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Journal Publications

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

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Documents

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Long-term measurements of the concentrations of halocarbons in an urban area of Kraków, Poland Long-term measurements of the concentrations of halocarbons in an urban area of Kraków, Poland

Date added: 08/07/2003
Date modified: 07/24/2009
Filesize: 210.57 kB

Lasa J., Śliwka I. Long.term measurements of the concentrations of halocarbons in an urban area of Kraków, Poland. Applied Energy, 75 (2003), 155-163.


Abstract


The results of the measurements of the concentrations of freons (F-11 and F-113), chloroform (CHCl3), trichloroethane (CH3CCl3) and carbon tetrachloride (CCl4) in air are presented. The data concern concentration measurements that have been conducted in Krakow since half way through 1997 to the end of 1999. The mean monthly values of these concentrations have been compared with the data from Mace Head, the station situated at a similar longitude as Krakow. It has been concluded that, in the observed period of time, the concentrations of the pollutants in Krakow are higher than in Mace Head. The mean monthly concentrations of F-11 and CCl4 decrease in Krakow faster than in Mace Head (2.5 and 3.3 times, respectively). The concentrations of CHCl3 and CH3CCl3 decrease at both locations, but the change is greater in Krakow. In Krakow, the observed increase of F-113 is 0.13 ppt/month and has an opposite trend than in the same period at Mace Head.

Long-term measurements of atmospheric mercury at Mace Head, Irish west coast, between 1995 and Long-term measurements of atmospheric mercury at Mace Head, Irish west coast, between 1995 and

Date added: 08/07/2002
Date modified: 07/24/2009
Filesize: 236.55 kB

Long-term measurements of atmospheric mercury at Mace Head, Irish west coast, between 1995 and 2001 R. Ebinghaus, H.H. Kock, A.M. Coggins, T.G. Spain, S.G. Jennings, C. Temme Atmos. Environ., 36, 5267-5276, 2002


Abstract


Monitoring of atmospheric mercury concentrations has been carried out at the Mace Head atmospheric research station on the west coast of Ireland between September 1995 and December 2001. Measurements were carried out with a time resolution of 15 min. No trend in the concentration levels has been detected during the measurement period, with the annual average concentrations remaining constant at 1.75 ng m−3. A slight increase in the concentration levels is derived, if only clean sector filtered air masses clearly of marine origin are used.

The Mace Head data set shows a seasonal pattern with higher monthly mean concentrations in the winter months. Comparison with two continental sites in Sweden shows, that atmospheric mercury concentrations at the western inflow boundary are on an average higher than those at the two continental sites, expressing a west to east decreasing concentration gradient.

At Mace Head, no indications for so-called Mercury Depletion Events (MDEs), recently reported for a number of sites in the Arctic and in the Antarctic, have been found between 1995 and 2001.

 

Long-term changes in tropospheric ozone Long-term changes in tropospheric ozone

Date added: 08/07/2006
Date modified: 07/24/2009
Filesize: 849.93 kB

Oltmans, S. J., et al. (2006), Long-term changes in tropospheric ozone, Atmos. Environ.,
40, 3156-3173


Abstract

In this review we attempt to critically evaluate the availability of reliable tropospheric ozone measurements suitable for long-term trend analysis. The focus is on large-scale changes deduced from measurements, which are used for comparison with numerical simulations of the tropospheric ozone cycle. These are required to quantify the influence of anthropogenic ozone precursor emission changes on climate. Long-term tropospheric ozone measurements show that ozone over Europe has increased by more than a factor of two between World War II and the early 1990s which is consistent with the large increase in anthropogenic ozone precursor emissions in the industrialized world. However, the further increase in background ozone over Europe and North America since the early 1990s cannot be solely explained by regional ozone precursor changes because anthropogenic ozone precursor emissions decreased in the industrialized countries as consequence of air pollution legislation. Measurements also indicate large increases in ozone in the planetary boundary layer over the tropical Atlantic since the late 1970s, which have been attributed to large increases in fossil fuel related emissions. Measurements at southern midlatitudes, which are limited in number, show a moderate increase in tropospheric ozone since the middle of the 1990s.

 

Local and regional air pollution in Ireland during an intensive aerosol measurement campaign Local and regional air pollution in Ireland during an intensive aerosol measurement campaign

Date added: 08/01/2006
Date modified: 07/02/2009
Filesize: 1.1 MB

Ceburnis, D., J. Yin, A.G. Allen, S.G. Jennings, R.M. Harrison, E. Wright, M. Fitzpatrick, T. Healy, and E. Barry, Local and regional air pollution in Ireland during an intensive aerosol measurement campaign, J. Environ. Monitoring, 8, 479-487, 2006.


Abstract

 

An intensive two month measurement campaign has been performed during a two year study of major component composition of urban PM10 and PM2.5 in Ireland (J. Yin, A. G. Allen, R. M. Harrison, S. G. Jennings, E. Wright, M. Fitzpatrick, T. Healy, E. Barry, D. Ceburnis and D. McCusker, Atmos. Res., 2005, 78(3–4), 149–165). Measurements included size-segregated mass, soluble ions, elemental carbon (EC) distributions, fine and coarse fraction organic carbon (OC) and major gases along with standard meteorological measurements. The study revealed that urban emissions in Ireland had mainly a local character and therefore were confined within a limited area of 20–30 km radius, without significantly affecting regional air quality. Gaseous measurements have shown that urban emissions in Ireland had clear, but fairly limited influence on the regional air quality due to favorable mixing conditions at higher wind speeds, in particular from the western sector. Size-segregated mass and chemical measurements revealed a clear demarcation size between accumulation and coarse modes at about 0.8 µm which was constant at all sites. Carbonaceous compounds at the urban site accounted for up to 90% of the particle mass in a size range of 0.066–0.61 µm. Nss SO42– concentrations in PM2.5 were only slightly higher at the urban site compared to the rural or coastal sites, while NO3 and NH4+ concentrations were similar at the urban and coastal sites, but were a factor of 2 to 3 higher than at the rural site. OC was highly variable between the sites and revealed clear seasonal differences. Natural or biogenic OC component accounted for <10% in winter and up to 30% in summer of the PM2.5 OC at urban sites. A contribution of biogenic OC component to PM2.5 OC mass at rural site was dominant.

Light scattering properties of sea-salt aerosol particle inferred from modeling studies and ground-b Light scattering properties of sea-salt aerosol particle inferred from modeling studies and ground-b

Date added: 09/22/2006
Date modified: 07/13/2009
Filesize: 689.42 kB

Chamaillard, K., Kleefeld, C., Jennings, S.G., Ceburnis, D. & O’Dowd, C.D., Light scattering properties of sea-salt aerosol particle inferred from modeling studies and ground-based measurements. Journal of Quantitative Spectroscopy & Radiative Transfer, vol 101, pp. 498-511, 2006.


