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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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 Nanoparticles in boreal forest and coastal environment: a comparison of observations and implicatio Nanoparticles in boreal forest and coastal environment: a comparison of observations and implicatio

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 1.15 MB

Lehtipalo, K., Kulmala, M., Sipilä, M., Petäjä, T., Vana, M., Ceburnis, D., Dupuy, R., and O'Dowd, C


Abstract.

 1

 

The detailed mechanism of secondary new particle formation in the atmosphere is still under debate. It is proposed that particle formation happens v a activation of 1–2 nm atmospheric neutral molecular clusters and/or large molecules. Since traditional instrumentation does not reach these sizes, the hypothesis has not yet been verified. By directly measuring particle size distributions down to mobility  diameters of about 1.3 nm with a pulse-height CPC, we  provide evidence of the nucleation mechanism in a coastal environment (Mace Head, Ireland) and in a boreal forest  (Hyyti¨al¨a, Finland). In both places neutral sub-3 nm condensation nuclei (nano-CN) were continuously present, even  when no new particle formation was detected. In Mace Head,  however, the concentration of the nano-CN was far too low to account for the particle formation rates during particle bursts. Thus the results imply that at coastal sites new particle formation initiates, as previously proposed, via homogenous nucleation  from biogenic iodine vapors. In contrast, activation  of pre-existing nano-CN remains a possible explanation in the boreal forest, but the observed concentrations are not the limiting factor for the particle formation events.

 

 

 On the effect of wind speed on submicron sea salt mass concentrations and source fluxes On the effect of wind speed on submicron sea salt mass concentrations and source fluxes

Date added: 03/21/2013
Date modified: 03/21/2013
Filesize: 2.25 MB

Ovadnevaite, J., D. Ceburnis, M. Canagaratna, H. Berresheim, J. Bialek, G. Martucci, D. R. Worsnop, and C. O’Dowd, On the effect of wind speed on submicron sea salt mass concentrations and source fluxes, J. Geophys. Res., 117, D16201, doi:10.1029/2011JD017379, 2012.


Abstract. A High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS) was evaluated for its ability to quantify submicron sea salt mass concentrations. The evaluation included both laboratory and field studies. Quantification of the sea salt signal in the HR-ToF-AMS was achieved by taking the 23Na35Cl+ ion as a surrogate for sea salt and then identifying a calibration scaling factor through a comparison with mono-disperse laboratory generated sea salt aerosol. Ambient sea salt concentrations calculated using this method agreed well with those obtained by ion chromatography of filter samples, following a 1:1 regression slope and a correlation coefficient R = 0.93. A key advantage of this AMS-based method is that it allows for high time resolution measurements of sea salt (5 min) along with the speciation of other chemical compounds, including primary organics contributing to sea spray. The high-time resolution sea salt measurement capability enabled the quantification of sea salt mass in both increasing and decreasing wind speed regimes up to 26 m s-1. A mass flux source function was also derived and found to have a power law wind speed dependency with an exponent of 3.1 for increasing winds and 2.3 for decreasing winds. Comparison of the mass flux relationship in this study suggests that previous schemes based on the Monahan whitecap–wind speed approach significantly over-estimate the submicron mass flux. Both the whitecap–wind speed component and the differential whitecap–aerosol productivity component of the source flux function contribute toward the over-estimation.

 

(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.

, Detection of Cloud Base Height Using Jenoptik CHM15K and Vaisala CL31 Ceilometers , Detection of Cloud Base Height Using Jenoptik CHM15K and Vaisala CL31 Ceilometers

Date added: 02/08/2011
Date modified: 02/08/2011
Filesize: 8.25 MB

Martucci, G., C. Milroy, and C.D. O’Dowd, Detection of Cloud Base Height Using Jenoptik CHM15K and Vaisala CL31 Ceilometers, J. Atmos. Oceanic Techol. Vol. 27, No. 2, 305–318, 2010.


Abstract Twelve case studies of multi-layer cloud base height (CBH) retrievals from two co-located ceilometers (Vaisala CL31 and Jenoptik CHM15K) have been analysed. The studies were performed during the period from September to December 2008 at the Mace Head Research Station, Ireland. During the period of measurement, the two instruments provided vertical profiles of backscattered laser signal as well as the manufacturer’s operational cloud-base product. The cases selected covered a diverse range of cloud-cover conditions ranging from single to multiple cloud layers and from cloud base heights varying from only a few hundreds metres per day up to 3-5 km in few hours. The results show significant offsets between the two manufacturer-derived CBHs along with a considerable degree of scatter. Using a newly developed Temporal Height-Tracking (THT) algorithm applied to both ceilometers, significant improvement in the correlation between CBH derived from both instruments results in a correlation coefficient increasing to R2 = 0.997 (with a slope of 0.998) from R2 = 0.788 (with associated slope of 0.925). Also, the regression intercept (offset) is reduced from 160 m to effectively zero (-3 m). For the worst individual case study, using the THT algorithm resulted in the correlation coefficient improving from R2 = 0.52, using the manufacturer’s output, to R2 = 0.97 with a reduction in the offset reducing from 569 m to 32 m. Applying the THT algorithm to the backscatter profiles of both instruments led to retrieved cloud bases which are statistically consistent with each other and ensured reliable detection of CBH, particularly when inhomogeneous cloud fields were present and changing rapidly in time. The THT algorithm also overcomes multiple false cloud base detections, associated with the two instruments manufacturer’s output.

 

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.

 

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

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

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


Abstract

 

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

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

 

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.

 

A comparison of PM10 levels at mace head and at Trinity College Dublin A comparison of PM10 levels at mace head and at Trinity College Dublin

Date added: 08/07/2000
Date modified: 07/27/2009
Filesize: 102.39 kB

Finnan J.; McGovern F.M.; O'Leary B.; O'Donnell C.,A comparison of PM10 levels at mace head and at Trinity College Dublin,Journal of Aerosol Science, Volume 31, Supplement 1, September 2000 , pp. 887-888(2)


Abstract


In recent years the role of particulate matter in environmental and health areas has come under increased attention from regulatory and monitoring agencies. This has lead to the introduction of an EC directive on monitoring of PM10 (particulate matter size less than 10 p,m) levels for EU countries. However, the use of PM 10 as a measurement standard has been the subject of considerable debate with lower cut off points, e.g. 2.5 p,m (PM2.5) being considered by many to be of more directly relevant to health issues. Here we present an analysis of PM 10 measurements carried out at two very different sites, i.e. the background site at Mace Head and the central Dublin site of Trinity College Dublin (TCD). Concurrent size distribution data are used to examine the results.

A dedicated study of new particle formation and fate in the coastal environment (PARFORCE) Overview of objectives and initial achievements A dedicated study of new particle formation and fate in the coastal environment (PARFORCE) Overview of objectives and initial achievements

Date added: 07/31/2002
Date modified: 07/27/2009
Filesize: 448.25 kB
C. D. O'Dowd, K. Hämeri, J.M. Mäkelä, M. Kulmala, L. Pirjola, H. Berresheim, S.G. Jennings, H-C Hansson, G. de Leeuw, A.G. Allen, C.N. Hewitt, A. Stroh, and Y. Viisanen. A dedicated study of new particle formation and fate in the coastal environment (PARFORCE): Overview of objectives and initial achievements. J. Geophys. Res. 107, 10.1029/2001000555, 2002.

