric N2O.

 

Light scattering enhancement factors in the marine boundary layer (Mace Head, Ireland) Light scattering enhancement factors in the marine boundary layer (Mace Head, Ireland)

Date added: 02/15/2011
Date modified: 02/15/2011
Filesize: 1.01 MB

Fierz-Schmidhauser, R., P. Zieger, A. Vaishya, C. Monahan, J. Bialek, C. D. O'Dowd, S. G. Jennings, U. Baltensperger, and E. Weingartner (2010), Light scattering enhancement factors in the marine boundary layer (Mace Head, Ireland), J. Geophys. Res., 115, D20204, doi:10.1029/2009JD013755.


Direct climate aerosol radiative forcing is influenced by the light scattering of atmospheric aerosols. The chemical composition, the size distribution, and the ambient relative humidity (RH) determine the amount of visible light scattered by aerosols. We measured the aerosol light scattering coefficients at RH varying from 30% to 90% of the marine atmosphere at the Mace Head Atmospheric Research Station on the west coast of Ireland. At this site, two major air mass types can be distinguished: clean marine and polluted air. In this paper, we present measurements of light scattering enhancement factors f(RH) = σsp(RH)/σsp(dry) from a 1 month field campaign (January–February 2009). At this site in winter, the mean f(RH = 85%) (standard deviation) for marine air masses at the wavelength of 550 nm was 2.22 (±0.17) and 1.77 (±0.31) for polluted air. Measured σsp(RH) and f(RH) agreed well with calculations from Mie theory using measurements of the size distribution and hygroscopic diameter growth factors as input. In addition, we investigated the RH influence on additional intensive optical properties: the backscatter fraction and the single scattering albedo. The backscatter fraction decreased by about 20%, and the single scattering albedo increased on average by 1%–5% at 85% RH compared to dry conditions.

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

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

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


Abstract

 

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

Atmospheric measurements of OH, HO2 and NO by laser-induced fluorescence spectroscopy Atmospheric measurements of OH, HO2 and NO by laser-induced fluorescence spectroscopy

Date added: 08/06/2003
Date modified: 07/27/2009
Filesize: 16.18 kB

Bloss, W. J.; Floquet, C.; Gravestock, T. J.; Heard, D. E.; Ingham, T.; Johnson, G. P.; Lee, J. D.,Atmospheric measurements of OH, HO2 and NO by laser-induced fluorescence spectroscopy using a compact all solid-state laser system,EGS - AGU - EUG Joint Assembly, Abstracts from the meeting held in Nice, France, 6 - 11 April 2003, abstract #10521


Abstract


Free-radicals are key intermediates that control the budgets of many trace gases, for example ozone, greenhouse gases and harmful pollutants. Measurement of radicals and comparison with model calculations constitutes an important test of our understanding of the underlying chemistry. There is a greater need for compact and lightweight instruments for the in situ measurement of free-radical species that are suitable for deployment from a number of field-platforms. A new field instrument has been developed that incorporates an all solid-state Nd:YAG pumped titanium sapphire laser that is capable of generating radiation at high pulse-repetition-frequency for the detection of OH, HO_2, NO and IO radicals in the atmosphere by laser induced fluorescence (LIF). The system offers advantages of wide wavelength tunability, compactness, low weight, greater long-term stability (fibre-optic delivery) and short warm-up time. The instrument was successfully deployed during 2002 in the NAMBLEX field campaign at Mace Head with detection limits for OH and HO_2 (measured simultaneously with laser operation at 308 nm) of 3.1 x 10^5 molecule cm-3 (0.012 ppt) and 2.6 x 10^6 molecule cm-3 (0.09 pptv) respectively. Diurnal profiles of OH have been recorded over a period of 5 weeks. NO controls the HO_2/OH ratio and is the critical parameter in the production of tropospheric ozone, yet measurements in the boundary layer are restricted to a single indirect technique based on chemiluminescent analysers. Measurements of NO in the atmosphere have been made by LIF using the new instrument operating at 226 nm, with absolute concentrations in good agreement with simultaneous measurements made using a commercial chemiluminescent analyser. Whilst operating at 445 nm, the instrument has detected the IO radical in the laboratory, with a projected detection limit that is well below previously measured atmospheric concentrations of IO. A second instrument to be deployed on an aircraft platform is currently being developed.

