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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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Characterization of individual airborne particles by using aerosol time-of-flight mass spectrom Characterization of individual airborne particles by using aerosol time-of-flight mass spectrom

Date added: 08/06/2004
Date modified: 07/27/2009
Filesize: 425.52 kB

Dall'Osto, M., D. C. S. Beddows, R. P. Kinnersley, R. M. Harrison, R. J. Donovan, and M. R. Heal (2004), Characterization of individual airborne particles by using aerosol time-of-flight mass spectrometry at Mace Head, Ireland, J. Geophys. Res., 109, D21302, doi:10.1029/2004JD004747.


Abstract


An aerosol time-of-flight mass spectrometer was deployed at Mace Head (Ireland) during August 2002. The measurements provide qualitative chemical composition and size distribution (0.3–3 μm) information for single particles. Three broad categories of particles: sea salt, dust, and carbon-containing particles were identified and apportioned, and their temporal evolution (1 hour resolution) is described. Aerosol sources were correlated with meteorological factors and with air mass trajectories, demonstrating long-range transport of different continental air masses from Europe, Africa, and America. The major class of particles was derived from sea salt and was subdivided into pure, mixed, and aged sea salt according to the extent of displacement of chloride by nitrate. Two types of dust particles were found mainly in the coarse mode (>1 μm); the former, thought to originate from the Sahara, presented an aluminium/silicon signature, while the latter, of more local origin, had a calcium-rich composition. Carbon-containing particles were mainly distributed in the fine mode (<1 μm) and associated with different chemical species in different size modes, suggesting different mechanisms of formation.

 

Characterization and intercomparison of aerosol absorption photometers: result of two intercompariso Characterization and intercomparison of aerosol absorption photometers: result of two intercompariso

Date added: 02/16/2011
Date modified: 02/16/2011
Filesize: 3.86 MB

Müller, T., Henzing, J. S., de Leeuw, G., Wiedensohler, A., Alastuey, A., Angelov, H., Bizjak, M., Collaud Coen, M., Engström, J. E., Gruening, C., Hillamo, R., Hoffer, A., Imre, K., Ivanow, P., Jennings, G., Sun, J. Y., Kalivitis, N., Karlsson, H., Komppula, M., Laj, P., Li, S.-M., Lunder, C., Marinoni, A., Martins dos Santos, S., Moerman, M., Nowak, A., Ogren, J. A., Petzold, A., Pichon, J. M., Rodriquez, S., Sharma, S., Sheridan, P. J., Teinilä, K., Tuch, T., Viana, M., Virkkula, A., Weingartner, E., Wilhelm, R., and Wang, Y. Q.: Characterization and intercomparison of aerosol absorption photometers: result of two intercomparison workshops, Atmos. Meas. Tech., 4, 245-268, doi:10.5194/amt-4-245-2011, 2011.


Absorption photometers for real time application have been available since the 1980s, but the use of filter-based instruments to derive information on aerosol properties (absorption coefficient and black carbon, BC) is still a matter of debate. Several workshops have been conducted to investigate the performance of individual instruments over the intervening years. Two workshops with large sets of aerosol absorption photometers were conducted in 2005 and 2007. The data from these instruments were corrected using existing methods before further analysis. The inter-comparison shows a large variation between the responses to absorbing aerosol particles for different types of instruments. The unit to unit variability between instruments can be up to 30% for Particle Soot Absorption Photometers (PSAPs) and Aethalometers. Multi Angle Absorption Photometers (MAAPs) showed a variability of less than 5%. Reasons for the high variability were identified to be variations in sample flow and spot size. It was observed that different flow rates influence system performance with respect to response to absorption and instrumental noise. Measurements with non absorbing particles showed that the current corrections of a cross sensitivity to particle scattering are not sufficient. Remaining cross sensitivities were found to be a function of the total particle load on the filter. The large variation between the response to absorbing aerosol particles for different types of instruments indicates that current correction functions for absorption photometers are not adequate.


Characteristic features of air ions at Mace Head on the west coast of Ireland Characteristic features of air ions at Mace Head on the west coast of Ireland

Date added: 08/07/2008
Date modified: 07/27/2009
Filesize: 917.86 kB

Marko Vana, Mikael Ehn, Tuukka Petaja, Henri Vuollekoski, Pasi Aalto, Gerrit de Leeuw, Darius Ceburnis, Colin D. O'Dowd, Markku Kulmala, Characteristic features of air ions at Mace Head on the west coast of Ireland, Atmospheric Research


Abstract


Coastal nucleation events and behavior of cluster ions were characterized through the measurements of air ion mobility distributions at the Mace Head research station on the west coast of Ireland in 2006. We measured concentrations of cluster ions and charged aerosol particles in the size range of 0.34–40 nm. These measurements allow us to characterize freshly nucleated charged particles with diameters smaller than 3 nm. The analysis shows that bursts of intermediate ions (1.6–7 nm) are a frequent phenomenon in the marine coastal environment. Intermediate ion concentrations were generally close to zero, but during some nucleation episodes the concentrations increased to several hundreds per cm3. Nucleation events occurred during most of the measurement days. We classified all days into one of seven classes according to the occurrence and type of new particle formation. Nucleation events were observed during 207 days in 2006, most prominently in the spring and summer months. Rain-induced events, in turn, were observed during 132 days. Particle formation and growth events mostly coincided with the presence of low tide. Also small cluster ions (0.34–1.6 nm) were characterized. Average concentrations of small ions were 440 cm− 3 for the negative ions and 423 cm− 3 for the positive ions. Average mean mobilities of small ions were 1.86 cm2V− 1s− 1 and 1.49 cm2V− 1s− 1 for the negative and positive polarities, respectively. Concentrations of small ions were observed to be strongly dependent on the variations of meteorological parameters including wind speed and direction.

 

CFCs in Connemara Technology Ireland September 1991 CFCs in Connemara Technology Ireland September 1991

Date added: 09/28/1991
Date modified: 07/27/2009
Filesize: 1.37 MB
O'Connor, T.C. & Simmonds, P.G. (1991)- CFCs in Connemara, Technology Ireland, 23, No. 5, pp. 19-21.

Abstract

 

At an isolated research centre in Conemara, scientist are monitoring the background atmospheric levels of the CFCs and other chemicals which are destroying the ozone layer. Tom O'Connor and Peter Simmonfs write here of how the UCG centre is playing a vital role in international studies to monitor the accumulation of these gases in the global atmosphere.

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

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

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


Abstract

CCN Determination Comparing Counters with single drop counting and photometric detector at Macehead CCN Determination Comparing Counters with single drop counting and photometric detector at Macehead

Date added: 08/01/1996
Date modified: 07/27/2009
Filesize: 5 MB

Gras, J.L., Jennings, S.G., and Geever, M., (1996). CCN determination comparing counters with single drop counting and photometric detectors at Mace Head, Ireland. Idojaras, 100, 171-182.


Abstract


Two static thermal-gradient cloud condensation nucleus (CCN) counters utilising different detection methods were operated over a three week period during May 1994, at Mace Head on the west coast of Ireland. One was a DH Associates model (MI), the other was custom built at the CSIRO Division of Atmospheric Research. Concentrations of CCN at a supersaturation of 0.5% were determined during this period for artificial NaCI aerosol particles and for ambient particles in clean maritime westerly, and continental easterly conditions. No significant differences were found between the relative performance of the counters with artificial NaCI particles and ambient particles, and no statistically significant differences in response were observed between maritime and continental conditions. Overall agreement between the two counters, for concentrations less than 1000 cm-3 was better than 15%.

Carbon Mass Concentration Measurements at Mace head, On the West Coast Of Ireland Carbon Mass Concentration Measurements at Mace head, On the West Coast Of Ireland

Date added: 08/01/1993
Date modified: 07/27/2009
Filesize: 3.5 MB
Jennings, S.G., McGovern, F.M. and Cooke, W.F., 1993. Carbon mass concentration measurements at Mace Head, on the west coast of Ireland. Atmospheric Environment 27A, pp. 1229–1239

Abstract


Measurements of the mass concentration of particulate carbon aerosol at Mace Head atmospheric research station on the west coast of Ireland are reported. The measurements were made using an aethalometer manufactured by Magee Scientific, which operates by measuring the light transmission through a quartz fibre filter, whilst air is drawn through the filter. Mass concentration measurements taken between February 1990 and April 1991 are presented and interpreted in terms of air mass and meteorological parameters. Average carbon mass concentration levels of 38±11 ng m−3 were found during periods when the clean sector sampled air masses had traversed over the North Atlantic for several days

Can the study of nitrogen isotopic composition in size-segregated aerosol nitrate and ammonium Can the study of nitrogen isotopic composition in size-segregated aerosol nitrate and ammonium

Date added: 08/07/2001
Date modified: 07/27/2009
Filesize: 186.81 kB

S.G. Yeatman, L.J. Spokes, P.F. Dennis, T.D. Jickells, Can the study of nitrogen isotopic composition in size-segregated aerosol nitrate and ammonium be used to investigate atmospheric processing mechanisms?, Atmospheric Environment 35 (2001) 1337}1345


