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

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Documents

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Atmospheric CO2 concentration variations recorded at Mace Head, Ireland, from 1992 to 1994 Atmospheric CO2 concentration variations recorded at Mace Head, Ireland, from 1992 to 1994

Date added: 07/31/1997
Date modified: 07/27/2009
Filesize: 491.17 kB

Bousquet, P., Gaudry. A., Ciais, P., Kazan, V., Monfray, P., Simmonds, P.G., Jennings, S.G., and O'Connor, T.C. (1997). Atmospheric CO2 concentration variations recorded at Mace Head, Ireland from 1992 to 1994. Phys. Chem. Earth, 21, 447-481.


Abstract


Atmospheric CO 2 has been monitored continuously at the Irish station of Mace-Head (MHD) since July 1992. The mean rate of increase is 1.85 ppmv yr -t with a peak-to-peak amplitude of 15.1+1.1 ppmv. The record also shows important short-term variations from the smoothed curve due to both European and oceanic influences and amplified by day/night local effects. Two different baseline conditions are defined in order to remove local perturbations. Restricted Baseline Conditions (RBC) keep data only representing atmospheric background conditions from the West. Extended Baseline Conditions (EBC) add stable air masses coming from all angular sectors to RBC selection. The contrast between western and eastern air masses coming respectively from North-Atlantic ocean and Europe is studied. For air masses arriving from the West, a systematic depletion in 1992-93 is found relative to all surrounding stations within the North- Atlantic basin. The partition of this depletion between European biospheric uptake and the North-Atlantic ocean cannot be performed as long as other tracers are not sampled regularly, or during intensive campaigns at Mace Head (13C/12C, Radon-222 and O2/N2). In contrast, Eastern air masses present strong positive anomalies in CO2 that reflect European sources.

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.

 

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

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

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


Abstract


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

 

Physicochemical properties of atmospheric aerosol at South UIST Physicochemical properties of atmospheric aerosol at South UIST

Date added: 08/06/1996
Date modified: 07/03/2009
Filesize: 906.46 kB

J. A. Lowe, M. H. Smith, B. M. Davison, S. E. Benson, M. K. Hill, C. D. O'Dowd, R. M. Harrison, C. N. Hewitt, Physicochemical properties of atmospheric aerosol at South UIST, Atmospheric EnvironmentVolume 30, Issue 22, , November 1996, Pages 3765-3776.


Abstract


Four field campaigns over the period November 1993 to August 1994 were undertaken on the island of South Uist, off the northwest coast of Scotland as part of the BMCAPE project. Measurements were made of the concentration and chemical composition of aerosol particles, utilising a variety of instruments. Sulphur and nitrogen gas species were also measured throughout these campaigns, together with appropriate meteorological parameters. A variety of air mass types were encountered during the campaigns and the relationship between the physical and chemical aerosol properties are discussed in terms of air mass histories and season factors.

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

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

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


Abstract


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

 

Observations of accumulation mode aerosol composition and soot carbon concentration.......volat Observations of accumulation mode aerosol composition and soot carbon concentration.......volat

Date added: 08/06/1996
Date modified: 07/03/2009
Filesize: 770.09 kB

Smith, M. H., and C. D. O'Dowd (1996), Observations of accumulation mode aerosol composition and soot carbon concentrations by means of a high-temperature volatility technique, J. Geophys. Res., 101(D14), 19,583–19,591.


Abstract


A high-temperature volatility system has been deployed for the measurement of the composition and concentration of the accumulation mode aerosol (0.05 μm < r < 1 μm) within the atmospheric boundary layer. This instrumentation comprises a volatility system based around a Particle Measuring Systems ASASP-X optical particle counter, which was operated together with an aethalometer for the direct observation of soot carbon concentrations. By cycling the heater tube through a range of temperatures from near ambient to over 1000°C, size-differentiated information upon aerosol composition may be obtained. Furthermore, by careful selection of analysis temperatures, discrimination is possible between elemental carbon and the more volatile fractions of the soot carbon aerosol. Observations made over the North Sea near the Dutch coast and in the central United Kingdom are presented for differing environmental conditions with soot carbon concentrations ranging from about 100 to over 6000 ng m-3. For polluted conditions over the North Sea the volatility technique clearly showed the dominance of soot carbon particles over other aerosol components with a narrow carbon particle distribution of mode radius around 0.06 μm accounting for about 80% of all particles with radii below 0.1 μm. Under polluted conditions, only about 25% of the total soot carbon aerosol comprised elemental carbon (with the remainder consisting of more volatile material), whereas this proportion rose to around 50% in the lower carbon loadings found in a cleaner maritime air mass. The use of soot carbon loadings as a tracer of anthropogenic aerosol inputs to oceanic regions is explored on the basis of measurements from a NE Atlantic cruise.

 

Dimethyl sulfide, methane sulfonic acid and physicochemical aerosol properties in Atlantic air Dimethyl sulfide, methane sulfonic acid and physicochemical aerosol properties in Atlantic air

Date added: 08/06/1996
Date modified: 07/01/2009
Filesize: 1.18 MB

Davison, B.M., C.N. Hewitt, R.M. Harrison, M. Schwikowski, U. Baltensperger, C. O'Dowd and M.H. Smith. Dimethyl sulfide, methane sulfonic acid and physico-chemical aerosol properties in Atlantic air from the United Kingdom to Halley Bay. J. Geophys. Res., 101, 22855-22874, 1996.


