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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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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.

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

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.

 

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.

 

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.

 

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.

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.

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.

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.

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.

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 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.

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.

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.

 

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 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.

Low European methyl chloroform emissions inferred from long-term atmospheric measurements Low European methyl chloroform emissions inferred from long-term atmospheric measurements

Date added: 08/26/2005
Date modified: 07/24/2009
Filesize: 186.75 kB

S. Reimann, A.J. Manning, P.G. Simmonds, D.M. Cunnold, R.H.J. Wang, J. Li, A. McCulloch, R.G. Prinn, J. Huang, R.F. Weiss, P.F. Fraser, S. O'Doherty, B.R. Greally, K. Stemmler, M. Hill, and D. Folini, (2005), Low European methyl chloroform emissions inferred from long-term atmospheric measurements, Nature, 433, 506-508.


Abstract


Methyl chloroform (CH3CCl3, 1,1,1,-trichloroethane) was used widely as a solvent before it was recognized to be an ozone-depleting substance and its phase-out was introduced under the Montreal Protocol'. Subsequently, its atmospheric concentration has declined steadily2-4 and recent European methyl chloroform consumption and emissions were estimated to be less than 0.1 gigagrams per year1,5. However, data from a short-term tropospheric measurement campaign (EXPORT) indicated that European methyl chloroform emissions could have been over 20 gigagrams in 2000 (ref. 6), almost doubling previously estimated global emissions1,4. Such enhanced emissions would significantly affect results from the CH3CCl3 method of deriving global abundances of hydroxyl radicals (OH) (refs 7-12) - the dominant reactive atmospheric chemical for removing trace gases related to air pollution, ozone depletion and the greenhouse effect. Here we use long-term, high-frequency data from Mace Head, Ireland and Jungfraujoch, Switzerland, to infer European methyl chloroform emissions. We find that European emission estimates declined from about 60 gigagrams per year in the mid-1990s to 0.3-1.4 and 1.9-3.4 gigagrams per year in 2000-03, based on Mace Head and Jungfraujoch data, respectively. Our European methyl chloroform emission estimates are therefore higher than calculated from consumption data1,5, but are considerably lower than those derived from the EXPORT campaign in 2000

Low Molecular Weight Organic Compounds in Maritime Air Recent Results from NAMBLEX Experiment, Low Molecular Weight Organic Compounds in Maritime Air Recent Results from NAMBLEX Experiment,

Date added: 08/06/2003
Date modified: 07/24/2009
Filesize: 13.55 kB
Read, K.; Hopkins, J.; Lewis, A., "Low Molecular Weight Organic Compounds in Maritime Air: Recent Results from NAMBLEX Experiment, Mace Head, Ireland", Geophysical Research Abstracts Volume 5, 2003.

Abstract

 

A dual channel GC-FID for the simultaneous measurement of C2-C7 non-methane hydrocarbons (NMHC), dimethyl sulphide (DMS) and some previously unmeasured oxygenated hydrocarbons (O-VOC) in the atmosphere has been developed and run alongside an established single channel GC-FID measuring NMHC. The instruments were implemented in the field as part of the NAMBLEX (North Atlantic Marine Boundary Layer Experiment) campaign to investigate the role of these trace species in the marine boundary layer. Oxygen containing species such as aldehydes, ketones and alcohols although well known to be highly significant in atmospheric reactions, have in the past been poorly

understood from both distribution and source perspectives. They exist from a combination of both biogenic and anthropogenic emissions together with a secondary source from hydrocarbon oxidation. Under all maritime conditions the organic composition was dominated by acetone, methanol and acetaldehyde with the sum of these compounds contributing up to 85% of the carbon mass of organics in air and up to 80% of the normalised OH radical sink. The relative contribution of NMHC was only comparable when isoprene emissions from terrestrial sources were present. In marine air masses a positive correlation was seen between average zonal surface wind speed and DMS concentration in air in line with previous studies. No equivalent behaviour was recreated for either acetone or acetaldehyde indicating that in this region the ocean is not a significant atmospheric source. These O-VOC compounds appeared to follow the general trends of anthropogenic NMHC tracers such as acetylene indicating a common terrestrial origin for these compounds. Methanol however showed strong anti correlation with averaged wind speed directly indicating that the surface ocean was acting as a sink.

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

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

Abstract

 


Mace Head Atmospheric Research Station-characterization of aerosol radiative parameters Mace Head Atmospheric Research Station-characterization of aerosol radiative parameters

Date added: 08/01/2003
Date modified: 07/24/2009
Filesize: 1.51 MB

Mace Head Atmospheric Research Station – characterization of aerosol radiative parameters S. Gerard Jennings, C. Kleefeld, C. D. O'Dowd, C. Junker, T.G. Spain, P. O'Brien, A.F Roddy, and T.C. O'Connor Boreal Environ. Res., 8, 303-314, 2003.


