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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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General Overview: European Integrated project on Aerosol Cloud Climate and Air Quality interactions General Overview: European Integrated project on Aerosol Cloud Climate and Air Quality interactions

Date added: 08/04/2011
Date modified: 08/04/2011
Filesize: 4.81 MB

M. Kulmala, A. Asmi, H.K. Lappalainen, U. Baltensperger, J.-L. Brenguier, , M. C. Facchini, H.-C. Hansson, Ø. Hov, C. O'Dowd, U. Poeschl, A. Wiedensohler,  R. Boers ,  O. Boucher,  G. De Leeuw, J. Feichter, R. Krejci ,  P. Laj, H. Lihavainen,  U. Lohmann, G. McFiggans, T. Mentel, C. Pilinis ,I.  Riipinen, M. Schultz, A. Stohl, E. Swietlicki, H. Denier Van den Gon , E. Vignati,  M. Amann,  C.Alves,  S. Arabas,  P. Artaxo, D.C.S. Beddows,  P. Beukes, R. Bergström,  M. Bilde, S. Clegg,  H. Coe,  B. d'Anna,  S. Gilardoni, J. Debernard, S.  Decesari,  M. Fischer,  A.M. Fjæraa, C. George, P. Halloran, T. Hamburger, R.M. Harrison, H. Herrman, T. Hoffmann,  C. Hoose, M Hu, U. Hõrrak, Y. Iinuma, T. Iversen,  M. Josipovic,  M. Junying, M. Kanakidou, A.Kiendler-Scharr,  A. Kirkevåg, G. Kiss,  Z. Klimont,    P. Kolmonen,  JE. Kristjansson, L. Laakso, A. Laaksonen, L. Labonnote, K.E.J. Lehtinen, R. Makkonen, G. McMeeking, J. Merikanto, A.Minikin, S.Mirme, W.T. Morgan, D. O’Donnell, TS. Panwar, H. Pawlowska, A Petzold, JJ. Pienaar, C. Pio,  C. Plass-Duelmer, A.S.H. Prévôt, S. Pryor, D. Rosenfeld, J. Schwarz, Ø. Seland, X.J. Shen, B. Sierau, D. Simpson,  J.Y.  Sun, D. Topping, P. Tunved, P. Vaattovaara, V. Vakkari, P. van Zyl, J.P. Veefkind,  B. Wehner, J. Wildt,  G. Visschedijk, S. Woodward, H. Vuollekoski, A. Zardini, K. Zhang, V.-M. Kerminen , K. Carslaw and S. N. Pandis. General Overview: European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) - integrating aerosol research from nano to global scales, Atmos. Chem. & Phys. Disc., 11, 1–176, doi:10.5194/acpd-11-1-2011, 2011.

 


 

Abstract

In this paper we describe and summarize the main achievements of the European  Aerosol Cloud Climate and Air Quality Interactions project (EUCAARI). EUCAARI  started on 1 January 2007 and ended on 31 December 2010 leaving a rich legacy

including: (a) a comprehensive database with a year of observations of the physical, chemical and optical properties of aerosol particles over Europe, (b) the first comprehensive aerosol measurements in four developing countries, (c) a database of airborne measurements of aerosols and clouds over Europe during May 2008, (d) comprehensive modeling tools to study aerosol processes fron nano to global scale and their ef10 fects on climate and air quality. In addition a new Pan-European aerosol emissions inventory was developed and evaluated, a new cluster spectrometer was built and tested in the field and several  new aerosol parameterizations and computations modules for chemical transport and global climate models were  veloped and evaluated. This work enabled EUCAARI to improve our understanding of aerosol radiative forcing  15 and air quality-climate interactions. The EUCAARI results can be utilized in European  and global environmental policy to assess the erosol impacts and the corresponding  abatement strategies.

Whitecap Coverage: Measurements from the North Atlantic Whitecap Coverage: Measurements from the North Atlantic

Date added: 12/10/2008
Date modified: 11/01/2009
Filesize: 198.39 kB
Callaghan, A., G. de Leeuw, L. Cohen, C.D. O’Dowd, Oceanic Whitecap Coverage: Measurements from the North Atlantic, Geophys. Res. Letts., doi:10.1029/2008GL036165, 2008

Abstract

 

Sea surface images obtained during the 2006 Marine Aerosol Production (MAP) campaign in the North East Atlantic were analysed for values of percentage whitecap coverage (W). Values of Ware presented for wind speeds up to circa 23 m s-1. The W data were divided into two overlapping groups and a piecewise,  wind-speed-only parameterization of W is proposed that is valid for wind speeds between 3.70 m s-1 and 23.09 m s-1. Segregation of data points based upon a 2.5 hour wind history acted to decrease data scatter at wind speeds above approximately 9.25 m s-1. At these wind speeds W values were greater for decreasing wind speeds than for increasing wind speeds. No clear wind history effect was observed at wind speeds below 9.25 m s-1

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

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

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


Abstract.

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

 

 

The Mean Free path of Air The Mean Free path of Air

Date added: 07/31/1988
Date modified: 07/08/2009
Filesize: 1.38 MB
Jennings, S.G. (1988). - The mean free path in air. J. Aerosol Sci., 19, 159 - 166.

Abstract


Values for the mean free path l in air are presented for temperatures 15, 20, 23 and 25°C for both dry air and moist air at relative humidities of 50 and 100%, at atmospheric pressure (1.01325 × 105 Pa) and at pressure 1 × 105 Pa. Use is made of an expression which minimizes the dependence on physical ‘constants’ for mean free path: image where μ is the viscosity of air, p is the density of air, P is the pressure and μ is a numerical factor equal to 0.4987445. Differences of up to 1.6% were obtained between the values of mean free path at 23°C from this work and that of other workers. Comparison between the Cunningham slip correction factor from the present work and that from other work shows differences up to 1.8%.

Sub-ppt Atmospheric Measurements Using PTV-GC-FID and realtime Digital Signal Processing Sub-ppt Atmospheric Measurements Using PTV-GC-FID and realtime Digital Signal Processing

Date added: 08/05/1998
Date modified: 07/27/2009
Filesize: 76.15 kB

J.B McQuaid, A.C Lewis and K.D Bartle. , Sub-ppt Atmospheric Measurements Using PTV-GC-FID and Real-Time Digital Signal Processing., Journal of High Resolution Chromatography:


Abstract


Automated on-line trace level measurements in the atmosphere have become possible over the past ten years due to developments in large volume injection technology and the increased availability of  non-cryogenic cooling devices using phenomena such as the Peltier effect. The analysis of hydrocarbon (HC) species in the atmosphere is a particularly challenging area where individual
ambient concentrations as low as 1 ppt may be encountered in clean tropical marine air. From measurements of hydrocarbon species taken in clean air it has been demonstrated that small but significant concentrations of some species remain constantly present. The presence of certain reactive alkene species even at levels below 5 ppt may have a significant impact on the oxidative capacity ofthe clean atmosphere. Whilst halogenated species have been routinely measured on-line at sub-ppt levels for several years, the analysis of HC species has been limited by the flame ionisation detector - the most popular detector for field measurements. The limiting parameter in using FID for trace determination is often the noise generated within the FID amplifier electronics rather than by the absolute detection limit of the FID itself.  The flame ionisation detector amplifier uses a high gain transimpedance stage which has three main sources of noise. The feedback resistor generates both Johnson and Shot noise. This noise passes through the output without amplification as the voltage gain of a transimpedance amplifier is essentially unity over the bandwidth of interest. The third source of noise is due to current noise generated within the amplifier input stages. This noise is subsequently amplified along with the signal. Determinations at very low concentrations using automatic peak height or area integration prove difficult to perform with reliability due to a combination of poor signal to noise and transient detector spikes. By increasing data acquisition sampling rates coupled to the application of a digital signal processing algorithm, the electrometer output can be bandwidth limited to a frequency which allows peak information to be accurately represented whilst substantially reducing noise of higher frequencies. The roll off rate of a digital filter is much greater than can be achieved using an analogue filter. A rejection of greater than 150 dB can be achieved with a pass band to stop band delta of a fraction of 1 Hz. The benefit of this is that chromatographic resolution and efficiency are not affected by the process, i.e. the peaks are not broadened. This communication reports a digital signal processing (DSP) unit tested in parallel to standard data capture system coupled to an automated trace analysis field GC instrument. The basic principle of DSP is to convert a dynamic analogue signal into discrete values by sampling at certain intervals, followed by the application of mathematical filter algorithms to remove any interference or noise that may be obscuring the desired signal. Once processed, the discrete signal may then be converted back to analogue if necessary. Comparison of data from both systems demonstrates a large enhancement in minimum detectable amount and improved integration reliability. Use of a DSP unit has resulted in a lowering of detection limits to allow automated sub-ppt measurements to be performed. Comparison of trace level analysis has shown that raw FID output logged straight to PC leads to a consistent overestimation of peak height of the order of 25% at low signal to noise levels. Post processing of chromatograms using enhancement in digital gain has also been performed. This has demonstrated that a significant amount of noise remaining following on-line processing is induced at the analogue input stage to PC data capture system.

The Eyjafjallajökull Ash Plume – Part II,  Forecasting the plume dispersion., The Eyjafjallajökull Ash Plume – Part II, Forecasting the plume dispersion.,

Date added: 11/17/2011
Date modified: 11/17/2011
Filesize: 2.21 MB

O’Dowd, C., S. Varghese, R. Flanagan, D. Martin, D. Ceburnis, J. Ovadnevaite, G. Martucci, J. Bialek, C. Monahan, H. Berresheim, A. Vaishya, T. Grigas, S. G. Jennings,  P. McVeigh, E. Moran, K. Lambkin, T. Semmler, and R. McGrath, The Eyjafjallajökull Ash Plume – Part II,  Forecasting the plume dispersion., 10.1016/j.atmosenv.2011.10.037, Atmos. Env. 2011.

