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Journal Publications

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

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Documents

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Nature-times Weather Understanding rainfall Nature-times Weather Understanding rainfall

Date added: 08/01/1971
Date modified: 08/01/2008
Filesize: 336.23 kB

An assessment of the surface ozone trend in Ireland relevant to air pollution and environmental protection An assessment of the surface ozone trend in Ireland relevant to air pollution and environmental protection

Date added: 03/12/2013
Date modified: 03/12/2013
Filesize: 442.05 kB

Tripathi, Om, P., Stephen G. Jennings, Colin O’Dowd, Barbara O’Leary, Keith Lambkin, Eoin Moran, Simon J. O’Doherty and T. Gerard Spain, An assessment of the surface ozone trend in Ireland relevant to air pollution and environmental protection, Atmos. Pollution Res., 3, 341-351, 2012.


Abstract. Hourly data (1994–2009) of surface ozone concentrations at eight monitoring sites have been investigated to assess target level and long–term objective exceedances and their trends. The European Union (EU) ozone target value for human health (60 ppb–maximum daily 8–hour running mean) has been exceeded for a number of years for almost all sites but never exceeded the set limit of 25 exceedances in one year. Second highest annual hourly and 4th highest annual 8–hourly mean ozone concentrations have shown a statistically significant negative trend for in–land sites of Cork–Glashaboy, Monaghan and Lough Navar and no significant trend for the Mace Head site. Peak afternoon ozone concentrations averaged over a three year period from 2007 to 2009 have been found to be lower than corresponding values over a three–year period from 1996 to 1998 for two sites: Cork–Glashaboy and Lough Navar sites. The EU long–term objective value of AOT40 (Accumulated Ozone Exposure over a threshold of 40 ppb) for protection of vegetation (3 ppm–hour, calculated from May to July) has been exceeded, on an individual year basis, for two sites: Mace Head and Valentia. The critical level for the protection of forest (10 ppm–hour from April to September) has not been exceeded for any site except at Valentia in the year 2003. AOT40–Vegetation shows a significant negative trend for a 3–year running average at Cork–Glashaboy (–0.13±0.02 ppm–hour per year), at Lough Navar (–0.05±0.02 ppm–hour per year) and at Monaghan (–0.03±0.03 ppm–hour per year–not statistically significant) sites. No statistically significant trend was observed for the coastal site of Mace head. Overall, with the exception of the Mace Head and Monaghan sites, ozone measurementrecords at Irish sites show a downward negative trend in peak values that affect human health and vegetation.

 

Optical properties of the atmospheric aerosol at mace head Optical properties of the atmospheric aerosol at mace head

Date added: 08/07/1999
Date modified: 09/11/2009
Filesize: 118.21 kB

O'Reilly S.; Kleefeld C.; Jennings S.G.,Optical properties of the atmospheric aerosol at mace head  ,Journal of Aerosol Science, Volume 30, Supplement 1, September 1999 , pp. 631-632(2)


Abstract

 