Marine biogenic and anthropogenic contributions to non-sea-salt sulfate in the marine boundary Marine biogenic and anthropogenic contributions to non-sea-salt sulfate in the marine boundary

Date added: 08/06/2002
Date modified: 07/24/2009
Filesize: 376.92 kB

Savoie, D. L., R. Arimoto, W. C. Keene, J. M. Prospero, R. A. Duce, and J. N. Galloway (2002), Marine biogenic and anthropogenic contributions to non-sea-salt sulfate in the marine boundary layer over the North Atlantic Ocean, J. Geophys. Res., 107(D18), 4356, doi:10.1029/2001JD000970.


Abstract


As a part of the Atmosphere/Ocean Chemistry Experiment (AEROCE), daily aerosol samples were collected in the marine boundary layer at Barbados, West Indies (13.17°N, 59.43°W), Bermuda (32.27°N, 64.87°W), and Mace Head, Ireland (53.32°N, 9.85°W), and in the free troposphere at Izaña, Tenerife, Canary Islands (28.30°N, 16.48°W; 2360 m asl). In this report, we use multiple variable regression analyses with methanesulfonate (MSA) and Sb and/or NO3 as the independent variables to assess the relative contributions of the marine biogenic and anthropogenic sources to the total non-sea-salt (nss) SO42− concentrations at the AEROCE sites. On the basis of 2 years of data at Bermuda and Barbados, the marine nss SO42−/MSA mass ratios (19.6 ± 2.1 and 18.8 ± 2.2) were consistent throughout the year and comparable to those at American Samoa in the tropical South Pacific (18.1 ± 0.9). At Mace Head (based on 1 year of data), this ratio was about 3.01 (±0.53). An analysis of the residuals and an assessment of the root mean square deviations indicate that the ratio at Mace Head can also be reasonably applied throughout the year. However, there is enough uncertainty during the winter that we cannot rule out a significant increase (to about 20) during periods with low concentrations of both MSA and NO3. The results from 4 years indicate that the marine contribution is too low to permit a reasonable assessment of the biogenic nss SO42−/MSA ratio at Izaña. The continental nss SO42−/Sb mass ratio varies significantly from one location to another. At Bermuda, where North American sources are expected to dominate, the ratio is about 29,000, about a factor of 2 higher than the average of 13,500 at Mace Head where European sources dominate. Intermediate values occurred at Barbados (18,000) and Izaña (24,000) where both European and North African sources are significant. Estimates based on these ratios indicate that, on an annual basis, the contributions from anthropogenic sources account for about 50% of the total nss SO42− in aerosols at Barbados, 70% at Bermuda, 85–90% at Mace Head, and about 90% at Izaña. If the same biogenic nss SO42−/MSA ratios are applicable to rainwater, then the relative contributions in precipitation at Barbados and Bermuda are comparable to those in aerosols.

 

Diurnal cycles of short-lived tropospheric alkenes at a north Atlantic coastal site Diurnal cycles of short-lived tropospheric alkenes at a north Atlantic coastal site

Date added: 08/07/1999
Date modified: 07/27/2009
Filesize: 210.82 kB

A.C. Lewis J.B. McQuaid, N. Carslaw, M.J. Pilling.,; Short Communication Diurnal cycles of short-lived tropospheric alkenes at a north Atlantic coastal site,. Atmospheric Environment 33 (1999) 2417Ð2422 2419


Abstract


Observation of diurnal cycles in atmospheric concentrations of reactive alkenes are reported from measurements performed at a North Atlantic coastal site (Mace Head, Eire 53°19'34N; 9°54'14W). Species seen to exhibit distinct cycles included isoprene, ethene, propene, 1-butene, iso-butene and a substituted C6 alkene. Five hundred and thirty air mass classified measurements were performed over a 4 week period at approximately hourly frequency and demonstrate that during periods when air flow resulted from unpolluted oceanic regions a clear daily cycle in concentrations existed, peaking at around solar noon for all species. These observations support the proposed mechanism of production via photochemical degradation of organic carbon in sea water. The observed concentrations showed strong correlation (propene R2 > 0.75) with solar flux, with little relationship to other meteorological or chemical parameters. The species' short atmospheric lifetimes indicate that the source of emission was from local coastal waters within close proximity of the sampling site. At solar noon concentrations of reactive alkenes from oceanic sources were responsible for up to 88% of non-methane hydrocarbon reaction with the hydroxyl radical at this coastal marine site.