Abstract


A dedicated study into the formation of new particles, New Particle Formation and Fate in the Coastal Environment (PARFORCE), was conducted over a period from 1998 to 1999 at the Mace Head Atmospheric Research Station on the western coast of Ireland. Continuous measurements of new particle formation were taken over the 2-year period while two intensive field campaigns were also conducted, one in September 1998 and the other in June 1999. New particle events were observed on ∼90% of days and occurred throughout the year and in all air mass types. These events lasted for, typically, a few hours, with some events lasting more than 8 hours, and occurred during daylight hours coinciding with the occurrence of low tide and exposed shorelines. During these events, peak aerosol concentrations often exceeded 106 cm−3 under clean air conditions, while measured formation rates of detectable particle sizes (i.e., d > 3 nm) were of the order of 104–105 cm−3 s−1. Nucleation rates of new particles were estimated to be, at least, of the order of 105–106 cm−3 s−1 and occurred for sulphuric acid concentrations above 2 × 106 molecules cm−3; however, no correlation existed between peak sulphuric acid concentrations, low tide occurrence, or nucleation events. Ternary nucleation theory of the H2SO4-H2O-NH3 system predicts that nucleation rates far in excess of 106 cm−3 s−1 can readily occur for the given sulphuric acid concentrations; however, aerosol growth modeling studies predict that there is insufficient sulphuric acid to grow new particles (of ∼1 nm in size) into detectable sizes of 3 nm. Hygroscopic growth factor analysis of recently formed 8-nm particles illustrate that these particles must comprise some species significantly less soluble than sulphate aerosol. The nucleation-mode hygroscopic data, combined with the lack of detectable VOC emissions from coastal biota, the strong emission of biogenic halocarbon species, and the fingerprinting of iodine in recently formed (7 nm) particles suggest that the most likely species resulting in the growth of new particles to detectable sizes is an iodine oxide as suggested by previous laboratory experiments. It remains an open question whether nucleation is driven by self nucleation of iodine species, a halocarbon derivative, or whether first, stable clusters are formed through ternary nucleation of sulphuric acid, ammonia, and water vapor, followed by condensation growth into detectable sizes by condensation of iodine species. Airborne measurements confirm that nucleation occurs all along the coastline and that the coastal biogenic aerosol plume can extend many hundreds of kilometers away from the source. During the evolution of the coastal plume, particle growth is observed up to radiatively active sizes of 100 nm. Modeling studies of the yield of cloud-condensation nuclei suggest that the cloud condensation nuclei population can increase by ∼100%. Given that the production of new particles from coastal biogenic sources occurs at least all along the western coast of Europe, and possibly many other coastlines, it is suggested that coastal aerosols contribute significantly to the natural background aerosol population.

A dedicated study of New Particle Formation and Fate in the Coastal Environment (PARFORCE): Overview A dedicated study of New Particle Formation and Fate in the Coastal Environment (PARFORCE): Overview

Date added: 08/01/2002
Date modified: 07/21/2009
Filesize: 448.25 kB
O’Dowd, C. D., et al., A dedicated study of New Particle Formation and Fate in the Coastal Environment (PARFORCE):Overview of objectives and achievements, J. Geophys. Res., 107(D19), 8108, doi:10.1029/2001JD000555, 2002Overview of objectives and achievements, J. Geophys. Res., 107(D19), 8108, doi:10.1029/2001JD000555, 2002

Abstract


A dedicated study into the formation of new particles, New Particle Formation and Fate in the Coastal Environment (PARFORCE), was conducted over a period from 1998 to 1999 at the Mace Head Atmospheric Research Station on the western coast of Ireland. Continuous measurements of new particle formation were taken over the 2-year period while two intensive field campaigns were also conducted, one in September 1998 and the other in June 1999. New particle events were observed on ∼90% of days and occurred throughout the year and in all air mass types. These events lasted for, typically, a few hours, with some events lasting more than 8 hours, and occurred during daylight hours coinciding with the occurrence of low tide and exposed shorelines. During these events, peak aerosol concentrations often exceeded 106 cm-3 under clean air conditions, while measured formation rates of detectable particle sizes (i.e., d > 3 nm) were of the order of 104-105 cm-3 s-1. Nucleation rates of new particles were estimated to be, at least, of the Qrder of 105-106 cm-3 s-1and occurred for sulphuric acid concentrations above 2 x 106 molecules cm-3; however, no correlation existed between peak sulphuric acid concentrations, low tide occurrence, or nucleation events. Ternary nucleation theory of the H2SO4-H2O-NH3 system predicts that nucleation rates far in excess of 106 cm-3 s-1 can readily occur for the given sulphuric acid concentrations; however, aerosol growth modeling studies predict that there is insufficient sulphuric acid to grow new particles (of ∼1 nm in size) into detectable sizes of 3 nm. Hygroscopic growth factor analysis of recently formed 8-nm particles illustrate that these particles must comprise some species significantly less soluble than sulphate aerosol. The nucleation-mode hygroscopic data, combined with the lack of detectable VOC emissions from coastal biota, the strong emission of biogenic halocarbon species, and the fingerprinting of iodine in recently formed (7 nm) particles suggest that the most likely species resulting in the growth of new particles to detectable sizes is an iodine oxide as suggested by previous laboratory experiments. It remains an open question whether nucleation is driven by self nucleation of iodine species, a halocarbon derivative, or whether first, stable clusters are formed through ternary nucleation of sulphuric acid, ammonia, and water vapor, followed by condensation growth into detectable sizes by condensation of iodine species. Airborne measurements confirm that nucleation occurs all along the coastline and that the coastal biogenic aerosol plume can extend many hundreds of kilometers away from the source. During the evolution of the coastal plume, particle growth is observed up to radiatively active sizes of 100 nm. Modeling studies of the yield of cloud-condensation nuclei suggest that the cloud condensation nuclei population can increase by ∼100%. Given that the production of new particles from coastal biogenic sources occurs at least all along the western coast of Europe, and possibly many other coastlines, it is suggested that coastal aerosols contribute significantly to the natural background aerosol population.

A detailed case study of isoprene chemistry during the EASE96 A detailed case study of isoprene chemistry during the EASE96

Date added: 08/05/2000
Date modified: 07/27/2009
Filesize: 349.47 kB

Carslaw, N., N. Bell, A.C. Lewis, J.B. McQuaid, and M.J. Pilling, 2000: A detailed case study of isoprene chemistry during the EASE96 Mace Head campaign. Atmos. Environ., 34, 2827-2836, doi:10.1016/S1352-2310(00)00088-1.


