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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 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.

 

Variations of CN number concentrations with respect to meteorological conditions at Mace Head, Variations of CN number concentrations with respect to meteorological conditions at Mace Head,

Date added: 08/07/1998
Date modified: 07/23/2009
Filesize: 56.9 kB

Kleefeld C.; Geever M.; Jennings S.G.; Maring H.,Variations of CN number concentrations with respect to meteorological conditions at mace head, Ireland,Journal of Aerosol Science, Volume 29, Supplement 1, September 1998 , pp. 203-203(1)


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 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 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.

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.

Verification of a Linear Relation between IR Extinction Absorption and Liquid Water Content of Fogs Verification of a Linear Relation between IR Extinction Absorption and Liquid Water Content of Fogs

Date added: 08/01/1979
Date modified: 07/27/2009
Filesize: 761.93 kB

Pinnick, R. G.; Jennings, S. G.; Chýlek, Petr; Auvermann, H. J., Verification of a Linear Relation between IR Extinction, Absorption and Liquid Water Content of Fogs., Journal of Atmospheric Sciences, vol. 36, Issue 8, pp.1577-1586


Abstract


A linear relationship, independent of the form of the size-distribution, between extinction at wave-lengths around = 11 µm, absorption around = 3.8 and 9.5 µm, and liquid water content of atmospheric fogs has been verified using 341 droplet size distribution measurements made under a variety of meteorological conditions. The results suggest that integrated liquid water content along a path in fog can be determined from measurement of CO2 laser ( = 10.6 µm) transmission along the path, and that liquid water content at a particular point in fog can be inferred from in situ measurement of fog-droplet absorption with a deuterium fluoride laser ( = 3.8 µm) or a suitably tuned C02 laser ( = 9.5 µm) spectrophone.

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.

 

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.

Evaluation of mixing height retrievals from automatic profiling lidars and ceilometers in view of fu Evaluation of mixing height retrievals from automatic profiling lidars and ceilometers in view of fu

Date added: 08/12/2011
Date modified: 08/12/2011
Filesize: 1.59 MB

Haeffelin, M.,  F. Angelini, Y. Morille, G. Martucci, S. Frey, G. P. Gobbi, S. Lolli, C. D. O'Dowd, L. Sauvage, I. Xueref-Rémy, B. Wastine,  Evaluation of mixing height retrievals from automatic profiling lidars and ceilometers in view of future integrated networks in Europe, Bound. Lay. Met., DOI 10.1007/s10546-011-9643-z, 2011

 

The determination of the depth of daytime and nighttime mixing layers mustbe known very accurately to relate boundary-layer concentrations of gases or particles to upstream fluxes. The mixing-height is parametrized in numerical weather prediction models, so improving the determination of the mixing height will improve the quality of the estimated gas and particle budgets. Datasets of mixing-height diurnal cycles with high temporal and spatial resolutions are sought by various end users. Lidars and ceilometers provide vertical profiles of backscatter from aerosol particles. As aerosols are predominantly concentrated in the mixing layer, lidar backscatter profiles can be used to trace the depth of the mixing layer. Large numbers of automatic profiling lidars and ceilometers are deployed by meteorological services and other agencies in several European countries providing systems to monitor  the mixing height on temporal and spatial scales of unprecedented density. We investigate limitations and capabilities of existing mixing height retrieval algorithms by applying five different retrieval techniques to three different lidars and ceilometers deployed during two 1-month campaigns.We studied three important steps in the mixing height retrieval process, namely the lidar/ceilometer pre-processing to reach sufficient signal-to-noise ratio, gradient detection techniques to find the significant aerosol gradients, and finally quality control and layer attribution to identify the actual mixing height from multiple possible layer detections. We found that layer attribution is by far the most uncertain step. We tested different gradient detection techniques, and found no evidence that the first derivative, wavelet transform, and two-dimensional derivative techniques have different skills to detect one or multiple significant aerosol gradients from lidar and ceilometer attenuated backscatter. However, our study shows that, when mixing height retrievals from a ultraviolet lidar and a near-infrared ceilometer agreed, they were 25–40% more likely to agree with an independent radiosonde mixing height retrieval than when each lidar or ceilometer was used alone. Furthermore, we point to directions that may assist the layer attribution step, for instance using commonly available surface measurements of radiation and temperature to derive surface sensible heat fluxes as a proxy for the intensity of convective mixing. It is a worthwhile effort to pursue such studies so that within a few years automatic profiling lidar and ceilometer networks can be utilized efficiently to monitor mixing heights at the European scale. 

A method of measurement of the Dielectric Constant of some liquids A method of measurement of the Dielectric Constant of some liquids

Date added: 01/01/1977
Date modified: 08/06/2009
Filesize: 1.3 MB

Jennings S.G., A method of measurement of the dielectric constant of some liquids. Phys. Educ. Vol 12, January 1977. pp. 40-42.


Abstract


The method depends on the existence of a driving force on a liquid dielectric in an electric field. The force leads to a rise in the liquid level between the plates of a capacitor. The capacitor plates were placed just above a reservoir of the dielectric liquid, the level of which was monitored by a travelling microscope. The rise in liquid level (h) was measured for selected values of voltage (v) until sparking between the plates occurred. A plot of h against V2 was obtained, and the dielectric constant was determined from the slope of the graph.

Wet properties affecting Atmospheric Aerosols Wet properties affecting Atmospheric Aerosols

Date added: 08/01/1998
Date modified: 09/11/2009
Filesize: 6.2 MB
Jennings. S.G, Wet properties affecting Atmospheric Aerosols, 1998, Atmospheric Particles, Pg 476-502, Wiley & Sons

Abstract

 

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

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.