The atmospheric aerosol is known to cause cooling of the earth's climate through radiative forcing. This forcing is comparable but of opposite sign to the radiative forcing due to greenhouse gases [1PCC, 1995]. However, unlike greenhouse gases, the atmospheric aerosol is not uniformly distributed about the globe. It is found to vary significantly both spatially and temporally. Therefore, an analysis of global radiative forcing due to the atmospheric aerosol requires an estimation of forcing on a regional scale. Characterisation of the optical properties of the local atmospheric aerosol forms an integral part of such an estimation. The scattering coefficient, Osp, and absorption coefficient, (Yap, of the atmospheric aerosol are basic input parameters to radiative forcing models. These parameters have been measured since 1996 and 1989, respectively, at the Global Atmospheric Watch (GAW/WMO) atmospheric research station at Mace Head (53°19'N, 9°54'W), located on the west coast of Ireland. The results of measurements from 7 th January 1997 to 12 th June ! 997 are presented. The scattering measurements were conducted with a TSI Model 3563 Integrating Nephelometer, operating at three wavelengths (450nm, 550nm and 700nm). It also had the
capability of measuring aerosol hemispheric backscatter coefficient from 90 ° to 180 °. Black carbon mass concentrations were measured using a Magee Scientific Model AE9 Aethalometer. The absorption coefficient for each wavelength was obtained by dividing black carbon mass concentrations by a constant, C; C(~=450nm)=1.5, C()~=550nm)=1.9 and C(L=700nm)=2.4 [Bodhaine, 1995], in order to compare with the aerosol scattering coefficients at these wavelengths. The scattering coefficient, Osp, for ~.=550nm ranged from 7 to 280 Mm -1 with an average and standard deviation of 76 + 49 Mm "l (geometric mean of 60 + 2 Mmt). The corresponding hemispheric backscattering coefficient, Cbsp, measurements were about an order of magnitude lower than (ysp ranging from 0.9 to 35 Mm "1 (geometric mean of 7 + 2 Mm-I). This results in a
hemispheric backscattered fraction, b, of 0.12 + 0.01 (geometric mean of 0.12). The AngstrOm exponent, describes the dependence of the aerosol scattering coefficient on wavelength, )~. The red-blue Angstr6m exponent (Ll=700nm, ~2=450nm) was found to range from -1.9 to 0.15 with an average of-0.66 + 0.7 (geometric mean of-0.69). The absorption coefficient, aap, for ~.=550nm ranged from 0.12 to 22 Mm "l and averaged 1.7 Mm "1 (geometric mean of 0.9 Mm'l). This results in an extinction coefficient, (yext, averaging
77.7Mm "1 (geometric mean of 53+2Mm'l). The scattering and absorption coefficients areused to calculate the single-scattering albedo, which describes the relative contributions of scattering and absorption to the total light extinction. The calculated albedo values ranged from 0.9 to 0.998 and averaged 0.97 + 0.02 (geometric mean of 0.97), indicating a highly scattering aerosol. The single scattering albedo exhibits a logarithmic correlation (R2=0.55, significant at a 99% confidence level) with black carbon concentrations. As black carbon levels increase, the albedo values can be seen to decrease  The scattering time series obtained were found to change with impact of different types of air mass (continental, marine and polar). The influence of synoptic meteorology on the scattering coefficient at Mace Head will be quantified by combining the pattern recognition capabilities of cluster analysis with air mass back-trajectory data.

Coastal Iodine Emissions: Part 2. Particle Nucleation Processes Coastal Iodine Emissions: Part 2. Particle Nucleation Processes

Date added: 03/21/2013
Date modified: 03/21/2013
Filesize: 2.57 MB

Monahan, C.; Ashu-Ayem, E. R.; Nitschke, U.; Darby, S. B.; Smith, P. D.; Stengel, D. B.; Venables, D. S.; O’Dowd, C. D. Coastal Iodine Emissions: Part 2. Particle Nucleation Processes, dx.doi.org/10.1021/es3011805 | Environ. Sci. Technol. 2012, 46, 10422−10428.


Abstract. Laboratory studies into particle formation from Laminaria digitata macroalgae were undertaken to elucidate aerosol formation for a range of I2 (0.376 ppbv) and O3 (<396 ppbv) mixing ratios and light levels (EPAR = 15, 100, and 235 μmol photons m2 s1). No clear pattern was observed for I2 or aerosol parameters as a function of light levels. Aerosol mass fluxes and particle number concentrations, were, however, correlated with I2 mixing ratios for low O3 mixing ratios of <3 ppbv (R2 = 0.7 and 0.83, respectively for low light levels, and R2 = 0.95 and 0.98, respectively for medium light levels). Additional experiments into particle production as a function of laboratory-generated I2, over a mixing ratio range of 18 ppbv, were conducted under moderate O3 mixing ratios (≈24 ppbv) where a clear, 100-fold or greater, increase in the aerosol number concentrations and mass fluxes was observed compared to the low O3 experiments. A linear relationship between particle concentration and I2 was found, in reasonable agreement with previous studies. Scaling the laboratory relationship to aerosol concentrations typical of the coastal boundary layer suggests a I2 mixing ratio range of 693 pptv can account for the observed particle production events. Aerosol number concentration produced from I2 is more than a factor of 10 higher than that produced from CH2I2 for the same mixing ratios.