 


The recent eruption of Iceland’s Eyjafjallajokull volcano caused extensive disruption across Europe. In this paper, we describe the volcanic ash parameterisation incorporated in the regional climate model (REMOTE) for forecasting volcanic ash dispersion. We investigate model sensitivity to emission parameters including eruption column height and vertical release distribution. Model results over a number of key ash incursion events are assessed in terms of agreement with both ground based measurements and retrieved LIDAR data at a number of European sites.

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

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

Abstract


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

The Eyjafjallajökull Ash Plume – Part I:  Physical, Chemical and Optical Characteristics, The Eyjafjallajökull Ash Plume – Part I: Physical, Chemical and Optical Characteristics,

Date added: 11/17/2011
Date modified: 11/17/2011
Filesize: 4.93 MB

O’Dowd, C.D., Darius Ceburnis, J. Ovadnevaite, G. Martucci, J. Bialek, C. Monahan, H. Berresheim, A. Vaishya, T. Grigas, S. G. Jennings,  P. McVeigh, S. Varghese, R. Flanagan, D. Martin, E. Moran, K. Lambkin, T. Semmler, C. Perrino, and R. McGrath, The Eyjafjallajökull Ash Plume – Part I:  Physical, Chemical and Optical Characteristics, Atmos. Environ, doi:10.1016/j.atmosenv.2011.07.004, , 2011.

 

 


Abstract. The Eyjafjallajökull ash plume was detected at the Mace Head Atmospheric Research Station numerous times from April 19th till 18th May, 2010 following subsidence into, and dilution in, the boundary layer.  The three strongest of these events, lasting 12-18 hours, are analysed in detail in terms of physical, chemical and optical properties.  The ash size distribution was bimodal with a supermicron mode of 2.5 mm diameter for the one case where it was measured.  The submicron mode varied from 185 nm during the high-explosive phase to 395 nm during the low-explosive phase.  Non-sea-salt (nss)-sulphate mass was 2.5 times higher during the low-explosive phase. Total particle concentrations ranged from 760 cm-3 to 1247 cm-3 and were typical of clean air in the region.    Between 30% and 39% of submicron chemical mass (i.e. exclusive of water content) was ash primarily composed of silicon dioxide while accounting for the water content, the submicron aerosol was composed of primary ash (15%) , nss-sulphate  (25%) and water (55%).  Hygroscopic growth factors were characteristic of sulphate aerosol but revealed an internally-mixed aerosol pointing to a mix of predominantly primary ash, nss-sulphate and water.  For the majority of the ash plumes, all condensation nuclei (CN, diameter >10 nm) were activated into cloud condensation nuclei (CCN) at a supersaturation of 0.25%.  Aerosol absorption increased by about a factor of two in the plume, compared to background levels, while aerosol scattering coefficients increased by an order of magnitude.

The Interaction of Falling Water drops:Coalescene The Interaction of Falling Water drops:Coalescene

Date added: 07/30/1972
Date modified: 07/08/2009
Filesize: 802.92 kB

Brazier-Smith, P.R., Jennings, S.G., and Latham, J. (1972)- The interaction of falling water drops: coalescence. Proc. Roy. Soc.., A326, 393-408.


Abstract


Experimental studies have been conducted of the interaction of falling water drops of radii R and r (R > r), density p and surface tension or colliding in air with a relative velocity U and a perpendicular distance X between the centre of one drop and the undeflected trajec- tory of the other. R and r were varied from 150 to 750 /m, R/r from 1.0 to 2.5, U from 0.3 to 3.0 m s-1 and X from 0 (head-on collisions) to the maximum value for contact, R+r. Four types of interaction were observed: (1) bouncing; (2) permanent coalescence; (3) coalescence followed by separation; (4) coalescence followed by separation and the formation of satellite drops. The principal effort was devoted to a study of the critical conditions under which drops will separate after coalescence. It was found that there was a critical value of X, denoted by Xc, below which the coalesced drops remained united and above which there was sufficient angular momentum for the drops to separate after coalescence. For a wide range of values of r, R and U the coalescence efficiency e = Xc(R + r)2 was found to lie between 0.1 and 0.4 for drops of identical size and about 0.2 and 0.6 for drops with Rlr = 2.0. A theoretical analysis based on energy concepts predicted that the coalescence efficiency is given by the equation = 2.40(Up f (r) wheref (Rlr) is a function which varies from 1.3 for Rlr = 1 and 3.8 for R/r = 3. The predic- tions of this equation were in excellent agreement with the experimental results over the entire range of conditions studied. Investigations are also described of the critical conditions for the bouncing of colliding drops, the influence of electric charges upon the interactions and the elongation and splitting of a rotating drop.

Wind Speed Influences on Marine Aerosol Optical Depth Wind Speed Influences on Marine Aerosol Optical Depth

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 2.04 MB

O’Dowd, C., C. Scannell, J. Mulcahy & S. G. Jennings,   Wind Speed Influences on Marine Aerosol Optical Depth. Adv. in Meteorol., Article ID 830846,  2010. doi:10.1155/2010/830846, 2010.


TheMulcahy (Mulcahy et al., 2008) power-law parameterization, derived at the coastal Atlantic stationMace Head, between clean marine aerosol optical depth (AOD) and wind speed is compared to open ocean MODIS-derived AOD versus wind speed. The reported AOD versus wind speed (U) was a function of 

U2. The open ocean MODIS-derived AOD at 550nm and 860nm wavelengths, while in good agreement with the general magnitude of the Mulcahy parameterization, follows a power-law with the exponent ranging from 0.72 to 2.47 for a wind speed range of 2–18ms1. For the four cases examined, some MODIS cases underestimated AOD while other cases overestimated AOD relative to the Mulcahy scheme. Overall, the results from MODIS support the general power-law relationship of Mulcahy, although some linear cases were also encountered in the MODIS dataset. Deviations also arise between MODIS andMulcahy at higher wind speeds (>15ms1), whereMODIS-derived AOD returns lower values as compared to Mulcahy. The results also support the suggestion than wind generated sea spray, under moderately high winds, can rival anthropogenic pollution plumes advecting out into marine environments with wind driven AOD contributing to AOD values approaching 0.3.

The use of the pulse height analyser ultrafine condensation particle counter (PHA-UCPC) techniq The use of the pulse height analyser ultrafine condensation particle counter (PHA-UCPC) techniq

Date added: 09/22/2003
Date modified: 07/13/2009
Filesize: 458.51 kB

O’Dowd, C.D., P.P. Aalto, Y.J. Yoon, K. Hameri. The use the pulse height analyzer ultrafine condensation particle counter (PHA-UCPC) technique applied to sizing of nucleation mode particle of differing chemical composition. J. Aerosol. Sci. 2003. doi:10.1016/j.jaerosci.2003.08.003


Abstract


A modified white-light pulse-height analyser (PHA) TSI 3025 ultra-fine condensation particle counter (UCPC) is often used to provide fast response of aerosol size distributions between 3 and 10 nm since there is a monotonic link between initial aerosol size and nucleated droplet final size. The use of the PHA-UCPC for sizing nucleation mode particles depends on the droplet nucleation in the condenser chamber being somewhat independent of particle composition. Laboratory characterization of the PHA-UCPC for a range of chemical compositions, thought to be involved in atmospheric aerosol nucleation and growth, are presented here. Ammonium sulphate, pinic acid, cis-pinonic acid, malonic acid and an iodine oxide were studied and their PHA-UCPC calibration kernels are presented. It was found that all species possessed significantly different PHA responses. The results suggest that, unless the nano-particle chemical composition is known, then the PHA-UCPC cannot be used for measurements of aerosol size distributions. However, the PHA-UCPC, if used in parallel with mobility size distribution measurements, can help elucidate nano-particle chemical composition. Using the combination of mobility size distributions and the PHA-UCPC response during a nucleation and growth event over the boreal forest indicates that new particle formation, in this region, is driven by condensation of organic vapours.

Electrostatic Deposition in ionic Diffussion Electrostatic Deposition in ionic Diffussion

Date added: 08/31/1968
Date modified: 07/21/2009
Filesize: 1.69 MB
F. Anderson, P.J Nolan and T.C. O'Connor, Electrostatic Deposition in ionic Diffussion, Volume 66, Section A, No. 5, 1968

Abstract

 

Errors in the determination of ionic diffusion coefficients caused by the neglect of electrostatic deposition are examined. Correction formulae applicable to low ionic concentrations are derived for cylindrical channels. These are similiar to the Fuchs formulae for rectangular channels. Formulae applicable in the case of high ionic concentration are also derived.

For singly charged particles the correction tot the diffusion coefficient under the usual experimental conditions is about two or three per cent. The error becomes large when the number electronic charges per ion aproaches 100. Previous Dublin experiments with multiply charged nuclei are examined in this connection and corrections applied. The Corrections do not invalidate the main conclusion of these experiments that the Einstein equation B=D/KT does not apply in the absence of charge equilibrium.