 

Wind speed dependent size-resolved parameterization for the organic enrichment of sea spray Wind speed dependent size-resolved parameterization for the organic enrichment of sea spray

Date added: 08/25/2011
Date modified: 11/17/2011
Filesize: 714.57 kB

Gantt, B, N. Meskhidze, M.C. Facchini, M. Rinaldi, D. Ceburnis, C.D. O’Dowd, Wind speed dependent size-resolved parameterization for the organic enrichment of sea spray, Atmos. Chem. Phys., 11, 1–13, 2011, www.atmos-chem-phys.net/11/1/2011/doi:10.5194/acp-11-1-2011


Abstract: For oceans to become a significant source of primary organic aerosol, sea spray must be highly enriched with organics relative to the bulk seawater.  We propose that organic enrichment at the air-sea interface, chemical composition of seawater, and the aerosol size are three main parameters controlling the organic mass fraction of sea spray aerosol (OMss).  To test this hypothesis, we developed a new marine primary organic aerosol emission function based on a conceptual relationship between the organic enrichment at the air-sea interface and surface wind speed.  The resulting parameterization is explored using aerosol chemical composition and surface wind speed from Atlantic and Pacific coastal stations, and satellite-derived ocean concentrations of chlorophyll-a, dissolved organic carbon, and particulate organic carbon.  Of all the parameters examined, a multi-variable logistic regression revealed that the combination of 10 meter wind speed and surface chlorophyll-a concentration ([Chl-a]) are the most consistent predictors of OMss.  This relationship, combined the published aerosol size dependence of OMss, resulted in a new parameterization for the organic carbon fraction of sea spray.  Global marine primary organic emission is investigated here by applying this newly-developed relationship to existing sea spray emission functions, satellite-derived [Chl-a], and modeled 10 meter winds.  Analysis of model simulations show that global annual submicron marine organic emission associated with sea spray is estimated to be from 2.8 to 5.6 Tg C yr-1.  This study provides additional evidence that marine primary organic aerosols are a globally significant source of organics in the atmosphere.

 

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.

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 Photo-Electric Counter The Photo-Electric Counter

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

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.

Sulfur in the Atmosphere Sulfur in the Atmosphere

Date added: 07/27/1995
Date modified: 07/27/2009
Filesize: 3.37 MB
Berresheim H., Wine P.H, Davis D.D,Sulfur in the Atmosphere, 1995

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%.

Opendda: a Novel High-Performance Computational Framework for the Discrete Dipole Approximation Opendda: a Novel High-Performance Computational Framework for the Discrete Dipole Approximation

Date added: 02/15/2011
Date modified: 02/15/2011
Filesize: 1.26 MB

James Mc Donald, Aaron Golden, and S. Gerard Jennings

Opendda: a Novel High-Performance Computational Framework for the Discrete Dipole Approximation.  International Journal of High Performance Computing Applications, February 2009 23: 42-61, doi:10.1177/1094342008097914, 2009

This work presents a highly optimized computational framework for the Discrete Dipole Approximation, a numerical method for calculating the optical properties associated with a target of arbitrary geometry that is widely used in atmospheric, astrophysical and industrial simulations. Core optimizations include the bit-fielding of integer data and iterative methods that complement a new Discrete Fourier Transform (DFT) kernel, which efficiently calculates the matrix— vector products required by these iterative solution schemes. The new kernel performs the requisite 3-D DFTs as ensembles of 1-D transforms, and by doing so, is able to reduce the number of constituent 1-D transforms by 60% and the memory by over 80%. The optimizations also facilitate the use of parallel techniques to further enhance the performance. Complete OpenMP-based shared-memory and MPI-based distributed-memory implementations have been created to take full advantage of the various architectures. Several benchmarks of the new framework indicate extremely favorable performance and scalability.

 

 

 


Intercomparison of measurement methods for black carbon aerosols Intercomparison of measurement methods for black carbon aerosols

Date added: 08/01/1999
Date modified: 07/02/2009
Filesize: 201.1 kB

Hitzenberger, R., Jennings, S.G., Larson, S.M., Dillner, A., Cachier, H., Galambos, Z., Rouc, A. and Spain, T.G. (1999). Intercomparison of measurement methods for black carbon aerosols. Atmos. Environ., 33, 2823-2833.


Abstract


In this study, two method intercomparisons were performed. One thermal and two optical methods for the measurement of black carbon (BC) were applied to laboratory generated aerosols containing only BC. For the optical measurements, an aethalometer (Hansen et al., 1984. Science of Total Environment 36, 191-196) and an integrating sphere technique (Hitzenberger et al., 1996b. Journal of Geophysical Research 101, D14, 19&unknown;601-19&unknown;606) were used. The thermal method was described by Cachier et al. (1989a. Tellus 41B, 379-390). In an additional comparison, the integrating sphere was compared to a thermal optical technique (Birch and Cary, 1996. Aerosol Science Technology 25, 221-241) on ambient aerosol samples. The absorption coefficients were obtained from transmission measurements on filter samples for both the aethalometer and the integrating sphere. The BC mass concentration for the aethalometer was derived from this absorption measurement. The BC mass concentration for the integrating sphere, however, was obtained using an independent calibration curve. The agreement between the absorption coefficient sigmaa obtained for the BC test aerosol on parallel filters with the aethalometer and the integrating sphere was satisfactory. The slope of the regression lines depended on filter type. A comparison between BC mass concentrations, however, showed that the aethalometer values were only 23% of those obtained by the integrating sphere technique indicating that for pure BC aerosols, the standard aethalometer calibration should not be used. Compared to the thermal method, the integrating sphere gave an overestimation of the BC mass concentrations by 21%. For the ambient samples, the integrating sphere and the thermal optical methods for BC mass concentration determination showed agreement within 5% of the 1:1 line, although the data were not so well correlated.

