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Journal Publications

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

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Documents

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The effect of physical and chemical aerosol properties on warm cloud droplet activation The effect of physical and chemical aerosol properties on warm cloud droplet activation

Date added: 08/01/2005
Date modified: 07/23/2009
Filesize: 1.02 MB

McFiggans, G., P. Artaxo, U. Baltensperger, H. Coe, M. C. Facchini, G. Feingold, S. Fuzzi, M. Gysel,, A. Laaksonen, U. Lohmann, T. F. Mentel, D. M. Murphy, C. D. O'Dowd, J. R. Snider and E. Weingartner, The effect of physical and chemical aerosol properties on warm cloud droplet activation, Atmospheric Chemistry and Physics Discussions, Vol. 5, pp 8507-8647, 2005.


Abstract


The effects of atmospheric aerosol on climate forcing may be very substantial but are quantified poorly at present; in particular, the effects of aerosols on cloud radiative properties, or the "indirect effects" are credited with the greatest range of uncertainty amongst the known causes of radiative forcing. This manuscript explores the effects that the composition and properties of atmospheric aerosol can have on the activation of droplets in warm clouds, so potentially influencing the magnitude of the indirect effect. The effects of size, composition, mixing state and various derived properties are assessed and a range of these properties provided by atmospheric measurements in a variety of locations is briefly reviewed. The suitability of a range of process-level descriptions to capture these aerosol effects is investigated by assessment of their sensitivities to uncertainties in aerosol properties and by their performance in closure studies. The treatment of these effects within global models is reviewed and suggestions for future investigations are made.

The efficency with which drizzle and precipitation sized drops collide with aerosol particles The efficency with which drizzle and precipitation sized drops collide with aerosol particles

Date added: 07/31/1991
Date modified: 07/10/2009
Filesize: 3.81 MB

McGann, B.T., and Jennings, S.G. (1991) - The efficiency with which drizzle and precipitation sized drops collide with aerosol particles. Atmos. Environ., 25A, 791 - 800.


Abstract


Vlaues of collision efficency and scavenging rates for drops interacting with aerosol particles are presented using more accurate flow fields than previous work and for a much greater number of drops than hitherto obtained. All calculations are performed at an Ambient temperature of 10C andatmospheric pressure of 900mb. Computations of collision efficency are performed for a drop radius range from 50 to 500 micrometre (um), for particle radius from 0.005 to 10um, for relative humidity values of 50,75,95 and 100% and for particle density of 1,1.5,2.0 and 2.5 x 10^3 kgm^-3. In addition the collision effiicency was also calculated fro elctric charges on the drop and particle and for an electric field, representive of typical thundercloud values. Combined use is made of a rigorous trajectory model together with a flux model and comparision is made between them in the overlap size region . Precipitation scavenging rates and the percentage of aerosol particles scavenged by precipitation drops described by Marshall-Palmer size distribution is also calculated.

The Electrical conductivity within water droplet clouds The Electrical conductivity within water droplet clouds

Date added: 08/01/1975
Date modified: 07/22/2009
Filesize: 1.58 MB
Jennings,S.G.   (1975)- The electrical conductivity within water droplet clouds. Proc.  4th Conf. Static Electrification. Inst. Phys. Conf. Series, No 27,  34-43.

Abstract

 

Studies have been made of the reduction of small positive ion concentration, produced by a weak americium alpha source in the presence of small water droplet clouds. The droplet clouds which possessed values of clou-water content ranging from about 1.0 up to 6 g m-3 and mean radius from 0.75 up to approximately 2.25 μm were produced by a steam condenser method which yielded relatively stable clouds.

The Evolution of Condensation Nucleus Counters The Evolution of Condensation Nucleus Counters

Date added: 08/07/2001
Date modified: 07/07/2009
Filesize: 7.48 MB
O'Connor Tom,  The Evolution of Condensation Nucleus Counters , The Aerosol Society Newsletter, pg 5-8, March 2001

Abstract

 


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 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.

The First Condensation Nucleus Conference And Research In Dublin The First Condensation Nucleus Conference And Research In Dublin

Date added: 08/07/1985
Date modified: 08/18/2008
Filesize: 711.16 kB
 O Connor, The First Condensation Nucleus Conference And Research In Dublin, J Rech. Atmos., 19 (1985) 

The Hohenpeissenberg aerosol formation experiment (HAFEX): a long-term study including size-resolved The Hohenpeissenberg aerosol formation experiment (HAFEX): a long-term study including size-resolved

Date added: 07/27/2003
Date modified: 07/27/2009
Filesize: 514.79 kB

Birmili W, Berresheim H, Plass-Dulmer C, Elste T, Gilge S, Wiedensohler A, Uhrner U, 2003. The Hohenpeissenberg aerosol formation experiment (HAFEX): a longterm study including size-resolved aerosol, H2SO4, OH, and monoterpenes measurements. Atmos. Chem. Phys. 3: 361–376.