The background atmospheric concentrations of cyclic perfluorocarbon tracers determined by negat The background atmospheric concentrations of cyclic perfluorocarbon tracers determined by negat

Date added: 08/07/2002
Date modified: 07/23/2009
Filesize: 164.57 kB

Simmonds, P. G., Greally, B. R., Olivier, S., Nickless, G., Cooke, K. M., and Dietz, R. N.  The background atmospheric concentrations of cyclic perfluorocarbon tracers determined by negative ion-chemical ionization mass spectrometry.  Atmos. Environ. 36, 2147-2156 (2002).


Abstract


The background atmospheric mixing ratios for a range of cyclic perfluorocarbons (cyclic-PFCs), widely used in atmospheric dispersion studies, have been measured by gas chromatography-mass spectrometry in negative ion-chemical ionization mode. Background concentrations range from <1fll-1 to >10fll-1, where femtolitre is expressed as parts in 1015 (ppqv). Because of their very long atmospheric lifetimes (>3000yr) the present day concentrations represent the accumulated emissions from all sources, although significant commercial production did not commence until the 1960s. Cyclic-PFCs are potent greenhouse gases; however, their atmospheric concentrations are currently so low as to make an insignificant contribution to global warming.

 

The phase-in and phase-out of European emissions of HCFC-141b and HCFC-142b .... at Mace Head, The phase-in and phase-out of European emissions of HCFC-141b and HCFC-142b .... at Mace Head,

Date added: 08/07/2007
Date modified: 07/23/2009
Filesize: 536.66 kB

DERWENT R. G. ; SIMMONDS P. G.; GREALLY B. R.  ; O'DOHERTY S. ; MCCULLOCH A. ; MANNING A. ; REIMANN S. ; FOLINI D. ; VOLLMER M. K.   , The phase-in and phase-out of european emissions of HCFC-141b and HCFC-142b under the Montreal Protocol : Evidence from observations at Mace Head, Ireland and Jungfraujoch, Switzerland from 1994 to 2004, Atmospheric Environment , 41, 4, pg 757-767 (2007)


Abstract

 

The mixing ratios of HCFC-141b (1,1-dichlorofluoroethane) and HCFC-142b (1-chloro-1,1-difluoroethane) have been rising steadily in baseline air at Mace Head, Ireland over the 10-year period from 1994 to 2004. These HCFCs are widely used replacements for the chlorofluorocarbons phased out under the Montreal Protocol and its subsequent amendments. Analysis of the HCFC content of regionally-polluted air arriving at Mace Head from the European continent shows that European emissions reached a peak during 2000-2001 and have declined subsequently, following the phase-out in their usage. European emissions of HCFC-141b have been further constrained by observations at the High-Alpine Jungfraujoch site. The reductions are consistent with the phase-out of HCFC production and use from the year 2001 onwards mandated by European regulations designed to exceed the requirements of the Montreal Protocol.

 

Relationships Between Extinction, Absorption, Backscattering, and Mass Content of Sulfuric Acid Aer. Relationships Between Extinction, Absorption, Backscattering, and Mass Content of Sulfuric Acid Aer.

Date added: 07/31/1980
Date modified: 07/06/2009
Filesize: 638.52 kB

Pinnick, R.G., Jennings, S.G., and Chylek, P. (1980)- Relationship between extinction, absorption, backscattering and mass content of sulphuric acid aerosols. J. Geophys. Res., 85, 4059-4066.


Abstract


Linear relationships between aerosol extinction, absorption, backscatter, and mass content are derived for polydispersions of sulfuric acid aerosols. These relationships are independent of the form of the size distribution and are a consequence of approximating the corresponding Mie efficiency factors (the extinction efficiency Qe, the absorption efficiency Qa, and the backscatter gain G) by linear functions of the particle size parameter x. The relationships are valid only at particular wavelengths that depend on the range of particle sizes present in a particular polydispersion. For example, at a wavelength λ=0.694 μm the relation between aerosol backscatter coefficient σbs (m-1 sr-1) and mass content M(g m-3) is σbs=0.048M for 75% sulfuric acid (25% water) aerosol, under the restriction that particles in the poly-dispersion have sizes not exceeding about 1.5 μm in radius. Possible applications of the relationships are (1) inference of path-integrated mass content of sulfuric acid aerosol (for example, the clouds of Venus) from an infrared laser transmission measurement through the aerosol cloud, (2) determination of sulfuric acid aerosol mass content at a particular point in an aerosol cloud from aerosol absorption measurements at that point with a CO2(λ=10.6 μm) laser spectrophone, (3) inference of path-integrated stratospheric aerosol mass from aerosol extinction measurements made by solar occultation for wavelengths λ=0.55 and 1 μm, and (4) inference of vertical profiles of stratospheric aerosol mass from ruby lidar (λ=0.694 μm) backscatter measurements.

, Detection of Cloud Base Height Using Jenoptik CHM15K and Vaisala CL31 Ceilometers , Detection of Cloud Base Height Using Jenoptik CHM15K and Vaisala CL31 Ceilometers

Date added: 02/08/2011
Date modified: 02/08/2011
Filesize: 8.25 MB

Martucci, G., C. Milroy, and C.D. O’Dowd, Detection of Cloud Base Height Using Jenoptik CHM15K and Vaisala CL31 Ceilometers, J. Atmos. Oceanic Techol. Vol. 27, No. 2, 305–318, 2010.


Abstract Twelve case studies of multi-layer cloud base height (CBH) retrievals from two co-located ceilometers (Vaisala CL31 and Jenoptik CHM15K) have been analysed. The studies were performed during the period from September to December 2008 at the Mace Head Research Station, Ireland. During the period of measurement, the two instruments provided vertical profiles of backscattered laser signal as well as the manufacturer’s operational cloud-base product. The cases selected covered a diverse range of cloud-cover conditions ranging from single to multiple cloud layers and from cloud base heights varying from only a few hundreds metres per day up to 3-5 km in few hours. The results show significant offsets between the two manufacturer-derived CBHs along with a considerable degree of scatter. Using a newly developed Temporal Height-Tracking (THT) algorithm applied to both ceilometers, significant improvement in the correlation between CBH derived from both instruments results in a correlation coefficient increasing to R2 = 0.997 (with a slope of 0.998) from R2 = 0.788 (with associated slope of 0.925). Also, the regression intercept (offset) is reduced from 160 m to effectively zero (-3 m). For the worst individual case study, using the THT algorithm resulted in the correlation coefficient improving from R2 = 0.52, using the manufacturer’s output, to R2 = 0.97 with a reduction in the offset reducing from 569 m to 32 m. Applying the THT algorithm to the backscatter profiles of both instruments led to retrieved cloud bases which are statistically consistent with each other and ensured reliable detection of CBH, particularly when inhomogeneous cloud fields were present and changing rapidly in time. The THT algorithm also overcomes multiple false cloud base detections, associated with the two instruments manufacturer’s output.

 

Field intercomparison of filter pack and impactor sampling for aerosol nitrate, ammonium, and s Field intercomparison of filter pack and impactor sampling for aerosol nitrate, ammonium, and s

Date added: 08/07/2004
Date modified: 07/24/2009
Filesize: 759.95 kB

Field Intercomparison of Filter Pack and Impactor Sampling for Aerosol Nitrate, Ammonium, and Sulphate at Coastal and Inland Sites, Z. Huang, R.M. Harrison, A.G. Allen, J.D. James, R.M. Tilling and J. Yin, Atmos. Res., 71, 215-232 (2004).


Abstract


An intercomparison has been performed on the coarse (>2.5 μm) and fine fraction (<2.5 μm) mass concentrations of particulate nitrate, ammonium, and sulphate determined simultaneously by filter pack and MOUDI samplers. Five intensive field campaigns have been carried out in summer and winter seasons, both at coastal sites (Mace Head, Ireland, and Tenerife, Spain) and at an inland site (University of Birmingham, West Midlands, UK). Comparison between particle sulphate measurements shows that sulphate measurements are the same with both filter pack and MOUDI, independent of sampling site or season. For both nitrate and ammonium, the MOUDI results are observed to be usually less than those from the filter pack, especially in the case of polluted air masses. During periods when the measured concentration products [NH3][HNO3] are low (<0.1 ppbv2), the ammonium concentrations obtained with the two samplers are matched very well with each other, but for nitrate, the filter pack system provides 15% higher mass concentrations than the MOUDI which are attributable to different inlet efficiencies. During more polluted periods, however, when there are high levels of gaseous ammonia and nitric acid in the atmosphere (with the measured concentration products [NH3][HNO3]>0.1 ppbv2), significantly negative sampling artefacts are observed for both nitrate and ammonium concentrations obtained with the impactor relative to the filter pack. Nevertheless, it is shown that both filter pack and MOUDI are capable of collecting ammonium nitrate from polluted air masses although the absolute efficiency is unknown. From the measurements obtained with the MOUDI in summertime at both coastal and inland sites, it is observed that about 64% of collected particle nitrate is present in the coarse (>2.5 μm) mode; but in wintertime, only about 29% of particle nitrate is found to reside in the coarse particles collected at the inland site. The lower efficiency of the MOUDI for ammonium nitrate relative to the Teflon filter is in marked contrast to the reported higher efficiency of the Berner impactor than the Teflon filter for sampling nitrate from polluted air.