Perfluorodecalin global warming potential and first detection in the atmosphere Perfluorodecalin global warming potential and first detection in the atmosphere

Date added: 08/07/2005
Date modified: 07/23/2009
Filesize: 233.75 kB

Shine KP, Gohar LK, Hurley MD, Marston G, Martin D, Simmonds PG, Wallington TJ and Watkins M, 2005: Perfluorodecalin: global warming potential and first detection in the atmosphere. Atmospheric Environment doi:10.1016/j.atmosenv.2005.01.001


Abstract


Perfluorodecalin (C10F18) has a range of medical uses that have led to small releases. Recently, it has been proposed as a carrier of vaccines, which could lead to significantly larger emissions. Since its emissions are controlled under the Kyoto Protocol, it is important that values for the global warming potential (GWP) are available. For a 50:50 mixture of the two isomers of perfluorodecalin, laboratory measurements, supplemented by theoretical calculations, give an integrated absorption cross-section of 3.91×10−16 cm2 molecule−1 cm−1 over the spectral region 0–1500 cm−1; calculations yield a radiative efficiency of 0.56 W m−2 ppbv−1 and a 100-year GWP, relative to carbon dioxide, of 7200 assuming a lifetime of 1000 years. We report the first atmospheric measurements of perfluorodecalin, at Bristol, UK and Mace Head, Ireland, where volume mixing ratios are about 1.5×10−15. At these concentrations, it makes a trivial contribution to climate change, but on a per molecule basis it is a potent greenhouse gas, indicating the need for careful assessment of its possible future usage.

 

Relationship between visible extinction absorption and mass concentration of carbonaceous smokes Relationship between visible extinction absorption and mass concentration of carbonaceous smokes

Date added: 07/31/1980
Date modified: 07/06/2009
Filesize: 1.99 MB

Jennings, S.G., and Pinnick, R.G. (1980)- Relationships between visible extinction, absorption and mass concentration of carbonaceous smokes. Atmos. Environ., 14, 1123-1129.


Abstract


A linear relation, independent of the size distribution, between visible and near-i.r. extinction coefficient σe(m−1) and mass concentration M (gm−3) of carbonaceous smokes is predicted. For a wavelength λ = 0.55μm the relation is σe/M = 9.5m2g−1, assuming a particle density of 2gcm−3. The relation is in good agreement with measurements on coal-fired stack plumes, oil smoke, soot and diesel exhaust that are available in the literature. A similar relationship between carbonaceous smoke visible and near-i.r. absorption coefficient σa, and mass concentration is also derived. The relations suggest that integrated mass concentration along a path within a carbonaceous smoke cloud can be inferred from measurement of the transmission from one end of the path to the other, and that the mass concentration at a particular location in the cloud can be determined from an in situ measurement of aerosol absorption at that location with a visible or near-i.r. laser spectrophone.

Iodine dioxide nucleation simulations in coastal and remote marine environments Iodine dioxide nucleation simulations in coastal and remote marine environments

Date added: 04/08/2009
Date modified: 07/28/2009
Filesize: 685.8 kB
Vuollekoski, H., V.-M. Kerminen, T. Anttila, S.-L. Sihto, M. Vana, M. Ehn, H. Korhonen, G. McFiggans, C. D. O’Dowd and M. Kulmala,,  Iodine dioxide nucleation simulations in coastal and remote marine environments, J. Geophys. Res., 114, D02206, doi:10.1029/2008JD010713, 2008

Abstract

 

Aerosol dynamical box model simulations of coastal new particle formation were performed in order to investigate the nucleation and growth mechanisms in this environment. In the simulations the nucleating vapor was assumed to be iodine dioxide (OIO). Both Eulerian and Lagrangian type simulations were made and compared with observations. We tested three nucleation mechanisms: kinetic nucleation of OIO (K  [OIO]2), activation of clusters by OIO (A  [OIO]) and sulphuric acid-induced activation of clusters containing OIO (B  [OIO]  [H2SO4]). All the nucleation mechanisms provided reasonable results, although the growth of particles due to condensation is inadequate in kinetic nucleation cases as compared with experimental measurements. Growth of newly formed particles could be assisted by any low-volatility vapors should their concentration exceed 109 cm3. Using the obtained values of coefficients K, A, and B we found that nucleation driven by iodine compounds in remote marine areas is possible, but by OIO and H2SO4 alone, only a minor fraction of newly formed particles is likely to reach detectable sizes. Owing to the scavenging by coagulation with background aerosol particles, few of them will likely reach climatically relevant sizes by acting as seed particles for other low-volatility vapors. In order to elucidate the significance of our results, more detailed measurements of OIO source and photolysis rates, dimensions of precursor areas, and particle chemical composition are needed.

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 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].

Wind-driven influences on aerosol light scattering in north-east Atlantic air Wind-driven influences on aerosol light scattering in north-east Atlantic air

Date added: 03/12/2013
Date modified: 03/12/2013
Filesize: 202.6 kB

Vaishya, A., S. G. Jennings, and C. O Dowd (2012), Wind-driven influences on aerosol light scattering in north-east Atlantic air, Geophys. Res. Lett., 39 , L05805, doi:10.1029/ 2011GL050556.