Abstract

 

Ambient aerosol size distributions (> 3 nm) and OH, H2SO4, and terpene concentrations were measured from April 1998 to August 2000 at a rural continental site in southern Germany. New particle formation (NPF) events were detected on 18% of all days, typically during midday hours under sunny and dry conditions. The number of newly formed particles correlated significantly with solar irradiance and ambient levels of H2SO4. A pronounced anticorrelatation of NPF events with the pre-existing particle surface
area was identified in the cold season, often associated with the advection of dry and relatively clean air masses from southerly directions (Alps). Estimates of the particle formation rate based on observations were around 1 cm−3 s−1, being in agreement with the predictions of ternary homogeneous H2SO4-NH3-H2O nucleation within a few orders of magnitude. The experimentally determined nucleation mode particle growth rates were on average 2.6 nm h−1, with a fraction of 0.7 nm h−1 being attributed to the cocondensation of H2SO4-H2O-NH3. The magnitude of nucleation mode particle growth was neither significantly correlated
to H2SO4, nor to the observed particle formation rate. Turn-over rate calculations of measured monoterpenes and aromatic hydrocarbons suggest that especially the oxidation products of monoterpenes have the capacity to contribute to the growth of nucleation mode particles. Although a large number of precursor gases, aerosol and meteorological parameters were measured, the ultimate key factors controlling the occurence of NPF events could not be identified.

The Impact of Ship-Produced Aerosols on the Microstructure and Albedo of Warm The Impact of Ship-Produced Aerosols on the Microstructure and Albedo of Warm

Date added: 08/06/2000
Date modified: 07/08/2009
Filesize: 176.35 kB

Durkee, P. and co authors, 2000: The impact of ship-produced aerosols on the microstructure and albedo of warm marine stratocumulus clouds: A test of MAST hypotheses 1i and 1ii. J. Atmos. Sci., 57, 2554-2569.


Abstract


Anomalously high reflectivity tracks in stratus and stratocumulus sheets associated with ships (known as ship tracks) are commonly seen in visible and near-infrared satellite imagery. Until now there have been only a limited number of in situ measurements made in ship tracks. The Monterey Area Ship Track (MAST) experiment, which was conducted off the coast of California in June 1994, provided a substantial dataset on ship emissions and their effects on boundary layer clouds. Several platforms, including the University of Washington C-131A aircraft, the Meteorological Research Flight C-130 aircraft, the National Aeronautics and Space Administration ER-2 aircraft, the Naval Research Laboratory airship, the Research Vessel Glorita, and dedicated U.S. Navy ships, participated in MAST in order to study processes governing the formation and maintenance of ship tracks. This paper tests the hypotheses that the cloud microphysical changes that produce ship tracks are due to (a) particulate emission from the ship's stack and/or (b) sea-salt particles from the ship's wake. It was found that ships powered by diesel propulsion units that emitted high concentrations of aerosols in the accumulation mode produced ship tracks. Ships that produced few particles (such as nuclear ships), or ships that produced high concentrations of particles but at sizes too small to be activated as cloud drops in typical stratocumulus (such as gas turbine and some steam-powered ships), did not produce ship tracks. Statistics and case studies, combined with model simulations, show that provided a cloud layer is susceptible to an aerosol perturbation, and the atmospheric stability enables aerosol to be mixed throughout the boundary layer, the direct emissions of cloud condensation nuclei from the stack of a diesel-powered ship is the most likely, if not the only, cause of the formation of ship tracks. There was no evidence that salt particles from ship wakes cause ship tracks.

 

The impact of the Montreal Protocol on halocarbon concentrations in northern hemisphere baselin The impact of the Montreal Protocol on halocarbon concentrations in northern hemisphere baselin

Date added: 08/07/1998
Date modified: 07/23/2009
Filesize: 550.28 kB

Derwent, RG, Simmonds, PG, O'Doherty, S, et al , The impact of the Montreal Protocol on halocarbon concentrations in northern hemisphere baseline and European air masses at Mace Head, Ireland over a ten year period from 1987-1996, ATMOS ENVIRON, 1998, Vol: 32, Pages: 3689 - 3702,