 

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

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

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


 

Abstract

 

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

 

Effects of particulate complex refractive index and particle size distribution variations on atmospheric extinction Effects of particulate complex refractive index and particle size distribution variations on atmospheric extinction

Date added: 08/01/1978
Date modified: 07/01/2009
Filesize: 851.05 kB
Jennings, S.G., and Pinnick, R.G.  (1978)- Effects of particulate refractive index and particle size distribution variations on atmospheric extinction and absorption for visible to middle-IR wavelengths. American Meteorological Society Third Conference on Atmospheric Radiation, Davis, California, 6-9.

Abstract


A comprehensive sensitivity study has been made, using Mie theory, to determine the effect of realistic variations in values of real and imaginary parts of the complex index of refraction on volume extinction and absorption coefficients for a wide range of lognormal particle size distributions (defined by geometric mean radius r sub g and geometric standard deviation sigma sub g). Wavelengths lambda from visible (0.55 micrometers) through middle-infrared (10.6 micrometers) were considered. Extinction is independent of complex index to within 20 percent for the majority of realistic particle size distributions, providing lambda < or = 2 micrometers. However, changes in extinction by up to an order of magnitude are caused by realistic variations in refractive indexes for 2 < or = lambda < or = 10.6 micrometers, with real index being more important in affecting extinction than imaginary index.

Comparisons of aerosol nitrogen isotopic composition at two polluted coastal sites Comparisons of aerosol nitrogen isotopic composition at two polluted coastal sites

Date added: 08/06/2001
Date modified: 07/23/2009
Filesize: 281.41 kB

Yeatman, S.G. L.J. Spokes, P.F. Dennis and T.D. Jickells, Comparison of aerosol nitrogen isotope composition at two coastal sites, Atmos. Environ. 35, 1307-1320, 2001, (Ser. No. ACP125).


Abstract


Atmospheric fixed-nitrogen deposition can contribute to eutrophication in coastal and estuarine waters. Stable nitrogen isotope data can provide important information regarding the sources and processing of atmospheric fixed-nitrogen species and is thus important in controlling eutrophication. Size-segregated aerosol samples were collected from two coastal sites: Weybourne, England and Mace Head, Ireland and also aboard the RRS Challenger in the Eastern Atlantic Ocean. Aerosol concentrations of ammonium and nitrate were determined prior to δ15N isotopic analysis. For both species a significant difference in mean isotopic composition was seen between samples from Weybourne (+6±6‰ for ammonium and +7±6‰ for nitrate) and Mace Head and RRS Challenger campaigns (-9±8‰ for ammonium and -1±3‰ for nitrate). At each site a strong dependence of isotopic composition on the geographical origin of the sampled air mass was also observed. For aerosol ammonium, marine and terrestrially dominated samples were found to be isotopically distinct, perhaps reflecting the presence of oceanic sources of ammonia in addition to anthropogenic or natural terrestrial sources. Further distinctions were made within terrestrially dominated samples, possibly indicative of different types of animal husbandry regimes or other forms of anthropogenic activity. For aerosol nitrate, there was found to be generally less variation between samples at each site, although at Weybourne a significant difference was observed between the mean isotopic composition of samples originating from the northern UK (+15±3‰) and that of those originating from the southern UK (+10±3‰), suggesting that aerosol δ15N data might possibly facilitate source apportionment between NOx emissions from power stations and those from vehicle exhausts. The nitrate data also appeared to show seasonality with higher concentrations and lower δ15N values seen in the summer.

 

Isentropic airflow probability analysis Isentropic airflow probability analysis

Date added: 08/06/1994
Date modified: 07/24/2009
Filesize: 1.32 MB

Merrill, J. T. (1994), Isentropic airflow probability analysis, J. Geophys. Res., 99(D12), 25,881–25,889.


