Payday loans
Home Publications Journal Publications

Journal Publications

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

Click on the "Search Document" icon above to find a publication based on the search criteria you create.

 


Documents

Order by : Name | Date | Hits [ Ascendant ]

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.

An ozone budget for the UK using measurements... ozone monitoring network; measured and modelle An ozone budget for the UK using measurements... ozone monitoring network; measured and modelle

Date added: 08/07/2003
Date modified: 07/27/2009
Filesize: 541.71 kB

Coyle M., et al., “An ozone budget for the UK: using measurements from the national ozone  monitoring network; measured and modelled meteorological data, and a 'big-leaf' resistance
analogy model of dry deposition”,  Environmental Pollution, 123 (1), 115-123, 2003.


Abstract


Data from the UK national air-quality monitoring network are used to calculate an annual mass budget for ozone (O3) production and loss in the UK boundary layer during 1996. Monthly losses by dry deposition are quantified from 1 km1 km scale maps of O3 concentration and O3 deposition velocities based on a ‘big  leaf ’ resistance analogy. The quantity of O3 deposition varies from 50 Gg-O3 month1 in the winter to over 200 Gg-O3 month1 in the summer when vegetation is actively absorbing O3. The net O3 production or loss in the UK boundary layer is found by selecting days when the UK is receiving ‘‘clean’’ Atlantic air from the SW to NW. In these conditions, the difference in O3 concentration observed at Mace Head and a rural site on the east coast of the UK indicates the net O3 production or loss within the UK boundary layer. A simple box model is then used to convert the concentration difference into a mass. The final budget shows that for most of the year the UK is a net sink for O3 (25 to 800 Gg-O3 month1) with production only exceeding losses in the photochemically active summer months (+45 Gg-O3 month1).

An overview of the Lagrangian experiments undertaken during the NA regional ACE An overview of the Lagrangian experiments undertaken during the NA regional ACE

Date added: 08/06/2000
Date modified: 06/30/2009
Filesize: 1.51 MB

Johnson, D. W., S. R. Osborne, R. Wood, K. Suhre, M. O. Andrae, R. Johnson, S. Businger, P. K. Quinn, T. Bates, P. Durkee, H. Johnson, L. M. Russell, K. Noone, P. Glantz, B. Bandy, C. O'Dowd, S. Rapsomanikis and J. Rudolph. An overview of the Lagrangian experiments undertaken during the North Atlantic Regional Aerosol Characterisation Experiment (ACE - 2). Tellus, 52B, 290-320. 2000.


Abstract

 

One of the primary aims of the North Atlantic regional Aerosol Characterisation Experiment (ACE-2) was to quantify the physical and chemical processes affecting the evolution of the major aerosol types over the North Atlantic. The best, practical way of doing this is in a Lagrangian framework where a parcel of air is sampled over several tens of hours and its physical and chemical properties are intensively measured. During the intensive observational phase of ACE-2, between 15 June 1997 and 24 July 1997, 3 cloudy Lagrangian experiments and 3 cloud-free, Lagrangian experiments were undertaken between the south west tip of the Iberian Peninsula and the Canary Islands. This paper gives an overview of the aims and logistics of all of the Lagrangian experiments and compares and contrasts them to provide a framework for the more focused Lagrangian papers in this issue and future process modelling studies and parametrisation development. The characteristics of the cloudy Lagrangian experiments were remarkably different, enabling a wide range of different physical and chemical processes to be studied. In the 1st Lagrangian, a clean maritime air mass was sampled in which salt particle production, due to increased wind speed, dominated the change in the accumulation mode concentrations. In the 2nd Lagrangian, extensive cloud cover resulted in cloud processing of the aerosol in a polluted air mass, and entrainment of air from the free troposphere influenced the overall decrease in aerosol concentrations in the marine boundary layer (MBL). Very little change in aerosol characteristics was measured in the 3rd Lagrangian, where the pollution in the MBL was continually being topped up by entraining air from a residual continental boundary layer (CBL) above. From the analysis of all the Lagrangian experiments, it has been possible to formulate, and present here, a generalised description of a European continental outbreak of pollution over the sub-tropical North Atlantic.

 

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

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

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


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

An isotopic study of atmospheric sulphur at three sites in Wales and at Mace Head, Eire An isotopic study of atmospheric sulphur at three sites in Wales and at Mace Head, Eire

Date added: 08/06/1998
Date modified: 07/27/2009
Filesize: 1.36 MB
McArdle N. ; Liss P. ; Dennis P.  1998, An isotopic study of atmospheric sulphur at three sites in Wales and at Mace Head, Eire, J. Geophys. Res. Vol. 103 , No. D23 , p. 31,079 (98JD01664)

Abstract


Sulphur isotope measurements made on aerosol and precipitation samples collected at three sites in Wales and Mace Head, Eire, between March 1993 and 1994, had highest non-sea-salt sulphate δ34S values, up to 11.9‰ for aerosol and 9.7‰ for precipitation, during the summer months. Aerosol methanesulphonate shows a clear summer peak with values up to 3-4 nmol m-3. Assuming samples contained only sulphur from terrestrial/anthropogenic, sea salt, and marine biogenic (from the oxidation of dimethylsulphide) sources, we used the sulphur isotope values to determine the contribution of dimethylsulphide-derived sulphate to total sulphate. In general the biogenic contribution was small, < 10%, although in samples from marine air masses it was as high as 40%. A comparison of aerosol and precipitation δ34S values found no evidence for large isotopic fractionations during the oxidation of sulphur dioxide.

An investigation of the behaviour of drops and drop-pairs subjected to strong electrical forces An investigation of the behaviour of drops and drop-pairs subjected to strong electrical forces

Date added: 09/12/1971
Date modified: 07/23/2009
Filesize: 703.62 kB

Brazier-Smith, P.R., Jennings, S.G., and Latham, J.  (1971)- An investigation of the behaviour of drops and drop-pairs subjected to strong electrical forces. Proc. Roy. Soc., A325, 363-376.


Abstract


A numerical model is described which simulates irrotational, incompressible flow on a computer. It has been applied to the problems of the deformation of uncharged drop-pairs separated in an electric field of critical strength and isolated drops charged to the Rayleigh limit in the absence of an electric field. In the case of pairs of drops of radius R, separated by an initial distance X in an electric field equal to that predicted by Brazier-Smith (1971) to cause disruption two types of interaction were identified. For values of X/R less than about 1.2 the drops deform and their surfaces accelerate towards each other and make contact. For X/R greater than about 1.2 the drops deform, a concavity appears at the near poles and then the near surfaces assume a conical profile of angle equal to that predicted by Taylor (1964). The subsequent issuance of liquid from these jets could not be studied with the present model. The computations predict that an isolated drop carrying the critical charge calculated by Rayleigh (1882) will deform, while retaining an approximately spheroidal shape, until the axial ratio achieves a value of about 2.5, whereupon cones possessing the Taylor angle are formed at each end of the drop, from which liquid will issue in the form of a jet. Experiments were performed in which uncharged water drops of radius R and surface tension T were directed towards a highly polished, earthed electrode at a shallow angle in an electric field of strength E. Each drop experienced the same electric forces as would result if the earthed electrode were removed and replaced by an identical drop twice as far away. Stroboscopic photographs of drops and their optical image in the polished electrode illustrated their deformation and eventual disintegration. The experimentally determined relation between normalized disintegration field E(R/T)1/4 and both X/R and the elongation a/b agreed well with theory over a wide range of separations.