Abstract


The international concern following the discovery of Antarctic stratospheric ozone depletion has prompted unprecedented international action by governments to control the production, sales and usage of a range of ozone-depleting chemicals. These international treaty obligations include the Montreal Protocol and its London and Copenhagen Amendments. They address, amongst many halocarbon species, the chlorofluorocarbons: CFC-11, -12 and -113 and the chlorocarbons: carbon tetrachloride and methyl chloroform. These chemicals have been routinely monitored at the remote, baseline monitoring station at Mace Head on the Atlantic Ocean coast of Ireland as part of the GAGE/AGAGE programme. The available monitoring data for the period 1987-1996 are presented here with a view to confirming the extent of compliance with the above Protocols on a global and European basis. Daily wind direction sectors provided by EMEP are used to sort the halocarbon data into northern hemisphere baseline air and European polluted air masses and trends have been determined for each wind direction sector. Evidence of the European phase-out of halocarbon usage is clearly apparent in the sorted halocarbon concentrations. A simple climatological long-range transport and a sophisticated Lagrangian air parcel dispersion model have been used to interpret the Mace Head halocarbon measurements and to derive estimates of European emission source strengths for each year. These emission source strengths confirm that the phase-out of halocarbon manufacture and sales is being followed in Europe.

 

The influence of evaporation and drop-interaction on a rainshaft The influence of evaporation and drop-interaction on a rainshaft

Date added: 07/30/1973
Date modified: 07/08/2009
Filesize: 1.13 MB

Brazier-Smith, P.R., and Jennings, S.G., and Latham, J. (1973)- The influence of evaporation and drop-interaction on a rainshaft. Quart. J. Roy. Met. Soc., 99, 704-722.


Abstract


Calculations have been made of the variations with fall-depth z of the liquid water content, L, rainfall rate, p, radar reflectivity, Z, drop concentration, NT, and raindrop size distribution n(r), within a steady-state rainshaft as a result of the evaporation and interaction of the drops. The interactions were described by a generalized stochastic equation which takes account, as described by Brazier-Smith, Jennings and Latham (1973), of the variation of coalescence efficiency s with drop radii R, r and the fact that satellite drops are produced when drops separate after collision. The relative humidity is assumed to fall linearly from 100 per cent at cloud base (z = 0, T = 8°C) with a gradient 8. The lapse rate within the rainshaft was taken to be 8°C krn- and the initial size distribution was generally given by the Marshall-Palmer equation. Calculations were made for 3 different situations in order to isolate the physical processes which most affect the rainfall:
(l), evaporation without interaction; (2) interaction without evaporation; (3) both interaction and evaporation. The calculations for Case (1) indicate that the numbers of drops in all size classes are diminished with increasing Z, with a preferential reduction at the small-radius end of the spectrum. In Case (2) the interactions of the raindrops introduce considerable detail into n(r), with bimodal curves associated with satellite drop production, the highly efficient consumption of small drops by larger ones and the variations of E and fall-velocity V with drop-radius r.
The main feature of the calculations for Case (3) is the rBle of coalescence in preserving within the spectrum a considerable amount of liquid water that would otherwise be lost by evaporation. For example, whereas the rainwater content at z = 1.5 km for 8 = 20 per cent km- and Lo = 1.0 gm m- is 0.28 gm m-3 if interactions are absent, their presence elevates L to 0.57 gm m-3 at this level. This retention effect is significant for all values considered of 8, L, p, and the initial slope of the raindrop size distribution (varied from half to twice that of the Marshall-Palmerequation). It is alsofound that the structure introduced into the size distributions as a result of interactions is partially smoothed out by evaporation, which replaces a substantial proportion of the smallest drops consumed by coalescence.

The influence of evaporation and drop-interaction on a rainshaft : Comments and Notes The influence of evaporation and drop-interaction on a rainshaft : Comments and Notes

Date added: 09/14/1974
Date modified: 07/08/2009
Filesize: 326.53 kB

Brazier-Smith, P.R., and Jennings, S.G., and Latham, J. (1974)- The influence of evaporation and drop-interaction on a rainshaft Reply. Quart. J. Roy. Met. Soc., 99, 704-722.