 

Abstract. Ten years (20012010) of aerosol light-scattering measurements in N.E. Atlantic marine air are analysed to determine wind-speed related influences on scattering properties. The scattering coefficient and the backscattering coefficient dependency on wind speed (U) was determined for the winter (Low Biological Activity-LBA) and the summer seasons (High Biological Activity-HBA), and was found to be dependent on ~ U2. In spite of having a U2 dependency, scattering properties for the LBA-period are approximately twice those of the HBA-period. 96% of the LBA-HBA scattering difference can be explained by the combined effects of size distribution and refractive index differences while 70% of the scattering difference can be attributed to a difference in refractive index alone resulting from organic-matter enrichment during the HBA period. The 550 nm scattering coefficient was ~ 70 Mm-1 for ~ 25 ms-1 wind speeds, which is considerably higher than that encountered under polluted air masses in the same region. Indeed, Mulcahy et al. [2008] reported a high correlation between aerosol optical depth (AOD) and wind-speed with AOD values of 0.30.4 at moderately high wind speed. They found a power-law dependency between wind speed and AOD and suggested that sea spray contributed significantly to the direct radiative effect. O’Dowd et al. [1999] highlighted the preferential activation of sea salt nuclei over sulphate nuclei in marine clouds, while Ovadnevaite et al. [2011] found that even the water insoluble organic sea spray plumes have almost a 100% activation efficiency even at a low supersaturation of 0.2%, pointing to a significant role for sea spray in the direct radiative effect. While there have been many studies of aerosol lightscattering in remote locations and in marine air [Bodhaine, 1996; Parameswaran et al., 1998; Pereira et al., 2011], there have been few studies [e.g., Kleefeld et al., 2002] that have reported wind-dependent scattering dependency. The aim of present study is to establish a wind-speed scattering relationship for clean marine air masses for conditions representative of periods with high organic matter enrichment and periods with low organic matter enrichment.

 

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.

 

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

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

Abstract


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

Primary submicron marine aerosol dominated by insoluble organic colloids and aggregates Primary submicron marine aerosol dominated by insoluble organic colloids and aggregates

Date added: 04/08/2009
Date modified: 11/01/2009
Filesize: 220.61 kB
Facchini, M.C.,  M. Rinaldi, S. Decesari, C. Carbone, E. Finessi, M. Mircea, S. Fuzzi, D. Ceburnis, R.  Flanagan, E. D. Nillsson, G.  de Leeuw, M. Martino,  J. Woeltjen and C.D. O’ Dowd, Primary submicron marine aerosol dominated by insoluble organic colloids and aggregates,, Geophys. Res. Letts., doi:10.1029/2008GL034210, 2008.

Abstract

 

The chemical properties of sea-spray aerosol particles produced by artificially generated bubbles using oceanic waters were investigated during a phytoplankton bloom in the North Atlantic. Spray particles exhibited a progressive increase in the organic matter (OM) content from 3 ± 0.4% up to 77 ± 5% with decreasing particle diameter from 8 to 0.125 mm. Submicron OM was almost entirely water insoluble (WIOM) and consisted of colloids and aggregates exuded by phytoplankton. Our observations indicate that size dependent transfer of sea water organic material to primary marine particles is mainly controlled by the solubility and surface tension properties of marine OM. The pattern of WIOM and sea-salt content in the different size intervals observed in bubble bursting experiments is similar to that measured in atmospheric marine aerosol samples collected during periods of high biological activity. The results point to a WIOM/sea-salt fingerprint associated with submicron primary marine aerosol production in biologically rich waters.

Accumulation rates of the heavy metals lead, mercury and cadmium in ombrotrophic peatlands in the We Accumulation rates of the heavy metals lead, mercury and cadmium in ombrotrophic peatlands in the We

Date added: 08/26/2006
Date modified: 07/09/2009
Filesize: 788.52 kB

Coggins, A. M.; Jennings, S. G.; Ebinghaus, R. (2006): Accumulation rates of the heavy metals lead, mercury and cadmium in ombrotrophic peatlands in the west of Ireland, Atmospheric Environment, 40, 260 - 270


Abstract


The vertical distributions of three heavy metals: Hg, Pb and Cd were determined in 3 cores sampled from two ombrotrophic bogs in the west of Ireland, one at Knockroe Co. Mayo, and the second at Letterfrack National Park, Co. Galway. Core chronologies were established using 210Pb dating techniques and were checked with fallout radionuclides from weapons testing. Variations were found in metal concentrations and cumulative inventories of each of the metals within each site and between the two sites. Maximum accumulation rates of the anthropogenically derived elements Hg, Pb, and Cd, were found in peat sediments dated between 1950 and 1970s at both sites. Pb and Hg accumulation rates are slightly lower than those found in similar studies from remote sites in Europe. Hg accumulation rates are fairly similar to those found in peatlands in America. Unlike the Pb and Hg concentration profiles, the Cd concentration profiles at the Letterfrack site were dominated by a surface enrichment, thought to be due to biological cycling of Cd in the peat. However Cd accumulation rates calculated at the Knockroe site are lower than those observed in Eastern Europe. Local meteorological conditions at the sites chosen for this study may account for the lower concentrations profiles observed when compared with some of the European studies. The similarity between the timing of the increase in metal accumulation rates in peat bogs in Northern America and this study could indicate that long range transportation of trace metals from Northern America may be occurring. Lead accumulations in the surface peat sediments (1993–1996) were between 1.5–3.0 mgm2 yr1 and 4–5 mgm2 yr1 at Knockroe and Letterfrack, respectively. Mercury accumulation rates for the same period at Knockroe were found to be between 6–11 mgm2 yr1, and between 19–24 mgm2 yr1 at Letterfrack. A greater variation in surface Cd accumulation rates was observed at both sites, with surface layer accumulation rates varying from 25 to 50 mgm2 yr1 at Knockroe and between 166 and 405 mgm2 yr1 at Letterfrack. Higher metal concentrations were found at the Letterfrack site, which are most likely due to local sources and the history of the site.