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

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

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


Abstract

 

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

 

An automated system for near-real time monitoring of trace atmospheric halocarbons An automated system for near-real time monitoring of trace atmospheric halocarbons

Date added: 08/05/1998
Date modified: 07/27/2009
Filesize: 122.2 kB

An Automated System for Near-Real-Time Monitoring of Trace Atmospheric Halocarbons, Bassford, M.R., Simmonds, P.G., and Nickless, G.,Anal. Chem., 70, 5, 958 - 965, 1998,  10.1021/ac970861z


Abstract


A new gas chromatographic method developed to quantitatively determine important atmospheric halocarbons is described. Target compounds include replacement CFCs, chlorinated solvents, and biosynthesized (naturally produced) organohalogens, all trace gases in the atmosphere at concentrations ranging from 0.1 to 600 pptv (where pptv = 1 part in 10-12 by volume). A combination of ultralow concentrations and relatively small electron attachment cross sections renders these compounds very difficult to routinely measure in the background air typical of remote atmospheric monitoring stations. Detection is achieved by preconcentration of a 200-mL air sample using an adsorbent-filled microtrap and enhancement of electron capture detector response by oxygen doping one of two detectors connected in series. Oxygen doping specifically targets halocarbons with relatively poor electron attachment rate coefficients. The work described here details construction of a novel analytical system, laboratory trials, and optimization followed by an extended field campaign at a remote atmospheric monitoring station, Mace Head, Ireland. A calibration standard or ambient air sample was acquired every hour using a cyclic, automated procedure without employing cryogenic preconcentration or refocusing. Overall precision of the analytical method for the target compounds is between 0.3 and 1.5%.

 

An assessment of the surface ozone trend in Ireland relevant to air pollution and environmental protection An assessment of the surface ozone trend in Ireland relevant to air pollution and environmental protection

Date added: 03/12/2013
Date modified: 03/12/2013
Filesize: 442.05 kB

Tripathi, Om, P., Stephen G. Jennings, Colin O’Dowd, Barbara O’Leary, Keith Lambkin, Eoin Moran, Simon J. O’Doherty and T. Gerard Spain, An assessment of the surface ozone trend in Ireland relevant to air pollution and environmental protection, Atmos. Pollution Res., 3, 341-351, 2012.


Abstract. Hourly data (1994–2009) of surface ozone concentrations at eight monitoring sites have been investigated to assess target level and long–term objective exceedances and their trends. The European Union (EU) ozone target value for human health (60 ppb–maximum daily 8–hour running mean) has been exceeded for a number of years for almost all sites but never exceeded the set limit of 25 exceedances in one year. Second highest annual hourly and 4th highest annual 8–hourly mean ozone concentrations have shown a statistically significant negative trend for in–land sites of Cork–Glashaboy, Monaghan and Lough Navar and no significant trend for the Mace Head site. Peak afternoon ozone concentrations averaged over a three year period from 2007 to 2009 have been found to be lower than corresponding values over a three–year period from 1996 to 1998 for two sites: Cork–Glashaboy and Lough Navar sites. The EU long–term objective value of AOT40 (Accumulated Ozone Exposure over a threshold of 40 ppb) for protection of vegetation (3 ppm–hour, calculated from May to July) has been exceeded, on an individual year basis, for two sites: Mace Head and Valentia. The critical level for the protection of forest (10 ppm–hour from April to September) has not been exceeded for any site except at Valentia in the year 2003. AOT40–Vegetation shows a significant negative trend for a 3–year running average at Cork–Glashaboy (–0.13±0.02 ppm–hour per year), at Lough Navar (–0.05±0.02 ppm–hour per year) and at Monaghan (–0.03±0.03 ppm–hour per year–not statistically significant) sites. No statistically significant trend was observed for the coastal site of Mace head. Overall, with the exception of the Mace Head and Monaghan sites, ozone measurementrecords at Irish sites show a downward negative trend in peak values that affect human health and vegetation.

 

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.

 

An analysis of condensation nuclei levels at Mace Head, Ireland An analysis of condensation nuclei levels at Mace Head, Ireland

Date added: 07/31/1999
Date modified: 07/27/2009
Filesize: 737.83 kB

Mc Govern, F.M. (1999). An analysis of condensation nuclei levels at Mace Head, Ireland. Atmos. Environ., 33, 1711-1723.


Abstract


Condensation nuclei (CN) concentrations measured at Mace Head between 1990 and 1992 are presented. The background CN concentration was found to typically range from 100 to 700 cm-3. Concentration values were in this range for 55% of the measurement period. No seasonal cycle was observed in the CN concentration values. Concurrent equivalent black carbon (EBC) measurements are used to examine anthropogenic influences on the background CN concentration. Evidence that transatlantic air mass transport influenced the background CN concentration contributing to increased CN and EBC levels, is shown. During polluted conditions the CN concentration was generally higher than 1000 cm-3. The principal source for high pollution levels was European air masses arriving at the site. Very high CN concentrations, greater than 50 000 cm-3, are attributed to local gas-to-particle conversion processes. The characteristics of a number of particle production events are considered. These show that these events are highly photochemical and occur during both clean and polluted conditions. Such production events though infrequent contributed significantly to the total aerosol number concentration.

Aitken Nuclei Measurements and Evidence of Gas-to-particle conversion Processes at Mace Head, Ireland.. Aitken Nuclei Measurements and Evidence of Gas-to-particle conversion Processes at Mace Head, Ireland..

Date added: 08/26/1994
Date modified: 07/23/2009
Filesize: 840.25 kB

O'Connor, T.C., McGovern, F.M., Jennings, S.G. & Philipp, C.(University of Hannover)  (1994)-
Aitken nuclei measurements and evidence of gas-to-particle conversion processes at Mace Head, Ireland. Proceedings of  EUROTRAC 94 Symposium, The Hague, SPB Academic Publishing, 1206-1209.


Aircraft Measurements During NAMBLEX (the SNAP campaign) Aircraft Measurements During NAMBLEX (the SNAP campaign)

Date added: 08/06/2003
Date modified: 07/27/2009
Filesize: 33.65 kB
Purvis R.M., Lewis A.C., McQuaid J.B. & Lee J.D. "Aircraft Measurements During NAMBLEX (the SNAP campaign)." Geophys Res. Abs. 6 (2004):

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 the 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 samples taken from onboard the aircraft with ground analysis using GC-FID were 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 during the summer of 2002. 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 hydrocarbon and 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 site showed good agreement between ground based and airborne hydrocarbon 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 a boundary 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.

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.