Abstract


A fairly concise description and a short history of the Mace Head atmospheric research station, at 53°N, 10°W, on the west coast of Ireland is reported. The relatively high latitude site is representative of background marine air in the Northern Atlantic on the western periphery of Europe. The site is ideally located to measure the prevailing (about 52% of the time) westerly-southwesterly air from the Atlantic, as well as polluted air under anticyclonic conditions from sources east of the site within Ireland, from the UK and from mainland Europe. Three years of aerosol radiative data, over a period from January 2000 to December 2002, are indicative of the medium to longterm measurement programme at the site. These include aerosol scattering coefficient, aerosol absorption coefficient, aerosol optical depth and single scattering albedo, supported by meteorological and air mass trajectory input. Variability in aerosol parameters are shown to be dependent on air mass origin, season and meteorological conditions. Measurements indicate that the dominant contribution to aerosol optical depth is due to scattering, with single scattering albedo in the range 0.941 to 0.997. Measured aerosol optical depth for marine air over the 3 year period varies between 0.03 and 0.38 with a mean value of 0.11 and standard deviation of ±0.06. These values are in fair agreement with other data for the North Atlantic region.

Major component composition of urban PM10 and PM2.5 in Ireland Major component composition of urban PM10 and PM2.5 in Ireland

Date added: 08/01/2005
Date modified: 07/02/2009
Filesize: 476.58 kB
Yin, J., A.G. Allen, R.M. Harrison, S.G. Jennings, E. Wright, M. Fitzpatrick, T. Healy, E. Barry, D. Ceburnis and D. McCusker, Major component composition of urban PM10 and PM2.5 in Ireland, Atmospheric Research, Volume 78, Issues 3-4, Pages 149-165. doi:10.1016/j.atmosres.2005.03.006 2005.

Abstract


The major source categories contributing to particulate air pollution in urban as well as non-urban areas of Ireland were studied over an 18-month period using measurements at five sites including urban roadside, urban centre/background, rural and coastal environments. Daily fine and coarse aerosol samples were collected using dichotomous Partisol samplers. The measurements included gravimetric mass (PM10, PM2.5 and PM2.5–10), soluble ions (SO42−, NO3, Cl, CH3SO3, NH4+, Na+, K+, Mg2+ and Ca2+), elemental carbon (EC) and organic carbon (OC). Mass closure procedures using reconstructed chemical components were used to identify major source categories contributing to the aerosol mass, namely primary marine aerosol (NaCl), secondary inorganic materials [NH4NO3 + (NH4)2SO4], primary anthropogenic combustion materials (EC), primary and secondary organic materials, and re-suspended dusts. Source component contributions differed for fine and coarse particles and at different locations. In urban areas, the major components contributing to fine particle mass (together accounting for 79–84% of PM2.5 mass) were, in order, organic compounds, elemental carbon, ammonium sulphate/ammonium nitrate, whilst in the coarse fraction re-suspended material and sea salt were predominant (56–66%). At the rural and coastal sites, PM2.5 mainly consisted of ammonium sulphate/ammonium nitrate and organic materials (65%), whilst sea salt was the largest contributor to coarse particles (39% rural, 56% coastal). Unexplained materials, accounting for about 7–28% of the mass, were attributed mainly to re-suspended materials at urban sites and organic materials at the other sites, as well as unmeasured water content.

Marine aerosol chemistry gradients Elucidating primary and secondary processes and fluxes Marine aerosol chemistry gradients Elucidating primary and secondary processes and fluxes

Date added: 08/01/2008
Date modified: 07/24/2009
Filesize: 260.53 kB

Ceburnis, D., C. D. O'Dowd, G. S. Jennings, M. C. Facchini, L. Emblico, S. Decesari, S. Fuzzi, and J. Sakalys (2008), Marine aerosol chemistry gradients: Elucidating primary and secondary processes and fluxes, Geophys. Res. Lett., 35, L07804, doi:10.1029/2008GL033462.


Abstract


Production mechanisms of aerosol chemical species, in terms of primary and secondary processes, were studied using vertical concentration gradient measurements at the coastal research station in Mace Head, Ireland. Total gravimetric PM1.0 mass, sea salt and water insoluble organic carbon (WIOC) concentration profiles showed a net production at the surface (i.e. primary production), while nssSO4 and water soluble organic carbon (WSOC) concentration profiles showed a net removal at the surface. These observations indicate that WSOC was predominantly of secondary origin and that WIOC was predominantly of primary origin. Derived PM1 mass fluxes compared reasonably well with those previously obtained from an eddy covariance (EC) technique following a power law relationship with the wind speed (F PM1 = 0.000096*U 4.23). For cases with clear primary organic mass fluxes in the flux footprint WIOM mass fluxes ranged between 0.16 and 1.02 ng m−2 s−1 and WIOM/sea salt mass ratio was 0.34–3.6, in good agreement with previous measurements at Mace Head.

Marine aerosol formation from biogenic iodine emissions Marine aerosol formation from biogenic iodine emissions

Date added: 07/31/2002
Date modified: 07/02/2009
Filesize: 373.3 kB

O'Dowd, C.D., J.L. Jimenez, R. Bahreini, R.C. Flagan, J.H. Seinfeld, K. Hämeri, L. Pirjola, M. Kulmala, S.G. Jennigns and T. Hoffmann, Marine aerosol formation from biogenic iodine emissions, Nature, 417, 632-636, 2002.