Abstract


The concentrations of dimethyl sulfide in air were obtained during a cruise between the United Kingdom and the Antarctic in the period October 1992 to January 1993 using a method of sampling and analysis optimized to avoid interferences from oxidants. In equatorial regions (30°N to 30°S) the atmospheric DMS concentration ranged from 3 to 46 ng (S) m-3, with an average of 18 ng (S) m-3, In the polar waters and regions south of the Falkland Islands, concentrations from 3 to 714 ng (S) m-3 were observed, with a mean concentration of 73 ng (S) m-3. The concentrations of a range of DMS oxidation products were also obtained. No clear relationships between reactant and product concentrations were seen. Information on particle number concentration, Fuchs surface area and the thermal volatility characteristics of the ambient aerosol was obtained, but again no clear relationships with sulfur concentrations were observed. Accumulation mode particle concentrations averaged 25 cm-3 in the clean marine and polar air masses south of 58°S while background condensation nuclei (CN) concentrations were of the order of 400-600 cm-3. Simplistic calculations suggest that a particle source strength of about 20-60 particles cm-3 d-1 is required to sustain this background CN concentration. It is not clear whether boundary layer nucleation of new CN or entrainment from the free troposphere provided the source of CN. Periods of elevated CN concentrations (>4000 cm-3) were regularly observed in the boundary layer over the Weddell Sea and were attributed to bursts of new particle formation. However, shortly after these nucleation events the CN concentration rapidly decayed to the background level through coagulation losses, suggesting little impact on the background CN or cloud condensation nuclei (CCN) concentration.

 

Dimethyl sulfide and its oxidation products in the atmosphere of the Atlantic and Southern Ocea Dimethyl sulfide and its oxidation products in the atmosphere of the Atlantic and Southern Ocea

Date added: 08/06/1996
Date modified: 07/23/2009
Filesize: 823.17 kB

Davison, B., C.D. O'Dowd, C.N. Hewitt, M.H. Smith, R.M. Harrison, D.A. Peel, E. Wolf, R. Mulvaney, M. Schwikowski and U. Baltensperger, Dimethyl Sulfide and its Oxidation Products in the Atmosphere of the Atlantic and Southern Oceans, Atmos. Environ., 30, 1895-1906, 1996


Abstract


Dimethyl sulfide, methane sulfonate, non-sea-salt sulfate and sulfur dioxide concentrations in air were obtained during a cruise between the U.K. and the Antarctic during the period October 1992-January 1993. In equatorial regions (30°N to 30°S) the atmospheric DMS concentration ranged from 3 to 46 ng (S)m-3 with an average of 18 ng(S)m-3. In the polar waters and regions south of the Falkland Islands concentrations from 3 to 714 ng(S)m-3 were observed with a mean concentration of 73 ng(S)m-3. Methane sulfonate concentrations were also enhanced in the vicinity of the Antarctic Peninsula and in the Weddell Sea. A simple model of DMS oxidation was used to estimate the ocean to atmosphere flux rate, and this was found to be within the range of previous estimates, with a mean value of 1011 ng (S) m-2 h-1.

 

Sulphur and nitrogen compounds in variable marine continental air masses at the southwest Europ Sulphur and nitrogen compounds in variable marine continental air masses at the southwest Europ

Date added: 08/05/1996
Date modified: 07/07/2009
Filesize: 1.16 MB

Pio et al., 1996. A.C. Pio, M.A. Cerqueira, L.M. Castro and M.L. Salgueiro , Sulphur and nitrogen compounds in variable Marine/Continental air masses at the Southwest European Coast. Atmospheric Environment 30 18 (1996), pp. 3115–3127.


Abstract


Measurements of atmospheric sulphur and nitrogen species were made on the west coast of Portugal, within the framework of BMCAPE project. Four research intensive campaigns took place between November 1993 and August 1994 and revealed pronounced seasonal cycles for DMS and MSA. Surprisingly high levels of DMS were detected during autumn (mean concentration : 776ngSm-3), possibly as a consequence of a later algae bloom or local marsh emissions. COS displayed a slight seasonal variation with mean concentrations ranging from 741 ngSm-3 in autumn up to 903 ngS m-3 in summer. On the basis of backward air mass trajectories and local meteorological data, samples were assigned into different classes of air masses. The lowest concentrations of SO2, nssSO42-, NH3, NH4+, HNO3, NO3- and NO2were found in air masses transported over the Atlantic Ocean and were about 3-10 times lower than those recorded in air masses from continental origin. Nevertheless, for many of the species, the mean concentrations in maritime air were still significantly higher than those previously recorded in remote marine sites, presumably owing to long-range transport of pollutants or contamination induced by mesoscale wind circulation.

 

Source assessment of particulate air pollutants measured at the southwest european coast Source assessment of particulate air pollutants measured at the southwest european coast

Date added: 08/05/1996
Date modified: 07/23/2009
Filesize: 841.66 kB

Pio, C.A., L.M. Castro, M.A. Cerqueira, I.M. Santos, F. Belchior, and M. L. Salgueiro,(1996), Source assessment of particulate air pollutants measured at the southwest , European coast, Atmos. Environ., 30, 3309-3320


Abstract


Aerosol particles and gaseous species were measured in air masses transported to the west coast of Portugal, between November 1993 and August 1994. Samples were taken during four monitoring campaigns distributed along the various seasons of the year, integrated in the EC Project : BMCAPE. Aerosol particles were collected with separation in two size fractions and analysed in relation to total mass, water soluble ions, trace elements and black/organic carbon. Local micro-meteorological parameters and air mass backward trajectories were compared with analytical results in order to define characteristic air mass types and to evaluate the origin of pollutants. Average concentrations on the Portuguese west coast, even in maritime air masses, are higher than values observed in remote oceanic locations. This is probably a consequence of continental European air masses recirculation through the eastern Atlantic Ocean, reinforced by situations of mesoscale transport from the Iberian Peninsula. Principal Component Analysis permitted the identification of five source groups for the fine and coarse aerosol fractions, namely combustion plus road traffic, sea salt spray, secondary aerosol production, soil and possibly non-ferrous metallurgy industries. In the aerosol fine fraction road traffic and combustion contribute on average with 250% of the total fine aerosol mass, while sea spray and secondary production represent 14% and 31%, respectively of the mass loading. Sea spray is by far the major contributor to the coarse fraction with an average of 88% of the suspended coarse aerosol mass.