Abstract

 

Direct climate radiative forcing depends on the aerosol optical depth t, the single scattering albedo $, and the up-scatter
fraction b; these quantities are functions of the refractive index of the particles, their size relative to the incident
wavelength, and their shape. Sea-salt aerosols crystallize into cubic shapes or in agglomerates of cubic particles under low relative humidity conditions. The present study investigates the effects of the shape of dried sea-salt particles on the
detection of light scattering from the particles. Ground-based measurements of scattering and backscattering coefficients have been performed with an integrating nephelometer instrument for a wavelength l ¼ 0:55 mm. The measurements are compared to two models: the Mie theory assuming a spherical shape for the particles and the Discrete Dipole Approximation (DDA) model for the hypothesis of cubic shape of the sea-salt aerosols. The comparison is made accurately by taking into account the actual range of the scattering angles measured by the nephelometer in both models that is from 71 to 1701 for the scattering coefficient and from 901 to 1701 for the backscattering coefficient. Modeled scattering and backscattering coefficients increase for nonspherical particles compared to spherical shape of particles with diameter larger than about 1 mm. However, the comparison of the modeling results with the measurements gives best agreement for particles diameter less than about 1 mm. The size distribution of the particles is measured with two instruments with different size bins: an electrical low-pressure impactor (ELPI) and an aerodynamic particle sizer (APS). It is found that the size of the bins of the instruments to determine the number concentration of the particles in accordance with their diameter is critical in the comparison of measurements with modeling.

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

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

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


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

Light backscattering and scattering by non-spherical sea-salt aerosols Light backscattering and scattering by non-spherical sea-salt aerosols

Date added: 08/01/2003
Date modified: 07/24/2009
Filesize: 483.03 kB

Chamaillard K., Jennings S.J., Kleefeld C., Ceburnis D. and Yoon Y.J. Light backscattering and scattering by non-spherical sea-salt aerosols. J. of Quantitative Spectroscopy & Radiative Transfer, Vol. 79-80, 577-597, 2003.


Abstract


The scattering coefficient, single-scatter albedo, and up-scatter fraction are key parameters in direct climate forcing by aerosols. Usually the contribution of sea-salt is estimated using Mie theory, assuming that these particles are spherical. The optical properties of particles are known to strongly depend on the shape of the particles. The question of the applicability of using Mie theory in recent studies is mainly devoted to nonspherical dust-like tropospheric aerosols. In this study, we attempt to quantify the relative contribution of nonspherical sea-salt to measured scattering and backscattering coefficients. The shape of nonspherical sea-salt is assumed to be cubic. The discrete dipole approximation model is applied to estimate the optical properties of the nonspherical particles. Measurements are then compared to Mie theory calculations and to DDA cubic calculations. The results are presented for two wavelengths: λ=0.55 μm and 0.7 μm, It is found that the size of particles responsible for scattering is larger than 0.3 μm. The backscattering coefficient, unlike the scattering coefficient, is very sensitive to particle shape. Cubic particles give better agreement to the measurements. Compared to spherical particles, the cubic approach underestimates the backscattering coefficient in contrast to prolate spheroidal calculations.

Lifetime and emission estimates of 1,1,2-trichlorotrifluorethane (CFC-113) from daily global background observations June 1982–June 1994 Lifetime and emission estimates of 1,1,2-trichlorotrifluorethane (CFC-113) from daily global background observations June 1982–June 1994

Date added: 08/01/1996
Date modified: 07/24/2009
Filesize: 1.48 MB
Fraser, P., D. Cunnold, F. Alyea, R. Weiss, R. Prinn, P. Simmonds, B. Miller, and R. Langenfelds (1996), Lifetime and emission estimates of 1,1,2-trichlorotrifluorethane (CFC-113) from daily global background observations June 1982–June 1994, J. Geophys. Res., 101(D7), 12,585–12,599.

Abstract


Observations every two hours of CCl2FCClF2 at Mace Head, Ireland (February 1987–June 1994); Cape Meares, Oregon (April 1984–June 1989); Ragged Point, Barbados (October 1985–June 1994); Cape Matatula, Samoa (October 1985–June 1989 and January 1992–June 1994); and Cape Grim, Tasmania (June 1982–June 1994) are reported. The observations from Cape Grim have been extended back to 1978 using archived air samples. The global atmospheric abundance of CCl2FCClF2 is indicated to have been growing exponentially between 1978 and 1987 with an e-folding time of approximately 7.6 years; it has been growing less rapidly since that time. On January 1, 1994, the mean inferred northern hemispheric mixing ratio in the lower troposphere was 84.4 ± 0.4 ppt and the southern hemispheric value was 80.6 ± 0.4 ppt; the global growth rate in 1991–1993 is estimated to have averaged approximately 3.1 ± 0.1 ppt/year. The differences between the northern and southern hemispheric concentrations are calculated to be consistent with the almost entirely northern hemispheric release of this gas. The annual release estimates of CCl2FCClF2 by industry, which include estimates of eastern European emissions, fairly consistently exceed those deduced from the measurements by approximately 10% from 1980 to 1993. The uncertainties in each estimate is approximately 5%. This difference suggests that up to 10% of past production might not yet have been released. The measurements indicate that atmospheric releases of CCl2FCClF2 have been decreasing rapidly since 1989 and in 1993 amounted to 78 ± 27 × 106 kg or 42 ± 15% of the 1985–1987 emissions.

LIDAR studies of the atmospheric boundary layer and locally generated sea spray aerosol plumes at Ma LIDAR studies of the atmospheric boundary layer and locally generated sea spray aerosol plumes at Ma

Date added: 07/31/2002
Date modified: 07/02/2009
Filesize: 798.06 kB
Gerard Kunz, Gerrit de Leeuw, Colin O'Dowd, Edo Becker.LIDAR studies of the atmospheric boundary layer and locally generated sea spray aerosol plumes at Mace Head. J. Geophys. Res., 107, 10.1029/2001JD001240, 2002.

Abstract

 

A scanning backscatter lidar was used to measure the depth and structure of the coastal atmospheric boundary layer and the evolution of primary aerosol (sea spray) plumes produced by breaking waves during the New Particle Formation and Fate in the Coastal Environment (PARFORCE) campaign at the Mace Head Atmospheric Research Station (Ireland) in September 1998 and in June 1999. The PBL structure was observed to vary from a single-layer well-mixed structure to multilayered structures. Comparison with in situ aircraft measurements of temperature and humidity exhibited good agreement. Using the lidar in the scanning mode allowed two-dimensional profiling over a spatial scale of 10 km, revealing significant primary aerosol plumes produced by breaking waves, particularly in the surf zone and at high wind speeds on the open sea. The initial plume heights were some tens of meters and evolved to hundreds of meters while transported over only a few kilometers from the source. The plumes were traceable to distances of more than 10 km down wind from the source.

Lidar observations of atmospheric boundary layer structure....Ireland (PARFORCE experiment) Lidar observations of atmospheric boundary layer structure....Ireland (PARFORCE experiment)

Date added: 08/06/2002
Date modified: 07/02/2009
Filesize: 798.06 kB
Kunz, G. J., G. de Leeuw, E. Becker, and C. D. O'Dowd (2002), Lidar observations of atmospheric boundary layer structure and sea spray aerosol plumes generation and transport at Mace Head, Ireland (PARFORCE experiment), J. Geophys. Res., 107(D19), 8106, doi:10.1029/2001JD001240.