Abstract


A detailed chemical mechanism has been used in conjunction with high-quality field measurements in order to assess the potential role of isoprene at a clean coastal Northern Hemisphere site. The importance of isoprene as a source of peroxy radicals, formaldehyde and ozone is discussed in some detail for a case study day (July 17 1996). Between 10:00 and 16:00h GMT, isoprene accounts on average for 15% of the OH removal, yet is responsible for the production of about 30% of the HO2 radicals. Isoprene is also responsible for between 40-60% of the HCHO formation, and 20-40% of the 2 ppb h-1 conversion of NO to NO2 by peroxy radicals. We discuss the significant time lag between HCHO formation and destruction, a time lag that must be accounted for in order to accurately calculate the rate of HO2 production from isoprene degradation, and the implications of the isoprene oxidation for atmospheric chemistry.

 

A general circulation model study of the global carbonaceous aerosol distribution A general circulation model study of the global carbonaceous aerosol distribution

Date added: 08/06/2002
Date modified: 07/27/2009
Filesize: 1.81 MB

Cooke, W. F., V. Ramaswamy, and P. Kasibhatla (2002), A general circulation model study of the global carbonaceous aerosol distribution, J. Geophys. Res., 107(D16), 4279, doi:10.1029/2001JD001274.


Abstract


Atmospheric distributions of carbonaceous aerosols are simulated using the Geophysical Fluid Dynamics Laboratory SKYHI general circulation model (GCM) (latitude-longitude resolution of ∼3° × 3.6°). A number of systematic analyses are conducted to investigate the seasonal and interannual variability of the concentrations at specific locations and to investigate the sensitivity of the distributions to various physical parameters. Comparisons are made with several observational data sets. At four specific sites (Mace Head, Mauna Loa, Sable Island, and Bondville) the monthly mean measurements of surface concentrations of black carbon made over several years reveal that the model simulation registers successes as well as failures. Comparisons are also made with averages of measurements made over varying time periods, segregated by geography and rural/remote locations. Generally, the mean measured remote surface concentrations exceed those simulated. Notwithstanding the large variability in measurements and model simulations, the simulations of both black and organic carbon tend to be within about a factor of 2 at a majority of the sites. There are major challenges in conducting comparisons with measurements due to inadequate sampling at some sites, the generally short length of the observational record, and different methods used for estimating the black and organic carbon amounts. The interannual variability in the model and in the few such measurements available points to the need for doing multiyear modeling and to the necessity of comparing with long-term measurements. There are very few altitude profile measurements; notwithstanding the large uncertainties, the present comparisons suggest an overestimation by the model in the free troposphere. The global column burdens of black and organic carbon in the present standard model integration are lower than in previous studies and thus could be regarded as approximately bracketing a lower end of the simulated anthropogenic burden due to these classes of aerosols, based on the current understanding of the carbonaceous aerosol cycle. Of the physical factors examined, the intensity and frequency of precipitation events are critical in governing the column burdens. Biases in the frequency of precipitation are likely the single biggest cause of discrepancies between simulation and observations. This parameter is available from very few sites and thus lacks a comprehensive global data set, unlike, say, monthly mean precipitation. Several multiyear GCM integrations have been performed to evaluate the sensitivity of the global mean black carbon distribution to the principal aerosol parameters, with due regard to variability and statistical significance. The most sensitive parameters, in order of importance, turn out to be the wet deposition, transformation from hydrophobic to hydrophilic state, and the partitioning of the emitted aerosol between the hydrophobic and hydrophilic varieties. From the sensitivity tests, it is estimated that the variations of the global mean column burden and lifetime of black carbon are within about a factor of 2 about their respective standard values. The studies also show that the column burdens over remote regions appear to be most sensitive to changes in each parameter, reiterating the importance of measurements in those locations for a proper evaluation of model simulation of these aerosols.

 

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

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

Abstract


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

A graphical method for determining the dry-depositional component of aerosol samples and their A graphical method for determining the dry-depositional component of aerosol samples and their

Date added: 08/07/1997
Date modified: 07/27/2009
Filesize: 907.95 kB

Huang, S., K. Rahn, and R. Arimoto. 1997. A graphical method for determining the dry-depositional component of aerosol samples and their field blanks. Atmospheric Environment 31:3383-3394.


Abstract


During the Atmosphere/Ocean Chemistry Experiment (AEROCE), field blanks of certain elements in aerosol samples occasionally increased abruptly, always during periods of unusually high atmospheric concentrations. We hypothesized that the anomalous blanks were created by coarse aerosol entering the sampling shelters and depositing onto the blank filters. If so, samples taken nearby should have been similarly affected. To test this hypothesis, we developed a simple graphical method in which elemental masses in field blanks are plotted against elemental masses in pumped samples, and zones of proportionality between the two are sought. Data from Bermuda and Mace Head (coastal western Ireland) confirmed that depositional zones did indeed appear, but only for coarse-particle elements and only under certain conditions. Actual increases of crustal and pollution-derived elements agreed well with values predicted from settling velocities and sampling rates: blanks increased up to an order of magnitude or more but samples by less than 1%. Marine elements behaved like crustal elements in most samples but occasionally were much more enriched: blanks increased up to 30-fold and samples up to about 3%. It thus appears that when coarse-particle elements are present in high concentrations, their field blanks and samples may be measurably affected by dry deposition. Depending on the elements of interest, this dry deposition may have to be measured and the concentrations corrected.

 

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

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

Abstract


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

A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE

Date added: 01/01/2000
Date modified: 07/27/2009
Filesize: 4.55 MB
Prinn, R. G., et al. (2000), A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE, J. Geophys. Res., 105(D14), 17,751–17,792.

Abstract


We describe in detail the instrumentation and calibrations used in the Atmospheric Lifetime Experiment (ALE), the Global Atmospheric Gases Experiment (GAGE), and the Advanced Global Atmospheric Gases Experiment (AGAGE) and present a history of the majority of the anthropogenic ozone-depleting and climate-forcing gases in air based on these experiments. Beginning in 1978, these three successive automated high-frequency in situ experiments have documented the long-term behavior of the measured concentrations of these gases over the past 20 years, and show both the evolution of latitudinal gradients and the high-frequency variability due to sources and circulation. We provide estimates of the long-term trends in total chlorine contained in long-lived halocarbons involved in ozone depletion. We summarize interpretations of these measurements using inverse methods to determine trace gas lifetimes and emissions. Finally, we provide a combined observational and modeled reconstruction of the evolution of chlorocarbons by latitude in the atmosphere over the past 60 years which can be used as boundary conditions for interpreting trapped air in glaciers and oceanic measurements of chlorocarbon tracers of the deep oceanic circulation. Some specific conclusions are as follows: (1) International compliance with the Montreal Protocol is so far resulting in chlorofluorocarbon and chlorocarbon mole fractions comparable to target levels; (2) mole fractions of total chlorine contained in long-lived halocarbons (CCl2F2, CCl3F, CH3CCl3, CCl4, CHClF2, CCl2FCClF2, CH3Cl, CH2Cl2, CHCl3, CCl2=CCl2) in the lower troposphere reached maximum values of about 3.6 ppb in 1993 and are beginning to slowly decrease in the global lower atmosphere; (3) the chlorofluorocarbons have atmospheric lifetimes consistent with destruction in the stratosphere being their principal removal mechanism; (4) multiannual variations in chlorofluorocarbon and chlorocarbon emissions deduced from ALE/GAGE/AGAGE data are consistent approximately with variations estimated independently from industrial production and sales data where available (CCl2F2 (CFC-12) and CCl2FCClF2 (CFC-113) show the greatest discrepancies); (5) the mole fractions of the hydrochlorofluorocarbons and hydrofluorocarbons, which are replacing the regulated halocarbons, are rising very rapidly in the atmosphere, but with the exception of the much longer manufactured CHClF2 (HCFC-22), they are not yet at levels sufficient to contribute significantly to atmospheric chlorine loading. These replacement species could in the future provide independent estimates of the global weighted-average OH concentration provided their industrial emissions are accurately documented; (6) in the future, analysis of pollution events measured using high-frequency in situ measurements of chlorofluorocarbons and their replacements may enable emission estimates at the regional level, which, together with industrial end-use data, are of sufficient accuracy to be capable of identifying regional noncompliance with the Montreal Protocol.