 

Photochemical impact on ozone fluxes in Coastal Waters Photochemical impact on ozone fluxes in Coastal Waters

Date added: 03/19/2013
Date modified: 03/19/2013
Filesize: 496.45 kB

Coleman, L., P. McVeigh, H. Berresheim, M. Martino, C.D. O’Dowd, Photochemical impact on ozone fluxes in Coastal Waters, Advances in Meteorology, Volume 2012, Article ID 943785, doi:10.1155/2012/943785, 2012


Abstract. Ozone fluxes, derived from gradient measurements in Northeast Atlantic coastal waters, were observed to depend on both tide height and solar radiation. Peak ozone fluxes of 0.26 ±0.04 μg m2 s1 occurred during low-tide conditions when exposed microalgae fields contributed to the flux footprint. Additionally, at mid-to-high tide, when water surfaces contribute predominantly to the flux footprint, fluxes of the order of 0.12 ±0.03 μg m2 s1 were observed. Considering only fluxes over water covered surfaces, and using an advanced ozone deposition model that accounts for surface-water chemistry enhancing the deposition sink, it is demonstrated that a photochemical enhancement reaction with dissolved organic carbon (DOC) is required to explain the enhanced ozone deposition during daylight hours. This sink amounts to an ozone loss rate of up to 0.6 ppb per hour under peak solar irradiance and points to a missing sink in the marine boundary layer ozone budget.

 

Igac August 2001 Igac August 2001

Date added: 08/06/2001
Date modified: 08/06/2008
Filesize: 1.91 MB

Evaluation of a three-dimensional chemical transport model (PMCAMx) in the European domain during the EUCAARI May 2008 campaign Evaluation of a three-dimensional chemical transport model (PMCAMx) in the European domain during the EUCAARI May 2008 campaign

Date added: 03/19/2013
Date modified: 03/19/2013
Filesize: 1.84 MB

Fountoukis, C., P. N. Racherla, H. A. C. Denier van der Gon, P. Polymeneas, P. E. Haralabidis, C. Pilinis, A. Wiedensohler, M. Dall’Osto, C. O'Dowd, and S. N. Pandis, Evaluation of a three-dimensional chemical transport model (PMCAMx) in the European domain during the EUCAARI May 2008 campaign, Atmos. Chem. Phys., 11, 10331–10347, 2011, doi:10.5194/acp-11-10331-2011, 2011.


Abstract. PMCAMx-2008, a detailed three-dimensional chemical transport model (CTM), was applied to Europe to simulate the mass concentration and chemical composition of particulate matter (PM) during May 2008. The model includes a state-of-the-art organic aerosol module which is based on the volatility basis set framework treating both primary and secondary organic components as semivolatile and photochemically reactive. The model performance is evaluated against high time resolution aerosol mass spectrometer (AMS) ground and airborne measurements. Overall, organic aerosol is predicted to account for 32% of total PM1 at ground level during May 2008, followed by sulfate (30 %), crustal material and sea-salt (14 %), ammonium (13 %), nitrate (7 %), and elemental carbon (4 %). The model predicts that fresh primary OA (POA) is a small contributor to organic PM concentrations in Europe during late spring, and that oxygenated species (oxidized primary and biogenic secondary) dominate the ambient OA. The Mediterranean region is the only area in Europe where sulfate concentrations are predicted to be much higher than the OA, while organic matter is predicted to be the dominant PM1 species in central and northern Europe. The comparison of the model predictions with the ground measurements in four measurement stations is encouraging. The model reproduces more than 94% of the daily averaged data and more than 87% of the hourly data within a factor of 2 for PM1 OA. The model tends to predict relatively flat diurnal profiles for PM1 OA in many areas, both rural and urban in agreement with the available measurements. The model performance against the high time resolution airborne measurements at multiple altitudes and locations is as good as its performance against the ground level hourly measurements. There is no evidence of missing sources of OA aloft over Europe during this period.