Abstract


A scanning backscatter lidar was used to measure the depth and structure of the coastal atmospheric boundary layer and the evolution of primary aerosol (sea spray) plumes produced by breaking waves during the New Particle Formation and Fate in the Coastal Environment (PARFORCE) campaign at the Mace Head Atmospheric Research Station (Ireland) in September 1998 and in June 1999. The PBL structure was observed to vary from a single-layer well-mixed structure to multilayered structures. Comparison with in situ aircraft measurements of temperature and humidity exhibited good agreement. Using the lidar in the scanning mode allowed two-dimensional profiling over a spatial scale of 10 km, revealing significant primary aerosol plumes produced by breaking waves, particularly in the surf zone and at high wind speeds on the open sea. The initial plume heights were some tens of meters and evolved to hundreds of meters while transported over only a few kilometers from the source. The plumes were traceable to distances of more than 10 km down wind from the source.

Large Electric fields due to industrial chimney stack plumes Large Electric fields due to industrial chimney stack plumes

Date added: 07/30/1977
Date modified: 07/23/2009
Filesize: 2.08 MB

Jones, C.D., and Jennings, S.G. (1977).- Large electric fields due to industrial chimney stack plumes. Atmos. Environ.,11, 1197-1207.


Abstract


Large values of electric field due to a charged plume from an industrial chimney stack have been observed. Downwind and crosswind profiles of the electric field were measured using 4 field mills. Average values of between 5 and 6 kV m−1 over 10 minute periods were measured at distances within 200 m of the stack. Electric field values as large as 3.5 kV m−1 were present at a distance of 3 km from the stack. It was found that the electric field did not return to its normal fair-weather value until the downwind distance from the stack had exceeded 9 km.

The decrease in the average value of the electric field, Ep, under the plume gave good agreement with an equation derived from line charge theory, modified by an empirical decay factor exp(−R/D)

.[1+Image ] where λ is the charge per unit length, h the plume height, R the distance of the position P downwind, and D the distance at which λ is reduced by Image . The experimental results yielded a value for D of about 1.5 km.

 

Point discharge currents as large as 3 μA were measured at a distance of 700 m from the stack. Measurements at heights ranging from 9.25 m to 3.25 m agreed with the theoretical relation i = k(E-E0) where E is the measured value of electric field at a distance 10 m upwind from the discharge point, E0 the critical value of electric field above which point discharge will occur and k is a constant. Values of E0 of about 2kV m−1 were found for the two highest points.

The results suggest that electric field measurements may be a valuable supplement to concentration data in atmospheric diffusion experiments using charged plumes.

Isotope values of atmospheric halocarbons and hydrocarbons from Irish urban, rural, and marine Isotope values of atmospheric halocarbons and hydrocarbons from Irish urban, rural, and marine

Date added: 08/06/2007
Date modified: 07/24/2009
Filesize: 750 kB

Redeker, K. R., S. Davis, and R. M. Kalin (2007), Isotope values of atmospheric halocarbons and hydrocarbons from Irish urban, rural, and marine locations, J. Geophys. Res., 112, D16307, doi:10.1029/2006JD007784.


Abstract

 

Stable carbon isotope ratios for 37 hydrocarbon, CFC and halocarbon compounds were determined over the course of 1 year (86 samples) from the urban Belfast environment, Northern Ireland (NI). A smaller number of samples were collected from rural locations at Crossgar and Hillsborough, NI, and one marine location at Mace Head, Republic of Ireland. Source δ 13C “signatures” suggest that <C5 alkanes are most likely derived from natural gas and liquid petroleum gas while >C5 alkanes and ≥C4 alkenes are most likely derived from vehicle emissions. C3–C5 hydrocarbons show significant enrichment of δ 13C with iso-alkanes < n-alkanes < alkenes < alkynes. There is also significant enrichment of δ 13C from propane to n-butane to n-pentane. There is no significant separation between n-pentane, n-hexane, n-heptane or methyl-butane, methyl pentane and methyl hexanes. Calculated hydroxyl reaction kinetic isotope effects and subsequent δ 13C enrichment are insufficient to explain shifts in isotopic ratio relative to concentration for all compounds as is differences in origin of air mass. Very few compounds show significant diurnal shifts; however, alkanes and ≥C4 alkenes demonstrate consistent enrichment of isotopic ratios when summer samples are compared to winter samples. Benzene is the sole compound measured that appears to become more depleted in δ 13C when summer samples are compared against winter samples. Urban air, sampled at Belfast, which has originated in Europe shows enriched values for hydrocarbons while air which has originated in the Arctic Ocean is most similar to marine air off the Atlantic, sampled at Mace Head, Ireland.

 

Isoprene and other non-methane hydrocarbons from seaweeds a source of reactive hydrocarbons to Isoprene and other non-methane hydrocarbons from seaweeds a source of reactive hydrocarbons to

Date added: 08/07/2004
Date modified: 07/24/2009
Filesize: 287.26 kB

BROADGATE, W.J., MALIN, G., KÜPPER, F.C., THOMPSON, A. & LISS, P.S. 2004. Isoprene and other non-methane hydrocarbons from seaweeds: a source of reactive hydrocarbons to the atmosphere. Marine Chemistry 88(1-2): 61-73. doi:10.1016/j.marchem.2004.02.002.


Abstract

 

Non-methane hydrocarbons (NMHCs) are produced naturally in the ocean and by terrestrial vegetation. Owing to its high reactivity and flux, isoprene (2-methyl-1,3-butadiene) is important in controlling the balance of atmospheric oxidants, and altering air quality on both local and global scales. Here we show, for the first time, that macroalgae (seaweeds) emit isoprene and a number of other non-methane hydrocarbons (NMHCs). We observed NMHC concentrations in rockpools containing macroalgae and estimated fluxes to the atmosphere over a full diurnal cycle. Emissions at our temperate coastal site (Mace Head, Ireland) in autumn are intermediate in magnitude between terrestrial and ocean fluxes (on a unit area basis), and may contribute significant concentrations to the local atmosphere. We also carried out a series of controlled laboratory experiments focusing on isoprene, in natural and artificial light, and under different temperature conditions involving red (Chondrus crispus, Asparagopsis armata), green (Ulva intestinalis, formerly known as Enteromorpha intestinalis) and brown (Laminaria digitata, Ascophyllum nodosum, Pelvetia canaliculata, Fucus vesiculosus, Fucus serratus, Halidrys siliquosa and Laminaria saccharina) macroalgae commonly found on the west coast of Ireland. We observed NMHC emissions from all the algae investigated and emissions were dominated by alkenes. Production is species-dependent, temperature-dependent and related to light availability. We discuss our observations in the context of what is known about the production of isoprene and ethene in higher plants.

