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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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Seasonal variation of carbon monoxide at remote sites in Japan Seasonal variation of carbon monoxide at remote sites in Japan

Date added: 08/07/1999
Date modified: 07/23/2009
Filesize: 183.89 kB
Narita D.; Pochanart P.; Matsumoto J.; Someno K.; Tanimoto H.; Hirokawa J.; Seasonal variation of carbon monoxide at remote sites in Japan, Chemosphere: Global Science Change, Volume 1, Number 1, August 1999 , pp. 137-144(8)

Abstract


Continuous measurement of CO has been carried out at remote sites in Japan, Oki (36oN), Happo (36oN) and Benoki (27oN). Seasonal variation at each site exhibited a clear cycle with a maximum in spring and a minimum in summer. It has been revealed that the concentrations of CO at Oki are substantially higher than at Mace Head throughout a year. Comparison of trajectory-categorized data between Oki and Mace Head has been made to elucidate that the concentration at Oki is higher than Mace Head both in the clean ''background'' and in the regionally polluted air mass. The spring maximum at Oki occurs in April that is one month later than the reported data at other remote sites in the northern hemisphere.

 

 

Modeled Optical Thickness of the Sea Salt Aerosol Over the World Ocean Modeled Optical Thickness of the Sea Salt Aerosol Over the World Ocean

Date added: 08/04/2011
Date modified: 08/05/2011
Filesize: 1.17 MB

Madry, L.M., O.B. Toon, C. D. O’Dowd, Modeled Optical Thickness of the Sea Salt Aerosol Over the World Ocean, J. Geophys. Res. doi:10.1029/2010JD014691, 2011.


We simulate the generation and microphysical evolution of seas

alt aerosol using a climatologically driven 3D microphysical model for the year 2006. We then apply Mie theory to calculate the extinction and scattering efficiencies of our transported, sizeresolved seasalt aerosol, accounting for hygroscopic growth due to changes in ambient relative humidity. We calculate the column optical thickness of our modeled seasalt aerosol for comparison to three previously published wind speeddependent clean  marine air optical thickness formulations. Variously derived from optical thickness measurements and retrievals taken from the Midway Island AERONET site, the satellitebased MODIS instruments, and the Global Atmospheric Watch (GAW) site at Mace Head, Ireland, the three formulations report similar background levels of clean marine AOT at zero wind speed but significantly different functional dependencies for nonzero wind speeds. We find that our modeled seasalt aerosol optical thickness very closely depends on the square of surface wind speed under steady state conditions. This relationship is consistent across all latitudes. However, due to the fact that steady state winds are seldom maintained, the 24 h mean wind is more frequently applicable to calculations of seasalt AOT, with only slightly diminished accuracy.

A Case Study of Ship Track Formation in a Polluted Marine Boundary Layer A Case Study of Ship Track Formation in a Polluted Marine Boundary Layer

Date added: 08/06/2000
Date modified: 06/30/2009
Filesize: 509.16 kB

Noone, K. J., D. W. Johnson, et al. (2000). "A Case Study of Ship Track Formation in a Polluted Marine Boundary Layer." J. Atmos. Sci. 57(16): 2748-2764.


Abstract

 

A case study of the effects of ship emissions on the microphysical, radiative, and chemical properties of polluted marine boundary layer clouds is presented. Two ship tracks are discussed in detail. In situ measurements of cloud drop size distributions, liquid water content, and cloud radiative properties, as well as aerosol size distributions (outside-cloud, interstitial, and cloud droplet residual particles) and aerosol chemistry, are presented. These are related to remotely sensed measurements of cloud radiative properties.

The authors examine the processes behind ship track formation in a polluted marine boundary layer as an example of the effects of anthropogenic particulate pollution on the albedo of marine stratiform clouds.

 

Significant growth in surface ozone at Mace Head, Ireland, 1987–2003 Significant growth in surface ozone at Mace Head, Ireland, 1987–2003

Date added: 08/07/2004
Date modified: 07/23/2009
Filesize: 501.27 kB

Significant growth in surface ozone at Mace Head, Ireland, 1987-2003 P.G. Simmonds, R.G. Derwent, A.L. Manning, G. Spain Atmos. Environ., 38, 4769-4778, 2004


Abstract

 

Background ozone O3 observations at Mace Head on the west coast of Ireland since 1987 show a significant positive trend of 0.49 ± 0.19 ppb year-1 through to 2003. Increasing trends are observed for all seasons, with the largest trends during the winter season, 0.63±0.31 ppb year-1 and the smallest trends during the summer, 0.39 ± 0.25 ppb year-1. However, this growth rate has not been consistent over time with a major anomaly evident in 1998-1999. This major O3 perturbation is correlated with variations of CO2, CO, CH4, H2 and CH3Cl, which are likely due to large-scale biomass burning events in tropical and boreal regions during 1997-1999 coupled with an intense El Niño event. Over the 16 years of observations background O3 has increased by about 8 ppb (∼ 24%) in the clean oceanic sectors representative of the Northern Hemisphere marine boundary layer.

 

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

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

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


Abstract


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

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

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

 

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

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

Temporal patterns, sources, and sinks of C8-C16 hydrocarbons in the atmosphere of Mace Head, Ireland Temporal patterns, sources, and sinks of C8-C16 hydrocarbons in the atmosphere of Mace Head, Ireland

Date added: 08/30/2002
Date modified: 03/07/2010
Filesize: 758.23 kB
Sartin, J. H., C. J. Halsall, L. A. Robertson, R. G. Gonard, A. R. MacKenzie, H. Berresheim, and C. N. Hewitt (2002), Temporal patterns, sources, and sinks of C8-C16 hydrocarbons in the atmosphere of Mace Head, Ireland, J. Geophys. Res., 107(D19), 8099, doi:10.1029/2000JD000232.

Abstract


During the 1999 New Particle Formation and Fate in the Coastal Environment (PARFORCE) field campaign, 16 C8-C16 volatile organic compounds (VOCs) were identified in the coastal atmosphere of Mace Head, Ireland. Sampling took place over 24 days, with 12 VOCs routinely quantified. Concentrations were observed in the low <10–150 parts per trillion by volume range, with levels typically in the order of aldehydes > ketones ≥ n-alkanes. Concentrations of these compounds were also measured in shoreline surface seawater. No relationship was observed between atmospheric concentrations and high/low tide events. Many VOCs revealed a temporal pattern in the atmosphere, with highest concentrations measured during the early morning and lowest concentrations in the afternoon. The strongest pattern was observed for the n-alkanes. However, this was dependent on the prevailing air mass direction and the local meteorology. A Lagrangian box model was applied to assess this diurnal cycle, using seawater emissions as a source (based on the seawater concentrations and observed wind speeds), and depletion via OH radicals and dilution by entrainment as sinks (using measured [OH] and boundary layer height data). The model gave good agreement to the observed concentrations for selected air mass types, predicting the daytime decrease in VOC concentrations due to OH radical chemistry and boundary layer growth, and the subsequent increase in VOC concentrations toward evening as both oxidation chemistry diminished and the mixing layer height fell.

Aerosol Mass measurement at Mace Head on the West coast of Ireland Aerosol Mass measurement at Mace Head on the West coast of Ireland

Date added: 07/31/1992
Date modified: 07/27/2009
Filesize: 1.1 MB

McGovern, F.M., Jennings, S.G., Spain, T.G., O'Connor, T.C., Krasenbrink, A., Georgi, B., and Below, M. (1992)- Aerosol mass measurements at Mace Head on the west coast of Ireland. J. Aerosol Sci., 23, 5953 - 5956.