Abstract


Atmospheric fixed-nitrogen deposition can contribute to eutrophication in coastal and estuarine waters. Stable nitrogen isotope data can provide important information regarding the sources and processing of atmospheric fixed-nitrogen species and is thus important in controlling eutrophication. Size-segregated aerosol samples were collected from two coastal sites: Weybourne, England and Mace Head, Ireland and also aboard the RRS Challenger in the Eastern Atlantic Ocean. Aerosol concentrations of ammonium and nitrate were determined prior to δ15N isotopic analysis. The isotopic enrichment factor, ε, was calculated for both the species by subtracting the respective δ15N values of the coarse-mode fraction (>1 μm diameter) from those of the fine-mode fraction (<1 μm diameter). Variations in this parameter were observed as weak functions of the percentage of each species in the coarse mode and of meteorological condition. As a result, the presence of two different size-shift processes (dissociation/gas scavenging and dissolution/coagulation) is proposed, consistent with similar arguments based upon major-ion data obtained from the same suite of samples. Dissolution/coagulation processes appear to exhibit negative isotopic enrichment factors whereas dissociation/gas scavenging processes appear to exhibit positive enrichment factors, suggesting that they may be reversible and thermodynamically driven. In offshore-flowing air masses just entering the marine environment, transferral of nitrate to the coarse mode by initial dissociation of NH4NO3 followed by scavenging of the HNO3 produced appears to be significantly more important than in samples of onshore, marine dominated air. In contrast, ammonium appears to be transferred to the coarse mode during offshore flow largely via the dissolution and coagulation of aerosol ammonium, nitrate and sulphate-containing species. During onshore flow, the uptake of gaseous NH3, arising from the continued dissociation of NH4NO3, seems to become increasingly important.

 

Can new particle formation occur in the clean marine boundary layer Can new particle formation occur in the clean marine boundary layer

Date added: 08/06/2000
Date modified: 07/27/2009
Filesize: 1.47 MB

Pirjola, L., C. D. O'Dowd, I. M. Brooks, and M. Kulmala (2000), Can new particle formation occur in the clean marine boundary layer?, J. Geophys. Res., 105(D21), 26,531–26,546.


Abstract


An analysis of new particle formation probability in the marine boundary layer (MBL) is conducted using a detailed aerosol dynamics and gas-phase chemistry model, thermodynamically correct classical binary (H2O-H2SO4) nucleation theory, and recently developed ternary (H2O-H2SO4-NH3) nucleation theory. Additionally, the effect of boundary-layer meteorology (i.e., adiabatic cooling, small scale fluctuations, and entrainment) in enhancing nucleation is also examined. The results indicate that for typical marine conditions, binary nucleation does not occur for any realistic conditions regardless of adiabatic cooling, turbulent fluctuations, or entrainment. For polar marine conditions, binary nucleation does occur due to lower temperatures, and is enhanced due to turbulent fluctuations. An increase in detectable particle sizes (N 3>3 nm), is only seen after multiple boundary layer circulations for conditions of high dimethyl sulphide (DMS) concentrations (400 ppt). Under extreme conditions of entrainment of free-troposphere layers containing very low aerosol condensation sinks and extraordinary high sulphuric acid concentrations (>108 molecules cm−3), increases in detectable particles up to 10,000 cm−3 are predicted only in polar marine air, but are viewed as unlikely to occur in reality. Comparison of model simulations with observed values of DMS and sulphuric acid in polar marine air masses suggest that binary nucleation may lead to an enhancement of ≈1000 cm−3 in N 3 particle concentration, but not to enhancements of ≈10,000 cm−3. Ternary nucleation is predicted to occur under realistic sulphuric acid (1.2 × 107 molecules cm−3) and ammonia (>5 ppt) concentrations; however, significant growth to detectable sizes (N 3) only occurs for DMS concentrations of the order of 400 ppt and very low aerosol condensation sinks, but these conditions are thought to be very infrequent in the MBL and are unlikely to make a significant contribution to the general MBL aerosol concentration. It is plausible that the background MBL aerosol concentration could be maintained by a slow, almost undetectable production rate, and not by noticeable nucleation events where large enhancements in N 3 concentrations are observed. The former requires sustained DMS concentrations of the order of 100 ppt which seems unlikely. In summary, the occurrence of new particles in the unperturbed MBL would be difficult to explain by DMS emissions alone. DMS emissions can explain the occurrence of thermodynamically stable sulphate clusters, but under most conditions, to grow these clusters to detectable sizes before they are scavenged by coagulation, an additional condensable species other than DMS-derived sulphuric acid would be required. In the event, however, of significant removal of the preexisting aerosol due to precipitation, the MBL aerosol can be replenished through growth of new particle formed through ternary nucleation under moderately high DMS concentrations.

 

Calculated trends and the atmospheric abundance of 1,1,1,2-tetrafluoroethane, 1,1-dichloro-1-fl Calculated trends and the atmospheric abundance of 1,1,1,2-tetrafluoroethane, 1,1-dichloro-1-fl

Date added: 08/07/1998
Date modified: 07/27/2009
Filesize: 686.34 kB

Simmonds, P.G., O’Doherty, S., Huang, J., Prinn, R., Derwent, R.G., Ryall, D.B., Nickless, G., and Cunnold D., 1998: Calculated trends and the atmospheric abundance of 1,1,1,2-tetrafluoroethane, 1,1-dichloro-1-fluoroethane, and 1-chloro-1,1-difluoroethane using automated in situ gas chromatography-mass spectrometry measurements recorded at Mace Head, Ireland from October 1994 to March 1997. J. Geophysical Research, 103, 16029-16037.


Abstract


The first in-situ measurements by automated gas chromatograph-mass spectrometer are reported for 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1-dichloro-1-fluoroethane, (HCFC-141b), and 1-chloro-1,1 -difluoroethane, (HCFC-142b). These compounds are steadily replacing the chlorofluorocarbons (CFCs) as refrigerants, foam-blowing agents, and solvents. The concentrations of all three compounds are shown to be rapidly increasing in the atmosphere, with 134a increasing at a rate of 2.05 ± 0.02 ppt yr-1 over the 30 months of observations. Similarly, 141b and 142b increased at rates of 2.49 + 0.03 and 1.24 ± 0.02 ppt yr-1, respectively, over the same period. The concentrations recorded at the atmospheric research station at Mace Head, Ireland, on January 1, 1996, the midpoint of the time series, were 3.67 ppt (134a),7.38 ppt (141b), and 8.78 ppt (142b). From these observations we optimally estimate the HCFC and HFC emissions using a 12-box global model and OH concentrations derived from global 1,1,1-trichloroethane (CCl3CH3) measurements. Comparing two methods of estimating emissions with independent industry estimates shows satisfactory agreement for 134a and 141b, while for 142b, industry estimates are less than half those required to explain our observations.

 

Bromine oxide in the mid-latitude marine boundary layer Bromine oxide in the mid-latitude marine boundary layer

Date added: 08/07/2004
Date modified: 07/27/2009
Filesize: 153.87 kB

Saiz-Lopez, A., J. M. C. Plane, and J. A. Shillito (2004), Bromine oxide in the mid-latitude marine boundary layer, Geophys. Res. Lett., 31, L03111, doi:10.1029/2003GL018956.


Abstract


We report direct observations of bromine oxide (BrO) in the mid-latitude marine boundary layer (MBL), using long-path Differential Optical Absorption Spectroscopy (DOAS). The measurements were made at the Mace Head observatory on the west coast of Ireland. Over six days of observations, the BrO concentration varied from below the detection limit (≈0.8 parts per trillion (ppt)) at night, to a maximum daytime concentration of 6.5 ppt. At the average daytime concentration of 2.3 ppt, BrO causes significant O3 depletion in the MBL through catalytic cycles involving the iodine oxide and hydroperoxy radicals, and also oxidises dimethyl sulfide much more rapidly than the hydroxyl radical. A post-sunrise pulse of BrO was observed, consistent with the build up of photolabile precursors produced by heterogeneous reactions on sea-salt aerosol during the previous night. This indicates that significant bromine activation occurs over the open ocean.

 

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

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

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


Abstract


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

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Boundary layer and aerosol evolution during the 3rd Lagrangian experiment of ACE-2 Boundary layer and aerosol evolution during the 3rd Lagrangian experiment of ACE-2

Date added: 08/31/2000
Date modified: 07/23/2009
Filesize: 952.82 kB

Wood, R., D. Johnson, S. Osborne, M. O. Andreae, B. Bandy, T. S. Bates, C. O'Dowd, P. Glantz, K. Noone, P. K. Quinn, J. Rudolph, and K. Suhre, Boundary layer and aerosol evolution during the 3rd Lagrangian experiment of ACE-2. Tellus, 2000. 52B: p. 401-422.