 

Isentropic airflow probability analysis Isentropic airflow probability analysis

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

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


Abstract

 

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

 

IOP  John A McClelland IOP John A McClelland

Date added: 08/07/2002
Date modified: 08/07/2008
Filesize: 3.28 MB
 pg 176 - 185 by Tom O Connor

Ionization equilibrium in aerosols Ionization equilibrium in aerosols

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

Abstract


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

Ionization Equibrium of maritime Air Ionization Equibrium of maritime Air

Date added: 08/07/1960
Date modified: 07/24/2009
Filesize: 5.83 MB
O'Connor, T.C, Sharkey, W.P, Ionization Equilibrium In Maritime Air, Procedding of the Royal irish Academy, Volume 61, Section A, No. 3
Abstract

Iodine Oxide Homogeneous Nucleation An Explanation for Coastal New Particle Production Iodine Oxide Homogeneous Nucleation An Explanation for Coastal New Particle Production

Date added: 07/31/2001
Date modified: 07/24/2009
Filesize: 423.83 kB

Hoffmann, T, CD O'Dowd, JH Seinfeld, Iodine oxides and new particle formation, Geophys. Res. Letts., 27, 1949-1952, 2001.


Abstract


A series of laboratory experiments on the chemical composition of aerosol particles formed after photodissociation of CH2I2, a major volatile alkyl halide released from macroalgae, have been performed in a laboratory scale reaction chamber using on-line atmospheric pressure chemical ionization mass spectrometry (APCI/MS). Based on the mass spectrometric results and the molecular properties of iodine oxides, we suggest that the self-nucleation of iodine oxides provides an efficient source of natural condensable material in coastal environments and discuss this concept focusing on OIO as one potential key species for new particle formation. The presented hypothesis not only fits the measured enrichment of iodine species in submicrometer particles, but also can explain the frequently observed nucleation bursts in the coastal boundary layer.

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

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

Abstract

 

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

Investigating organic aerosol loading in the remote marine environment Investigating organic aerosol loading in the remote marine environment

Date added: 09/01/2011
Date modified: 11/17/2011
Filesize: 2.42 MB

Lapina, K., C.L. Heald, D.V. Spracklen, S.R. Arnold, J.D. Allan, H Coe, G. McFiggans, S.R. Zorn, F. Drewnick, T.S. Bates, L.N. Hawkins, L.M. Russell, A. Smirnov, C. O'Dowd and A.J. Hind. Investigating organic aerosol loading in the remote marine environment, Atmos. Chem. Phys., 11, 8847–8860, 2011, doi:10.5194/acp-11-8847-2011.

 

  

Abstract: Aerosol loading in the marine environment is investigated using aerosol composition

measurements from several research ship campaigns (ICEALOT, MAP, RHaMBLe, VOCALS

and OOMPH), observations of total AOD column from satellite (MODIS) and ship-based instruments (Maritime Aerosol Network, MAN), and a global chemical transport model (GEOS-Chem). This work represents the most comprehensive evaluation of oceanic OM emission inventories to date, by employing aerosol composition measurements obtained from campaigns with wide spatial and temporal coverage. The model

underestimates AOD over the remote oceans on average by 0.02 (21 %), compared to satellite observations, but provides an unbiased simulation of ground-based Maritime Aerosol Network (MAN) observations. Comparison with cruise data demonstrates that the GEOS-Chem simulation of marine sulfate, with the mean observed values ranging between 0.22 μgm−3 and 1.34 μgm−3, is generally unbiased, however surface organic matter (OM) concentrations, with the mean observed concentrations between 0.07 μgm−3 and 0.77 μgm−3, are underestimated by a factor of 2-5 for the standard model run. Addition of a a sub-micron marine OM source of approximately 9 TgCyr−1 brings the model into agreement with the ship-based measurements, however this additional OM source does not explain the model underestimate of marine AOD. The model underestimate of marine AOD is therefore likely the result of a combination of satellite retrieval bias and a missing marine aerosol source (which exhibits a different spatial pattern than existing aerosol in the model).

  


Interpretation of roadside PM10 monitoring data from Sunderland, United Kingdom Interpretation of roadside PM10 monitoring data from Sunderland, United Kingdom

Date added: 09/22/2003
Date modified: 07/23/2009
Filesize: 739.63 kB

Price, M., Dowd, C., & Dixon, M. (2003). Interpretation of roadside PM10 monitoring data from Sunderland, United Kingdom. Environmental Monitoring and Assessment, 82, 225-241


Abstract


Roadside PM10 has been monitored by Partisol® at three sites in Sunderland between August 1997 and February 1998. The sites chosen were an inner city kerbside site; a roadside site adjacent to a dual carriageway on the outskirts of Sunderland with an open aspect; and a rural site. The results indicate that there is a seasonal variation in the relationship between the sites in terms of monitored PM10. In the winter there is a poor correlation between the sites whereas in the summer significant correlations are obtained. Of the sites monitored PM10 is consistently highest at the inner city roadside site. During the summer, exceedances of the U.K. 50 μg m-3 standard (DETR, 2000) are associated with conditions suitable for the build-up of photochemical pollution however during the winter period exceedances are recorded during a variety of weather conditions. At the dual carriageway site PM2.5 has also been recorded and contributions to measured PM10 are 77% in summer and 68% in winter. The results illustrate a number of inconsistencies between this study utilising the Partisol® and others reporting results where PM10 has been monitored by TEOM®.

International field intercomparison measurements of atmospheric mercury species at Mace Head, Ireland International field intercomparison measurements of atmospheric mercury species at Mace Head, Ireland

Date added: 07/31/1999
Date modified: 07/24/2009
Filesize: 195.51 kB

Ebinghaus, R., Jennings, S.G., Schroeder, W.H., Berg, T., Donaghy., Guentzel, J., Kenny, C., Kock, H.H., Kvietkus, K., Landing, W., Munthe, J., Prestbo, E.M., Schneeberger, D., Slemr, F., Sommar, J., Urba, A., Wallschlager, D. & Xiao, Z. 1999. International field intercomparison measurements of atmospheric mercury species at Mace Head, Ireland. Atmos. Environ., 33, 3063-3073.


Abstract


Eleven laboratories from North America and Europe met at Mace Head, Ireland for the period 11-15 September 1995 for the first international field intercomparison of measurement techniques for atmospheric mercury species in ambient air and precipitation at a marine background location. Different manual methods for the sampling and analysis of total gaseous mercury (TGM) on gold and silver traps were compared with each other and with new automated analyzers. Additionally, particulate-phase mercury (Hgpart) in ambient air, total mercury, reactive mercury and methylmercury in precipitation were analyzed by some of the participating laboratories. Whereas measured concentrations of TGM and of total mercury in precipitation show good agreement between the participating laboratories, results for airborne particulate-phase mercury show much higher differences. Two laboratories measured inorganic oxidized gaseous mercury species (IOGM), and obtained levels in the low picogram m-3 range.

Intercomparison of number concentration measurements by various aerosol particle counters Intercomparison of number concentration measurements by various aerosol particle counters

Date added: 07/31/2002
Date modified: 07/02/2009
Filesize: 535.01 kB

Ankilov, A., A Baklanov, M. Colhoun, K-H. Enderle, J. Gras, Yu Jualanov, D. Kaller, A. Linder, A.A. Lushnikov, R. Mavliev, F. McGovern, A. Mirme, T.C. O'Connor, J. Podzimek, O. Prining, G.P. Reischl, R. Rudolf, G.J. Sem, W.W. Szymanski, E. Tamm, A.E. Vrtala, P.E. Wagner, W. Winklmayr and V. Zagaynov, Intercomparison of number concentration measurements by various aerosol particle counters. Atmos. Res. 62, 177-208, 2002.