Abstract


Aerosol mass/size measurements have been carried out at the Mace Head research station, on the west coast of Ireland, for a period of over two years. Mass/size distributions were obtained in the size range 0.06-10 μm using Berner low-pressure cascade impactor systems. The distributions obtained reflect the different types of air mass which are encountered at Mace Head. Westerly winds are dominant at the site with the associated air masses being typically maritime. Unimodal mass/size distributirns with the peak mass concentration occurring principally in the 2-4 μm size range were characteristic if these conditions. Continental air masses from Europe are typified by mass/size distributions which have peak values in the submicron size range

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

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

Abstract


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

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

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

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


Abstract


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

 

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

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

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


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

 

Condensation Nuclei In maritime Air Condensation Nuclei In maritime Air

Date added: 08/07/1966
Date modified: 07/27/2009
Filesize: 858.97 kB
O'Connor, Condensation Nuclei in Maritime Air, Journal de Recherches Atmospheriques, Vol II, 2 annee (1966), no 2-3, pp 181-184
Abstract

 

Data is reported on the concentration of condensation nuclei, their size and the fraction uncharged, in maritime air at a station on the west coast of Ireland well away from sources of man-made pollution. These are correlated with some meteorological paratmeters and the state of the ocean. These observations were made mainly with on-shore winds and they supplement those of O'Connor, Sharkey and Flanagan, in Q.J..R.M.S., 87,1961,pp. 105-8.

The concentration of nuclei per cm3 varied from about 100 to 12,500 but was usually less than 1,000. The size of the nuclei decreased with increasing concentration with an average value of about 3.5 X 10^-6 cm for their radii. It did not depend markedly on the relative humidity.

Microphysical and physico-chemical characterization of atmospheric marine and continental aerosol at mace head Microphysical and physico-chemical characterization of atmospheric marine and continental aerosol at mace head

Date added: 07/31/1997
Date modified: 07/23/2009
Filesize: 1.02 MB

Jennings, S.G., Geever, M. McGovern, F.M., Francis, J., Spain, G. and Donaghy, T. (1997).- Microphysical and physico-chemical characterisation of atmospheric aerosol at Mace Head. Atmos. Environ., 31, 2795-2808.


Abstract


Measurements of the aerosol particle size, aerosol volume distribution and aerosol volatility (diameter range 0.1-3.0 μm), aerosol mass (diameter range 0.06-16.0 μm), condensation nuclei (CN) and cloud condensation nuclei (CCN), and black carbon (BC) mass concentration at Mace Head during the EU project Background Maritime Contribution to Atmospheric Pollution in Europe (BMCAPE), obtained over four intensive campaigns during the period between November 1993 and August 1994, are presented. Marine air was found to possess mean accumulation mode (ACM) aerosol particle number concentration., N, of between 100 and 160 cm-3 for the winter and summer seasons. Marine ACM mass ranged in value from about 0.8 to 6 μg m-3. Marine air was found to contain black carbon with episodic mean mass concentrations generally in the range 5-40 ng m-3. The impact of black carbon on the marine environment is also reflected by the moderately positive correlation (r2 in the range 0.23-0.44) found between marine ACM number concentration and BC mass loading, with a higher correlation (r2 = 0.55) found for winter continental air. Black carbon accounted for between 0.6% and 1.2% of the ACM mass loading for marine aerosol at Mace Head, increasing to between 4% and 6% for continental air. Arithmetic mean values of ACM number concentration N and BC mass concentration agree quite well with results from a few other investigators of marine atmospheric aerosol in the North Atlantic.

Airborne measurements of nucleation mode particles I coastal nucleation and growth rates Airborne measurements of nucleation mode particles I coastal nucleation and growth rates

Date added: 08/01/2006
Date modified: 06/30/2009
Filesize: 1.47 MB

O’Dowd, C.D, Y. J. Yoon, W. Junkerman, P. P. Aalto, and H. Lihavainen, Airborne Measurements of Nucleation Mode Particles I: Coastal Atlantic Nucleation Events. Atmos. Chem. Phys. Discuss, 6, 8097-8123, 2006.


Abstract


A light aircraft was equipped with a bank of Condensation Particle Counters (CPCs) (50% cut from 3–5.4–9.6 nm) and a nano-Scanning Mobility Particle Sizer (nSMPS) and deployed along the west coast of Ireland, in the vicinity of Mace Head. The objective of the exercise was to provide high resolution micro-physical measurements of the coastal nucleation mode in order to map the spatial extent of new particle production regions and to evaluate the evolution, and associated growth rates of the coastal nucleation-mode aerosol plume. Results indicate that coastal new particle production is occurring over most areas along the land-sea interface with peak concentrations at the coastal plume-head in excess of 106 cm−3. Pseudo-Lagrangian studies of the coastal plume evolution illustrated significant growth of new particles to sizes in excess of 8 nm approximately 10 km downwind of the source region. Close to the plume head (<1 km) growth rates can be as high as 123–171 nm h−1, decreasing gradually to 53–72 nm h−1 at 3 km. Further along the plume, at distances up to 10 km, the growth rates are calculated to be 17–32 nm h−1. Growth rates of this magnitude suggest that after a couple of hours, coastal nucleation mode particles can reach significant sizes where they can contribution to the regional aerosol loading.

Overview of the international project on biogenic aerosol formation in the boreal forest Overview of the international project on biogenic aerosol formation in the boreal forest

Date added: 07/31/2001
Date modified: 07/22/2009
Filesize: 727.68 kB

Kulmala, M., K. Hämeri, P.P. Aalto, J.M. Makela, L. Pirjola, E.D. Nilsson, G. Buzorius, U. Rannik, M. Dal Maso, W. Seidl, T. Hoffmann, R. Janson, H-C. Hansson, Y. Viisanen, and A. Laaksonen, C.D. O'Dowd, Overview of the international project on biogenic aerosol formation in the boreal forest (BIOFOR), Tellus B, 324-343, 2001.


Abstract


Aerosol formation and subsequent particle growth in ambient air have been frequently observed at a boreal forest site (SMEAR II station) in Southern Finland. The EU funded project BIOFOR (Biogenic aerosol formation in the boreal forest has focused on: (a) determination of formation mechanisms of aerosol particles in the boreal forest site; (b) verification of emissions of secondary organic aerosols from the boreal forest site; and (c) quantification of the amount of condensable vapours produced in photochemical reactions of biogenic volatile organic compounds (BVOC) leading to aerosol formation. The approach of the project was to combine the continuous measurements with a number of intensive field studies. These field studies were organised in three periods, two of which were during the most intense particle production season and one during a non-event season. Although the exact formation route for 3 nm particles remains unclear, the results can be summarised as follows: Nucleation was always connected to Arctic or Polar air advecting over the site giving conditions for a stable nocturnal boundary layer followed by a rapid formation and growth of a turbulent convective mixed layer closely followed by formation of new particles. The nucleation seems to occur in the mixed layer or entrainment zone. However two more prerequisites seem to be necessary. A certain threshold of high enough sulphuric acid and ammonia concentrations is probably needed as the number of newly formed particles Was correlated with the product of the sulphuric acid production and the ammonia concentrations No such correlation was found with the oxidation products of terpenes. The condensation sink, i.e., effective particle area, is probably of importance as no nucleation was observed at high values of the condensation sink. From measurement of the hygroscopic properties of the nucleation particles it was found that inorganic compounds and hygroscopic organic compounds contributed both to the particle growth during daytime while at night time organic compounds dominated. Emissions rates for several gaseous compounds was determined. Using four independent ways to estimate the amount of the condensable vapour needed for observed growth of aerosol particles we get an estimate of 2-10 × 107 vapour molecules cm-3. The estimations for source rate give 7.5-11 x 104 cm-3 s-1. These results lead to the following conclusions: The most probable formation mechanism is ternary nucleation (water-sulphuric acid-ammonia). After nucleation, growth into observable sizes (≥3 nm) is required before new particles appear. The major part of this growth is probably due to condensation of organic vapours. However, there is lack of direct proof of this phenomenon because the composition of 1-5 nm size particles is extremely difficult to determine using the present state-of-art instrumentation.

Modelling the Contribution of Passive Smoking to Exposure to PM10 in UK Homes Modelling the Contribution of Passive Smoking to Exposure to PM10 in UK Homes

Date added: 07/31/2001
Date modified: 07/03/2009
Filesize: 426.21 kB

Dimitroulopoulou, C., Ashmore, M.R., and M.A. Byrne 2001. Modelling the contribution of passive smoking to exposure to PM10 in UK homes. Indoor and Built Environment, 10, 209-213, 2001.