 

Description of a biofluorescence optical particle counter Description of a biofluorescence optical particle counter

Date added: 05/09/2009
Date modified: 07/23/2009
Filesize: 371.82 kB
Ryan, O., R. Greaney, S.G. Jennings and C.D. O’Dowd, Description of a biofluorescence optical particle counter J.Q.S.R.T., DOI: 10.1016/j.jqsrt.2009.01.033, 2009

Abstract

 

A bioaerosol fluorescence detection system is being constructed using an ellipsoid reflector-based optical particle counter. The flux measuring device is to size submicron marine spray aerosol particles smaller than 100nm in diameter. It will simultaneously non-destructively excite and detect fluorescence from organic matter contained in the aerosol. Chlorophyll-a is the primary fluorophor target, used as a marker for detecting phytoplankton (or derivatives thereof) in the particles. Particles have been sized to 500nm in diameter and fluorescence detection testing is underway. The device will aid the quantification and identification of this organic material contained in marine spray aerosols, providing improved inputs into climate models and air quality assessments.

Uptake of methanol to the North Atlantic Ocean surface Uptake of methanol to the North Atlantic Ocean surface

Date added: 08/06/2004
Date modified: 07/23/2009
Filesize: 417.44 kB

Carpenter, L. J., A. C. Lewis, J. R. Hopkins, K. A. Read, I. D. Longley, and M. W. Gallagher (2004), Uptake of methanol to the North Atlantic Ocean surface, Global Biogeochem. Cycles, 18, GB4027, doi:10.1029/2004GB002294.


Abstract


An anticorrelation between atmospheric methanol (CH3OH) concentrations and wind speed and a positive correlation between dimethylsulphide (DMS) concentrations and wind speed have been observed at the coastal air monitoring site of Mace Head in Ireland, during a period of cyclonic activity in which the averaged surface wind speed changed substantially as a low-pressure system evolved over the northeast Atlantic. These observations suggest a net air-to-sea flux of CH3OH. This conclusion is supported by the good agreement between the wind speed dependencies of the measured gas concentrations and theoretical predictions using wind-induced turbulent gas transfer velocities of DMS and CH3OH calculated from a resistance model, embedded in a photochemical box model. For a wind speed of 8 m s−1, an ocean deposition rate of methanol of between 0.02 and 0.33 cm s−1 is calculated, with a best estimate of 0.09 cm s−1, in good agreement with deposition rates used in global models and derived from atmospheric budgets. The large uncertainty in the calculated deposition rates is due almost entirely to the uncertainty in the degree of saturation of methanol in the surface ocean, highlighting the critical requirement for measurements of methanol in seawater. Owing to the dependence on wind speed, the deposition rates calculated showed substantial range and the calculated contribution of ocean deposition to total loss of CH3OH (ocean uptake and gas phase OH oxidation) varied from approximately 20% to 60%.

 

Trends over a 20-year period from 1987 to 2007 in surface ozone at the atmospheric research sta Trends over a 20-year period from 1987 to 2007 in surface ozone at the atmospheric research sta

Date added: 08/07/2007
Date modified: 07/23/2009
Filesize: 205.45 kB

Derwent, R. G., Simmonds, P. G., Manning, A. J., and Spain, T. G.: Trends over a 20-year
period from 1987–2007 in surface ozone at the atmospheric research station, Mace Head,
15 Ireland, Atmos. Environ., 41, 9091–9098, 2007.


Abstract


Hourly measurements of baseline ozone at the Mace Head Atmospheric Research Station on the Atlantic Ocean coast of Ireland are observed when unpolluted air masses are advected to the station from across the North Atlantic Ocean. Monthly mean ozone mixing ratios in baseline air masses have risen steadily during the 1980s and 1990s reaching unprecedented levels during the early months of 1999. During the 2000s, baseline ozone mixing ratios have shown evidence of decline and stabilisation. Over the entire 20-year 1987-2007 period, the trend in annual baseline ozone has been +0.31±0.12(2-σ)ppbyear-1 and is highly statistically significant. Trends have been highest in the spring months and lowest in the summer months, producing a significant increase in the amplitude of the seasonal cycle. Over the shorter 1995-2007 period, we demonstrate how the growth to peak in 1999 and the subsequent decline have been driven by boreal biomass burning events during 1998/1999 and 2002/2003. The 2000s have been characterised by relatively constant baseline ozone and CH4 levels and these may be a reasonable guide to future prospects, at least in the short term.

 

The spatial distribution of the reactive iodine species IO from simultaneous active and passive DOAS The spatial distribution of the reactive iodine species IO from simultaneous active and passive DOAS

Date added: 03/02/2010
Date modified: 03/03/2010
Filesize: 1.87 MB

Seitz, K.,  J. Buxmann, D. Pöhler, T. Sommer, J. Tschritter, T. Neary, C. O’Dowd, and U. Platt,  The spatial distribution of the reactive iodine species IO from simultaneous active and passive DOAS observations, Atmos. Chem. Phys., 10, 2117–2128, 2010


 

Abstract. :

We present investigations of the reactive iodine species (RIS) IO, OIO and I
2 in a coastal region from a field  campaign simultaneously employing active long path differential optical absorption spectroscopy (LP-DOAS) as well as passive multi-axis differential optical absorption spectroscopy (MAX-DOAS). The campaign took place at the Martin Ryan Institute (MRI) in Carna, County Galway at the IrishWest Coast about 6 km south-east of the atmospheric research station Mace Head in summer 2007. In order to study the horizontal distribution of the trace gases of interest, we established two almost parallel active LP-DOAS light paths, the shorter of 1034m length just crossing the intertidal area, whereas the longer one of 3946m length also crossed open water during periods of low tide. In addition we operated two passive Mini-MAX-DOAS instruments with the same viewing direction. While neither OIO nor I2 could be unambiguously identified with any of the instruments, IO could be detected with active as well as passive DOAS. The IO column densities seen at both active LP-DOAS light paths are almost the same. Thus it can be concluded that coastal IO is almost exclusively located in the intertidal area, where we detected mixing ratios of up to 29±8.8 ppt (equivalent to pmol/mol). Nucleation events with particle concentrations of 106 cm3 particles were observed each day correlating with high IO mixing ratios. Therefore we feel that our detected IO concentrations confirm the results of model studies, which state that in order to explain such particle bursts, IO mixing ratios of 50 to 100 ppt in so called “hot-spots” are required.

The use of trajectory cluster analysis to interpret trace gas measurements at Mace Head The use of trajectory cluster analysis to interpret trace gas measurements at Mace Head

Date added: 08/06/2000
Date modified: 07/23/2009
Filesize: 881.19 kB

Cape, J.N., J Methven and L.E Hudson, The use of trajectory cluster analysis to interpret trace gas measurements at Mace Head, Ireland, Atmos. Environ., 34, 3651-3663, 2000, (Ser. No. ACP088).


Abstract

 

A first step in interpreting the wide variation in trace gas concentrations measured over time at a given site is to classify the data according to the prevailing weather conditions. In order to classify measurements made during two intensive field campaigns at Mace Head, on the west coast of Ireland, an objective method of assigning data to different weather types has been developed. Air-mass back trajectories calculated using winds from ECMWF analyses, arriving at the site in 1995-1997, were allocated to clusters based on a statistical analysis of the latitude, longitude and pressure of the trajectory at 12h intervals over 5 days. The robustness of the analysis was assessed by using an ensemble of back trajectories calculated for four points around Mace Head. Separate analyses were made for each of the 3 years, and for four 3-month periods. The use of these clusters in classifying ground-based ozone measurements at Mace Head is described, including the need to exclude data which have been influenced by local perturbations to the regional flow pattern, for example, by sea breezes. Even with a limited data set, based on 2 months of intensive field measurements in 1996 and 1997, there are statistically significant differences in ozone concentrations in air from the different clusters. The limitations of this type of analysis for classification and interpretation of ground-based chemistry measurements are discussed.

 

The North Atlantic Marine Boundary Layer Experiment (NAMBLEX). Discussion The North Atlantic Marine Boundary Layer Experiment (NAMBLEX). Discussion

Date added: 08/30/2008
Date modified: 07/23/2009
Filesize: 8.12 MB

Heard, D. E., K. A. Read, J. Methven, S. Al-Haider, W. J. Bloss, G. P. Johnson, M. J. Pilling, P. W. Seakins, S. C. Smith, R. Sommariva, J. C. Stanton, T. J. Still, B. Brooks, G. De Leeuw, A. V. Jackson, J. B. McQuaid, R. Morgan, M. H. Smith, L. J. Carpenter, N. Carslaw, J. R. Hamilton, J. Hopkins, J. D. Lee, A. C. Lewis, R. M. Purvis, D. J. Wevill, N. Brough, T. Green, G. Mills, S. A. Penkett, J. M. C. Plane, A. Saiz-Lopez, D. Worton, P. S. Monks, Z. Fleming, A. R. Rickard, M. Alfarra, J. D. Allan, K. Bower, H. Coe, M. Cubison, M. Flynn, G. McFiggans, M. Gallagher, E. G. Norton, C. D. O'Dowd, J. Shillito, D. Topping, G. Vaughan, P. Williams, M. Bitter, S. M. Ball, R. L. Jones, I. M. Povey, S. O'Doherty, P. G. Simmonds, A. Allen, R. P. Kinnersley, D. C. S. Beddows, M. Dall'Osto, R. M. Harrison, R. J. Donovan, M. R. Heal, S. G. Jennings, C. Noone and G. Spain, The North Atlantic Marine Boundary Layer Experiment (NAMBLEX). Overview of the campaign held at Mace Head, Ireland, in summer 2002, Atmospheric Chemistry and Physics Discussions, Vol. 5, pp 12177-12254, 2005.


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.

 

Volatility of aerosols at Mace Head on the west coast of Ireland Volatility of aerosols at Mace Head on the west coast of Ireland

Date added: 09/03/1990
Date modified: 07/08/2009
Filesize: 668.3 kB

Jennings, S.G., and O'Dowd, C.D. (1990). - Volatility of aerosols at Mace Head on the west coast of Ireland. J. Geophys. Res., 95, 13,937 - 13,948.