A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE

Date added: 01/01/2000
Date modified: 07/23/2009
Filesize: 4.55 MB
Prinn, R. G., et al. (2000), A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE, J. Geophys. Res., 105(D14), 17,751–17,792.

Abstract


We describe in detail the instrumentation and calibrations used in the Atmospheric Lifetime Experiment (ALE), the Global Atmospheric Gases Experiment (GAGE), and the Advanced Global Atmospheric Gases Experiment (AGAGE) and present a history of the majority of the anthropogenic ozone-depleting and climate-forcing gases in air based on these experiments. Beginning in 1978, these three successive automated high-frequency in situ experiments have documented the long-term behavior of the measured concentrations of these gases over the past 20 years, and show both the evolution of latitudinal gradients and the high-frequency variability due to sources and circulation. We provide estimates of the long-term trends in total chlorine contained in long-lived halocarbons involved in ozone depletion. We summarize interpretations of these measurements using inverse methods to determine trace gas lifetimes and emissions. Finally, we provide a combined observational and modeled reconstruction of the evolution of chlorocarbons by latitude in the atmosphere over the past 60 years which can be used as boundary conditions for interpreting trapped air in glaciers and oceanic measurements of chlorocarbon tracers of the deep oceanic circulation. Some specific conclusions are as follows: (1) International compliance with the Montreal Protocol is so far resulting in chlorofluorocarbon and chlorocarbon mole fractions comparable to target levels; (2) mole fractions of total chlorine contained in long-lived halocarbons (CCl2F2, CCl3F, CH3CCl3, CCl4, CHClF2, CCl2FCClF2, CH3Cl, CH2Cl2, CHCl3, CCl2=CCl2) in the lower troposphere reached maximum values of about 3.6 ppb in 1993 and are beginning to slowly decrease in the global lower atmosphere; (3) the chlorofluorocarbons have atmospheric lifetimes consistent with destruction in the stratosphere being their principal removal mechanism; (4) multiannual variations in chlorofluorocarbon and chlorocarbon emissions deduced from ALE/GAGE/AGAGE data are consistent approximately with variations estimated independently from industrial production and sales data where available (CCl2F2 (CFC-12) and CCl2FCClF2 (CFC-113) show the greatest discrepancies); (5) the mole fractions of the hydrochlorofluorocarbons and hydrofluorocarbons, which are replacing the regulated halocarbons, are rising very rapidly in the atmosphere, but with the exception of the much longer manufactured CHClF2 (HCFC-22), they are not yet at levels sufficient to contribute significantly to atmospheric chlorine loading. These replacement species could in the future provide independent estimates of the global weighted-average OH concentration provided their industrial emissions are accurately documented; (6) in the future, analysis of pollution events measured using high-frequency in situ measurements of chlorofluorocarbons and their replacements may enable emission estimates at the regional level, which, together with industrial end-use data, are of sufficient accuracy to be capable of identifying regional noncompliance with the Montreal Protocol.

A method of measurement of the Dielectric Constant of some liquids A method of measurement of the Dielectric Constant of some liquids

Date added: 01/01/1977
Date modified: 08/06/2009
Filesize: 1.3 MB

Jennings S.G., A method of measurement of the dielectric constant of some liquids. Phys. Educ. Vol 12, January 1977. pp. 40-42.


Abstract


The method depends on the existence of a driving force on a liquid dielectric in an electric field. The force leads to a rise in the liquid level between the plates of a capacitor. The capacitor plates were placed just above a reservoir of the dielectric liquid, the level of which was monitored by a travelling microscope. The rise in liquid level (h) was measured for selected values of voltage (v) until sparking between the plates occurred. A plot of h against V2 was obtained, and the dielectric constant was determined from the slope of the graph.

A model prediction of the yield of CCN from coastal nucleation events A model prediction of the yield of CCN from coastal nucleation events

Date added: 07/31/2002
Date modified: 07/27/2009
Filesize: 352.77 kB
Liisa Pirjola, Colin O'Dowd, Markku Kulmala, A model prediction of the yield of CCN from coastal nucleation events, J. Geophys. Res., 107, 10.1029/2000JD000213, 2002.

Abstract


The formation and evolution of new particles during coastal nucleation events are examined using the aerosol dynamic and gas-phase chemistry model AEROFOR2. Coastal regions are known to be a strong source of natural aerosol particles and are also strong sources of biogenic vapors which can condense onto aerosol particles, thus resulting in particle growth. A number of model simulations were performed to determine the instantaneous nucleation rate along with the source rate of a generic biogenic vapor leading to the observed particle size distributions which indicate the rapid appearance of ∼105–106 cm−3 nucleation mode particles in this environment. Model calculations suggest values of 3 × 105 cm−3 s−1 to 3 × 106 cm−3 s−1 for the instantaneous nucleation rate and a value of 5 × 107 cm−3 s−1 for the condensable vapor source rate in order to reproduce the observed concentrations. A significant fraction of these new particles survive to grow into cloud condensation nuclei (CCN) sizes for supersaturations typically encountered in boundary layer clouds during subsequent evolution over 3 days under clear-sky conditions, thus contributing to the indirect radiative effect of aerosols. The amount of CCN is mainly affected by coagulation between particles and condensation of the biogenic vapor and, to a lesser extent, by condensation of sulphuric acid formed by DMS oxidation. In all simulated cases, an increase of more than 100% in CCN concentration, for supersaturations >0.35% was observed.

