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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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Comparisons of coarse-mode aerosol nitrate and ammonium at two polluted coastal sites Comparisons of coarse-mode aerosol nitrate and ammonium at two polluted coastal sites

Date added: 08/07/2001
Date modified: 07/27/2009
Filesize: 413.74 kB

Yeatman S.G., Spokes L.J., Jickells T.D. (2001) Comparison of coarse mode aerosol nitrate and ammonium at two polluted coastal sites. Atmospheric Environment 35 1321-1335.


Abstract


Direct atmospheric fixed-nitrogen deposition can contribute to eutrophication in coastal and estuarine waters and can be enhanced by heterogeneous reactions between gaseous atmospheric nitrogen species and aerosol sea salt, which increase deposition rates. Size-segregated aerosol samples were collected from two coastal sites: Weybourne, England and Mace Head, Ireland. Major-ion aerosol concentrations were determined and temporal patterns were interpreted with the use of air-mass back trajectories. Low levels of terrestrially derived material were seen during periods of clean, onshore flow, with respective concentration ranges for nitrate and ammonium of 0.47-220 and below detection limit to 340 nmol/m3. Corresponding levels of marine derived material during these periods were high, with sodium concentrations ranging from 39 to 1400 nmol/m3. Highest levels of terrestrially derived material were seen during polluted, offshore flow, where the air had passed recently over strong source regions of the UK and northern Europe, with concentration ranges of nitrate and ammonium of 5.6-790 and 9.7-1000 nmol/m3, respectively. During polluted flow ∼40-60% of the nitrate was found in the coarse mode (>1 μm diameter) and under clean marine conditions almost 100% conversion was seen. In addition, the data suggests strong evidence for dissolution, coagulation processes that also shift nitrate to the coarse mode. Furthermore, such processes are thought also to give rise to the size-shifting of aerosol ammonium, since significant coarse-mode fractions of this species (∼19-45%) were seen at both sites. A comparison of the relative importance of nitrate and ammonium in the overall dry deposition of inorganic fixed-nitrogen at each site indicates that at Weybourne the mass-weighted dry deposition velocity of the latter is around double that seen at Mace Head with its resultant contribution to the overall inorganic nitrogen dry flux exceeding that of nitrate.

 

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

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

Abstract


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

Emission rates of C8–C15 VOCs from seaweed and sand in the inter-tidal zone at Mace Head, Irela Emission rates of C8–C15 VOCs from seaweed and sand in the inter-tidal zone at Mace Head, Irela

Date added: 08/07/2002
Date modified: 07/27/2009
Filesize: 167.86 kB

Emission rates of C8 - C15 VOCs from seaweed and sand in the inter-tidal zone at Mace Head, Ireland (2002) J.H. Sartin, C.J. Halsall, S. Hayward and C.N. Hewitt, Atmospheric Environment , 36, 5311 - 5321


Abstract


Emission fluxes for a range of C8-C15 volatile organic compounds (VOCs) were determined from the seaweed Fucus spiralis (spiral wrack) and an adjacent sand surface during low tide on the coastline of Mace Head, Ireland. These two surface types, assessed using dynamic flux chamber systems, are typical of the Mace Head inter-tidal zone. A range of n-alkanes and oxygenates were routinely identified in the measurement of chamber air. Examination of the odd/even n-alkane ratios and use of the carbon preference index (CPI) suggested a biogenic source for these compounds (CPIs >2 in for all samples). Fluxes of n-pentadecane, the most predominant n-alkane, ranged from 0.2 to 5.1mugm-2h-1 (0.9-24nmolm-2h-1), while oxygenates such as nonanal and decanal had fluxes ranging from <0.1 to 4.4mugm-2h-1 (<0.1-31nmolm-2h-1) and <0.1 to 4.6mugm-2h-1 (<0.1-30nmolm-2h-1), respectively. Seaweed emission rates for n-pentadecane were correlated with photosynthetically active radiation (PAR) (rs=0.94) while emissions from sand showed correlation with temperature (rs=0.85). This suggests a possible biochemical route controlling the release of n-pentadecane from spiral wrack, and temperature-driven volatilisation from sand. Volatilisation from residual seawater trapped in the sand may explain the comparable flux of both n-alkanes and oxygenates from this surface. Unlike the n-alkanes, oxygenate fluxes from sand correlate with PAR, suggesting a photodependent production from organic carbon residues present in seawater. Comparison with previous flux estimates from coastal seawater indicates that the two source types (Fucus spiralis and bare sand) are significant but not dominant sources of these VOCs.

 

Recent Tropospheric Growth Rate and Distribution of HFC-134a (CF3CH2F) Recent Tropospheric Growth Rate and Distribution of HFC-134a (CF3CH2F)

Date added: 08/06/1996
Date modified: 07/23/2009
Filesize: 488.65 kB

Oram, D.E., Reeves, C.E., Sturges, W.T., Penkett, S.A., Fraser, P.J. and Langenfelds, R.L. 1996. Recent tropospheric growth rate and distribution of HFC-134a (CF3CH2F). Geophysical Research Letters 23:1949-1952.


Abstract


Air samples collected at Cape Grim, Tasmania (41°S) between 1978 and 1995, and at Mace Head, Ireland (53°N) between July 1994 and May 1995, have been analysed by GC-MS to determine recent trends of HFC-134a, an important CFC replacement, in the background atmosphere. Until 1990, the concentration of HFC-134a at Cape Grim was below detection limits, the first quantifiable level (0.01 pptv) appearing in May 1990. Between 1992 and mid-1995 the concentration grew exponentially at ∼200 % yr-1 with the concentration at the end of 1994 reaching 0.43 pptv. At Mace Head, HFC-134a grew at a rate of 1.24 ± 0.11 pptv yr-1 between July 1994 and May 1995, with the concentration at the end of 1994 being 1.48 pptv. In the absence of industrial production and release estimates for HFC-134a, the observations have been used in conjunction with a 2-D global model to estimate recent emissions. The model indicates that significant emissions (250 tonnes) began in 1991, increasing rapidly to a level of ∼8 ktonnes in 1994.

 

A dedicated study of New Particle Formation and Fate in the Coastal Environment (PARFORCE): Overview A dedicated study of New Particle Formation and Fate in the Coastal Environment (PARFORCE): Overview

Date added: 08/01/2002
Date modified: 07/21/2009
Filesize: 448.25 kB
O’Dowd, C. D., et al., A dedicated study of New Particle Formation and Fate in the Coastal Environment (PARFORCE):Overview of objectives and achievements, J. Geophys. Res., 107(D19), 8108, doi:10.1029/2001JD000555, 2002Overview of objectives and achievements, J. Geophys. Res., 107(D19), 8108, doi:10.1029/2001JD000555, 2002

Abstract


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

A detailed case study of isoprene chemistry during the EASE96 A detailed case study of isoprene chemistry during the EASE96

Date added: 08/05/2000
Date modified: 07/27/2009
Filesize: 349.47 kB

Carslaw, N., N. Bell, A.C. Lewis, J.B. McQuaid, and M.J. Pilling, 2000: A detailed case study of isoprene chemistry during the EASE96 Mace Head campaign. Atmos. Environ., 34, 2827-2836, doi:10.1016/S1352-2310(00)00088-1.