Abstract


Volatile properties of maritime and modified maritime aerosol were measured at the remote site at Mace Head (53°19′N, 9°54′W) on the west coast of Ireland, located on the eastern edge of the North Atlantic Ocean. The volatility measurements were made with a light-scattering counter equipped with a temperature-controlled heated inlet. The work extends the temperature range from 300°C to 850°C for the first time for aerosol volatility studies. Representative measurements made over the period of about a year show that the submicrometer particles with radius <0.2 μm are highly volatile for the maritime aerosol and show temperature fractionation features of ammonium sulfate (or ammonium bisulfate). It is estimated that 85–95% of this size fraction (by volume) is composed of these sulfates. For the higher temperatures, temperature-fractionation characteristics of sodium chloride are shown for the supermicron and also the submicron maritime particles. About 80% of the particle size interval of 0.3–1.5 μm radius is composed of sodium chloride. The temperature profile curves for the modified maritime aerosol, which has made a partial traverse overland, do not display definitive features characteristic of known atmospheric constituents such as ammonium sulfate or sodium chloride, but rather properties indicative of mixtures of these species with other unknown constituents. For both airmasses, between about 5% and 30% (by volume) of the aerosol particles remain involatile at least up to a temperature of 850°C.

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

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

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


Abstract


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

 

Global scale emission and distribution of sea-spray aerosol: Global scale emission and distribution of sea-spray aerosol:

Date added: 03/03/2010
Date modified: 03/03/2010
Filesize: 1.37 MB

Vignati,, E.,  M. C. Facchini, M. Rinaldi, C. Scannell, D. Ceburnis, J. Sciare, M. Kanakidou, S. Myriokefalitakis, F. Dentener and C. D. O’Dowd , Global scale emission and distribution of sea spray aerosol: sea-salt and organic enrichment, Atmos. Envniron. 44,, doi:10.1016/j.atmosenv.2009.11.013  , 2010.


Abstract

The chemical composition of marine aerosols as a function of their size is an important parameter for theevaluation of their impact on the global climate system. In this work we modelled fine p

article organic matter emitted by sea spray processes and its influence on the aerosol chemical properties at the global scale using the off-line global Chemistry-Transport Model TM5. TM5 is coupled to a microphysical aerosol dynamics model providing size resolved information on particle masses and numbers. The mass of the emitted sea spray particles is partitioned between water insoluble organic matter (WIOM) and sea salt components in the accumulation mode using a function that relates the emitted organic fraction to the surface ocean chlorophyll-a concentrations. The global emission in the sub-micron size range of  organic matter by sea spray process is 8.2 Tg yr1, compared to 24 Tg fine yr1 sea-salt emissions. When  the marine sources are included, the concentrations of modelled primary particulate organic matter (POM) increase mainly over the oceans. The model predictions of WIOM and sea salt are evaluated  against measurements carried out at Mace Head (Northern Hemisphere) and Amsterdam Island  (Southern Hemisphere), showing that in clean marine conditions WIOM marine emissions contribute  significantly to POM values.  
fine particle organic matter emitted by sea spray processes and its influence on the aerosol chemical properties at the global scale using the off-line global Chemistry-Transport Model TM5. TM5 is coupled to a microphysical aerosol dynamics model providing size resolved information on particle masses and numbers. The mass of the emitted sea spray particles is partitioned between water insoluble organic matter (WIOM) and sea salt components in the accumulation mode using a function that relates the emitted organic fraction to the surface ocean chlorophyll-a concentrations. The global emission in the sub-micron size range of  organic matter by sea spray process is 8.2 Tg yr1, compared to 24 Tg fine yr1 sea-salt emissions. When  the marine sources are included, the concentrations of modelled primary particulate organic matter (POM) increase mainly over the oceans. The model predictions of WIOM and sea salt are evaluated  against measurements carried out at Mace Head (Northern Hemisphere) and Amsterdam Island  (Southern Hemisphere), showing that in clean marine conditions WIOM marine emissions contribute  significantly to POM values.
fine particle organic matter emitted by sea spray processes and its influence on the aerosol chemical properties at the global scale using the off-line global Chemistry-Transport Model TM5. TM5 is coupled to a microphysical aerosol dynamics model providing size resolved information on particle masses and numbers. The mass of the emitted sea spray particles is partitioned between water insoluble organic matter (WIOM) and sea salt components in the accumulation mode using a function that relates the emitted organic fraction to the surface ocean chlorophyll-a concentrations. The global emission in the sub-micron size range of  organic matter by sea spray process is 8.2 Tg yr1, compared to 24 Tg fine yr1 sea-salt emissions. When  the marine sources are included, the concentrations of modelled primary particulate organic matter (POM) increase mainly over the oceans. The model predictions of WIOM and sea salt are evaluated  against measurements carried out at Mace Head (Northern Hemisphere) and Amsterdam Island  (Southern Hemisphere), showing that in clean marine conditions WIOM marine emissions contribute  significantly to POM values.

The role of VOC oxidation products in continental new particle formation The role of VOC oxidation products in continental new particle formation

Date added: 08/01/2007
Date modified: 07/08/2009
Filesize: 693.16 kB

Laaksonen, A., M. Kulmala, C.D. O’Dowd, J. Joutsensaari, P. Vaattovaara, S. Mikkonen, K.E.J. Lehtinen, L. Sogacheva, M. Dal Maso, P. Aalto, T. Petäjä, A. Sogachev, Y. J. Yoon, H. Lihavainen, D. Nilsson, M. C. Facchini, F. Cavalli, S. Fuzzi, T. Hoffmann, F. Arnold, M. Hanke, K. Sellegri, B. Umann, W Junkermann, H. Coe, J. D. Allan, M. R. Alfarra, D.R. Worsnop, M.-L. Riekkola, T. Hyötyläinen and Y Viisanen., The role of VOC oxidation products in continental new particle formation, Atmos. Chem. And Phys. Discuss., 2007.


Abstract


Aerosol physical and chemical properties and trace gas concentrations were measured during the QUEST field campaign in March–April, 2003, in Hyytiälä, Finland. Our aim was to understand the role of oxidation products of VOC's such as mono- and sesquiterpenes in atmospheric nucleation events. Particle chemical compositions were measured using the Aerodyne Aerosol Mass Spectrometer, and chemical compositions of aerosol samples collected with low-pressure impactors and a high volume sampler were analysed using a number of techniques. The results indicate that during and after new particle formation, all particles larger than 50 nm in diameter contained similar organic substances that are likely to be mono- and sesquiterpene oxidation products. The oxidation products identified in the high volume samples were shown to be mostly aldehydes. In order to study the composition of particles in the 10–50 nm range, we made use of Tandem Differential Mobility Analyzer results. We found that during nucleation events, both 10 and 50 nm particle growth factors due to uptake of ethanol vapour correlate strongly with gas-phase monoterpene oxidation product (MTOP) concentrations, indicating that the organic constituents of particles smaller than 50 nm in diameter are at least partly similar to those of larger particles. We furthermore showed that particle growth rates during the nucleation events are correlated with the gas-phase MTOP concentrations. This indicates that VOC oxidation products may have a key role in determining the spatial and temporal features of the nucleation events. This conclusion was supported by our aircraft measurements of new 3–10 nm particle concentrations, which showed that the nucleation event on 28 March 2003, started at the ground layer, i.e. near the VOC source, and evolved together with the mixed layer. Furthermore, no new particle formation was detected upwind away from the forest, above the frozen Gulf of Bothnia.

Trace elements in the atmosphere over the North Atlantic Trace elements in the atmosphere over the North Atlantic

Date added: 08/06/1995
Date modified: 07/23/2009
Filesize: 1.49 MB

Arimoto, R., R. A. Duce, B. J. Ray, W. G. Ellis Jr., J. D. Cullen, and J. T. Merrill (1995), Trace elements in the atmosphere over the North Atlantic, J. Geophys. Res., 100(D1), 1199–1213.


Abstract


The concentrations of trace elements in aerosol particles from the atmosphere over the North Atlantic Ocean were determined as part of a program designed to characterize the chemical climatology of the region. For these studies, which were part of the Atmosphere-Ocean Chemistry Experiment (AEROCE), 2 years of samples were collected at Tudor Hill, Bermuda (BTT), and at Ragged Point, Barbados (BAT); and 1 year of samples was collected at Mace Head, Ireland (MHT) and at the Izaña Observatory, Tenerife, Canary Islands (IZT). One major component of the aerosol was atmospheric dust, and the ranking for the median mineral dust concentrations as represented by aluminum was BAT > IZT > BTT > MHT. The Al concentrations at BAT, IZT, and BTT ranged over 4 orders of magnitude, i.e., from 0.001 to 10 μg m−3. At MHT the maximum dust concentrations were about a factor of 10 lower than at the other sites, but the lower end of the range in dust concentrations was similar at all sites. The mineral dust concentrations generally were highest in summer, and the flux of atmospheric dust was dominated by sources in North Africa. The elements showing clear enrichments over the concentrations expected from sea salt or crustal sources were I, Sb, Se, V, and Zn. At Izaña, which is in the free troposphere (elevation ∼2360 m), the concentrations of Se and I were much lower than at the boundary layer sites; this difference between sites most likely results from the marine emissions of these elements. The impact of pollution sources on trace element concentrations was evident at all sites but varied with season and location. The concentrations of elements originating from pollution sources generally were low at Barbados. Analyses of trace element ratios indicate that there are large-scale differences in the pollution emissions from North America versus those from Europe and Africa. Emissions from pyrometallurgical industries, steel and iron manufacturing, and possibly biomass burning are more evident in the atmospheric samples influenced by transport from Europe and Africa.