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

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

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


Abstract


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

 

A Photoelectric Condensation Nucleus Counter On High Precision A Photoelectric Condensation Nucleus Counter On High Precision

Date added: 08/07/1955
Date modified: 07/13/2009
Filesize: 4.73 MB
L.w Pollak & Tc O'Connor, A Photoelectric Condensation Nucleus Counter On High Precision, Geofisica Pura E Applicata Milano Vol. 32 pp 139-146

Abstract

 

A new model of the direct beam photo-electrix condensation nucleus counter and itsproperties are described. the main feature of the construction is the reduction of the fog tube diameter which resulted in the elimination of all uncertainties in the measurement of the light intensity after the fog is formed by adiabatic expansion.- Individual measurements with two identical of this design which incorporate all previous improvements, agree to better than 5% in 70% in all cases, their aver absolute difference being 2%. Deviations of more than one division of meter reading (or 10% of concentration) were not observed, This agreement is maintained over long periods. - A calibration curve of the latest model of the photo-electric nucleus counter is given

A Statistical Analysis of North East Atlantic (submicron) Aerosol Size Distributions A Statistical Analysis of North East Atlantic (submicron) Aerosol Size Distributions

Date added: 03/19/2013
Date modified: 03/19/2013
Filesize: 516.78 kB

Dall’Osto, M., C. Monahan, R. Greaney, D.C.S. Beddows, R. M. Harrison, D. Ceburnis and C. D. O’Dowd. A Statistical Analysis of North East Atlantic (submicron) Aerosol Size Distributions., Atmos. Chem. Phys., 11, 12567–12578, 2011, doi:10.5194/acp-11-12567-2011.


Abstract. The Global Atmosphere Watch research station at Mace Head (Ireland) offers the possibility to sample some of the cleanest air masses being imported into Europe as well as some of the most polluted being exported out of Europe. We present a statistical cluster analysis of the physical characteristics of aerosol size distributions in air ranging from the cleanest to the most polluted for the year 2008. Data coverage achieved was 75% throughout the year. By applying the Hartigan-Wong k-Means method, 12 clusters were identified as systematically occurring. These 12 clusters could be further combined into 4 categories with similar characteristics, namely: coastal nucleation category (occurring 21.3% of the time), open ocean nucleation category (occurring 32.6% of the time), background clean marine category (occurring 26.1% of the time) and anthropogenic category (occurring 20% of the time) aerosol size distributions. The coastal nucleation category is characterised by a clear and dominant nucleation mode at sizes less than 10 nm while the open ocean nucleation category is characterised by a dominant Aitken mode between 15 nm and 50 nm. The background clean marine aerosol exhibited a clear bimodality in the sub-micron size distribution, with although it should be noted that either the Aitken mode or the accumulation mode may dominate the number concentration. However, peculiar background clean marine size distributions with coarser accumulation modes are also observed during winter months. By contrast, the continentally-influenced size distributions are generally more monomodal (accumulation), albeit with traces of bimodality. The open ocean category occurs more often during May, June and July, corresponding with the North East (NE) Atlantic high biological period. Combined with the relatively high percentage frequency of occurrence (32.6 %), this suggests that the marine biota is an important source of new nano aerosol particles in NE Atlantic Air.

 

A study of peroxy radicals and ozone photochemistry at coastal sites in the northern and southe A study of peroxy radicals and ozone photochemistry at coastal sites in the northern and southe

Date added: 08/06/1997
Date modified: 07/27/2009
Filesize: 1.01 MB

Carpenter, L. J., P. S. Monks, B. J. Bandy, S. A. Penkett, I. E. Galbally, and C. P. (. Meyer (1997), A study of peroxy radicals and ozone photochemistry at coastal sites in the northern and southern hemispheres, J. Geophys. Res., 102(D21), 25,417–25,427.


Abstract


Peroxy radicals and other important species relevant to ozone photochemistry, including ozone, its photolysis rate coefficient jO(1 D), NOx (NO + NO2), and peroxides, were measured at the coastal sites of Cape Grim, Tasmania, in January/February 1995 during the Southern Ocean Atmospheric Photochemistry Experiment (SOAPEX 1) and Mace Head, Western Ireland, in May 1995 during the Atlantic Atmospheric Photochemistry Experiment (ATAPEX 1). At both sites it was observed that the relationship between peroxy radical (HO2 + RO2) concentrations and jO(1 D) switched from a square root dependence in clean oceanic or “baseline” air to a first-order dependence in more polluted air. Simple algorithms derived from a photochemical reaction scheme indicate that this switch-over occurs when atmospheric NO levels are sufficient for peroxy radical reaction with NO to compete with radical recombination reactions. At this crucial point, net tropospheric ozone production is expected to occur and was observed in the ozone diurnal cycles when the peroxy radical/jO(1 D) dependencies became first order. The peroxy radical/jO(1 D) relationships imply that ozone production exceeds destruction at NO levels of 55±30 parts per trillion by volume (pptv) at Mace Head during late spring and 23±20 pptv at Cape Grim during summer, suggesting that the tropospheric ozone production potential of the southern hemisphere is more responsive to the availability of NO than that of the northern hemisphere.

 

A two-column method for long-term monitoring of non-methanehydrocarbons (NMHCs) and oxygenated volat A two-column method for long-term monitoring of non-methanehydrocarbons (NMHCs) and oxygenated volat

Date added: 08/31/2003
Date modified: 07/23/2009
Filesize: 174.39 kB

Hopkins, J. R., Read, K. A., and Lewis, A. C.: A Two Column Method for Long-term Monitoring of Non-Methane Hydrocarbons (NMHCs) and Oxygenated Volatile Organic Compounds, J. Envir. Mon., 5, 8–13, 2003.


Abstract


 

A method has been developed for concurrent analysis of C2–C7 hydrocarbons and C2–C5 oxygenated volatile organic compounds (o-VOCs) including alcohols, aldehydes, ketones and ethers. A multi-bed, Peltier-cooled adsorbent trap, consisting of Carboxen 1000 and Carbopack B, was used to acquire one sample per hour. Upon injection the sample was split in an approximately 50 : 50 ratio between a 50 m aluminium oxide (Al2O3) porous layer open tubular (PLOT) column and a 10 m LOWOX column. Eluents from each column were then analysed using flame ionisation detection (FID). Regular calibration of the system was performed using a standard cylinder mixture at the parts per billion by volume (ppbV) level for non-methane hydrocarbons (NMHCs) and a permeation tube method for the oxygenated species. The system is fully automated with NMHC detection limits between 1 and 10 parts per trillion by volume (pptV) and o-VOC detection limits between 10 and 40 pptV.

Accelerated Rates of Rainfall Accelerated Rates of Rainfall

Date added: 07/09/1971
Date modified: 06/30/2009
Filesize: 384.37 kB
P. R. BRAZIER-SMITH, S. G. JENNINGS & J. LATHAM, Accelerated Rates of Rainfall,  Nature 232, 112 - 113 (09 July 1971); doi:10.1038/232112b0

Abstract

 

RAINFALL intensity within clouds may be greatly increased by the production of satellite drops when raindrops collide, and this process could explain the extremely high rates of rainfall development reported in certain clouds1,2. We have set out to test this possibility by laboratory experiments.

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.

Advance, 12 the growth of snowflakes and hail Advance, 12 the growth of snowflakes and hail

Date added: 06/01/1972
Date modified: 08/01/2008
Filesize: 330.33 kB

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

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

Abstract


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

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.