Abstract

 

Total aerosol particle number concentrations, as measured by means of 16 different measurement systems, have been quantitatively compared during an international workshop at the Institute for Experimental Physics of the University of Vienna, Austria, which was coordinated within the Committee on Nucleation and Atmospheric Aerosols (ICCP-IUGG). The range of measuring instruments includes Pollak counters (PCO) in use already for several decades, presently available commercial particle counters, as well as laboratory prototypes. The operation of the instruments considered was based on different measurement principles: (1) adiabatic expansion condensation particle counter, (2) flow diffusion condensation particle counter, (3) turbulent mixing condensation particle counter, (4) laser optical particle counter, and (5) electrostatic particle measurement system. Well-defined test aerosols with various chemical compositions were considered: DEHS, sodium chloride, silver, hydrocarbons, and tungsten oxide. The test aerosols were nearly monodispersed with mean particle diameters between 4 and 520 nm, the particle number concentrations were varied over a range from about 4 × 101 to 7 × 106 cm-3. A few measurements were performed with two-component aerosol mixtures. For simultaneous concentration measurements, the various instruments considered were operated under steady state conditions in a linear flow system. A series of at least 10 single concentration measurements was performed by each individual instrument at each set of test aerosol parameters. The average of the concentration data measured by the various instruments was defined as a common reference. The number concentrations obtained from the various instruments typically agreed within a factor of about two over the entire concentration range considered. The agreement of the measured concentrations is notable considering the various different measurement principles applied in this study, and particularly in view of the broad range of measurement instruments used. Significant deviations and nonlinear response were observed only in a few cases and are possibly related to calibration errors. For certain conditions, a dependence of aerosol counter response on particle composition has been found. The scatter of the number concentrations obtained from each individual instrument during measurements with constant test aerosol typically did not exceed 20% to 25%. At concentrations below 103 cm-3, however, several of the instruments, including electrostatic particle measurement systems, tend to show increased experimental scatter.

Intercomparison of measurement methods for black carbon aerosols Intercomparison of measurement methods for black carbon aerosols

Date added: 08/01/1999
Date modified: 07/02/2009
Filesize: 201.1 kB

Hitzenberger, R., Jennings, S.G., Larson, S.M., Dillner, A., Cachier, H., Galambos, Z., Rouc, A. and Spain, T.G. (1999). Intercomparison of measurement methods for black carbon aerosols. Atmos. Environ., 33, 2823-2833.


Abstract


In this study, two method intercomparisons were performed. One thermal and two optical methods for the measurement of black carbon (BC) were applied to laboratory generated aerosols containing only BC. For the optical measurements, an aethalometer (Hansen et al., 1984. Science of Total Environment 36, 191-196) and an integrating sphere technique (Hitzenberger et al., 1996b. Journal of Geophysical Research 101, D14, 19&unknown;601-19&unknown;606) were used. The thermal method was described by Cachier et al. (1989a. Tellus 41B, 379-390). In an additional comparison, the integrating sphere was compared to a thermal optical technique (Birch and Cary, 1996. Aerosol Science Technology 25, 221-241) on ambient aerosol samples. The absorption coefficients were obtained from transmission measurements on filter samples for both the aethalometer and the integrating sphere. The BC mass concentration for the aethalometer was derived from this absorption measurement. The BC mass concentration for the integrating sphere, however, was obtained using an independent calibration curve. The agreement between the absorption coefficient sigmaa obtained for the BC test aerosol on parallel filters with the aethalometer and the integrating sphere was satisfactory. The slope of the regression lines depended on filter type. A comparison between BC mass concentrations, however, showed that the aethalometer values were only 23% of those obtained by the integrating sphere technique indicating that for pure BC aerosols, the standard aethalometer calibration should not be used. Compared to the thermal method, the integrating sphere gave an overestimation of the BC mass concentrations by 21%. For the ambient samples, the integrating sphere and the thermal optical methods for BC mass concentration determination showed agreement within 5% of the 1:1 line, although the data were not so well correlated.

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

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

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


Abstract


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

Intercomparison Of Formaldehyde Intercomparison Of Formaldehyde

Date added: 08/31/2003
Date modified: 07/23/2009
Filesize: 36.97 kB

T.J.Still , G.Mills, S. Al-Haider, P.W Seakins, P.Quincy, N.Martin , INTERCOMPARISON OF FORMALDEHYDE

Geophysical Research Abstracts, Vol. 6, 03925, 2004, SRef-ID: 1607-7962/gra/EGU04-A-03925 ,European Geosciences Union 2004


Abstract

 

Formaldehyde is one of the most abundant gas phase carbonyl compounds present in the troposphere, which is emitted directly, and produced from photo-oxidation of biogenic and anthropogenic volatile organic compounds. The subsequent removal process of formaldehyde generates substantial amounts of HO2 radicals, which ultimately result in formation of ozone. Consequently formaldehyde has a strong influence on the global mixing ratio of ozone and HOx radicals, which govern the oxidising capacity of the troposphere. An apparatus has been developed for the direct determination of ambient, atmospheric formaldehyde using gas chromatography with an argon doped, pulsed discharge helium ionization detector. Absolute values are obtained via calibration with a permeation source. The relatively high duty cycle (˜11 hr-1) allows measurements to be taken on timescales that are short compared to the atmospheric lifetime of formaldehyde. A detection limit of 42 pptv is calculated. This instrument was deployed to the West Coast of Ireland for the North Atlantic Marine Boundary Layer Experiment (NAMBLEX). Formaldehyde was also measured using an indirect fluorometric technique, and the results of the comparison are presented. Similar diurnal profiles are observed for both methods although they have slightly different dynamic ranges, and there was a discrepancy in the absolute values. The instruments were then tested for a linear response to atmospheric formaldehyde, and for any interferences due to ozone and water, at the National Physics Laboratory. The results demonstrated that both instruments have a linear response to formaldehydeup to 8.6 ppbv. The ozone interference experiments show that each of the techniques have a response due to ozone but of different magnitudes. It has not been possible to fully characterise the water interference in the gas chromatography technique, whilst the fluormetric method was found not to have an interference from this source. Box modelling studies predict formaldehyde concentrations comparable with our measurements and indicate that decomposition of oxygenates (e.g. CH3OH, CH3CHO), contribute significantly to the observed formaldehyde  concentrations.

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

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

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


Abstract


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

 

Interannual variability over the eastern North Atlantic Ocean Chemical and meteorological evide Interannual variability over the eastern North Atlantic Ocean Chemical and meteorological evide

Date added: 08/06/1994
Date modified: 07/24/2009
Filesize: 1.53 MB

Doddridge, B. G., P. A. Dirmeyer, J. T. Merrill, S. J. Oltmans, and R. R. Dickerson (1994), Interannual variability over the eastern North Atlantic Ocean: Chemical and meteorological evidence for tropical influence on regional-scale transport in the extratropics, J. Geophys. Res., 99(D11), 22,923–22,935.