Abstract

 

Trajectory analysis has been used to identify possible sources in both short-and long-range atmospheric transport. Here the focus is on the climatological pathway of airflow to the Atmosphere/Ocean Chemistry Experiment sites, determined by superposition of ensembles of isentropic trajectories. The trajectories are prepared from wind fields on surfaces of constant potential temperature interpolated from the National Meteorological Center global analysis, calculated twice daily for each site for the period from 1986 to 1993. At Bermuda there is a notable seasonal variation, with the months of May–November dominated by flow around the subtropical anticyclone, while flow from the northwest and west is more common in the cooler months of December–April. Flow from the west predominates at Mace Head, Ireland, in the months from April–September, while flow from the east (over Great Britain and western Europe) is of increased importance during October–March. At Izaña the flow is most commonly from the west; flow from the east, over Africa and southern Europe, is most common during the months of July–September. The winds at Barbados, West Indies, are much steadier than at the other sites, and there is little seasonal variation in the general pattern of flow. The circulation during precipitation events, evaluated as the airflow weighted by rainfall amount, showed a striking difference from the general pattern of airflow at Mace Head, especially during October–March: in the absence of rain the winds are much more common from the east, over polluted continental areas, than during rain events, when the dominance of flow from the west is greater.

 

Marine organohalogens in the atmosphere over the Atlantic and Southern Oceans Marine organohalogens in the atmosphere over the Atlantic and Southern Oceans

Date added: 08/06/2003
Date modified: 07/24/2009
Filesize: 564.21 kB

Carpenter, L. J., P. S. Liss, and S. A. Penkett (2003), Marine organohalogens in the atmosphere over the Atlantic and Southern Oceans, J. Geophys. Res., 108(D9), 4256, doi:10.1029/2002JD002769.


Abstract


Reactive halogen species (RHS) such as the halogen oxide radicals IO and BrO influence tropospheric oxidation processes in both polar and temperate regions. Oceanic photolabile halocarbons have been shown to be strong sources of RHS in midlatitudes. However, the global source strengths of these halocarbon precursors and the relative importance of the coastal and pelagic oceans on their concentrations are highly uncertain. Here we present atmospheric measurements of the reactive organic halogens CH3I, CH2I2, CH2ClI, CH2IBr, CHIBr2, CHBr3, CH2Br2, and CHBr2Cl made at Mace Head, Ireland, during the Particle Formation and Fate in the Coastal Environment campaign in September 1998 and at Cape Grim, Tasmania, during the Southern Ocean Atmospheric Photochemistry Experiment 2 campaign in January/February 1999. Mace Head is strongly influenced by local macroalgae, whereas Cape Grim, owing to its cliff-top location, suffers much less impact from seaweeds. The very reactive halocarbons CH2I2, CH2IBr, and CHIBr2 observed at Mace Head were below detection limits at Cape Grim, although CH2ClI was detected at both locations. Mixing ratios of CH3I, CH2ClI, CHBr3, CHBr2Cl, and CH2Br2 at Cape Grim were on average 25–50% of those at Mace Head. Concentrations of the polybromomethanes correlated well at both sites. Using these correlations, we estimate molar source strengths of CHBr2Cl and CH2Br2 to be between 3 and 6% and between 15 and 25% of the global CHBr3 flux, respectively. These values fall within ranges estimated independently from concentration and lifetime data.

 

Atmospheric CO2 concentration variations recorded at Mace Head, Ireland, from 1992 to 1994 Atmospheric CO2 concentration variations recorded at Mace Head, Ireland, from 1992 to 1994

Date added: 07/31/1997
Date modified: 07/27/2009
Filesize: 491.17 kB

Bousquet, P., Gaudry. A., Ciais, P., Kazan, V., Monfray, P., Simmonds, P.G., Jennings, S.G., and O'Connor, T.C. (1997). Atmospheric CO2 concentration variations recorded at Mace Head, Ireland from 1992 to 1994. Phys. Chem. Earth, 21, 447-481.