 

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

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

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


Abstract

 

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

The variation of the mixing state of Saharan dust particles with atmospheric transport. The variation of the mixing state of Saharan dust particles with atmospheric transport.

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 1.65 MB

Dall’Osto, R.M. Harrison, E. J.  Highwood, C. O’Dowd, D. Ceburnis, X. Querol and E. P. Achterberg, The variation of the mixing state of Saharan dust particles with atmospheric transport. Atmos. Env., doi:10.1016/j.atmosenv.2010.05.030, 2010,


Mineral dust is an important aerosol species in the Earth

 

s atmosphere and has a major source within North Africa, of which the Sahara forms the major part. Aerosol Time of Flight Mass Spectrometry (ATOFMS) is first used to determine the mixing state of dust particles collected from the land surface in the Saharan region, showing low abundance of species such as nitrate and sulphate internally mixed with the dust mineral matrix. These data are then compared with the ATOFMS single particle mass spectra of Saharan dust particles detected in the marine atmosphere in the vicinity of the Cape Verde islands, which are further compared with those from particles with longer atmospheric residence sampled at a coastal station at Mace Head, Ireland. Saharan dust particles collected near the Cape Verde  Islands showed increased internally mixed nitrate but no sulphate, whilst Saharan dust particles collected on the coast of Ireland showed a very high degree of internally mixed secondary species including nitrate, sulphate and methanesulphonate. This uptake of secondary species will change the pH  and hygroscopic properties of the aerosol dust and thus can influence the budgets of other reactive gases, as well as influencing the radiative properties of the particles and the availability of metals for

dissolution

Volatility of Elemental Carbon Volatility of Elemental Carbon

Date added: 07/31/1994
Date modified: 07/23/2009
Filesize: 423.53 kB
Jennings, S.G., O'Dowd, C.D., Cooke, W.F., Sheridan, P.J. and Cachier, (1994). - Volatility of elemental carbon. Geophys. Res. Letts., 21, 1719 - 1722.

Abstract


A volatility technique whereby aerosol particles are heated to the relatively high temperature of 860 °C is used to infer the presence of elemental carbon in polluted air masses in the vicinity of the west coast of Ireland. The volume of elemental carbon for submicrometre sized particles contained in the aerosol is estimated from the fall off in number concentration at a critical onset temperature of about 730 −735 °C, as also obtained for laboratory carbon ink aerosol. The technique permits determination of the elemental carbon volume percentage of the total fine aerosol volume, and an estimation of the abundance of elemental carbon contained within the black carbon fraction of the atmospheric aerosol. Supplementary black carbon mass concentration measurements were obtained using a thermal method and an aethalometer absorption method. The work suggests that elemental carbon can be identified using the volatility technique and that it can yield size-segregated information on the fraction of elemental carbon in atmospheric aerosol.

Novel iodine chemistry in the marine boundary layer Novel iodine chemistry in the marine boundary layer

Date added: 08/07/2004
Date modified: 07/23/2009
Filesize: 189.32 kB

Saiz-Lopez, A., and J. M. C. Plane (2004), Novel iodine chemistry in the marine boundary layer, Geophys. Res. Lett., 31, L04112, doi:10.1029/2003GL019215.


Abstract


The atmospheric chemistry of iodine is important for several reasons, including the influence of iodine oxides on the oxidising capacity of the troposphere, the formation of new particles, and the enrichment of iodine in marine aerosols and the transport of this essential dietary element to the continents. It is shown here that a substantial iodine source is I2, most likely emitted from macro-algae at low tide. This source accounts for the daytime production of new particles in the coastal marine boundary layer, and also explains the discovery of significant night-time levels of iodine oxides.

 

Effect of Horizontal Resolution on Meteorology and Air-Quality Prediction with a Regional Scale Mode Effect of Horizontal Resolution on Meteorology and Air-Quality Prediction with a Regional Scale Mode

Date added: 05/12/2011
Date modified: 05/12/2011
Filesize: 4.49 MB

Varghese, S., B. Langmann and C. D. O’Dowd, Effect of Horizontal Resolution on Meteorology and Air-Quality Prediction with a Regional Scale Model, Atmos. Res., doi:10.1016/j.atmosres.2011.02.007, 2011

 


 

Horizontal resolution sensitivity can significantly contribute to the uncertainty in predictions of meteorology and air-quality from a regional climate model. In the study presented here, astate-of-the-art regional scale atmospheric climate-chemistry-aerosol model REMOTE is used to understand the influence of spatial model resolutions of 1.0°, 0.5° and 0.25° on predicted meteorological and aerosol parameters for June 2003 for the European domain comprising North-east Atlantic and Western Europe. Model precipitation appears to improve with resolution while wind speed has shown best results for 0.25° resolution for most of the stations compared with ECAD data. Low root mean square error and spatial bias for surface pressure, precipitation and surface temperature show that the model is very reliable. Spatial and temporal variation in black carbon, primary organic carbon, sea-salt and sulphate concentrations and their burden are presented. In most cases, chemical species concentrations at the surface show no particular trend or improvement with increase in resolution. There has been a pronounced influence of horizontal resolution on the vertical distribution pattern of some aerosol species. Some of these effects are due to the improvement in topographical details, flow characteristics and associated vertical and horizontal dynamic processes. The different sink processes have contributed very differently to the various aerosol pecies in terms of deposition (wet and dry) and sedimentation which are strongly linked to the meteorological processes. Overall, considering the formance of meteorological parameters and chemical  pecies concentrations, a horizontal model resolution of 0.5° is suggested to achieve easonable results within the limitations of this model.

Vertical Inhomogeneity in Atmospheric Fog and Haze and it's effects on IR extinction Vertical Inhomogeneity in Atmospheric Fog and Haze and it's effects on IR extinction

Date added: 08/01/1978
Date modified: 07/08/2009
Filesize: 2.32 MB
Pinnick, R. G.; Hoihjelle, D. L.; Stenmark, E. B.; Lindberg, James D., Vertical inhomogeneity in atmospheric fog and haze and its effects on infrared extinction, J. Opt. Soc. Am, Vol.68, Page 540

Abstract

 

The presence of atmospheric fog and haze is important to radiative transfer in the atmosphere. For quantitative estimates of scattering and absorption by fod and haze particles, the size distribution is needed. Previously, fog and haze particulate size distributions have been measured by impaction techniques (Garland, 1971; Pilie, 1975; Krasikov and Chikirova, 1956; Kumai, 1973; low, 1975; May, 1961; barteneva and Polyakova, 1965; and Goodman, 1977), by collection of particles on spiderwebs (Arnulf et al., 1957), by a laser hologram camera (Kumkelm, 1971), and by light-scattering single particle counters (Eldridge, 1961; Laktionov, 1967). All of these techniques have serious limitations which restrict their usefulness and require measurements made with them to be regarded with caution. For example, impaction techniques involve laborious microsope measuremtn of droplets or droplet replicas, and corrections must be made to obtain true droplet size. Furthermore, impaction collection efficiencies must be applied to obtain relative particle concentrations.

 

In this article we present measurements of the size distribution of fog and haze particles made with a balloon-borne light-scattering single-particle counter, with emphasis on their effect on Infrared radiation. The primary advantages of using a light-scattering counter is that the measurement is donw in situ in real time, with minimal disturbance to the particles during measurement. Also, measurment of vertical structure is possible with this technique because a statistically significant size distribution measurement can be completed in a relatively short time (on the order of 1/2 minute), permitting a vertical upleg and lownleg to 200m altitude to be completed in 15 to 30 minutes. Measurements made during upleg and downleg portions of each tranverse show that temporal changes during such times scales were relatively small compared to vertical changes for most measurement periods.

Results from measurement of four haze and fog profiles presented here are typical of 19 profiles measured during February 1976 near Grafenwohr, a town located 100 km north of Nurnberg near the eastern border of West Germany. The local terrain consists of rollong hills and is partially forested; some of the land is tilled for farming.

Volatility of Aerosols in the Arid Southwestern United States Volatility of Aerosols in the Arid Southwestern United States

Date added: 07/31/1987
Date modified: 07/08/2009
Filesize: 1.19 MB

Pinnick, R.G., Jennings, S.G., and Fernandez, G. (1987). - Volatility of aerosols in the arid south western United States. J. Atmos. Sci., 44, 391 - 400.


Abstract

 

Volatile properties of aerosols at an isolated rural site in south-central New Mexico were measured with a light-scattering particle counter equipped with a temperature-controlled heated inlet. Intermittent measurements throughout a one-year period show that submicron particles are highly volatile and display temperature-fractionation characteristics of ammonium sulfate or bisulfate. It is estimated that 60-98 percent of the submicron aerosol fraction (by mass) is composed of these sulfates. Larger supermicron particles with radii greater than 0.4 micron, which are composed mostly of quartz and clay minerals of soil origin, are relatively involatile.