Abstract

 

A physical compartmental model (INTAIR) has been parameterised to estimate P 1M0 concentrations and has been used to assess the contribution of smoking to P1M0 levels for typical homes in the UK. The results suggest that smoking activity at home increases the daily mean concentrations in the living room by 1-1.5 &- mu;3g.m per cigarette smoked, and may contribute significantly to personal exposures to PM10 The model simulations demonstrate that the contribution of smoking to daily mean concentrations is highly dependent on the air exchange rate between the room and outdoors.

Concurrent measurements of OH and ultra-fine particles in the coastal atmosphere Concurrent measurements of OH and ultra-fine particles in the coastal atmosphere

Date added: 08/05/1998
Date modified: 07/27/2009
Filesize: 144.75 kB
O'Dowd, C.D., D.J. Creasey, M. Geever, G. McFiggans, D.E. Heard, J.D. Lee, M.J. Pilling, B.J. Whitaker, M.H. Smith, and S.G. Jennings, Concurrent measurements of OH and ultra-fine particles in the coastal atmosphere, J. Aerosol Sci., 29, s611-s612, 1998, (Ser. No. ACP051).

Abstract

 

Factors controlling the nucleation of new aerosol particles in the background atmosphere not easily discernible due to the difficulties associated with measuring aerosol precursors leading to aerosol nucleation along with difficulties in determining new particle chemical composition. It is generally assumed that the primary aerosol precursors species are sulphuric acid and water, although other species such as ammonia and organics have also been implicated. Sulphuric acid is produced in the gas phase via the oxidation of SO2 by the OH radical. Further, OH is likely to also be involved in the oxidation of other precursor species leading to homogeneous heteromolecular nucleation. Simultaneous measurements of OH and ultrafine particles were measured at Mace Head during a campaign in May, 1997. The relationship between the occurrence of ultra-fine particles and the concentration of the OH radical is explored. Aerosol measurements were conducted using three condensation nucleus counters: TSI 3025 (r>1.5 nm); TSI 3022 (r>35nm) and TSI 3010 (r>5nm). Deployment of these three instruments allows determination of ultrafine aerosol concentration by examination of the

difference between the three concentrations. The particle counters were configured for 5Hz sampling in single particle mode and thus, the 3022 and 3010 are off scale at concentrations in excess of 10,000 cm-3 while the 3025 is off scale at 160,OOOcm”. It should be noted that at these concentrations, the condensation particle counters are not quantitatively accurate and can only be interpreted as qualitative. OH measurements were undertaken using the recently developed FAGE technique (Creusey et al, 1997). One typical example of coastal nucleation in anthropogenically influenced air at Mace Head is illustrated in Figure 1. Nucleation events are observed under low tide conditions during daytime. On Julian Day 144, massive concentrations of ultrafine particles are seen at midday and during low tide. Particle concentrations exceeded 150,000 cmm3 and occur shortly after the peak in OH concentration. It is interesting that there are two ultrafine particle peaks which coincide with two OH peaks suggesting that the production of new particles is related to availability of the OH radical. O’Dowd et al. (1998) have shown that nucleation occurs in clean air most days at Mace Head and that these nucleation events relate to low tide events. The measurements presented for this campaign also show that nucleation occurs most days under anthropogenically influenced conditions and that these events require low tide and solar irradiation in order to occur. Thus, it appears that under low tide conditions, there is a sufficient source of aerosol precursor material to promote nucleation. However, it is not clear why, on some days when low tide and solar irradiation occur, nucleation does not always occur. The case presented here suggests that when OH concentrations are drastically reduced, aerosol nucleation no longer proceeds suggesting that the oxidation of aerosol precursors by OH is required for nucleation in this environment.


Deposition in ionic Diffussion Deposition in ionic Diffussion

Date added: 08/07/1968
Date modified: 07/27/2009
Filesize: 1.69 MB

TC OConnor, F Anderson, PJ Nolan, Electrostatic Deposition in ionic Diffussion ,Proceeding of the Royal Irish Academy 1968, Volume 66 Section A No. 5


Abstract

 

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

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

Small particle concentration fluctuations at a coastal site Small particle concentration fluctuations at a coastal site

Date added: 08/01/2002
Date modified: 07/23/2009
Filesize: 877.43 kB
Vana, M., Jennings, S.G., Kleefeld, C., Mirme, A., and Tamm, E., 2002. Small particle concentration fluctuations at a coastal site, Atmos. Res., 63, pp. 247 – 269.

Abstract


Aerosol size spectra (d=10 nm–10 μm) were measured with an electrical aerosol spectrometer (EAS) at Mace Head on the west coast of Ireland. Several small aerosol particle (diameter 10–32 nm) concentration bursts were observed during the measurement period. Relationships between the events, air mass trajectories, tide height, and meteorological parameters are examined. Series of bursts were observed when a spectral transformation due to subsequent particle growth from 10 to 56–100 nm can be identified in an Eulerian experiment. Particle growth rates of between 1 and 3 nm/h were determined. These bursts appear in cold and comparatively clean arctic or polar air masses with temperature and relative humidity fluctuations, and do not correlate with low tide in some cases. These episodes, similar to those frequently found in the continental boundary layer, are thought to occur over a wide area and, for clear detection, require stable airflow for a few days. Elevated small-particle concentration events are more common during low tide or shortly after, and are typically associated with low wind speeds. Here, the increased shore exposure during low tide is thought to influence the nucleation and the subsequent growth of these aerosol particles. The occurrences of the bursts are found to depend on local wind direction. The highest d=10–32 nm particle concentrations appeared for wind sectors furthest from the tidal regions when the wind direction was 150–160°(south-easterly). Most of the events occurred during daytime when solar irradiation is most intense.

Dual pathways for atmospheric sulfuric acid-water nucleation mechanisms Dual pathways for atmospheric sulfuric acid-water nucleation mechanisms

Date added: 04/08/2009
Date modified: 11/01/2009
Filesize: 988.72 kB
Laaksonen, A.,  M. Kulmala, T. Berndt, F. Stratmann, S. Mikkonen, A. Ruuskanen, K.E.J. Lehtinen, M. Dal Maso, P. Aalto, T. Petäjä, I. Riipinen, R. Janson, F. Arnold, M. Hanke, J.Ücker, B. Umann, K. Sellegri,  C.D. O’Dowd, Y. Viisanen, Dual pathways for atmospheric sulfuric acid-water nucleation mechanisms,, Atmos. Chem. Phys.,  8, 7255–7264, 2008.

Abstract


Atmospheric new particle formation is generally thought to occur due to homogeneous or ion-induced nucleation of sulphuric acid. We compare ambient nucleation rates with laboratory data from nucleation experiments involving either sulphuric acid or oxidized SO2. Atmospheric nucleation occurs at H2SO4 concentrations 2–4 orders of magnitude lower than binary or ternary nucleation rates of H2SO4 produced from a liquid reservoir, and atmospheric H2SO4 concentrations are very well replicated in the SO2 oxidation experiments. We hypothesize these features to be due to the formation of free HSO5 radicals in pace with H2SO4 during the SO2 oxidation. We suggest that at temperatures above 250K these radicals produce nuclei of new aerosols much more efficiently than H2SO4. These nuclei are activated to further growth by H2SO4 and possibly other trace species. However, at lower temperatures the atmospheric relative acidity is high enough for the H2SO4–H2O nucleation to dominate.

Aerosol and trace gas measurements during the mace head experiment Aerosol and trace gas measurements during the mace head experiment

Date added: 07/31/1996
Date modified: 07/27/2009
Filesize: 999.68 kB

McGovern, F.M., Jennings, S.G., O'Connor, T.C., and Simmonds, P.G. (1996) - Aerosol and trace gas measurements during the Mace Head experiment. Atmos. Environ., 30, 3891 - 3902.