Abstract


Calculations have been made of the variations with fall-depth z of the liquid water content, L, rainfall rate, p, radar reflectivity, Z, drop concentration, NT, and raindrop size distribution n(r), within a steady-state rainshaft as a result of the evaporation and interaction of the drops. The interactions were described by a generalized stochastic equation which takes account, as described by Brazier-Smith, Jennings and Latham (1973), of the variation of coalescence efficiency s with drop radii R, r and the fact that satellite drops are produced when drops separate after collision. The relative humidity is assumed to fall linearly from 100 per cent at cloud base (z = 0, T = 8°C) with a gradient 8. The lapse rate within the rainshaft was taken to be 8°C krn- and the initial size distribution was generally given by the Marshall-Palmer equation. Calculations were made for 3 different situations in order to isolate the physical processes which most affect the rainfall:
(l), evaporation without interaction; (2) interaction without evaporation; (3) both interaction and evaporation. The calculations for Case (1) indicate that the numbers of drops in all size classes are diminished with increasing Z, with a preferential reduction at the small-radius end of the spectrum. In Case (2) the interactions of the raindrops introduce considerable detail into n(r), with bimodal curves associated with satellite drop production, the highly efficient consumption of small drops by larger ones and the variations of E and fall-velocity V with drop-radius r.
The main feature of the calculations for Case (3) is the rBle of coalescence in preserving within the spectrum a considerable amount of liquid water that would otherwise be lost by evaporation. For example, whereas the rainwater content at z = 1.5 km for 8 = 20 per cent km- and Lo = 1.0 gm m- is 0.28 gm m-3 if interactions are absent, their presence elevates L to 0.57 gm m-3 at this level. This retention effect is significant for all values considered of 8, L, p, and the initial slope of the raindrop size distribution (varied from half to twice that of the Marshall-Palmerequation). It is alsofound that the structure introduced into the size distributions as a result of interactions is partially smoothed out by evaporation, which replaces a substantial proportion of the smallest drops consumed by coalescence.

The influence of the complex index of refraction on the volume extinction, scattering and absorption The influence of the complex index of refraction on the volume extinction, scattering and absorption

Date added: 08/01/1977
Date modified: 07/08/2009
Filesize: 496.46 kB
The influence of the complex index of refraction on the volume extinction, scattering and absorption coefficient of particle size distributions. Topical Optical Society of America Meeting on Optical Propagation Through Turbulence, Rain and Fog, Boulder, Colorado, U.S.A., pp. WD  7-1  to  7-4.

Abstract

 


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.

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%.

The modeling of tropospheric methane How well can point measurements be reproduced by a global The modeling of tropospheric methane How well can point measurements be reproduced by a global

Date added: 08/06/2000
Date modified: 07/27/2009
Filesize: 1.69 MB

Houweling, S., F. Dentener, J. Lelieveld, B. Walter, and E. Dlugokencky, 2000: The modeling of tropospheric methane: How well can point measurements be reproduced by a global model? J. Geophys. Res., 105, 8981-9002, doi:10.1029/1999JD901149.


Abstract

 

Global model simulations of tropospheric methane are presented, using state of the art representations of its terrestrial sources. Parameters critical for its tropospheric sink and transport have been evaluated using CH3CCl3 and SF6. We assess how well available methane measurements can be reproduced by the model, and how model and measurements can most efficiently be compared. Using European Centre for Medium-Range Weather Forecasts reanalyzed meteorological fields, direct comparisons between model results and flask or in situ measurements are presented, as opposed to comparing multiannual averaged seasonal cycles and trends as was done in previous studies. When comparing monthly means derived from weekly flask sampling and the model, the agreement at stations as Bermuda East and Mace Head is improved if, instead of sampling the model at each model time step, samples are taken at the same times as the measurements were taken. A method is presented to estimate the potential influence of subgrid variability using a marked tracer that is emitted in the vicinity of observational stations only. From the contribution of this tracer to the computed methane concentration at a particular station, the potential contribution of subgrid sources can be estimated. Radon 222 is used to select baseline conditions in the model to improve the comparability of model and measurements when a clean air sector is selected for sampling. Comparisons of model results and measurements, screened for local influences and artifacts of wind sector selection, indicate that the model has in particular difficulty reproducing seasonal cycles at higher latitude stations of the Northern Hemisphere. Sensitivity simulations show that the simulated annual variation at these stations is sensitive to the parameterization of wetland emissions. Also at the South China Sea, model simulations point to errors in the representation of methane sources. Marked tracer simulations indicate that this is most likely related to emissions from natural wetlands and rice paddies, in line with recent inverse modeling and up-scaling estimates.

 

THE NAMBLEX FIELD Campaign 2002 THE NAMBLEX FIELD Campaign 2002

Date added: 08/07/2003
Date modified: 08/07/2008
Filesize: 5.06 kB
Heard, D.E.The NAMBLEX field campaign 2002 [EGU04-A-03242].