Abstract


The formation of marine aerosols and cloud condensation nuclei—from which marine clouds originate—depends ultimately on the availability of new, nanometre-scale particles in the marine boundary layer. Because marine aerosols and clouds scatter incoming radiation and contribute a cooling effect to the Earth's radiation budget1, new particle production is important in climate regulation. It has been suggested that sulphuric acid—derived from the oxidation of dimethyl sulphide—is responsible for the production of marine aerosols and cloud condensation nuclei. It was accordingly proposed that algae producing dimethyl sulphide play a role in climate regulation2, but this has been difficult to prove and, consequently, the processes controlling marine particle formation remains largely undetermined3, 4. Here, using smog chamber experiments under coastal atmospheric conditions, we demonstrate that new particles can form from condensable iodine-containing vapours, which are the photolysis products of biogenic iodocarbons emitted from marine algae. Moreover, we illustrate, using aerosol formation models, that concentrations of condensable iodine-containing vapours over the open ocean are sufficient to influence marine particle formation. We suggest therefore that marine iodocarbon emissions have a potentially significant effect on global radiative forcing.

Marine Aerosol Production: a review of the current knowledge Marine Aerosol Production: a review of the current knowledge

Date added: 08/06/2007
Date modified: 07/02/2009
Filesize: 1.51 MB

O’Dowd, C.D., & G. de Leeuw, Marine Aerosol Production: a review of the current knowledge, , Phil. Trans. R. Soc. A, doi:10.1098/rsta.2007.2043, 2007


Abstract


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

 

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

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

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


Abstract


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

Marine aerosols and iodine emissions Marine aerosols and iodine emissions

Date added: 08/01/2005
Date modified: 07/24/2009
Filesize: 77.44 kB

O’Dowd, C.D., J.L. Jimenez, R. Bahreini, R.C. Flagan J.H. Seinfeld, L. Pirjola, M. Kulmala, S.FG. Jennings and T. Hoffmann, Marine aerosols and iodine emissions, Nature, DOI 10.1038/nature03373, 2005.


Abstract


The formation of marine aerosols and cloud condensation nuclei—from which marine clouds originate—depends ultimately on the availability of new, nanometre-scale particles in the marine boundary layer. Because marine aerosols and clouds scatter incoming radiation and contribute a cooling effect to the Earth's radiation budget1, new particle production is important in climate regulation. It has been suggested that sulphuric acid—derived from the oxidation of dimethyl sulphide—is responsible for the production of marine aerosols and cloud condensation nuclei. It was accordingly proposed that algae producing dimethyl sulphide play a role in climate regulation2, but this has been difficult to prove and, consequently, the processes controlling marine particle formation remains largely undetermined3, 4. Here, using smog chamber experiments under coastal atmospheric conditions, we demonstrate that new particles can form from condensable iodine-containing vapours, which are the photolysis products of biogenic iodocarbons emitted from marine algae. Moreover, we illustrate, using aerosol formation models, that concentrations of condensable iodine-containing vapours over the open ocean are sufficient to influence marine particle formation. We suggest therefore that marine iodocarbon emissions have a potentially significant effect on global radiative forcing.

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

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

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


Abstract


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

 

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

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

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


Abstract


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

 

Marine particle nucleation Observation at Bodega Bay, California Marine particle nucleation Observation at Bodega Bay, California

Date added: 08/06/2006
Date modified: 07/24/2009
Filesize: 1.48 MB

Wen, J., Y. Zhao, and A. S. Wexler (2006), Marine particle nucleation: Observation at Bodega Bay, California, J. Geophys. Res., 111, D08207, doi:10.1029/2005JD006210.


Abstract


A TSI nano-SMPS was installed in a lab at Bodega Bay, about 50 m from the coastline and 5 m above sea level. On the basis of measurements conducted from June to December 2001 and from January to June 2003, we have observed two kinds of nucleation events, i.e., long-term (a few hours) and short-term (a few minutes) particle bursts. The long-term events mostly occur during daytime in the summer, lasting from 0.5 to 8 hours. Narrow spikes (short-term events) that occur year-round, both day and night, last only a few minutes to a half hour but contain particle number concentrations comparable to some of the long-term events. Wind direction and speed affect the occurrence and intensity of the particle burst. Nucleation mostly takes place during northwesterly onshore wind for both long- and short-term events, and the probability of nucleation occurrence is higher at higher wind speed. However, in contrast to what has been observed at Mace Head, Ireland, nucleation at Bodega Bay does not correlate with tidal height. Instead, the seasonal and interannual variations of ultrafine particle number concentration N3–10nm appear to correlate with ocean upwelling, a characteristic of currents along the west coast of the United States that brings up nutrients from subsurface waters, promoting plant productivity. Simultaneous measurements of nucleation at the coast and 1.6 km out suggest that nucleation is a coastal phenomenon, supporting the contention that it is related to direct or biogenic emission of precursor gases from the coastal area during the sea upwelling periods.

 

Mass absorption Coefficient of natural Aerosol Particles in the 0.4 - 2.4um Wavelength Interval.. Mass absorption Coefficient of natural Aerosol Particles in the 0.4 - 2.4um Wavelength Interval..