Abstract


Atmospheric CO 2 has been monitored continuously at the Irish station of Mace-Head (MHD) since July 1992. The mean rate of increase is 1.85 ppmv yr -t with a peak-to-peak amplitude of 15.1+1.1 ppmv. The record also shows important short-term variations from the smoothed curve due to both European and oceanic influences and amplified by day/night local effects. Two different baseline conditions are defined in order to remove local perturbations. Restricted Baseline Conditions (RBC) keep data only representing atmospheric background conditions from the West. Extended Baseline Conditions (EBC) add stable air masses coming from all angular sectors to RBC selection. The contrast between western and eastern air masses coming respectively from North-Atlantic ocean and Europe is studied. For air masses arriving from the West, a systematic depletion in 1992-93 is found relative to all surrounding stations within the North- Atlantic basin. The partition of this depletion between European biospheric uptake and the North-Atlantic ocean cannot be performed as long as other tracers are not sampled regularly, or during intensive campaigns at Mace Head (13C/12C, Radon-222 and O2/N2). In contrast, Eastern air masses present strong positive anomalies in CO2 that reflect European sources.

Comparison of long-term trends and seasonal variations of atmospheric mercury concentrations at Comparison of long-term trends and seasonal variations of atmospheric mercury concentrations at

Date added: 08/07/2005
Date modified: 07/27/2009
Filesize: 449.95 kB

Kock, H.H.;  Bieber, E.; Ebinghaus, R.; Spain, T.G.; Thees, B. (2005): Comparison of long-term trends and seasonal variations of atmospheric mercury concentrations at the two European coastal monitoring stations Mace Head, Ireland, and Zingst, Germany. In: Atmospheric Environment . Vol. 39 (2005) 39, 7549 - 7556


Abstract

 

Monitoring of total gaseous mercury (TGM) concentrations has been carried out at Mace Head on the west coast of Ireland and at Zingst on the southern shore-line of the Baltic Sea. We have used the continuous measurements to assess long-term trends and seasonal variations of TGM concentrations over the same time period. Between 1998 and 2004 the annually averaged TGM concentrations measured at Mace Head (1.72 ng m-3) and Zingst (1.66 ng m-3) remained fairly stable. At both stations we measured higher TGM levels during winter months and lower concentrations during summer months. We also observed an unexpected West to East gradient and found that the overall mean Mace Head TGM concentration was 0.06 ng m-3 higher than those of Zingst. For the January to June period, the Mace Head TGM values (6-year mean = 1.75 ng m-3) are significantly elevated compared to the Zingst results (6-year mean-1.64 ng m-3). Since no local anthropogenic mercury sources exist near the Mace Head station, enhanced emission from the sea appears to provide the most probable explanation for the observed differences. Multiple regression analysis with the atmospheric mercury concentrations measured at Zingst were made with selected meteorological and air quality parameters (wind component, dew point, dust and NOx concentrations). The short-term variation in the TGM concentrations at Zingst shows a strong positive correlation with weather conditions and selected air quality parameters, making TGM a usable tracer of air masses originating from different source regions.

 

Relation between absorption coefficient and imaginary index of atmospheric aerosol constituents Relation between absorption coefficient and imaginary index of atmospheric aerosol constituents

Date added: 07/31/1979
Date modified: 07/06/2009
Filesize: 512.02 kB
Jennings, S.G., Pinnick, R.G., and Gillespie, J.B. (1979)- Relation between absorption coefficient and imaginary index of atmospheric aerosol constituents. Appl. Opt., 18, 1368-1371.

Abstract


The absorption coefficient per unit mass α(cm2g-l) for aerosols in the wavelength range λ = 1.06–10.6 µm is shown to be a sensitive function of particle size distribution and of both imaginary and real indexes of refraction. Hence the imaginary index of refraction cannot be accurately determined from absorption measurements on an aerosol sample as attempted by S. A. Schleusener et al., Appl. Opt. 15, 2546 (1976), unless the size distribution and real index of the aerosol material are known. Similar difficulties arise in attempts to infer imaginary index from transmission measurements through aerosol samples as done by F. E. Volz, Appl. Opt. 11, 755 (1972); 12, 564 (1973) and K. Fischer, Beitr. Phys. Atmos. 43, 244 (1970). In addition, scattering losses can further complicate the determination of imaginary index from transmission measurements.