Abstract


Observed boreal fall season (September–November) 1991 surface CO data from Mace Head, Ireland, are characterized by particularly high mixing ratios, as evidenced by high means, medians, and maxima for those months, relative to the same dato for boreal fall 1992. Air parcels characterized by elevated CO during fall 1991 are attributed to European sources on the basis of isentropic back trajectory analysis. A histogram of the 1991 data shows a bimodal distribution representing two discrete source regions, North Atlantic and European, while the 1992 data show only one mode, representing primarily zonal westerly flow over the North Atlantic Ocean. A similar distinction exists in O3 data between the two years. Considerable interannual variability has important implications for observationalists and modelers alike; an inherent uncertainty is introduced by basing any determination of trend from only a few years of data. An isentropic flow climatology for Mace Head illustrates significant differences in the regional-scale flow patterns to Mace Head between the 1991 and the 1992 fall seasons. These differences have been examined in terms of general dynamical principles and tropical/extratropical coupling. There is evidence of the existence of Rossby wave links with the tropical upper troposphere over South America and the central Pacific Ocean which are responsible for the climatic forcing giving rise to the observed interannual variation in large-scale flow patterns and influencing the chemical character of air parcels reaching Mace Head. Using CO as a tracer for short-lived continental anthropogenic O3 precursors and calculating ΔO3/ΔCO for air parcel trajectories following anticyclonic paths over western Europe during the late summer and fall season of 1991, we estimate O3 production over western Europe at about 66 (40–96) billion moles of O3 per summer (∼3 Tg O3 per summer), based on 1985 CO emission inventory dam (37 Tg CO yr−1 for western Europe).

 

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

Date added: 08/06/2007
Date modified: 07/24/2009
Filesize: 673.42 kB

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


Abstract


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

 

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

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

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


Abstract


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

 

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

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

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


Abstract

 

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

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

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

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


Abstract

In situ, gas chromatographic measurements of non-methane hydrocarbons and dimethyl sulfide at a In situ, gas chromatographic measurements of non-methane hydrocarbons and dimethyl sulfide at a

Date added: 08/05/1997
Date modified: 07/24/2009
Filesize: 587.14 kB

Lewis, A.C.; Bartle, K.D.; Heard, D.E.; McQuaid, J.B.; Pilling, M.J.; Seakins, P.W. (1997) In situ, gas chromatographic measurements of non-methane hydrocarbons and dimethyl sulfide at a remote coastal location (Mace Head, Eire) July-August 1996, Faraday Transactions, 93,  pp.2921-2927.


Abstract


Atmospheric non-methane hydrocarbons (NMHC) and dimethyl sulÐde (DMS) have been monitored at a remote coastal location Mace Head, Eire) using adsorption sampling techniques with analysis by in situ gas chromatography as part of the ACSOE OXICOA 1996 campaign. Concentrations varied considerably during the campaign but can be consistently interpreted by consideration of the relevant back-trajectory of the monitored air mass. Isoprene is conÐrmed as the most important NMHC in determining OH removal, contributing to up to 20%. Isoprene shows strong diurnal variations, although the structure of the diurnal pattern depends on the origin of the air mass. In contrast to previous studies, DMS concentrations during the campaign appeared to show no consistent diurnal variation.

In situ measurements of atmospheric methane at GAGE AGAGE sites during 1985–2000 and resulting source inferences In situ measurements of atmospheric methane at GAGE AGAGE sites during 1985–2000 and resulting source inferences

Date added: 08/01/2002
Date modified: 07/24/2009
Filesize: 7.81 MB
Cunnold, D. M., et al. (2002), In situ measurements of atmospheric methane at GAGE/AGAGE sites during 1985–2000 and resulting source inferences, J. Geophys. Res., 107(D14), 4225, doi:10.1029/2001JD001226.

Abstract


Continuous measurements of methane since 1986 at the Global Atmospherics Gases Experiment/Advanced Global Atmospherics Gases Experiment (GAGE/AGAGE) surface sites are described. The precisions range from approximately 10 ppb at Mace Head, Ireland, during GAGE to better than 2 ppb at Cape Grim, Tasmania, during AGAGE (i.e., since 1993). The measurements exhibit good agreement with coincident measurements of air samples from the same locations analyzed by Climate Monitoring and Diagnostics Laboratory (CMDL) except for differences of approximately 5 ppb before 1989 (GAGE lower) and about 4 ppb from 1991 to 1995 (GAGE higher). These results are obtained before applying a factor of 1.0119 to the GAGE/AGAGE values to place them on the Tohoku University scale. The measurements combined with a 12-box atmospheric model and an assumed atmospheric lifetime of 9.1 years indicates net annual emissions (emissions minus soil sinks) of 545 Tg CH4 with a variability of only ±20 Tg from 1985 to 1997 but an increase in the emissions in 1998 of 37 ± 10 Tg. The effect of OH changes inferred by Prinn et al. [2001] is to increase the estimated methane emissions by approximately 20 Tg in the mid-1980s and to reduce them by 20 Tg in 1997 and by more thereafter. Using a two-dimensional (2-D), 12-box model with transport constrained by the GAGE/AGAGE chlorofluorocarbon measurements, we calculate that the proportion of the emissions coming from the Northern Hemisphere is between 73 and 81%, depending on the OH distribution used. However, this result includes an adjustment of 5% derived from a simulation of the 2-D estimation procedure using the 3-D MOZART model. This adjustment is needed because of the very different spatial emission distributions of the chlorofluorocarbons and methane which makes chlorofluorocarbons derived transport rates inaccurate for the 2-D simulation of methane. The 2-D model combined with the annual cycle in OH from Spivakovsky et al. [2000] provide an acceptable fit to the observed 12-month cycles in methane. The trend in the amplitude of the annual cycle of methane at Cape Grim is used to infer a trend in OH in 30°–90°S of 0 ± 5% per decade from 1985 to 2000, in qualitative agreement with Prinn et al. [2001] for the Southern Hemisphere.

In situ measurement of the ratio of aerosol absorption to extinction coefficient In situ measurement of the ratio of aerosol absorption to extinction coefficient

Date added: 07/31/1980
Date modified: 07/02/2009
Filesize: 558.49 kB

Bruce, C.W., Yee, Y.P., and Jennings, S.G. (1980)- In situ measurements of the ratio of aerosol absorption to extinction coefficients. Appl. Opt., 19, 1893-1894.


Abstract


A knowledge of the proportion of absorbed to scattered radiation for countermeasure smokes is necessary for modeling battlefield effects. Measurement of the total scattered component, however, is difficult. This report presents results obtained by using a new and simpler approach focussing on the extinction and the absorption coefficients (the total scattering coefficient is the difference quantity). Measurements of the absorption and extinction coefficients due to smoke produced by the combustion of 'red phosphorous' are simultaneously obtained in a small test chamber. The same CO2 laser beam at lambda = 9.55 micron is used to produce both results. A form of aerosol spectrophone cell was used to measure the absorption coefficient while functioning as a transmission cell from which the extinction coefficient was calculated. The ratio of the absorption to extinction coefficients was then compared with estimates of the same quantities based on calculated particle sizes, the particle size estimates being obtained from characteristics of the settling process. The ratio agreed with that predicted within the experimental error.