 

Gas-to-particle conversion of sulphur and nitrogen compounds as studied at marine stations in N Gas-to-particle conversion of sulphur and nitrogen compounds as studied at marine stations in N

Date added: 08/05/1996
Date modified: 07/02/2009
Filesize: 935.92 kB

V. L. Foltescu, E. Selin Lindgren, J. Isakson, M. Oblad, J. M. Pacyna, S. Benson, Gas-to-particle conversion of sulphur and nitrogen compounds as studied at marine stations in Northern Europe, Atmospheric EnvironmentVolume 30, Issue 18, , September 1996, Pages 3129-3140.


Abstract


The present work provides insights into the N- and S-pollution behaviour at rural and remote sites in Northern Europe. Formation of SO42- and NO3- from their precursor gases receives special attention in order to understand the significance of chemical conversion in shaping the distributions of concentration and deposition monitored at our sites : Säby-on the Swedish west coast, Lista-on the Norwegian south coast and South Uist-on the Hebride Islands in Northern Scotland. Owing mainly to the complexity of the problem, the approach is semiquantitative. Concentration patterns of S- and N-compounds for air mass transport between the sites were investigated for 10 periods (13d), within continental(6d) and oceanic (7 d) air masses. The observations spanned over both winter and summer days and conclusions could be drawn in some cases with respect to seasonality. The measurements were performed during the BMCAPE (Background Maritime Contribution to Atmospheric Pollution in Europe) project in 1993 and 1994. S- and N-ratios were used as indicators of air mass age, chemical conversion efficiency and en-route deposition. The S-ratio is defined as the ratio of particulate S (as SO42-) to total S (as SO2 and SO42-). The N-ratio is taken as the ratio of gaseous HNO3-N over particulate NO3--N. S-ratios at Säby and Lista agreed very well in those cases when no or insignificant precipitation occurred. Higher S-ratios and lower N-ratios were typical for conditions of high relative humidity. It is conceivable that condensed phase chemistry was of major importance in the SO2 oxidation and that HNO3 was absorbed onto the wet aerosol particles. Stagnation of the air masses over source regions of high emission densities and rates resulted in accumulation of pollution, the S-ratios in such conditions being high due to the longer transport time. The S-ratios for marine air flow at Säby and Lista no longer agreed (higher at Lista) as in the case of continental air masses. The reason is likely to be the proximity of the Lista station to the sea. Lista was highly affected by sea spray produced by the strong westerly winds. The N-ratio remained very low in the case of maritime air masses due to unexpectedly high NO3- concentrations. It is conceivable that the high load of NO3- is due to sea spray of surface water. More efficient SO2 deposition over land than over sea has been observed in the westerly airflow by the relative loss of SO2 while the flow swept over land.

 

Lifetime and emission estimates of 1,1,2-trichlorotrifluorethane (CFC-113) from daily global background observations June 1982–June 1994 Lifetime and emission estimates of 1,1,2-trichlorotrifluorethane (CFC-113) from daily global background observations June 1982–June 1994

Date added: 08/01/1996
Date modified: 07/24/2009
Filesize: 1.48 MB
Fraser, P., D. Cunnold, F. Alyea, R. Weiss, R. Prinn, P. Simmonds, B. Miller, and R. Langenfelds (1996), Lifetime and emission estimates of 1,1,2-trichlorotrifluorethane (CFC-113) from daily global background observations June 1982–June 1994, J. Geophys. Res., 101(D7), 12,585–12,599.

Abstract


Observations every two hours of CCl2FCClF2 at Mace Head, Ireland (February 1987–June 1994); Cape Meares, Oregon (April 1984–June 1989); Ragged Point, Barbados (October 1985–June 1994); Cape Matatula, Samoa (October 1985–June 1989 and January 1992–June 1994); and Cape Grim, Tasmania (June 1982–June 1994) are reported. The observations from Cape Grim have been extended back to 1978 using archived air samples. The global atmospheric abundance of CCl2FCClF2 is indicated to have been growing exponentially between 1978 and 1987 with an e-folding time of approximately 7.6 years; it has been growing less rapidly since that time. On January 1, 1994, the mean inferred northern hemispheric mixing ratio in the lower troposphere was 84.4 ± 0.4 ppt and the southern hemispheric value was 80.6 ± 0.4 ppt; the global growth rate in 1991–1993 is estimated to have averaged approximately 3.1 ± 0.1 ppt/year. The differences between the northern and southern hemispheric concentrations are calculated to be consistent with the almost entirely northern hemispheric release of this gas. The annual release estimates of CCl2FCClF2 by industry, which include estimates of eastern European emissions, fairly consistently exceed those deduced from the measurements by approximately 10% from 1980 to 1993. The uncertainties in each estimate is approximately 5%. This difference suggests that up to 10% of past production might not yet have been released. The measurements indicate that atmospheric releases of CCl2FCClF2 have been decreasing rapidly since 1989 and in 1993 amounted to 78 ± 27 × 106 kg or 42 ± 15% of the 1985–1987 emissions.

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%.

Concurrent Measurements of Black Carbon aerosol and Carbon Monoxide at Mace Head Concurrent Measurements of Black Carbon aerosol and Carbon Monoxide at Mace Head

Date added: 07/31/1996
Date modified: 07/27/2009
Filesize: 3.16 MB

Jennings, S.G., Spain, T.G., Doddridge, B.G., Maring, H., Kelly, B.P., and Hansen, A.D.A. (1996) - Concurrent measurements of black carbon aerosol and carbon monoxide at Mace Head. J.Geophys. Res., 101, 19,447 - 19,454.


