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

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

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


Abstract


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

Trends over a 20-year period from 1987 to 2007 in surface ozone at the atmospheric research sta Trends over a 20-year period from 1987 to 2007 in surface ozone at the atmospheric research sta

Date added: 08/07/2007
Date modified: 07/23/2009
Filesize: 205.45 kB

Derwent, R. G., Simmonds, P. G., Manning, A. J., and Spain, T. G.: Trends over a 20-year
period from 1987–2007 in surface ozone at the atmospheric research station, Mace Head,
15 Ireland, Atmos. Environ., 41, 9091–9098, 2007.


Abstract


Hourly measurements of baseline ozone at the Mace Head Atmospheric Research Station on the Atlantic Ocean coast of Ireland are observed when unpolluted air masses are advected to the station from across the North Atlantic Ocean. Monthly mean ozone mixing ratios in baseline air masses have risen steadily during the 1980s and 1990s reaching unprecedented levels during the early months of 1999. During the 2000s, baseline ozone mixing ratios have shown evidence of decline and stabilisation. Over the entire 20-year 1987-2007 period, the trend in annual baseline ozone has been +0.31±0.12(2-σ)ppbyear-1 and is highly statistically significant. Trends have been highest in the spring months and lowest in the summer months, producing a significant increase in the amplitude of the seasonal cycle. Over the shorter 1995-2007 period, we demonstrate how the growth to peak in 1999 and the subsequent decline have been driven by boreal biomass burning events during 1998/1999 and 2002/2003. The 2000s have been characterised by relatively constant baseline ozone and CH4 levels and these may be a reasonable guide to future prospects, at least in the short term.

 

The phase-in and phase-out of European emissions of HCFC-141b and HCFC-142b .... at Mace Head, The phase-in and phase-out of European emissions of HCFC-141b and HCFC-142b .... at Mace Head,

Date added: 08/07/2007
Date modified: 07/23/2009
Filesize: 536.66 kB

DERWENT R. G. ; SIMMONDS P. G.; GREALLY B. R.  ; O'DOHERTY S. ; MCCULLOCH A. ; MANNING A. ; REIMANN S. ; FOLINI D. ; VOLLMER M. K.   , The phase-in and phase-out of european emissions of HCFC-141b and HCFC-142b under the Montreal Protocol : Evidence from observations at Mace Head, Ireland and Jungfraujoch, Switzerland from 1994 to 2004, Atmospheric Environment , 41, 4, pg 757-767 (2007)


Abstract

 

The mixing ratios of HCFC-141b (1,1-dichlorofluoroethane) and HCFC-142b (1-chloro-1,1-difluoroethane) have been rising steadily in baseline air at Mace Head, Ireland over the 10-year period from 1994 to 2004. These HCFCs are widely used replacements for the chlorofluorocarbons phased out under the Montreal Protocol and its subsequent amendments. Analysis of the HCFC content of regionally-polluted air arriving at Mace Head from the European continent shows that European emissions reached a peak during 2000-2001 and have declined subsequently, following the phase-out in their usage. European emissions of HCFC-141b have been further constrained by observations at the High-Alpine Jungfraujoch site. The reductions are consistent with the phase-out of HCFC production and use from the year 2001 onwards mandated by European regulations designed to exceed the requirements of the Montreal Protocol.

 

Seasonal cycle of N2O Analysis of data Seasonal cycle of N2O Analysis of data

Date added: 08/06/2007
Date modified: 07/23/2009
Filesize: 599.77 kB

Jiang, X., W. L. Ku, R.-L. Shia, Q. Li, J. W. Elkins, R. G. Prinn, and Y. L. Yung (2007), Seasonal cycle of N2O: Analysis of data, Global Biogeochem. Cycles, 21, GB1006, doi:10.1029/2006GB002691


Abstract


We carried out a systematic study of the seasonal cycle and its latitudinal variation in the nitrous oxide (N2O) data collected by National Oceanic and Atmospheric Administration–Global Monitoring Division (NOAA-GMD) and the Advanced Global Atmospheric Gases Experiment (AGAGE). In order to confirm the weak seasonal signal in the observations, we applied the multitaper method for the spectrum analysis and studied the stations with significant seasonal cycle. In addition, the measurement errors must be small compared with the seasonal cycle. The N2O seasonal cycles from seven stations satisfied these criteria and were analyzed in detail. The stations are Alert (82°N, 62°W), Barrow (71°N, 157°W), Mace Head (53°N, 10°W), Cape Kumukahi (19°N, 155°W), Cape Matatula (14°S, 171°W), Cape Grim (41°S, 145°E) and South Pole (90°S, 102°W). The amplitude (peak to peak) of the seasonal cycle of N2O varies from 0.29 ppb (parts-per-billion by mole fraction in dry air) at the South Pole to 1.15 ppb at Alert. The month at which the seasonal cycle is at a minimum varies monotonically from April (South Pole) to September (Alert). The seasonal cycle in the Northern Hemisphere shows the influence of the stratosphere; the seasonal cycle of N2O in the Southern Hemisphere suggests greater influence from surface sources. Preliminary estimates are obtained for the magnitude of the seasonally varying sources needed to account for the observations.

 

Isotope values of atmospheric halocarbons and hydrocarbons from Irish urban, rural, and marine Isotope values of atmospheric halocarbons and hydrocarbons from Irish urban, rural, and marine

Date added: 08/06/2007
Date modified: 07/24/2009
Filesize: 750 kB

Redeker, K. R., S. Davis, and R. M. Kalin (2007), Isotope values of atmospheric halocarbons and hydrocarbons from Irish urban, rural, and marine locations, J. Geophys. Res., 112, D16307, doi:10.1029/2006JD007784.


Abstract

 

Stable carbon isotope ratios for 37 hydrocarbon, CFC and halocarbon compounds were determined over the course of 1 year (86 samples) from the urban Belfast environment, Northern Ireland (NI). A smaller number of samples were collected from rural locations at Crossgar and Hillsborough, NI, and one marine location at Mace Head, Republic of Ireland. Source δ 13C “signatures” suggest that <C5 alkanes are most likely derived from natural gas and liquid petroleum gas while >C5 alkanes and ≥C4 alkenes are most likely derived from vehicle emissions. C3–C5 hydrocarbons show significant enrichment of δ 13C with iso-alkanes < n-alkanes < alkenes < alkynes. There is also significant enrichment of δ 13C from propane to n-butane to n-pentane. There is no significant separation between n-pentane, n-hexane, n-heptane or methyl-butane, methyl pentane and methyl hexanes. Calculated hydroxyl reaction kinetic isotope effects and subsequent δ 13C enrichment are insufficient to explain shifts in isotopic ratio relative to concentration for all compounds as is differences in origin of air mass. Very few compounds show significant diurnal shifts; however, alkanes and ≥C4 alkenes demonstrate consistent enrichment of isotopic ratios when summer samples are compared to winter samples. Benzene is the sole compound measured that appears to become more depleted in δ 13C when summer samples are compared against winter samples. Urban air, sampled at Belfast, which has originated in Europe shows enriched values for hydrocarbons while air which has originated in the Arctic Ocean is most similar to marine air off the Atlantic, sampled at Mace Head, Ireland.

 

Interannual and seasonal variability in atmospheric N 2 O Interannual and seasonal variability in atmospheric N 2 O

Date added: 08/06/2007
Date modified: 07/24/2009
Filesize: 673.42 kB

Nevison, C. D., N. M. Mahowald, R. F. Weiss, and R. G. Prinn (2007), Interannual and seasonal variability in atmospheric N2O, Global Biogeochem. Cycles, 21, GB3017, doi:10.1029/2006GB002755.


Abstract


The increase in atmospheric N2O observed over the last century reflects large-scale human perturbations to the global nitrogen cycle. High-precision measurements of atmospheric N2O over the last decade reveal subtle signals of interannual variability (IAV) superimposed upon the more prominent growth trend. Anthropogenic sources drive the underlying growth in N2O, but are probably too monotonic to explain most of the observed IAV. The causes of both seasonal and interannual variability in atmospheric N2O are explored on the basis of comparisons of a 1993–2004 atmospheric transport simulation to observations of N2O at five stations of the Advanced Global Atmospheric Gases Experiment (AGAGE). The complementary tracers chlorofluorocarbons (CFCs) 11 and 12 and SF6 also are examined. The model simulation does not include a stratospheric sink and thus isolates the effects of surface sources and tropospheric transport. Both model and observations yield correlations in seasonal and interannual variability among species, but only in a few cases are model and observed variability correlated to each other. The results suggest that tropospheric transport contributes substantially to observed variability, especially at Samoa station. However, some features of observed variability are not explained by the model simulation and appear more consistent with a stratospheric influence. At Mace Head, Ireland, N2O and CFC growth rate anomalies are weakly correlated to IAV in polar winter lower stratospheric temperature, a proxy for the strength of the mean meridional stratospheric circulation. Seasonal and interannual variability in the natural sources of N2O may also contribute to observed variability in atmospheric N2O.