Abstract


A detailed chemical mechanism has been used in conjunction with high-quality field measurements in order to assess the potential role of isoprene at a clean coastal Northern Hemisphere site. The importance of isoprene as a source of peroxy radicals, formaldehyde and ozone is discussed in some detail for a case study day (July 17 1996). Between 10:00 and 16:00h GMT, isoprene accounts on average for 15% of the OH removal, yet is responsible for the production of about 30% of the HO2 radicals. Isoprene is also responsible for between 40-60% of the HCHO formation, and 20-40% of the 2 ppb h-1 conversion of NO to NO2 by peroxy radicals. We discuss the significant time lag between HCHO formation and destruction, a time lag that must be accounted for in order to accurately calculate the rate of HO2 production from isoprene degradation, and the implications of the isoprene oxidation for atmospheric chemistry.

 

Statistical characteristics and predictability of particle formation events at Mace Head Statistical characteristics and predictability of particle formation events at Mace Head

Date added: 08/01/2006
Date modified: 07/23/2009
Filesize: 498.16 kB
Yoon, Y.J., C.D. O’Dowd, S.G. Jennings, S.H. Lee, Statistical characteristics and predictability of particle formation events at Mace Head, J. Geophys. Res.,doi:10.1029/2005JD006284, 2006.

Abstract


The seasonal characteristics of coastal nucleation events at the Mace Head Atmospheric Research Station, resulting from exposure of macroalgae to the atmosphere, were analyzed for a 2-year period from August 2002 to July 2004. Nucleation events occurred on 58% of the days over the period. The seasonal variation of the number of event days and event duration show a clear cycle, with maximum values in spring and autumn and the minimum values in the winter season. The nucleation events typically start ∼75 min prior to the occurrence of the low-tide mark and the event start time is correlated (r = 0.75) to the low-tide height. The intensity of the events, as determined by the peak particle concentrations achieved, is also positively correlated with the amount of tidal areas exposed to ambient air, as determined by the tidal height, and solar radiation. A nucleation potential index (NPI) was developed as a tool to provide a predictive capability for event prediction at Mace Head. The index was derived from normalized tidal height, solar radiation intensity, and wind direction and was compared with the occurrence of nucleation events from the database. The result shows that Mace Head particle formation events can be quite well predicted with a threshold probability of 50%.

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.

 

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

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

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


Abstract


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

 

Ionization Equibrium of maritime Air Ionization Equibrium of maritime Air

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

Novel Biogenic Iodine-Containing Trihalomethanes and Other Short-Lived Halocarbons in the Coast Novel Biogenic Iodine-Containing Trihalomethanes and Other Short-Lived Halocarbons in the Coast

Date added: 08/06/2000
Date modified: 07/23/2009
Filesize: 1.05 MB

Carpenter, L. J., G. Malin, P. S. Liss, and F. C. Küpper (2000), Novel Biogenic Iodine-Containing Trihalomethanes and Other Short-Lived Halocarbons in the Coastal East Atlantic, Global Biogeochem. Cycles, 14(4), 1191–1204.


Abstract


Reactive halogen photochemistry and its impact on tropospheric oxidant levels have recently attracted intense research interest following the observation of the iodine oxide radical at midlatitudes. During September 1998, short-lived organoiodines including CH3I, C2H5I, CH2ICl, CH2IBr, CH2I2, and the hitherto undetected CHIBr2, as well as the organobromines CHBr3, CH2Br2, CHBr2Cl, CH3Br, and C2H5Br, were measured in air and seawater at and around Mace Head, on the west coast of Ireland. The release rates of organic bromines and iodines from seaweeds were determined from incubations of 10 species of brown, red, and green macroalgae collected in the intertidal or subtidal zones of the rocky shore. For all the brown algae studied, iodine was released mainly as CH2I2. However, for several seaweeds, the novel iodine-containing trihalomethanes CHIBr2 and CHI2Cl represented a significant fraction of the released organic iodine. The macroalgae incubation experiments as well as monitoring of the in situ concentrations in a rock pool indicated that natural halocarbon production by seaweeds was stimulated by incident light. The halocarbon fluxes derived from the seaweed incubations, coupled with published detailed biomass surveys, enabled coastal organohalogen seawater concentrations to be estimated. The CHBr3, CH2Br2, and CHBr2Cl concentrations calculated by this method compared well with coastal surface seawater measurements, implying that macroalgae were the major sources of the polybromomethanes. Measured CH3Br, CH3I, and CH2ICl levels were higher than calculated, which may be due to the existence of additional sources. CH3Br production by macroalgae accounted for less than 10% of measured levels in coastal waters. Short-lived iodocarbons such as CH2I2 and CHIBr2 were depleted in surface seawater compared to calculated levels, implying their photolytic loss within the upper water column.

 

Role of organic and black carbon in the chemical composition of atmospheric aerosol at European background sites Role of organic and black carbon in the chemical composition of atmospheric aerosol at European background sites

Date added: 08/01/2001
Date modified: 07/23/2009
Filesize: 205.08 kB

Krivacsy, Z., Hoffer, A., Sarvari, Zs., Temesi, D., Baltensperger, U., Nyeki, S., Weingartner, E., Kleefeld, S., Jennings, S.G., 2001. Role of organic and black carbon in the chemical composition of atmospheric ,aerosol at European background sites. Atmospheric Environment 35, 6231-6244.


Abstract


The mass concentrations of inorganic ions, water-soluble organic carbon, water-insoluble organic carbon and black carbon were determined in atmospheric aerosol collected at three European background sites: (1) the Jungfraujoch, Switzerland (high-alpine, PM2.5 aerosol); (2) K-puszta, Hungary (rural, PM1.0 aerosol); (3) Mace Head, Ireland (marine, total particulate matter). At the Jungfraujoch and K-puszta the contribution of carbonaceous compounds to the aerosol mass was higher than that of inorganic ions by 33% and 94%, respectively. At these continental sites about 60% of the organic carbon was water soluble, 55-75% of the total carbon proved to be refractory and a considerable portion of the water soluble, refractory organic matter was composed of humic-like substances. At Mace Head the mass concentration of organic matter was found to be about twice than that of nonsea-salt ions 40% of the organic carbon was water soluble and the amount of highly refractory carbon was low. Humic-like substances were not detected but instead low molecular weight carboxylic acids were responsible for about one-fifth of the water-soluble organic mass. These results imply that the influence of carbonaceous compounds on aerosol properties (e.g. hygroscopic, optical) might be significant.