Date added: 08/26/1973
Date modified: 07/22/2009
Filesize: 8.15 MB
K. Fischer, "Bestimmung der Absorption von sichtbarer Strahlung durch Aerosolpartikeln," Contrib. Atmos. Phys. 43, 244 (1970); "Mass Absorption Coefficient of Natural Aerosol Particles in the 0.4–2.4 µm Wavelength Interval," Contrib. Atmos. Phys. 46, 89 (1973), "Mass Absorption Indices of Various Types of Natural Aerosol Particles in the Infrared," Appl. Opt. 14, 2851 (1975).

Abstract

 

Theoretical investigation have predicted that absorption of solar radiation by particulate matter- suspended as aerosol particles in the air - plays an important part in the radiation budget of the atmosphere.

In the present study the mass absorption coeffiecnet K/P (i.e. the imaginary part of the refractive index related to density) is determined for the 0.4 - 2.4 um wavelength intercal wavelength interval. The measuremetn are performed on films of aerosol particles which were collected by an automatic jet impactor at several urban and remote sites.

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

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

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


Abstract


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

Measurement and analysis of aerosol and black carbon in the southwestern United States and Panama an Measurement and analysis of aerosol and black carbon in the southwestern United States and Panama an

Date added: 08/01/2004
Date modified: 07/02/2009
Filesize: 856.64 kB
Junker, C., Sheahan, J., Jennings, S.G., O’Brien, P., Hinds, B.D., Martinez-Tway, E., Hansen, A.D.A., White, C., Garvey, D.M., and Pinnick, R.G., 2004. Measurement and analysis of aerosol and black carbon in the Southern United States and Panama and their dependence on air mass origin, J. Geophys. Res. 109, D13201, doi: 10.1029/2003JD004066.

Abstract


Total aerosol mass loading, aerosol absorption, and black carbon (BC) content were determined from aerosol collected on 598 quartz fiber filters at a remote, semiarid site near Orogrande, New Mexico from December 1989 to October 1995. Aerosol mass was determined by weighing filters before and after exposure, and aerosol absorption was determined by measuring the visible light transmitted through loaded filter samples and converting these measurements to aerosol absorption. BC content was determined by measuring visible light transmitted through filter samples before and after firing and converting the absorption to BC mass, assuming a BC absorption cross section of 19 m2/g in the fiber filter medium. Two analyses were then performed on each of the logged variables: an autoregressive integrating moving average (ARIMA) analysis and a decomposition analysis using an autoregressive model to accommodate first-order autocorrelation. The two analyses reveal that BC mass has no statistically significant seasonal dependence at the 5% level of significance but only random fluctuations varying around an average annual value that has a long-term decreasing trend (from 0.16 to 0.11 μg/m3 during 1990–1995). Aerosol absorption, which is dominated by BC, also displays random fluctuations about an average value, and decreases from 1.9 Mm−1 to 1.3 Mm−1 during the same period. Unlike BC, aerosol mass at the Orogrande site displays distinctly different character. The analyses reveal a pronounced seasonal dependence, but no long-term trend for aerosol mass. The seasonal indices resulting from the autoregression analysis have a minimum in January (−0.78) and maximum in June (+0.58). The geometric mean value over the 1990–1995 period for aerosol mass is 16.0 μg/m3. Since BC aerosol at the Orogrande site is a product of long-range atmospheric transport, a back trajectory analysis of air masses was conducted. Back trajectory analyses indicate that air masses traversing high population centres on the west coast of the USA can lead to significant BC loading, while air masses originating from the southeast of the site tend to have less BC. Additional aerosol measurements are reported for a remote maritime site located on the Atlantic side of the former Panama Canal Zone for the 1976–1979 period, although these data have been analyzed with less statistical rigor. The average geometric mean value of aerosol mass loading for this site is 9.7 μg/m3, with a significant decreasing trend of −19% per year. The mean value of aerosol absorption is 0.59 Mm−1, with a decreasing trend of −15% per year.

Measurement and interpretation of OH and HO2 radicals during NAMBLEX Measurement and interpretation of OH and HO2 radicals during NAMBLEX

Date added: 08/06/2003
Date modified: 07/23/2009
Filesize: 8.76 kB
Lee, J.; Smith, S.; Bloss, W.; Heard, D.; Johnson, G.Measurement and interpretation of OH and HO2 radicals during NAMBLEX

Abstract

 

We present measurements of the hydroxyl, OH, and hydroperoxyl, HO2, radicals obtained during the summer 2002 North Atlantic Marine Boundary Layer Experiment at the Mace Head Atmospheric Research Station, Ireland. Direct  easurements
of [OH] were made using laser-induced fluorescence (LIF) at 308 nm, whilst measurements of [HO2] were made possible subsequent to chemical conversion to OH using NO. Calibration of the measurements of both species was carried out