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

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

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


Abstract

 

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

 

Timescale analysis of marine boundary layer aerosol evolution Lagrangian case studies Timescale analysis of marine boundary layer aerosol evolution Lagrangian case studies

Date added: 08/06/2000
Date modified: 07/08/2009
Filesize: 247.97 kB

Hoell, C., C.D. O'Dowd, S.R. Osborne, and D.W. Johnson, Timescale Analysis of Marine Boundary Layer Aerosol Evolution: Lagrangian Case Studies Under Clean and Polluted Cloudy Conditions. Tellus, 52B,423-438, 2000


Abstract


Significant changes were observed in the sub-micron aerosol size distribution during a clean and a polluted Lagrangian study of marine boundary layer (MBL) aerosol and meteorological evolution during ACE-2. These changes were accompanied by significant alterations in boundary layer meteorology and structure. The clean case (LAG1) shows a reduction in the fine mode aerosol from 1050 cm-3 to 750 cm-3 and an increase in the accumulation mode concentration from 76 cm-3 to 162 cm-3 over 26 h. Dominant meteorological features during the same period comprised a reduction in boundary layer height from ap1500 m to ap800 m and an increase in the surface layer wind speed from 5 m s-1 to 15 m s-1. A detailed time-scale analysis, based upon measured data and including processes such as coagulation, condensation, deposition, chemical processing, sea-salt flux and entrainment, suggests that the dominant loss process for fine mode aerosol is coagulation, while the enhancement of accumulation mode aerosol can be almost totally ascribed to enhanced sea-salt aerosol flux into the reduced mixed layer volume. Aerosol size distributions from the polluted Lagrangian (LAG2) indicated little growth in particle diameter, and both fine and accumulation mode were observed to decrease in concentration from 2700 cm-3 to 1150 cm-3 and from 670 cm-3 to 430 cm-3 in 26 h, respectively. Dilution with cleaner free tropospheric air as the boundary layer height increased from ap500 m to >1000 m is suggested to be the primary factor relating to reduced aerosol concentrations in this case. To a smaller extent, coagulation and precipitation scavenging were calculated to be of some importance. For both Lagrangian case studies, meteorological changes, followed by physical aerosol-cloud interactions, appear to have the greatest influence on the MBL aerosol size distribution and number concentration over the given time-scale.

 

Vertical Structure in Atmospheric Fog and Haze and Its Effects on Visible and Infrared Extinction Vertical Structure in Atmospheric Fog and Haze and Its Effects on Visible and Infrared Extinction

Date added: 08/01/1978
Date modified: 07/08/2009
Filesize: 1004.22 kB
R. G. Pinnick, D. L. Hoijelle, G. Fernandez, E. B. Stenmark, J. D. Lindberg, G. B. Hoidale, and S. G. Jennings,, "Vertical structure in atmospheric fog and haze and its effects on visible and infrared extinction," J. Atmos. Sci.35, 2020 (1978).

Abstract

 

Vertical structure of the size distribution and number concentration of particulates in atmospheric fog and haze near Grafenwöhr, West Germany, were measured with a balloonborne light-scattering aerosol counter for periods spanning parts of eight days in February 1976. For haze (5 km visibility) conditions, little vertical variation is seen; but for low visibility (<1 km) fog conditions, significant vertical increases in concentration of droplets with radii larger than 4 μm are seen over the first 150 m altitude. For haze, the particle size distribution is approximated by a log-normal with geometric mean radius rg ≈ 0.2 μm and geometric standard deviation  σo ≈1.9. For fog, a bimodal distribution is found with a relative maximum for the larger particle mode at radii of 4 to 6 μm and corresponding values rg ≈ 5 m and σo ≈1.6; the smaller particle mode has values of rg ≈ 0.3 μm to rg ≈ 0.6 μm and σo  ≈1.8 to ≈2.5. Liquid water content values for haze and fog range from 10-4 to 0.45 g m-3. Extinction calculated from the particle size distributions shows an approximate 1/ λ wavelength dependence for haze conditions, but nearly neutral (wavelength independent) extinction for heavy fog. A correlation exists between calculated particulate extinction and calculated liquid water content, independent of particle size distribution, for the fogs and hues studied.

Weather: Understanding rainfall Weather: Understanding rainfall

Date added: 08/01/1971
Date modified: 07/22/2009
Filesize: 336.23 kB
Weather: Understanding rainfall,1971
Abstract

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

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

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


Abstract


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

The Relative Contribution of sub and super micron particles to aerosol light scattering .. The Relative Contribution of sub and super micron particles to aerosol light scattering ..

Date added: 07/31/2002
Date modified: 07/08/2009
Filesize: 905.05 kB

Christoph Kleefeld, Colin O'Dowd, Sarah O'Reilly, S. Gerard Jennings, Pasi Alto, Edo, Becker, Gerard Kunz, Gerrit de Leeuw.The Relative Contribution of sub and super micron particles to aerosol light scattering in the marine boundary layer (MBL), J. Geophys. Res., 107, 10.1029/2000JD000262, 2002.


Abstract

 

Measurements of the aerosol light scattering coefficient (ssp) at a wavelength of l = 550 nm were conducted at a coastal atmospheric research station in the east Atlantic Ocean during June 1999. Size distribution measurements between diameters of 3 nm and 40 mm (at ambient humidity) were used to derive scattering coefficients from Mie theory. The calculated scattering coefficients were about a factor of 7.4 higher than the measured scattering coefficients. The discrepancy was explained by a reduced cutoff of the sampling system at particle diameters between 6 and 8 mm, dependent on wind speed. The calculated aerosol scattering was about 1 order of magnitude higher than previously reported measurements in the MBL and is attributed to supermicrometer particles at sizes d > 10 mm dominating aerosol scattering. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0360 Atmospheric Composition and Structure: Transmission and scattering of radiation; 3359 Meteorology and  Atmospheric Dynamics: Radiative processes; KEYWORDS: light scattering, sea-salt aerosol, marine boundary layer, particle size distribution, Mie theory

 

Use of an Average complex refractive index in atmospheric propagation calculations Use of an Average complex refractive index in atmospheric propagation calculations

Date added: 08/01/1978
Date modified: 07/08/2009
Filesize: 932.35 kB
. B. Gillespie, S. G. Jennings, and J. D. Lindberg, "Use of an average complex refractive index in atmospheric propagation calculations," Appl. Opt. 17, 989-991 (1978)

Abstract

 

In most atmospheric propagation calculation it is generally ssumed that atmospheric dust is composed of homogeneous spherical particles all with the same average complex refractive index and all distributed by the same size distribution. As pointed out by Bergstrom, it is perhaps more realisitc to assume that since diiferent optical constants and each component will have an associated size distribution characteristic of its production. In particular, the free carbon type particles and the soil derived particles should be different. Previous work in our laboratory  with commericallly available cascade impactors has shown that, for some minerals characteristic of the local envirorment, the imaginary refractive index of desert dust is a strong function of particle size.

The Vertical structure of aerosol and its relationship to boundary-layer thermodynamics and ove The Vertical structure of aerosol and its relationship to boundary-layer thermodynamics and ove

Date added: 08/06/1996
Date modified: 07/08/2009
Filesize: 3.84 MB

O'DOWD C. D. ; SMITH M. H., The vertical structure of aerosol and its relationship to boundary-layer thermodynamics over the rural UK, Quarterly Journal of the Royal Meteorological Society, 1996, vol. 122 (B), no 536, pp. 1799-1814


Abstract


The vertical structure of aerosol, covering sizes from 0.05-4 μm radius, was examined under conditions of subsidence during winter and summer over the rural UK. Under well-mixed boundary layer conditions, dry accumulation mode aerosol was found to be well mixed with height. During the winter campaigns, nocturnal cooling resulted in the development of a stable surface layer, typically 100 m in depth, within which the surface emitted pollutants became trapped leading to concentrations significantly greater than that observed in the mixed boundary layer above it. Under stable boundary-layer conditions, the aerosol and water vapour vertical profiles exhibited strong negative gradients with height and were indicative of suppressed turbulence associated with stable boundary-layer conditions. During summer, the boundary layer was normally decoupled and possessed two cloud layers: cumuli forming just below, and penetrating the surface-layer inversion; and stratocumulus occupying the region under the boundary-layer capping inversion. Aerosol profiles under decoupled conditions exhibited considerable variability with peak concentrations being observed in the vicinity of cloud edges. Average aerosol concentrations in the main boundary-layer ranged from 209-651 cm-3 and 0.89-4.3 μm-3 cm-3 for dry number and volume respectively, whilst concentrations and volumetric loadings of 239-2430 cm-3 and 1.1-13.5 μm3 were encountered in surface layers. The majority of the aerosol number and mass concentrations were almost exclusively derived from the size range 0.05-0.2 μm radius with mode radii often occurring at 0.1 μm or larger. By comparison, free tropospheric aerosol possessed typically an order of magnitude lower concentrations and mass with an associated mode radius of 0.05-0.06 μm or less.

 

Ultrafine particle size distributions at hyytiälä boreal forest site and at a coastal site in M Ultrafine particle size distributions at hyytiälä boreal forest site and at a coastal site in M

Date added: 08/07/2000
Date modified: 07/23/2009
Filesize: 120.05 kB
J. M. MAKELA, P. AALTO, M.VAKEVA, K. HJ~MERI, I.K.KOPONEN, C.D.O'DOWD, M. KULMALA,ULTRAFINE PARTICLE SIZE DISTRIBUTIONS AT HYYTIP, LA BOREAL FOREST SITE AND AT A COASTAL SITE IN MACE HEAD,  J. Aerosol Sct. Vol. 3 I, Suppl. 1, pp S602- S603,2000

Abstract


Number size distribution measurements in the submicron, and especially in the ultrafine size range, were carried out in the intensive field campaigns in connection with two EU projects BIOFOR (ENV4 - CT97 - 0405) and PARFORCE (ENV4-CT97- 0526). The studies in both projects were concentrated in finding the fundamental physico-chemical processes to cause the ambient particle formation phenomena that are observed at two continuous measurement sites (Makela et al, 1997, O'Dowd et al, 1999). The two sites in question are boreal forest site of Hyyti~il~i (SMEAR II) in '
Southern Finland and coastal site of Mace Head on the West coast of Ireland.