 

 

 

 

 

 

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

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

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


Abstract


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

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

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

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


Abstract


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

 

Aerosol decadal trends – Part 1: In-situ optical measurements at GAW and IMPROVE stations Aerosol decadal trends – Part 1: In-situ optical measurements at GAW and IMPROVE stations

Date added: 03/12/2013
Date modified: 03/12/2013
Filesize: 2.64 MB

Collaud Coen, M., E. Andrews, A. Asmi, U. Baltensperger, N. Bukowiecki, D. Day, M. Fiebig, A. M. Fjaeraa, H. Flentje, A. Hyvärinen, A. Jefferson, S. G. Jennings, G. Kouvarakis, H. Lihavainen, C. Lund Myhre, W. C. Malm, N. Mihapopoulos, J. V. Molenar, C. O'Dowd, J. A. Ogren, B. A. Schichtel, P. Sheridan, A. Virkkula, E. Weingartner, R. Weller, and P. Laj,Aerosol decadal trends – Part 1: In-situ optical measurements at GAW and IMPROVE stations, Atmos. Chem. Phys., 13, 869-894, 2013, www.atmos-chem-phys.net/13/869/2013/doi:10.5194/acp-13-869-2013.


Abstract. Currently many ground-based atmospheric stations include in-situ measurements of aerosol physical and optical properties, resulting in more than 20 long-term (> 10 yr) aerosol measurement sites in the Northern Hemisphere and Antarctica. Most of these sites are located at remote locations and monitor the aerosol particle number concentration, wavelength-dependent light scattering, backscattering, and absorption coefficients. The existence of these multi-year datasets enables the analysis of long-term trends of these aerosol parameters, and of the derived light scattering Ångström exponent and backscatter fraction. Since the aerosol variables are not normally distributed, three different methods (the seasonal Mann-Kendall test associated with the Sen's slope, the generalized least squares fit associated with an autoregressive bootstrap algorithm for confidence intervals, and the least-mean square fit applied to logarithms of the data) were applied to detect the long-term trends and their magnitudes. To allow a comparison among measurement sites, trends on the most recent 10 and 15 yr periods were calculated. No significant trends were found for the three continental European sites. Statistically significant trends were found for the two European marine sites but the signs of the trends varied with aerosol property and location. Statistically significant decreasing trends for both scattering and absorption coefficients (mean slope of −2.0% yr−1) were found for most North American stations, although positive trends were found for a few desert and high-altitude sites. The difference in the timing of emission reduction policy for the Europe and US continents is a likely explanation for the decreasing trends in aerosol optical parameters found for most American sites compared to the lack of trends observed in Europe. No significant trends in scattering coefficient were found for the Arctic or Antarctic stations, whereas the Arctic station had a negative trend in absorption coefficient. The high altitude Pacific island station of Mauna Loa presents positive trends for both scattering and absorption coefficients.

 

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.

 

Aerosol deposition in turbulent channel flow on a regular array of three-dimensional roughness elements Aerosol deposition in turbulent channel flow on a regular array of three-dimensional roughness elements

Date added: 07/31/2001
Date modified: 06/30/2009
Filesize: 527.45 kB
Lai, A.C.K., Byrne, M.A. and Goddard, A.J.H. Aerosol deposition in turbulent channel flow on a regular array of three-dimensional roughness elements. J. Aerosol Sci., 32, 121-137, 2001.

Abstract


Understanding particle deposition onto rough surfaces is important for many engineering and environmental applications. An experimental system was designed for the study of aerosol deposition on regular arrays of uniform elements (in the form of discrete protrusions) in a turbulent ventilation duct flow using monodisperse tracer small particles, in the range 0.7-7.1mum. The Reynolds number for the test conditions was 44,000 in the 150 mm square duct. The roughness elements were arranged at two different orientations with respect to the airflow direction and the aerosol deposition velocity and pressure drop were measured for both orientations. Compared to earlier measurements in the same duct system involving smooth or ribbed surfaces, a significant increase in deposition velocity onto the regular roughness elements is observed. In addition, the associated pressure loss penalty is lower than in the presence of the roughness elements than in the presence of the ribbed surfaces. This may be attributable to the small dimensionless roughness height of the elements, which results only in a moderate distortion of the flow structure near the surfaces.

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.

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.

Aerosol dynamics in ship tracks Aerosol dynamics in ship tracks

Date added: 08/06/1999
Date modified: 07/23/2009
Filesize: 1.65 MB

Russell, L. M. ; Seinfeld, J. H. ; Flagan, R. C. ; Ferek, R. J. ; Hegg, D. A. ; Hobbs, P. V. ;  Wobrock, W. ;  Flossmann, A. I. ; O'Dowd, C. D. ; Nielsen, K. E. ; Durkee, P. A.  1999 Aerosol dynamics in ship tracks J. Geophys. Res. Vol. 104 , No. D24 , p. 31,077-31096 DOI 10.1029/1999JD900985


Abstract

 

Ship tracks are a natural laboratory to isolate the effect of anthropogenic aerosol emissions on cloud properties. The Monterey Area Ship Tracks (MAST) experiment in the Pacific Ocean west of Monterey, California, in June 1994, provides an unprecedented data set for evaluating our understanding of the formation and persistence of the anomalous cloud features that characterize ship tracks. The data set includes conditions in which the marine boundary layer is both clean and continentally influenced. Two case studies during the MAST experiment are examined with a detailed aerosol microphysical model that considers an external mixture of independent particle populations. The model allows tracking individual particles through condensational and coagulational growth to identify the source of cloud condensation nuclei (CCN). In addition, a cloud microphysics model was employed to study specific effects of precipitation. Predictions and observations reveal important differences between clean (particle concentrations below 150 cm-3) and continentally influenced (particle concentrations above 400 cm-3) background conditions: in the continentally influenced conditions there is a smaller change in the cloud effective radius, drop number and liquid water content in the ship track relative to the background than in the clean marine case. Predictions of changes in cloud droplet number concentrations and effective radii are consistent with observations although there is significant uncertainty in the absolute concentrations due to a lack of measurements of the plume dilution. Gas-to-particle conversion of sulfur species produced by the combustion of ship fuel is predicted to be important in supplying soluble aerosol mass to combustion-generated particles, so as to render them available as CCN. Studies of the impact of these changes on the cloud's potential to precipitate concluded that more complex dynamical processes must be represented to allow sufficiently long drop activations for drizzle droplets to form.

Aerosol formation during PARFORCE: Ternary nucleation of H2SO4, NH3 and H2O Aerosol formation during PARFORCE: Ternary nucleation of H2SO4, NH3 and H2O

Date added: 07/31/2002
Date modified: 07/27/2009
Filesize: 354.52 kB
Markku Kulmala, Pekka Korhonen, Ismo Napari, Robert Jansson, Harald Berresheim, and Colin O'Dowd, Aerosol formation during PARFORCE: Ternary nucleation of H2SO4, NH3 and H2O, J. Geophys. Res., 107, 10.1029/2001JD000900, 2002.