using a technique based on the photolysis of H2O by a mercury lamp at 184.9 nm. Measurements of OH and HO2 were made on 24 and 13 days respectively, and the noon-time maxima in [OH] and [HO2] were found to vary between 3 - 8 x 10ˆ6 and 1.5 - 2.1 x 10ˆ8 molecule cm-3 respectively for j(O1D) in the range 0.5 - 2.2 x 10ˆ-5 s-1. There is significant evidence to support the presence of night-time HO2 radicals with concentrations in the range 2 - 3 x 10ˆ7 molecule cm-3 (mean [HO2] night-time detection limit 9.65 x 10ˆ6 molecule cm-3). The limited data available for [OH] at night suggest that there is some evidence for the presence of the species above its night-time detection limit (mean night-time [OH]  detection limit = 5.74 x 10ˆ4 molecule cm-3). The data set was used along with a wide range of supporting measurements to carry out a detailed study of chemistry in a range of clean and semi-polluted air masses. A strong correlation between [OH] and the rate of its primary production, P(OH), has been illustrated in both types of air mass with a reduction in dependence as [NOx] increases. A simple steady state calculation has also shown relatively good agreement highlighting the dominance of the CO and CH4 destruction routes in the Marine Boundary Layer (MBL). An analysis of the functional dependence of [OH], [HO2] and the ratio [HO2] / [OH] on [NOx] illustrated the non linear relationship between HOx and NOx radicals. Steady state modelling of [OH] versus [NOx] gave results within the error of the measurements. Similar modelling of [HO2] and [HO2] / [OH] versus [NOx] agreed well at higher [NOx], but showed discrepancies of increasing magnitude for [NOx] < 900 pptv. The effect of the reaction of halogen monoxide species (IO and BrO) with HO2 is also investigated. Observed levels of IO and BrO during NAMBLEX are such that the XO + HO2 reaction can account for up to 40 % of the total sink for HO2 radicals during clean marine air (low NOx) episodes, and to make a significant contribution to the production of OH via the photolysis of HOX.

Measurement of contaminant removal from skin using a portable fluorescence scanning system Measurement of contaminant removal from skin using a portable fluorescence scanning system

Date added: 08/01/2005
Date modified: 07/02/2009
Filesize: 189.8 kB

Hession, H, Byrne, MA, Cleary, S, Andersson, KG and J Roed. Measurement of contaminant removal from skin using a portable fluorescence scanning system. In press: Journal of Environmental Radioactivity, 2005.


Abstract


The residence time of particulate contamination on the human body is a factor that has an important impact on the accuracy of exposure assessment in the aftermath of an accidental release of radionuclides to the atmosphere. Measurements of particle clearance from human skin were made using an illumination system to excite fluorescence in labelled silica particles and a CCD camera and image processing system to detect this fluorescence. The illumination system consists of high-intensity light emitting diodes (LEDS) of suitable wavelengths arranged on a portable stand. The physically small size of the LEDs allows them to be positioned close to the fluorescing surface, thus maximising the fluorescent signal that can be obtained. The limit of detection was found to be 50 μg of tracer particle per cm2.

Experiments were carried out to determine the clearance rates of 10 μm and 3 μm particles from the skin. Results show that, in the absence of any mechanical rubbing of the skin, the clearance of particles from the skin followed an approximately exponential decay with a half-time of 1.5–7.8 h. Skin hairiness and degree of human movement were found, in addition to particle size, to have an important influence on particle fall-off rate.

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

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

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


Abstract


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

Measurements of aerosol scattering coefficient over a period of 2 years at Mace Head, Ireland Measurements of aerosol scattering coefficient over a period of 2 years at Mace Head, Ireland

Date added: 08/07/1999
Date modified: 08/07/2008
Filesize: 134.93 kB
Ch. Kleefeld, S. O'Reilly and S.G. Jennings ,MEASUREMENTS OF AEROSOL SCATTERING COEFFICIENT OVER A PERIOD OF 2 YEARS AT MACE HEAD, IRELAND,J. Aerosol Sci. Vol. 30, Suppl. 1, pp. S 157-S 158, 1999

Measurements of Atmospheric Mercury Concentrations in Northwestern and Central Europe --- Comparison Measurements of Atmospheric Mercury Concentrations in Northwestern and Central Europe --- Comparison

Date added: 08/26/1995
Date modified: 07/23/2009
Filesize: 1.09 MB

R. Ebinghaus, H.H. Kock, S.G. Jennings, P. McCartin and M.J. Orren (1995): Measurements of Atmospheric Mercury Concentrations in Northwestern and Central Europe --- Comparison of Experimental Data and Model Results, Atmospheric Environment, Vol. 29, No. 22, pp. 3333 - 3344


Abstract


Field experiments were carried out at various sites in Europe to compare ambient air and precipitation concentrations of atmospheric mercury with model data. In addition, ozone and aerosol black carbon concentrations in air were measured simultaneously as input data for validation of the EMEP-based European long-range transport model. Data sets for mercury in air and precipitation, ozone and aerosol black carbon show that the selected sites range from background conditions for Northwestern Europe to regionally influenced air masses from heavily industrialized Central Europe. Measured 12 h averaged mercury concentrations in air range from 2.1 ng m-3 for Mace Head, Ireland to 8.2 ng m-3 for the Halle/Leipzig/Bitterfeld area in former German Democratic Republic. Precipitation concentrations of total mercury from 17 to 460 ng k-1 were measured from 1991 to 1993 for the same sites. Experimental data and model results for total gaseous mercury and mercury in precipitation are in good agreement.

