Key dates in Mace Head's history

1958	Renting and refurbishing a coastal lookout post on Mace Head.
1973	Purchase of a ruined cottage and seven acres extending to the shore.
1985	Refurbishment of the cottage by the University as a laboratory.
1987	Commencement of continuous measurements by international groups, such as CFC gases in the Global Atmospheric Gases Experiment [GAGE].
1988	Expansion forthe US-based Atmosphere-Ocean Chemistry Experiment (AEROCE) and construction of first shore laboratory and sampling tower.
1990	Enlargement of the cottage and construction of second laboratory near the shore.

The station is overseen by a Management Committee drawn from NUI's Atmospheric Research Group, Department of Physics, which carries out research with the help of research assistants, postgraduate students and post-doctoral researchers. Throughout the year, many scientists visit the station for long-term measurement campaigns, shorter-term projects, and international workshops. Research performed at Mace Head is documented widely in the international scientific literature.

International Dimension

Atmospheric pollution is a complex problem that transcends national boundaries, thus research into its causes requires international collaboration and a sharing of resources and expertise. Mace Head is recognised world-wide as a key location in the study of climate change. Its facilities have been used by scientists from over one hundred universities and institutions in twenty countries. It is central to a number of international research networks and is a baseline station for the Global Atmosphere Watch of the World Meteorological Organization since 1994. It is an important point of contact between European and American scientists and has achieved a high profile in atmospheric research.

Atmospheric Research at Mace Head

Research activities at Mace Head have been mainly concerned with measurements of Northern Hemisphere background levels of trace substances in air from the Atlantic Ocean. Sources and sinks of these substances and the complex biogeochemical processes which they undergo in the atmosphere are investigated.

• Since 1987, Mace Head has been one of five international sites studying the life cycles of chlorofluorocarbon (CFC) gases as part of the Advanced Global Atmospheric Gases Experiment (AGAGE) [Simmonds et al., 1996].
• Since 1987, Mace Head has been one of four primary sites participating in the Atmosphere Ocean Chemistry Experiment (AEROCE) to study biogeochemical cycles in the North Atlantic Ocean, which forms part of the North Atlantic Regional Experiment (NARE). AEROCE is funded by the US National Science Foundation and involves several US university and governmental institutions [Prospero, 1997].
• In 1994 and 1995, NUI-Galway coordinated a EU-funded project to assess the Background Maritime Contribution to Atmospheric Pollution in Europe (BMCAPE), which involved six sites along Europe's Atlantic coast, including Mace Head.
• In 1996 and 1997, Mace Head was chosen as the primary measuring site for Atmospheric Chemistry Studies in the Marine Environment (ACSOE), led by the University of East Anglia [Broadgate et al., 1998].
• Since 1987, Mace Head has been part of the European Tropospheric Ozone Research (TOR) network and still contributes to European and American studies of ground level ozone concentrations [Simmonds et al., 1997].
• Since 1989, extensive studies of heavy metals in the atmosphere, including elemental mercury, have been undertaken under the auspices of an Irish-German collaboration. In 1995, the first international workshop for field intercomparison of measurement techniques for mercury in air and precipitation brought together participants from 12 European and North American laboratories [Ebinghaus et al., 1999].
• Ongoing studies of methane and carbon dioxide (since 1992) include the collection of flask samples which are analysed for isotopic constitution to try to identify their origin from fossil fuels or more recent organic processes [Bousquet et al., 1997].
• Since the late 1980s, a NOAA collaborative trace gas (CO2 and isotopes) long-term flask sampling program has been in operation at Mace Head.
• From 1998-2000, Mace Head has been the host location for the EU-funded program, New Particle Formation and Fate in the Coastal Environment (PARFORCE), bringing with it continuous measurements of ultrafine particle characteristics.

Atmospheric Research Activities

NUI-Galway scientists have specialized in the study of particulate matter in the atmosphere including the very small Aitken or condensation nuclei (CN) formed by combustion processes and gaseous reactions, the larger particles or cloud condensation nuclei (CCN) ) on which cloud droplets form, black carbon /soot, and aerosol particles of organic origin.