 

Interannual and seasonal variability in atmospheric N 2 O Interannual and seasonal variability in atmospheric N 2 O

Date added: 08/06/2007
Date modified: 07/02/2009
Filesize: 673.42 kB

Nevison, C. D., N. M. Mahowald, R. F. Weiss, and R. G. Prinn (2007), Interannual and seasonal variability in atmospheric N2O, Global Biogeochem. Cycles, 21, GB3017, doi:10.1029/2006GB002755.


Abstract


The increase in atmospheric N2O observed over the last century reflects large-scale human perturbations to the global nitrogen cycle. High-precision measurements of atmospheric N2O over the last decade reveal subtle signals of interannual variability (IAV) superimposed upon the more prominent growth trend. Anthropogenic sources drive the underlying growth in N2O, but are probably too monotonic to explain most of the observed IAV. The causes of both seasonal and interannual variability in atmospheric N2O are explored on the basis of comparisons of a 1993–2004 atmospheric transport simulation to observations of N2O at five stations of the Advanced Global Atmospheric Gases Experiment (AGAGE). The complementary tracers chlorofluorocarbons (CFCs) 11 and 12 and SF6 also are examined. The model simulation does not include a stratospheric sink and thus isolates the effects of surface sources and tropospheric transport. Both model and observations yield correlations in seasonal and interannual variability among species, but only in a few cases are model and observed variability correlated to each other. The results suggest that tropospheric transport contributes substantially to observed variability, especially at Samoa station. However, some features of observed variability are not explained by the model simulation and appear more consistent with a stratospheric influence. At Mace Head, Ireland, N2O and CFC growth rate anomalies are weakly correlated to IAV in polar winter lower stratospheric temperature, a proxy for the strength of the mean meridional stratospheric circulation. Seasonal and interannual variability in the natural sources of N2O may also contribute to observed variability in atmospheric N2O.

 

Seasonal characteristics of the physicochemical properties of North Atlantic... Seasonal characteristics of the physicochemical properties of North Atlantic...

Date added: 08/06/2007
Date modified: 07/23/2009
Filesize: 725.93 kB

Yoon, Y. J., et al. (2007), Seasonal characteristics of the physicochemical properties of North Atlantic marine atmospheric aerosols, J. Geophys. Res., 112, D04206, doi:10.1029/2005JD007044.


Abstract


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

 

Marine Aerosol Production: a review of the current knowledge Marine Aerosol Production: a review of the current knowledge

Date added: 08/06/2007
Date modified: 07/02/2009
Filesize: 1.51 MB

O’Dowd, C.D., & G. de Leeuw, Marine Aerosol Production: a review of the current knowledge, , Phil. Trans. R. Soc. A, doi:10.1098/rsta.2007.2043, 2007


Abstract


The current knowledge in primary and secondary marine aerosol formation is reviewed. For primary marine aerosol source functions, recent source functions have demonstrated a significant flux of submicrometre particles down to radii of 20nm. Moreover, the source functions derived from different techniques up to 10μm have come within a factor of two of each other. For secondary marine aerosol formation, recent advances have identified iodine oxides and isoprene oxidation products, in addition to sulphuric acid, as contributing to formation and growth, although the exact roles remains to be determined. While a multistep process seems to be required, isoprene oxidation products are more likely to participate in growth and sulphuric acid is more likely to participate in nucleation. Iodine oxides are likely to participate in both nucleation and growth.

 

A Combined Organic-Inorganic sea-spray Source Function A Combined Organic-Inorganic sea-spray Source Function

Date added: 08/06/2007
Date modified: 07/27/2009
Filesize: 317.72 kB

O'Dowd, C. D., B. Langmann, S. Varghese, C. Scannell, D. Ceburnis, and M. C. Facchini (2008), A combined organic-inorganic sea-spray source function, Geophys. Res. Lett., 35, L01801, doi:10.1029/2007GL030331.


Abstract


This study presents a novel approach to develop a combined organic-inorganic sub-micron sea-spray source function for inclusion in large-scale models. It requires wind speed and surface ocean chlorophyll-a concentration as input parameters. The combined organic-inorganic source function is implemented in the REMOTE regional climate model and sea-spray fields are predicted with particular focus on the North East Atlantic. The model predictions using the new source functions compare well with observations of total sea-spray mass and organic carbon fraction in sea-spray aerosol. During winter (periods of low oceanic biological activity), sea-salt dominates the sea-spray mass while in summer (when biological activity is high), water soluble organic carbon contributes between 60–90% of the submicron sea-spray mass.

 

Regional model simulation of North Atlantic cyclones...response to increased sea surface temper Regional model simulation of North Atlantic cyclones...response to increased sea surface temper

Date added: 08/06/2007
Date modified: 07/06/2009
Filesize: 2.79 MB

Semmler, T., S. Varghese, R. McGrath, P. Nolan, S. Wang, P. Lynch, and C. O'Dowd (2008), Regional model simulation of North Atlantic cyclones: Present climate and idealized response to increased sea surface temperature, J. Geophys. Res., 113, D02107, doi:10.1029/2006JD008213.


Abstract


The influence of an increased sea surface temperature (SST) on the frequency and intensity of cyclones over the North Atlantic is investigated using two data sets from simulations with the Rossby Centre regional climate model RCA3. The model domain comprises large parts of the North Atlantic and the adjacent continents. RCA3 is driven by reanalysis data for May to December 1985–2000 at the lateral and lower boundaries, using SST and lateral boundary temperatures. A realistic interannual variation in tropical storm and hurricane counts is simulated. In an idealized sensitivity experiment, SSTs and boundary condition temperatures at all levels are increased by 1 K to ensure that we can distinguish the SST from other factors influencing the development of cyclones. An increase in the count of strong hurricanes is simulated. There is not much change in the location of hurricanes. Generally weaker changes are seen in the extratropical region and for the less extreme events. Increases of 9% in the count of extratropical cyclones and 39% in the count of tropical cyclones with wind speeds of at least 18 m/s are found.

 

European Emissions of HFC-365mfc, a Chlorine-Free Substitute for the Foam Blowing Agents HCFC-141b and CFC-11 European Emissions of HFC-365mfc, a Chlorine-Free Substitute for the Foam Blowing Agents HCFC-141b and CFC-11

Date added: 08/05/2007
Date modified: 07/24/2009
Filesize: 595.17 kB

European Emissions of HFC-365mfc, a Chlorine-Free Substitute for the Foam Blowing Agents HCFC-141b and CFC-11
Stemmler, K., Folini, D., Ubl, S., Vollmer, M.K., Reimann, S., O'Doherty, S., Greally, B.R., Simmonds, P.G., and Manning, A.J. Environ. Sci. Technol., 41, 4, 1145 - 1151, 2007,  10.1021/es061298h


Abstract


HFC-365mfc (1,1,1,3,3-pentafluorobutane) is an industrial chemical used for polyurethane foam blowing. From early 2003, HFC-365mfc has been commercially produced as a substitute for HCFC-141b, whose use in Europe has been banned since January 2004. We describe the first detection of HFC-365mfc in the atmosphere and report on a 2 year long record at the high Alpine station of Jungfraujoch (Switzerland) and the Atlantic coast station of Mace Head (Ireland). The measurements at Jungfraujoch are used to estimate the central European emissions of HFC-365mfc, HCFC-141b, and CFC-11. For HFC-365mfc, we estimate the central European emissions (Germany, France, Italy, Switzerland, The Netherlands, Belgium, and Luxembourg) in 2003 and 2004 as 400-500 tonnes year-1. These emissions are about one-third lower on a per capita basis than what we estimate from the Mace Head measurements for the total of Europe. The estimated emissions of HCFC-141b for central Europe are higher (i.e., 7.2-3.5 ktonnes year-1) with a decreasing trend in the period from 2000 to 2004. Residual emissions of CFC-11 are estimated at 2.4-4.7 ktonnes year-1 in the same time period. The Po Valley (northern Italy) appears to be a main source region for HFC-365mfc and for the former blowing agents HCFC-141b and CFC-11. In 2004, the emissions of HFC-365mfc arose from a wider region of Europe, which we attribute to an increased penetration of HFC-365mfc into the European market.