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

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

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


Abstract

 

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

 

On the ability of pseudo-operational ground-based Light Detection And Ranging (LIDAR) sensors to det On the ability of pseudo-operational ground-based Light Detection And Ranging (LIDAR) sensors to det

Date added: 08/05/2011
Date modified: 08/05/2011
Filesize: 3.35 MB

Milroy, C., Martucci, S. Lolli,  S. Loaec, L. S. I. Xueref-Remy, J. V. Lavrič, C.D. O’Dowd,  On the ability of pseudo-operational ground-based Light Detection And Ranging (LIDAR) sensors to determine boundary-layer structure: intercomparison and comparison with in-situ radiosounding, Atmos. Meas. Tech. Diss.. 1–35, 2011 www.atmos-meas-tech discuss.net/4/1/2011/doi:10.5194/amtd-4-1-2011, 2011

 


 

Twenty-one cases of boundary-layer (BL) structure were retrieved by three co-located remote sensors, one lidar (Leosphere ALS300) and two ceilometers (Vaisala CL31, Jenoptik CHM15K). Data were collected during the ICOS field campaign held at the

GAW Atmospheric Station of Mace Head, Ireland, from 8 to 28 June 2009. The study is a two-step investigation of the BL structure based (i) on the intercomparison of backscatter pofiles from the three laser sensors and (ii) on the comparison of the backscatter profiles with twenty-three radiosoundings performed during the period of 8 to 15 June 2009. The Temporal Height-Tracking (THT) algorithm was applied to the three sensors’ backscatter profiles to retrieve the decoupled structure of the BL over Mace Head. The results of the intercomparisons are expressed in terms of the mean correlation coefficients, mean bias (difference between two sensors’ detections), mean sigma (the standard deviation of the bias) and the consistency, i.e. the percentage of cases where the detections of the intercompared sensors were closer than 200 m.  The ALS300-CHM15K comparison provided the most consistent retrievals amongst the three comparisons with, respectively, the 86.5% and 77.2% of the lower and upper layer detections closer than 200m and with correlation coefficients equal to 0.88 and 0.83 at the lower and upper layer, respectively. The lidar and ceilometers-detected BL heights were then compared to the temperature profiles retrieved by radiosoundings. The most consistent retrievals at the lower layer are from the ALS300 with the 75% of  detections closer than 200m to the radiosoundings’ first temperature inversion. Despite the lower signal-to-noise ratio and R-value compared to the ASL300 and CHM15K, the CL31 is more consistent with  the soundings retrievals at the upper layer with 62.5% of detections closer than 200m to the radiosoundings’ econd temperature inversion. The ALS300 has larger pulse-averaged power compared to the two ceilometers and better ability in detecting fine aerosol layers within the BL. The comparison of remote and in-situ data proved both the veracity of the inherent link between temperature and aerosol backscatter profiles, and the existence of possible limitations in using aerosols as a tracer to detect the BL structure. 

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

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

Abstract


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

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

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

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


Abstract


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

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

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

 

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

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

Relationships between condensation nuclei number concentration, tides, and standard meteorological variables at Mace Head, Ireland Relationships between condensation nuclei number concentration, tides, and standard meteorological variables at Mace Head, Ireland

Date added: 07/31/2000
Date modified: 07/23/2009
Filesize: 1.21 MB

O'Brien, E. W., Jennings, S.G., Geever, M., and Kleefeld, C. (2000). Relationships between condensation nuclei number concentration, tides, and standard meteorological variables at Mace Head, Ireland. J. Geophys. Res., 105, 1973-1986.


Abstract


The set of hourly averaged condensation nuclei (CN) data collected at Mace Head during 1991-1994 was examined for relationships that might exist between CN number concentrations and the more commonly measured meteorological variables, including tides. CN number concentrations at Mace Head can be characterized by typically low background levels (less than about 700 particles cm-3) when the wind is from the west, somewhat higher background levels (1000-4000 particles cm-3) when the wind is from the east, with sporadic bursts of short-lived discrete events of more than 10,000 cm-3 for several hours. These events occur typically during early afternoon and are normally associated with slack winds and anomalously warm, dry air. They appear to be independent of pressure, wind direction and precipitation. They can occur any time during the year, although the strongest events tend to occur during spring and autumn. Large-amplitude low tides also occur predominantly in the early afternoon during this observing period. We present evidence that large CN concentration events occur preferentially after exceptionally low tides during daylight. A neural network was employed to train the standard meteorological variables to predict CN concentrations. Baseline forecasts of CN counts for the final 180 days of the observing period were made using lagged values of all other variables. Further forecasts were made with some variables removed from the predictor set. The best correlation between the predicted values and the verifying data over the 180 days was 0.67, which was obtained from a 1-hour forecast using knowledge of all variables except temperature. Other variables whose removal improved the forecast (or whose presence degraded it) were pressure and wind speed. The best predictors of CN values were wind direction, relative humidity, and time of day. An elementary nearest neighbor, or historical analogue approach to predicting the same set of CN values generated lower correlations with the verifying data but generated a much more accurate probability distribution function.

Continuous observations of carbon dioxide at Mace Head, Ireland from 1995 to 1999 and its net European ecosystem exchange Continuous observations of carbon dioxide at Mace Head, Ireland from 1995 to 1999 and its net European ecosystem exchange

Date added: 07/31/2002
Date modified: 07/27/2009
Filesize: 376.57 kB
Derwent, R.G., Ryall, D.B., Manning, A.J., Simmonds, P.G., O’Doherty, S., Biraud, s., Ciais, P., Ramonet, M., and Jennings, S.G., 2002. Continuous observations of carbon dioxide at Mace Head, Ireland from 1995 to 1999 and its net European ecosystem exchange, Atmos. Environ., 36, pp. 2799 – 2807.

Abstract


A 5-yr record of continuous high-frequency carbon dioxide CO2 observations over the 1995-1999 period for the Mace Head Atmospheric Research Station has been examined to reveal a complex interplay between local- and regional-scale sources and sinks. During the winter months, an additional CO2 source, over and above fossil fuel combustion, is required to support the observed concentrations of CO2 in European regionally polluted air masses. During the summer months, an additional CO2 sink is required. Over the entire study period, the additional net European ecosystem exchange source-sink required is -0.36+/-0.4Gtonne Cyr-1.