Research activities at Mace Head are divided into the following main areas:

Microphysical and physico-chemical properties of atmospheric aerosols

A wide range of aerosol particle sizing and mass measurement equipment is used to study the microphysical and physico-chemical properties of atmospheric aerosols at Mace Head. Begun in 1987, this work is in collaboration with the US NSF-funded Air Ocean Chemistry Experiment (AEROCE), which has had its primary eastern Atlantic site located at Mace Head from 1988­1994 to study biogeochemical cycles in the North Atlantic.

Research includes studies of aerosol particle size and mass distribution [Jennings et al., 1991]. While aerosol volatility at Mace Head was first reported by Jennings and O'Dowd [1990], more emphasis was then placed on extension of the technique to the inference of sea-salt particles. More recent work [Jennings et al., 1997a] has included number concentration of inferred aerosol chemical constituents including elemental carbon [Jennings et al., 1994].

Nucleation of atmospheric particles in the coastal environment

Rapid particle nucleation events are being studied under a wide variety of conditions at Mace Head. The newly funded European Union Environment and Climate Program, "New Particle Formation and Fate in the Coastal Environment" (PARFORCE), investigates the processes which control and promote new-particle nucleation in the marine boundary layer. Nucleation of new, ultrafine aerosol particles has been observed in the clean marine coastal environment under a variety of conditions at Mace Head [O'Dowd et al., 1998]. These nucleation events were observed to occur almost daily, lasting up to several hours, and were found to be linked to the occurrence of low tides. Peak particle concentrations achieved during these clean-air nucleation events can approach 1,000,000 cm-3.

Cloud condensation nuclei (CCN) measurements

Long-term measurement of cloud condensation nuclei (CCN)-which have as yet an un-quantified influence on the radiative properties of cloud, and hence on global climate-have been ongoing at Mace Head since January 1994. The station's CCN counter was manufactured by DH Associates (model M1) and compares well (within 15%) to a CSIRO custom built counter [Gras et al., 1996]. Air mass and meteorological effects on the CCN population are being studied. Recent work has found evidence for enhanced CCN concentrations with increasing wind speed [Jennings et al., 1997b].
Aerosol radiative properties

Field research at Mace Head is also directed to the measurement of black carbon absorption (and mass concentration), ongoing since 1989 [Jennings et al., 1993; Cooke et al., 1997]. Seasonal and air mass influence on black carbon levels are being investigated. Measurements of aerosol scattering coefficients were recently (January 1997) initiated at Mace Head. This permits the determination of aerosol single scattering albedo. The direct measurement of particulate mass concentration for particle diameter <2.5 mm (PM2.5) allows the determination of the mass scattering efficiency, a.

Trace gases research at Mace Head

Since 1987, continuous measurements of chlorofluorocarbons (CFC's)-CFC-11, CFC-12, CH3CCl3, CFC-113, as well as CCl4, CH4, N2O, CO, and O3-have been made at Mace Head as part of the Global Atmospheric Gases Experiment (GAGE) [Simmonds et al., 1997]. The GAGE program was superseded in 1995 by Advanced GAGE (AGAGE). T.G. Spain has been maintaining the operation of the GAGE and AGAGE research program at Mace Head. Measurement of CFC substitutes-HFC's and HCFC's-by an automated gas chromatograph-mass spectrometer was initiated in 1995. In addition, a flask sampling network for CH4 isotope measurements has been undertaken by NUI-Galway and other EU participants [Nisbet et al., 1998].

Since 1992 a collaborative CO2 measurement program has been underway with CNRS, Gif sur Yvette, France and the University of Bristol [Biraud et al., 1999]. The work has been extended to include radon and CO2 isotope measurements under the EU ESCOBA research project.

Additional Research Programs and supporting activities

Intensive field research at Mace Head has included the UK Community Research Programme of the Natural Environment Research Council:

Atmospheric Chemistry Studies in the Oceanic Environment (ACSOE) which centred its ground based measurements at the station over the periods June­August 1996 and April­May 1997 for two of its consortia: OXICOA (OXIdizing Capacity of the Ocean Atmosphere) and MAGE ( Marine Aerosol and Gas Exchange).