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

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

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


Abstract


A light aircraft was equipped with a bank of Condensation Particle Counters (CPCs) (50% cut from 3–5.4–9.6 nm) and a nano-Scanning Mobility Particle Sizer (nSMPS) and deployed along the west coast of Ireland, in the vicinity of Mace Head. The objective of the exercise was to provide high resolution micro-physical measurements of the coastal nucleation mode in order to map the spatial extent of new particle production regions and to evaluate the evolution, and associated growth rates of the coastal nucleation-mode aerosol plume. Results indicate that coastal new particle production is occurring over most areas along the land-sea interface with peak concentrations at the coastal plume-head in excess of 106 cm−3. Pseudo-Lagrangian studies of the coastal plume evolution illustrated significant growth of new particles to sizes in excess of 8 nm approximately 10 km downwind of the source region. Close to the plume head (<1 km) growth rates can be as high as 123–171 nm h−1, decreasing gradually to 53–72 nm h−1 at 3 km. Further along the plume, at distances up to 10 km, the growth rates are calculated to be 17–32 nm h−1. Growth rates of this magnitude suggest that after a couple of hours, coastal nucleation mode particles can reach significant sizes where they can contribution to the regional aerosol loading.

Airborne concentrations and deposition fluxes of major and trace species at marine stations in Airborne concentrations and deposition fluxes of major and trace species at marine stations in

Date added: 08/05/1997
Date modified: 06/30/2009
Filesize: 1.36 MB

Foltescu et al (1996). V.L. Foltescu, E. Selin Lindgren, J. Isakson, M. Oblad, R. Tiede, J. Sommar, J.M. Pacyna and K. Toerseth , Airborne concentrations and deposition fluxes of major and trace species at marine stations in southern Scandinavia. Atmospheric Environment 30 22 (1996), pp. 3857–3872.


Abstract


Extensive measurements of airborne concentrations and deposition fluxes of many major and trace species were performed within the framework of the BMCAPE project (Background Maritime Contribution to Atmospheric Pollution in Europe) at two Scandinavian sites (Saby in Sweden and Lista in Norway) during four seasons in 1993 and 1994. The study focused on gaseous and particulate S-, N- and CI-species.Airborne concentration levels during the different campaigns, seasons and the various air masses encountered are presented for the following gaseous and particulate species: SO2, HCl, NOx, HNO3, NH3, SO2-4, NH+4, NO-3, S, Cl, K, Ca, V, Ni, Zn, Br, Pb and condensation nuclei. In addition, particle concentrations of Ti, Fe, Cu and Mn are discussed in the text. A time series is given for particulate and gaseous Hg. Annual flux estimates for Southern Scandinavia are given for Mn, Fe, Ni, Cu, Zn, Pb, Cl, S, non-sea-salt-sulphate-S, As, Na, K, Ca, Mg, NO-3-N and NH+4-N. Based on direct flux measurements to a water surface, dry deposition velocities are determined for nine elements: Mn, Fe, Ni, Cu, Zn, Pb, Cl, S, Ca.

 

Air Pollution Measurements at Macehead Air Pollution Measurements at Macehead

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

Air Pollution Measurements at Macehead Air Pollution Measurements at Macehead

Date added: 08/07/1988
Date modified: 09/11/2009
Filesize: 2.14 MB

AGAGE Observations of Methyl Bromide and Methyl Chloride at Mace Head, Ireland, and Cape Grim, Tasmania, 1998–2001 AGAGE Observations of Methyl Bromide and Methyl Chloride at Mace Head, Ireland, and Cape Grim, Tasmania, 1998–2001

Date added: 08/01/2004
Date modified: 07/27/2009
Filesize: 593.54 kB

Simmonds, P.; Derwent, R.; Manning, A.; Fraser, P.; Krummel, P.; O'Doherty, S.; Prinn, R.; Cunnold, D.; Miller, B.; Wang, H.; Ryall, D.; Porter, L.; Weiss, R.; Salameh, P. ,AGAGE Observations of Methyl Bromide and Methyl Chloride at Mace Head, Ireland, and Cape Grim, Tasmania, 1998–2001, Journal of Atmospheric Chemistry, pg 1573-0662


Abstract


In situ AGAGE GC-MS measurements of methyl bromide (CH3Br) and methyl chloride (CH3Cl) at Mace Head, Ireland and Cape Grim, Tasmania (1998–2001) reveal a complex pattern of sources. At Mace Head both gases have well-defined seasonal cycles with similar average annual decreases of 3.0% yr−1 (CH3Br) and 2.6% yr−1 (CH3Cl), and mean northern hemisphere baseline mole fractions of 10.37 ± 0.05 ppt and 535.7 ± 2.2 ppt, respectively. We have used a Lagrangian dispersion model and local meteorological data to segregate the Mace Head observations into different source regions, and interpret the results in terms of the known sources and sinks of these two key halocarbons. At Cape Grim CH3Br and CH3Cl also show annual decreases in their baseline mixing ratios of 2.5% yr−1 and 1.5% yr−1, respectively. Mean baseline mole fractions were 7.94 ± 0.03 ppt (CH3Br) and 541.3 ± 1.1 ppt (CH3Cl). Although CH3Cl has astrong seasonal cycle there is no well-defined seasonal cycle in the Cape Grim CH3Br record. The fact that both gases are steadily decreasing in the atmosphere at both locations implies that a change has occurred which is affecting a common, major source of both gases (possibly biomass burning) and/or their major sink process (destruction by hydroxyl radical).

AGAGE Observations of Methyl Bromide and Methyl Chloride at Mace Head, Ireland, and Cape Grim, Tasmania, 1998–2001 AGAGE Observations of Methyl Bromide and Methyl Chloride at Mace Head, Ireland, and Cape Grim, Tasmania, 1998–2001

Date added: 08/01/2004
Date modified: 06/30/2009
Filesize: 593.54 kB

Simmonds, P.; Derwent, R.; Manning, A.; Fraser, P.; Krummel, P.; O'Doherty, S.; Prinn, R.; Cunnold, D.; Miller, B.; Wang, H.; Ryall, D.; Porter, L.; Weiss, R.; Salameh, P. ,AGAGE Observations of Methyl Bromide and Methyl Chloride at Mace Head, Ireland, and Cape Grim, Tasmania, 1998–2001, Journal of Atmospheric Chemistry, pg 1573-0662


Abstract


In situ AGAGE GC-MS measurements of methyl bromide (CH3Br) and methyl chloride (CH3Cl) at Mace Head, Ireland and Cape Grim, Tasmania (1998–2001) reveal a complex pattern of sources. At Mace Head both gases have well-defined seasonal cycles with similar average annual decreases of 3.0% yr−1 (CH3Br) and 2.6% yr−1 (CH3Cl), and mean northern hemisphere baseline mole fractions of 10.37 ± 0.05 ppt and 535.7 ± 2.2 ppt, respectively. We have used a Lagrangian dispersion model and local meteorological data to segregate the Mace Head observations into different source regions, and interpret the results in terms of the known sources and sinks of these two key halocarbons. At Cape Grim CH3Br and CH3Cl also show annual decreases in their baseline mixing ratios of 2.5% yr−1 and 1.5% yr−1, respectively. Mean baseline mole fractions were 7.94 ± 0.03 ppt (CH3Br) and 541.3 ± 1.1 ppt (CH3Cl). Although CH3Cl has astrong seasonal cycle there is no well-defined seasonal cycle in the Cape Grim CH3Br record. The fact that both gases are steadily decreasing in the atmosphere at both locations implies that a change has occurred which is affecting a common, major source of both gases (possibly biomass burning) and/or their major sink process (destruction by hydroxyl radical).