Abstract


Measurements obtained between the 9th and 23rd of April 1991 at the Mace Head remote maritime station are presented. These measurements were obtained as part of a EUROTRAC Air Sea Exchange intensive measurement campaign. Analysis of variations in the aerosol and trace concentrations is based on inter-comparison of the measured species and use of local meteorological data and back trajectories for the period. While air masses of principally maritime origin were encountered throughout the campaign, typical background maritime conditions only occurred during short periods. Other periods were highly modified by mainly local influences which included local biomass burning and Aitken nuclei(AN) production. The biomass burning was observed to contribute to elevated accumulation mode aerosol (0.1-1.0 μm), black carbon mass concentration, CO, and CH4 levels. The O3 concentrations were variable throughout the measurement period. Reasonable correlations were found between the trace gas data except between O3 and CO during the period influenced by biomass burning when the O3 levels were generally depleted. Very high AN concentrations (> 20,000cm-3) were measured on a number of sampling days, with a distinct dawn effect being observed. The very high AN concentrations occurred during otherwise clean air conditions and also in the presence of combustion aerosols and are principally attributed to photochemical gas-to-particle conversion processes. The conditions under which these events occurred and variations in background conditions are examined.

Aerosol light absorption in the North Atlantic trends and seasonal characteristic during the period 1989 to 2003 Aerosol light absorption in the North Atlantic trends and seasonal characteristic during the period 1989 to 2003

Date added: 08/01/2006
Date modified: 07/27/2009
Filesize: 547.6 kB

Junker, C., Jennings, S. G., and Cachier, H.: Aerosol light absorption in the North Atlantic: trends and seasonal characteristics during the period 1989 to 2003, Atmos. Chem. Phys., 6, 1913-1925, 2006


Abstract


Aerosol light attenuation on quartz fibre filters has been measured since February 1989 at the Mace Head Atmospheric Research station near Carna, Co. Galway, Ireland, using an Aethalometer.

The frequency of occurrence of the hourly averaged aerosol absorption data is found to be bimodally distributed. The two modes result from clean marine air and anthropogenically polluted continental air both being advected to the station dependent on the prevailing wind direction. The hourly averages of the marine portion of the aerosol light absorption are found to follow closely a lognormal distribution with a geometric mean of 0.310 Mm-1. The hourly averages of continental sector aerosol absorption are neither normally nor lognormally distributed and have an arithmetic mean of 6.36 Mm-1, indicating the presence of anthropogenic sources for BC east of the Mace Head station.

The time series of the monthly averaged attenuation coefficient σatt of both marine and continental sector aerosol shows an increase from 1989 to 1997 and a levelling off thereafter.

The monthly maximum of marine sector σatt is found in May. Trend and seasonal characteristics of the clean marine aerosol attenuation coefficients observed at Mace Head appear to be driven by meteorological factors, as indicated by rainfall data and by trends in the North Atlantic Oscillation (NAO) indices. The observed increasing trends of the continental sector σatt from 1989 up to 1997 are possibly related to changes in BC emissions over Ireland, calculated from UNSTAT (2002) fuel consumption data.

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.

Impact of halogen monoxide chemistry upon boundary layer OH and HO 2 concentrations at a coasta Impact of halogen monoxide chemistry upon boundary layer OH and HO 2 concentrations at a coasta

Date added: 08/06/2005
Date modified: 07/24/2009
Filesize: 187.73 kB

Bloss, W. J.; Lee, J. D.; Johnson, G. P.; Sommariva, R.; Heard, D. E.; Saiz-Lopez, A.; Plane, J. M. C.; McFiggans, G.; Coe, H.; Flynn, M.; Williams, P.; Rickard, A. R.; Fleming, Z. L. Impact of halogen monoxide chemistry upon boundary layer OH and HO2 concentrations at a coastal site Geophys. Res. Lett., Vol. 32, No. 6, L06814 10.1029/2004GL022084


Abstract


The impact of iodine oxide chemistry upon OH and HO2 concentrations in the coastal marine boundary layer has been evaluated using data from the NAMBLEX (North Atlantic Marine Boundary Layer Experiment) campaign, conducted at Mace Head, Ireland during the summer of 2002. Observationally constrained calculations show that under low NOx conditions experienced during NAMBLEX (NO ≤ 50 pptv), the reaction IO + HO2 → HOI + O2 accounted for up to 40% of the total HO2 radical sink, and the subsequent photolysis of HOI to form OH + I comprised up to 15% of the total midday OH production rate. The XO + HO2 (X = Br, I) reactions may in part account for model overestimates of measured HO2 concentrations in previous studies at Mace Head, and should be considered in model studies of HOx chemistry at similar coastal locations.

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

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

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


Abstract


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

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

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

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


Abstract


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

.

Observations of high concentrations of I2 and IO in coastal air Observations of high concentrations of I2 and IO in coastal air

Date added: 03/03/2010
Date modified: 03/03/2010
Filesize: 299.46 kB

Huang, R.-J., K. Seitz, T. Neary, C. D. O’Dowd, U. Platt, and T. Hoffmann, Observations of high concentrations of I2 and IO in coastal air supporting iodine-oxide driven coastal new particle formation . Geophys. Res. Letts, VOL. 37, L03803, doi:10.1029/2009GL041467, 2010


Abstract.

 Theoretical studies have predicted that concentrations of gaseous I2 and IO of the order of 80–100 ppt and 40–50 ppt, respectively, are required in coastal air to account for photochemically-driven coastal new-particle formation events to occur. However, measurements reported to date  (i.e., 20 ppt I2,  10 ppt IO) have not supported the required model predictions. Here, we present measurements of high concentrations of I2 and IO n N.E. Atlantic marine air on the west coast of Ireland. The maximum mixing ratios of daytime I2 and IO over the seaweed beds during low tide were 302 ppt and 35 ppt, respectively. The I2 distribution=was rather inhomogeneous, even at the inter-tidal zone, but closely related to the macroalgae biomass  bundance. New particle formation bursts were frequently observed during daytime hours with the concentrations up to 4.5  105 particles cm3 during low-tide conditions, and the concentrations of ultra-fine particles were positively correlated with the IO concentrations. Considering the constraints set out in theoretical studies for new particle formation via condensation of condensable iodine oxide vapours, the results reported here clearly demonstrate that the molecular iodine and iodine monoxide concentrations in coastal air are sufficient to meet the theoretical precursor concentrations required to drive intensive coastal newparticle formation from higher order condensable iodine oxides.

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

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

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


Abstract


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

 

Mace Head Atmospheric Research Station IGActivities Mace Head Atmospheric Research Station IGActivities

Date added: 07/31/1999
Date modified: 07/24/2009
Filesize: 59.08 kB
Jennings, S.G., 1999. Mace Head Atmospheric Research Station. IGACtivities, No. 18, 14-17.

Abstract

 


Mass absorption Coefficient of natural Aerosol Particles in the 0.4 - 2.4um Wavelength Interval.. Mass absorption Coefficient of natural Aerosol Particles in the 0.4 - 2.4um Wavelength Interval..

Date added: 08/26/1973
Date modified: 07/22/2009
Filesize: 8.15 MB
K. Fischer, "Bestimmung der Absorption von sichtbarer Strahlung durch Aerosolpartikeln," Contrib. Atmos. Phys. 43, 244 (1970); "Mass Absorption Coefficient of Natural Aerosol Particles in the 0.4–2.4 µm Wavelength Interval," Contrib. Atmos. Phys. 46, 89 (1973), "Mass Absorption Indices of Various Types of Natural Aerosol Particles in the Infrared," Appl. Opt. 14, 2851 (1975).

Abstract

 

Theoretical investigation have predicted that absorption of solar radiation by particulate matter- suspended as aerosol particles in the air - plays an important part in the radiation budget of the atmosphere.

In the present study the mass absorption coeffiecnet K/P (i.e. the imaginary part of the refractive index related to density) is determined for the 0.4 - 2.4 um wavelength intercal wavelength interval. The measuremetn are performed on films of aerosol particles which were collected by an automatic jet impactor at several urban and remote sites.