Measurements of Atmospheric Mercury Concentrations in Northwestern and Central Europe --- Comparison Measurements of Atmospheric Mercury Concentrations in Northwestern and Central Europe --- Comparison

Date added: 08/26/1995
Date modified: 07/10/2009
Filesize: 1.12 MB

R. Ebinghaus, H.H. Kock, S.G. Jennings, P. McCartin and M.J. Orren (1995): Measurements of Atmospheric Mercury Concentrations in Northwestern and Central Europe --- Comparison of Experimental Data and Model Results, Atmospheric Environment, Vol. 29, No. 22, pp. 3333 - 3344


Abstract


Field experiments were carried out at various sites in Europe to compare ambient air and precipitation concentrations of atmospheric mercury with model data. In addition, ozone and aerosol black carbon concentrations in air were measured simultaneously as input data for validation of the EMEP-based European long-range transport model. Data sets for mercury in air and precipitation, ozone and aerosol black carbon show that the selected sites range from background conditions for Northwestern Europe to regionally influenced air masses from heavily industrialized Central Europe. Measured 12 h averaged mercury concentrations in air range from 2.1 ng m-3 for Mace Head, Ireland to 8.2 ng m-3 for the Halle/Leipzig/Bitterfeld area in former German Democratic Republic. Precipitation concentrations of total mercury from 17 to 460 ng k-1 were measured from 1991 to 1993 for the same sites. Experimental data and model results for total gaseous mercury and mercury in precipitation are in good agreement.

Measurements of fractionated gaseous mercury concentrations over northwestern and central Europ Measurements of fractionated gaseous mercury concentrations over northwestern and central Europ

Date added: 08/05/1999
Date modified: 07/23/2009
Filesize: 215.76 kB
Sommar, J., Feng, X., Gardfeldt, K. and Lindqvist, O., 1999. Measurements of fractionated gaseous mercury concentrations in northwestern and central Europe, 1995–99. Journal of Environmental Monitoring 1, pp. 435–439.

Abstract


Although it makes up only a few per cent. of total gaseous mercury (TGM) in the atmosphere, the fraction of xidised (divalent) mercury plays a major role in the biogeochemical cycle of mercury due to its high affinity for water and surfaces. Quantitative knowledge of this fraction present in mixing ratios in the parts-per-1015 (ppq) range is currently very scarce. This work is based on #220 data for divalent gaseous mercury (DGM) collected during 1995–99 in ambient air. Over the course of the measurements, the sampling and analytical methods were modified and improved. This is described here in detail and includes transition from wet leaching and reduction procedures to thermo-reductive desorption, the use of annular as well as tubular denuders and adoption of an automated sampling system. The concentration of DGM exhibited a strong seasonal behaviour in contrast to atomic gaseous mercury, with low values in winter and maximum values in summer. The DGM/TGM ratios were frequently found to be below the detection limit (1%) and in the range 1–5%. A trend of diurnal DGM patterns was observed and implies photolytically induced sources. Scavenging of DGM during rain events was also noticed.

 

Measurements of gas-phase hydrogen peroxide and methyl hydroperoxide in the coastal environment duri Measurements of gas-phase hydrogen peroxide and methyl hydroperoxide in the coastal environment duri

Date added: 09/14/2002
Date modified: 07/02/2009
Filesize: 313.1 kB
Morgan, R. B., and A. V. Jackson (2002), Measurements of gas-phase hydrogen peroxide and methyl hydroperoxide in the coastal environment during the PARFORCE project, J. Geophys. Res., 107(D19), 8109, doi:10.1029/2000JD000257.

Abstract


Ambient gas-phase hydrogen peroxide (H2O2) and organic hydroperoxides (ROOHs) were measured at Mace Head Atmospheric Monitoring Station during September 1998 and June 1999. These measurements formed part of the New Particle Formation and Fate in the Coastal Environment (PARFORCE) campaign with the intention of assisting with the elucidation of potential oxidation pathways that lead to the production of new particles. A reflux concentrator sampled ambient air prior to on-site analysis by a peroxidase fluorescence technique with specific peroxide detection. Hydrogen peroxide, methyl hydroperoxide (CH3OOH), and several hydroperoxide species were detected. The highest H2O2 concentrations were observed during periods of clean maritime air, and a significant correlation exists between H2O2 concentration and tidal cycle during days when air masses had advected over inter tidal zones upwind of Mace Head. Peak H2O2 concentrations were observed around low tide on these days, coincident with particle events.

Measurements Of Global Radiation Using Black And White Atmometers Measurements Of Global Radiation Using Black And White Atmometers

Date added: 08/07/1955
Date modified: 07/03/2009
Filesize: 1.43 MB
TC O Connor ,Measurements Of Global Radiation Using Black And White Atmometers , Geofiscica Pura E Applicata -Milano Vol 30 p 130-136 (1955)

Abstract

 

The difference in the evaporation from black and white Livingston atmometers was compared with the global radiation as measured by a Bellani spherical pyranometer. Results show that one unit (cm^3) of difference in the evaporation corresponds to 20+/- 3 cal/cm^2 of global radiation. The total of 95 daily values of radiation measured by pairs of atmometers differed from the corresponding Bellani figure by 2.3%. The operation of the atmometers and the accuracy of the results are discussed. The method is considered sufficiently accurate for the general climatological purposes.