Production Flux of Sea-Spray Aerosol. Rev. of Geophys., Production Flux of Sea-Spray Aerosol. Rev. of Geophys.,

Date added: 05/12/2011
Date modified: 05/12/2011
Filesize: 2.68 MB

de Leeuw, G., E. Andreas, M. Anguelova , C. Fairall , E. Lewis , C. O'Dowd , M. Schulz , S. Schwartz , Production Flux of Sea-Spray Aerosol. Rev. of Geophys., doi:10.1029/2010RG000349, 2011


 

Knowledge of the sizeand compositiondependent production flux of primary sea spray aerosol (SSA) particles and its dependence on environmental variables is required for modeling cloud microphysical properties and aerosol radiative influences, interpreting measurements of particulate matter in coastal areas and its relation to air quality, and evaluating rates of uptake and reactions of gases in sea spray drops. This review examines recent research pertinent to SSA production flux, which deals mainly with production of particles with r80 (equilibrium radius at 80% relative humidity) less than 1 mm and as small as 0.01 mm. Production of sea spray particles and its dependence on controlling factors has been investigated in aboratory studies that have examined the dependences on water temperature, salinity, and the presence of organics and in field measurements with micrometeorological techniques that use newly developed fast optical particle sizers. Extensive measurements show that waterinsoluble organic matter contributes substantially to the omposition of SSA particles with r80 < 0.25 mm and, in locations with high biological activity, can be the ominant constituent. Orderofmagnitude variation  remains in estimates of the sizedependent production flux per white area, the quantity central to formulations of the production flux based on the whitecap method. This variation indicates that the production flux may depend on quantities such as the volume flux of air bubbles to the surfacet hat are not accounted for in current models. Variation in estimates of the whitecap fraction as a function of wind speed contributes additional, comparable uncertainty to production flux estimates.  

Cloud condensation nuclei measurements at Mace Head, Ireland, over the period 1994-2002 Cloud condensation nuclei measurements at Mace Head, Ireland, over the period 1994-2002

Date added: 08/01/2006
Date modified: 07/27/2009
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Reade, K., S.G. Jennings, and G. McSweeney, Cloud condensation nuclei measurements at Mace Head, Ireland, over the period 1994-2002, Atmos. Res., 82, 610-621, 2006.


Abstract


Analyses of cloud condensation -nuclei (CCN) number concentrations (cm-3) measured at the Mace Head Atmospheric Research Station, near Carna, County Galway, Ireland, using a DH Associates Model M1 static thermal diffusion cloud chamber over the period from March 1994 to September 2002 are presented in this work. Air masses are defined as being 'marine' if they originate from a wind direction of 180-300° and 'continental' air masses are defined as originating from a wind direction of 45-135°. Air masses without such filtering were classified as 'undefined' air masses. Air masses were found to be dominated by marine sector air, re-affirming Mace Head as a baseline atmospheric research station. CCN levels for specific air masses at Mace Head were found to be comparable with earlier studies both at Mace Head and elsewhere. Monthly averaged clean marine (wind direction of 180-300° and black carbon absorption coefficient <1.425 Mm-1) CCN and marine CCN varied between 15-247 cm-3 and 54-670 cm-3, respectively. As expected, significant increases in number concentration were found in continentally sourced CCN over that of marine CCN and were found to follow a log-normal distribution significantly tighter than that of clean marine air masses. No significant trend was found for CCN over the 9-year period. While polluted continental air masses showed a slight increase in CCN concentrations over the winter months, most likely due to increased fuel usage and a lower mixed boundary layer, the dominance of marine sector air arriving at Mace Head, which generally consists of background CCN concentrations, reduced seasonal differences for polluted air. Marine air showed a distinct seasonal pattern, with elevated values occurring over the spring and summer seasons. This is thought to be due to enhanced biogenic aerosol production as a result of phytoplankton bloom activity in the North Atlantic.

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

Date added: 09/22/2003
Date modified: 07/23/2009
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Price, M., Dowd, C., & Dixon, M. (2003). Interpretation of roadside PM10 monitoring data from Sunderland, United Kingdom. Environmental Monitoring and Assessment, 82, 225-241


Abstract


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

Condensation Nuclei as indicators of air pollution Condensation Nuclei as indicators of air pollution

Date added: 07/31/1984
Date modified: 07/27/2009
Filesize: 2.52 MB

O'Connor, T.C. & O'Dea, J.J.(RTC Sligo) (1984)- Indicators of Air Pollution, Irish Journal of Environmental Science, III, pp. 32-39


Abstract


Condensation Nuclei (CN) are Submicron sized particles found in the atmosphere at concentrations of 10^2 to 10^6 particles per cm^3. They arise from a variety of sources but are mainly produced by combustion processes. Sensitive and reliable CN counters have been developed in Ireland to determine their concentration and size. Results from a variety of locations are presented to illustratetheir use as a general indicator of air pollution levels. The Use of CN measurement as a tool for air quality management is discussed.

A Combined Organic-Inorganic sea-spray Source Function A Combined Organic-Inorganic sea-spray Source Function

Date added: 08/06/2007
Date modified: 07/27/2009
Filesize: 317.72 kB

O'Dowd, C. D., B. Langmann, S. Varghese, C. Scannell, D. Ceburnis, and M. C. Facchini (2008), A combined organic-inorganic sea-spray source function, Geophys. Res. Lett., 35, L01801, doi:10.1029/2007GL030331.


Abstract


This study presents a novel approach to develop a combined organic-inorganic sub-micron sea-spray source function for inclusion in large-scale models. It requires wind speed and surface ocean chlorophyll-a concentration as input parameters. The combined organic-inorganic source function is implemented in the REMOTE regional climate model and sea-spray fields are predicted with particular focus on the North East Atlantic. The model predictions using the new source functions compare well with observations of total sea-spray mass and organic carbon fraction in sea-spray aerosol. During winter (periods of low oceanic biological activity), sea-salt dominates the sea-spray mass while in summer (when biological activity is high), water soluble organic carbon contributes between 60–90% of the submicron sea-spray mass.

 

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

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

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


Abstract

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

 

A comparison of PM10 levels at mace head and at Trinity College Dublin A comparison of PM10 levels at mace head and at Trinity College Dublin

Date added: 08/07/2000
Date modified: 07/27/2009
Filesize: 102.39 kB

Finnan J.; McGovern F.M.; O'Leary B.; O'Donnell C.,A comparison of PM10 levels at mace head and at Trinity College Dublin,Journal of Aerosol Science, Volume 31, Supplement 1, September 2000 , pp. 887-888(2)


Abstract


In recent years the role of particulate matter in environmental and health areas has come under increased attention from regulatory and monitoring agencies. This has lead to the introduction of an EC directive on monitoring of PM10 (particulate matter size less than 10 p,m) levels for EU countries. However, the use of PM 10 as a measurement standard has been the subject of considerable debate with lower cut off points, e.g. 2.5 p,m (PM2.5) being considered by many to be of more directly relevant to health issues. Here we present an analysis of PM 10 measurements carried out at two very different sites, i.e. the background site at Mace Head and the central Dublin site of Trinity College Dublin (TCD). Concurrent size distribution data are used to examine the results.