Observations of 1,1-difluoroethane (HFC-152a) at AGAGE and SOGE monitoring stations in 1994–2004 and derived global and regional emission estimates Observations of 1,1-difluoroethane (HFC-152a) at AGAGE and SOGE monitoring stations in 1994–2004 and derived global and regional emission estimates

Date added: 08/05/2007
Date modified: 07/23/2009
Filesize: 2.28 MB
Greally, B. R., et al. (2007), Observations of 1,1-difluoroethane (HFC-152a) at AGAGE and SOGE monitoring stations in 1994–2004 and derived global and regional emission estimates, J. Geophys. Res., 112, D06308, doi:10.1029/2006JD007527.

Abstract


Ground-based in situ measurements of 1,1-difluoroethane (HFC-152a, CH3CHF2) which is regulated under the Kyoto Protocol are reported under the auspices of the AGAGE (Advanced Global Atmospheric Gases Experiment) and SOGE (System of Observation of halogenated Greenhouse gases in Europe) programs. Observations of HFC-152a at five locations (four European and one Australian) over a 10 year period were recorded. The annual average growth rate of HFC-152a in the midlatitude Northern Hemisphere has risen from 0.11 ppt/yr to 0.6 ppt/yr from 1994 to 2004. The Southern Hemisphere annual average growth rate has risen from 0.09 ppt/yr to 0.4 ppt/yr from 1998 to 2004. The 2004 average mixing ratio for HFC-152a was 5.0 ppt and 1.8 ppt in the Northern and Southern hemispheres, respectively. The annual cycle observed for this species in both hemispheres is approximately consistent with measured annual cycles at the same locations in other gases which are destroyed by OH. Yearly global emissions of HFC-152a from 1994 to 2004 are derived using the global mean HFC-152a observations and a 12-box 2-D model. The global emission of HFC-152a has risen from 7 Kt/yr to 28 Kt/yr from 1995 to 2004. On the basis of observations of above-baseline elevations in the HFC-152a record and a consumption model, regional emission estimates for Europe and Australia are calculated, indicating accelerating emissions from Europe since 2000. The overall European emission in 2004 ranges from 1.5 to 4.0 Kt/year, 5–15% of global emissions for 1,1-difluoroethane, while the Australian contribution is negligible at 5–10 tonnes/year, <0.05% of global emissions.

Optimal estimation of the soil uptake rate of molecular hydrogen from the Advanced Global Atmospheric Gases Experiment and other measurements Optimal estimation of the soil uptake rate of molecular hydrogen from the Advanced Global Atmospheric Gases Experiment and other measurements

Date added: 08/05/2007
Date modified: 07/23/2009
Filesize: 683.98 kB
Xiao, X., et al. (2007), Optimal estimation of the soil uptake rate of molecular hydrogen from the Advanced Global Atmospheric Gases Experiment and other measurements, J. Geophys. Res., 112, D07303, doi:10.1029/2006JD007241.

Abstract


Hydrogen (H2), a proposed clean energy alternative, warrants detailed investigation of its global budget and future environmental impacts. The magnitudes and seasonal cycles of the major (presumably microbial) soil sink of hydrogen have been estimated from high-frequency in situ AGAGE H2 observations and also from more geographically extensive but low-frequency flask measurements from CSIRO and NOAA-GMD using the Kalman filter in a two-dimensional (2-D) global transport model. Hydrogen mole fractions exhibit well-defined seasonal cycles in each hemisphere with their phase difference being only about 3 months. The global production rate of H2 is estimated to be 103 ± 10 Tg yr−1 with only a small estimated interannual variation. Soil uptake (84 ± 8 Tg yr−1) represents the major loss process for H2 and accounts for 81% of the total destruction. Strong seasonal cycles are deduced for the soil uptake of H2. The soil sink is a maximum over the northern extratropics in summer and peaks only 2 to 3 months earlier in the Northern Hemisphere than in the Southern Hemisphere. Oxidation by tropospheric OH (18 ± 3 Tg yr−1) accounts for 17% of the destruction, with the remainder due to destruction in the stratosphere. The calculated global burden is 191 ± 29 Tg, indicating an overall atmospheric lifetime of 1.8 ± 0.3 years. Hydrogen in the troposphere (149 ± 23 Tg burden) has a lifetime of 1.4 ± 0.2 years.

The role of VOC oxidation products in continental new particle formation The role of VOC oxidation products in continental new particle formation

Date added: 08/01/2007
Date modified: 07/08/2009
Filesize: 693.16 kB

Laaksonen, A., M. Kulmala, C.D. O’Dowd, J. Joutsensaari, P. Vaattovaara, S. Mikkonen, K.E.J. Lehtinen, L. Sogacheva, M. Dal Maso, P. Aalto, T. Petäjä, A. Sogachev, Y. J. Yoon, H. Lihavainen, D. Nilsson, M. C. Facchini, F. Cavalli, S. Fuzzi, T. Hoffmann, F. Arnold, M. Hanke, K. Sellegri, B. Umann, W Junkermann, H. Coe, J. D. Allan, M. R. Alfarra, D.R. Worsnop, M.-L. Riekkola, T. Hyötyläinen and Y Viisanen., The role of VOC oxidation products in continental new particle formation, Atmos. Chem. And Phys. Discuss., 2007.


Abstract


Aerosol physical and chemical properties and trace gas concentrations were measured during the QUEST field campaign in March–April, 2003, in Hyytiälä, Finland. Our aim was to understand the role of oxidation products of VOC's such as mono- and sesquiterpenes in atmospheric nucleation events. Particle chemical compositions were measured using the Aerodyne Aerosol Mass Spectrometer, and chemical compositions of aerosol samples collected with low-pressure impactors and a high volume sampler were analysed using a number of techniques. The results indicate that during and after new particle formation, all particles larger than 50 nm in diameter contained similar organic substances that are likely to be mono- and sesquiterpene oxidation products. The oxidation products identified in the high volume samples were shown to be mostly aldehydes. In order to study the composition of particles in the 10–50 nm range, we made use of Tandem Differential Mobility Analyzer results. We found that during nucleation events, both 10 and 50 nm particle growth factors due to uptake of ethanol vapour correlate strongly with gas-phase monoterpene oxidation product (MTOP) concentrations, indicating that the organic constituents of particles smaller than 50 nm in diameter are at least partly similar to those of larger particles. We furthermore showed that particle growth rates during the nucleation events are correlated with the gas-phase MTOP concentrations. This indicates that VOC oxidation products may have a key role in determining the spatial and temporal features of the nucleation events. This conclusion was supported by our aircraft measurements of new 3–10 nm particle concentrations, which showed that the nucleation event on 28 March 2003, started at the ground layer, i.e. near the VOC source, and evolved together with the mixed layer. Furthermore, no new particle formation was detected upwind away from the forest, above the frozen Gulf of Bothnia.

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

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

Abstract


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

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

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

Abstract

 

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

Primary marine aerosol emissions size resolved eddy covariance measurements with estimates of the sea salt and organic carbon fractions Primary marine aerosol emissions size resolved eddy covariance measurements with estimates of the sea salt and organic carbon fractions

Date added: 08/01/2007
Date modified: 07/23/2009
Filesize: 1.75 MB

Nilsson, E.D., E. M. Mårtensson, J. S. Van Ekeren, G. de Leeuw, M. Moerman, and C. O'Dowd, Primary marine aerosol emissions: size resolved eddy covariance measurements with estimates of the sea salt and organic carbon fractions, Atmos. Chem. Phys. Discuss., 7, 13345-13400, 2007