The nitrate radical in the remote marine boundary layer The nitrate radical in the remote marine boundary layer

Date added: 08/06/2000
Date modified: 07/23/2009
Filesize: 1.19 MB

Allan B. J., G. McFiggans, J. M. C. Plane, H. Coe and G. G. McFadyen The Nitrate Radical in the Remote Marine Boundary Layer. J. Geophys. Res., 24191-24204, 2000.


Abstract


The technique of differential optical absorption spectroscopy has been used to determine the nitrate radical (NO3) concentration in the remote marine boundary layer. The instrument was deployed in campaigns at Mace Head on the west coast of Ireland and on the north coast of Tenerife. A comprehensive set of NO3 measurements under a wide variety of conditions was obtained. For instance, nighttime NO3 levels at Mace Head ranged from 1 to 5 ppt in the clean marine atmosphere and from 1 to 40 ppt in semipolluted continental air masses. The nightly averaged NO3 lifetime varied from less than 2 min to 4 hours. At Tenerife, where there was less variability in conditions, nighttime NO3 ranged from 1 to 20 ppt, with nightly averaged lifetimes between 4 and 34 min. A photochemical box model, fully constrained by measurements of species that control the formation and removal of NO3, was then employed to determine the major loss mechanisms of the radical. This shows that NO3 in the clean marine air masses is very sensitive to small increases in the concentrations of dimethyl sulphide (DMS) and nonmethane hydrocarbons and that the radical is rarely in chemical steady state. At Tenerife, 80 - 90% of NO3 was removed by reaction with DMS. However, in continental air masses with little marine influence, indirect losses of NO3 via dinitrogen pentoxide (N2O5) usually dominate. It appears that in much of the North Atlantic, NO3 is a more efficient sink for DMS compared to the hydroxyl radical (OH) during the day.

 

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.

 

The North Atlantic Marine Boundary Layer Experiment (NAMBLEX). Overview of the campaign held at Mace Head, Ireland, in summer 2002 The North Atlantic Marine Boundary Layer Experiment (NAMBLEX). Overview of the campaign held at Mace Head, Ireland, in summer 2002

Date added: 08/01/2005
Date modified: 07/23/2009
Filesize: 9.65 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.

The North Atlantic Marine Boundary Layer Experiment (NAMBLEX). Overview of the campaign held at Mace Head, Ireland, in summer 2002 The North Atlantic Marine Boundary Layer Experiment (NAMBLEX). Overview of the campaign held at Mace Head, Ireland, in summer 2002

Date added: 08/01/2005
Date modified: 07/23/2009
Filesize: 9.65 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.

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

The North Atlantic Oscillation controls air Pollution transport to the Artic Atmos Chem Phys Comments The North Atlantic Oscillation controls air Pollution transport to the Artic Atmos Chem Phys Comments

Date added: 08/26/2003
Date modified: 08/05/2009
Filesize: 944.42 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. Discuss., 3, 3222-3240, 2003


Abstract


This paper studies the interannual variability of pollution pathways from northern hemisphere (NH) continents into the Arctic. Using a 1-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.

The origin of high particulate concentrations over the United Kingdom, March 2000 The origin of high particulate concentrations over the United Kingdom, March 2000

Date added: 08/07/2002
Date modified: 07/23/2009
Filesize: 1.45 MB

Ryall, D.B., R.G Derwent, A.J. Manning, A.L. Redington, J. Corden, W. Millington, P.G. Simmonds, S. O’Doherty, N. Carslaw and G.W. Fuller (2002), The origin of high particulate concentrations over the United Kingdom, March 2000, Atmos. Environ. 36, 1363-1378.


Abstract


An episode of exceptionally high PM10 and PM2.5 levels was observed during the night of the 2-3 March 2000 throughout England and Wales. The weather was characterised by strong westerly winds and widespread rainfall associated with a low pressure system to the north of Scotland, conditions usually associated with relatively clean, unpolluted air. Possible sources included volcanic ash from an eruption on 26 February 2000 in Iceland, or dust from large sandstorms over the Sahara. A combination of atmospheric transport modelling using the Lagrangian dispersion model NAME, an analyses of satellite imagery and observational data from Mace Head has shown that the most likely origin of the episode was long range transport of dust from the Sahara region of North Africa. Further modelling studies have revealed a number of previously unidentified dust episodes, and indicate that transport of dust from the Sahara can occur several times a year. Dust episodes are of interest for a number of reasons, particulate levels can be elevated over a wide area and in some instances can significantly exceeded current air quality standards. If a natural source is identified over which there can be no control, there are implications for the setting of air quality standards.

 

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.