In September 1995, Mace Head was host to the first international workshop, involving some 12 laboratories from North America and Europe, for the field intercomparison of measurement techniques for atmospheric mercury species in ambient air and precipitation. Since then, continuous total gaseous mercury measurements have been taken at Mace Head as a function of air mass and meteorological conditions and are being analysed.

More details on the Mace Head Station and its research activities may be found on the web site.

References

1. Biraud, S., P. Ciais, M. Ramonet, P.G., Simmonds, V. Kazan, P. Monfray, T.G., Spain, and S. G. Jennings, European greenhouse gas emissions estimated from continuous atmospheric measurements at Mace Head, Ireland, J. Geophys. Res., 1999.
2. Nisbet, E.G., I. Levin, G.P. Wyers, and A.F. Roddy, Quantification of the west European methane emissions budget by atmospheric measurements, Final Report EUR 17511 EN, Office for official publications of the European Communities, L-2985 Luxembourg, 24 pp., 1998.
3. Bousquet et al., Atmospheric CO2 concentration variations recorded at Mace Head, Ireland from 1992 to 1994, Phys. Chem. Earth, 21, 447-481, 1997.
4. Broadgate, W.B. et al., OXICOA Eastern Atlantic Spring Experiment 97, MAGE Eastern Atlantic Experiment 97, Mace Head Data Book, School of Environmental Sciences, University of East Anglia, Norwich, 1997 (ACSOE Publication No. ACR028), 1998.
5. Cooke, W.F., S.G. Jennings, and T.G. Spain, Black carbon measurements at Mace Head, 1989-1996, J. Geophys. Res.,102, 25,339-25,346, 1997.
6. Ebinghaus et al., International field intercomparison measurements of atmospheric mercury species at Mace Head, Ireland, Atmos. Environ. (in press).
7. Gras, J.L., S.G. Jennings, and M. Geever, CCN determination comparing counters with single drop counting and photometric detectors at Mace Head, Ireland, Idojaras, 100, 171-182, 1996.
8. Jennings, S.G., and C.D. O'Dowd, Volatility of aerosol at Mace Head on the west coast of Ireland, J. Geophys. Res., 95, 13,937-13,948, 1990.
9. Jennings, S.G., C.D. O'Dowd, T.C. O'Connor, and F.M. McGovern, Physical characteristics of the ambient aerosol at Mace Head, Atmos. Environ., 25A, 557-562, 1991.
10. Jennings, S.G., F.M. McGovern, and W.F. Cooke, Mass concentration of aerosol black carbon at Mace Head on the west coast of Ireland, Atmos. Environ., 27A, 1229-1239, 1993.
11. Jennings, S.G., C.D. O'Dowd, W.F. Cooke, P.J. Sheridan, and H. Cachier, Volatility of elemental carbon, Geophys. Res. Lett., 21, 1719-1722, 1994.
12. Jennings, S.G., M. Geever, F.M. McGovern, J. Francis, T.G. Spain, and T. Donaghy, Microphysical and physico-chemical characterisation of atmospheric aerosol at Mace Head, Atmos. Environ., 31, 2795-2808, 1997a.
13. Jennings, S.G., M. Geever, and T.C. O'Connor, Coastal CCN measurements at Mace Head with enhanced concentrations in strong winds, Atmos. Res., 46, 243-252, 1997b.
14. O'Dowd, C.D., M. Geever, M.K. Hill, S.G. Jennings, M.H. Smith, New particle formation: Spatial scales and nucleation rates in the coastal environment, 25, 1661-1664, Geophys. Res. Letts, 1998.
15. Prospero, J.M., The Atmosphere/Ocean Experiment (AEROCE): An overview, EOS, Transactions, AGU, 78, F122-F123, 1997.
16. Simmonds P.G. et al., Long-term trends in concentrations of halocarbons and radiatively active gases in Atlantic and European air masses monitored at Mace Head, Ireland from 1987 to 1995, Atmos. Environ., 30, 4041-4063, 1996.
17. Simmonds P.G., S. Seuring, G. Nickless, and R.G. Derwent, Segregation and interpretation of ozone and carbon monoxide measurements by air mass origin at the TOR station Mace Head, Ireland from 1987 to 1995, J. Atmos. Chem., 28, 45-59, 1997.