Abstract


Primary marine aerosol fluxes were measured using eddy covariance (EC), a condensation particle counter (CPC) and an optical particle counter (OPC) with a heated inlet. The later was used to discriminate between sea salt and total aerosol. Measurements were made from the 25 m tower at the research station Mace Head at the Irish west coast, May to September 2002. The aerosol fluxes were dominated by upward fluxes, sea spray from bubble bursting at the ocean surface. The sea salt aerosol number emissions increased two orders of magnitude with declining diameter from 1 to 0.1 μm where it peaked at values of 105 to 107 particles m−2s−1. The sea salt emissions increased at all sizes in the wind range 4 to 22 ms−1, in consistency with a power function of the wind speed. The sea salt emission data were compared to three recent sub micrometer sea salt source parameterisations. The best agreement was with Mårtensson et al. (2003), which appear to apply from 0.1 to 1.1 μm diameters in temperate water (12°C) as well as tropical water (25°C). The total aerosol emissions were independent of the wind speed below 10 ms−1, but increased with the wind above 10 ms−1. The aerosol volume emissions were larger for the total aerosol than for the sea salt at all wind speeds, while the sea salt number emissions approached the total number emissions at 15 ms−1. It is speculated that this is caused by organic carbon in the surface water that is depleted at high wind speeds. The data are consistent with an internal aerosol mixture of sea salt, organic carbon and water. Using the aerosol model by Ellison et al. (1999) (a mono-layer of organic carbon surrounding a water-sea-salt brine) we show that the total and sea salt aerosol emissions are consistent. This predict that the organic carbon fraction increase with decreasing diameter from a few % at 1 μm over 50% at about 0.5 μm to about 90% at 0.1 μm, in consistency with simultaneous chemical data by Cavalli et al. (2004). The combined models of Mårtensson et al. (2003) and Ellison et al. (1999) reproduce the observed total aerosol emissions and offer an approach to model the organic sea spray fraction.

Elemental and organic carbon in PM10 a one year measurement campaign within the European Monitoring and Evaluation Programme EMEP Elemental and organic carbon in PM10 a one year measurement campaign within the European Monitoring and Evaluation Programme EMEP

Date added: 08/01/2007
Date modified: 07/27/2009
Filesize: 2.18 MB

Yttri, K.E., W. Aas, A. Bjerke, J.N. Cape, F. Cavalli, D. Ceburnis, C. Dye, L. Emblico, M.C. Facchini, C. Forster, J.E. Hanssen, S.G. Jennings, W. Maenhaut, J.P. Putaud, and K. Torseth, Elemental and organic carbon in PM10: a one year measurement campaign within the European Monitoring and Evaluation Programme EMEP, Atmos. Chem. Phys., 7, 5711-5725, 2007.


Abstract


In the present study, ambient aerosol (PM10) concentrations of elemental carbon (EC), organic carbon (OC), and total carbon (TC) are reported for 12 European rural background sites and two urban background sites following a one-year (1 July 2002–1 July 2003) sampling campaign within the European Monitoring and Evaluation Programme, EMEP http://www.emep.int/). The purpose of the campaign was to assess the feasibility of performing EC and OC monitoring on a regular basis and to obtain an overview of the spatial and seasonal variability on a regional scale in Europe.

Analyses were performed using the thermal-optical transmission (TOT) instrument from Sunset Lab Inc., operating according to a NIOSH derived temperature program. The annual mean mass concentration of EC ranged from 0.17±0.19 μg m−3 (mean ± SD) at Birkenes (Norway) to 1.83±1.32 μg m−3 at Ispra (Italy). The corresponding range for OC was 1.20±1.29 μg m−3 at Mace Head (Ireland) to 7.79±6.80 μg m−3 at Ispra. On average, annual concentrations of EC, OC, and TC were three times higher for rural background sites in Central, Eastern and Southern Europe compared to those situated in the Northern and Western parts of Europe. Wintertime concentrations of EC and OC were higher than those recorded during summer for the majority of the sites. Moderate to high Pearson correlation coefficients (rp) (0.50–0.94) were observed for EC versus OC for the sites investigated. The lowest correlation coefficients were noted for the three Scandinavian sites: Aspvreten (SE), Birkenes (NO), and Virolahti (FI), and the Slovakian site Stara Lesna, and are suggested to reflect biogenic sources, wild and prescribed fires. This suggestion is supported by the fact that higher concentrations of OC are observed for summer compared to winter for these sites. For the rural background sites, total carbonaceous material accounted for 30±9% of PM10, of which 27±9% could be attributed to organic matter (OM) and 3.4±1.0% to elemental matter (EM). OM was found to be more abundant than SO42- for sites reporting both parameters.

Concentrations and fluxes of aerosol particles during the LAPBIAT measurement campaign at Värriö fie Concentrations and fluxes of aerosol particles during the LAPBIAT measurement campaign at Värriö fie

Date added: 08/01/2007
Date modified: 07/10/2009
Filesize: 2.65 MB

Ruuskanen, T.M., M. Kaasik, P. P. Aalto, U. Hõrrak, M. Vana, M. Mårtensson, Y. J. Yoon, P. Keronen, D. Nilsson, C. O’Dowd, M. Noppel, T. Alliksaar, J. Ivask, M. Sofiev, M. Prank, M. Kulmala, Concentrations and fluxes of aerosols particles during the LAPBIAT measurement campaign in the Varrio field station. Atmos. Chem. And Phys., 7, 3683–3700, 2007.


Abstract

 

The LAPBIAT measurement campaign took place in the V¨arri¨o SMEAR I measurement station located in Eastern
Lapland in the spring of 2003 between 26 April and 11 May. In this paper we describe the measurement campaign,
concentrations and fluxes of aerosol particles, air ions and trace gases, paying special attention to an aerosol particle
formation event broken by a air mass change from a clean Arctic air mass with new particle formation to polluted one
approaching from industrial areas of Kola Peninsula, Russia, lacking new particle formation. Aerosol particle number
flux measurements show strong downward fluxes during that time. Concentrations of coarse aerosol particles were  high for 1–2 days before the nucleation event (i.e. 28–29 April), very low immediately before and during the observed aerosol particle formation event (30 April) and increased moderately from the moment of sudden break of the event. In general particle deposition measurements based on snow samples show the same changes. Measurements of the mobility distribution of air ions showed elevated concentrations of intermediate air ions during the particle formation event. We estimated the growth rates in the nucleation mode size range. For particles <10 nm, the growth rate increases with size on 30 April. Dispersion modelling made with model SILAM support the conclusion that the nucleation event was interrupted by an outbreak of sulphate-rich air mass in the evening of 30 April that originated from the industry at Kola Peninsula.

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

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

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


Abstract


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

.

Light scattering properties of sea-salt aerosol particle inferred from modeling studies and ground-b Light scattering properties of sea-salt aerosol particle inferred from modeling studies and ground-b

Date added: 09/22/2006
Date modified: 07/13/2009
Filesize: 689.42 kB

Chamaillard, K., Kleefeld, C., Jennings, S.G., Ceburnis, D. & O’Dowd, C.D., Light scattering properties of sea-salt aerosol particle inferred from modeling studies and ground-based measurements. Journal of Quantitative Spectroscopy & Radiative Transfer, vol 101, pp. 498-511, 2006.


Abstract

 

Direct climate radiative forcing depends on the aerosol optical depth t, the single scattering albedo $, and the up-scatter
fraction b; these quantities are functions of the refractive index of the particles, their size relative to the incident
wavelength, and their shape. Sea-salt aerosols crystallize into cubic shapes or in agglomerates of cubic particles under low relative humidity conditions. The present study investigates the effects of the shape of dried sea-salt particles on the
detection of light scattering from the particles. Ground-based measurements of scattering and backscattering coefficients have been performed with an integrating nephelometer instrument for a wavelength l ¼ 0:55 mm. The measurements are compared to two models: the Mie theory assuming a spherical shape for the particles and the Discrete Dipole Approximation (DDA) model for the hypothesis of cubic shape of the sea-salt aerosols. The comparison is made accurately by taking into account the actual range of the scattering angles measured by the nephelometer in both models that is from 71 to 1701 for the scattering coefficient and from 901 to 1701 for the backscattering coefficient. Modeled scattering and backscattering coefficients increase for nonspherical particles compared to spherical shape of particles with diameter larger than about 1 mm. However, the comparison of the modeling results with the measurements gives best agreement for particles diameter less than about 1 mm. The size distribution of the particles is measured with two instruments with different size bins: an electrical low-pressure impactor (ELPI) and an aerodynamic particle sizer (APS). It is found that the size of the bins of the instruments to determine the number concentration of the particles in accordance with their diameter is critical in the comparison of measurements with modeling.