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

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

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


Abstract.

 

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

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

concentrations were of the order of 3000 cm

 

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

Aerosol physico-chemical characteristics over a boreal forest determined by volatility analysis Aerosol physico-chemical characteristics over a boreal forest determined by volatility analysis

Date added: 07/31/2000
Date modified: 06/30/2009
Filesize: 154.04 kB

O'Dowd, C.D., E. Becker, J.M. Makela, M. Kulmala, Aerosol physic-chemical characteristics over a boreal forest determined by volatility analysis, Boreal Environment Research, 4, 337-348, 2000


Abstract


A thermal volatility technique was used in the boreal forest environment to examine accumulation mode (0.05–0.35 µm radius) physico-chemical properties as a function of air mass origin. Three primary aerosol species were identified in all air masses: (1) a semi-volatile organic component, (2) ammonium sulphate, and (3) a non-volatile component thought to comprise mostly of soot carbon. Under some conditions, sulphuric acid was also identified, as was sea salt. Following nucleation and growth of new particles into accumulation mode sizes, the organic fraction of accumulation mode aerosol, by mass, was observed to increase from 30%, prior to and during the nucleation event, up to 75% by the end of the growth period, indicating a substantial fraction of organic mass condensing onto newly formed particles.

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

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

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


Abstract


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

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

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

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

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

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

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


Abstract.

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

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

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

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

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


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

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

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

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


Abstract


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

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

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

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

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.

Aerosol formation during PARFORCE: Ternary nucleation of H2SO4, NH3 and H2O Aerosol formation during PARFORCE: Ternary nucleation of H2SO4, NH3 and H2O

Date added: 07/31/2002
Date modified: 07/27/2009
Filesize: 354.52 kB
Markku Kulmala, Pekka Korhonen, Ismo Napari, Robert Jansson, Harald Berresheim, and Colin O'Dowd, Aerosol formation during PARFORCE: Ternary nucleation of H2SO4, NH3 and H2O, J. Geophys. Res., 107, 10.1029/2001JD000900, 2002.

Abstract


A new version of a ternary nucleation (sulphuric acid-ammonia-water) model based on classical nucleation theory, but with an improved ability to predict nucleation rates over a larger temperature range (258–303 K) compared with previous work, is presented. The modeled nucleation rates are given as a function of temperature and ambient acid and ammonia concentrations. For the first time the predicted ternary nucleation rates are compared to the observed particle production rates using measured ambient sulphuric acid and ammonia concentrations as input data. The ambient gas concentrations were measured simultaneously to aerosol formation rates during the 1999 New Particle Formation and Fate in the Coastal Environment (PARFORCE) coastal field campaign at Mace Head. According to the results, daytime ambient acid and ammonia concentrations were significantly higher than required by model calculations to induce the formation of new particles by homogeneous ternary nucleation. However, binary nucleation of sulphuric acid-water molecules is not able to predict new particle formation since the binary nucleation rate is far too small. We conclude that all particle formation events observed at coastal sites can be initiated by ternary nucleation of sulphuric acid, ammonia, and water vapor. However, related studies illustrate that ambient sulphuric acid concentrations are, nevertheless, insufficient to explain observed rapid growth of particles from 1 to 3 nm sizes which can be detected by current instrumentation.

Aerosol dynamics in ship tracks Aerosol dynamics in ship tracks

Date added: 08/06/1999
Date modified: 07/23/2009
Filesize: 1.65 MB

Russell, L. M. ; Seinfeld, J. H. ; Flagan, R. C. ; Ferek, R. J. ; Hegg, D. A. ; Hobbs, P. V. ;  Wobrock, W. ;  Flossmann, A. I. ; O'Dowd, C. D. ; Nielsen, K. E. ; Durkee, P. A.  1999 Aerosol dynamics in ship tracks J. Geophys. Res. Vol. 104 , No. D24 , p. 31,077-31096 DOI 10.1029/1999JD900985


Abstract

 

Ship tracks are a natural laboratory to isolate the effect of anthropogenic aerosol emissions on cloud properties. The Monterey Area Ship Tracks (MAST) experiment in the Pacific Ocean west of Monterey, California, in June 1994, provides an unprecedented data set for evaluating our understanding of the formation and persistence of the anomalous cloud features that characterize ship tracks. The data set includes conditions in which the marine boundary layer is both clean and continentally influenced. Two case studies during the MAST experiment are examined with a detailed aerosol microphysical model that considers an external mixture of independent particle populations. The model allows tracking individual particles through condensational and coagulational growth to identify the source of cloud condensation nuclei (CCN). In addition, a cloud microphysics model was employed to study specific effects of precipitation. Predictions and observations reveal important differences between clean (particle concentrations below 150 cm-3) and continentally influenced (particle concentrations above 400 cm-3) background conditions: in the continentally influenced conditions there is a smaller change in the cloud effective radius, drop number and liquid water content in the ship track relative to the background than in the clean marine case. Predictions of changes in cloud droplet number concentrations and effective radii are consistent with observations although there is significant uncertainty in the absolute concentrations due to a lack of measurements of the plume dilution. Gas-to-particle conversion of sulfur species produced by the combustion of ship fuel is predicted to be important in supplying soluble aerosol mass to combustion-generated particles, so as to render them available as CCN. Studies of the impact of these changes on the cloud's potential to precipitate concluded that more complex dynamical processes must be represented to allow sufficiently long drop activations for drizzle droplets to form.

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

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

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


Abstract


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

Aerosol direct radiative effects over the northwest Atlantic, northwest Pacific, and North Indian Oc Aerosol direct radiative effects over the northwest Atlantic, northwest Pacific, and North Indian Oc

Date added: 08/01/2006
Date modified: 07/10/2009
Filesize: 2.78 MB

Bates, T. S. , T. L. Anderson, T. Baynard, T. Bond, O. Boucher, G. Carmichael, A. Clarke, C. Erlick, H. Guo, L. Horowitz, S. Howell, S. Kulkarni, H. Maring, A. McComiskey, A. Middlebrook, K. Noone, C. D. O'Dowd, J. Ogren, J. Penner, P. K. Quinn, A. R. Ravishankara, D. L. Savoie, S. E. Schwartz, Y. Shinozuka, Y. Tang, R. J. Weber and Y. Wu, Aerosol direct radiative effects over the northwest Atlantic, northwest Pacific, and North Indian Oceans: estimates based on in-situ chemical and optical measurements and chemical transport modelling, Atmospheric Chemistry and Physics Discussions, Vol. 6, pp 175-362, 2006.