 

The Photo-Electric Counter The Photo-Electric Counter

Date added: 08/31/1972
Date modified: 08/31/2008
Filesize: 3.79 MB

The Photoelectric Nucleus Counter as Hygrometer The Photoelectric Nucleus Counter as Hygrometer

Date added: 08/07/1955
Date modified: 07/22/2009
Filesize: 895.22 kB
PJ Nolan & TC O Connor, The Photoelectric Nucleus Counter as Hygrometer, Geofisica Pura E Applicata - Milano Vol. 31 pp 32-36 (1955)

Abstract

 

Hygrometric measurements on room air were made with a Nolan-Pollak nucleus counter from which the lining of blotting paper had been removed. The dew point can be determined from the critical overpressure for condensation on nuclei. Satisfactory agreement with the values given by a ventilated wet and dry blub hygrometer was obtained. The correction required is small since condensation occurs on ordinary atmospheric nuclei when the temperature is brought to about 0.3C below the dew point.

The production of Condensation Nuclei By Heated Wires The production of Condensation Nuclei By Heated Wires

Date added: 08/07/1966
Date modified: 07/23/2009
Filesize: 4.73 MB
T.C. O'connor, AF Roddy, The production of Condensation Nuclei By Heated Wires, Journal de Recherches Atmospheriques Vol II 2e nos 2-3 pp 239-44
Abstract

 

Investigations of the condensation nuclei produced by heated wires, particularly platinum, are described. There is a 'transient' type due to surface containation and a 'permanent' type which contain the material of the wire and are about 4 x 10-7 cm in diameter. Nitrogen dioxide is also produced by the wires in the gaseous and not in the particulate form.

The regional aerosol-climate model REMO-HAM The regional aerosol-climate model REMO-HAM

Date added: 03/22/2013
Date modified: 03/22/2013
Filesize: 1.96 MB

Pietikäinen, JP, D O'Donnell, C Teichmann, U Karstens, S Pfeifer, J Kazil, R Podzun, S Fiedler, H Kokkola, W Birmili, C O'Dowd, U Baltensperger, E Weingartner, R Gehrig, G Spindler, M Kulmala, J Feichter, D Jacob, A Laaksonen, The regional aerosol-climate model REMO-HAM, Geosci. Model Dev., 5, 1323-1339, doi: 10.5194, 2012.


Abstract. REMO-HAM is a new regional aerosol-climate model. It is based on the REMO regional climate model and includes most of the major aerosol processes. The structure for aerosol is similar to the global aerosol-climate model ECHAM5-HAM, for example the aerosol module HAM is coupled with a two-moment stratiform cloud scheme. On the other hand, REMO-HAM does not include an online coupled aerosol-radiation nor a secondary organic aerosol module. In this work, we evaluate the model and compare the results against ECHAM5-HAM and measurements. Four different measurement sites were chosen for the comparison of total number concentrations, size distributions and gas phase sulphur dioxide concentrations: Hyyti¨al¨a in Finland, Melpitz in Germany, Mace Head in Ireland and Jungfraujoch in Switzerland. REMO-HAM is run with two different resolutions: 50×50 km2and 10×10 km2. Based on our simulations, REMO-HAM is in reasonable agreement with the measured values. The differences in the total number concentrations between REMO-HAM and ECHAM5-HAM can be mainly explained by the difference in the nucleation mode. Since we did not use activation nor kinetic nucleation for the boundary layer, the total number concentrations are somewhat underestimated. From the meteorological point of view, REMO-HAM represents the precipitation fields and 2m temperature profile very well compared to measurement. Overall, we show that REMO-HAM is a functional aerosol-climate model, which will be used in further studies.

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

 

The relative Importance of sea-salt and nss-sulphate aerosol to the marine CCN Population The relative Importance of sea-salt and nss-sulphate aerosol to the marine CCN Population

Date added: 08/06/1999
Date modified: 07/08/2009
Filesize: 9.2 MB

O'Dowd, C.D., J. Lowe, M.H. Smith and A.D. Kaye, The relative importance of sea-salt and nss-sulphate aerosol to the marine CCN population: An improved multi-component aerosol-droplet parameterisation. Q. J. Roy. Met. Soc., 125, 1295-1313. 1999