Chemical and physical characteristics of aerosol particles at a remote coastal location, Mace Head, Ireland, during NAMBLEX Chemical and physical characteristics of aerosol particles at a remote coastal location, Mace Head, Ireland, during NAMBLEX

Date added: 08/01/2005
Date modified: 07/01/2009
Filesize: 435.58 kB

Coe, H., J. D. Allan, R. M. Alfarra, K. N. Bower, M. J. Flynn, G. B. McFiggans, D. O. Topping, P. I. Williams, C. D. O'Dowd, M. Dall'Osto, D. C. S. Beddows and R. M. Harrison, Chemical and physical characteristics of aerosol particles at a remote coastal location, Mace Head, Ireland, during NAMBLEX, Atmospheric Chemistry and Physics Discussions, Vol. 5, pp 11643-11678, 2005.


Abstract


Aerosol number concentrations and size distributions from 3 nm to 20 µm diameter were measured at the Mace Head Atmospheric Research Station, Co. Galway, Ireland, a coastal site on the eastern seaboard of the north Atlantic Ocean. Both on and offline size resolved aerosol composition measurements were also made using an Aerodyne Aerosol Mass Spectrometer (AMS) and ion chromatographic analysis of daily samples collected using a Micro-Orifice Uniform Deposit Impactor (MOUDI). Particle number concentrations, size distributions and AMS measurements were determined at 7 and 22 m above ground level to investigate local effects on the aerosol size distribution induced by the tidal zone. During periods of new particle formation ultrafine particle number concentrations are large and variable, however, outside these periods no variability in particle number was observed at any size, nor was the particle composition variable. Analysis of particle size distributions show that within each air mass observed particle number concentrations were very consistent. During anticyclonic periods and conditions of continental outflow Aitken and accumulation mode were enhanced by a factor of 5 compared to the marine sector, whilst coarse mode particles were enhanced during westerly conditions. Baseline marine conditions were rarely met at Mace Head during NAMBLEX and high wind speeds were observed for brief periods only.

Loss rates of gaseous species to aerosol surfaces were calculated for a range of uptake coefficients. Even when the accommodation coefficient is unity, lifetimes of less than 100 s were never observed and rarely were lifetimes less than 500 s. Diffusional limitation to mass transfer is important in most conditions as the coarse mode is always significant, we calculate a minimum overestimate of 50% in the loss rate if this is neglected and so it should always be considered when calculating loss rates of gaseous species to particle surfaces. HO2 and HOI have accommodation coefficients of around 0.03 and hence we calculate lifetimes due to loss to particle surfaces of 2000 s or greater. Aerosol composition measurements using the AMS show accumulation mass modes of acidified sulphate and organic material, both of which have the same shape and are centred at around 350 nm vacuum aerodynamic diameter, implying an internal mixture. The organic and sulphate are approximately equally important, though the mass ratio varies considerably between air masses. Mass spectral fingerprints of the organic fraction in polluted conditions are similar to those observed at other locations that are characterised by aged continental aerosol. Even in marine conditions a background concentration of between 0.5 and 1 µg m−3 of both organic and sulphate was observed. Key differences in the mass spectra were observed during the few clean periods but were insufficient to ascertain whether these changes reflect differences in the source fingerprint of the organic aerosol. However, in an accompanying paper (Dall'Osto et al., 2005) periods of organic dominated aerosol particles were also observed and could be separated from the aged continental aerosol. The coarse mode was composed of sea salt and showed significant displacement of chloride by nitrate and to a lesser extent sulphate in polluted conditions.

The concurrent observation of methyl iodide and dimethyl sulphide in marine air; implications f The concurrent observation of methyl iodide and dimethyl sulphide in marine air; implications f

Date added: 08/07/1998
Date modified: 07/23/2009
Filesize: 560.08 kB

Bassford, M.R., G. Nickless, P.G. Simmonds, A.C. Lewis, M.J. Pilling, and M.J. Evans, The concurrent observation of methyl iodide and dimethyl sulphide in marine air; implications for sources of atmospheric methyl iodide, Atmospheric Environment, 33 (15), 2373-2383, 1999.


Abstract


Continuous atmospheric measurements of methyl iodide and dimethyl sulphide were carried out at Mace Head, western Ireland, over a 4-week period in July 1996. The concurrent observations of methyl iodide and dimethyl sulphide reported here display a clear association, indeed statistical analysis indicated a very significant degree of covariance. A simple yet informative use of modelled 5-day back trajectories was employed in tandem with examination of local meteorology to illuminate the geographical source regions of methyl iodide and dimethyl sulphide. The interpretation of the atmospheric observations in terms of air-mass flow has elucidated part of the global methyl iodide cycle and provides evidence for two distinct source regions of methyl iodide: I. Under certain synoptic meteorological conditions, long-range transport of methyl iodide and dimethyl sulphide was observed from discrete areas of the sub-tropical Atlantic Ocean located in a region between 30-50°N and 20-50°W. 2. Measurements taken under different conditions led us to believe that there was an additional source of methyl iodide that influenced the Mace Head atmosphere, most likely produced by coastal macroalgae which inhabit waters off the western coast of Ireland.

 

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.

 

(NAMBLEX). Overview of the campaign held at Mace Head,  Ireland, in summer 2002 (NAMBLEX). Overview of the campaign held at Mace Head, Ireland, in summer 2002

Date added: 08/06/2006
Date modified: 07/27/2009
Filesize: 9.65 MB

Heard, D. E., Read, K. A., Methven, J., Al-Haider, S., Bloss, W. J., Johnson, G. P., Pilling, M. J., Seakins, P. W., Smith, S. C., Sommariva, R., Stanton, J. C., Still, T. J., Ingham, T., Brooks, B., De Leeuw, G., Jackson, A. V., McQuaid, J. B., Morgan, R., Smith, M. H., Carpenter, L. J., Carslaw, N., Hamilton, J., Hopkins, J. R., Lee, J. D., Lewis, A. C., Purvis, R. M., Wevill, D. J., Brough, N., Green, T., Mills, G., Penkett, S. A., Plane, J. M. C., Saiz-Lopez, A., Worton, D., Monks, P. S., Fleming, Z., Rickard, A. R., Alfarra, M. R., Allan, J. D., Bower, K., Coe, H., Cubison, M., Flynn, M., McFiggans, G., Gallagher, M., Norton, E. G., O'Dowd, C. D., Shillito, J., Topping, D., Vaughan, G., Williams, P., Bitter, M., Ball, S. M., Jones, R. L., Povey, I. M., O'Doherty, S., Simmonds, P. G., Allen, A., Kinnersley, R. P., Beddows, D. C. S., Dall'Osto, M., Harrison, R. M., Donovan, R. J., Heal, M. R., Jennings, S. G., Noone, C., and Spain, G.: The North Atlantic Marine Boundary Layer Experiment(NAMBLEX). Overview of the campaign held at Mace Head, Ireland, in summer 2002, Atmos. Chem. Phys., 6, 2241-2272, 2006.