Abstract

 

Continuous measurements of white light attenuation (ATN) through a quartz fiber filter (related to aerosol black carbon content) and of carbon monoxide (CO) carried out over the period December 1991 through July 1992 at the Mace Head atmospheric field research station (53°19'N, 9°54'W) near Carna, County Galway on the west coast of Ireland are presented. Isentropic air flow back trajectories, condensation nuclei concentration data, and meteorological data were generated as part of the Atmosphere/Ocean Chemistry Experiment. Use is made of this supporting data together with synoptic weather charts in the analysis of the measurements. Measurements of ATN and CO are reported for unmodified marine air from the North Atlantic which yield ATN and ATN/CO values in the range 1-4 × 10-3 m-3 and 1-4 × 10-5 m-3 ppbv-1. Increasing values of ATN and ATN/CO are obtained for polluted transatlantic air, modified marine air, and polluted air from the UK and/or Europe. The covariance of ATN and CO obtained for these air masses suggests a common source. Transport of air from west of the African Saharan region to Mace Head is accompanied by a rise in optical attenuation purported to be due to absorbing desert dust aerosol without a concurrent rise in CO.

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.

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

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

Abstract


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

Measurements of Atmospheric Mercury Concentrations in Northwestern and Central Europe --- Comparison Measurements of Atmospheric Mercury Concentrations in Northwestern and Central Europe --- Comparison

Date added: 08/26/1995
Date modified: 07/23/2009
Filesize: 1.09 MB

R. Ebinghaus, H.H. Kock, S.G. Jennings, P. McCartin and M.J. Orren (1995): Measurements of Atmospheric Mercury Concentrations in Northwestern and Central Europe --- Comparison of Experimental Data and Model Results, Atmospheric Environment, Vol. 29, No. 22, pp. 3333 - 3344


Abstract


Field experiments were carried out at various sites in Europe to compare ambient air and precipitation concentrations of atmospheric mercury with model data. In addition, ozone and aerosol black carbon concentrations in air were measured simultaneously as input data for validation of the EMEP-based European long-range transport model. Data sets for mercury in air and precipitation, ozone and aerosol black carbon show that the selected sites range from background conditions for Northwestern Europe to regionally influenced air masses from heavily industrialized Central Europe. Measured 12 h averaged mercury concentrations in air range from 2.1 ng m-3 for Mace Head, Ireland to 8.2 ng m-3 for the Halle/Leipzig/Bitterfeld area in former German Democratic Republic. Precipitation concentrations of total mercury from 17 to 460 ng k-1 were measured from 1991 to 1993 for the same sites. Experimental data and model results for total gaseous mercury and mercury in precipitation are in good agreement.

Measurements of Atmospheric Mercury Concentrations in Northwestern and Central Europe --- Comparison Measurements of Atmospheric Mercury Concentrations in Northwestern and Central Europe --- Comparison

Date added: 08/26/1995
Date modified: 07/10/2009
Filesize: 1.12 MB

R. Ebinghaus, H.H. Kock, S.G. Jennings, P. McCartin and M.J. Orren (1995): Measurements of Atmospheric Mercury Concentrations in Northwestern and Central Europe --- Comparison of Experimental Data and Model Results, Atmospheric Environment, Vol. 29, No. 22, pp. 3333 - 3344


Abstract


Field experiments were carried out at various sites in Europe to compare ambient air and precipitation concentrations of atmospheric mercury with model data. In addition, ozone and aerosol black carbon concentrations in air were measured simultaneously as input data for validation of the EMEP-based European long-range transport model. Data sets for mercury in air and precipitation, ozone and aerosol black carbon show that the selected sites range from background conditions for Northwestern Europe to regionally influenced air masses from heavily industrialized Central Europe. Measured 12 h averaged mercury concentrations in air range from 2.1 ng m-3 for Mace Head, Ireland to 8.2 ng m-3 for the Halle/Leipzig/Bitterfeld area in former German Democratic Republic. Precipitation concentrations of total mercury from 17 to 460 ng k-1 were measured from 1991 to 1993 for the same sites. Experimental data and model results for total gaseous mercury and mercury in precipitation are in good agreement.

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.

 

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

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

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


Abstract


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

 

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

Aitken Nuclei Measurements and Evidence of Gas-to-particle conversion Processes at Mace Head, Ireland.. Aitken Nuclei Measurements and Evidence of Gas-to-particle conversion Processes at Mace Head, Ireland..

Date added: 08/26/1994
Date modified: 07/23/2009
Filesize: 840.25 kB

O'Connor, T.C., McGovern, F.M., Jennings, S.G. & Philipp, C.(University of Hannover)  (1994)-
Aitken nuclei measurements and evidence of gas-to-particle conversion processes at Mace Head, Ireland. Proceedings of  EUROTRAC 94 Symposium, The Hague, SPB Academic Publishing, 1206-1209.


Global trends and annual releases of CCl3F and CCl2F2 estimated from ALE GAGE and other measure Global trends and annual releases of CCl3F and CCl2F2 estimated from ALE GAGE and other measure

Date added: 08/07/1994
Date modified: 07/24/2009
Filesize: 1.87 MB

Cunnold, D. M., P. J. Fraser, R. F. Weiss, R. G. Prinn, P. G. Simmonds, B. R. Miller, F. N. Alyea, and A. J. Crawford (1994), Global trends and annual releases of CCl3F and CCl2F2 estimated from ALE/GAGE and other measurements from July 1978 to June 1991, J. Geophys. Res., 99(D1), 1107–1126.


Abstract


Thirteen years of Atmospheric Lifetime Experiment/Global Atmospheric Gases Experiment CCl3F and CCl2F2 measurements at five remote, surface, globally distributed sites are analyzed. Comparisons are made against shipboard measurements by the Scripps Institution of Oceanography group and archived air samples collected at Cape Grim, Tasmania, since 1978. CCl3F in the lower troposphere was increasing at an average rate of 9.2 ppt/yr over the period July 1978 to June 1988. CCl2F2 was increasing at an average 17.3 ppt/yr in the lower troposphere over the same period. However, between July 1988 and June 1991 the increases of CCl3F and CCl2F2 in this region have averaged just 7.0 ppt/yr and 15.7 ppt/yr, respectively. The rate of increase has been decreasing 2.4 ppt/yr2 and 2.9 ppt/yr2 over this 3-year period. Based on a recent scenario of the global releases of these compounds and using the new calibration scale SIO 1993, the equilibrium lifetimes are estimated to be 44 - 10 + 17 and 180 - 81 + 820 years for CCl3F and CCl2F2, respectively. Using these lifetime estimates and a two-dimensional model, it is estimated that global releases of these two chlorofluorocarbons in 1990 were 249 ± 28 × 106 kg for CCl3F and 366 ± 30 × 106 kg for CCl2F2. It is also estimated that combined releases of these chlorofluorocarbons in 1990 were 21 ± 5% less than those in 1986.