Abstract


A new version of a ternary nucleation (sulphuric acid-ammonia-water) model based on classical nucleation theory, but with an improved ability to predict nucleation rates over a larger temperature range (258–303 K) compared with previous work, is presented. The modeled nucleation rates are given as a function of temperature and ambient acid and ammonia concentrations. For the first time the predicted ternary nucleation rates are compared to the observed particle production rates using measured ambient sulphuric acid and ammonia concentrations as input data. The ambient gas concentrations were measured simultaneously to aerosol formation rates during the 1999 New Particle Formation and Fate in the Coastal Environment (PARFORCE) coastal field campaign at Mace Head. According to the results, daytime ambient acid and ammonia concentrations were significantly higher than required by model calculations to induce the formation of new particles by homogeneous ternary nucleation. However, binary nucleation of sulphuric acid-water molecules is not able to predict new particle formation since the binary nucleation rate is far too small. We conclude that all particle formation events observed at coastal sites can be initiated by ternary nucleation of sulphuric acid, ammonia, and water vapor. However, related studies illustrate that ambient sulphuric acid concentrations are, nevertheless, insufficient to explain observed rapid growth of particles from 1 to 3 nm sizes which can be detected by current instrumentation.

Aerosol generation by waves breaking on small islands and rocks near the mace head research sta Aerosol generation by waves breaking on small islands and rocks near the mace head research sta

Date added: 08/07/2000
Date modified: 07/27/2009
Filesize: 150.69 kB

Kunz, GJ, CD O'Dowd, G de Leeuw, Aerosol generation by waves breaking on small islands and rocks near the Mace Head research station. European Aerosol Conference, 2000, J. Aerosol. Sci., Suppl 1., 656-657, 2000. [36] Kleefeld, C., S O'Rielly, SG Jennings, E Becker, C O'Dowd, G Kunz and G de Leeuw, Aerosol scattering: relation to primary and secondary aerosol production in the coastal atmosphere during the PARFORCE campaign, European Aerosol Conference, 2000, J. Aerosol. Sci., Suppl 1., 658-659, 2000.


Abstract


Two coastal field experiments (September 1998 and in June 1999) were conducted at Mace Head, Ireland, under the EU-funded PARFORCE (New P__._~icle Formation and Fate in the Coastal Environment) programme which was designed to elucidate the processes which control and promote homogeneous heteromolecular nucleation in the coastal boundary layer. During conditions of westerly winds and after sufficiently long fetch, the Mace Head station is regularly exposed to pure maritime and clean arctic atmospheres. Under these conditions the generation and growth of new particles due to photochemical conversion of biological emissions is seen to occur on almost a daily basis (e.g., O'Dowd et al., 1998 and O'Dowd et al., 1999). During the PARFORCE experiments the TNO Physics and Electronics Laboratory (TNO-FEL) undertook to measure boundary layer dynamics, as determined from the aerosol structures measured with a lidar (light detection and ranging) system. The results revealed the generation of large amounts of sea spray Aerosol by waves breaking on the islands and roCks near the Mace Head station. The location, size and dynamics of these locally generated aerosol plumes were determined from series of consecutive horizontal and vertical scans. The horizontal extent of these aerosol plumes is highly coherent over distances of several kilometres and the vertical extent is generally between a few tens of meters to a few hundreds of meters. In some occasions the aerosol was observed to be taken aloft to the top of the mixed layer at an altitude of about one kilometre.

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.

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

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

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


Abstract


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

Aerosol Optical Depth in Clean and Polluted Northeast Atlantic Air Aerosol Optical Depth in Clean and Polluted Northeast Atlantic Air

Date added: 11/06/2009
Date modified: 11/06/2009
Filesize: 250.56 kB

Mulcahy, J. P., C. D. O’Dowd, and S. G. Jennings (2009), Aerosol optical depth in clean marine and continental northeast Atlantic air, 114, D20204, doi:10.1029/2009JD011992. J. Geophys. Res.


Abstract.

The aerosol optical depth (AOD) and A ° ngstro¨m exponent for the period 2002–2004 is evaluated for clean marine and continentally influenced air masses over the northeast Atlantic region. Measurements were carried out at the Mace Head atmospheric research station on the west coast of Ireland using a precision filter radiometer which measures the aerosol optical depth at four wavelengths centered at 368, 412, 500, and 862 nm. The clean marine AOD at 500 nm is characterized by a mean value of 0.14 ±0.06, exhibiting relatively small temporal variability. The A ° ngstro¨m exponent was less than 1 for the majority of cases, having an average value of 0.40 ± 0.29 in clean marine conditions. The latter is consistent with the presence of relatively large supermicron particles, such as sea salt dominating the marine aerosol size distribution. The A ° ngstro¨m exponent shows a distinct seasonal cycle in clean marine air, with maximum values being derived in the summer months and minimum values in the winter. In continental air masses, while the range and standard deviation of the AOD is larger than in clean marine conditions, the overall mean AOD (

t500 = 0.19 ± 0.12) is comparable with the clean marine AOD. The continental A ° ngstro¨m exponent is larger, having a mean value of 1.07 ± 0.32. This is attributed to a dominating accumulation mode in the presence of urban-industrial aerosol particles originating mainly from continental Europe. These results demonstrate how the natural marine AOD can rival polluted AOD over the northeast Atlantic region and highlight the importance of the natural marine aerosol contribution over oceans.

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

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

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


Abstract


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

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

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

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

Aerosol physico-chemical characteristics over a boreal forest determined by volatility analysis Aerosol physico-chemical characteristics over a boreal forest determined by volatility analysis

Date added: 07/31/2000
Date modified: 06/30/2009
Filesize: 154.04 kB

O'Dowd, C.D., E. Becker, J.M. Makela, M. Kulmala, Aerosol physic-chemical characteristics over a boreal forest determined by volatility analysis, Boreal Environment Research, 4, 337-348, 2000


Abstract


A thermal volatility technique was used in the boreal forest environment to examine accumulation mode (0.05–0.35 µm radius) physico-chemical properties as a function of air mass origin. Three primary aerosol species were identified in all air masses: (1) a semi-volatile organic component, (2) ammonium sulphate, and (3) a non-volatile component thought to comprise mostly of soot carbon. Under some conditions, sulphuric acid was also identified, as was sea salt. Following nucleation and growth of new particles into accumulation mode sizes, the organic fraction of accumulation mode aerosol, by mass, was observed to increase from 30%, prior to and during the nucleation event, up to 75% by the end of the growth period, indicating a substantial fraction of organic mass condensing onto newly formed particles.