Abstract


The North Atlantic Marine Boundary Layer Experiment (NAMBLEX), involving over 50 scientists from 12 institutions, took place at Mace Head, Ireland (53.32° N, 9.90° W), between 23 July and 4 September 2002. A wide range of state-of-the-art instrumentation enabled detailed measurements of the boundary layer structure and atmospheric composition in the gas and aerosol phase to be made, providing one of the most comprehensive in situ studies of the marine boundary layer to date. This overview paper describes the aims of the NAMBLEX project in the context of previous field campaigns in the Marine Boundary Layer (MBL), the overall layout of the site, a summary of the instrumentation deployed, the temporal coverage of the measurement data, and the numerical models used to interpret the field data. Measurements of some trace species were made for the first time during the campaign, which was characterised by predominantly clean air of marine origin, but more polluted air with higher levels of NOx originating from continental regions was also experienced. This paper provides a summary of the meteorological measurements and Planetary Boundary Layer (PBL) structure measurements, presents time series of some of the longer-lived trace species (O3, CO, H2, DMS, CH4, NMHC, NOx, NOy, PAN) and summarises measurements of other species that are described in more detail in other papers within this special issue, namely oxygenated VOCs, HCHO, peroxides, organo-halogenated species, a range of shorter lived halogen species (I2, OIO, IO, BrO), NO3 radicals, photolysis frequencies, the free radicals OH, HO2 and (HO2+Σ RO2), as well as a summary of the aerosol measurements. NAMBLEX was supported by measurements made in the vicinity of Mace Head using the NERC Dornier-228 aircraft. Using ECMWF wind-fields, calculations were made of the air-mass trajectories arriving at Mace Head during NAMBLEX, and were analysed together with both meteorological and trace-gas measurements. In this paper a chemical climatology for the duration of the campaign is presented to interpret the distribution of air-mass origins and emission sources, and to provide a convenient framework of air-mass classification that is used by other papers in this issue for the interpretation of observed variability in levels of trace gases and aerosols.

A graphical method for determining the dry-depositional component of aerosol samples and their A graphical method for determining the dry-depositional component of aerosol samples and their

Date added: 08/07/1997
Date modified: 07/27/2009
Filesize: 907.95 kB

Huang, S., K. Rahn, and R. Arimoto. 1997. A graphical method for determining the dry-depositional component of aerosol samples and their field blanks. Atmospheric Environment 31:3383-3394.


Abstract


During the Atmosphere/Ocean Chemistry Experiment (AEROCE), field blanks of certain elements in aerosol samples occasionally increased abruptly, always during periods of unusually high atmospheric concentrations. We hypothesized that the anomalous blanks were created by coarse aerosol entering the sampling shelters and depositing onto the blank filters. If so, samples taken nearby should have been similarly affected. To test this hypothesis, we developed a simple graphical method in which elemental masses in field blanks are plotted against elemental masses in pumped samples, and zones of proportionality between the two are sought. Data from Bermuda and Mace Head (coastal western Ireland) confirmed that depositional zones did indeed appear, but only for coarse-particle elements and only under certain conditions. Actual increases of crustal and pollution-derived elements agreed well with values predicted from settling velocities and sampling rates: blanks increased up to an order of magnitude or more but samples by less than 1%. Marine elements behaved like crustal elements in most samples but occasionally were much more enriched: blanks increased up to 30-fold and samples up to about 3%. It thus appears that when coarse-particle elements are present in high concentrations, their field blanks and samples may be measurably affected by dry deposition. Depending on the elements of interest, this dry deposition may have to be measured and the concentrations corrected.

 

Modelling OH, HO2, and RO2 radicals in the marine boundary layer 2. Mechanism reduction and unce Modelling OH, HO2, and RO2 radicals in the marine boundary layer 2. Mechanism reduction and unce

Date added: 08/06/1999
Date modified: 07/23/2009
Filesize: 1.21 MB

Carslaw N., P.J. Jacobs, and M.J. Pilling (1999), Modelling OH, HO2 and RO2 radicals in the marine boundary layer: 2. Mechanism reduction and uncertainty analysis, J. Geophys. Res., 104, 30257-30273.


Abstract


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

 

Proceedings of the Royal Irish Academy The Calibration of a photo-electric nucleus counter. Proceedings of the Royal Irish Academy The Calibration of a photo-electric nucleus counter.

Date added: 08/31/1946
Date modified: 07/22/2009
Filesize: 4.32 MB
P.J Nolan, L.W. Pollack, Proceedings of the Royal Irish Academy The Calibration of a photo-electric nucleus counter., Volume L1, Section A, No. 2, 1946

Abstract

 

Models of nucleus counterm designed to measure photo-electrically the decrease in intensity of a beam of light which has passed one or more times through an artificially produced fog, are described by L.W. Pollak and W.A. Morgan in a paper.

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.

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

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

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


Abstract


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

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

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

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


Abstract


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

Condensation and coagulation sinks and formation of NMP in coastal and boreal forest BL Condensation and coagulation sinks and formation of NMP in coastal and boreal forest BL

Date added: 08/06/2002
Date modified: 07/21/2009
Filesize: 360.63 kB

Dal Maso, M., M. Kulmala, K. E. J. Lehtinen, J. M. Mäkelä, P. Aalto, and C. D. O'Dowd (2002), Condensation and coagulation sinks and formation of nucleation mode particles in coastal and boreal forest boundary layers, J. Geophys. Res., 107(D19), 8097, doi:10.1029/2001JD001053.