 

Isentropic airflow probability analysis Isentropic airflow probability analysis

Date added: 08/06/1994
Date modified: 07/24/2009
Filesize: 1.32 MB

Merrill, J. T. (1994), Isentropic airflow probability analysis, J. Geophys. Res., 99(D12), 25,881–25,889.


Abstract

 

Trajectory analysis has been used to identify possible sources in both short-and long-range atmospheric transport. Here the focus is on the climatological pathway of airflow to the Atmosphere/Ocean Chemistry Experiment sites, determined by superposition of ensembles of isentropic trajectories. The trajectories are prepared from wind fields on surfaces of constant potential temperature interpolated from the National Meteorological Center global analysis, calculated twice daily for each site for the period from 1986 to 1993. At Bermuda there is a notable seasonal variation, with the months of May–November dominated by flow around the subtropical anticyclone, while flow from the northwest and west is more common in the cooler months of December–April. Flow from the west predominates at Mace Head, Ireland, in the months from April–September, while flow from the east (over Great Britain and western Europe) is of increased importance during October–March. At Izaña the flow is most commonly from the west; flow from the east, over Africa and southern Europe, is most common during the months of July–September. The winds at Barbados, West Indies, are much steadier than at the other sites, and there is little seasonal variation in the general pattern of flow. The circulation during precipitation events, evaluated as the airflow weighted by rainfall amount, showed a striking difference from the general pattern of airflow at Mace Head, especially during October–March: in the absence of rain the winds are much more common from the east, over polluted continental areas, than during rain events, when the dominance of flow from the west is greater.

 

Interannual variability over the eastern North Atlantic Ocean Chemical and meteorological evide Interannual variability over the eastern North Atlantic Ocean Chemical and meteorological evide

Date added: 08/06/1994
Date modified: 07/24/2009
Filesize: 1.53 MB

Doddridge, B. G., P. A. Dirmeyer, J. T. Merrill, S. J. Oltmans, and R. R. Dickerson (1994), Interannual variability over the eastern North Atlantic Ocean: Chemical and meteorological evidence for tropical influence on regional-scale transport in the extratropics, J. Geophys. Res., 99(D11), 22,923–22,935.


Abstract


Observed boreal fall season (September–November) 1991 surface CO data from Mace Head, Ireland, are characterized by particularly high mixing ratios, as evidenced by high means, medians, and maxima for those months, relative to the same dato for boreal fall 1992. Air parcels characterized by elevated CO during fall 1991 are attributed to European sources on the basis of isentropic back trajectory analysis. A histogram of the 1991 data shows a bimodal distribution representing two discrete source regions, North Atlantic and European, while the 1992 data show only one mode, representing primarily zonal westerly flow over the North Atlantic Ocean. A similar distinction exists in O3 data between the two years. Considerable interannual variability has important implications for observationalists and modelers alike; an inherent uncertainty is introduced by basing any determination of trend from only a few years of data. An isentropic flow climatology for Mace Head illustrates significant differences in the regional-scale flow patterns to Mace Head between the 1991 and the 1992 fall seasons. These differences have been examined in terms of general dynamical principles and tropical/extratropical coupling. There is evidence of the existence of Rossby wave links with the tropical upper troposphere over South America and the central Pacific Ocean which are responsible for the climatic forcing giving rise to the observed interannual variation in large-scale flow patterns and influencing the chemical character of air parcels reaching Mace Head. Using CO as a tracer for short-lived continental anthropogenic O3 precursors and calculating ΔO3/ΔCO for air parcel trajectories following anticyclonic paths over western Europe during the late summer and fall season of 1991, we estimate O3 production over western Europe at about 66 (40–96) billion moles of O3 per summer (∼3 Tg O3 per summer), based on 1985 CO emission inventory dam (37 Tg CO yr−1 for western Europe).

 

Volatility of Elemental Carbon Volatility of Elemental Carbon

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

Abstract


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

Volatility of Elemental Carbon Volatility of Elemental Carbon

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

Abstract


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

Mass Measurements Of Aerosol at macehead on the west coast of Ireland Mass Measurements Of Aerosol at macehead on the west coast of Ireland

Date added: 07/31/1994
Date modified: 07/24/2009
Filesize: 1.91 MB

McGovern F.M., Krasenbrink, A., Jennings, S.G., Georgi, B., Spain, T.G., Below, M., and O'Connor , T.C. (1994) Mass measurements of aerosol at Mace Head on the west coast of Ireland. Atmos. Environ, 28, 1311 -1318.


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

Home Environment and Childhood Asthma Home Environment and Childhood Asthma

Date added: 07/31/1994
Date modified: 07/02/2009
Filesize: 224.33 kB

Leen, M.G., O'Connor, T.C., Kelleher, C.C., Loftus, B.G. & Mitchell, C. (1994)- Home environment and childhood asthma. The Irish Medical Journal, Vol. 87, No. 5, pp. 142-144.