Significant enhancement of aerosol optical depth in marine air under high wind conditions Significant enhancement of aerosol optical depth in marine air under high wind conditions

Date added: 09/12/2008
Date modified: 07/06/2009
Filesize: 479.23 kB

Mulcahy, J. P., C. D. O'Dowd, S. G. Jennings, and D. Ceburnis (2008), Significant enhancement of aerosol optical depth in marine air under high wind conditions, Geophys. Res. Lett., 35, L16810, doi:10.1029/2008GL034303.


Abstract


The relationship between the AOD and wind speed (U), obtained at the Mace Head atmospheric research station, is determined for clean marine (Northeast Atlantic) conditions under steady-state wind speed scenarios. AOD measurements were made under much higher wind speed conditions (up to 18 m s−1) than hitherto measured. The AOD is found to be approximately dependent on U2, with a high correlation (r2 = 0.97) determined at all measured wavelengths of 862 nm, 500 nm, 412 nm and 368 nm. A corresponding anti-correlation was observed between the Ångström exponent and wind speed (r2 = 0.93). The results illustrate that under moderate-to-high wind conditions, sea-spray AOD can rival or even exceed that associated with pollution plumes over oceanic regions and can potentially contribute to radiative, dynamical and biogeochemical feedback processes associated with future climate change.

 

Contributions of Primary Organic Matter to Marine Aerosol Contributions of Primary Organic Matter to Marine Aerosol

Date added: 01/31/2011
Date modified: 01/31/2011
Filesize: 583.72 kB

Ovadnevaite, J., M. Dall'Osto, D. Ceburnis, C. Monahan, D. Worsnop, C. O’Dowd and H. Berresheim Detecting Very High Contributions of Primary Organic Matter to Marine Aerosol, Geophys. Res. Letts., doi:10.1029/2010GL046083 , 2011.


Using on‐line High‐Resolution Aerosol Mass Spectrometry, we report submicron organic marine aerosol plume concentrations peaking at 3.8 mg m−3. These concentrations are far greater than previously determinedby off‐line techniques and can exceed typica terrestrial concentrations of organic aerosol. The organic mass comprised 77% of the total submicron non‐refractory mass and such plumes were associated with regions of high biological activity and moderately‐high wind speeds over the N.E. Atlantic. High‐resolution mass spectra analysis revealed a unique marine organic aerosol fingerprint, when compared to anthropogenic organic aerosol, and in particular, anthropogenic hydrocarbons. 37% hydrocarbon and 63% oxygenated hydrocarbon speciation was observed for the organic mass, indicating that at least 37% of the organic mass is produced via primary sea‐spray. The hydrocarbon and oxygenated hydrocarbon species were highly correlated (r > 0.99) suggesting a significant, if not dominant, fraction of the oxygenated component is also likely to be sea‐spray in origin.

Electrical charging of water drops in polarizing electric fields. Electrical charging of water drops in polarizing electric fields.

Date added: 08/01/1975
Date modified: 07/01/2009
Filesize: 2.02 MB

Jennings, S.G.  (1974)- Electrical charging of water drops in polarizing electric fields.  J. Electrostatics, 1,  15-25.


Abstract


Measurements were made of the electric charge acquired by drops of mean radius of about 750 μm as they fell through a cloud of water droplets of mean radius 16 μm, in the presence of a vertical electric field E, the value of which could be varied from 4.5 to 27 kV m−1. It was found that the proportion of interactions which resulted in separation (and, therefore, in electric charge transfer, as a consequence of the inductive process of electrification) decreased from about 1% in the weaker fields to about 0.2% in the strongest ones.

This work suggests that the collisions between polarised raindrops and cloud droplets in natural clouds could give rise, very effectively, to the production of electric fields of about 30 kV m−1 but that significantly larger fields could not be produced since all collisions in higher fields would result in permanent coalescence.

Surfactants and Submicron sea spray generation Surfactants and Submicron sea spray generation

Date added: 08/01/2006
Date modified: 07/07/2009
Filesize: 1.86 MB
Sellegri, K., C. D. O'Dowd, Y. J. Yoon, S. G. Jennings, and G. de Leeuw, Surfactants and submicron sea spray generation, J. Geophys. Res., 111, D22215, doi:10.1029/2005JD006658, 2006.

Abstract


Laboratory experiments have been carried out to elucidate the role of surfactants on the primary marine aerosol production of submicron marine aerosols. A synthetic surfactant SDS was used in conjunction with artificially generated seawater, and the resultant bubble-mediated aerosol produced was observed. At 23°C, the aerosol distribution resulting from the use of surfactant-free seawater comprised three modes: (1) a dominant accumulation mode at 110 nm; (2) an Aitken mode at 45 nm; and (3) a third mode, at 300 nm, resulting from forced bursting of bubbles. The forced bursting occurs when bubbles fail to burst upon reaching the surface and are later shattered by splashing associated with breaking waves and/or wind pressure at the surface. At 4°C, the accumulation mode diameter was reduced to 85 nm, the Aitken mode diameter was reduced to <30 nm and the 300 nm mode diameter was reduced to 200 nm. With the addition of SDS, the relative importance of the mode resulting from forced bursting increased dramatically. The laboratory results were compared to the observed seasonality of North Atlantic marine aerosol where a progression from mode radii minima in winter to maxima in summer is seen. The bimodality and the seasonality in modal diameter can be mostly explained by a combination of the three modes observed in the laboratory and their variation as a function of sea-surface temperature and seawater surfactant concentration. These results indicate that submicron primary aerosol modes would on a first approximation result from bubble bursting processes, although evidences of additional secondary processes leading, during summer, to a higher amplitude of the Aitken mode and mode 2 smoothed into mode 3 still need to be investigated.