Abstract


The formation and growth of new particles has been evaluated using a revised version of a simple, but novel, theoretical tool. The concentration of condensable vapors and their source rates has been estimated using the aerosol condensation sink together with the measured particle growth rate. Also, by adding the coagulation sink and the measured formation rate of 3 nm particles, the formation rate of 1 nm particles and their concentration can be estimated. Condensation and coagulation sinks can be obtained from ambient aerosol size distribution data. The method has been applied to analyze the particle formation and growth rates observed during coastal and boreal forest nucleation events. The condensation sinks are typically 4-7 x 10-3 s-1 in the forest and 2 x 10-3 s-1 under coastal conditions, while the coagulation sinks for 1, 2, and 3 nm particles are typically smaller by factors 1.5-2, 5-7, and 11-15, respectively. The measured growth rates are 2-10 nm/h for the boreal forest and range from 15 to 180 nm/h at the coast, corresponding to a vapor concentration of 2-13 x 10 cm-3 and 108 cm-3 to 109 cm-3, respectively. The vapor source rate was 1-2 x 105 cm-3 s-1 in the boreal forest and 2-5 x 106 cm-3s-1 in the coastal environment. The estimated formation rate of 1 nm particles in the forest environment was 8-20 cm-3s-1 and 300-10,000 cm-3 s-1 at the coast. The concentration of 1 nm particles was estimated to be 2000-5000 and 4 × 104-7 × 106 particles cm-3 in forest and at coast, respectively.

 

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

Coastal New Particle Formation: A Review of the Current State-Of-The-Art Coastal New Particle Formation: A Review of the Current State-Of-The-Art

Date added: 08/01/2005
Date modified: 07/27/2009
Filesize: 773.65 kB

O’Dowd, C. D., T. Hoffmann, Coastal New Particle Formation: A Review of the Current State-Of-The-Art. Environ. Chem. 2, 245. doi:10.1071/EN05077, 2005.


Abstract


New particle formation via secondary gas-to-particle conversion processes over the oceans is one of the main mechanisms controlling the marine aerosol number population; however, despite extensive effort over the years, this phenomenon is still not well quantified. Coastal new particle formation events are more frequent than open ocean events and consequently have been studied in greater detail. This review article summarizes the recent studies into coastal new particle formation events and summarizes the linkage of these events to iodine emissions and ultimate particle formation via iodine oxide nucleation processes. The current state of knowledge may be summarized by concluding that, in general, coastal nucleation events are driven by biogenic emissions of iodine vapours that undergo rapid chemical reactions to produce condensable iodine oxides leading to nucleation and growth of new particles. The primary source of the condensable iodine vapours is thought to be molecular iodine (I2). The role of iodine oxides in open-ocean new particle production still remains an open question and is the most pressing next step to undertake.

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.


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

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

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


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

Simulating ultrafine particle formation in Europe using a regional CTM: contribution of primary emissions versus secondary formation to aerosol number concentrations Simulating ultrafine particle formation in Europe using a regional CTM: contribution of primary emissions versus secondary formation to aerosol number concentrations

Date added: 03/21/2013
Date modified: 03/21/2013
Filesize: 2.01 MB

Fountoukis, C., I. Riipinen, H. A. C. Denier van der Gon, P. E. Charalampidis, C. Pilinis, A. Wiedensohler, C. O'Dowd, J. P. Putaud, M. Moerman, and S. N. Pandis, Simulating ultrafine particle formation in Europe using a regional CTM: contribution of primary emissions versus secondary formation to aerosol number concentrations, Atmos. Chem. Phys., 12, 8663–8677, 2012 www.atmos-chem-phys.net/12/8663/2012/ doi:10.5194/acp-12-8663-2012.


Abstract. A three-dimensional regional chemical transport model (CTM) with detailed aerosol microphysics, PMCAMx-UF, was applied to the European domain to simulate the contribution of direct emissions and secondary formation to total particle number concentrations during May 2008. PMCAMx-UF uses the Dynamic Model for Aerosol Nucleation and the Two-Moment Aerosol Sectional (TOMAS) algorithm to track both aerosol number and mass concentration using a sectional approach. The model predicts nucleation events that occur over scales of hundreds up to thousands of kilometers especially over the Balkans and Southeast Europe. The model predictions were compared against measurements from 7 sites across Europe. The model reproduces more than 70% of the hourly concentrations of particles larger than 10 nm (N10) within a factor of 2. About half of these particles are predicted to originate from nucleation in the lower troposphere. Regional nucleation is predicted to increase the total particle number concentration by approximately a factor of 3. For particles larger than 100 nm the effect varies from an increase of 20% in the eastern Mediterranean to a decrease of 20% in southern Spain and Portugal resulting in a small average increase of around 1% over the whole domain. Nucleation has a significant effect in the predicted N50 levels (up to a factor of 2 increase) mainly in areas where there are condensable vapors to grow the particles to larger sizes. A semi-empirical ternary sulfuric acid-ammonia-water parameterization performs better than the activation or the kinetic parameterizations in reproducing the observations. Reducing emissions of ammonia and sulfur dioxide affects certain parts of the number size distribution.

 

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

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

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


Abstract


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

 

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

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

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


Abstract


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

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

Source apportionment of individual aerosol particles by using time-of-flight mass spectrometry Source apportionment of individual aerosol particles by using time-of-flight mass spectrometry

Date added: 08/06/2003
Date modified: 08/18/2008
Filesize: 7.67 kB

M. Dall Osto , R. M. Harrison , D. Beddows , R. P. Kinnesley , R. J. Donovan  and M. R. Heal, Source apportionment of individual aerosol particles by using time-of-flight mass spectrometry, 2003


Aerosol dynamics in ship tracks Aerosol dynamics in ship tracks

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

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


Abstract

 

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

Organic matter contribution to marine aerosols and cloud condensation nuclei Organic matter contribution to marine aerosols and cloud condensation nuclei

Date added: 09/23/2008
Date modified: 07/23/2009
Filesize: 158.68 kB

Baerbel Langmann, Claire Scannell, Colin O'Dowd, New Directions: Organic matter contribution to marine aerosols and cloud condensation nuclei, Atmospheric Environment, Volume 42, Issue 33, October 2008, Pages 7821-7822, ISSN 1352-2310, DOI: 10.1016/j.atmosenv.2008.09.002.


Abstract

 

Aerosols in the marine atmosphere influence solar irradiation over the world's ocean directly by backscattering incoming solar radiation and indirectly, by forming cloud condensation nuclei (CCN) thereby affecting the cloud albedo. Charlson et al. (1987) suggested the existence of a feedback mechanism between climate change and the flux of oceanic dimethyl sulfide (DMS), commonly known as the CLAW hypothesis after the four founding authors. According to this hypothesis, DMS produced by marine phytoplankton is ventilated into the marine boundary layer (MBL) and ultimately oxidised to sulfate aerosol which form CCNs.

The change in cloud albedo results in a global temperature perturbation affecting the productivity of the marine biosphere and hence the concentration of oceanic DMS. The authors assumed that non-sea salt (nss) sulfate aerosol as oxidation product of DMS is the major source of CCN over the oceans thereby disregarding the potential of other chemical components of the submicron marine aerosol like sea salt and water soluble and water insoluble organic carbon (OC) to form CCNs. Since the publication of the CLAW hypothesis it has been difficult to prove or disprove the idea, however several studies (e.g. Woodhouse et al., 2008) have elucidated that DMS flux in the MBL alone cannot explain new particle and CCN formation.