 

Particle mobility size spectrometers: harmonization of technical standards and data structure to facilitate high quality long-term observations of atmospheric particle number size distributions Particle mobility size spectrometers: harmonization of technical standards and data structure to facilitate high quality long-term observations of atmospheric particle number size distributions

Date added: 03/19/2013
Date modified: 03/19/2013
Filesize: 1021.65 kB

Wiedensohler, A., Birmili, W., Nowak, A., Sonntag, A., Weinhold, K., Merkel, M., Wehner, B., Tuch, T., Pfeifer, S., Fiebig, M., Fjäraa, A. M., Asmi, E., Sellegri, K., Depuy, R., Venzac, H., Villani, P., Laj, P., Aalto, P., Ogren, J. A., Swietlicki, E., Roldin, P., Williams, P., Quincey, P., Hüglin, C., Fierz-Schmidhauser, R., Gysel, M., Weingartner, E., Riccobono, F., Santos, S., Grüning, C., Faloon, K., Beddows, D., Harrison, R. M., Monahan, C., Jennings, S. G., O'Dowd, C. D., Marinoni, A., Horn, H.-G., Keck, L., Jiang, J., Scheckman, J., McMurry, P. H., Deng, Z., Zhao, C. S., Moerman, M., Henzing, B., and de Leeuw, G.: Particle mobility size spectrometers: harmonization of technical standards and data structure to facilitate high quality long-term observations of atmospheric particle number size distributions, Atmos. Meas. Techs., Vol 5 Issue 3 Pages 657-685 DOI: 10.5194/amt-5-657-2012,2012.


Abstract. Mobility particle size spectrometers often referred to as DMPS (Differential Mobility Particle Sizers) or SMPS (Scanning Mobility Particle Sizers) have found a wide range of applications in atmospheric aerosol research. However, comparability of measurements conducted world-wide is hampered by lack of generally accepted technical standards and guidelines with respect to the instrumental setup, measurement mode, data evaluation as well as quality control. Technical standards were developed for a minimum requirement of mobility size spectrometry to perform long-term atmospheric aerosol measurements. Technical recommendations include continuous monitoring of flow rates, temperature, pressure, and relative humidity for the sheath and sample air in the differential mobility analyzer. We compared commercial and custom-made inversion routines to calculate the particle number size distributions from the measured electrical mobility distribution. All inversion routines are comparable within few per cent uncertainty for a given set of raw data. Furthermore, this work summarizes the results from several instrument intercomparison workshops conducted within the European infrastructure project EUSAAR (European Supersites for Atmospheric Aerosol Research) and ACTRIS (Aerosols, Clouds, and Trace gases Research InfraStructure Network) to determine present uncertainties especially of custom-built mobility particle size spectrometers. Under controlled laboratory conditions, the particle number size distributions from 20 to 200 nm determined by mobility particle size spectrometers of different design are within an uncertainty range of around ±10% after correcting internal particle losses, while below and above this size range the discrepancies increased. For particles larger than 200 nm, the uncertainty range increased to 30 %, which could not be explained. The network reference mobility spectrometers with identical design agreed within ±4% in the peak particle number concentration when all settings were done carefully. The consistency of these reference instruments to the total particle number concentration was demonstrated to be less than 5 %. Additionally, a new data structure for particle number size distributions was introduced to store and disseminate the data at EMEP (European Monitoring and Evaluation Program). This structure contains three levels: raw data, processed data, and final particle size distributions. Importantly, we recommend reporting raw measurements including all relevant instrument parameters as well as a complete documentation on all data transformation and correction steps. These technical and data structure standards aim to enhance the quality of long-term size distribution measurements, their comparability between different networks and sites, and their transparency and traceability back to raw data.