Abstract


The largest uncertainty in the radiative forcing of climate change over the industrial era is that due to aerosols, a substantial fraction of which is the uncertainty associated with scattering and absorption of shortwave (solar) radiation by anthropogenic aerosols in cloud-free conditions (IPCC, 2001). Quantifying and reducing the uncertainty in aerosol influences on climate is critical to understanding climate change over the industrial period and to improving predictions of future climate change for assumed emission scenarios. Measurements of aerosol properties during major field campaigns in several regions of the globe during the past decade are contributing to an enhanced understanding of atmospheric aerosols and their effects on light scattering and climate. The present study, which focuses on three regions downwind of major urban/population centers (North Indian Ocean (NIO) during INDOEX, the Northwest Pacific Ocean (NWP) during ACE-Asia, and the Northwest Atlantic Ocean (NWA) during ICARTT), incorporates understanding gained from field observations of aerosol distributions and properties into calculations of perturbations in radiative fluxes due to these aerosols. This study evaluates the current state of observations and of two chemical transport models (STEM and MOZART). Measurements of burdens, extinction optical depth (AOD), and direct radiative effect of aerosols (DRE – change in radiative flux due to total aerosols) are used as measurement-model check points to assess uncertainties. In-situ measured and remotely sensed aerosol properties for each region (mixing state, mass scattering efficiency, single scattering albedo, and angular scattering properties and their dependences on relative humidity) are used as input parameters to two radiative transfer models (GFDL and University of Michigan) to constrain estimates of aerosol radiative effects, with uncertainties in each step propagated through the analysis. Constraining the radiative transfer calculations by observational inputs increases the clear-sky, 24-h averaged AOD (34±8%), top of atmosphere (TOA) DRE (32±12%), and TOA direct climate forcing of aerosols (DCF – change in radiative flux due to anthropogenic aerosols) (37±7%) relative to values obtained with "a priori" parameterizations of aerosol loadings and properties (GFDL RTM). The resulting constrained clear-sky TOA DCF is −3.3±0.47, −14±2.6, −6.4±2.1 Wm−2 for the NIO, NWP, and NWA, respectively. With the use of constrained quantities (extensive and intensive parameters) the calculated uncertainty in DCF was 25% less than the "structural uncertainties" used in the IPCC-2001 global estimates of direct aerosol climate forcing. Such comparisons with observations and resultant reductions in uncertainties are essential for improving and developing confidence in climate model calculations incorporating aerosol forcing.

Aerosol deposition in turbulent channel flow on a regular array of three-dimensional roughness elements Aerosol deposition in turbulent channel flow on a regular array of three-dimensional roughness elements

Date added: 07/31/2001
Date modified: 06/30/2009
Filesize: 527.45 kB
Lai, A.C.K., Byrne, M.A. and Goddard, A.J.H. Aerosol deposition in turbulent channel flow on a regular array of three-dimensional roughness elements. J. Aerosol Sci., 32, 121-137, 2001.

Abstract


Understanding particle deposition onto rough surfaces is important for many engineering and environmental applications. An experimental system was designed for the study of aerosol 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 0.7-7.1mum. The Reynolds number for the test conditions was 44,000 in the 150 mm square duct. The roughness elements were arranged at two different orientations with respect to the airflow direction and the aerosol deposition velocity and pressure drop were measured for both orientations. Compared to earlier measurements in the same duct system involving smooth or ribbed surfaces, a significant increase in deposition velocity onto the regular roughness elements is observed. In addition, the associated pressure loss penalty is lower than in the presence of the roughness elements than in the presence of the ribbed surfaces. This may be attributable to the small dimensionless roughness height of the elements, which results only in a moderate distortion of the flow structure near the surfaces.

Aerosol decadal trends – Part 2: In-situ aerosol particle number concentrations at GAW and ACTRIS stations Aerosol decadal trends – Part 2: In-situ aerosol particle number concentrations at GAW and ACTRIS stations

Date added: 03/12/2013
Date modified: 03/12/2013
Filesize: 6.1 MB

Asmi, A., M. Collaud Coen, J.A. Ogren, E. Andrews, P. Sheridan, A. Jefferson, E. Weingartner, U. Baltensperger, N. Bukowiecki, H. Lihavainen, N. Kivekäs, E. Asmi, P. P. Aalto, M. Kulmala, A. Wiedensohler, W. Birmili, A. Hamed, C. O'Dowd, S. G Jennings, R. Weller, H. Flentje, A. M. Fjaeraa, M. Fiebig, C. L. Myhre, A. G. Hallar, E. Swietlicki, A. Kristensson, and P. Laj,Aerosol decadal trends – Part 2: In-situ aerosol particle number concentrations at GAW and ACTRIS stations, Atmos. Chem. Phys., 13, 895-916, 2013, www.atmos-chem-phys.net/13/895/2013/ doi:10.5194/acp-13-895-2013


Abstract. We have analysed the trends of total aerosol particle number concentrations (N) measured at long-term measurement stations involved either in the Global Atmosphere Watch (GAW) and/or EU infrastructure project ACTRIS. The sites are located in Europe, North America, Antarctica, and on Pacific Ocean islands. The majority of the sites showed clear decreasing trends both in the full-length time series, and in the intra-site comparison period of 2001–2010, especially during the winter months. Several potential driving processes for the observed trends were studied, and even though there are some similarities between N trends and air temperature changes, the most likely cause of many northern hemisphere trends was found to be decreases in the anthropogenic emissions of primary particles, SO2 or some co-emitted species. We could not find a consistent agreement between the trends of N and particle optical properties in the few stations with long time series of all of these properties. The trends of N and the proxies for cloud condensation nuclei (CCN) were generally consistent in the few European stations where the measurements were available. This work provides a useful comparison analysis for modelling studies of trends in aerosol number concentrations.

 

Aerosol decadal trends – Part 1: In-situ optical measurements at GAW and IMPROVE stations Aerosol decadal trends – Part 1: In-situ optical measurements at GAW and IMPROVE stations

Date added: 03/12/2013
Date modified: 03/12/2013
Filesize: 2.64 MB

Collaud Coen, M., E. Andrews, A. Asmi, U. Baltensperger, N. Bukowiecki, D. Day, M. Fiebig, A. M. Fjaeraa, H. Flentje, A. Hyvärinen, A. Jefferson, S. G. Jennings, G. Kouvarakis, H. Lihavainen, C. Lund Myhre, W. C. Malm, N. Mihapopoulos, J. V. Molenar, C. O'Dowd, J. A. Ogren, B. A. Schichtel, P. Sheridan, A. Virkkula, E. Weingartner, R. Weller, and P. Laj,Aerosol decadal trends – Part 1: In-situ optical measurements at GAW and IMPROVE stations, Atmos. Chem. Phys., 13, 869-894, 2013, www.atmos-chem-phys.net/13/869/2013/doi:10.5194/acp-13-869-2013.