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

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

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


Abstract


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

Long-term changes in tropospheric ozone Long-term changes in tropospheric ozone

Date added: 08/07/2006
Date modified: 07/24/2009
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Oltmans, S. J., et al. (2006), Long-term changes in tropospheric ozone, Atmos. Environ.,
40, 3156-3173


Abstract

In this review we attempt to critically evaluate the availability of reliable tropospheric ozone measurements suitable for long-term trend analysis. The focus is on large-scale changes deduced from measurements, which are used for comparison with numerical simulations of the tropospheric ozone cycle. These are required to quantify the influence of anthropogenic ozone precursor emission changes on climate. Long-term tropospheric ozone measurements show that ozone over Europe has increased by more than a factor of two between World War II and the early 1990s which is consistent with the large increase in anthropogenic ozone precursor emissions in the industrialized world. However, the further increase in background ozone over Europe and North America since the early 1990s cannot be solely explained by regional ozone precursor changes because anthropogenic ozone precursor emissions decreased in the industrialized countries as consequence of air pollution legislation. Measurements also indicate large increases in ozone in the planetary boundary layer over the tropical Atlantic since the late 1970s, which have been attributed to large increases in fossil fuel related emissions. Measurements at southern midlatitudes, which are limited in number, show a moderate increase in tropospheric ozone since the middle of the 1990s.

 

External influences on Europe's air quality Baseline methane, carbon monoxide and ozone from 19 External influences on Europe's air quality Baseline methane, carbon monoxide and ozone from 19

Date added: 08/07/2006
Date modified: 07/24/2009
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Derwent, RG, Simmonds, PG, O'Doherty, S, et al , External influences on Europe''s air quality: Baseline methane, carbon monoxide and ozone from 1990 to 2030 at Mace Head, Ireland, ATMOS ENVIRON, 2006, Vol: 40, Pages: 844 - 855, ISSN: 1352-2310


Abstract


A global 3-D chemistry-transport model STOCHEM has been employed to study trends in the mole fractions of methane, carbon monoxide and ozone in baseline air masses entering Europe from the Atlantic Ocean over the period from 1990 to 2030. With a range of emission scenarios for man-made ozone precursor emission sources available, a wide range of model trends were predicted for the period up to 2030. In the scenario based on current planned air pollution controls, IIASA CLE, methane shows a strong upward trend, ozone shows a weaker upward trend, and carbon monoxide is approximately flat in baseline air masses. In one of the more pessimistic IPCC SRES scenarios, A2, all three gases show future increases. However, in the scenario based on maximum feasible emission reductions, IIASA MFR all three trace gases decline. By 2030, projected climate change reduces the growth in CH4, but has insignificant effects on baseline CO and O3 in these simulations. Global or hemispheric ozone precursor emissions and their controls exert a potentially large external influence on Europe’s air quality. This influence is currently not taken into account in future European air quality policy formulation.
r 2005 Elsevier Ltd. All rights reserved.

(NAMBLEX). Overview of the campaign held at Mace Head,  Ireland, in summer 2002 (NAMBLEX). Overview of the campaign held at Mace Head, Ireland, in summer 2002

Date added: 08/06/2006
Date modified: 07/27/2009
Filesize: 9.65 MB

Heard, D. E., Read, K. A., Methven, J., Al-Haider, S., Bloss, W. J., Johnson, G. P., Pilling, M. J., Seakins, P. W., Smith, S. C., Sommariva, R., Stanton, J. C., Still, T. J., Ingham, T., Brooks, B., De Leeuw, G., Jackson, A. V., McQuaid, J. B., Morgan, R., Smith, M. H., Carpenter, L. J., Carslaw, N., Hamilton, J., Hopkins, J. R., Lee, J. D., Lewis, A. C., Purvis, R. M., Wevill, D. J., Brough, N., Green, T., Mills, G., Penkett, S. A., Plane, J. M. C., Saiz-Lopez, A., Worton, D., Monks, P. S., Fleming, Z., Rickard, A. R., Alfarra, M. R., Allan, J. D., Bower, K., Coe, H., Cubison, M., Flynn, M., McFiggans, G., Gallagher, M., Norton, E. G., O'Dowd, C. D., Shillito, J., Topping, D., Vaughan, G., Williams, P., Bitter, M., Ball, S. M., Jones, R. L., Povey, I. M., O'Doherty, S., Simmonds, P. G., Allen, A., Kinnersley, R. P., Beddows, D. C. S., Dall'Osto, M., Harrison, R. M., Donovan, R. J., Heal, M. R., Jennings, S. G., Noone, C., and Spain, G.: The North Atlantic Marine Boundary Layer Experiment(NAMBLEX). Overview of the campaign held at Mace Head, Ireland, in summer 2002, Atmos. Chem. Phys., 6, 2241-2272, 2006.


Abstract


The North Atlantic Marine Boundary Layer Experiment (NAMBLEX), involving over 50 scientists from 12 institutions, took place at Mace Head, Ireland (53.32° N, 9.90° W), between 23 July and 4 September 2002. A wide range of state-of-the-art instrumentation enabled detailed measurements of the boundary layer structure and atmospheric composition in the gas and aerosol phase to be made, providing one of the most comprehensive in situ studies of the marine boundary layer to date. This overview paper describes the aims of the NAMBLEX project in the context of previous field campaigns in the Marine Boundary Layer (MBL), the overall layout of the site, a summary of the instrumentation deployed, the temporal coverage of the measurement data, and the numerical models used to interpret the field data. Measurements of some trace species were made for the first time during the campaign, which was characterised by predominantly clean air of marine origin, but more polluted air with higher levels of NOx originating from continental regions was also experienced. This paper provides a summary of the meteorological measurements and Planetary Boundary Layer (PBL) structure measurements, presents time series of some of the longer-lived trace species (O3, CO, H2, DMS, CH4, NMHC, NOx, NOy, PAN) and summarises measurements of other species that are described in more detail in other papers within this special issue, namely oxygenated VOCs, HCHO, peroxides, organo-halogenated species, a range of shorter lived halogen species (I2, OIO, IO, BrO), NO3 radicals, photolysis frequencies, the free radicals OH, HO2 and (HO2+Σ RO2), as well as a summary of the aerosol measurements. NAMBLEX was supported by measurements made in the vicinity of Mace Head using the NERC Dornier-228 aircraft. Using ECMWF wind-fields, calculations were made of the air-mass trajectories arriving at Mace Head during NAMBLEX, and were analysed together with both meteorological and trace-gas measurements. In this paper a chemical climatology for the duration of the campaign is presented to interpret the distribution of air-mass origins and emission sources, and to provide a convenient framework of air-mass classification that is used by other papers in this issue for the interpretation of observed variability in levels of trace gases and aerosols.

Marine particle nucleation Observation at Bodega Bay, California Marine particle nucleation Observation at Bodega Bay, California

Date added: 08/06/2006
Date modified: 07/24/2009
Filesize: 1.48 MB

Wen, J., Y. Zhao, and A. S. Wexler (2006), Marine particle nucleation: Observation at Bodega Bay, California, J. Geophys. Res., 111, D08207, doi:10.1029/2005JD006210.


Abstract


A TSI nano-SMPS was installed in a lab at Bodega Bay, about 50 m from the coastline and 5 m above sea level. On the basis of measurements conducted from June to December 2001 and from January to June 2003, we have observed two kinds of nucleation events, i.e., long-term (a few hours) and short-term (a few minutes) particle bursts. The long-term events mostly occur during daytime in the summer, lasting from 0.5 to 8 hours. Narrow spikes (short-term events) that occur year-round, both day and night, last only a few minutes to a half hour but contain particle number concentrations comparable to some of the long-term events. Wind direction and speed affect the occurrence and intensity of the particle burst. Nucleation mostly takes place during northwesterly onshore wind for both long- and short-term events, and the probability of nucleation occurrence is higher at higher wind speed. However, in contrast to what has been observed at Mace Head, Ireland, nucleation at Bodega Bay does not correlate with tidal height. Instead, the seasonal and interannual variations of ultrafine particle number concentration N3–10nm appear to correlate with ocean upwelling, a characteristic of currents along the west coast of the United States that brings up nutrients from subsurface waters, promoting plant productivity. Simultaneous measurements of nucleation at the coast and 1.6 km out suggest that nucleation is a coastal phenomenon, supporting the contention that it is related to direct or biogenic emission of precursor gases from the coastal area during the sea upwelling periods.

 

Effects of source temporal resolution on transport simulations of boreal fire emissions Effects of source temporal resolution on transport simulations of boreal fire emissions

Date added: 08/06/2006
Date modified: 07/27/2009
Filesize: 427.81 kB

Hyer, E. J., E. S. Kasischke, and D. J. Allen (2007), Effects of source temporal resolution on transport simulations of boreal fire emissions, J. Geophys. Res., 112, D01302, doi:10.1029/2006JD007234.