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

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

Abstract


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

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.

 

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.

Seasonal Characteristics of the physicochemical properties of the North Atlantic marine atmospheric Aerosols Seasonal Characteristics of the physicochemical properties of the North Atlantic marine atmospheric Aerosols

Date added: 08/01/2007
Date modified: 07/06/2009
Filesize: 725.93 kB
Yoon, Y.J., D. Ceburnis, F. Cavalli, O. Jourdan, J.P. Putaud, M.C. Facchini, S. Descari, S. Fuzzi, , S.G. Jennings, C.D. O’Dowd. Seasonal characteristics of the physico-chemical properties of North Atlantic marine atmospheric aerosols J. Geophys. Res., doi:10.1029/2005JD007044, 2007.

Abstract


Seasonal physicochemical characteristics of North Atlantic marine aerosols are presented for the period from January 2002 to June 2004. The aerosol size distribution modal diameters show seasonal variations, 0.031 μm in winter and 0.049 μm in summer for the Aitken mode and 0.103 μm in winter and 0.177 μm in summer for the accumulation mode. The accumulation mode mass also showed a seasonal variation, minimum in winter and maximum in summer. A supermicron sized particle mode was found at 2 μm for all seasons showing 30% higher mass concentration during winter than summer resulting from higher wind speed conditions. Chemical analysis showed that the concentration of sea salt has a seasonal pattern, minimum in summer and maximum in winter because of a dependency of sea-salt load on wind speeds. By contrast, the non-sea-salt (nss) sulphate concentration in fine mode particles exhibited lower values during winter and higher values during midsummer. The water soluble organic carbon (WSOC) and total carbon (TC) analysis also showed a distinctive seasonal pattern. The WSOC concentration during the high biological activity period peaked at 0.2 μgC m−3, while it was lower than 0.05 μgC m−3 during the low biological activity period. The aerosol light scattering coefficient showed a minimum value of 5.5 Mm−1 in August and a maximum of 21 Mm−1 in February. This seasonal variation was due to the higher contribution of sea salt in the MBL during North Atlantic winter. By contrast, aerosols during late spring and summer exhibited larger angstrom parameters than winter, indicating a large contribution of the biogenically driven fine or accumulation modes. Seasonal characteristics of North Atlantic marine aerosols suggest an important link between marine aerosols and biological activity through primary production of marine aerosols.

Experiments on water drop interactions Experiments on water drop interactions

Date added: 09/06/1977
Date modified: 08/06/2009
Filesize: 1.27 MB

Jennings, S.G. (1977)- Experiments on water drop interactions. Phys. Ed., 12, 381-385.


Abstract

 

A series of experiments is described which demonstrate the interactions of water drops. These experiments were used in a project with second year undergraduates and should be easy to adapt for school use. Photographic, stroboscopic and droplet stream formation techniques are used. Droplet-droplet collisions and collisions with plane and curved air-water interfaces are involved. It is considered that the experiments provide a good basis for the understanding of the relative roles of kinetic energy and surface energy in governing water droplet behaviour.

Equilibrium Size of Atmospheric Aerosol Sulfates as a Function of Particle Acidity and Ambient Relative Humidity Equilibrium Size of Atmospheric Aerosol Sulfates as a Function of Particle Acidity and Ambient Relative Humidity

Date added: 07/31/1993
Date modified: 07/01/2009
Filesize: 557.48 kB

Kelly, B.P., & Koutrakis, P. (1993)- Equilibrium size of atmospheric aerosol sulphates as a function of particle acidity and ambient relative humidity. J. Geophy. Res. 98, pp. 7141-7147.


Abstract


Acid aerosol events in Uniontown, Pennsylvania, were studied during the summer of 1990. Size-fractionated acid aerosols were collected using a microorifice cascade impactor. The collected samples were analyzed for hydrogen, sulfate, nitrate, and ammonium ion concentrations. These measurements show evidence of a relationship between the mass median geometric aerodynamic diameter of sulfate particles and both particle acid content (H+/SO4=) and ambient relative humidity. Sulfate particle size increases with both increasing acid content and relative humidity. Considering the uncertainties involved, the growth of atmospheric sulfate particles observed in this study was found to be in good agreement with that predicted on the basis of laboratory-derived data. To our knowledge, this is the first time that such a relationship has been observed under real atmospheric conditions. Therefore the results of this study suggest that laboratory experiments and thermodynamic calculations can be used in order to understand the chemistry of atmospheric sulfates and their impacts on visibility reduction. In addition, we present evidence to suggest that the chemical composition of acid aerosol particles may be related to the ambient relative humidity.

A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE

Date added: 01/01/2000
Date modified: 07/27/2009
Filesize: 4.55 MB
Prinn, R. G., et al. (2000), A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE, J. Geophys. Res., 105(D14), 17,751–17,792.