EUCAARI ion spectrometer measurements at 12 European sites – analysis of new-particle formation even EUCAARI ion spectrometer measurements at 12 European sites – analysis of new-particle formation even

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 2.55 MB

Manninen, H. E, .T. Nieminen, E. Asmi, S. Gagné, S. Häkkinen, K. Lehtipalo, P. Aalto, M. Vana, A. Mirme, S. Mirme, U. Hõrrak, C. Plass-Dülmer, G. Stange, G. Kiss, A. Hoffer, N. Tör\H{o}, M. Moerman, B. Henzing, G. de Leeuw, M. Brinkenberg, G. N. Kouvarakis, A. Bougiatioti, N. Mihalopoulos, C. O'Dowd, D. Ceburnis, A. Arneth, B. Svenningsson, E. Swietlicki, L. Tarozzi, S. Decesari, M. C. Facchini, W. Birmili, A. Sonntag, A. Wiedensohler, J. Boulon, K. Sellegri, P. Laj, M. Gysel, N. Bukowiecki, E. Weingartner, G. Wehrle, A. Laaksonen, A. Hamed, J. Joutsensaari, T. Petäjä, V.-M. Kerminen, and M. Kulmala, EUCAARI ion spectrometer measurements at 12 European sites – analysis of new-particle formation events,
Atmos. Chem. Phys., 10, 7907–7927, doi:10.5194/acp-10-7907-2010, 2010


  

We present comprehensive results on continuous atmospheric cluster and particle measurements in the size range 

1–42 nm within the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) project. We focused on characterizing the spatial and temporal variation of new particle formation events and relevant particle formation parameters across Europe. Different types of air ion and cluster mobility spectrometers were deployed at 12 field sites across Europe from March 2008 to May 2009. The measurements were conducted in a wide variety of environments, including coastal and continental locations as well as sites at different altitudes (both in the boundary layer and the free troposphere). New particle formation events were detected at all of the 12 field sites during the year-long measurement period. From the data, nucleation and growth rates of newly formed particles were determined for each environment. In a case of parallel ion and neutral cluster measurements, we could also estimate the relative contribution of ion-induced and neutral nucleation to  the total particle formation. The formation rates of charged particles at 2 nm accounted for 1–30% of the corresponding total particle formation rates. As a significant new result, we found out that the total particle formation rate varied much more between the different sites than the formation rate of charged particles. This work presents, so far, the most comprehensive effort to experimentally characterize nucleation and growth of atmospheric molecular clusters and nanoparticles at ground-based observation sites on a continental scale.

On The Occurrence of Open Ocean Particle Production Events On The Occurrence of Open Ocean Particle Production Events

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 603.03 kB

O’Dowd, C.D, C. Monahan and M. Dall’Osto, On The Occurrence of Open Ocean Particle Production Events, Geophys. Res. Letts., 37, L19805, doi:10.1029/2010GL044679,  2010.


We present new results from the Mace Head coastal station illustrating that open ocean new particle production and growth events occur frequently during periods of high oceanic productivity over the N.E. Atlantic. For the first time, we report events during which a recently 

formed nucleation mode (15 nm diameter) is detected and is observed to grow into an Aitken mode (50 nm diameter) over periods up to 48 hours. A growth rate of 0.8 nm hour1 is estimated in a typical case study, pointing to a source region 700 km offshore. The duration of the growth also suggests the particle production events are occurring over large spatial scales. Analysis of seven yearsof data show occurrence of extended growth events (lasting at least 24 hours) from March to September, with a peak occurrence in May. The events suggest that secondary marine boundary layer aerosol formation contributes to the marine aerosol population.

Particle mobility size spectrometers: harmonization of technical standards and data structure to fac Particle mobility size spectrometers: harmonization of technical standards and data structure to fac

Date added: 02/15/2011
Date modified: 02/15/2011
Filesize: 2.08 MB

Wiedensohler, A., Birmili, W., Nowak, A., Sonntag, A., Weinhold, K., Merkel, M., Wehner, B., Tuch, T., Pfeifer, S., Fiebig, M., Fjäraa, A. M., Asmi, E., Sellegri, K., Depuy, R., Venzac, H., Villani, P., Laj, P., Aalto, P., Ogren, J. A., Swietlicki, E., Roldin, P., Williams, P., Quincey, P., Hüglin, C., Fierz-Schmidhauser, R., Gysel, M., Weingartner, E., Riccobono, F., Santos, S., Grüning, C., Faloon, K., Beddows, D., Harrison, R. M., Monahan, C., Jennings, S. G., O'Dowd, C. D., Marinoni, A., Horn, H.-G., Keck, L., Jiang, J., Scheckman, J., McMurry, P. H., Deng, Z., Zhao, C. S., Moerman, M., Henzing, B., and de Leeuw, G.: Particle mobility size spectrometers: harmonization of technical standards and data structure to facilitate high quality long-term observations of atmospheric particle number size distributions, Atmos. Meas. Tech. Discuss., 3, 5521-5587, doi:10.5194/amtd-3-5521-2010, 2010.


Particle mobility size spectrometers often referred to as DMPS (Differential Mobility Particle Sizers) or SMPS (Scanning Mobility Particle Sizers) have found a wide application in atmospheric aerosol research. However, comparability of measurements conducted world-wide is hampered by lack of generally accepted technical standards with respect to the instrumental set-up, measurement mode, data evaluation as well as quality control. This article results from several instrument intercomparison workshops conducted within the European infrastructure project EUSAAR (European Supersites for Atmospheric Aerosol Research). Under controlled laboratory conditions, the number size distribution from 20 to 200 nm determined by mobility size spectrometers of different design are within an uncertainty range of ±10% after correcting internal particle losses, while below and above this size range the discrepancies increased. Instruments with identical design agreed within ±3% in the peak number concentration when all settings were done carefully. Technical standards were developed for a minimum requirement of mobility size spectrometry for atmospheric aerosol measurements. Technical recommendations are given for atmospheric measurements including continuous monitoring of flow rates, temperature, pressure, and relative humidity for the sheath and sample air in the differential mobility analyser. In cooperation with EMEP (European Monitoring and Evaluation Program), a new uniform data structure was introduced for saving and disseminating the data within EMEP. This structure contains three levels: raw data, processed data, and final particle size distributions. Importantly, we recommend reporting raw measurements including all relevant instrument parameters as well as a complete documentation on all data transformation and correction steps. These technical and data structure standards aim to enhance the quality of long-term size distribution measurements, their comparability between different networks and sites, and their transparency and traceability back to raw data.


 


 

Aerosol particle size distribution in the 0.25-5.0 micron radius range in Northern England Aerosol particle size distribution in the 0.25-5.0 micron radius range in Northern England

Date added: 07/30/1977
Date modified: 06/30/2009
Filesize: 1.3 MB

Jennings, S.G., and Elleson, R.K. (1977)- Aerosol size distributions in the 0.25 to 5 micrometre radius range. Atmos. Environ., 11, 361-366.


Abstract


An analysis has been made of continuous measurements on the particle size distribution of the atmospheric aerosol in five particle radius categories between 0.25 and 5.0 μm. An automatic Royco model 225 optical particle counter together with a digital line printer was used to obtain the measurements at a 10 min sampling frequency from 21 July to 8 September 1975 at Durham Observatory, 2 km SSW of Durham City in the North East of England. Measurements were also taken every 10 min from 15 December to 6 January 1976 on the summit of Great Dun Fell, 842 msl, on the Northern Pennine Range, England.

Diurnal variation associated with the particle number concentration shows maximum concentration from about 02:00–08:00 h BST and a minimum over the period 14:00–20:00 h BST.

The particle size distribution for both the Durham and Great Dun Fell site follows the shape of a Junge log-radius type distribution with slopes β equal to 3.04 and 2.74 respectively. The distributions show that the number concentration over the five radius intervals is an order of magnitude lower at the mountain site of Great Dun Fell than at Durham Observatory.

An analysis of the sampling frequency of particle concentrations showed that the measurements could be made less frequently by factors up to 20, without loss of accurate information.