Abstract


Aircraft measurements are presented of the Lagrangian evolution of a marine boundary layer over a 30-h period during the ACE-2 field campaign. At the start of the  observational period,a 500-m deep polluted marine internal boundary layer (MIBL) was overlain by the remnants of a polluted continental boundary layer extending to around 2 km below a clean, dry free troposphere. The MIBL grew rapidly to a thickness of 900–1000 m in response to increasing sea surface temperatures. No significant aerosol spectral evolution was observed in the boundary layer. Low concentrations of SO2 were observed in the MIBL suggesting that the air mass contained relatively aged aerosol. Aerosol spectra show a broad mode with a modal diameter of around 0.1 mm. The polluted layer between the MIBL and the unpolluted free troposphere was only weakly and intermittently turbulent which prevented significant entrainment of clean air into the polluted layer from aloft. The polluted layer depth was thus controlled mainly by subsidence which as a result becomes shallower, decreasing from over 2000 m to around 1200 m during the observational period. The aerosol characteristics of the polluted layer were similar to those in the MIBL and so although the MIBL entrained considerable amounts of air from above the MIBL the aerosol characteristics underwent no significant change. This has important implications for the rate at which a polluted continental air mass is converted to a clean marine one. The dataset should prove useful in the validation of the modelling of continental pollution outbreaks.

Black carbon measurements at Mace Head, 1989–1996 Black carbon measurements at Mace Head, 1989–1996

Date added: 07/31/1997
Date modified: 07/27/2009
Filesize: 625.86 kB

W.F. Cooke., Jennings, S.G., and Spain, T.G. (1997) Black-carbon measurements at Mace Head, 1989-1996, J. Geophys. Res.,102, 25, 339-25, 346.


Abstract


Black carbon mass concentrations have been measured using an aethalometer at Mace Head on the west coast of Ireland on an almost continuous basis from February 1989 to June 1996. The purpose of this paper is to report on the monthly averaged black carbon concentration at this site over the 7 year period and to examine the influence of air mass on the black carbon mass concentration. The seasonal variation of black carbon mass concentration for clean marine and continental air masses is also investigated.

Black carbon aerosol and carbon monoxide in European regionally polluted air masses at Mace Head, Ireland during 1995–1998 Black carbon aerosol and carbon monoxide in European regionally polluted air masses at Mace Head, Ireland during 1995–1998

Date added: 07/31/2001
Date modified: 07/27/2009
Filesize: 364.88 kB

Derwent, R.G., Ryall, D.B., Jennings, S.G., Spain, T.G., and Simmonds, P.G. (2001). Black carbon aerosol and carbon monoxide in European regionally polluted air masses at Mace Head, Ireland during 1995-1998. Atmos. Environ., 35, 6371-6378.


Abstract


Continuous measurements of black carbon aerosol (BCA) at the Mace Head Atmospheric Research Station on the Atlantic Ocean coast of Ireland show the occurrence of dramatically elevated concentrations when regionally polluted air masses are advected to the station. These occurrences correlate well with similar elevations in carbon monoxide and a wide range of other trace gases monitored near-simultaneously with the BCA. Using daily sector allocation and a sophisticated Lagrangian dispersion model, two independent estimates of the European emission source strength of BCA that are required to explain the Mace Head observations have been made. The best estimates of the UK and European emission source strengths of BCA are 46±14 and [(482-511)±140]x103 tonnes/yr, respectively, and these estimates compare favourably with published inventories, at least to within ±25%, though they are considerably smaller than the emissions employed in some early global climate model studies.

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

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

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


Abstract


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

Biogenic sulphur emissions and inferred non-sea-salt-sulphate CCN around Antarctica Biogenic sulphur emissions and inferred non-sea-salt-sulphate CCN around Antarctica

Date added: 08/06/1997
Date modified: 07/01/2009
Filesize: 1.53 MB

O'Dowd, C. D., J. A. Lowe, M. H. Smith, B. Davison, C. N. Hewitt, and R. M. Harrison (1997), Biogenic sulphur emissions and inferred non-sea-salt-sulphate cloud condensation nuclei in and around Antarctica, J. Geophys. Res., 102(D11), 12,839–12,854.


Abstract


Accumulation mode aerosol properties and biogenic sulphur emissions over the South Atlantic and Antarctic Oceans are examined. Two contrasting air masses, polar and maritime, each possessing distinct aerosol properties, were encountered during the summer months. By examining aerosol volatile properties, polar air masses arriving from the Antarctic continent were shown to consist primarily Of H2SO4 in the accumulation mode size range, with inferred NH+ 4 to SO= 4 molar ratios close to zero. By comparison, air masses of temperate maritime origin were significantly neutralized with molar ratios of ≈1. These results suggest a deficit of ammonia in polar air masses compared with that in maritime air masses. Dimethyl sulphide (DMS) exhibited no correlation with its putative aerosol oxidation products, although spatial coherence in atmospheric concentrations of DMS, methane sulphonic acid (MSA), and non-sea-salt (nss)-sulphate mass was observed. Volatility analysis, used to infer nss-sulphate cloud condensation nuclei (nss-sCCN) active at a supersaturation of ≈0.2%, indicates that nss-sCCN mass and number concentration were best correlated with MSA mass (r≈0.63). Aerosol volatility identified the presence of MSA in submicron non-sea-salt aerosol; however, its contribution to the aerosol mass was small relative to the contribution of sulphuric acid and ammonium bisulphate/sulphate aerosol. The marine sulphur cycle appears strongly coupled to the sea-salt cycle with, typically, 80–90% of nss-sulphate thought to be internally mixed with sea-salt aerosol. During the austral Summer of 1992/1993, a period of strong biological productivity in the Weddell Sea and sub-Antarctic Ocean, particularly during ice-melt, the cruise-average DMS flux of 61 μg m−2 d−1 corresponded to a very modest average nss-sCCN concentration of 21 cm−3. Observed peak values of DMS flux and inferred nss-CCN concentrations during the cruise were 477 μg m−2 d−1 and 64 cm−3, respectively. Events of new particle formation were identified in the Weddell Sea and occurred under conditions of high DMS flux and low aerosol surface area.

 

Biogenic iodine emissions and identification of end products in coastal ultrafine particles during nucleation bursts Biogenic iodine emissions and identification of end products in coastal ultrafine particles during nucleation bursts

Date added: 07/31/2002
Date modified: 07/27/2009
Filesize: 703.95 kB
J.M. Mäkelä, T. Hoffmann, C. Holzke, M. Väkevä, T. Suni, T. Mattila, P.P. Aalto, U. Tapper, E.I. Kauppinen and C.D. O'Dowd, Biogenic iodine emissions and identification of end products in coastal ultrafine particles during nucleation bursts. J. Geophys. Res. 107, 10.1029/2001JD000580,

Abstract


Ultrafine particles sampled during new particle formation bursts observed in the coastal zone were studied with transmission electron microscopy (TEM) and elemental analysis using energy-dispersive X ray (EDX). It was observed that both iodine and sulphur were present in the new particles with diameter below 10 mn. Gaseous emissions of halogen compounds from seaweeds were also measured at the same location during low-tide particle nucleation episodes. Based on the presence of iodine in the particle phase during low-tide nucleation bursts, and the significant emission of iodine compounds from the seaweeds during these periods, it is apparent that part of the biogenic iodine species emitted from the seaweeds end up in the ultrafine particulate phase. It was not possible to quantitatively determine the iodine content in the particles; however, in most cases the relative contribution from iodine and sulphate was similar, while some cases indicated no sulphate. On larger sized particles the contribution of sulphate was significantly higher than iodine. It appears that the condensable species leading to the appearance of new particles in the coastal atmosphere is an iodine species. Whether or not this iodine species also participates in the nucleation of new stable clusters could not be completely verified.

Biogenic fluxes of halomethanes from Irish peatland ecosystems Biogenic fluxes of halomethanes from Irish peatland ecosystems

Date added: 08/06/2001
Date modified: 07/01/2009
Filesize: 278.07 kB

Dimmer, C.H., P.G. Simmonds, G.N. Nickless, and M.R. Bassford, Biogenic fluxes of halomethanes from Irish Peatland Ecosystems, Atmos. Environ., 35(2), 321-330, 2001, (Ser. No. ACP108)


Abstract


Irish peatland ecosystems have been shown to be important sources of low molecular weight halocarbons. Emission of CH3Br, CH3Cl, CH3I and CHCl3 was recorded from all peatland sites monitored, with minor flux of other halocarbons at certain sites. Fluxes were found to be highly linked to incident light, with strong diurnal cycles recorded at all open peatland sites. Estimates of halomethane emissions, particularly from coastal peatland and conifer plantation forest floor sites, suggests that these ecosystems may make a significant contribution to the global budgets of several important halocarbons. Global annual fluxes of 4.7 (0.1-151.9), 0.9 (0.1-3.3), 5.5 (0.9-43.4), and 1.4 (0.1-12.8) Ggyr-1 for CHCl3, CH3Br, CH3Cl, and CH3I, respectively, were determined for peatland ecosystems.