 

Nitrogenated and aliphatic organic vapors as possible drivers for marine secondary organic aerosol growth Nitrogenated and aliphatic organic vapors as possible drivers for marine secondary organic aerosol growth

Date added: 03/13/2013
Date modified: 03/13/2013
Filesize: 1.02 MB

DallOsto, Manuel,Darius Ceburnis, Ciaran Monahan, Douglas R. Worsnop,

Jakub Bialek, Markku Kulmala, Theo Kurtén, Mikael Ehn, John Wenger,

John Sodeau, Robert Healy, and Colin ODowd. (2012), Nitrogenated and aliphatic organic vapors as possible drivers for marine secondary organic aerosol growth, J. Geophys. Res., 117, D12311, doi:10.1029/2012JD017522.


Abstract. Measurements of marine aerosol chemistry, using state-of-the-art mass spectrometry, as well as aerosol microphysics, hygroscopicity and cloud condensation nuclei (CCN) activity were undertaken during new particle growth events. The events were detected in air advecting over North East (NE) Atlantic waters during the EUCAARI Intensive Observation Period in June 2008 at Mace Head, Ireland. During these growth events, the aerosol mass spectrometers illustrated increases in accumulation mode aerosol phase nitrogenated and aliphatic compounds thought to condense from the gas phase. Since the composition changes observed in the accumulation mode occurred simultaneously to the growth of the accumulation, Aitken and nucleation modes, the growth of both the nucleation mode and the Aitken mode is attributed to the condensation of these species. Nitrogenated compounds like amines are also plausible candidates in the nucleation process, as suggested by quantum mechanic calculations. It is also plausible that amides and organic nitrites, also identified by the mass spectrometers, are possible candidate chemical compounds, suggesting that multiple types of chemical species may be contributing. Given that these open ocean aerosol formation and growth events occur in very clean polar marine air masses, we suggest that the organic compounds responsible for particle formation and growth are mainly of biogenic origin. Despite increasing the particle number concentration, the initial effect is to suppress hygroscopicity and CCN activity.

Aerosol analysis and forecast in the ECMWF Integrated Forecast System: 3. Evaluation by means of case studies Aerosol analysis and forecast in the ECMWF Integrated Forecast System: 3. Evaluation by means of case studies

Date added: 03/14/2013
Date modified: 03/14/2013
Filesize: 4.4 MB

Mangold, A., H. De Backer, B. De Paepe, S. Dewitte, I. Chiapello, Y. Derimian, M. Kacenelenbogen, J.‐F. Léon, N. Huneeus, M. Schulz, D. Ceburnis, C. O’Dowd, H. Flentje, S. Kinne, A. Benedetti, J.‐J. Morcrette and O. Boucher, Aerosol analysis and forecast in the ECMWF Integrated Forecast System: 3. Evaluation by means of case studies, J. Geophys. Res., 116, D03302, doi:10.1029/2010JD014864., 2011.


Abstract. A near real‐time system for assimilation and forecasts of aerosols, greenhouse and trace gases, extending the ECMWF Integrated Forecasting System (IFS), has been developed in the framework of the Global and regional Earth‐system Monitoring using Satellite and in‐situ data (GEMS) project. The GEMS aerosol modeling system is novel as it is the first aerosol model fully coupled to a numerical weather prediction model with data assimilation. A reanalysis of the period 2003–2009 has been carried out with the same system. During its development phase, the aerosol system was first run for the time period January 2003 to December 2004 and included sea salt, desert dust, organic matter, black carbon, and sulfate aerosols. In the analysis, Moderate Resolution Imaging Spectroradiometer (MODIS) total aerosol optical depth (AOD) at 550 nm over ocean and land (except over bright surfaces) was assimilated. This work evaluates the performance of the aerosol system by means of case studies. The case studies include (1) the summer heat wave in Europe in August 2003, characterized by forest fire aerosol and conditions of high temperatures and stagnation, favoring photochemistry and secondary aerosol formation, (2) a large Saharan dust event in March 2004, and (3) periods of high and low sea salt aerosol production. During the heat wave period in 2003, the linear correlation coefficients between modeled and observed AOD (550 nm) and between modeled and observed PM2.5 mass concentrations are 0.82 and 0.71, respectively, for all investigated sites together. The AOD is slightly and the PM2.5 mass concentration is clearly overestimated by the aerosol model during this period. The simulated sulfate mass concentration is significantly correlated with observations but is distinctly overestimated. The horizontal and vertical locations of the main features of the aerosol distribution during the Saharan dust outbreak are generally well captured, as well as the timing of the AOD peaks. The aerosol model simulates winter sea salt AOD reasonably well, however, showing a general overestimation. Summer sea salt events show a better agreement. Overall, the assimilation of MODIS AOD data improves the subsequent aerosol predictions when compared with observations, in particular concerning the correlation and AOD peak values. The assimilation is less effective in correcting a positive (PM2.5, sulfate mass concentration, Angström exponent) or negative (desert dust plume AOD) model bias.