In recent years, the role of natural organic aerosol in the marine environment has received increasing attention. Measurements indicate that the increase of the marine biological activity is accompanied by a considerable increase of the contribution of OC to the submicron marine aerosol (e.g. O'Dowd et al., 2004) exceeding the mass fraction of nss sulfate by a factor of more than two. OC aerosols are partly primary aerosols (POC) which are directly released from the ocean and partly secondary aerosols (SOC) which form in the atmosphere through chemical reactions of reactive gases released at the ocean surface. CCNs formed from POC and reactive gases like isoprene should be available much closer to areas with increased marine biological activity than CCNs formed from nss sulfate. Meskhidze and Nenes (2006) argued that SOC aerosols can act as efficient CCNs in the Southern Ocean, even though the authors had to revise their estimates of oceanic isoprene fluxes. Roelofs (2008) showed in a global model study that OC aerosols significantly contribute to marine cloud optical properties and seasonality by estimating a global annual flux of marine organic matter of about 75 Tg C yr−1 (corresponding to 90–135 Tg OC yr−1 depending on the applied conversion factor) whereas Spracklen et al. (2008) provide a global annual oceanic OC emission estimate of around 8 Tg OC yr−1. The very different approaches used by the authors lead to a one order of magnitude difference in the marine OC emissions estimates. As measurements are generally limited spatially and temporally and are only available for selected gases or aerosols, globally, the role of the ocean as a source of photochemical active gases and aerosols remains unclear.

We would like to contribute to an improved understanding of marine OC emissions by presenting a global annual marine OC flux estimate based on a different approach. A combined organic–inorganic submicron sea–spray source function (O'Dowd et al., 2008) is applied globally, where we make use of chlorophyll-a concentration obtained from MODIS Aqua and Terra satellite and wind speed obtained from SeaWinds on QuikSCAT as monthly average input information. The only difference to O'Dowd et al. (2008) is the use of a revised relationship between organic mass and chlorophyll concentration in the current estimate (organic mass [%] = 49.129 × chlorophyll [mg m−3]) because of recent corrections of the chemical analysis. The resulting marine flux of submicron OC aerosols is 2.3 Tg OC yr−1 for 2003 and 2.8 Tg C yr−1 for 2006, with a spatial distribution as shown in Fig. 1. As the submicron OC aerosols are likely internally mixed with sea-salt and therefore are already hygroscopic, they can act as sites for biogenic SOC condensation making them more active as CCN. Estimates for the very high latitudes should be regarded with caution because the satellite sensors have a large margin of errors in these regions. Our estimate of the global annual marine OC flux is in the range of that published by Spracklen et al. (2008), but approximately a factor of 3 lower as only submicron particles are considered here. The global distribution of the marine OC flux by Spracklen et al. (2008) follows the global distribution of chlorophyll-a, whereas high wind speed in the approach presented here leads to increased marine OC emissions in particular in the region of the Antarctic circumpolar current, the North Atlantic and the North Pacific Ocean and considerably lower emissions in the tropics and subtropics where wind speed is generally lower. Further measurements preferably in remote oceanic regions, and measurements and modelling studies on the mechanisms of marine OC production are needed to illuminate the nature and role of marine OC aerosols and their potential to act as CCNs.

Effects of source temporal resolution on transport simulations of boreal fire emissions Effects of source temporal resolution on transport simulations of boreal fire emissions

Date added: 08/06/2006
Date modified: 07/27/2009
Filesize: 427.81 kB

Hyer, E. J., E. S. Kasischke, and D. J. Allen (2007), Effects of source temporal resolution on transport simulations of boreal fire emissions, J. Geophys. Res., 112, D01302, doi:10.1029/2006JD007234.


Abstract


The quality of temporal information from daily burned area inputs was evaluated using a transport and chemistry experiment. Carbon monoxide emissions from boreal forest fires were estimated using burned area inputs with daily resolution. Averaging of emissions data to create 30-day aggregate data reduced the variance by 80%, indicating a substantial loss of information. Data from Russia, Canada, and Alaska were tested for periodicity to uncover systematic gaps in daily data. Some evidence of periodicity was found in data from Alaska, where temporal information came from fire mapping by the Alaskan Fire Service. Autocorrelation decayed rapidly and nearly monotonically for Canada and Russia, where temporal information came from Advanced Very High Resolution Radiometer (AVHRR) satellite observations. Daily data as well as 7-day and 30-day aggregates were used as input to the University of Maryland Atmospheric Chemistry and Transport Model, and output was compared with CO observations from the Cooperative Air Sampling Network (CASN); continuous measurements from Mace Head, Ireland; and total column CO retrievals from the Measurement of Pollution in the Troposphere (MOPITT) instrument. CASN flask measurements showed no sensitivity to high-frequency variability in the source, indicating the effectiveness of the filtering protocol at ensuring only well-mixed air masses are sampled in this data set. Differences between daily and 7-day simulations were too small for quantitative comparison in any of the data. For cases where the differences were substantial, simulations using daily and 7-day average sources agreed better with observations than 30-day average sources.

 

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

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

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


Abstract

 

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

A global black carbon aerosol model A global black carbon aerosol model

Date added: 07/31/1996
Date modified: 07/27/2009
Filesize: 1.35 MB
Cooke W.F. and J.J.N. Wilson. (1996)- A global black carbon aerosol model, J. Geophys. Res., 101, 19395-19409.

Abstract


A global inventory has been constructed for emissions of black carbon from fossil fuel combustion and biomass burning. This inventory has been implemented in a three-dimensional global transport model and run for 31 model months. Results for January and July have been compared with measurements taken from the literature. The modeled values of black carbon mass concentration compare within a factor of 2 in continental regions and some remote regions but are higher than measured values in other remote marine regions and in the upper troposphere. The disagreement in remote regions can be explained by the coarse grid scale of the model (10° × 10°), the simplicity of the current deposition scheme, and possibly too much black carbon being available for transport, which would also account for the disagreement in the upper troposphere. The disagreement may also be due to problems associated with the measurement of black carbon. Emissions from this database appear to provide a reasonable estimate of the annual emissions of black carbon to the atmosphere. Biomass burning emissions amount to 5.98 Tg and that from fossil fuel amounts to 7.96 Tg. A local sensitivity analysis has been carried out and shows that black carbon has a lifetime between 6 and 10 days, depending on the transformation rate between hydrophobic and hydrophilic black carbon.

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.

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