Abstract. Currently many ground-based atmospheric stations include in-situ measurements of aerosol physical and optical properties, resulting in more than 20 long-term (> 10 yr) aerosol measurement sites in the Northern Hemisphere and Antarctica. Most of these sites are located at remote locations and monitor the aerosol particle number concentration, wavelength-dependent light scattering, backscattering, and absorption coefficients. The existence of these multi-year datasets enables the analysis of long-term trends of these aerosol parameters, and of the derived light scattering Ångström exponent and backscatter fraction. Since the aerosol variables are not normally distributed, three different methods (the seasonal Mann-Kendall test associated with the Sen's slope, the generalized least squares fit associated with an autoregressive bootstrap algorithm for confidence intervals, and the least-mean square fit applied to logarithms of the data) were applied to detect the long-term trends and their magnitudes. To allow a comparison among measurement sites, trends on the most recent 10 and 15 yr periods were calculated. No significant trends were found for the three continental European sites. Statistically significant trends were found for the two European marine sites but the signs of the trends varied with aerosol property and location. Statistically significant decreasing trends for both scattering and absorption coefficients (mean slope of −2.0% yr−1) were found for most North American stations, although positive trends were found for a few desert and high-altitude sites. The difference in the timing of emission reduction policy for the Europe and US continents is a likely explanation for the decreasing trends in aerosol optical parameters found for most American sites compared to the lack of trends observed in Europe. No significant trends in scattering coefficient were found for the Arctic or Antarctic stations, whereas the Arctic station had a negative trend in absorption coefficient. The high altitude Pacific island station of Mauna Loa presents positive trends for both scattering and absorption coefficients.

 

Aerosol Climatology Measurements with a Nolan-Pollack Counter.. Aerosol Climatology Measurements with a Nolan-Pollack Counter..

Date added: 07/31/1991
Date modified: 07/27/2009
Filesize: 1.24 MB

O'Connor, T.C & McGovern, F.M. (1991)- Aerosol climatology measurements with a Nolan-Pollak counter. Atmospheric Environment, 25A, pp. 563-567.


Abstract


The Nolan-Pollak photoelectic Nucleus Counter was originally developed in the 1940s for aerosol climatology measurements although its versatility led subsequently to many other applications in aerosol science. It has been widely used in manuel, automatic and modified forms in many parts of the world to record ambient concentrations of Aitken nuclei. The design calibrations and performance of an automatic counter is described. Measurements of Aikten nuclei at MAce HEad, Ireland, are used to discuss it's sustainablity for the prpose of aerosol climatology.

 

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

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

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


Abstract


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

Aerosol analysis and forecast in the ECMWF Integrated Forecast System: 3. Evaluation by means of case studies Aerosol analysis and forecast in the ECMWF Integrated Forecast System: 3. Evaluation by means of case studies

Date added: 03/14/2013
Date modified: 03/14/2013
Filesize: 4.4 MB

Mangold, A., H. De Backer, B. De Paepe, S. Dewitte, I. Chiapello, Y. Derimian, M. Kacenelenbogen, J.‐F. Léon, N. Huneeus, M. Schulz, D. Ceburnis, C. O’Dowd, H. Flentje, S. Kinne, A. Benedetti, J.‐J. Morcrette and O. Boucher, Aerosol analysis and forecast in the ECMWF Integrated Forecast System: 3. Evaluation by means of case studies, J. Geophys. Res., 116, D03302, doi:10.1029/2010JD014864., 2011.


Abstract. A near real‐time system for assimilation and forecasts of aerosols, greenhouse and trace gases, extending the ECMWF Integrated Forecasting System (IFS), has been developed in the framework of the Global and regional Earth‐system Monitoring using Satellite and in‐situ data (GEMS) project. The GEMS aerosol modeling system is novel as it is the first aerosol model fully coupled to a numerical weather prediction model with data assimilation. A reanalysis of the period 2003–2009 has been carried out with the same system. During its development phase, the aerosol system was first run for the time period January 2003 to December 2004 and included sea salt, desert dust, organic matter, black carbon, and sulfate aerosols. In the analysis, Moderate Resolution Imaging Spectroradiometer (MODIS) total aerosol optical depth (AOD) at 550 nm over ocean and land (except over bright surfaces) was assimilated. This work evaluates the performance of the aerosol system by means of case studies. The case studies include (1) the summer heat wave in Europe in August 2003, characterized by forest fire aerosol and conditions of high temperatures and stagnation, favoring photochemistry and secondary aerosol formation, (2) a large Saharan dust event in March 2004, and (3) periods of high and low sea salt aerosol production. During the heat wave period in 2003, the linear correlation coefficients between modeled and observed AOD (550 nm) and between modeled and observed PM2.5 mass concentrations are 0.82 and 0.71, respectively, for all investigated sites together. The AOD is slightly and the PM2.5 mass concentration is clearly overestimated by the aerosol model during this period. The simulated sulfate mass concentration is significantly correlated with observations but is distinctly overestimated. The horizontal and vertical locations of the main features of the aerosol distribution during the Saharan dust outbreak are generally well captured, as well as the timing of the AOD peaks. The aerosol model simulates winter sea salt AOD reasonably well, however, showing a general overestimation. Summer sea salt events show a better agreement. Overall, the assimilation of MODIS AOD data improves the subsequent aerosol predictions when compared with observations, in particular concerning the correlation and AOD peak values. The assimilation is less effective in correcting a positive (PM2.5, sulfate mass concentration, Angström exponent) or negative (desert dust plume AOD) model bias.

 

 

 

 

 

 

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

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

Abstract


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

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

Accumulation rates of the heavy metals lead, mercury and cadmium in ombrotrophic peatlands in the We Accumulation rates of the heavy metals lead, mercury and cadmium in ombrotrophic peatlands in the We

Date added: 08/26/2006
Date modified: 07/09/2009
Filesize: 788.52 kB

Coggins, A. M.; Jennings, S. G.; Ebinghaus, R. (2006): Accumulation rates of the heavy metals lead, mercury and cadmium in ombrotrophic peatlands in the west of Ireland, Atmospheric Environment, 40, 260 - 270


Abstract


The vertical distributions of three heavy metals: Hg, Pb and Cd were determined in 3 cores sampled from two ombrotrophic bogs in the west of Ireland, one at Knockroe Co. Mayo, and the second at Letterfrack National Park, Co. Galway. Core chronologies were established using 210Pb dating techniques and were checked with fallout radionuclides from weapons testing. Variations were found in metal concentrations and cumulative inventories of each of the metals within each site and between the two sites. Maximum accumulation rates of the anthropogenically derived elements Hg, Pb, and Cd, were found in peat sediments dated between 1950 and 1970s at both sites. Pb and Hg accumulation rates are slightly lower than those found in similar studies from remote sites in Europe. Hg accumulation rates are fairly similar to those found in peatlands in America. Unlike the Pb and Hg concentration profiles, the Cd concentration profiles at the Letterfrack site were dominated by a surface enrichment, thought to be due to biological cycling of Cd in the peat. However Cd accumulation rates calculated at the Knockroe site are lower than those observed in Eastern Europe. Local meteorological conditions at the sites chosen for this study may account for the lower concentrations profiles observed when compared with some of the European studies. The similarity between the timing of the increase in metal accumulation rates in peat bogs in Northern America and this study could indicate that long range transportation of trace metals from Northern America may be occurring. Lead accumulations in the surface peat sediments (1993–1996) were between 1.5–3.0 mgm2 yr1 and 4–5 mgm2 yr1 at Knockroe and Letterfrack, respectively. Mercury accumulation rates for the same period at Knockroe were found to be between 6–11 mgm2 yr1, and between 19–24 mgm2 yr1 at Letterfrack. A greater variation in surface Cd accumulation rates was observed at both sites, with surface layer accumulation rates varying from 25 to 50 mgm2 yr1 at Knockroe and between 166 and 405 mgm2 yr1 at Letterfrack. Higher metal concentrations were found at the Letterfrack site, which are most likely due to local sources and the history of the site.