 

 

 

 

 

 

Nature-times Weather Understanding rainfall Nature-times Weather Understanding rainfall

Date added: 08/01/1971
Date modified: 09/11/2009
Filesize: 336.23 kB

Coastal iodine emissions: Part 1. Release of I2 by Laminaria digitata in chamber experiments Coastal iodine emissions: Part 1. Release of I2 by Laminaria digitata in chamber experiments

Date added: 03/19/2013
Date modified: 03/19/2013
Filesize: 3.16 MB

Ashu-Ayem, E.R., U, Nitschke, C. Monahan, J. Chen, S.B. Darby, P.D. Smith, C.D. O’Dowd, D. B. Stengel, D.S. Venables. Coastal iodine emissions: Part 1. Release of I2 by Laminaria digitata in chamber experiments, dx.doi.org/10.1021/es204534v | Environ. Sci. Technol. 2012, 46, 10413−10421.


Abstract. Tidally exposed macroalgae emit large amounts of I2 and iodocarbons that produce hotspots of iodine chemistry and intense particle nucleation events in the coastal marine boundary layer. Current emission rates are poorly characterized, however, with reported emission rates varying by 3 orders of magnitude. In this study, I2 emissions from 25 Laminaria digitata samples were investigated in a simulation chamber using incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS). The chamber design allowed gradual extraction of seawater to simulate tidal emersion of algae. Samples were exposed to air with or without O3 and to varying irradiances. Emission of I2 occurred in four distinct stages: (1) moderate emissions from partially submerged samples; (2) a strong release by fully emerged samples; (3) slowing or stopping of I2 release; and (4) later pulses of I2 evident in some samples. Emission rates were highly variable and ranged from 7 to 616 pmol min1 gFW1 in ozone-free air, with a median value of 55 pmol min1 gFW1 for 20 samples.

 

Primary and secondary marine organic aerosols over the North Atlantic Ocean during the MAP experiment Primary and secondary marine organic aerosols over the North Atlantic Ocean during the MAP experiment

Date added: 03/19/2013
Date modified: 03/19/2013
Filesize: 1.9 MB

Decesari, S., E. Finessi, M. Rinaldi, M. Paglione, S. Fuzzi, E. G. Stephanou, T. Tziaras, A.Spyros, D. Ceburnis, C. O'Dowd, M. Dall’Osto, R. Harrison, J. Allan, H. Coe, M. C. Facchini, Primary and secondary marine organic aerosols over the North Atlantic Ocean during the MAP experiment, J. Geophys. Res., 116, D22210, doi:10.1029/2011JD016204, 2011


Abstract.