 

Biogenic coastal aerosol production and its influence on aerosol radiative properties Biogenic coastal aerosol production and its influence on aerosol radiative properties

Date added: 07/31/2001
Date modified: 07/27/2009
Filesize: 562.71 kB
O'Dowd, C.D., Biogenic coastal aerosol production and its influence on aerosol radiative properties, J. Geophys. Res., 106, 1545-1550, 2001

Abstract


Coastal zones have been shown to provide a massive source of new, tidal-related, aerosol particles in the atmospheric boundary layer with concentrations exceeding 1,000,000 cm−3 during nucleation bursts sustained over many hours [O Dowd, 200O]. While coastal regions are very strong sources of natural aerosol particles, hithertofore, it has not been demonstrated that these particles contribute to aerosol-related radiative flux. In this brief report, evidence is presented for growth of these new particles, following tidal-related particle formation, into radiatively active particle sizes (i.e. radius>50 nm) where an increase in concentration of more than 300% can be seen. This increase of radiatively active particles concomitantly results in more than a threefold enhancement in both aerosol scattering ability (thereby influencing direct radiative flux) and cloud condensation nuclei (CCN) availability (thereby influencing indirect radiative flux). These results provide direct evidence for coastal biogenic emissions significantly enhancing the radiative flux potential of atmospheric aerosols.

Biogenic aerosol formation in the boreal forest Biogenic aerosol formation in the boreal forest

Date added: 07/31/2000
Date modified: 07/01/2009
Filesize: 469.52 kB

Kulmala, M. K. Hämeri, J.M. Mäkelä, P. P. Aalto, L. Pirjola, M. Väkevä, E. D. Nilsson, I.K.Koponen, G. Buzorius, P. Keronen, g. Rannik, L. Laakso, T. Vesala, K. Bigg, W. Seidl, R. Forkel, T. Hoffmann, J. Spanke, R. Jansson, M. Shimmo, H-C. Hansson, C.D. O'Dowd, E. Becker, J. Paatero, K. Teinilä, R. Hillamo, amd Y. Viisanen, Biogenic aerosol formation in the boreal forest, Boreal Environment Research, 4, 279-280, 2000


Abstract


Aerosol formation and subsequent particle growth in the ambient air have been frequently observed at the boreal forest site (SMEAR II station), southern Finland. The EU funded project BIOFOR (Biogenic aerosol formation in the boreal forest) has focused on a) the determination of formation mechanisms of aerosol particles in the boreal forest site, and b) the verification of emissions of secondary organic aerosols from the boreal forest site, including the quantification of the amount of condensable vapours produced in photochemical reactions of biogenic volatile organic compounds (BVOC) leading to aerosol formation. Although the exact formation route for 3 nm particles is still unclear, the project results can be summarised as follows: (i) The most probable formation mechanism is ternary nucleation (water-sulphuric acid-ammonia) and the growth to observable sizes is mainly due to condensation of organic vapours. However, we do not have a direct proof of these phenomena, since it is impossible to determine the composition of 1 to 5-nm-size particles using the present state-of-art instrumentation; (ii) If nucleation takes place, it always occurs in cold-air advection in polar and Arctic air masses at low cloudiness, and the nucleation is closely connected to the onset of strong turbulence, convection, and entrainment in the morning-noon transition from a stable to an unstable stratified boundary layer; (iii) The emissions rates for several gaseous compounds have been verified. The model calculations showed that the amount of the condensable vapour needed for observed growth of aerosol particles is in the range 1–5 x 107 cm–3. The estimations for the vapour source rate are in the range 3–8 x 104 cm–3s–1.

Behavior of ultrafine particles in continental and marine air masses at a rural site in the Uni Behavior of ultrafine particles in continental and marine air masses at a rural site in the Uni

Date added: 08/06/2000
Date modified: 07/09/2009
Filesize: 1.44 MB

Coe H., P. I. Williams, G. McFiggans, M. W. Gallagher, K. M. Beswick, K. N. Bower and T. W. Choularton Behavior of ultrafine particles in continental and marine air masses at a rural site in the United Kingdom. J. Geophys. Res., 105, 26891-26905, 2000


Abstract


Particle size distribution measurements were made at a coastal site in the United Kingdom. These are presented, and the behavior of recently formed ultrafine particles is discussed. No ultrafine particles were observed in maritime air masses; however, 3 to 7 nm particles were frequently observed at enhanced concentrations when the wind direction was from the land. Their formation was favored at lower temperatures, when 1 ppbv or more of SO2 was present and in air masses that had not been aged extensively. On days when enhanced ultrafine particle concentrations were observed, 3 nm particles increased sharply in the morning, approximately 30 to 90 min after the UV solar flux first increased. By early afternoon the ultrafine particle concentration had returned to background levels. Rapid measurements of 5 nm particles showed no correlation with turbulence parameters, although the boundary layer mixing scales were similar to growth times of freshly nucleated particles to 5 nm diameter. However, ultrafine particle concentrations do correlate with the availability of sulphuric acid vapor. A delay of approximately an hour between the increase of H2SO4 in the morning and a large increase in ultrafine particle concentrations is due to the growth of particles to observable sizes, not the nucleation process itself. An analysis of the timescales for growth showed that coagulation may be important immediately after the particles have nucleated but its effectiveness reduces as number concentration falls. Conversely, growth by condensation is initially slow due to the Kelvin effect but increases in importance as the particles reach observable sizes.

 

Backscatter and extinction measurements in cloud and drizzle at CO2 laser wavelengths Backscatter and extinction measurements in cloud and drizzle at CO2 laser wavelengths

Date added: 07/31/1986
Date modified: 06/30/2009
Filesize: 1.09 MB

Jennings, S.G. (1986). - Backscatter and extinction measurements in cloud and drizzle at CO2 laser wavelengths. Appl. Opt., 25, 2499 - 2505.


Abstract


The backscatter and extinction of laboratory generated cloud and drizzle sized drops have been measured at CO2 laser wavelengths (predominately at λ = 10.591 µm). Measurements of volume backscatter coefficient σb and volume extinction coefficient σe for laboratory cloud of predominantly <20-µm radius droplets are dependent on the form of the size distribution in agreement with numerical prediction. For drops of >˜20 µm at λ = 10.591 µm the relation between σe and σb has the appealingly simple size distribution independent form of σeb =8π/G,[equation] is the asymptotic value of the backscatter gain, where n and k are the real and imaginary indices of refraction. The linear relation is in good agreement with extinction and backscatter measurements made on laboratory generated drizzle sized drops (r > 20 µm). This suggests that the extinction coefficient at CO2 laser wavelengths could be inferred from lidar backscatter return signals without requiring knowledge of the size distribution for drizzle and spherical precipitation sized water drops.

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

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

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


Abstract


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

Backround Bioaerosol Measurements at Mace Head Backround Bioaerosol Measurements at Mace Head

Date added: 08/26/1998
Date modified: 07/27/2009
Filesize: 113.15 kB

Kenny, C.M., and Jennings, S.G. (1998). Background bioaerosol measurements at Mace Head. J. Aerosol Sci., 29, S779-S780.


Abstract


Primary biological aerosol particles consist of airborne viable or non-viable material which are an ubiquitous component of the atmospheric aerosol. The types of particles considered as bioaerosols cover a very large size range, smallest in size are viruses (- 0.005 pm < radius< - 0.25 pm); larger particles include bacteria (r > - 0.2 pm), algae spores and fungi (r > - 0.5 pm) and pollen grains (r > - 5 pm), (Macher, 1993). Plant debris like leaf litter, parts of insects and human and animal epithhelial cells have a supposed r > - 1 pm. Assessment of bioaerosols is generally more complicated than that of non-bioaerosols - for example bioaerosol viability may be affected by a variety of stresses (desiccation, radiation, oxygen toxicity, chemical pollutants etc.) in the environment. A background bioaerosol measurement programme is currently taking place at the Mace Head Atmospheric Field Research Station, Carna, Co. Galway. Effective biological analysis of airborne particles requires samplers operating at a high flow rate and with the capability of concentrating the air particles into a fairly small liquid volume. Use has been made of a glass Aerojet cyclone high volume sampler which has been proven to be successful for the collection of bioaerosol material. Cyclones with spray wetters have been found to be gentle with airborne microorganisms and help to maintain cell viability levels. Utilising a blue protein dye,  uantitative determination of the percentage biological and non-biological species present in the aerosol has been made. The  staining solution reacts with the carboxyl group of a protein and therefore stains the protein-containing or biological particles blue. Non-biologicals are not changed by the stain. Under the light microscope the effects of the protein dye on different particle types can be seen and biological particles can be classified by their characteristic morphology and size. Filters have been examined using a Leitz microscope (Laborlux S), equipped with a 10x ocular lens and an objective lens, Plan 40, and size distribution spectra of the bioaerosol species have been measured. The samples were evaluated into size classes (3.5 urn < diameter < 40 urn) and size distributions of the total aerosol were obtained. The percentages of biological particles in the corresponding size classes are shown in Figure 1. The highest percentage of total biological particles < 10 urn occurs during the modified marine periods 07/25/97 and 07/l l/97 which reflects the passage of the air mass over land. The marine sample 07/15/97 shows a consistently high percentage of biological particles over the larger size ranges. The two predominant peaks occuring during the marine period 07/04/97 are caused by spores. Coupling size distribution spectra with corrected fluorescence spectra of the same air sample yield quantitative effective fluorescence cross-section per unit volume of background air. Analysis of size distribution spectra of the total aerosol, will be presented for both maritime and polluted air.