Photochemical ozone formation in north west Europe and its control Photochemical ozone formation in north west Europe and its control

Date added: 08/07/2003
Date modified: 07/23/2009
Filesize: 635.36 kB

DERWENT, R.G., Jenkin, M.E., Saunders, S.M., Pilling, M.J., Simmonds, P.G., Passant, N.R., Dollard, G.J., Dumitrean, P. and Kent, A., 2003: Photochemical ozone formation in north west Europe and its control. Atmos Environ, 37, 1,983-1,991.


Abstract


A photochemical trajectory model together with a Master Chemical Mechanism and a highly speciated emission inventory for organic compounds have been used to describe the formation of ozone in north west Europe and to identify the most prolific ozone-forming organic compounds. Observations are reviewed to assess the impact of emission controls on their urban volatile organic compound (VOC) concentration trends with time. The observed trends are then used to deduce the likely trends in episodic peak ozone concentrations and to compare them with observed trends in peak ozone concentrations. It is concluded that it is likely that motor vehicle emission controls have brought about a substantial reduction in episodic peak ozone concentrations in north west Europe during the 1990s.

 

SimulatingMarine New Particle Formation and Growth Using theM7Modal Aerosol DynamicsModal SimulatingMarine New Particle Formation and Growth Using theM7Modal Aerosol DynamicsModal

Date added: 01/30/2011
Date modified: 01/31/2011
Filesize: 1.28 MB

Monahan, C., H. Vuollekoski, M. Kulmala, C. O’Dowd. Modelling the Contribution of Iodine Oxide to Marine New Particle Formation, Adv. in Meteorol., Article ID 482603, doi:10.1155/2010/482603, 2010.


A modal atmospheric aerosol model (M7) is evaluated in terms of predicting marine new particle formation and growth. Simulations were carried out for three different nucleation schemes involving (1) kinetic self-nucleation of OIO (2) nucleation via OIO activation by H2SO4 and (3) nucleation via OIO activation by H2SO4 plus condensation of a low-volatility organic vapour. Peak OIO and H2SO4 vapour concentrations were both limited to 6 × 106 molecules cm−3 at noontime while the peak organic vapour concentration was limited to 12×106 molecules cm−3. All simulations produced significant concentrations of new particles in the Aitken mode. From a base case particle concentration of 222 cm−3 at radii >15 nm, increases in concentrations to 366 cm−3 were predicted fromthe OIO-OIO case, 722 cm−3 for the OIO-H2SO4 case, and 1584 cm−3 for the OIO-H2SO4 case with additional condensing organic vapours. The results indicate that open ocean new particle production is feasible for clean conditions; however, new particle production becomes most significant when an additional condensable organic vapour is available to grow the newly formed particles to larger sizes. Comparison to sectional model for a typical case study demonstrated good agreement and the validity of using the modal model.

The effect of particle size distribution and complex index of refraction of atmospheric aerosols... The effect of particle size distribution and complex index of refraction of atmospheric aerosols...

Date added: 08/01/1981
Date modified: 07/10/2009
Filesize: 1.44 MB
Jennings, S.G. (1981)- The effect of particle size distribution and complex index of refraction of atmospheric aerosols in the visual range. Proc. of the Ninth International Conference in Atmospheric Aerosol, Condensation and Ice Nuclei, Galway University Press, 415 - 420.

Abstract

 

A comprehensive study has been made of the effect of particle size distribution and complex index of refraction on the visual range, with a wavelengrth lamada of 0.55 micrometres. Calculations were performed by using a generalized polydisperse Mie scattering theory, which makes the assumption that the particles are spherical. Several workers have shown that a lognormal distribution can well represent different types of atmospheric aerosol over a wide range of natural conditions. A lognormal distribution wth geometric mean radius rg varying from 0.005 to 10 micrometers and geometric standard deviation sigmag varying from 1.5 up to 3.0 was used in the calculations.

 


 

The composition of nucleation and Aitken modes particles during coastal nucleation events evidence f The composition of nucleation and Aitken modes particles during coastal nucleation events evidence f

Date added: 08/01/2006
Date modified: 07/07/2009
Filesize: 3.14 MB

Vaattovaara, P., P. E. Huttunen, Y. J. Yoon, J. Joutsensaari, K. E. J. Lehtinen, C. D. O’Dowd, and A. Laaksonen,The composition of nucleation and Aitken modes particles during coastal nucleation events: evidence for marine secondary organic contribution, Atmos. Chem. Phys. Discuss., 6, 3337–3379, 2006.


Abstract


Newly-formed nanometer-sized particles have been observed at coastal and marine environments worldwide. Interestingly, organic species have so far not been detected in those newly-formed nucleation mode particles. In this study, we applied the UFO-TDMA (ultrafine organic tandem differential mobility analyzer) method to study the possible existence of an organic fraction in recently formed coastal nucleation mode particles (d<20 nm) at the Mace Head research station. Furthermore, effects of those nucleation events to potential CCN (cloud condensation nuclei) were studied. The coastal events were typical for the Mace Head region and they occurred at low tide conditions during efficient solar radiation and high biological activity (HBA, i.e. a high mass concentration of chlorophyll a of the ocean) in spring 2002. Additionally, a PHA-UCPC (pulse height analyzer ultrafine condensation particle counter) technique was used to study the composition of newly-formed particles formed in low tide conditions during a lower biological activity (LBA, i.e. a lower mass concentration of chlorophyll a of the ocean) in October 2002. The overall results of the UFO-TDMA and the PHA-UCPC measurements indicate that those coastally/marinely formed nucleation mode particles include a remarkable fraction of secondary organic products, beside iodine oxides, which are likely to be responsible for the nucleation. During clean marine air mass conditions, the origin of those secondary organic oxidation compounds can be related to marine/coastal biota and thus a major fraction of the organics may originate from biosynthetic production of alkenes such as isoprene and their oxidation by iodine, hydroxyl radical, and ozone. During modified marine conditions, also anthropogenic secondary organic compounds may contribute to the nucleation mode organic mass, in addition to biogenic secondary organic compounds. Thus, the UFO-TDMA results suggest that the secondary organic compounds may, in addition to being significant contributors to the nucleation mode processes, accelerate the growth of freshly nucleated particles and increase their survival probability to CCN and even larger radiatively active particle sizes. The results give new insights to the coastal/marine particle formation, growth, and properties. The marine biota driven secondary organic contributions to coastal/marine particle formation and composition can be anticipated in other species specific biologically active oceans and fresh-waters areas around the world and thus, they may be significant also to the global radiative bugdet, atmosphere-biosphere feedbacks, and climate change.

Coastal new particle formation Environmental conditions and aerosol physico-chemical characteristics during nucleation bursts Coastal new particle formation Environmental conditions and aerosol physico-chemical characteristics during nucleation bursts

Date added: 07/31/2002
Date modified: 07/27/2009
Filesize: 1.31 MB
Colin D. O'Dowd, Kaarle Hämeri, Jyrki Mäkelä, Minna Väkeva, Pasi Aalto, Gerrit de Leeuw, Gerard Kunz, Harald Berresheim, Hans-Christen Hansson, Edo Becker, Andrew G. Allen, Roy M. Harrion, Christoph Kleefeld, Michael Geever, S. Gerard Jennings, Harald Berresheim, and Markku Kulmala.Coastal new particle formation: Environmental conditions and aerosol physico-chemical characteristics during nucleation bursts. J. Geophys. Res. 107, 10.1029/2000JD000206, 2002.