Accelerated Rates of Rainfall Accelerated Rates of Rainfall

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

Abstract

 

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

A two-column method for long-term monitoring of non-methanehydrocarbons (NMHCs) and oxygenated volat A two-column method for long-term monitoring of non-methanehydrocarbons (NMHCs) and oxygenated volat

Date added: 08/31/2003
Date modified: 07/23/2009
Filesize: 174.39 kB

Hopkins, J. R., Read, K. A., and Lewis, A. C.: A Two Column Method for Long-term Monitoring of Non-Methane Hydrocarbons (NMHCs) and Oxygenated Volatile Organic Compounds, J. Envir. Mon., 5, 8–13, 2003.


Abstract


 

A method has been developed for concurrent analysis of C2–C7 hydrocarbons and C2–C5 oxygenated volatile organic compounds (o-VOCs) including alcohols, aldehydes, ketones and ethers. A multi-bed, Peltier-cooled adsorbent trap, consisting of Carboxen 1000 and Carbopack B, was used to acquire one sample per hour. Upon injection the sample was split in an approximately 50 : 50 ratio between a 50 m aluminium oxide (Al2O3) porous layer open tubular (PLOT) column and a 10 m LOWOX column. Eluents from each column were then analysed using flame ionisation detection (FID). Regular calibration of the system was performed using a standard cylinder mixture at the parts per billion by volume (ppbV) level for non-methane hydrocarbons (NMHCs) and a permeation tube method for the oxygenated species. The system is fully automated with NMHC detection limits between 1 and 10 parts per trillion by volume (pptV) and o-VOC detection limits between 10 and 40 pptV.

A study of peroxy radicals and ozone photochemistry at coastal sites in the northern and southe A study of peroxy radicals and ozone photochemistry at coastal sites in the northern and southe

Date added: 08/06/1997
Date modified: 07/27/2009
Filesize: 1.01 MB

Carpenter, L. J., P. S. Monks, B. J. Bandy, S. A. Penkett, I. E. Galbally, and C. P. (. Meyer (1997), A study of peroxy radicals and ozone photochemistry at coastal sites in the northern and southern hemispheres, J. Geophys. Res., 102(D21), 25,417–25,427.


Abstract


Peroxy radicals and other important species relevant to ozone photochemistry, including ozone, its photolysis rate coefficient jO(1 D), NOx (NO + NO2), and peroxides, were measured at the coastal sites of Cape Grim, Tasmania, in January/February 1995 during the Southern Ocean Atmospheric Photochemistry Experiment (SOAPEX 1) and Mace Head, Western Ireland, in May 1995 during the Atlantic Atmospheric Photochemistry Experiment (ATAPEX 1). At both sites it was observed that the relationship between peroxy radical (HO2 + RO2) concentrations and jO(1 D) switched from a square root dependence in clean oceanic or “baseline” air to a first-order dependence in more polluted air. Simple algorithms derived from a photochemical reaction scheme indicate that this switch-over occurs when atmospheric NO levels are sufficient for peroxy radical reaction with NO to compete with radical recombination reactions. At this crucial point, net tropospheric ozone production is expected to occur and was observed in the ozone diurnal cycles when the peroxy radical/jO(1 D) dependencies became first order. The peroxy radical/jO(1 D) relationships imply that ozone production exceeds destruction at NO levels of 55±30 parts per trillion by volume (pptv) at Mace Head during late spring and 23±20 pptv at Cape Grim during summer, suggesting that the tropospheric ozone production potential of the southern hemisphere is more responsive to the availability of NO than that of the northern hemisphere.

 

A Statistical Analysis of North East Atlantic (submicron) Aerosol Size Distributions A Statistical Analysis of North East Atlantic (submicron) Aerosol Size Distributions

Date added: 03/19/2013
Date modified: 03/19/2013
Filesize: 516.78 kB

Dall’Osto, M., C. Monahan, R. Greaney, D.C.S. Beddows, R. M. Harrison, D. Ceburnis and C. D. O’Dowd. A Statistical Analysis of North East Atlantic (submicron) Aerosol Size Distributions., Atmos. Chem. Phys., 11, 12567–12578, 2011, doi:10.5194/acp-11-12567-2011.


Abstract. The Global Atmosphere Watch research station at Mace Head (Ireland) offers the possibility to sample some of the cleanest air masses being imported into Europe as well as some of the most polluted being exported out of Europe. We present a statistical cluster analysis of the physical characteristics of aerosol size distributions in air ranging from the cleanest to the most polluted for the year 2008. Data coverage achieved was 75% throughout the year. By applying the Hartigan-Wong k-Means method, 12 clusters were identified as systematically occurring. These 12 clusters could be further combined into 4 categories with similar characteristics, namely: coastal nucleation category (occurring 21.3% of the time), open ocean nucleation category (occurring 32.6% of the time), background clean marine category (occurring 26.1% of the time) and anthropogenic category (occurring 20% of the time) aerosol size distributions. The coastal nucleation category is characterised by a clear and dominant nucleation mode at sizes less than 10 nm while the open ocean nucleation category is characterised by a dominant Aitken mode between 15 nm and 50 nm. The background clean marine aerosol exhibited a clear bimodality in the sub-micron size distribution, with although it should be noted that either the Aitken mode or the accumulation mode may dominate the number concentration. However, peculiar background clean marine size distributions with coarser accumulation modes are also observed during winter months. By contrast, the continentally-influenced size distributions are generally more monomodal (accumulation), albeit with traces of bimodality. The open ocean category occurs more often during May, June and July, corresponding with the North East (NE) Atlantic high biological period. Combined with the relatively high percentage frequency of occurrence (32.6 %), this suggests that the marine biota is an important source of new nano aerosol particles in NE Atlantic Air.

 

A Photoelectric Condensation Nucleus Counter On High Precision A Photoelectric Condensation Nucleus Counter On High Precision

Date added: 08/07/1955
Date modified: 07/13/2009
Filesize: 4.73 MB
L.w Pollak & Tc O'Connor, A Photoelectric Condensation Nucleus Counter On High Precision, Geofisica Pura E Applicata Milano Vol. 32 pp 139-146

Abstract

 

A new model of the direct beam photo-electrix condensation nucleus counter and itsproperties are described. the main feature of the construction is the reduction of the fog tube diameter which resulted in the elimination of all uncertainties in the measurement of the light intensity after the fog is formed by adiabatic expansion.- Individual measurements with two identical of this design which incorporate all previous improvements, agree to better than 5% in 70% in all cases, their aver absolute difference being 2%. Deviations of more than one division of meter reading (or 10% of concentration) were not observed, This agreement is maintained over long periods. - A calibration curve of the latest model of the photo-electric nucleus counter is given

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

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

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


Abstract


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

 

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

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

Abstract


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

A method of measurement of the Dielectric Constant of some liquids A method of measurement of the Dielectric Constant of some liquids

Date added: 01/01/1977
Date modified: 08/06/2009
Filesize: 1.3 MB

Jennings S.G., A method of measurement of the dielectric constant of some liquids. Phys. Educ. Vol 12, January 1977. pp. 40-42.