Averaging periods for indoor-outdoor ratios of pollution in naturally ventilated non-domestic buildings near a busy road Averaging periods for indoor-outdoor ratios of pollution in naturally ventilated non-domestic buildings near a busy road

Date added: 08/01/2003
Date modified: 06/30/2009
Filesize: 387.68 kB

Ni Riain, C, Mark, D., Davies, M., Harrison, R.M. and Byrne, M.A. Averaging periods for indoor-outdoor ratios of pollution in naturally ventilated non-domestic buildings near a busy road. Atmos Env, Vl 37, pp 4121-4132 , 2003.


Abstract

 

Continuous measurements of carbon monoxide (CO) and particulate matter (PM10, PM2.5 and PM1) were made inside and outside two naturally ventilated (NV) and two mechanically assisted (MV) spaces overlooking the same six-lane highway in Central London. The indoor/outdoor (I/O) ratio was calculated for each site for the whole monitoring period in the usual way, and then cumulatively at each hourly time-step from the start of monitoring up to the whole period in order to track the evolution of the I/O ratio with length of monitoring or averaging period. Hourly data were also sorted by wind speed and direction and I/O ratios calculated for each direction/speed set from ensemble means. I/O ratios for the whole period were generally lower in the NV spaces than the MV, however, the indoor-outdoor relationship in the NV spaces was found to vary substantially with wind direction. For a constant above-roof wind speed, I/O ratios of CO varied by 50-60% about the mean value with direction, and by 20-30% for particulate matter. Consequently, I/O ratios for NV spaces depended on the distribution of wind direction within the calculation period and, hence, on the length of monitoring period. The I/O ratio in one NV space changed by a factor of three between the early stages and final stages of monitoring, with a stable final value (±5%) achieved after 900 h of monitoring. By contrast, in the MV spaces under constant fan speed, constant values for the I/O ratio were achieved for CO within 4 h of the start of monitoring. It is argued here that field assessments of the filtration performance of naturally ventilated spaces need to consider exposure to and distribution of natural ventilation drivers within the monitoring period in order to draw meaningful comparisons for design and exposure assessment purposes.

Attenuated total Reflectance Measurements of the complex refractive index of polystyrene latex at CO2 laser wavelengths Attenuated total Reflectance Measurements of the complex refractive index of polystyrene latex at CO2 laser wavelengths

Date added: 07/31/1981
Date modified: 06/30/2009
Filesize: 1.62 MB
Jennings, S.G. (1981)- Attenuated total Reflectance Measurements of the complex refractive index of polystyrene latex at CO2 laser wavelengths. J. Opt. Soc. Amer., 71, 923-927.
Abstract

 

Attenuated total reflectance (ATR) measurements of the complex refractive index m of 5, 10,15, 20, and 30% water suspensions of polystyrene latex are presented for CO2 laser wavelengths (measurements for the 30% suspension are for X =10.591 ,um only). The use of the Maxwell Garnet mixture rule for the real index and the imaginary index (at X = 9.305 ,um) and an extrapolation scheme for the remaining values of imaginary index yield the values m =
1.709 - 0.07i (X = 9.305 ,tm); m = 1.887 - 0.06i (X = 9.504 Arm); m = 1.705 - 0.04i (X = 9.694 ,um); m = 1.764 - 0.045i (X = 10.591 ,um). ATR measurements of the complex index of water and water-ammonium sulfate solutions are in reasonably good agreement with those previously published.

Attenuated total reflectance measurements of the complex refractive index of kaolinite powder at CO2 laser wavelengths Attenuated total reflectance measurements of the complex refractive index of kaolinite powder at CO2 laser wavelengths

Date added: 07/31/1985
Date modified: 06/30/2009
Filesize: 1.63 MB

Pinnick, R.G., Jennings, S.G., Boice, D.C., and Cruncleton, J.P. (1985). - Attenuated total reflectance measurement of the complex refractive index of kaolinite powder at CO2 laser wavelengths. Appl. Opt., 24, 3274 - 3285.


Abstract

 

Attenuated total reflectance measurements of the complex refractive index of kaolinite powder-air mixtures are made for nine CO2 laser wavelengths. The Maxwell-Garnett effective medium theory and generalizations of it that account for either the shape distribution of kaolinite grains in the medium (in which the grains are approximated by a shape distribution of small arbitrarily oriented ellipsoids) or the size distribution of grains (in which finite grain sizes are accounted for by considering, in addition to the electric dipole interaction, magnetic dipole and electric quadrupole interactions) are used to deduce from these measurements the complex refractive index of kaolinite. Most success is achieved with a generalization which assumes a shape distribution of small ellipsoidal grains but which neglects all but electric dipole interactions. In spectral regions where kaolinite displays very strong absorption (in the 9.6-10-,um spectral region) all effective medium theory solutions for kaolinite refractive index either are plagued with ill-conditioning or are nonphysical. It appears that the attenuated total reflectance method, at least as we have applied it here to loosely packed powders comprised of nonspherical grains, is not suitable for measurement of powders in spectral regions of strong absorption.

Atmospheric Sulphur Levels in Western Ireland Atmospheric Sulphur Levels in Western Ireland

Date added: 08/07/1969
Date modified: 07/27/2009
Filesize: 2.97 MB
O'Connor. TC., Atmospheric Sulphur Levels In Western Ireland, Sulphur in Agriculture, AN Foras Taluntais, Dublin, 1969

Abstract

 

Sulphur compounds can exist in the atmosphere in the solid, liquid or gaseous form, depending on their origin and subsequent history. They have deleterious effect on the health of humans, plants and animals and by their corrosive action on buildings and other materials. They have also been studied for their beneficial effects, for example, the nutrition of plants and other natural processes in soils and weathering. They can also be involved in processes of cloud formation and the geochemistry around the world. Although there have been many studies or atmospheric sulphur levels in polluted areas there is little data available on the natural background concentrations of sulphur dioxide in unpolluted areas in temperate latitudes.

This paper is concerned with some aspects of the atmospheric portion of the natural cycle of sulphur. it describes some investigations into the concentrations of sulphur dioxide at a variety of sites. in Galway city, Sine references to recent paper on specific aspects of the sulpur cycle are also given.

Atmospheric Particles from organic Vapours Atmospheric Particles from organic Vapours

Date added: 08/06/2002
Date modified: 06/30/2009
Filesize: 99.71 kB

O'Dowd, Colin D.; Aalto, Pasi; Hmeri, Kaarle; Kulmala, Markku; Hoffmann, Thorsten, Aerosol formation: Atmospheric particles from organic vapours, Nature, Volume 416, Issue 6880, pp. 497-498 (2002)


Abstract

 

Aerosol particles produced over forested areas may affect climate by acting as nuclei for cloud condensation, but their composition (and hence the chemical species that drive their production) remains an open question. Here we show, to our knowledge for the first time, that these newly formed particles (3-5 nm in diameter) are composed primarily of organic species, such as cis-pinonic acid and pinic acid, produced by oxidation of terpenes in organic vapours released from the canopy.

Atmospheric particle formation events at Värriö measurement station in Finnish Lapland 1998–2002 Atmospheric particle formation events at Värriö measurement station in Finnish Lapland 1998–2002

Date added: 08/01/2004
Date modified: 06/30/2009
Filesize: 683.76 kB

Vehkamäki, H., M. Dal Maso, T. Hussein, R. Flanagan, A. Hyvärinen, J. Lauros, J. Merikanto, P. Mönkkönen, M. Pihlatie, K. Salminen, L. Sogacheva, T. Thum, T. M. Ruuskanen, P. Keronen, P. P. Aalto, P. Hari, K. E. J. Lehtinen, Ü. Rannik, and M. Kulmala. Atmospheric particle formation events at Värriö measurement station in Finnish Lapland 1998–2002. Atmospheric Chemistry and Physics, Vol 4, pp. 2015-2023, 2004.


Abstract

 

During the calendar years 1998-2002, 147 clear 8nm diameter particle formation events have been identified at the SMEAR I station in Värriö, northern Finland. The events have been classified in detail according to the particle formation rate, growth rate, event starting time, different trace gas concentrations and pre-existing particle concentrations as well as various meteorological conditions. The frequency of particle formation and growth events was highest during the spring months between March and May, suggesting that increasing biological activity might produce the precursor gases for particle formation. The apparent 8nm particle formation rates were around 0.1 /cm3s, and they were uncorrelated with growth rates that varied between 0.5 and 10nm/h. The air masses with clearly elevated sulphur dioxide concentrations (above 1.6ppb) came, as expected, from the direction of the Nikel and Monschegorsk smelters. Only 15 formation events can be explained by the pollution plume from these sources.

Atmospheric modeling of high- and low-frequency methane observations Importance of interannuall Atmospheric modeling of high- and low-frequency methane observations Importance of interannuall

Date added: 08/06/2005
Date modified: 07/27/2009
Filesize: 1.92 MB

Chen, Y.-H., and R. G. Prinn (2005), Atmospheric modeling of high- and low-frequency methane observations: Importance of interannually varying transport, J. Geophys. Res., 110, D10303, doi:10.1029/2004JD005542.