In situ chloroform measurements at Advanced Global Atmospheric Gases Experiment atmospheric research stations from 1994 to 1998 In situ chloroform measurements at Advanced Global Atmospheric Gases Experiment atmospheric research stations from 1994 to 1998

Date added: 08/01/2001
Date modified: 07/24/2009
Filesize: 1.54 MB
O'Doherty, S., et al. (2001), In situ chloroform measurements at Advanced Global Atmospheric Gases Experiment atmospheric research stations from 1994 to 1998, J. Geophys. Res., 106(D17), 20,429–20,444.

Abstract


Measurements of atmospheric chloroform (CHCl3) by in situ gas chromatography using electron capture detection are reported from the Advanced Global Atmospheric Gases Experiment (AGAGE) network of atmospheric research stations. They are some of the most comprehensive in situ, high-frequency measurements to be reported for CHCl3 and provide valuable information not only on clean “baseline” mixing ratios but also on local and regional sources. Emissions from these sources cause substantial periodic increases in CHCl3 concentrations above their baseline levels, which can be used to identify source strengths. This is particularly the case for measurements made at Mace Head, Ireland. Furthermore, these local sources of CHCl3 emissions are significant in relation to current estimates of global emissions and illustrate that the understanding of competing sources and sinks of CHCl3 is still fragmentary. These observations also show that CHCl3 has a very pronounced seasonal cycle with a summer minimum and winter maximum presumably resulting from enhanced destruction by OH in the summer. The amplitude of the cycle is dependent on sampling location. Over the 57 months of in situ measurements a global average baseline concentration of 8.9±0.1 ppt was determined with no appreciable trend in the baseline detected.

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

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

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


Abstract


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

Impact of volcanic ash plume aerosol on cloud microphysics Impact of volcanic ash plume aerosol on cloud microphysics

Date added: 03/19/2013
Date modified: 03/19/2013
Filesize: 3.41 MB

Martucci, M., J. Ovadnevaite, D. Ceburnis, H. Berresheim, S .Varghese, D. Martin, R. Flanagan, C. D. O'Dowd, Impact of volcanic ash plume aerosol on cloud microphysics., Atmos Environ, doi:10.1016/j.atmosenv.2011.12.033 , 2011


Abstract. This study focuses on the dispersion of the Eyjafjallajökull volcanic ash plume over the west of Ireland, at the Mace Head Supersite, and its influence on cloud formation and microphysics during one significant event spanning May 16th and May 17th, 2010. Ground-based remote sensing of cloud microphysics was performed using a Ka-band Doppler cloud RADAR, a LIDAR-ceilometer and a multi-channel microwave radiometer combined with the synergistic analysis scheme SYRSOC (Synergistic Remote Sensing Of Cloud). For this case study of volcanic aerosol interaction with clouds, cloud droplet number concentration (CDNC), liquid water content (LWC), and droplet effective radius (reff) and the relative dispersion were retrieved. A unique cloud type formed over Mace Head characterized by layer-averaged maximum, mean and standard deviation values of the CDNC, reff and LWC: Nmax = 948 cm-3, N = 297 cm-3, σN = 250 cm-3, reff max = 35.5 μm, reff = 4:8 μm, σreff = 4:4 μm, LWCmax =0:23 g m-3, LWC = 0:055 g m-3, σLWC =0:054 g m-3, respectively. The high CDNC, for marine clean air, were associated with large accumulation mode diameter (395 nm) and a hygroscopic growth factor consistent with sulphuric acid aerosol, despite being almost exclusively internally mixed in submicron sizes. Additionally, the Condensation Nuclei (CN, d > 10 nm) to Cloud Condensation Nuclei (CCN) ratio, CCN:CN ~1 at the moderately low supersaturation of 0.25%. This case study illustrates the influence of volcanic aerosols on cloud formation and microphysics and shows that volcanic aerosol can be an efficient CCN.

 

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

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

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


Abstract


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

Igac August 2001 Igac August 2001

Date added: 08/06/2001
Date modified: 08/06/2008
Filesize: 1.91 MB

Hygroscopic properties of nucleation mode and Aitken mode particles during nucleation bursts an Hygroscopic properties of nucleation mode and Aitken mode particles during nucleation bursts an

Date added: 08/06/2002
Date modified: 07/24/2009
Filesize: 925.58 kB

Väkevä, M., K. Hämeri, and P. P. Aalto (2002), Hygroscopic properties of nucleation mode and Aitken mode particles during nucleation bursts and in background air on the west coast of Ireland, J. Geophys. Res., 107(D19), 8104, doi:10.1029/2000JD000176.


Abstract


The hygroscopic and cloud condensation nuclei (CCN) properties of submicrometer atmospheric aerosol particles were investigated using an Ultrafine Tandem Differential Mobility Analyzer (UF-TDMA) and a CCN counter at the Mace Head Monitoring Station on the west coast of Ireland during the New Particle Formation and Fate in the Coastal Environment (PARFORCE) field campaign in September 1998 and June 1999. These measurements give indirect in situ information on the composition and state of mixing of the aerosol particles. The UF-TDMA was used for monitoring of hygroscopic diameter growth factors of aerosol particles with dry mobility diameters 8–20 nm when taken from dry state to a controlled humid environment (RH 90%). The CCN counter was used to study the activation of aerosol particles when exposed to supersaturated conditions (dry diameters of 15–150 nm). It was seen that in clean marine air masses during the observed particle formation events, the newly formed nucleation mode particles (8 and 10 nm) most often had low growth factors (between 1.0 and 1.1) resulting from low solubility. This indicates that the nucleation mode particles consist of nonsoluble or weakly soluble species, possible accompanied by a small soluble part; however, when nucleation mode particles were observed outside the event periods, the growth factors were higher (about 1.3–1.4). In contrast, the 20 nm particles usually clearly belonged to the Aitken mode (based on number size distribution measurements) and had hygroscopic properties similar to some common salts (growth factors 1.4–1.5).