Aerosol properties associated with air masses arriving into the North East Atlantic during the 2008 Aerosol properties associated with air masses arriving into the North East Atlantic during the 2008

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 7.27 MB

Dall’Osto,M.,  D. Ceburnis, G. Martucci, J. Bialek, R. Dupuy, S. G. Jennings, H. Berresheim, J. C. Wenger, R. M. Healy, M. C. Facchini, M. Rinaldi, L. Giulianelli, E. Finessi, D. Worsnop, M. Ehn, J. Mikkil¨a, M. Kulmala, J. Sodeau, and C. D. O’Dowd, , Aerosol properties associated with air masses arriving into the North East Atlantic during the 2008 Mace Head EUCAARI intensive observing period: an overview Atmos. Chem. Phys., 10, 8413-8435, doi:10.5194/acp-10-8413-2010, 2010.


Abstract.

 

As part of the EUCAARI Intensive Observing Period, a 4-week campaign to measure aerosol physical, chemical and optical properties, atmospheric structure, and cloud microphysics was conducted from mid-May to mid-June, 2008 at the Mace Head Atmospheric Research Station, located

at the interface of Western Europe and the N. E. Atlantic and centered on the west Irish coastline. During the campaign, continental air masses comprising both young and aged continental plumes were encountered, along with polar, Arctic and tropical air masses. Polluted-continental aerosol

concentrations were of the order of 3000 cm

 

3, while background marine air aerosol concentrations were between 400– 600 cm3. The highest marine air concentrations occurred in polar air masses in which a 15 nm nucleation mode, with concentration of 1100 cm3, was observed and attributed to open ocean particle formation. Continental air submicron chemical composition (excluding refractory sea salt) was dominated by organic matter, closely followed by sulphate mass.  Although the concentrations and size distribution spectral shape were almost identical for the young and aged continental cases, hygroscopic growth factors (GF) and cloud condensation nuclei (CCN) to total condensation nuclei (CN) concentration ratios were significantly less in the younger pollution plume, indicating a more oxidized organic component to the aged continental plume. The difference in chemical composition and hygroscopic growth factor appear to result in a 40–50% impact on aerosol scattering coefficients and Aerosol Optical Depth, despite almost identical aerosol microphysical properties in both cases, with the higher valuesb been recorded for the more aged case. For the CCN/CN ratio, the highest ratios were seen in the more age plume. In marine air, sulphate mass dominated the sub-micron component, followed by water soluble organic carbon, which, in turn, was dominated by methanesulphonic acid (MSA). Sulphate concentrations were highest in marine tropical air – even higher than in continental air. MSA was present at twice the concentrations of previously-reported concentrations at the same location and the same season. Both continental and marine air exhibited aerosol GFs significantly less than ammonium sulphate aerosol pointing to a significant organic contribution to all air mass aerosol properties.

AGAGE Observations of Methyl Bromide and Methyl Chloride at Mace Head, Ireland, and Cape Grim, Tasmania, 1998–2001 AGAGE Observations of Methyl Bromide and Methyl Chloride at Mace Head, Ireland, and Cape Grim, Tasmania, 1998–2001

Date added: 08/01/2004
Date modified: 07/27/2009
Filesize: 593.54 kB

Simmonds, P.; Derwent, R.; Manning, A.; Fraser, P.; Krummel, P.; O'Doherty, S.; Prinn, R.; Cunnold, D.; Miller, B.; Wang, H.; Ryall, D.; Porter, L.; Weiss, R.; Salameh, P. ,AGAGE Observations of Methyl Bromide and Methyl Chloride at Mace Head, Ireland, and Cape Grim, Tasmania, 1998–2001, Journal of Atmospheric Chemistry, pg 1573-0662


Abstract


In situ AGAGE GC-MS measurements of methyl bromide (CH3Br) and methyl chloride (CH3Cl) at Mace Head, Ireland and Cape Grim, Tasmania (1998–2001) reveal a complex pattern of sources. At Mace Head both gases have well-defined seasonal cycles with similar average annual decreases of 3.0% yr−1 (CH3Br) and 2.6% yr−1 (CH3Cl), and mean northern hemisphere baseline mole fractions of 10.37 ± 0.05 ppt and 535.7 ± 2.2 ppt, respectively. We have used a Lagrangian dispersion model and local meteorological data to segregate the Mace Head observations into different source regions, and interpret the results in terms of the known sources and sinks of these two key halocarbons. At Cape Grim CH3Br and CH3Cl also show annual decreases in their baseline mixing ratios of 2.5% yr−1 and 1.5% yr−1, respectively. Mean baseline mole fractions were 7.94 ± 0.03 ppt (CH3Br) and 541.3 ± 1.1 ppt (CH3Cl). Although CH3Cl has astrong seasonal cycle there is no well-defined seasonal cycle in the Cape Grim CH3Br record. The fact that both gases are steadily decreasing in the atmosphere at both locations implies that a change has occurred which is affecting a common, major source of both gases (possibly biomass burning) and/or their major sink process (destruction by hydroxyl radical).

AGAGE Observations of Methyl Bromide and Methyl Chloride at Mace Head, Ireland, and Cape Grim, Tasmania, 1998–2001 AGAGE Observations of Methyl Bromide and Methyl Chloride at Mace Head, Ireland, and Cape Grim, Tasmania, 1998–2001

Date added: 08/01/2004
Date modified: 06/30/2009
Filesize: 593.54 kB

Simmonds, P.; Derwent, R.; Manning, A.; Fraser, P.; Krummel, P.; O'Doherty, S.; Prinn, R.; Cunnold, D.; Miller, B.; Wang, H.; Ryall, D.; Porter, L.; Weiss, R.; Salameh, P. ,AGAGE Observations of Methyl Bromide and Methyl Chloride at Mace Head, Ireland, and Cape Grim, Tasmania, 1998–2001, Journal of Atmospheric Chemistry, pg 1573-0662


Abstract


In situ AGAGE GC-MS measurements of methyl bromide (CH3Br) and methyl chloride (CH3Cl) at Mace Head, Ireland and Cape Grim, Tasmania (1998–2001) reveal a complex pattern of sources. At Mace Head both gases have well-defined seasonal cycles with similar average annual decreases of 3.0% yr−1 (CH3Br) and 2.6% yr−1 (CH3Cl), and mean northern hemisphere baseline mole fractions of 10.37 ± 0.05 ppt and 535.7 ± 2.2 ppt, respectively. We have used a Lagrangian dispersion model and local meteorological data to segregate the Mace Head observations into different source regions, and interpret the results in terms of the known sources and sinks of these two key halocarbons. At Cape Grim CH3Br and CH3Cl also show annual decreases in their baseline mixing ratios of 2.5% yr−1 and 1.5% yr−1, respectively. Mean baseline mole fractions were 7.94 ± 0.03 ppt (CH3Br) and 541.3 ± 1.1 ppt (CH3Cl). Although CH3Cl has astrong seasonal cycle there is no well-defined seasonal cycle in the Cape Grim CH3Br record. The fact that both gases are steadily decreasing in the atmosphere at both locations implies that a change has occurred which is affecting a common, major source of both gases (possibly biomass burning) and/or their major sink process (destruction by hydroxyl radical).

Air Pollution Measurements at Macehead Air Pollution Measurements at Macehead

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

Air Pollution Measurements at Macehead Air Pollution Measurements at Macehead

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