Abstract


We compare modeled and observed atmospheric methane (CH4) between 1996 and 2001, focusing on the role of interannually varying (IAV) transport. The comparison uses observations taken at 13 high-frequency (∼hourly) in situ and 6 low-frequency (∼weekly) flask measurement sites. To simulate atmospheric methane, we use the global 3-D chemical transport model (MATCH) driven by NCEP reanalyzed winds at T62 resolution (∼1.8° × 1.8°). For the simulation, both methane surface emissions and atmospheric sink (OH destruction) are prescribed as annually repeating fields; thus, atmospheric transport is the only IAV component in the simulation. MATCH generally reproduces the amplitude and phase of the observed methane seasonal cycles. At the high-frequency sites, the model also captures much of the observed CH4 variability due to transient synoptic events, which are sometimes related to global transport events. For example, the North Atlantic Oscillation (NAO) and El Niño are shown to influence year-to-year methane observations at Mace Head (Ireland) and Cape Matatula (Samoa), respectively. Simulations of individual flask measurements are generally more difficult to interpret at certain sites, partially due to observational undersampling in areas of high methane variability. A model-observational comparison of methane monthly means at seven coincident in situ and flask locations shows a better comparison at the in situ sites. Additional simulations conducted at coarser MATCH resolution (T42, ∼2.8° × 2.8°) showed differences from the T62 simulation at sites near strong emissions. This study highlights the importance of using consistent observed meteorology to simulate atmospheric methane, especially when comparing to high-frequency observations.

 

Atmospheric Methyl Iodide at Cape Grim, Tasmania, from AGAGE Observations Atmospheric Methyl Iodide at Cape Grim, Tasmania, from AGAGE Observations

Date added: 08/05/2003
Date modified: 07/27/2009
Filesize: 264.04 kB

Cohan, D.S., G.A. Sturrock, A.P. Biazar, and P.J. Fraser, Atmospheric methyl iodide at Cape Grim, Tasmania from AGAGE  observations, J. Atmos. Chem., 44, 131-150, 2003.


Abstract


Atmospheric mixing ratios of methyl iodide (CH3I) and other methyl halides have been measured at Cape Grim, Tasmania (41°S, 145°E), since early 1998 as part of the Advanced Global Atmospheric Gases Experiment (AGAGE). This paper analyses about 1700 ambient air CH3I measurements from the 14-month period (March 1998–April 1999). Mixing ratios peaked during the summer, despite faster photolytic loss, suggesting local oceanic emissions were about 2.2–3.6 times stronger in summer than in winter. Back trajectories show that CH3I levels are strongly dependent on air mass origin, with highest mixing ratios in air from the Tasman Sea/Bass Strait region and lowest levels in air originating from the Southern Ocean at higher latitudes. CH3I mixing ratios were not well correlated with other methyl halides in unpolluted marine air. The large variations with season and air mass origin suggest that high frequency, continuous data from key locations will make a significant contribution to the understanding of sources and sinks of this important short-lived atmospheric species.

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

Date added: 08/06/2001
Date modified: 07/27/2009
Filesize: 238.69 kB

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


Abstract


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

 

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

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

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


Abstract

 

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

 

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

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

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


Abstract


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

ATMOSPHERIC MEASUREMENTS OF OH, HO2 ATMOSPHERIC MEASUREMENTS OF OH, HO2

Date added: 08/06/2003
Date modified: 07/09/2009
Filesize: 16.18 kB

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


Abstract


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

Atmospheric inputs of trace metals to the Northeast Atlantic Ocean The importance of southeaste Atmospheric inputs of trace metals to the Northeast Atlantic Ocean The importance of southeaste

Date added: 08/06/2001
Date modified: 07/27/2009
Filesize: 209.3 kB

Spokes et al., 2001 L. Spokes, T. Jickells and K. Jarvis, Atmospheric inputs of trace metals to the northeast Atlantic Ocean: the importance of southeasterly flow, Marine Chemistry 76 (2001), pp. 319–330


Abstract


The study of aerosols and rainwater presented here demonstrates that episodic atmospheric deposition events associated with southeasterly flow are quantitatively significant for large areas of the North Atlantic Ocean. This paper considers aluminium and manganese, with predominantly crustal sources, and lead and zinc, which are mobilised into the atmosphere primarily through anthropogenic activity. High levels of all trace metals are associated with southeasterly flow from Europe as the air passes over heavily populated and industrialised regions before reaching the northeast Atlantic Ocean. Fluxes calculated using the 1% HNO3 acid soluble metal concentration show that, although the climatological norm for this area is westerly flow, short-lived southeasterly transport events dominate the input of trace metals to this ocean region. This material may be toxic to phytoplankton or may be represent a new source of nutrients to the biological community. A significant decrease in atmospheric lead levels in polluted air is seen between June 1996 and May 1997, reflecting the decrease in use of leaded fuels in Europe. Comparing atmospheric flux values to sediment trap metal fluxes shows that the atmosphere represents the dominant source of zinc to the deep ocean, whereas an additional, non-atmospheric, manganese source this required, perhaps from mobilisation of sedimentary material from the continental shelf or long range advection of manganese rich Saharan material.

 

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

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

 

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

Atmospheric Emissions and Trends of Nitrous Oxide Deduced From 10 Years of ALE–GAGE Data Atmospheric Emissions and Trends of Nitrous Oxide Deduced From 10 Years of ALE–GAGE Data

Date added: 08/01/1990
Date modified: 07/27/2009
Filesize: 1.5 MB

R.G. Prinn, D. Cunnold, R. Rasmussen, P. Simmonds, F. Alyea, A. Crawford, P. Fraser, and R. Rosen.  Atmospheric emissions and trends of nitrous oxide deduced from ten years of ALE/GAGE data. J. Geophys. Res., 95, 18369-18385, 1990.


Abstract


We present and interpret long-term measurements of the chemically and radiatively important trace gas nitrous oxide (N2O) obtained during the Atmospheric Lifetime Experiment (ALE) and its successor the Global Atmospheric Gasses Experiment (GAGE). The ALE/GAGE data for N2O comprise over 110,000 individual calibrated real-time air analyses carried out over a 10-year (July 1978-June 1988) time period. These measurements indicate that the average concentration in the northern hemisphere is persistently 0.75+/-0.16 ppbv higher than in the southern hemisphere and that the global average linear trend in N2O lies in the range from 0.25 to 0.31% yr-1, with the latter result contingent on certain assumptions about the long-term stability of the calibration gases used in the experiment. Interpretation of the data, using inverse theory and a 9-box (grid) model of the global atmosphere, indicates that the N2O surface emissions into the 90°N-30°N, 30°N-0°, 0°-30°S, and 30°S-90°S semihemispheres account for about 22-34, 32-39, 20-29 and 11-15% of the global total emissions, respectively.<p>The measured trends and latitudinal distributions are consistent with the hypothesis that stratospheric photodissociation is the major atmospheric sink for N2O, but they do not support the hypothesis that the temporal N2O increase is caused solely by increases in anthropogenic N2O emissions associated with fossil fuel combustion. Instead, the cause for the N2O trend appears to be a combination of a growing tropical source (probably resulting from tropical land disturbance) and a growing northern mid-latitude source (probably resulting from a combination of fertilizer use and fossil fuel combustion). The exact combination of these sources which best fits the data depends on the assumed tropospheric-stratospheric exchange rates for N2O in the northern hemisphere relative to the southern hemisphere. Accepting a theoretically-calculated N2O lifetime of 166+/-16 years due to stratospheric destruction only, we deduce from the ALE/GAGE data a 10-year average global N2O emission rate of (20.5+/-2.4)×1012gN2O yr-1, but with significant year-to-year variations in emissions associated perhaps with year-to-year variations in tropical land disturbance.

Atmospheric Composition Change: Ecosystems - Atmosphere interactions Atmospheric Composition Change: Ecosystems - Atmosphere interactions

Date added: 11/11/2009
Date modified: 11/11/2009
Filesize: 7.78 MB

Fowler, D., K. Pilegaard, M.A. Sutton, P. Ambus, M. Raivonen, J. Duyzer, D. Simpson, H. Fagerli, S. Fuzzi, J.K. Schjoerring, C. Granier, A. Neftel, I.S.A. Isaksen, P. Laj, M.Maione, P.S. Monks, J. Burkhardt, U. Daemmgen, J. Neirynck, E. Personne, R. Wichink-Kruit, K. Butterbach-Bahl, C. Flechard, J.P. Tuovinen, M. Coyle, G. Gerosa, B. Loubet, N. Altimir, L. Gruenhage, C. Ammann, S. Cieslik, E. Paoletti, T.N. Mikkelsen, H. Ro-Poulsen, P. Cellier, J.N. Cape, L. Horváth, F. Loreto, Ü. Niinemets, P. I. Palmer, J.Rinne, P. Misztal, E. Nemitz, D. Nilsson, S. Pryor, M.W. Gallagher, T. Vesala, U. Skiba, N. Brüeggemann, S. Zechmeister-Boltenstern, J. Williams, C. O’Dowd, M. C. Facchini, G. de Leeuw, A. Flossman, N. Chaumerliac, J.W. Erisman, Atmospheric Composition Change: Ecosystems - Atmosphere interactions, Atmos. Environ., doi:10.1016/j.atmosenv.2009.07.068,  2009


Abstract.