Abstract


The quality of temporal information from daily burned area inputs was evaluated using a transport and chemistry experiment. Carbon monoxide emissions from boreal forest fires were estimated using burned area inputs with daily resolution. Averaging of emissions data to create 30-day aggregate data reduced the variance by 80%, indicating a substantial loss of information. Data from Russia, Canada, and Alaska were tested for periodicity to uncover systematic gaps in daily data. Some evidence of periodicity was found in data from Alaska, where temporal information came from fire mapping by the Alaskan Fire Service. Autocorrelation decayed rapidly and nearly monotonically for Canada and Russia, where temporal information came from Advanced Very High Resolution Radiometer (AVHRR) satellite observations. Daily data as well as 7-day and 30-day aggregates were used as input to the University of Maryland Atmospheric Chemistry and Transport Model, and output was compared with CO observations from the Cooperative Air Sampling Network (CASN); continuous measurements from Mace Head, Ireland; and total column CO retrievals from the Measurement of Pollution in the Troposphere (MOPITT) instrument. CASN flask measurements showed no sensitivity to high-frequency variability in the source, indicating the effectiveness of the filtering protocol at ensuring only well-mixed air masses are sampled in this data set. Differences between daily and 7-day simulations were too small for quantitative comparison in any of the data. For cases where the differences were substantial, simulations using daily and 7-day average sources agreed better with observations than 30-day average sources.

 

Particle counting and numerical models: Effect of instrumental size resolution and particle shapes o Particle counting and numerical models: Effect of instrumental size resolution and particle shapes o

Date added: 08/05/2006
Date modified: 08/05/2009
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Karine Chamaillard, S.G. Jennings, Particle counting and numerical models: Effect of instrumental size resolution and particle shapes on optical cross-sections, Journal of Quantitative Spectroscopy and Radiative Transfer, Volume 100, Issues 1-3, VIII Conference on Electromagnetic and Light Scattering by Nonspherical Particles, July-August 2006, Pages 64-76, ISSN 0022-4073, DOI: 10.1016/j.jqsrt.2005.11.064.

 


Abstract


The effect of instrumental size resolution measurements on numerical calculations of optical cross-sections is investigated. The particle counting instruments considered are a FSSP-300, a large scattering angle probe instrument similar to a ASASP-X, and, an aerodynamical system ELPI instrument. The scattering and hemispheric backscattering cross-sections, Csca and Cbk, are calculated on the basis that the full width of the instrumental size bin should be considered in modeling. An average process is applied on these quantities over the full size bin of the instrument; they are then compared to their usual estimation on the single mean diameter Dp per channel. The effect of particle shape is investigated with ellipsoids and spheres. Results show sensitivity of the optical cross-sections to the shape of the particles as well as position of the mean geometrical diameter Dp of the channels within the interferences modes of the scattering efficiencies. The value of the width of the size bins, d log D, of each channel is crucial in the results. This comparison gives a useful estimation of error important in optical particle counting instruments based on inversion process of optical quantities. In addition, accuracy of size distribution measurements is found not to be representative of accuracy in the calculations of optical cross-sections.

First appearance and rapid growth of anthropogenic HFC-245fa (CHF2CH2CF3) in the atmosphere First appearance and rapid growth of anthropogenic HFC-245fa (CHF2CH2CF3) in the atmosphere

Date added: 08/05/2006
Date modified: 07/01/2009
Filesize: 398.7 kB
Vollmer, M. K., S. Reimann, D. Folini, L. W. Porter, and L. P. Steele (2006), First appearance and rapid growth of anthropogenic HFC-245fa (CHF2CH2CF3) in the atmosphere, Geophys. Res. Lett., 33, L20806, doi:10.1029/2006GL026763.

Abstract


We capture the first atmospheric appearance of HFC-245fa (CHF2CH2CF3), a new foam blowing agent. Our results from the high-altitude observatory at Jungfraujoch, Switzerland, show a rapid growth of this substance in the northern hemispheric troposphere from 0.28 ppt in July 2004 to 0.68 ppt at the end of 2005, which corresponds to an overall increase of >90% per year. By combining our observations with an atmospheric 3-box model we estimate a southern hemispheric trend for this trace gas which we compare to observations at southern hemisphere mid-latitudes. We also estimate a global HFC-245fa emissions increase from 2100–2400 tonnes in 2003 to 5100–5900 tonnes in 2005. Pollution episodes are relatively rare at Jungfraujoch compared to other hydrofluorocarbons thereby confirming the limited use of HFC-245fa in Europe. Back trajectory analysis reveals the largest potential European sources of HFC-245fa in northern Italy and northeastern Spain.

Global trends, seasonal cycles, and European emissions of dichloromethane, trichloroethene, and tetrachloroethene..... Global trends, seasonal cycles, and European emissions of dichloromethane, trichloroethene, and tetrachloroethene.....

Date added: 08/05/2006
Date modified: 07/02/2009
Filesize: 1.92 MB
Simmonds, P. G., et al. (2006), Global trends, seasonal cycles, and European emissions of dichloromethane, trichloroethene, and tetrachloroethene from the AGAGE observations at Mace Head, Ireland, and Cape Grim, Tasmania, J. Geophys. Res., 111, D18304, doi:10.1029/2006JD007082.

Abstract


In situ observations (every 4 hours) of dichloromethane (CH2Cl2) from April 1995 to December 2004 and trichloroethene (C2HCl3) and tetrachloroethene (C2Cl4) from September 2000 to December 2004 are reported for the Advanced Global Atmospheric Gases Experiment (AGAGE) station at Mace Head, Ireland. At a second AGAGE station at Cape Grim, Tasmania, CH2Cl2 and C2Cl4 data collection commenced in 1998 and 2000, respectively. C2HCl3 is below the limit of detection at Cape Grim except during pollution episodes. At Mace Head CH2Cl2 shows a downward trend from 1995 to 2004 of 0.7 ± 0.2 ppt yr−1 (ppt: expressed as dry mole fractions in 1012), although from 1998 to 2004 the decrease has been only 0.3 ± 0.1ppt yr−1. Conversely, there has been a small but significant growth of 0.05 ± 0.01 ppt yr−1 in CH2Cl2 at Cape Grim. The time series for C2HCl3 and C2Cl4 are relatively short for accurate trend analyses; however, we observe a small but significant decline in C2Cl4 (0.18 ± 0.05 ppt yr−1) at Mace Head. European emissions inferred from AGAGE measurements are compared to recent estimates from industry data and show general agreement for C2HCl3. Emissions estimated from observations are lower than industry emission estimates for C2Cl4 and much lower in the case of CH2Cl2. A study of wildfires in Tasmania, uncontaminated by urban emissions, suggests that the biomass burning source of CH2Cl2 may have been previously overestimated. All three solvents have distinct annual cycles, with the phases and amplitudes reflecting their different chemical reactivity with OH as the primary sink.

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

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

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


Abstract


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

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

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

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

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

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

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


Abstract


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

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

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

Abstract


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

Statistical characteristics and predictability of particle formation events at Mace Head Statistical characteristics and predictability of particle formation events at Mace Head

Date added: 08/01/2006
Date modified: 07/23/2009
Filesize: 498.16 kB
Yoon, Y.J., C.D. O’Dowd, S.G. Jennings, S.H. Lee, Statistical characteristics and predictability of particle formation events at Mace Head, J. Geophys. Res.,doi:10.1029/2005JD006284, 2006.

Abstract


The seasonal characteristics of coastal nucleation events at the Mace Head Atmospheric Research Station, resulting from exposure of macroalgae to the atmosphere, were analyzed for a 2-year period from August 2002 to July 2004. Nucleation events occurred on 58% of the days over the period. The seasonal variation of the number of event days and event duration show a clear cycle, with maximum values in spring and autumn and the minimum values in the winter season. The nucleation events typically start ∼75 min prior to the occurrence of the low-tide mark and the event start time is correlated (r = 0.75) to the low-tide height. The intensity of the events, as determined by the peak particle concentrations achieved, is also positively correlated with the amount of tidal areas exposed to ambient air, as determined by the tidal height, and solar radiation. A nucleation potential index (NPI) was developed as a tool to provide a predictive capability for event prediction at Mace Head. The index was derived from normalized tidal height, solar radiation intensity, and wind direction and was compared with the occurrence of nucleation events from the database. The result shows that Mace Head particle formation events can be quite well predicted with a threshold probability of 50%.