Abstract


The effect of sub-cloud aerosol on cloud droplet concentration was explored over the north Atlantic and east Pacific under a variety of low and high wind speed conditions. A relationship of the form of D = 197(1-exp(-6.13 × 10-3 * A)] was found to fit best the relationship between cloud droplet concentration (D; cm-3) and sub-cloud aerosol concentration (A; cm-3) under low to moderate wind conditions. A few noticeable deviations from this relationship were observed which occurred under moderate to high wind speed condition. Under these high wind conditions, sea-salt aerosol provided the primary source of cloud nuclei due to their higher nucleation activity and larger sizes, even under sulphate-rich conditions. Simple model simulations reveal that the activation of sea-salt nuclei suppresses the peak supersaturation reached in cloud, and thus inhibits the activation of smaller sulphate nuclei into cloud droplets. A multi-component aerosol-droplet parametrization for use in general circulation models is developed to allow prediction of cloud droplet concentration as a function of sea-salt and non-sea-salt-(nss) sulphate nuclei. The effects of enhancing an existing nss-sulphate cloud condensation nuclei (CCN) population with sea-salt nuclei are to reduce the number of cloud droplets activated under high (polluted) sulphate conditions and to increase the cloud droplet concentration under low (clean) sulphate conditions. The presence of sea-salt CCN reduces the influence of nss-sulphate CCN on cloud droplet concentrations, and thus is likely to reduce the predicted effect of nss-sulphate indirect radiative forcing.

 

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.

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 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.

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 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

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.

 

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.

 

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.

 

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.

 

Tracking electrically charged puff,....,by ground level electric field measurements Tracking electrically charged puff,....,by ground level electric field measurements

Date added: 07/31/1977
Date modified: 07/08/2009
Filesize: 1003.89 kB

Jennings, S.G., and Jones, C.D. (1977)- Tracking electrically charged puffs, as used in short range atmospheric diffusion investigations, by ground level electric field measurements. J. Electrostatics, 2, 367-373.


Abstract


The use of ionized air as a tracer in short range atmospheric diffusion investigations raises the possibility of cloud location using electric field measurements. In this short communication a simple analysis is developed which enables the trajectory of a charged cloud to be ascertained from electric field measurements at three points at ground level (assuming the charge is known). Alternatively, if the charge is not known, it is shown that five-position electric field measurements are needed to find both its position and magnitude.

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).

Transport of boreal forest fire emissions from Canada to Europe Transport of boreal forest fire emissions from Canada to Europe

Date added: 07/31/2001
Date modified: 07/23/2009
Filesize: 2.14 MB

Forster, C., Wandinger, U., Wotawa, G., James, P., Mattis, I., Althausen, D., Simmonds, P., O'Doherty, S., Jennings, S. Gerard., Kleefeld, Christoph, Schneider, Johannes, Trickl, Thomas, Kreipl, Stephan, Jager, Horst, Stohl, Anreas. (2001). Transport of boreal forest fire emissions from Canada to Europe. J. Geophys. Res., 106, 22,887 - 22,906.


Abstract


In August 1998, severe forest fires occurred in many parts of Canada, especially in the Northwest Territories. In the week from August 5 to 11, more than 1000 different fires burned >1 x 106 ha of boreal forest, the highest 1-week sum ever reported throughout the 1990s. In this study we can unambigously show for the first time that these fires caused pronounced large-scale haze layers above Europe and that they influenced concentrations of carbon monoxide and other trace gases at the surface station Mace Head in Ireland over a period of weeks. Transport took place across several thousands of kilometers. An example of such an event, in which a pronounced aerosol layer was observed at an altitude of 3-6 km over Germany during August 1998, is investigated in detail. Backward trajectories ending at the measured aerosol layer are calculated and shown to have their origin in the forest fire region. Simulations with a particle dispersion model reveal how a substantial amount of forest fire emissions was transported across the Atlantic. The resulting aerosol lamina over Europe is captured well by the model. In addition, the model demonstrates that the forest fire emissions polluted large regions over Europe during the second half of August 1998. Surface measurements at Mace Head are compared to the model results for an anthropogenic and a forest fire carbon monoxide tracer, respectively. While wet deposition removed considerable amounts of aerosol during its transport, forest fire carbon monoxide reached Europe in copious amounts. It is estimated that during August 1998, 32%, 10%, and 58% of the carbon monoxide enhancement over the background level at Mace Head were caused by European and North American anthropogenic emissions and forest fire emissions, respectively.

Transport-induced interannual variability of carbon monoxide determined using a chemistry and t Transport-induced interannual variability of carbon monoxide determined using a chemistry and t

Date added: 08/06/1996
Date modified: 07/23/2009
Filesize: 1.34 MB

Allen, D. J., P. Kasibhatla, A. M. Thompson, R. B. Rood, B. G. Doddridge, K. E. Pickering, R. D. Hudson, and S.-J. Lin (1996), Transport-induced interannual variability of carbon monoxide determined using a chemistry and transport model, J. Geophys. Res., 101(D22), 28,655–28,669.