Ecosystems and the atmosphere: This review describes the state of understanding the processes involved in the exchange of trace gases and aerosols between the earth’s surface and the atmosphere. The gases covered include NO, NO2, HONO, HNO3, NH3, SO2, DMS, Biogenic VOC, O3, CH4, N2O and particles in the size range 1 nm–10 mmincluding organic and inorganic chemical species. The main focus of the reviewis on the exchange between terrestrial ecosystems, both managed and natural and the atmosphere, although some new developments in ocean–atmosphere exchange are included. The material presented is biased towards the last decade, but includes earlier work, where more recent developments are limited or absent.  New methodologies and instrumentation have enabled, if not driven technical advances in measurement. These developments have advanced the process understanding and upscaling of fluxes, especially for particles, VOC and NH3. Examples of these applications include mass spectrometric methods, such as  Aerosol Mass Spectrometry (AMS) adapted for field measurement of atmosphere–surface fluxes using micrometeorological methods for chemically resolved aerosols. Also briefly described are some advances in theory and techniques in micrometeorology. For some of the compounds there have been paradigm shifts in approach and application of both techniques and assessment. These include flux measurements over marine surfaces and urban areas using micrometeorological methods and the up-scaling of flux measurements using aircraft and satellite remote sensing. The application of a flux-based approach in assessment of O3 effects on vegetation at regional scales is an important policy linked development secured through improved quantification of fluxes. The coupling of monitoring, modelling and intensive flux measurement at a continental scale within the NitroEurope network represents a quantum development in the application of research teams to address the underpinning science of reactive nitrogen in the cycling between ecosystems and the atmosphere in Europe. Some important developments of the science have been applied to assist in addressing policy questions, which have been the main driver of the research agenda, while other developments in understanding have not been applied to their wider field especially in chemistry-transport models through deficiencies in obtaining appropriate data to enable application or inertia within the modelling community. The paper identifies applications, gaps and research questions that have remained intractable at least since 2000 within the specialized sections of the paper, and where possible these have been focussed on research questions for the coming decade.

 

 

Atmospheric Composition Change – Global and Regional Air Quality Atmospheric Composition Change – Global and Regional Air Quality

Date added: 11/11/2009
Date modified: 11/11/2009
Filesize: 9.8 MB

Monks, P.S., C. Granier, S. Fuzzi, A. Stohl, M. Williams, H. Akimoto, M. Amman, A. Baklanov, U. Baltensperger, I. Bey, N. Blake, R.S. Blake, K. Carslaw, O.R. Cooper, F. Dentener, D. Fowler, E. Fragkou, G. Frost, S. Generoso, P. Ginoux, V. Grewe, A. Guenther, H.C. Hansson, S. Henne, J. Hjorth, A. Hofzumahaus, H. Huntrieser, I.S.A. Isaksen, M.E. Jenkin, J. Kaiser, M. Kanakidou, Z. Klimont, M. Kulmala, P. Laj, M.G. Lawrence, J.D. Lee, C. Liousse, M. Maione, G. McFiggans, A. Metzger, A. Mieville, N. Moussiopoulos, J.J. Orlando, C. O'Dowd, P.I. Palmer, D.D. Parrish, A. Petzold, U. Platt, U. Poeschl, A.S.H. Prévôt, C.E. Reeves, S. Reimann, Y. Rudich, K. Sellegri, R. Steinbrecher, D. Simpson, H. ten Brink, J. Theloke, G.R. van der Werf, R. Vautard, V. Vestreng, Ch. Vlachokostas and R. vonGlasow, Atmospheric Composition Change – Global and Regional Air Quality, Atmos. Environ.,  doi:10.1016/j.atmosenv.2009.08.021  , 2009


Abstract.

Air quality transcends all scales with in the atmosphere from the local to the global with handovers and feedbacks at each scale interaction. Air quality has manifold effects on health, ecosystems, heritage and climate. In this review the state of scientific understanding in relation to global and regional air quality is outlined. The review discusses air quality, in terms of emissions, processing and transport of trace gases and aerosols. New insights into the characterization of both natural and anthropogenic emissions are reviewed looking at both natural (e.g. dust and lightning) as well as plant emissions. Trends in anthropogenic emissions both by region and globally are discussed as well as biomass burning emissions. In terms of chemical processing the major air quality elements of ozone, non-methane hydrocarbons, nitrogen oxides and aerosols are covered. A number of topics are presented as a way of integrating the process view into the atmospheric context; these include the atmospheric oxidation efficiency, halogen and HOx chemistry, nighttime chemistry, tropical chemistry, heat waves, megacities, biomass burning and the regional hot spot of the Mediterranean. New findings with respect to the transport of pollutants across the scales are discussed, in particular the move to quantify the impact of long-range transport on regional air quality. Gaps and research questions that remain intractable are identified. The review concludes with a focus of research and policy questions for the coming decade. In particular, the policy challenges for concerted air quality and climate change policy (co-benefit) are discussed.

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

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

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


Abstract


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

Atmospheric carbon dioxide and its stable isotope ratios, methane, carbon monoxide, nitrous oxi Atmospheric carbon dioxide and its stable isotope ratios, methane, carbon monoxide, nitrous oxi

Date added: 08/07/1998
Date modified: 07/27/2009
Filesize: 655.24 kB

Francey, R.J., L.P. Steele, R.L. Langenfelds, C.E. Allison, L.N. Cooper, B.L. Dunse, B.G. Bell, T.D. Murray, H.S. Tait, L. Thompson and K.A. Masarie, Atmospheric carbon dioxide and its stable isotope ratios, methane, carbon monoxide and hydrogen from Shetland Isles, Atmos. Environ., Vol. 32, No. 19, 3331-3338, 1998.


Abstract


Since November 1992, 0.5l glass flasks have been filled approximately monthly with dry marine air from Shetland Isles, Scotland (60.2oN, 1.2oW) and transported to CSIRO, Australia for analyses. The Shetland site is part of a CSIRO global flask network with 10-12 sites, anchored to continuous high precision in situ measurements made at the Australian Cape Grim Baseline Station (40.7oS, 144.7oE), a primary station in the Global Atmosphere Watch programme (GAW) coordinated by the World Meteorological Organisation. The methodology is summarised, and Shetland results for CO2, CH4, N2O, CO, H2 and delta13C, delta18O of CO2 presented for the period 1992-1996. We compare data to available results from surrounding stations of the NOAA cooperative network (in particular Mace Head, Ireland, 53.3oN, 9.9oW), and address issues of both trace species intercalibration and atmospheric spatial gradients. While considerable uniformity of trace-gas composition is evident in oceanic air over a 13o range of latitude, nevertheless anomalies in CO2 concentration and isotopic composition are suggested in samples representing air to the west of Shetland. The potential for remotely monitoring integrated emissions from northern Europe is also identified.

 

Atmospheric bromoform at Mace Head, Ireland seasonality and evidence for a peatland source Atmospheric bromoform at Mace Head, Ireland seasonality and evidence for a peatland source

Date added: 08/07/2005
Date modified: 07/27/2009
Filesize: 692.16 kB

Carpenter, L. J., Wevill, D. J., O'Doherty, S., Spain, G., and Simmonds, P. G.: Atmospheric bromoform at Mace Head, Ireland: seasonality and evidence for a peatland source, Atmos. Chem. Phys., 5, 2927-2934, 2005.


Abstract


In situ atmospheric observations of bromoform (CHBr3) made over a 2.5 year period at Mace Head, Ireland from May 2001- Dec 2003, including during the NAMBLEX (North Atlantic Marine Boundary Layer Experiment) campaign, show broad maxima from spring until autumn and winter minima, with mixing ratios of 5.3+1.0 pptv (mid March - mid October) and 1.8+0.8 pptv (December-February). This indicates that, unlike CHCl3, which has a summer minimum and winter maximum at Mace Head, local biological sources of CHBr3 have a greater influence on the atmospheric data than photochemical decay during long-range transport. The emission sources are predominantly macroalgal, but we find evidence for a small terrestrial flux from peatland ecosystems, which so far has not been accounted for in the CHBr3 budget. Sharp increases in CHCl3 and CHBr3 concentrations and decreases in O3 concentrations occurred at night when the wind direction switched from an ocean- to a land-based sector (land breeze) and the wind speed dropped to below 5 ms-1. These observations infer a shallow atmospheric boundary layer with increased O3 deposition and concentration of local emissions of both CHCl3 and CHBr3. The ratio of ΔCHCl3/ΔCHBr3 varied strongly according to the prevailing wind direction; from 0.60+0.15 in south-easterly (100-170° and northerly (340-20°) air to 2.5+0.4 in north-easterly (40-70°) air. Of these land-sectors, the south-easterly air masses are likely to be strongly influenced by macroalgal beds along the coast and the emission ratios probably reflect those from seaweeds in addition to land sources. The north-easterly airmasses however had an immediate fetch inland, which locally is comprised of coastal peatland ecosystems (peat bogs and coastal conifer plantations), previously identified as being strong sources of atmospheric CHCl3 under these conditions. Although we cannot entirely rule out other local land or coastal sources, our observations also suggest peatland ecosystem emissions of CHBr3. We use correlations between CHCl3 and CHBr3 during the north-easterly land breeze events in conjunction with previous estimates of local wetland CHCl3 release to tentatively deduce a global wetland CHBr3 source of 20.4(0.4-948) Gg yr-1, which is approximately 7% of the total global source.