 

Hygroscopic and CCN properties of aerosol particles in boreal forests Hygroscopic and CCN properties of aerosol particles in boreal forests

Date added: 07/31/2001
Date modified: 07/02/2009
Filesize: 498.17 kB
Hämeri, K. J.M. Mäkelä, L. Pirjola, M. Väkevä, P. Aalto, P. Miikkulainen, and C.D. O'Dowd, Hygroscopic properties of boreal forest aerosol during nucleation events. Tellus B, 53, 359-378, 2001

Abstract


The measurements of the hygroscopic and cloud condensation nuclei (CCN) properties of submicrometer atmospheric aerosol particles were performed with two tandem differential mobility analysers (TDMA) and a CCN counter at the Hyytia¨ la¨ forest field station in south-central Finland during the BIOFOR campaign. The TDMAs were used to measure hygroscopic diameter growth factors of individual aerosol particles in the dry particle diameter range 10–365 nm when taken from the dry state (relative humidity RH<5%) to RH=90%. The CCN counter was used to study the activation of aerosol particles when exposed to supersaturated conditions. The measurements show clear diurnal pattern of particle solubility. The pattern was strongest for particles in nucleation and Aitken modes. The lowest growth factor (soluble fraction) values were detected during late evening and early morning and the maximum was observed during noon–afternoon. The highest soluble fractions were determined for nucleation mode particles. The response of hygroscopic growth to changes of relative humidity suggests that the soluble compounds are either fully soluble or deliquescent well before 70% RH. The hygroscopic growth was investigated additionally by a detailed model using the size-resolved composition from the impactor samples. The comparison between different instruments shows good consistency. We found good agreement for the 20 nm growth factors measured with two TDMAs, not only on average but also regarding the temporal variation. The similar conclusion was drawn for comparison of TDMA with CCNC for Aitken mode particles with dry sizes 50 and 73 nm. Differences between wet and dry spectra measured using APS and CSASP spectrometer probes were used to derive growth factors for coarse mode particles. Growth factors for coarse mode particles (Dp ca. 2 mm) ranged between 1.0 and 1.6. Agreement between the evolution of growth factors with time for both accumulation and coarse modes was observed regularly. However, similar portions of the data set also indicated clear differences and consequently different chemical compositions between both modes. When the differences between both modes were observed, the coarse mode always behaved in a less hygroscopic manner, with growth factors near one.

Hydroxyl Radical Concentrations Estimated from Measurements of Trichloroethylene during the EAS Hydroxyl Radical Concentrations Estimated from Measurements of Trichloroethylene during the EAS

Date added: 08/05/1999
Date modified: 07/24/2009
Filesize: 161.63 kB

Derwent, R.G., N. Carslaw, P. G. Simmonds, M. Bassford, S. O’Doherty, D.B. Ryall, M.J. Pilling, A.C. Lewis, and J.B. McQuaid, Hydroxyl radical concentrations estimated from measurements of trichloroethylene during the EASE/ACSOE campaign at Mace Head, Ireland during July 1996, J. Atmos Chem, 34, 185-205, 1999, (Ser. No. ACP107).


Abstract


During the EASE/OXICOA campaign of the NERC ACSOE programme, trichloroethylene and a wide range of man-made halocarbons and radiatively-active trace gases were monitored with high precision and high frequency throughout July 1996 at Mace Head on the Atlantic Ocean coast of Ireland. Trichloroethylene concentrations in concert with many other trace gases became elevated as regionally-polluted and photochemically-aged air masses reached Mace Head. However, as the anticyclonic air masses retreated during 19 and 20 July, trace gas concentrations remained elevated for a significant period. During this 2-4 day period, trichloroethylene concentrations decayed significantly, though the concentrations of the other more chemically-inert trace gases did not. A detailed interpretation of this behaviour using a Lagrangian dispersion model has allowed the estimation of average and peak OH radical concentrations of 3 and 9 × 106 molecule cm-3, respectively, during the travel from the source areas in the U.K. and the low countries out to Mace Head. Using a simple box model, the available Mace Head measurements, when combined into a detailed chemical mechanism, generated OH radical concentrations which peaked at 7 × 106 molecule cm-3, in close agreement with the estimates based on trichloroethylene decay.

 

How falling raindrops collide How falling raindrops collide

Date added: 08/01/1972
Date modified: 07/02/2009
Filesize: 470.45 kB

S.G Jennings, P.R. Brazier-Smith, J. Latham, ,How falling raindrops collide,Page 313, New Scientist, 10 February 1972


Abstract

Home Environment and Childhood Asthma Home Environment and Childhood Asthma

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

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


Abstract


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

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

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

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


Abstract

 

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

High Electric fields from industrial stack plumes High Electric fields from industrial stack plumes

Date added: 01/01/1976
Date modified: 07/02/2009
Filesize: 338.61 kB

Jennings, S.G., and Jones, C.D. (1976)- High electric fields due to industrial stack plumes. Nature, 264, 236-237.


Abstract


THE use of electrostatic precipitators on an industrial stack to remove particulate matter and aerosol particles is now quite common. The plume emanating from such an installation is likely to be highly electrically charged, and consequently associated electrical effects should be observable downwind of the stack.

Halogenated greenhouse gases at the Swiss High Alpine Site of Jungfraujoch (3580 m asl) Continu Halogenated greenhouse gases at the Swiss High Alpine Site of Jungfraujoch (3580 m asl) Continu

Date added: 08/06/2004
Date modified: 07/24/2009
Filesize: 1.93 MB

Reimann, S., D. Schaub, K. Stemmler, D. Folini, M. Hill, P. Hofer, B. Buchmann, P. G. Simmonds, B. R. Greally, and S. O'Doherty (2004), Halogenated greenhouse gases at the Swiss High Alpine Site of Jungfraujoch (3580 m asl): Continuous measurements and their use for regional European source allocation, J. Geophys. Res., 109, D05307, doi:10.1029/2003JD003923.


Abstract


At the high Alpine site of Jungfraujoch (3580 m asl), 23 halogenated greenhouse gases are measured quasi-continuously by gas chromatography-mass spectrometry (GCMS). Measurement data from the years 2000–2002 are analyzed for trends and pollution events. Concentrations of the halogenated trace gases, which are already controlled in industrialized countries by the Montreal Protocol (e.g., CFCs) were at least stable or declining. Positive trends in the background concentrations were observed for substances which are used as CFC-substitutes (hydrofluorocarbons, hydrochlorofluorocarbons). Background concentrations of the hydrofluorocarbons at the Jungfraujoch increased from January 2000 until December 2002 as follows: HFC 134a (CF3CH2F) from 15 to 27 ppt, HFC 125 (CF3CHF2) from 1.4 to 2.8 ppt, and HFC 152a (CHF2CH3) from 2.3 to 3.2 ppt. For HFC 152a, a distinct increase of its concentration magnitude during pollution events was observed from 2000 to 2002, indicating rising European emissions for this compound. Background concentrations of all measured compounds were in good agreement with similar measurements at Mace Head, Ireland. On the other hand, peak concentrations were significantly higher at the Jungfraujoch. This finding is due to the proximity to potent European sources, foremost in southern Europe. The average ratio of halocarbons versus carbon monoxide (CO) concentrations above their baseline values was used to estimate source strengths for the part of Europe which most influences the Jungfraujoch during pollution events. HFCs emission estimates from Jungfraujoch tend to be higher than figures at Mace Head (Ireland) from the end of the 1990s, which either reflects the increased use of these compounds or the closer location of Jungfraujoch to major southern European sources. Transport of polluted European boundary layer air masses to the high Alpine site was observed especially during frontal passages, foehn events, and thermal lifting of air masses in summer. The measurement data during the periods when the Jungfraujoch was under the influence of the polluted boundary layer were used in combination with concurrent air mass trajectories to allocate above baseline halocarbon concentrations to specific European source regions.

 

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

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

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


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

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

research station and onboard the R/V 

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

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

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

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

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

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

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

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

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

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

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

From the ship

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

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

average growth rate in marine conditions was 3 nm h

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

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

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

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


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

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