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

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

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


Abstract


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

Measurements of the number concentration of aitken nuclei at mountain and rural sites Measurements of the number concentration of aitken nuclei at mountain and rural sites

Date added: 08/01/1975
Date modified: 07/03/2009
Filesize: 1.25 MB
Jennings, S.G.  (1975)- Measurements of condensation Aitken nuclei at rural and mountain sites. Jnl. de Rech. Atmos., No. 2,  59-66.

Abstract

 

A study of the number concentration at Aitken nuclei has been carried out using automated Nolan Pollak photoelectric nucleus ountain site, a sparsely populated site and in a rural envirorment. It has been found that the nucleus counter assembly operates very satisfactorily over long periods under field conditions.

The appuratus has proven to be particularly senstive in detecting pertubations in the background count due to localized nuclei sources. Frequency distribution curves of the individual observations follow closely a log-normal distribution for each measurement period. It is shown that te two minute sampling frequency can be increased by about an order of magnitude without causing a significant change in the nuclei number distribution.

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

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

Abstract


Meteorological influences on coastal new particle formation Meteorological influences on coastal new particle formation

Date added: 07/31/2002
Date modified: 07/23/2009
Filesize: 1.07 MB
Gerrit de Leeuw, Gerard Kunz, Gintautas Buzorius, and Colin O'Dowd, Meteorological influences on coastal new particle formation, J. Geophys. Res. 107, 10.1029/2001JD001478, 2002.

Abstract


The meteorological situation at the midlatitude coastal station of Mace Head, Ireland, is described based on observations during the New Particle Formation and Fate in the Coastal Environment (PARFORCE) experiments in September 1998 and June 1999. Micrometeorological sensors were mounted near the shore line on a small mast with a height of 3 m and on a 22 m high tower at about 100 m away from the sea. Turbulent fields of wind speed, air temperature, and water vapor were measured. Parameters such as the friction velocity, drag coefficient, kinematic fluxes of heat and water vapor, and various variances were derived. The influence of meteorological parameters on coastal nucleation events is examined, and it is found that the occurrence of nucleation is, more or less, independent of air mass origin and is primarily driven by the occurrence of exposed shore areas during low tide and solar radiation. Micrometeorological influences were also examined in terms of promoting particle production events in this environment. A positive correlation was found between kinematic heat flux and particle production probability. In contrast, a strong negative correlation was found between production probability and both kinematic water vapor fluxes and relative humidity. These results indicate that the occurrence of new particle production events in the coastal zone are most probable during conditions when the shore area containing coastal biota has dried out and the biota are exposed directly to the solar radiation flux and increased shore, or surface, temperatures. These conditions correspond to drying and stressing of the biota, which is known to increase the emissions of biogenic vapors.

Micron-sized droplets irradiated with a pulsed CO2 laser measurement of explosion and breakdown thresholds Micron-sized droplets irradiated with a pulsed CO2 laser measurement of explosion and breakdown thresholds

Date added: 07/31/1990
Date modified: 07/03/2009
Filesize: 1.33 MB
Pinnick, R.G., Biswas, A., Armstrong, R.L., Jennings, S.G., Pendleton, J.D., and Fernandez, G. (1990). - Micron-sized droplets irradiated with a pulsed CO2 laser: Measurements of explosion and breakdown thresholds. Appl. Opt., 29, 918 - 925.

Abstract


Measurements of minimum CO2 laser fluence required to explode or disintegrate 10–60 µm radius droplets of water, ethanol, diesel (hexadecane), CCl4, bromoform, and ethyl bromide are reported. Threshold fluences range from 0.4 J cm-2 for 10-µm radius ethanol drops to 20 J cm-2 for 30µm bromoform drops. Threshold fluences for water droplets are ~3 J cm-2 independent of drop size. Comparison of the measurements to calculations of laser fluence required for considered absorbing droplets to reach superheat temperature is in good agreement for cases where liquid material properties are known, suggesting that superheating of droplets is the dominant mechanism causing explosion/disintegration. Measured droplet-induced laser breakdown thresholds are considerably higher than explosion thresholds and have less dependence on droplet size and composition. The highest breakdown threshold values are for water drops, which range from 150 to 280 J cm-2 (0.9–1.7 × 109W cm-2) compared with 670 J cm-2 (4.0 × 109 W cm-2) for clean air breakdown for the laser pulse length and spot size.

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

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

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


Abstract


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

Mid-latitude North-Atlantic aerosol characteristics in clean and polluted air Mid-latitude North-Atlantic aerosol characteristics in clean and polluted air

Date added: 07/31/2001
Date modified: 07/23/2009
Filesize: 574.87 kB
O'Dowd, C.D., E. Becker and M. Kulmala, Mid-latitude North-Atlantic aerosol characteristics in clean and polluted air, Atmos. Res., 58, 167-185, 2001.