Abstract


Nucleation mode aerosol was characterized during coastal nucleation events at Mace Head during intensive New Particle Formation and Fate in the Coastal Environment (PARFORCE) field campaigns in September 1998 and June 1999. Nucleation events were observed almost on a daily basis during the occurrence of low tide and solar irradiation. In September 1998, average nucleation mode particle concentrations were 8600 cm−3 during clean air events and 2200 cm−3 during polluted events. By comparison, during June 1999, mean nucleation mode concentrations were 27,000 cm−3 during clean events and 3350 cm−3 during polluted conditions. Peak concentrations often reached 500,000–1,000,000 cm−3 during the most intense events and the duration of the events ranged from 2 to 8 hours with a mean of 4.5 hours. Source rates for detectable particle sizes (d > 3 nm) were estimated to be between 104 and 106 cm−3 s−1 and initial growth rates of new particles were as high as 0.1–0.35 nm s−1 at the tidal source region. Recently formed 8 nm particles were subjected to hygroscopic growth and were found to have a growth factor of 1.0–1.1 for humidification at 90% relative humidity. The low growth factors implicate a condensable gas with very low solubility leading to detectable particle formation. It is not clear if this condensable gas also leads to homogeneous nucleation; however, measured sulphuric acid and ammonia concentration suggest that ternary nucleation of thermodynamically stable sulphate clusters is still likely to occur. In clear air, significant particle production (>105 cm−3) was observed with sulphuric acid gas-phase concentration as low as 2 × 106 molecules cm−3 and under polluted conditions as high as 1.2 × 108 molecules cm−3.

Aerosol distribution over Europe a model evaluation study with Aerosol distribution over Europe a model evaluation study with

Date added: 08/01/2008
Date modified: 07/27/2009
Filesize: 1.41 MB

Langmann, B. Varghese, E. Marmer, E. Vignati, J. Wilson, P. Stier and C. O’Dowd, Aerosol distribution over Europe: A model evaluation study with detailed aerosol microphysics, Atmos. Chem. Phys., in press, 2008.


Abstract


This paper summarizes an evaluation of model simulations with a regional scale atmospheric climate-chemistry/aerosol model called REMOTE, which has been extended by a microphysical aerosol module. Model results over Europe are presented and compared with available measurements in surface air focusing on the European distribution and variability of primary and secondary aerosols. Additionally, model results obtained with detailed aerosol microphysics are compared to those based on an aerosol bulk mass approach revealing the impact of dry deposition fluxes on atmospheric burden concentration. An improved determination of elevated ozone and sulfate concentrations could be achieved by considering a diurnal cycle in the anthropogenic emission fluxes. Deviation between modelled and measured organic carbon concentrations can be mainly explained by missing formation of secondary organic aerosols and deficiencies in emission data. Changing residential heating practices in Europe, where the use of wood is no longer restricted to rural areas, need to be considered in emission inventories as well as vegetation fire emissions which present a dominant source of organic carbon.

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

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

Abstract


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

Non-Methane hydrocarbon measurements in Ireland Non-Methane hydrocarbon measurements in Ireland

Date added: 08/06/2003
Date modified: 07/27/2009
Filesize: 32.07 kB
Noone, C A.Non-methane hydrocarbon measurements in Ireland [EGU04-A-05179].

Abstract

 

The measurement of non-methane hydrocarbons (NMHCs) has become increasingly important in recent years in light of their role as precursors in the formation of ozone and their potential impact on human health. In this poster, observations of diurnal and seasonal cycles of NMHCs (C$_2$-C$_8$) are reported for measurements observed at Mace Head, Ireland from 2002-2003. The remote coastal research station of Mace Head, Co. Galway is unique in Europe offering an opportunity to study the Northern Hemispheric background atmosphere, as well as emissions from Europe. Continuous ground-based data collected at Mace Head allows air mass characterisation and model estimates of ozone production with polluted
plumes to be made.

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

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

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


Abstract

Advances in characterization of size resolved organic matter in marine aerosol over the North Atlantic Advances in characterization of size resolved organic matter in marine aerosol over the North Atlantic

Date added: 08/01/2004
Date modified: 07/27/2009
Filesize: 552.34 kB
Cavalli,F., M.C. Facchini, S. Decesari, M. Mircea, L. Emblico, S. Fuzzi, D. Ceburnis, Y.J. Yoon and C.D. O’Dowd, J.-P. Putaud and A. Dell’Acqua, Advances in characterization of size resolved organic matter in marine aerosol over the North Atlantic, J. Geophys. Res, doi:10.1029/2004JD0051377, 2004.

Abstract


Size-segregated marine aerosols were collected at Mace Head Atmospheric Research Station (Ireland) during spring and autumn 2002 corresponding with the phytoplankton bloom periods in the North Atlantic. Strict control of the sampling, air mass back trajectory analysis, and analysis of pollutant tracers allowed the selection of a set of samples representative of clean marine conditions. A comprehensive chemical characterization of both (1) water-soluble and water-insoluble organic fraction and (2) water-soluble inorganic ions was performed. The selected samples illustrated a consistent picture in terms of chemical composition. The supermicron mode predominantly comprises sea-salt aerosol with a mass concentration of 10.16 ± 0.80 μg m−3, the remainder being non-sea-salt (nss) sulphate, 0.03 ± 0.01 μg m−3, and nitrate, 0.13 ± 0.04 μg m−3. By comparison, the mass of sea salt, nss sulphate, and nitrate in the submicron mode is found to be 0.39 ± 0.08 μg m−3, 0.26 ± 0.04 μg m−3, and 0.02 ± 0.01 μg m−3, respectively. Water-soluble organic carbon (WSOC) is observed in the submicron mode with a mass concentration of 0.25 ± 0.04 μg m−3, comparable to that of nss sulphate, and in the supermicron mode with a mass concentration of 0.17 ± 0.04 μg m−3. The WSOC to total carbon (TC) ratio is found to be 0.20 ± 0.12 for the submicron fraction and 0.29 ± 0.08 for the supermicron fraction, while the black carbon (BC) to TC ratio is, on average, 0.032 ± 0.001 for both aerosol modes. The remaining carbon, water-insoluble organic carbon, contributes 0.66 ± 0.11 μg m−3 and 0.26 ± 0.06 μg m−3 to the submicron and supermicron modes, respectively and, thus, represents the dominant submicron aerosol species. Furthermore, the WSOC chemical composition comprises mainly aliphatic and only partially oxidized species and humic-like substances, resulting in appreciable surface-active properties. The observed organic matter chemical features (size-dependent concentration, hydrophobic nature of a substantial fraction of the organic matter, and low oxidized and surface-active WSOC species) are consistent with the hypothesis of a primary marine source; bubble-bursting processes, occurring at the surface of the North Atlantic Ocean during phytoplankton blooms, effectively transfer organic matter into marine aerosol particles, particularly enriching the fine-aerosol fraction.

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

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

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


Abstract


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

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

Date added: 08/01/2006
Date modified: 07/27/2009
Filesize: 692.21 kB

Reade, K., S.G. Jennings, and G. McSweeney, Cloud condensation nuclei measurements at Mace Head, Ireland, over the period 1994-2002, Atmos. Res., 82, 610-621, 2006.


Abstract


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

The effect of clouds on aerosol growth in the rural atmosphere The effect of clouds on aerosol growth in the rural atmosphere

Date added: 08/06/2000
Date modified: 07/07/2009
Filesize: 206.46 kB

Colin D. O'Dowd, Jason A. Lowe, Michael H. Smith, The effect of clouds on aerosol growth in the rural atmosphere, Atmospheric ResearchVolume 54, Issue 4, , August 2000, Pages 201-221.


Abstract


Measurements of accumulation mode aerosol in the atmospheric boundary layer under cloudy and cloud-free conditions, and in the lower free troposphere under cloud-free conditions, were conducted over the rural northwest of England. Normalised size distributions in the cloud-free boundary layer (CFBL) and the cloud-free free troposphere (CFFT) exhibited almost identical spectral similarities with both size distributions possessing a concentration peak mode-radius of 0.05 μm or less. By comparison, aerosol distributions observed in cloudy air exhibited a distinctive log-normal distribution with mode-radii occurring at 0.1 μm concomitant with a local minimum at 0.05 μm. The consistent and noticeable difference in spectral features observed between cloudy and cloud-free conditions suggest that a greater amount of gas-to-particle conversion occurs on cloudy days, presumably through in-cloud aqueous phase oxidation processes, leading to larger sized accumulation mode particles. Apart from the distinct difference between cloudy and cloud-free aerosol spectra on cloudy days, aerosol concentration and mass were observed to be significantly enhanced above that of the ambient background in the vicinity of clouds. Volatility analysis during one case of cloud processing indicated an increase in the relative contribution of aerosol mass volatile at temperatures characteristic of sulphuric acid, along with a smaller fraction of more volatile material (possibly nitric acid and/or organic aerosol). Growth-law analysis of possible growth mechanisms point to aqueous phase oxidation of aerosol precursors in cloud droplets as being the only feasible mechanism capable of producing the observed growth. The effect of cloud processing is to alter the cloud condensation nuclei (CCN) supersaturation spectrum in a manner which increases the availability of CCN at lower cloud supersaturations.