Abstract


We describe in detail the instrumentation and calibrations used in the Atmospheric Lifetime Experiment (ALE), the Global Atmospheric Gases Experiment (GAGE), and the Advanced Global Atmospheric Gases Experiment (AGAGE) and present a history of the majority of the anthropogenic ozone-depleting and climate-forcing gases in air based on these experiments. Beginning in 1978, these three successive automated high-frequency in situ experiments have documented the long-term behavior of the measured concentrations of these gases over the past 20 years, and show both the evolution of latitudinal gradients and the high-frequency variability due to sources and circulation. We provide estimates of the long-term trends in total chlorine contained in long-lived halocarbons involved in ozone depletion. We summarize interpretations of these measurements using inverse methods to determine trace gas lifetimes and emissions. Finally, we provide a combined observational and modeled reconstruction of the evolution of chlorocarbons by latitude in the atmosphere over the past 60 years which can be used as boundary conditions for interpreting trapped air in glaciers and oceanic measurements of chlorocarbon tracers of the deep oceanic circulation. Some specific conclusions are as follows: (1) International compliance with the Montreal Protocol is so far resulting in chlorofluorocarbon and chlorocarbon mole fractions comparable to target levels; (2) mole fractions of total chlorine contained in long-lived halocarbons (CCl2F2, CCl3F, CH3CCl3, CCl4, CHClF2, CCl2FCClF2, CH3Cl, CH2Cl2, CHCl3, CCl2=CCl2) in the lower troposphere reached maximum values of about 3.6 ppb in 1993 and are beginning to slowly decrease in the global lower atmosphere; (3) the chlorofluorocarbons have atmospheric lifetimes consistent with destruction in the stratosphere being their principal removal mechanism; (4) multiannual variations in chlorofluorocarbon and chlorocarbon emissions deduced from ALE/GAGE/AGAGE data are consistent approximately with variations estimated independently from industrial production and sales data where available (CCl2F2 (CFC-12) and CCl2FCClF2 (CFC-113) show the greatest discrepancies); (5) the mole fractions of the hydrochlorofluorocarbons and hydrofluorocarbons, which are replacing the regulated halocarbons, are rising very rapidly in the atmosphere, but with the exception of the much longer manufactured CHClF2 (HCFC-22), they are not yet at levels sufficient to contribute significantly to atmospheric chlorine loading. These replacement species could in the future provide independent estimates of the global weighted-average OH concentration provided their industrial emissions are accurately documented; (6) in the future, analysis of pollution events measured using high-frequency in situ measurements of chlorofluorocarbons and their replacements may enable emission estimates at the regional level, which, together with industrial end-use data, are of sufficient accuracy to be capable of identifying regional noncompliance with the Montreal Protocol.

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

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

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


Abstract


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

A general circulation model study of the global carbonaceous aerosol distribution A general circulation model study of the global carbonaceous aerosol distribution

Date added: 08/06/2002
Date modified: 07/27/2009
Filesize: 1.81 MB

Cooke, W. F., V. Ramaswamy, and P. Kasibhatla (2002), A general circulation model study of the global carbonaceous aerosol distribution, J. Geophys. Res., 107(D16), 4279, doi:10.1029/2001JD001274.


Abstract


Atmospheric distributions of carbonaceous aerosols are simulated using the Geophysical Fluid Dynamics Laboratory SKYHI general circulation model (GCM) (latitude-longitude resolution of ∼3° × 3.6°). A number of systematic analyses are conducted to investigate the seasonal and interannual variability of the concentrations at specific locations and to investigate the sensitivity of the distributions to various physical parameters. Comparisons are made with several observational data sets. At four specific sites (Mace Head, Mauna Loa, Sable Island, and Bondville) the monthly mean measurements of surface concentrations of black carbon made over several years reveal that the model simulation registers successes as well as failures. Comparisons are also made with averages of measurements made over varying time periods, segregated by geography and rural/remote locations. Generally, the mean measured remote surface concentrations exceed those simulated. Notwithstanding the large variability in measurements and model simulations, the simulations of both black and organic carbon tend to be within about a factor of 2 at a majority of the sites. There are major challenges in conducting comparisons with measurements due to inadequate sampling at some sites, the generally short length of the observational record, and different methods used for estimating the black and organic carbon amounts. The interannual variability in the model and in the few such measurements available points to the need for doing multiyear modeling and to the necessity of comparing with long-term measurements. There are very few altitude profile measurements; notwithstanding the large uncertainties, the present comparisons suggest an overestimation by the model in the free troposphere. The global column burdens of black and organic carbon in the present standard model integration are lower than in previous studies and thus could be regarded as approximately bracketing a lower end of the simulated anthropogenic burden due to these classes of aerosols, based on the current understanding of the carbonaceous aerosol cycle. Of the physical factors examined, the intensity and frequency of precipitation events are critical in governing the column burdens. Biases in the frequency of precipitation are likely the single biggest cause of discrepancies between simulation and observations. This parameter is available from very few sites and thus lacks a comprehensive global data set, unlike, say, monthly mean precipitation. Several multiyear GCM integrations have been performed to evaluate the sensitivity of the global mean black carbon distribution to the principal aerosol parameters, with due regard to variability and statistical significance. The most sensitive parameters, in order of importance, turn out to be the wet deposition, transformation from hydrophobic to hydrophilic state, and the partitioning of the emitted aerosol between the hydrophobic and hydrophilic varieties. From the sensitivity tests, it is estimated that the variations of the global mean column burden and lifetime of black carbon are within about a factor of 2 about their respective standard values. The studies also show that the column burdens over remote regions appear to be most sensitive to changes in each parameter, reiterating the importance of measurements in those locations for a proper evaluation of model simulation of these aerosols.