Atmospheric histories of halocarbons from analysis of Antarctic firn air Major Montreal Protocol species Atmospheric histories of halocarbons from analysis of Antarctic firn air Major Montreal Protocol species

Date added: 08/01/2002
Date modified: 06/30/2009
Filesize: 832.27 kB
Sturrock, G. A., D. M. Etheridge, C. M. Trudinger, P. J. Fraser, and A. M. Smith (2002), Atmospheric histories of halocarbons from analysis of Antarctic firn air: Major Montreal Protocol species, J. Geophys. Res., 107(D24), 4765, doi:10.1029/2002JD002548.
Abstract

 

Air samples extracted from Antarctic firn at Law Dome have been analyzed for the suite of halocarbons that contribute most of the anthropogenic chlorine and about half the anthropogenic bromine presently released into the stratosphere. The species, all included in the Montreal Protocol, are the chlorofluorocarbons (CFCs -11, -12, -113, -114, -115), hydrochlorofluorocarbons (HCFCs -22, -141b, -142b), halons (H -1211, -1301), CH3CCl3 (methyl chloroform) and CCl4 (carbon tetrachloride). The measurements were used to reconstruct the atmospheric history of these species since the 1930s, providing a record considerably predating existing in situ records or other conventional air archives, encompassing virtually the entire history of anthropogenic emissions of CFCs, HCFCs, and halons and giving early 20th century levels for CH3CCl3 and CCl4. Significant features of this study are (1) the narrow age spread (spectral width 5 years) of the individual firn air samples, which reveals rapid atmospheric changes, (2) the use of inversion techniques to infer past atmospheric composition with associated uncertainties, and (3) the low analytical detection limit (<0.1 ppt), which, together with the narrow air age spread, detects early background levels and resolves the time that industrial emissions first appeared in the southern hemisphere atmosphere. Integrity of the data is demonstrated by successful intercomparison of data from independent firn sites on Law Dome with common time-series. An upper limit is given for the potential contribution to atmospheric levels of CH3CCl3 from nonindustrial sources. The atmospheric records produced from firn air are compared to calculations based on the history of their global emissions.

On the photochemical production of biogenic new particles in the coastal boundary layer On the photochemical production of biogenic new particles in the coastal boundary layer

Date added: 08/05/1999
Date modified: 08/05/2008
Filesize: 4.86 MB
O'Dowd, C.D., G. McFiggans, D.J. Creasey, L. Pirjola, C. Hoell, M.H. Smith, B.J. Allan, J.M.C. Plane, D.E. Heard, J.D. Lee, M.J. Pilling, and M. Kulmala, On the photochemical production of biogenic new particles in the coastal boundary layer, Geophys. Res. Lett., 26, 1707-1710, 1999, (Ser. No. ACP072).

On the formation, growth and composition of nucleation mode particles On the formation, growth and composition of nucleation mode particles

Date added: 08/06/2001
Date modified: 07/03/2009
Filesize: 428.69 kB

Kulmala, M.,M. Dal Maso, J.M. Mäkelä, L. Pirjola, M. Väkevä, P. Aalto, P. Miikkulainen, K. Hämeri and C.D. O'Dowd, On the Formation, growth and composition of nucleation mode particles, Tellus B, 53, 479-490,, 2001


Abstract


Taking advantage of only the measured aerosol particles spectral evolution as a function of time, a new analytical tool is developed to derive formation and growth properties of nucleation mode aerosols. This method, when used with hygroscopic growth‐factors, can also estimate basic composition properties of these recently‐formed particles. From size spectra the diameter growth‐rate can be obtained, and aerosol condensation and coagulation sinks can be calculated. Using this growth‐rate and condensation sink, the concentration of condensable vapours and their source rate can be estimated. Then, combining the coagulation sink together with measured number concentrations and apparent source rates of 3 nm particles, 1 nm particle nucleation rates and concentration can be estimated. To estimate nucleation rates and vapour concentration source rates producing new particle bursts over the Boreal forest regions, three cases from the BIOFOR project were examined using this analytical tool. In this environment, the nucleation mode growth‐rate was observed to be 2–3 nm hour−1, which required a condensable vapour concentration of 2.5–4×107 cm−3 and a source rate of approximately 7.5–11×104 cm−3 s−1 to be sustained. The formation rate of 3 nm particles was ≈1 particle cm−3 s−1 in all three cases. The estimated formation rate of 1 nm particles was 10–100 particles cm−3 s−1, while their concentration was estimated to be between 10,000 and 100,000 particles cm−3. Using hygroscopicity data and mass flux expressions, the mass flux of insoluble vapour is estimated to be of the same order of magnitude as that of soluble vapour, with a soluble to insoluble vapour flux ratio ranging from 0.7 to 1.4 during these nucleation events.