The organic chemical composition of atmospheric submicron particles in the marine boundary layer was characterized over the northeast Atlantic Ocean in summer 2006, during the season of phytoplankton blooms, in the frame of the Marine Aerosol Production (MAP) experiment. First measurements of water insoluble organic carbon (WIOC) in marine aerosol particles by nuclear magnetic resonance (NMR) spectroscopy showed that it is structurally similar to lipids, resembling the organic fraction of sea spray formed during bubble bursting experiments. The composition of the watersoluble organic carbon (WSOC) fraction was investigated by liquid chromatography mass spectrometry and by 1D and 2DNMR spectroscopy, and showed a less hydrophilic fraction containing traces of fatty acids and rich of alkanoic acids formed by lipid degradation, and a more hydrophilic fraction, containing more functionalized species encompassing short chain aliphatic acids and sulfate esters of hydroxyl carboxylic acids. The more oxidized fraction of WSOC accounts for the oxidized organic aerosol components, which can form by either gastoparticle conversion or extensive chemical aging of lipidcontaining primary particles, as also suggested by the parallel measurements using online mass spectrometric techniques (presented in a companion paper), showing oxidized organic substances internally mixed with sea salt particles. These measurements are also compared with online measurements using an Aerosol TimeOfFlight Mass Spectrometer (ATOFMS) and Aerodyne Aerosol Mass Spectrometer (AMS). Given the large variability in the chemical composition of marine organic aerosol particles, a multitechnique approach is recommended to reduce method dependent categorizations and oversimplifications and to improve the comparability with the results obtained in different oceanic areas.

 

Functionalization and fragmentation during ambient organic aerosol aging: application of the 2-D volatility basis set to field studies Functionalization and fragmentation during ambient organic aerosol aging: application of the 2-D volatility basis set to field studies

Date added: 03/21/2013
Date modified: 03/21/2013
Filesize: 1.84 MB

Murphy, B. N., N. M. Donahue, C. Fountoukis, M. Dall’Osto, C. O’Dowd, A. Kiendler-Scharr, and S. N. Pandis, Functionalization and fragmentation during ambient organic aerosol aging: application of the 2-D volatility basis set to field studies, Atmos. Chem. Phys., 12, 10797–10816, 2012, doi:10.5194/acp-12-10797-2012.


Abstract. Multigenerational oxidation chemistry of atmospheric organic compounds and its effects on aerosol loadings and chemical composition is investigated by implementing the Two-Dimensional Volatility Basis Set (2-D-VBS) in a Lagrangian host chemical transport model. Three model formulations were chosen to explore the complex interactions between functionalization and fragmentation processes during gas-phase oxidation of organic compounds by the hydroxyl radical. The base case model employs a conservative transformation by assuming a reduction of one order of magnitude in effective saturation concentration and an increase of oxygen content by one or two oxygen atoms per oxidation generation. A second scheme simulates functionalization in more detail using group contribution theory to estimate the effects of oxygen addition to the carbon backbone on the compound volatility. Finally, a fragmentation scheme is added to the detailed functionalization scheme to create a functionalization-fragmentation parameterization. Two condensed-phase chemistry pathways are also implemented as additional sensitivity tests to simulate (1) heterogeneous oxidation via OH uptake to the particle-phase and (2) aqueous-phase chemistry of glyoxal and methylglyoxal. The model is applied to summer and winter periods at three sites where observations of organic aerosol (OA) mass and O:C were obtained during the European Integrated Project on Aerosol Cloud Climate and Air Quality Interactions (EUCAARI) campaigns. The base case model reproduces observed mass concentrations and O:C well, with fractional errors (FE) lower than 55% and 25 %, respectively. The detailed functionalization scheme tends to overpredict OA concentrations, especially in the summertime, and also underpredicts O:C by approximately a factor of 2. The detailed functionalization model with fragmentation agrees well with the observations for OA concentration, but still underpredicts O:C. Both heterogeneous oxidation and aqueous-phase processing have small effects on OA levels but heterogeneous oxidation, as implemented here, does enhance O:C by about 0.1. The different schemes result in very different fractional attribution for OA between anthropogenic and biogenic sources.