Abstract


The prevalence of childhood asthma has increased dramatically in the past 20 years. The reasons for the increase are unclear but many authors suggest that changes in the home environment favourable to proliferation of the house dust mite are to blame. Our study aimed to compare home environment of children with asthma and controls. A questionnaire on home environment was administered to the parents of 134 children with asthma and 118 controls. Detailed studies of home temperature, humidity and dust mite allergen (DERpI) levels were performed in 20 homes (10 from each group). The questionnaire response rate was 86%. There were no significant differences between asthma and control homes with respect to social class, type of housing, smoking habits, pets, insulation, home heating, bedding, carpeting and domestic cleaning habits. A first degree family history of atopy wasobtained in 42% of asthmatic families and in 16% of controls. Temperature, humidity and dust mite allergen levels were similar in both groups. The majority gave readings exceeding recommended norms. Values for DERpI were above thresholds by a factor of 5 in 48%. Home environment does not significantly differ in children with or without asthma. The home environment is now generally mite friendly, and large segments of the childhood population are now exposed to high levels of DERpI. This may account for the increasing prevalence as more and more children with an atopic background develop overt symptoms in response to high levels of allergen load.

Physicochemical Properties of Aerosols Over the Northeast Atlantic: Evidence for Wind-Speed-Related Physicochemical Properties of Aerosols Over the Northeast Atlantic: Evidence for Wind-Speed-Related

Date added: 08/06/1993
Date modified: 07/03/2009
Filesize: 1.04 MB

O'Dowd, C. D., and M. H. Smith (1993), Physicochemical Properties of Aerosols Over the Northeast Atlantic: Evidence for Wind-Speed-Related Submicron Sea-Salt Aerosol Production, J. Geophys. Res., 98(D1), 1137–1149.


Abstract


Physicochemical characteristics of submicron aerosol particles over the Northeast Atlantic (63°N, 8°W) during October/November 1989 have been examined using a thermal analytical technique and are classified according to air mass origin. Aerosol associated with anthropogenically influenced air masses contained typically 80% sulphate particles by number, the remainder being soot carbon and sea salt. For Arctic air masses the contribution of sulphate to the total aerosol was reduced to around 65%, due to low concentrations relative to sea salt which is dependent on wind speed. In situations with clean maritime air and high wind speeds, sulphate aerosol accounted for less than 25% of the total accumulation mode particles, the remainder consisting predominantly of sea salt. Arctic air masses and clean maritime air during periods of high winds were consistently acidic with inferred molar ratios of NH4 +/SO4 = near 0.2. The continental and modified maritime aerosol encountered was found to have molar ratios of about 0.8. Soot carbon was present in all air masses to a similar degree (5–13%). In clean air masses, submicron sea salt aerosol concentrations showed a strong exponential increase with wind speed (correlation coefficients cc ≥ 0.8), down to a dry particle radius of 0.05 μm. Under these “clean air” conditions and high winds the sea salt aerosol dominated all particle sizes for r > 0.05 μm and accounted for approximately 75% of the total concentration, suggesting that under these conditions, sea salt aerosol would comprise the primary source of cloud condensation nuclei (CCN) in stratiform clouds.

 

Submicron Particle, Radon and Soot Carbon Characteristics over Northeast Atlantic Submicron Particle, Radon and Soot Carbon Characteristics over Northeast Atlantic

Date added: 08/01/1993
Date modified: 07/23/2009
Filesize: 1 MB

O'Dowd, C. D., M. H. Smith, and S. G. Jennings (1993), Submicron Particle, Radon, and Soot Carbon Characteristics Over the Northeast Atlantic, J. Geophys. Res., 98


Abstract


Atmospheric aerosol particles (0.05μm ≤ rdry ≤ 1.5μm), 222Rn, and soot carbon mass were measured on a cruise over the Northeast Atlantic (63°N, 8°W) during October and November 1989. An accumulation mode (AM) was present in all particle data and was characterized by a lognormal size distribution with parameters N cm−3 (total number concentration), rg μm (geometric mean radius) and σg (geometric standard deviation). For aerosol associated with the “cleanest” Northeast Atlantic maritime and Arctic air masses, the AM parameters were found to be 16 cm−3 ≤ N ≤ 48 cm−3, 1.32 ≤ σg ≤ 1.46, and 0.08 μm < rg < 0.09 μm, leading to AM masses of between 0.20 μg m−3 and 0.38 μg m−3. Clean background levels of soot carbon mass for maritime and Arctic air were estimated to be around 20 ng m−3 and were associated with particle size radii r ≤ 0.15 μm. Soot carbon mass showed an excellent correlation with AM number concentration (∝=0.93), demonstrating its usefulness as an air mass tracer and as an indicator of anthropogenic pollutant transport. By comparison, radon, which is often used for this purpose, exhibited a significantly poorer correlation (∝=0.60) for this region. Approximately 9% of the total AM mass was accounted for by soot carbon, regardless of air mass origin, suggesting that early winter marine aerosol in the remote North Atlantic is primarily of anthropogenic origin.

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

Scavenging Of Sub-Micrometre Aerosol Particles By Water Drops Scavenging Of Sub-Micrometre Aerosol Particles By Water Drops

Date added: 07/31/1993
Date modified: 07/06/2009
Filesize: 1.36 MB

Byrne, M.A., and Jennings, S.G. (1993). - Scavenging of submicrometre aerosol particles by water drops. Atmos. Environ., 27A, 2099 - 2105.


Abstract


Experiments were carried out in order to measure the collection efficiencies, E, with which small-sized water drops (of radii between 400 and 500 um) carrying electrical charge, Q (from 5 x 10^-4 to 22 x 10^-11 C) collect monodisperse aerosol particles of radii between 0.35 and 0.88 um. The measured values of collection efficency were within the range 1-6% and were in good agreement with previous results. the measurements show an increase in aerosol particles radius, drop radius and drop charge

Optical and Thermal Measurements of Black CArbon Aerosol Content.....of the Specific Attenuation Cross-section, Sigma. Jennings, Liousse, Cachier Optical and Thermal Measurements of Black CArbon Aerosol Content.....of the Specific Attenuation Cross-section, Sigma. Jennings, Liousse, Cachier

Date added: 07/31/1993
Date modified: 07/03/2009
Filesize: 2.92 MB

Louisse, C., Cachier, H., and Jennings, S.G. (1993). - Optical and thermal measurements of black carbon aerosol contents in different environments: variation of the specific attenuation cross-section. Atmos. Environ., 27A, 1203 - 1211.