Abstract


The method depends on the existence of a driving force on a liquid dielectric in an electric field. The force leads to a rise in the liquid level between the plates of a capacitor. The capacitor plates were placed just above a reservoir of the dielectric liquid, the level of which was monitored by a travelling microscope. The rise in liquid level (h) was measured for selected values of voltage (v) until sparking between the plates occurred. A plot of h against V2 was obtained, and the dielectric constant was determined from the slope of the graph.

A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE

Date added: 01/01/2000
Date modified: 07/27/2009
Filesize: 4.55 MB
Prinn, R. G., et al. (2000), A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE, J. Geophys. Res., 105(D14), 17,751–17,792.

Abstract


We describe in detail the instrumentation and calibrations used in the Atmospheric Lifetime Experiment (ALE), the Global Atmospheric Gases Experiment (GAGE), and the Advanced Global Atmospheric Gases Experiment (AGAGE) and present a history of the majority of the anthropogenic ozone-depleting and climate-forcing gases in air based on these experiments. Beginning in 1978, these three successive automated high-frequency in situ experiments have documented the long-term behavior of the measured concentrations of these gases over the past 20 years, and show both the evolution of latitudinal gradients and the high-frequency variability due to sources and circulation. We provide estimates of the long-term trends in total chlorine contained in long-lived halocarbons involved in ozone depletion. We summarize interpretations of these measurements using inverse methods to determine trace gas lifetimes and emissions. Finally, we provide a combined observational and modeled reconstruction of the evolution of chlorocarbons by latitude in the atmosphere over the past 60 years which can be used as boundary conditions for interpreting trapped air in glaciers and oceanic measurements of chlorocarbon tracers of the deep oceanic circulation. Some specific conclusions are as follows: (1) International compliance with the Montreal Protocol is so far resulting in chlorofluorocarbon and chlorocarbon mole fractions comparable to target levels; (2) mole fractions of total chlorine contained in long-lived halocarbons (CCl2F2, CCl3F, CH3CCl3, CCl4, CHClF2, CCl2FCClF2, CH3Cl, CH2Cl2, CHCl3, CCl2=CCl2) in the lower troposphere reached maximum values of about 3.6 ppb in 1993 and are beginning to slowly decrease in the global lower atmosphere; (3) the chlorofluorocarbons have atmospheric lifetimes consistent with destruction in the stratosphere being their principal removal mechanism; (4) multiannual variations in chlorofluorocarbon and chlorocarbon emissions deduced from ALE/GAGE/AGAGE data are consistent approximately with variations estimated independently from industrial production and sales data where available (CCl2F2 (CFC-12) and CCl2FCClF2 (CFC-113) show the greatest discrepancies); (5) the mole fractions of the hydrochlorofluorocarbons and hydrofluorocarbons, which are replacing the regulated halocarbons, are rising very rapidly in the atmosphere, but with the exception of the much longer manufactured CHClF2 (HCFC-22), they are not yet at levels sufficient to contribute significantly to atmospheric chlorine loading. These replacement species could in the future provide independent estimates of the global weighted-average OH concentration provided their industrial emissions are accurately documented; (6) in the future, analysis of pollution events measured using high-frequency in situ measurements of chlorofluorocarbons and their replacements may enable emission estimates at the regional level, which, together with industrial end-use data, are of sufficient accuracy to be capable of identifying regional noncompliance with the Montreal Protocol.

A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE

Date added: 01/01/2000
Date modified: 07/23/2009
Filesize: 4.55 MB
Prinn, R. G., et al. (2000), A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE, J. Geophys. Res., 105(D14), 17,751–17,792.

Abstract


We describe in detail the instrumentation and calibrations used in the Atmospheric Lifetime Experiment (ALE), the Global Atmospheric Gases Experiment (GAGE), and the Advanced Global Atmospheric Gases Experiment (AGAGE) and present a history of the majority of the anthropogenic ozone-depleting and climate-forcing gases in air based on these experiments. Beginning in 1978, these three successive automated high-frequency in situ experiments have documented the long-term behavior of the measured concentrations of these gases over the past 20 years, and show both the evolution of latitudinal gradients and the high-frequency variability due to sources and circulation. We provide estimates of the long-term trends in total chlorine contained in long-lived halocarbons involved in ozone depletion. We summarize interpretations of these measurements using inverse methods to determine trace gas lifetimes and emissions. Finally, we provide a combined observational and modeled reconstruction of the evolution of chlorocarbons by latitude in the atmosphere over the past 60 years which can be used as boundary conditions for interpreting trapped air in glaciers and oceanic measurements of chlorocarbon tracers of the deep oceanic circulation. Some specific conclusions are as follows: (1) International compliance with the Montreal Protocol is so far resulting in chlorofluorocarbon and chlorocarbon mole fractions comparable to target levels; (2) mole fractions of total chlorine contained in long-lived halocarbons (CCl2F2, CCl3F, CH3CCl3, CCl4, CHClF2, CCl2FCClF2, CH3Cl, CH2Cl2, CHCl3, CCl2=CCl2) in the lower troposphere reached maximum values of about 3.6 ppb in 1993 and are beginning to slowly decrease in the global lower atmosphere; (3) the chlorofluorocarbons have atmospheric lifetimes consistent with destruction in the stratosphere being their principal removal mechanism; (4) multiannual variations in chlorofluorocarbon and chlorocarbon emissions deduced from ALE/GAGE/AGAGE data are consistent approximately with variations estimated independently from industrial production and sales data where available (CCl2F2 (CFC-12) and CCl2FCClF2 (CFC-113) show the greatest discrepancies); (5) the mole fractions of the hydrochlorofluorocarbons and hydrofluorocarbons, which are replacing the regulated halocarbons, are rising very rapidly in the atmosphere, but with the exception of the much longer manufactured CHClF2 (HCFC-22), they are not yet at levels sufficient to contribute significantly to atmospheric chlorine loading. These replacement species could in the future provide independent estimates of the global weighted-average OH concentration provided their industrial emissions are accurately documented; (6) in the future, analysis of pollution events measured using high-frequency in situ measurements of chlorofluorocarbons and their replacements may enable emission estimates at the regional level, which, together with industrial end-use data, are of sufficient accuracy to be capable of identifying regional noncompliance with the Montreal Protocol.

«StartPrev12345678910NextEnd»
Page 10 of 11
Copyright © 2017 Atmospheric Physics Research Cluster. All Rights Reserved.
Joomla! is Free Software released under the GNU/GPL License.
 
None