 

A burning question. Can recent growth rate anomalies in the greenhouse gases be attributed to l A burning question. Can recent growth rate anomalies in the greenhouse gases be attributed to l

Date added: 08/07/2005
Date modified: 09/11/2009
Filesize: 181.92 kB

P.G. Simmonds,A. J.Manning,R.G. Derwent, P. Ciais,M.Ramonet, V. Kazan and D. Ryall, A burning question. Can recent growth rate anomalies in the greenhouse gases be attributed to large-scale biomass burning events?, Atmos. Environ., 2005, 39, 2513–2517.


Abstract

 

Simultaneous in situ measurements of carbon dioxide (CO2) and the principal gases linked to biomass burning at the Mace Head Observatory, Ireland, reveal a strong correlation in 1998-99 and 2002-03, both periods with intense global fires. CO2, carbon monoxide (CO), methane (CH4), hydrogen (H2), ozone (O3) and methyl chloride (CH3Cl), all have similar rates of accumulation during these time frames. These perturbations imply a causal relationship between large-scale biomass burning events and the interannual variability of these gases.

 

Seasonal Characteristics of the physicochemical properties of the North Atlantic marine atmospheric Seasonal Characteristics of the physicochemical properties of the North Atlantic marine atmospheric

Date added: 08/01/2007
Date modified: 07/13/2009
Filesize: 725.93 kB
Yoon, Y.J., D. Ceburnis, F. Cavalli, O. Jourdan, J.P. Putaud, M.C. Facchini, S. Descari, S. Fuzzi, , S.G. Jennings, C.D. O’Dowd. Seasonal characteristics of the physico-chemical properties of North Atlantic marine atmospheric aerosols J. Geophys. Res., doi:10.1029/2005JD007044, 2007.

Abstract

 

Seasonal physicochemical characteristics of North Atlantic marine aerosols are presented for the period from January 2002 to June 2004. The aerosol size distribution modal diameters show seasonal variations, 0.031 mm in winter and 0.049 mm in summer for the Aitken mode and 0.103 mm in winter and 0.177 mm in summer for the accumulation mode. The accumulation mode mass also showed a seasonal variation, minimum in winter and maximum in summer. A supermicron sized particle mode was found at 2 mm for all seasons showing 30% higher mass concentration during winter than summer resulting from higher wind speed conditions. Chemical analysis showed that the concentration of sea salt has a seasonal pattern, minimum in summer and maximum in winter because of a dependency of sea-salt load on wind speeds. By contrast, the nonsea-salt (nss) sulphate concentration in fine mode particles exhibited lower values during winter and higher values during midsummer. The water soluble organic carbon (WSOC) and total carbon (TC) analysis also showed a distinctive seasonal pattern. The WSOCconcentration during the high biological activity period peaked at 0.2 mgC m3, while it was lower than 0.05 mgC m3 during the low biological activity period. The aerosol light scattering coefficient showed a minimum value of 5.5 Mm1 in August and a maximum of 21 Mm1 in February. This seasonal variation was due to the higher contribution of sea salt in the MBL during North Atlantic winter. By contrast, aerosols during late spring and summer exhibited larger angstrom parameters than winter, indicating
a large contribution of the biogenically driven fine or accumulation modes. Seasonal characteristics of North Atlantic marine aerosols suggest an important link between marine aerosols and biological activity through primary production of marine aerosols.

Local and regional air pollution in Ireland during an intensive aerosol measurement campaign Local and regional air pollution in Ireland during an intensive aerosol measurement campaign

Date added: 08/01/2006
Date modified: 07/02/2009
Filesize: 1.1 MB

Ceburnis, D., J. Yin, A.G. Allen, S.G. Jennings, R.M. Harrison, E. Wright, M. Fitzpatrick, T. Healy, and E. Barry, Local and regional air pollution in Ireland during an intensive aerosol measurement campaign, J. Environ. Monitoring, 8, 479-487, 2006.


Abstract

 

An intensive two month measurement campaign has been performed during a two year study of major component composition of urban PM10 and PM2.5 in Ireland (J. Yin, A. G. Allen, R. M. Harrison, S. G. Jennings, E. Wright, M. Fitzpatrick, T. Healy, E. Barry, D. Ceburnis and D. McCusker, Atmos. Res., 2005, 78(3–4), 149–165). Measurements included size-segregated mass, soluble ions, elemental carbon (EC) distributions, fine and coarse fraction organic carbon (OC) and major gases along with standard meteorological measurements. The study revealed that urban emissions in Ireland had mainly a local character and therefore were confined within a limited area of 20–30 km radius, without significantly affecting regional air quality. Gaseous measurements have shown that urban emissions in Ireland had clear, but fairly limited influence on the regional air quality due to favorable mixing conditions at higher wind speeds, in particular from the western sector. Size-segregated mass and chemical measurements revealed a clear demarcation size between accumulation and coarse modes at about 0.8 µm which was constant at all sites. Carbonaceous compounds at the urban site accounted for up to 90% of the particle mass in a size range of 0.066–0.61 µm. Nss SO42– concentrations in PM2.5 were only slightly higher at the urban site compared to the rural or coastal sites, while NO3 and NH4+ concentrations were similar at the urban and coastal sites, but were a factor of 2 to 3 higher than at the rural site. OC was highly variable between the sites and revealed clear seasonal differences. Natural or biogenic OC component accounted for <10% in winter and up to 30% in summer of the PM2.5 OC at urban sites. A contribution of biogenic OC component to PM2.5 OC mass at rural site was dominant.

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.

 

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