Abstract


In optical analysers devoted to the analysis of atmospheric black carbon concentration, the specific attenuation cross-section, a is the factor used to convert the attenuation of a light beam due to the absorption of aerosols deposited on a filter into their black carbon content. We have tried to gain further insight for a suitable choice of sigma value, using both optical analysis (with an aethalometer) and thermal analysis of black carbon aerosols and comparison of the two sets of results. Samples which were investigated originate from varying environments, including suburban areas, tropical areas where biomass buming was prevalent and from more remote locations. In a given type of atmospheric environment, a values are found to be constant

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.

Global Average Concentration and Trend for Hydroxyl Radicals Deduced From ALE GAGE Trichloroeth Global Average Concentration and Trend for Hydroxyl Radicals Deduced From ALE GAGE Trichloroeth

Date added: 08/07/1992
Date modified: 07/24/2009
Filesize: 1.53 MB

Prinn, R., et al. (1992), Global Average Concentration and Trend for Hydroxyl Radicals Deduced From ALE/GAGE Trichloroethane (Methyl Chloroform) Data for 1978–1990, J. Geophys. Res., 97(D2), 2445–2461.


Abstract

Atmospheric measurements at several surface stations made between 1978 and 1990 of the anthropogenic chemical compound 1,1,1-trichloroethane (methyl chloroform, CH3CCl3) show it increasing at a global average rate of 4.4 ± 0.2% per year (1σ) over this time period. The measured trends combined with industrial emission estimates are used in an optimal estimation inversion scheme to deduce a globally averaged CH3CCl3 tropospheric (and total atmospheric) lifetime of 5.7 (+0.7, −0.6) years (1σ) and a weighted global average tropospheric hydroxyl radical (OH) concentration of (8.7 ± 1.0) × 105 radical cm−3 (1σ). Inclusion of a small loss rate to the ocean for CH3CCl3 of 1/85 year−1 does not affect the stated lifetime but lowers the stated OH concentration to (8.1 ± 0.9) × 105 radical cm−3 (1σ). The rate of change of the weighted global average OH concentration over this time period is determined to be 1.0 ± 0.8% per year (1σ) which has major implications for the oxidation capacity of the atmosphere and more specifically for methane (CH4), which like CH3CCl3 is destroyed primarily by OH radicals. Because the weighting strongly favors the tropical lower troposphere, this deduced positive OH trend is qualitatively consistent with hypothesized changes in tropical tropospheric OH and ozone concentrations driven by tropical urbanization, biomass burning, land use changes, and long-term warming. We caution, however, that our deduced rate of change in OH assumes that current industry estimates of anthropogenic emissions and our absolute calibration of CH3CCl3 are accurate. The CH3CCl3 measurements at our tropical South Pacific station (Samoa) show remarkable sensitivity to the E1 Nino-Southern Oscillation (ENSO), which we attribute to modulation of cross-equatorial transport during the northern hemisphere winter by the interannually varying upper tropospheric zonal winds in the equatorial Pacific. Thus measurements of this chemical compound have led to the discovery of a previously unappreciated aspect of tropical atmospheric tracer transport.

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

A High Temperature Volatility technique for determination of atmospheric aerosol composition A High Temperature Volatility technique for determination of atmospheric aerosol composition

Date added: 07/31/1992
Date modified: 06/30/2009
Filesize: 2.32 MB
O'Dowd, C.D., Jennings, S.G., Smith M.H., and Cooke, W.F. (1992) - A high temperature volatility technique for determination of atmospheric aerosol composition. J. Aerosol Sci., 23, S905 - S908.

Abstract


Size segregated atmospheric aerosol composition, over the radius range 0.05μm ≤ r ≤ 1.5μm, is inferred using an optical particle counter equipped with a high temperature heater tube cycling through temperatures from 20°C to 870°C. The volatility system infers the presence of common atmospheric constituents such as H2SO4, (NH4)2SO4, NaCl, and soot carbon. This system has been successfully used to determine the physico-chemical characteristics of accumulation mode aerosol associated with air masses of different origin. Results from ship-borne and ground based measurements are presented. For continental and modified maritime air, (NH4)2SO4 was observed to be the dominant species, whilst H2SO4 was more abundant in Arctic aerosol. Sea-salt aerosol accounts for ≈75% of accumulation mode particle concentration for maritime aerosol in periods of high wind speeds. We also show that soot carbon can be identified in polluted air using this technique.

CFCs in Connemara Technology Ireland September 1991 CFCs in Connemara Technology Ireland September 1991

Date added: 09/28/1991
Date modified: 07/27/2009
Filesize: 1.37 MB
O'Connor, T.C. & Simmonds, P.G. (1991)- CFCs in Connemara, Technology Ireland, 23, No. 5, pp. 19-21.

Abstract

 

At an isolated research centre in Conemara, scientist are monitoring the background atmospheric levels of the CFCs and other chemicals which are destroying the ozone layer. Tom O'Connor and Peter Simmonfs write here of how the UCG centre is playing a vital role in international studies to monitor the accumulation of these gases in the global atmosphere.

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

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

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


Abstract


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

Physical Characteristic of the Ambient Aerosol At Macehead Physical Characteristic of the Ambient Aerosol At Macehead

Date added: 07/31/1991
Date modified: 07/23/2009
Filesize: 3.29 MB

Jennings, S.G., O'Dowd, C.D., O'Connor, T.C., and McGovern, F.M (1991). - Physical characteristics of the ambient aerosol at Mace Head. Atmos. Environ., 25A, 557 - 562.