Abstract


Aerosol number concentrations (r>1.5 nm) and size distributions (5 nm–150 μm radius) are reported for air masses typical of clean and polluted air masses over a North–East Atlantic coastal site (Mace Head). In clean marine air, total particle concentration is typically 400–600 cm−3, rising to between 600 and 1500 cm−3 for modified maritime air, and in the most polluted air, concentrations increase to ≈7000 cm−3. In all air masses, regular bursts of ultra-fine (1.5–5 nm) particles (UFP) were observed over several hours duration and coincided with low tide occurrence in the presence of solar radiation. During these bursts, measured UFP concentrations exceeded 180,000 cm−3. Typically, the sub-micron marine size distribution possessed a bi-modal shape, typical of cloud-induced aerosol growth, with an accumulation mode centred at 0.1–0.2 μm (radius) and a fine mode ≈0.02 μm, while super-micron sea-spray particles possessed a mode at ≈1–5 μm, extending to ≈10 μm under moderately low wind speeds of 5–6 m s−1. Under higher wind speed conditions (10–11 m s−1), a spume drop mode, extending to sizes of 150 μm, was observed. In anthropogenically influenced air masses, the sub-micron size distribution remained bi-modal, although to a lesser extent. Number concentration is dominated by sub-micron aerosol in all air masses, in marine air masses, surface area is generally dominated by super-micron particles, and volume is overwhelmingly dominated by the mode centred on 10 μm under moderate conditions, and 100 μm under higher winds. By comparison, in polluted air, surface area is dominated by sub-micron sizes and volume dominated by super-micron sizes. After nucleation bursts, growth of new, ultra-fine, particles into sizes in the accumulation mode can be observed under some conditions with growth rates of the order of 10 nm/h. Calculating the pre-existing aerosol condensation sink and the growth rate of newly formed particles allowed estimation of the condensing vapour concentration producing the observed growth along with the source rate of the condensing vapour. The concentration of condensable vapour and its source strength were 10–14×107 molecules cm−3 and 3–14×105 molecules cm−3 s−1, respectively.

Minimizing light absorption measurement artifacts of the Minimizing light absorption measurement artifacts of the

Date added: 02/15/2011
Date modified: 02/15/2011
Filesize: 2.71 MB

Collaud Coen, M., E. Weingartner, A. Apituley, D. Ceburnis, R. Fierz-Schmidhauser, H, Flentje, J.S. Henzing,  S.G. Jennings, M. Moerman, A. Petzold, O. Schmid, and U. Baltensperger. Minimizing light absorption measurement artifacts of the Aethalometer: evaluation of five correction algorithms: the EUSAAR protocol. Atmos. Meas.Technol., 3, 457-474, 2010.


The aerosol light absorption coefficient is an essential parameter involved in atmospheric radiation budget

calculations. The Aethalometer (AE) has the great advantage of measuring the aerosol light absorption coefficient at several wavelengths, but the derived absorption coefficients are systematically too high when compared to reference methods. Up to now, four different correction algorithms of the AE absorption coefficients have been proposed by several authors. A new correction scheme based on these previously published methods has been developed, which accounts for the optical properties of the aerosol particles embedded in the filter. All the corrections have been tested on six datasets representing different aerosol types and loadings and include multi-wavelength AE and white-light AE. All the corrections have also been evaluated through comparison with a Multi-Angle Absorption Photometer (MAAP) for four datasets lasting between 6 months and five years. The modification of the wavelength dependence by the different corrections is analyzed in detail. The performances and the limits of all AE corrections are determined and recommendations are given.


 

 

 

 

 

Model evaluation of marine primary organic aerosol emission schemes Model evaluation of marine primary organic aerosol emission schemes

Date added: 03/21/2013
Date modified: 03/21/2013
Filesize: 2.12 MB

Gantt, B., M. S. Johnson, N. Meskhidze, J. Sciare, J. Ovadnevaite, D. Ceburnis, C. D. O’Dowd, Model evaluation of marine primary organic aerosol emission schemes, Atmos. Chem. & Phys., 12, 8553–8566, 2012

www.atmos-chem-phys.net/12/8553/2012/ doi:10.5194/acp-12-8553-2012.


Abstract. In this study, several marine primary organic aerosol (POA) emission schemes have been evaluated using the GEOS-Chem chemical transport model in order to provide guidance for their implementation in air quality and climate models. These emission schemes, based on varying dependencies of chlorophyll a concentration ([chl a]) and 10m wind speed (U10), have large differences in their magnitude, spatial distribution, and seasonality. Model comparison with weekly and monthly mean values of the organic aerosol mass concentration at two coastal sites shows that the source function exclusively related to [chl a] does a better job replicating surface observations. Sensitivity simulations in which the negative U10 and positive [chl a] dependence of the organic mass fraction of sea spray aerosol are enhanced show improved prediction of the seasonality of the marine POA concentrations. A top-down estimate of submicron marine POA emissions based on the parameterization that compares best to the observed weekly and monthly mean values of marine organic aerosol surface concentrations has a global average emission rate of 6.3 Tg yr−1. Evaluation of existing marine POA source functions against a case study during which marine POA contributed the major fraction of submicron aerosol mass shows that none of the existing parameterizations are able to reproduce the hourly-averaged observations. Our calculations suggest that in order to capture episodic events and short-term variability in submicron marine POA concentration over the ocean, new source functions need to be developed that are grounded in the physical processes unique to the organic fraction of sea spray aerosol.

 

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