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

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

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


Abstract

 

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

European emissions of mercury derived from long-term obsercations at Mace Head, on the western Irish coast European emissions of mercury derived from long-term obsercations at Mace Head, on the western Irish coast

Date added: 08/01/2006
Date modified: 07/24/2009
Filesize: 185.84 kB

Slemr F, R. Ebinghaus, P.G. Simmonds and S.G. Jennings, European emissions of mercury derived from long-term observations at Mace Head, on the western Irish coast, Atmos. Environ., 40, 6966-6974, 2006.


Abstract


Many emission inventories for mercury have been compiled but rarely constrained using observations of ambient air concentrations with a known quality. In this paper, we derive Hg/CO, Hg/halocarbon, and Hg/CH4 emission ratios from pollution episodes observed during the long-term mercury monitoring at the Mace Head Atmospheric Research Station in Ireland. The average Hg/CO emission ratio from 15 pollution episodes with air originating from the European continent observed between 1996 and 2003 was 0.0050±0.0021 ng m-3 ppbv-1, i.e. (5.5±2.3) x 10-7mol/mol, which is almost identical to the ratio reported recently for the continental plumes of eastern Asia. Mercury correlated also with CFCl3 (CFC-11), CF2Cl2 (CFC-12), CH3CCl3, CCl4, CCl2FCF2Cl (CFC-113), CHCl3, N2O, and CH4 during the pollution episodes. The mercury emissions calculated from the emission ratios and the European emissions of the above gases are in reasonable agreement with the estimated anthropogenic total mercury emissions of 250t/yr in 1995. However, the measurements encompass almost exclusively elemental mercury whose anthropogenic emissions are estimated to be only 152 t yr-1. Several hypotheses are proposed to explain this discrepancy, such as natural sources, underestimation of the emissions of elementary mercury, and erroneous speciation of anthropogenic emissions.

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

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

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


Abstract


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

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

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

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


Abstract


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

Aerosol direct radiative effects over the northwest Atlantic, northwest Pacific, and North Indian Oc Aerosol direct radiative effects over the northwest Atlantic, northwest Pacific, and North Indian Oc

Date added: 08/01/2006
Date modified: 07/10/2009
Filesize: 2.78 MB

Bates, T. S. , T. L. Anderson, T. Baynard, T. Bond, O. Boucher, G. Carmichael, A. Clarke, C. Erlick, H. Guo, L. Horowitz, S. Howell, S. Kulkarni, H. Maring, A. McComiskey, A. Middlebrook, K. Noone, C. D. O'Dowd, J. Ogren, J. Penner, P. K. Quinn, A. R. Ravishankara, D. L. Savoie, S. E. Schwartz, Y. Shinozuka, Y. Tang, R. J. Weber and Y. Wu, Aerosol direct radiative effects over the northwest Atlantic, northwest Pacific, and North Indian Oceans: estimates based on in-situ chemical and optical measurements and chemical transport modelling, Atmospheric Chemistry and Physics Discussions, Vol. 6, pp 175-362, 2006.


Abstract


The largest uncertainty in the radiative forcing of climate change over the industrial era is that due to aerosols, a substantial fraction of which is the uncertainty associated with scattering and absorption of shortwave (solar) radiation by anthropogenic aerosols in cloud-free conditions (IPCC, 2001). Quantifying and reducing the uncertainty in aerosol influences on climate is critical to understanding climate change over the industrial period and to improving predictions of future climate change for assumed emission scenarios. Measurements of aerosol properties during major field campaigns in several regions of the globe during the past decade are contributing to an enhanced understanding of atmospheric aerosols and their effects on light scattering and climate. The present study, which focuses on three regions downwind of major urban/population centers (North Indian Ocean (NIO) during INDOEX, the Northwest Pacific Ocean (NWP) during ACE-Asia, and the Northwest Atlantic Ocean (NWA) during ICARTT), incorporates understanding gained from field observations of aerosol distributions and properties into calculations of perturbations in radiative fluxes due to these aerosols. This study evaluates the current state of observations and of two chemical transport models (STEM and MOZART). Measurements of burdens, extinction optical depth (AOD), and direct radiative effect of aerosols (DRE – change in radiative flux due to total aerosols) are used as measurement-model check points to assess uncertainties. In-situ measured and remotely sensed aerosol properties for each region (mixing state, mass scattering efficiency, single scattering albedo, and angular scattering properties and their dependences on relative humidity) are used as input parameters to two radiative transfer models (GFDL and University of Michigan) to constrain estimates of aerosol radiative effects, with uncertainties in each step propagated through the analysis. Constraining the radiative transfer calculations by observational inputs increases the clear-sky, 24-h averaged AOD (34±8%), top of atmosphere (TOA) DRE (32±12%), and TOA direct climate forcing of aerosols (DCF – change in radiative flux due to anthropogenic aerosols) (37±7%) relative to values obtained with "a priori" parameterizations of aerosol loadings and properties (GFDL RTM). The resulting constrained clear-sky TOA DCF is −3.3±0.47, −14±2.6, −6.4±2.1 Wm−2 for the NIO, NWP, and NWA, respectively. With the use of constrained quantities (extensive and intensive parameters) the calculated uncertainty in DCF was 25% less than the "structural uncertainties" used in the IPCC-2001 global estimates of direct aerosol climate forcing. Such comparisons with observations and resultant reductions in uncertainties are essential for improving and developing confidence in climate model calculations incorporating aerosol forcing.

Strong correlation between levels of tropospheric OH and UV-B Strong correlation between levels of tropospheric OH and UV-B

Date added: 04/22/2006
Date modified: 07/27/2009
Filesize: 1.22 MB

Rohrer, F. and H. Berresheim, Strong correlation between levels of tropospheric hydroxyl radicals and solar ultraviolet radiation, Nature, 442, 184-187, 2006.


Abstract


The most important chemical cleaning agent of the atmosphere is the hydroxyl radical, OH. It determines the oxidizing power of the atmosphere, and thereby controls the removal of nearly all gaseous atmospheric pollutants. The atmospheric supply of OH is limited, however, and could be overcome by consumption due to increasing pollution and climate change, with detrimental feedback effects. To date, the high variability of OH concentrations has prevented the use of local observations to monitor possible trends in the concentration of this species. Here we present and analyse long-term measurements of atmospheric OH concentrations, which were taken between 1999 and 2003 at the Meteorological Observatory Hohenpeissenberg in southern Germany. We find that the concentration of OH can be described by a surprisingly linear dependence on solar ultraviolet radiation throughout the measurement period, despite the fact that OH concentrations are influenced by thousands of reactants. A detailed numerical model of atmospheric reactions and measured trace gas concentrations indicates that the observed correlation results from compensations between individual processes affecting OH, but that a full understanding of these interactions may not be possible on the basis of our current knowledge of atmospheric chemistry. As a consequence of the stable relationship between OH concentrations and ultraviolet radiation that we observe, we infer that there is no long-term trend in the level of OH in the Hohenpeissenberg data set.

Low European methyl chloroform emissions inferred from long-term atmospheric measurements Low European methyl chloroform emissions inferred from long-term atmospheric measurements

Date added: 08/26/2005
Date modified: 07/24/2009
Filesize: 186.75 kB

S. Reimann, A.J. Manning, P.G. Simmonds, D.M. Cunnold, R.H.J. Wang, J. Li, A. McCulloch, R.G. Prinn, J. Huang, R.F. Weiss, P.F. Fraser, S. O'Doherty, B.R. Greally, K. Stemmler, M. Hill, and D. Folini, (2005), Low European methyl chloroform emissions inferred from long-term atmospheric measurements, Nature, 433, 506-508.