Abstract


Transport-induced interannual variability of carbon monoxide (CO) is studied during 1989–1993 using the Goddard chemistry and transport model (GCTM) driven by assimilated data. Seasonal changes in the latitudinal distribution of CO near the surface and at 500 hPa are captured by the model. The annual cycle of CO is reasonably well simulated at sites of widely varying character. Day to day fluctuations in CO due to synoptic waves are reproduced accurately at remote North Atlantic locations. By fixing the location and magnitude of chemical sources and sinks, the importance of transport-induced variability is investigated at CO-monitoring sites. Transport-induced variability can explain 1991–1993 decreases in CO at Mace Head, Ireland, and St. David's Head, Bermuda, as well as 1991–1993 increases in CO at Key Biscayne, Florida. Transport-induced variability does not explain decreases in CO at southern hemisphere locations. The model calculation explains 80–90% of interannual variability in seasonal CO residuals at Mace Head, St. David's Head, and Key Biscayne and at least 50% of variability in detrended seasonal residuals at Ascension Island and Guam. Upper tropospheric interannual variability during October is less than 8% in the GCTM. Exceptions occur off the western coast of South America, where mixing ratios are sensitive to the strength of an upper tropospheric high, and just north of Madagascar, where concentrations are influenced by the strength of offshore flow from Africa.

 

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.

 

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.

 

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.

Uncertainties in the determination of global sub-micron marine organic matter emissions Uncertainties in the determination of global sub-micron marine organic matter emissions

Date added: 03/13/2013
Date modified: 03/13/2013
Filesize: 2.97 MB

Albert , M. F. M. A., M. Schaap, A.M.M. Manders, C. Scannell, C.D. ODowd and G. de Leeuw, Uncertainties in the determination of global sub-micron marine organic

matter emissions, Atmos. Environ., 57, 289-300, 2012 http://dx.doi.org/10.1016/j.atmosenv.2012.04.009


Abstract. Organic matter (OM) constitutes an important contribution to the composition of sub-micron sea-spray aerosol produced from biologically active waters. However, OM emission estimates vary by more than an order of magnitude. To estimate the uncertainties in the OM production estimates a sensitivity analysis has been performed in which various parameters have been varied. These include different sea-spray source functions, satellite-retrieved chlorophyll distributions, and a relationship correlating in situ organic mass measurements with satellite-retrieved chlorophyll data. The starting point was a baseline model from which the annual global emission of the water insoluble organic matter (WIOM) fraction in sea spray has been estimated to be 20.4 Tg. In this baseline the global WIOM emission is dominated by the contribution (80%) of the chlorophyll-poor regions (< 0.3 mg m-3). Significant deviations from this estimate are introduced by the choice of the sea-spray source function and the assumed background organic mass fraction, each of which leads to an uncertainty of at least a factor of 2. In particular the chlorophyll-poor regions which dominate the WIOM contribution are strongly affected by the choice of the organic mass fraction parameterisation. The way the chlorophyll data are handled, such as different gap filling approaches, causes deviations in the OM emission that are in the order of 10% and is therefore of less importance. The present research indicates that special attention should be given to the low chlorophyll areas in e.g. the tropics, since there the parameterisations are most uncertain and at the same time these regions dominate total WIOM emissions.

 

Uptake of Methanol to the north Atlantic Ocean Uptake of Methanol to the north Atlantic Ocean

Date added: 08/31/2004
Date modified: 07/27/2009
Filesize: 4.31 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

 

Methanol has an almost ubiquitous presence throughout the depth of the troposphere and has been identified as having an important effect on the atmospheric oxidative capacity, yet its global sources and sinks are not well known. Recent evaluations of the methanol budget conclude that a major uncertainty is whether the ocean is a net source or sink. During the North Atlantic Marine Boundary Layer Experiment (NAMBLEX) in July-August 2002, an anticorrelation between methanol concentrations and wind speed and a positive correlation between dimethylsulphide concentrations and wind speed was observed during a 3 day period of cyclonic activity in which the averaged surface wind speed changed substantially as a low pressure system evolved over the northeast Atlantic. The observations agreed well with theoretical predictions derived
assuming air-sea exchange according to the transfer velocity method, embedded in a zero dimensional box model. For the average wind speeds encountered, an irreversible ocean uptake rate of methanol of 8 x 10-7 s-1 was calculated, equivalent to a deposition rate of 0.08 cm s-1, in good agreement with deposition rates used in global models. However, owing to the dependence on wind speed, the uptake rates calculated
showed substantial range and the calculated contribution of ocean deposition to total destruction (uptake and OH destruction) varied from approximately 20% to 60%.

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%.

 

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