Atmospheric aerosol measurements at Mace Head, Ireland Atmospheric aerosol measurements at Mace Head, Ireland

Date added: 08/07/2000
Date modified: 07/27/2009
Filesize: 247.74 kB
Jennings S.G., Atmospheric aerosol measurements at Mace Head, Ireland,Journal of Aerosol Science, Volume 31, Supplement 1, September 2000 , pp. 580-583(4)

Abstract


The atmospheric aerosol plays a fundamental role in the earth's atmosphere, involving solid particulate material. Interest in atmospheric aerosol research has increased dramatically in recent years, as evidenced by a rapidly increasing publication rate in the discipline and through an accelerating presence in both national and international conference media. In earlier decades, interest in atmospheric aerosols was mainly because of their effects on visibility. More recently the accelerated interest in aerosols is largely due to their role in climate effects and in atmospheric chemistry processes. This has also been recognised internationally through activities, such as for example the International Global Atmospheric Chemistry (IGAC) Focus on aerosols and the World Meteorological Organisation (WMO), Global Atmospheric Watch (GAW) Aerosol, (WMO, 1997).

One of the largest uncertainties associated with climate forcing relates to the atmospheric aerosol, as noted by the Inter-Governmental Panel on Climate Change (IPCC); Houghton et al., 1995. The atmospheric aerosol shows large variability both in time and in space (Dreiling and Jaenicke, 1994) and is one of the major outstanding uncertainties in atmospheric aerosol research. Recently, there have been increasing studies of the natural aerosol since it is recognised that until natural background aerosol sources are better quantified, the influence of the more pollutant anthropogenic aerosol on climate for example, cannot be fully understood. The Mace Head Atmospheric Research Station has provided a good platform for the performance of a range of atmospheric aerosol studies some of which are summarised in the following pages.

Assessment of changing meteorology and emissions on air quality using a regional climate model: Impact on ozone Assessment of changing meteorology and emissions on air quality using a regional climate model: Impact on ozone

Date added: 03/12/2013
Date modified: 03/12/2013
Filesize: 3.64 MB

Coleman, L. , D. Martin, S. Varghese, S.G. Jennings, C.D. O’Dowd, Assessment of changing meteorology and emissions on air quality using a regional climate model: Impact on ozone, Atmos. Environ., http://dx.doi.org/10.1016/j.atmosenv.2012.11.048, 2012


 

Abstract. A regional climate model is used to assess changes in atmospheric ozone for the years 2030, 2050 and 2100 relative to 2006 brought about by changes in meteorology and emissions. The simulations are evaluated against ozone measurements for 2006, exhibiting good agreement between the model-predicted measurements and the measured annual cycles. Under the RCP6 emission scenario used in these simulations, average ozone mixing ratios are set to reduce by 2.0 ppb over domains encompassing Europe and the North East Atlantic between 2006 and 2100 with the most significant decrease occurring after 2050 due to the pattern in changing emissions. Peak reductions of more than 8 ppb are observed during summer time over mainland Europe by 2100. Model output was studied for three relevant subdomains, namely the North East Atlantic, Ireland and Europe. The relative contribution of changes in both emissions and meteorology is assessed. Over the whole domain, changing emissions are predominantly responsible for changes in surface ozone; although over the North East Atlantic domain, the changing emissions do not perturb surface ozone trends and the decrease in 2100 levels is entirely attributable to changing meteorology.

Application of a compact all solid-state laser system to the in situ detection of atmospheric OH, HO Application of a compact all solid-state laser system to the in situ detection of atmospheric OH, HO

Date added: 08/06/2003
Date modified: 07/27/2009
Filesize: 184.19 kB
W. J. Bloss, T. J. Gravestock, D. E. Heard, T. Ingham,G. P. Johnson and J. D. Lee, "Application of a compact all solid-state laser system to the in situ detection of atmospheric OH, HO2, NO and IO by laser-induced fluorescence", Journal of Environmental Monitoring., 5, 21-28 (2003).

Abstract

 

A tuneable, high pulse-repetition-frequency, solid state Nd:YAG pumped titanium sapphire laser capable of generating radiation for the detection of OH, HO2, NO and IO radicals in the atmosphere by laser induced fluorescence (LIF) has been developed. The integration of the laser system operating at 308 nm into a field measurement apparatus for the simultaneous detection of hydroxyl and hydroperoxy radicals is described, with detection limits of 3.1 6 105 molecule cm23 (0.012 pptv in the boundary layer) and 2.6 6 106 molecule cm23 (0.09 pptv) achieved for OH and HO2 respectively (30 s signal integration, 30 s background integration, signalto- noise ratio ~ 1). The system has been field tested and offers several advantages over copper vapour laser pumped dye laser systems for the detection of atmospheric OH and HO2 radicals by LIF, with benefits of greater tuning range and ease of use coupled with reduced power consumption, instrument footprint and warm-up time. NO has been detected in the atmosphere at y 1 ppbv by single photon LIF using the A 2S1 B X 2P1/2 (0,0) transition at 226 nm, with absolute concentrations in good agreement with simultaneous measurements made using a chemiluminescence analyser. With some improvements in performance, particularly with regard to laser power, the theoretical detection limit for NO is projected to be y 2 6 106 molecule cm23 (0.08 pptv). Whilst operating at 445 nm, the laser system has been used to readily detect the IO radical in the laboratory, and although it is difficult to project the sensitivity in the field, an estimate of the detection limit is v 1 6 105 molecule cm23 (v 0.004 pptv), well below previously measured atmospheric concentrations of IO.

Application of a compact all solid-state laser system to the in situ detection of atmospheric OH, HO Application of a compact all solid-state laser system to the in situ detection of atmospheric OH, HO

Date added: 08/06/2003
Date modified: 06/30/2009
Filesize: 184.19 kB
W. J. Bloss, T. J. Gravestock, D. E. Heard, T. Ingham,G. P. Johnson and J. D. Lee, "Application of a compact all solid-state laser system to the in situ detection of atmospheric OH, HO2, NO and IO by laser-induced fluorescence", Journal of Environmental Monitoring., 5, 21-28 (2003).

Abstract


A tuneable, high pulse-repetition-frequency, solid state Nd:YAG pumped titanium sapphire laser capable of generating radiation for the detection of OH, HO2, NO and IO radicals in the atmosphere by laser induced fluorescence (LIF) has been developed. The integration of the laser system operating at 308 nm into a field measurement apparatus for the simultaneous detection of hydroxyl and hydroperoxy radicals is described, with detection limits of 3.1 6 105 molecule cm23 (0.012 pptv in the boundary layer) and 2.6 6 106 molecule cm23 (0.09 pptv) achieved for OH and HO2 respectively (30 s signal integration, 30 s background integration, signalto- noise ratio ~ 1). The system has been field tested and offers several advantages over copper vapour laser pumped dye laser systems for the detection of atmospheric OH and HO2 radicals by LIF, with benefits of greater tuning range and ease of use coupled with reduced power consumption, instrument footprint and warm-up time. NO has been detected in the atmosphere at y 1 ppbv by single photon LIF using the A 2S1 B X 2P1/2 (0,0) transition at 226 nm, with absolute concentrations in good agreement with simultaneous measurements made using a chemiluminescence analyser. With some improvements in performance, particularly with regard to laser power, the theoretical detection limit for NO is projected to be y 2 6 106 molecule cm23 (0.08 pptv). Whilst operating at 445 nm, the laser system has been used to readily detect the IO radical in the laboratory, and although it is difficult to project the sensitivity in the field, an estimate of the detection limit is v 1 6 105 molecule cm23 (v 0.004 pptv), well below previously measured atmospheric concentrations of IO.

Applicability of condensation particle counters to measure atmospheric clusters Applicability of condensation particle counters to measure atmospheric clusters

Date added: 09/12/2008
Date modified: 07/10/2009
Filesize: 617.3 kB

Sipilä, M., Lehtipalo, K., Kulmala, M., Petäjä, T., Junninen, H., Aalto, P. P., Manninen, H. E., Kyrö, E.-M., Asmi, E., Riipinen, I., Curtius, J., Kürten, A., Borrmann, S., and O'Dowd, C. D.: Applicability of condensation particle counters to measure atmospheric clusters, Atmos. Chem. Phys., 8, 4049-4060, 2008


Abstract


This study presents an evaluation of a pulse height condensation particle counter (PH-CPC) and an expansion
condensation particle counter (E-CPC) in terms of measuring ambient and laboratory-generated molecular and ion clusters. Ambient molecular cluster concentrations were measured with both instruments as they were deployed in conjunction with an ion spectrometer and other aerosol instruments in Hyyti¨al¨a, Finland at the SMEAR II station between 1 March and 30 June 2007. The observed cluster concentrations varied and ranged from some thousands to 100 000 cm−3. Both instruments showed similar (within a factor of 5) concentrations. An average size of the detected clusters was approximately 1.8 nm. As the atmospheric measurement of sub 2-nm particles and molecular clusters is a challenging task, we conclude that most likely we were unable to detect the smallest clusters. Nevertheless, the reported concentrations are the best estimates to date for minimum cluster concentrations in a boreal forest environment.

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