Transatlantic transport of pollution and its effects on surface ozone in Europe and North Ameri Transatlantic transport of pollution and its effects on surface ozone in Europe and North Ameri

Date added: 08/07/2002
Date modified: 07/23/2009
Filesize: 7.5 MB
Li, Q., et al. (2002), Transatlantic transport of pollution and its effects on surface ozone in Europe and North America, J. Geophys. Res., 107(D13), 4166, doi:10.1029/2001JD001422.

Abstract


We examine the transatlantic transport of anthropogenic ozone and its impact on surface ozone in Europe and North America by using a 5-year (1993–1997) simulation with the GEOS-CHEM global three-dimensional model of tropospheric chemistry. Long-term time series of ozone and CO at Mace Head (Ireland) and Sable Island (Canada) are used to evaluate transatlantic transport in the model. North American anthropogenic emissions contribute on average 5 ppbv to surface ozone at Mace Head, and up to 10–20 ppbv during transatlantic transport events, which are forerunners of broader events in Europe. These events are associated with low-level westerly flow driven by an intense Icelandic low between Iceland and the British Isles. North American influence on ozone at Mace Head is strongly correlated with the North Atlantic Oscillation (NAO), implying that the NAO index can be used to forecast transatlantic transport of North American pollution to Europe. European anthropogenic emissions contribute on average less than 2 ppbv to surface ozone at Sable Island but up to 5–10 ppbv during transatlantic transport events. These events are associated with low-level easterly flow established by anomalous low pressure at 45°N over the North Atlantic. North American anthropogenic emissions enhance surface ozone in continental Europe by 2–4 ppbv on average in summer and by 5–10 ppbv during transatlantic transport events; transport in the boundary layer and subsidence from the free troposphere are both important mechanisms. We find in the model that 20% of the violations of the European Council ozone standard (55 ppbv, 8-hour average) in the summer of 1997 over Europe would not have occurred in the absence of anthropogenic emissions from North America. North American influence on surface ozone in Europe is particularly strong at the thresholds used for the European standards (55–65 ppbv).

Tropospheric concentrations of the chlorinated solvents, tetrachloroethene and trichloroethene, Tropospheric concentrations of the chlorinated solvents, tetrachloroethene and trichloroethene,

Date added: 08/07/2001
Date modified: 07/23/2009
Filesize: 573.98 kB

Dimmer, C.H., McCulloch, A., Simmonds, P.G., Nickless, G. Bassford, M.R. and Smythe-Wright, D. Tropospheric concentrations of the chlorinated solvents, tetrachloroethene, and trichloroethene, measured in the remote Northern Hemisphere, Atmospheric Environment, 35, 2001, 1171-1182.


Abstract


A fully automated twin ECD gas chromatograph system with sample enriching adsorption-desorption primary stage was deployed on two field campaigns - Ny-Ålesund, Svalbard, Arctic Norway (July-September 1997), and the RRS Discovery CHAOS cruise of the northeast Atlantic (April-May 1998). Concentrations of an extensive set of halocarbons were detected at hourly intervals at pptv levels. We present the results obtained for the chlorinated solvents, tetrachloroethene (PCE) and trichloroethene (TCE). Average baseline PCE and TCE concentrations of 1.77 and 0.12 pptv, respectively, were recorded in Ny-Ålesund. During pollution incidences, concentrations rose to 5.61 (PCE) and 3.18 pptv (TCE). The cruise data showed average concentrations ranging from 4.26 (PCE) and 1.66 pptv (TCE) for air masses originating over the North Atlantic and Arctic open oceans, to maxima of 15.59 (PCE) and 17.51 pptv (TCE) for polluted air masses from Northern Europe. The data sets emphasise the difficulties in defining remote sites for background tropospheric halocarbon measurements, as Ny-Ålesund research station proved to be a source of tetrachloroethene. The data also suggest possible oceanic emissions of trichloroethene in the sub-tropical ocean.

 

Volatility of Elemental Carbon Volatility of Elemental Carbon

Date added: 07/31/1994
Date modified: 07/13/2009
Filesize: 423.53 kB
Jennings, S.G., O'Dowd, C.D., Cooke, W.F., Sheridan, P.J. and Cachier, (1994). - Volatility of elemental carbon. Geophys. Res. Letts., 21, 1719 - 1722.

Abstract


A volatility technique whereby aerosol particles are heated to the relatively high temperature of 860 °C is used to infer the presence of elemental carbon in polluted air masses in the vicinity of the west coast of Ireland. The volume of elemental carbon for submicrometre sized particles contained in the aerosol is estimated from the fall off in number concentration at a critical onset temperature of about 730 −735 °C, as also obtained for laboratory carbon ink aerosol. The technique permits determination of the elemental carbon volume percentage of the total fine aerosol volume, and an estimation of the abundance of elemental carbon contained within the black carbon fraction of the atmospheric aerosol. Supplementary black carbon mass concentration measurements were obtained using a thermal method and an aethalometer absorption method. The work suggests that elemental carbon can be identified using the volatility technique and that it can yield size-segregated information on the fraction of elemental carbon in atmospheric aerosol.

Wet properties affecting Atmospheric Aerosols Wet properties affecting Atmospheric Aerosols

Date added: 08/01/1998
Date modified: 07/10/2009
Filesize: 6.2 MB
Jennings. S.G, Wet properties affecting Atmospheric Aerosols, 1998, Atmospheric Particles, Pg 476-502, Wiley & Sons

Abstract

 

The origin of atmospheric particles can be either anthropogenic (man-made) or natural. Primary particles are those which are emitted into the atmosphere as particles such as black carbon and organic particles in smoke plumes, soil dust particles, sea spray and volcanic particles, etc Secondary particles are formed from gas-to-particle coversion processes in the atmosphere- such as sulphates(from SO2), Nitreates (from (NOx) and secondary organics (from gaseous hydro-carbons)

Time series analysis of long-term data sets of atmospheric mercury concentrations Time series analysis of long-term data sets of atmospheric mercury concentrations

Date added: 08/05/2004
Date modified: 07/23/2009
Filesize: 431.28 kB

Temme C, Ebinghaus R, Einax JW, Steffen A, Schroeder WH. Time series analysis of long-term data sets of atmospheric mercury concentrations. Anal Bioanal Chem. 2004; 380:49350


Abstract


Different aspects and techniques of time series analysis were used to investigate long-term data sets of atmospheric mercury in the Northern Hemisphere. Two perennial time series from different latitudes with different seasonal behaviour were chosen: first, Mace Head on the west coast of Ireland (53°20′N, 9°54′W), representing Northern Hemispherical background conditions in Europe with no indications for so-called atmospheric mercury depletion events (AMDEs); and second, Alert, Canada (82°28′N, 62°30′W), showing strong AMDEs during Arctic springtime. Possible trends were extracted and forecasts were performed by using seasonal decomposition procedures, autoregressive integrated moving average (ARIMA) methods and exponential smoothing (ES) techniques. The application of time series analysis to environmental data is shown in respect of atmospheric long-term data sets, and selected advantages are discussed. Both time series have not shown any statistically significant temporal trend in the gaseous elemental mercury (GEM) concentrations since 1995, representing low Northern Hemispherical background concentrations of 1.72±0.09 ng m−3 (Mace Head) and 1.55±0.18 ng m−3 (Alert), respectively. The annual forecasts for the GEM concentrations in 2001 at Alert by two different techniques were in good agreement with the measured concentrations for this year.

 

The North Atlantic Oscillation controls air Pollution transport to the Arctic The North Atlantic Oscillation controls air Pollution transport to the Arctic

Date added: 08/26/2003
Date modified: 08/05/2009
Filesize: 753.2 kB

Eckhardt, S., Stohl, A., Beirle, S., Spichtinger, N., James, P., Forster, C., Junker, C., Wagner, T., Platt, U., and Jennings, S. G.: The North Atlantic Oscillation controls air pollution transport to the Arctic, Atmos. Chem. Phys., 3, 1769-1778, 2003.


Abstract


This paper studies the interannual variability of pollution pathways from northern hemisphere (NH) continents into the Arctic. Using a 15-year model simulation of the dispersion of passive tracers representative of anthropogenic emissions from NH continents, we show that the North Atlantic Oscillation (NAO) exerts a strong control on the pollution transport into the Arctic, particularly in winter and spring. For tracer lifetimes of 5 (30) days, surface concentrations in the Arctic winter are enhanced by about 70% (30%) during high phases of the NAO (in the following referred to as NAO+) compared to its low phases (NAO-). This is mainly due to great differences in the pathways of European pollution during NAO+ and NAO- phases, respectively, but reinforced by North American pollution, which is also enhanced in the Arctic during NAO+ phases. In contrast, Asian pollution in the Arctic does not significantly depend on the NAO phase. The model results are confirmed using remotely-sensed NO2 vertical atmospheric columns obtained from seven years of satellite measurements, which show enhanced northward NO2 transport and reduced NO2 outflow into the North Atlantic from Central Europe during NAO+ phases. Surface measurements of carbon monoxide (CO) and black carbon at high-latitude stations further corroborate the overall picture of enhanced Arctic pollution levels during NAO+ phases

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