 

Home Environment and Childhood Asthma Home Environment and Childhood Asthma

Date added: 07/31/1994
Date modified: 07/02/2009
Filesize: 224.33 kB

Leen, M.G., O'Connor, T.C., Kelleher, C.C., Loftus, B.G. & Mitchell, C. (1994)- Home environment and childhood asthma. The Irish Medical Journal, Vol. 87, No. 5, pp. 142-144.


Abstract


The prevalence of childhood asthma has increased dramatically in the past 20 years. The reasons for the increase are unclear but many authors suggest that changes in the home environment favourable to proliferation of the house dust mite are to blame. Our study aimed to compare home environment of children with asthma and controls. A questionnaire on home environment was administered to the parents of 134 children with asthma and 118 controls. Detailed studies of home temperature, humidity and dust mite allergen (DERpI) levels were performed in 20 homes (10 from each group). The questionnaire response rate was 86%. There were no significant differences between asthma and control homes with respect to social class, type of housing, smoking habits, pets, insulation, home heating, bedding, carpeting and domestic cleaning habits. A first degree family history of atopy wasobtained in 42% of asthmatic families and in 16% of controls. Temperature, humidity and dust mite allergen levels were similar in both groups. The majority gave readings exceeding recommended norms. Values for DERpI were above thresholds by a factor of 5 in 48%. Home environment does not significantly differ in children with or without asthma. The home environment is now generally mite friendly, and large segments of the childhood population are now exposed to high levels of DERpI. This may account for the increasing prevalence as more and more children with an atopic background develop overt symptoms in response to high levels of allergen load.

Primary marine aerosol emissions size resolved eddy covariance measurements with estimates of the sea salt and organic carbon fractions Primary marine aerosol emissions size resolved eddy covariance measurements with estimates of the sea salt and organic carbon fractions

Date added: 08/01/2007
Date modified: 07/23/2009
Filesize: 1.75 MB

Nilsson, E.D., E. M. Mårtensson, J. S. Van Ekeren, G. de Leeuw, M. Moerman, and C. O'Dowd, Primary marine aerosol emissions: size resolved eddy covariance measurements with estimates of the sea salt and organic carbon fractions, Atmos. Chem. Phys. Discuss., 7, 13345-13400, 2007


Abstract


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.

Organic aerosol formation via sulphate cluster activation Organic aerosol formation via sulphate cluster activation

Date added: 08/06/2004
Date modified: 07/03/2009
Filesize: 667.33 kB

Kulmala, M., V.-M. Kerminen, T. Anttila, A. Laaksonen, and C. D. O'Dowd (2004), Organic aerosol formation via sulphate cluster activation, J. Geophys. Res., 109, D04205, doi:10.1029/2003JD003961.


Abstract


The formation of aerosols, and subsequent cloud condensation nuclei, remains one of the least understood atmospheric processes upon which global climate change critically depends. Under atmospheric conditions, the process of homogeneous nucleation (formation of stable clusters ∼ 1 nm in size), and their subsequent growth into new particles (>3 nm), determines the aerosol and cloud nuclei population, yet, hitherto, no theory has elucidated the new particle formation phenomenon in detail. In this study, we present a new theory which provides a mechanistic explanation for new particle formation via activation of stable inorganic clusters by organic vapors. The new nano-particle activation theory is analogous to Köhler theory which describes cloud formation in a supersaturated water vapor field but differs in that it describes the activation of inorganic stable nano-clusters into aerosol particles in a supersaturated organic vapor which initiates spontaneous and rapid growth of clusters. Inclusion of the new theory into aerosol formation models predicts that increases in organic vapor densities lead to even greater increases in particle production, which, in turn, will influence the global radiative cooling effect of atmospheric aerosols.

 

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