Abstract


This paper describes results of a reasonably extensive series of ambient aerosols measurements conducted for the first time from MAce HEad, on the west coast of Ireland. Aerosol size distributions (0.045 <radius,r, <1.5 micrometres (Um)) And Basic meteorological parameters were measured under both maritime, modified maritime and continental air mass conditions. It was found that the shape of the size distribution spectra is dependent on air mass source

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

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

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


Abstract


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

 

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

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

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


Abstract


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

Atmospheric Emissions and Trends of Nitrous Oxide Deduced From 10 Years of ALE–GAGE Data Atmospheric Emissions and Trends of Nitrous Oxide Deduced From 10 Years of ALE–GAGE Data

Date added: 08/01/1990
Date modified: 07/27/2009
Filesize: 1.5 MB

R.G. Prinn, D. Cunnold, R. Rasmussen, P. Simmonds, F. Alyea, A. Crawford, P. Fraser, and R. Rosen.  Atmospheric emissions and trends of nitrous oxide deduced from ten years of ALE/GAGE data. J. Geophys. Res., 95, 18369-18385, 1990.


Abstract


We present and interpret long-term measurements of the chemically and radiatively important trace gas nitrous oxide (N2O) obtained during the Atmospheric Lifetime Experiment (ALE) and its successor the Global Atmospheric Gasses Experiment (GAGE). The ALE/GAGE data for N2O comprise over 110,000 individual calibrated real-time air analyses carried out over a 10-year (July 1978-June 1988) time period. These measurements indicate that the average concentration in the northern hemisphere is persistently 0.75+/-0.16 ppbv higher than in the southern hemisphere and that the global average linear trend in N2O lies in the range from 0.25 to 0.31% yr-1, with the latter result contingent on certain assumptions about the long-term stability of the calibration gases used in the experiment. Interpretation of the data, using inverse theory and a 9-box (grid) model of the global atmosphere, indicates that the N2O surface emissions into the 90°N-30°N, 30°N-0°, 0°-30°S, and 30°S-90°S semihemispheres account for about 22-34, 32-39, 20-29 and 11-15% of the global total emissions, respectively.<p>The measured trends and latitudinal distributions are consistent with the hypothesis that stratospheric photodissociation is the major atmospheric sink for N2O, but they do not support the hypothesis that the temporal N2O increase is caused solely by increases in anthropogenic N2O emissions associated with fossil fuel combustion. Instead, the cause for the N2O trend appears to be a combination of a growing tropical source (probably resulting from tropical land disturbance) and a growing northern mid-latitude source (probably resulting from a combination of fertilizer use and fossil fuel combustion). The exact combination of these sources which best fits the data depends on the assumed tropospheric-stratospheric exchange rates for N2O in the northern hemisphere relative to the southern hemisphere. Accepting a theoretically-calculated N2O lifetime of 166+/-16 years due to stratospheric destruction only, we deduce from the ALE/GAGE data a 10-year average global N2O emission rate of (20.5+/-2.4)×1012gN2O yr-1, but with significant year-to-year variations in emissions associated perhaps with year-to-year variations in tropical land disturbance.

Micron-sized droplets irradiated with a pulsed CO2 laser measurement of explosion and breakdown thresholds Micron-sized droplets irradiated with a pulsed CO2 laser measurement of explosion and breakdown thresholds

Date added: 07/31/1990
Date modified: 07/03/2009
Filesize: 1.33 MB
Pinnick, R.G., Biswas, A., Armstrong, R.L., Jennings, S.G., Pendleton, J.D., and Fernandez, G. (1990). - Micron-sized droplets irradiated with a pulsed CO2 laser: Measurements of explosion and breakdown thresholds. Appl. Opt., 29, 918 - 925.

Abstract


Measurements of minimum CO2 laser fluence required to explode or disintegrate 10–60 µm radius droplets of water, ethanol, diesel (hexadecane), CCl4, bromoform, and ethyl bromide are reported. Threshold fluences range from 0.4 J cm-2 for 10-µm radius ethanol drops to 20 J cm-2 for 30µm bromoform drops. Threshold fluences for water droplets are ~3 J cm-2 independent of drop size. Comparison of the measurements to calculations of laser fluence required for considered absorbing droplets to reach superheat temperature is in good agreement for cases where liquid material properties are known, suggesting that superheating of droplets is the dominant mechanism causing explosion/disintegration. Measured droplet-induced laser breakdown thresholds are considerably higher than explosion thresholds and have less dependence on droplet size and composition. The highest breakdown threshold values are for water drops, which range from 150 to 280 J cm-2 (0.9–1.7 × 109W cm-2) compared with 670 J cm-2 (4.0 × 109 W cm-2) for clean air breakdown for the laser pulse length and spot size.

Air Pollution Measurements at Macehead Air Pollution Measurements at Macehead

Date added: 08/07/1988
Date modified: 07/27/2009
Filesize: 2.14 MB

Air Pollution Measurements at Macehead Air Pollution Measurements at Macehead

Date added: 08/07/1988
Date modified: 09/11/2009
Filesize: 2.14 MB

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

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

Abstract


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

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

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

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


Abstract

 

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

Extinction and Liquid Water Content Measurements at CO2 Laser wavelengths Extinction and Liquid Water Content Measurements at CO2 Laser wavelengths

Date added: 07/31/1987
Date modified: 07/01/2009
Filesize: 601.9 kB

Nolan, P.F., and Jennings, S.G. (1987). - Extinction and liquid water content measurements at CO2 laser wavelengths. J. Atmos. and Oceanic Technol., 4, 391 - 400.


Abstract

 

Measurements have been made of both extinction coefficients in an evaporating laboratory cloud at wavelength λ = 10.591 μm using a CO2 laser, and of liquid water content (LWC) at the center of the cloud using a continuous filtration LWC device. Cloud uniformity has been promoted and monitored within the laboratory chamber. The measurements give an overall linear relation between extinction and liquid water content independent of droplet-size distribution in reasonably good agreement with the Chýlek prediction. The measurements show significantly better agreement with the Chýlek prediction for the narrower cloud drop-size distributions. The broader size distribution data show an underestimate in extinction compared to the Chýlek prediction, providing the first experimental evidence for the large radius limit (radius 12 μm) in use of the Chýlek relation.

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