 

Aerosol decadal trends – Part 2: In-situ aerosol particle number concentrations at GAW and ACTRIS stations Aerosol decadal trends – Part 2: In-situ aerosol particle number concentrations at GAW and ACTRIS stations

Date added: 03/12/2013
Date modified: 03/12/2013
Filesize: 6.1 MB

Asmi, A., M. Collaud Coen, J.A. Ogren, E. Andrews, P. Sheridan, A. Jefferson, E. Weingartner, U. Baltensperger, N. Bukowiecki, H. Lihavainen, N. Kivekäs, E. Asmi, P. P. Aalto, M. Kulmala, A. Wiedensohler, W. Birmili, A. Hamed, C. O'Dowd, S. G Jennings, R. Weller, H. Flentje, A. M. Fjaeraa, M. Fiebig, C. L. Myhre, A. G. Hallar, E. Swietlicki, A. Kristensson, and P. Laj,Aerosol decadal trends – Part 2: In-situ aerosol particle number concentrations at GAW and ACTRIS stations, Atmos. Chem. Phys., 13, 895-916, 2013, www.atmos-chem-phys.net/13/895/2013/ doi:10.5194/acp-13-895-2013


Abstract. We have analysed the trends of total aerosol particle number concentrations (N) measured at long-term measurement stations involved either in the Global Atmosphere Watch (GAW) and/or EU infrastructure project ACTRIS. The sites are located in Europe, North America, Antarctica, and on Pacific Ocean islands. The majority of the sites showed clear decreasing trends both in the full-length time series, and in the intra-site comparison period of 2001–2010, especially during the winter months. Several potential driving processes for the observed trends were studied, and even though there are some similarities between N trends and air temperature changes, the most likely cause of many northern hemisphere trends was found to be decreases in the anthropogenic emissions of primary particles, SO2 or some co-emitted species. We could not find a consistent agreement between the trends of N and particle optical properties in the few stations with long time series of all of these properties. The trends of N and the proxies for cloud condensation nuclei (CCN) were generally consistent in the few European stations where the measurements were available. This work provides a useful comparison analysis for modelling studies of trends in aerosol number concentrations.

 

Connecting marine productivity to sea-spray via nanoscale biological processes: Phytoplankton Dance or Death Disco? Connecting marine productivity to sea-spray via nanoscale biological processes: Phytoplankton Dance or Death Disco?

Date added: 02/02/2016
Date modified: 02/03/2016
Filesize: 1.03 MB

Connecting marine productivity to sea-spray via nanoscale biological processes: Phytoplankton Dance or Death Disco? O'Dowd, C,Ceburnis, D,Ovadnevaite, J,Bialek, J,Stengel, DB,Zacharias, M,Nitschke, U,Connan, S,Rinaldi, M,Fuzzi, S,Decesari, S,Facchini, MC,Marullo, S,Santoleri, R,Dell'Anno, A,Corinaldesi, C,Tangherlini, M,Danovaro, R., Scientific Reports 5, Article number: 14883, doi:10.1038/srep14883 (2015)


Bursting bubbles at the ocean-surface produce airborne salt-water spray-droplets, in turn, forming climate-cooling marine haze and cloud layers. The reflectance and ultimate cooling effect of these layers is determined by the spray’s water-uptake properties that are modified through entrainment of ocean-surface organic matter (OM) into the airborne droplets. We present new results illustrating a clear dependence of OM mass-fraction enrichment in sea spray (OMss) on both phytoplankton-biomass, determined from Chlorophyll-a (Chl-a) and Net Primary Productivity (NPP). The correlation coefficient for OMss as a function of Chl-a increased form 0.67 on a daily timescale to 0.85 on a monthly timescale. An even stronger correlation was found as a function of NPP, increasing to 0.93 on a monthly timescale. We suggest the observed dependence is through the demise of the bloom, driven by nanoscale biological processes (such as viral infections), releasing large quantities of transferable OM comprising cell debris, exudates and other colloidal materials. This OM, through aggregation processes, leads to enrichment in sea-spray, thus demonstrating an important coupling between biologically-driven plankton bloom termination, marine productivity and sea-spray modification with potentially significant climate impacts.



 

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