 

Airborne trace gas measurements over open ocean and coastal regions upwind of Mace Head, Irelan Airborne trace gas measurements over open ocean and coastal regions upwind of Mace Head, Irelan

Date added: 08/06/2003
Date modified: 07/27/2009
Filesize: 13.7 kB

Ruth Purvis, Ally Lewis, Jim McQuaid, "Airborne Trace Gas Measurements Over Open Ocean and Coastal Regions Upwind of Mace Head, Ireland", Geophysical Research Abstracts Volume 5, 2003.


Abstract

 

The spatial distribution of a number of trace species has been determined in marine boundary layer (MBL) and free troposphere (FT) air around the Mace Head Atmospheric Research Station, Ireland. CO and ozone measurements were made onboard NERC Dornier 228-101 research aircraft operated by the Airborne Remote Sensing Facility during the SNAP (Supporting NAMBLEX from an Airborne Platform) campaign in August 2002. High frequency whole air sampling from the aircraft with ground analysis using GC-FID was used for C2 - C6 hydrocarbons mixing ratios. The campaign was conducted in conjunction with the ground based NAMBLEX (North Atlantic Marine Boundary Layer Experiment) campaign carried out at Mace Head. The distribution of trace species was investigated in both coastal regions and above the deep waters beyond the continental shelf. A vertical gradient in concentration of hydrocarbonand sulphur species with known oceanic sources was observed in the MBL over both oceanic regions when compared to anthropogenic tracers such as acetylene and CO. Under clear sky conditions typical maximum mixing ratios were MBL ethene 78 pptV: FT ethene 10 pptV: MBL DMS: 89 pptV: FT DMS 21 pptV. Elevated mixing ratios of species with oceanic origin were observed in the lower most FT in regions experiencing strong convective activity associated with cumulus cells. Vertical profiles centred over the field sit showed good agreement between ground based and airbornehydrocarbon measurements taken within the MBL. The MBL upwind of Mace Head appeared well mixed with respect to both NMHCs, CO and ozone. Above 2 km showed distinct layers with free tropospheric ozone values of 50 ppbV contrasting typical MBL values of less than 30 ppbV. Flights indicate aboundary layer height of approximately 1200 m. The observations confirm that for these species the surface site measurements are generally representative of the marine boundary layer as a whole but not of the air mass above.

A modeling study of iodine chemistry in the marine boundary layer A modeling study of iodine chemistry in the marine boundary layer

Date added: 08/06/2000
Date modified: 07/27/2009
Filesize: 1.4 MB

McFiggans, G., J. M. C. Plane, B. J. Allan, L. J. Carpenter, H. Coe, and C. O'Dowd (2000), A modeling study of iodine chemistry in the marine boundary layer, J. Geophys. Res., 105(D11), 14,371–14,385.


Abstract


An observationally constrained photochemical box model has been developed to investigate the atmospheric chemistry of iodine in the marine boundary layer, motivated by recent measurements of the iodine monoxide (IO) radical (Allan et al., this issue). Good agreement with the time series of IO measured at a midlatitude coastal station was achieved by using a reaction scheme that included recycling of iodine through marine aerosol. The strong diurnal variation in IO observed in the subtropical Atlantic was satisfactorily modeled by assuming a constant concentration of iodocarbons that photolyzed to produce roughly 1 × 104 iodine atoms cm−3 s−1 at midday. The significance of the occurrence of IO at concentrations of up to 4 parts per trillion in the marine boundary layer was then considered from three angles. First, the iodine-catalyzed destruction of ozone was shown to be of a magnitude similar to that caused by odd-hydrogen photochemistry, with up to 13% of the available ozone destroyed per day in a marine air mass. Second, the enrichment factor of iodine in marine aerosol compared with surface seawater was predicted to increase to values of several thousand, in sensible accord with observations. Most of the enrichment should be due to the accumulation of iodate, although other iodine species may also be present, depending on the rate of aerosol recycling. Third, the denoxification of the marine boundary layer was found to be significantly enhanced as a result of aerosol uptake of IONO2, formed from the recombination of IO with NO2.

 

Regional climate simulations of North Atlantic cyclones: changes .. in a climate change scenario Regional climate simulations of North Atlantic cyclones: changes .. in a climate change scenario

Date added: 08/06/2008
Date modified: 07/23/2009
Filesize: 4.19 MB

Semmler, S. Varghese, R. McGrath, P. Nolan, S. Wang, P. Lynch, C. O'Dowd, Regional climate simulations of North Atlantic cyclones: changes in frequency and intensity in a climate change scenario, Climate Res. Vol. 36: 1–16, 2008, doi: 10.3354/cr00732,  2008


Abstract

 

Frequency and intensity of cyclones over the North Atlantic are investigated using 2 data sets from simulations with the Rossby Centre regional climate model RCA3. The model domain comprises large parts of the North Atlantic and the adjacent continents. RCA3 is driven by ECHAM5- OM1 general circulation model data for May to December from 1985 to 2000 and May to December from 2085 to 2100 assuming the SRES-A2 emission scenario. We apply an objective algorithm to identify and track tropical and extratropical cyclones, as well as extratropical transition. The simulation
indicates increase in the count of strong hurricanes and extratropical cyclones. Contrasting, and generally weaker, changes are seen for the less extreme events. Decreases of 18% in the count of extratropical cyclones and 13% in the count of tropical cyclones with wind speeds of ≥18 m s–1 can be found. Furthermore, there is a pronounced shift in the tracks of hurricanes and their extratropical transition in November and December—more hurricanes are seen over the Gulf of Mexico, the Caribbean Sea and the western Sargasso Sea and less over the southern North Atlantic.

Intercomparison of elemental concentrations in total and size-fractionated aerosol samples coll Intercomparison of elemental concentrations in total and size-fractionated aerosol samples coll

Date added: 08/07/1995
Date modified: 07/24/2009
Filesize: 1.12 MB

Francois F., Maenhaut W., Colin J.L., Losno R., Schulz M., Stahlschmidt T., Spokes L.,
Jickells T., Intercomparison of Elemental Concentrations in Total and Size-Fractionated
Aerosol Samples Collected During the Mace Head Experiment, April 1991, Atmos. Environ.
29, 1995, 837-849.


Abstract


During an intercomparison field experiment, organized at the Atlantic coast station of Mace Head, Ireland, in April 1991, aerosol samples were collected by four research groups. A variety of samplers was used, combining both high- and low-volume devices, with different types of collection substrates: Hi-Vol Whatman 41 filter holders, single Nuclepore filters and stacked filter units, as well as PIXE cascade impactors. The samples were analyzed by each participating group, using in-house analytical techniques and procedures. The intercomparison of the daily concentrations for 15 elements, measured by two or more participants, revealed a good agreement for the low-volume samplers for the majority of the elements, but also indicated some specific analytical problems, owing to the very low concentrations of the non-sea-salt elements at the sampling site. With the Hi-Vol Whatman 41 filter sampler, on the other hand, much higher results were obtained in particular for the sea-salt and crustal elements. The discrepancy was dependent upon the wind speed and was attributed to a higher collection efficiency of the Hi-Vol sampler for the very coarse particles, as compared to the low-volume devices under high wind speed conditions. The elemental mass size distribution, as derived from parallel cascade impactor samplings by two groups, showed discrepancies in the submicrometer aerosol fraction, which were tentatively attributed to differences in stage cut-off diameters and/or to bounce-off or splintering effects on the quartz impactor slides used by one of the groups. However, the atmospheric concentrations (sums over all stages) were rather similar in the parallel impactor samples and were only slightly lower than those derived from stacked filter unit samples taken in parallel.

 

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