Abstract


Methyl chloroform (CH3CCl3, 1,1,1,-trichloroethane) was used widely as a solvent before it was recognized to be an ozone-depleting substance and its phase-out was introduced under the Montreal Protocol'. Subsequently, its atmospheric concentration has declined steadily2-4 and recent European methyl chloroform consumption and emissions were estimated to be less than 0.1 gigagrams per year1,5. However, data from a short-term tropospheric measurement campaign (EXPORT) indicated that European methyl chloroform emissions could have been over 20 gigagrams in 2000 (ref. 6), almost doubling previously estimated global emissions1,4. Such enhanced emissions would significantly affect results from the CH3CCl3 method of deriving global abundances of hydroxyl radicals (OH) (refs 7-12) - the dominant reactive atmospheric chemical for removing trace gases related to air pollution, ozone depletion and the greenhouse effect. Here we use long-term, high-frequency data from Mace Head, Ireland and Jungfraujoch, Switzerland, to infer European methyl chloroform emissions. We find that European emission estimates declined from about 60 gigagrams per year in the mid-1990s to 0.3-1.4 and 1.9-3.4 gigagrams per year in 2000-03, based on Mace Head and Jungfraujoch data, respectively. Our European methyl chloroform emission estimates are therefore higher than calculated from consumption data1,5, but are considerably lower than those derived from the EXPORT campaign in 2000

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

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

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


Abstract


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

 

Comparison of long-term trends and seasonal variations of atmospheric mercury concentrations at Comparison of long-term trends and seasonal variations of atmospheric mercury concentrations at

Date added: 08/07/2005
Date modified: 07/27/2009
Filesize: 449.95 kB

Kock, H.H.;  Bieber, E.; Ebinghaus, R.; Spain, T.G.; Thees, B. (2005): Comparison of long-term trends and seasonal variations of atmospheric mercury concentrations at the two European coastal monitoring stations Mace Head, Ireland, and Zingst, Germany. In: Atmospheric Environment . Vol. 39 (2005) 39, 7549 - 7556


Abstract

 

Monitoring of total gaseous mercury (TGM) concentrations has been carried out at Mace Head on the west coast of Ireland and at Zingst on the southern shore-line of the Baltic Sea. We have used the continuous measurements to assess long-term trends and seasonal variations of TGM concentrations over the same time period. Between 1998 and 2004 the annually averaged TGM concentrations measured at Mace Head (1.72 ng m-3) and Zingst (1.66 ng m-3) remained fairly stable. At both stations we measured higher TGM levels during winter months and lower concentrations during summer months. We also observed an unexpected West to East gradient and found that the overall mean Mace Head TGM concentration was 0.06 ng m-3 higher than those of Zingst. For the January to June period, the Mace Head TGM values (6-year mean = 1.75 ng m-3) are significantly elevated compared to the Zingst results (6-year mean-1.64 ng m-3). Since no local anthropogenic mercury sources exist near the Mace Head station, enhanced emission from the sea appears to provide the most probable explanation for the observed differences. Multiple regression analysis with the atmospheric mercury concentrations measured at Zingst were made with selected meteorological and air quality parameters (wind component, dew point, dust and NOx concentrations). The short-term variation in the TGM concentrations at Zingst shows a strong positive correlation with weather conditions and selected air quality parameters, making TGM a usable tracer of air masses originating from different source regions.

 

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

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

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


Abstract

 

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

 

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

Date added: 08/07/2005
Date modified: 06/30/2009
Filesize: 181.92 kB

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


Abstract


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

 

Atmospheric bromoform at Mace Head, Ireland seasonality and evidence for a peatland source Atmospheric bromoform at Mace Head, Ireland seasonality and evidence for a peatland source

Date added: 08/07/2005
Date modified: 07/27/2009
Filesize: 692.16 kB

Carpenter, L. J., Wevill, D. J., O'Doherty, S., Spain, G., and Simmonds, P. G.: Atmospheric bromoform at Mace Head, Ireland: seasonality and evidence for a peatland source, Atmos. Chem. Phys., 5, 2927-2934, 2005.


Abstract


In situ atmospheric observations of bromoform (CHBr3) made over a 2.5 year period at Mace Head, Ireland from May 2001- Dec 2003, including during the NAMBLEX (North Atlantic Marine Boundary Layer Experiment) campaign, show broad maxima from spring until autumn and winter minima, with mixing ratios of 5.3+1.0 pptv (mid March - mid October) and 1.8+0.8 pptv (December-February). This indicates that, unlike CHCl3, which has a summer minimum and winter maximum at Mace Head, local biological sources of CHBr3 have a greater influence on the atmospheric data than photochemical decay during long-range transport. The emission sources are predominantly macroalgal, but we find evidence for a small terrestrial flux from peatland ecosystems, which so far has not been accounted for in the CHBr3 budget. Sharp increases in CHCl3 and CHBr3 concentrations and decreases in O3 concentrations occurred at night when the wind direction switched from an ocean- to a land-based sector (land breeze) and the wind speed dropped to below 5 ms-1. These observations infer a shallow atmospheric boundary layer with increased O3 deposition and concentration of local emissions of both CHCl3 and CHBr3. The ratio of ΔCHCl3/ΔCHBr3 varied strongly according to the prevailing wind direction; from 0.60+0.15 in south-easterly (100-170° and northerly (340-20°) air to 2.5+0.4 in north-easterly (40-70°) air. Of these land-sectors, the south-easterly air masses are likely to be strongly influenced by macroalgal beds along the coast and the emission ratios probably reflect those from seaweeds in addition to land sources. The north-easterly airmasses however had an immediate fetch inland, which locally is comprised of coastal peatland ecosystems (peat bogs and coastal conifer plantations), previously identified as being strong sources of atmospheric CHCl3 under these conditions. Although we cannot entirely rule out other local land or coastal sources, our observations also suggest peatland ecosystem emissions of CHBr3. We use correlations between CHCl3 and CHBr3 during the north-easterly land breeze events in conjunction with previous estimates of local wetland CHCl3 release to tentatively deduce a global wetland CHBr3 source of 20.4(0.4-948) Gg yr-1, which is approximately 7% of the total global source.

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

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

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


Abstract


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

Atmospheric modeling of high- and low-frequency methane observations Importance of interannuall Atmospheric modeling of high- and low-frequency methane observations Importance of interannuall

Date added: 08/06/2005
Date modified: 07/27/2009
Filesize: 1.92 MB

Chen, Y.-H., and R. G. Prinn (2005), Atmospheric modeling of high- and low-frequency methane observations: Importance of interannually varying transport, J. Geophys. Res., 110, D10303, doi:10.1029/2004JD005542.


Abstract


We compare modeled and observed atmospheric methane (CH4) between 1996 and 2001, focusing on the role of interannually varying (IAV) transport. The comparison uses observations taken at 13 high-frequency (∼hourly) in situ and 6 low-frequency (∼weekly) flask measurement sites. To simulate atmospheric methane, we use the global 3-D chemical transport model (MATCH) driven by NCEP reanalyzed winds at T62 resolution (∼1.8° × 1.8°). For the simulation, both methane surface emissions and atmospheric sink (OH destruction) are prescribed as annually repeating fields; thus, atmospheric transport is the only IAV component in the simulation. MATCH generally reproduces the amplitude and phase of the observed methane seasonal cycles. At the high-frequency sites, the model also captures much of the observed CH4 variability due to transient synoptic events, which are sometimes related to global transport events. For example, the North Atlantic Oscillation (NAO) and El Niño are shown to influence year-to-year methane observations at Mace Head (Ireland) and Cape Matatula (Samoa), respectively. Simulations of individual flask measurements are generally more difficult to interpret at certain sites, partially due to observational undersampling in areas of high methane variability. A model-observational comparison of methane monthly means at seven coincident in situ and flask locations shows a better comparison at the in situ sites. Additional simulations conducted at coarser MATCH resolution (T42, ∼2.8° × 2.8°) showed differences from the T62 simulation at sites near strong emissions. This study highlights the importance of using consistent observed meteorology to simulate atmospheric methane, especially when comparing to high-frequency observations.

 

Direct Measurements of New-Particle Fluxes in the Coastal Environment Direct Measurements of New-Particle Fluxes in the Coastal Environment

Date added: 08/06/2005
Date modified: 07/27/2009
Filesize: 228.88 kB

Flanagan, Robert J., Michael Geever, and Colin D. O'Dowd (2005), Direct Measurements of New-Particle Fluxes in the Coastal Environment, Enviro Chem, 2(4), 256, doi:10.1071/EN05069.


Abstract


Measurements of the flux of new secondary aerosol particles during nucleation events in the coastal environment using an eddy-correlation technique are reported for the first time. Events are divided into two types based on the prevailing wind direction. During tidal-related nucleation events, new-particle upward fluxes are typically of the order of 109–1010 particles m-2 s-1. A close correlation (r2 = 0.86) was found between total particle concentration and total (positive) flux when air masses were not affected by multiple sources. This would suggest that continuous measurements of particle number concentration at Mace Head can be translated into a flux using the resulting parameterization. It is expected that parameterizations obtained from similar data and analysis would be equally feasible at other coastal locations.

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