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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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Seasonal variation of carbon monoxide at remote sites in Japan Seasonal variation of carbon monoxide at remote sites in Japan

Date added: 08/07/1999
Date modified: 07/23/2009
Filesize: 183.89 kB
Narita D.; Pochanart P.; Matsumoto J.; Someno K.; Tanimoto H.; Hirokawa J.; Seasonal variation of carbon monoxide at remote sites in Japan, Chemosphere: Global Science Change, Volume 1, Number 1, August 1999 , pp. 137-144(8)

Abstract


Continuous measurement of CO has been carried out at remote sites in Japan, Oki (36oN), Happo (36oN) and Benoki (27oN). Seasonal variation at each site exhibited a clear cycle with a maximum in spring and a minimum in summer. It has been revealed that the concentrations of CO at Oki are substantially higher than at Mace Head throughout a year. Comparison of trajectory-categorized data between Oki and Mace Head has been made to elucidate that the concentration at Oki is higher than Mace Head both in the clean ''background'' and in the regionally polluted air mass. The spring maximum at Oki occurs in April that is one month later than the reported data at other remote sites in the northern hemisphere.

 

 

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

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

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


Abstract


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

 

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

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

Abstract


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

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

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

Abstract

 

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

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

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

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


Abstract


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

 

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

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

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


Abstract


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

Role of the Volatile Fraction of Submicron Marine Aerosol on its Hygroscopic Properties Role of the Volatile Fraction of Submicron Marine Aerosol on its Hygroscopic Properties

Date added: 09/12/2008
Date modified: 07/06/2009
Filesize: 257.12 kB

Sellegri, K., P. Villani, D. Picard, R. Dupuy, C. O’Dowd and P. Laj, Role of the Volatile Fraction of Submicron Marine Aerosol on its Hygroscopic Properties, Atmos. Res., in press, 2008.


Abstract


The hygroscopic growth factor (HGF) of 85 nm and 20 nm marine aerosol particles was measured during January 2006 for a three-week period within the frame of the EU FP6 project MAP (Marine Aerosol Production) winter campaign at the coastal site of Mace Head, using the TDMA technique. The results are compared to aerosol particles produced in a simulation tank by bubbling air through sea water sampled near the station, and through synthetic sea water (inorganic salts). This simulation is assimilated to primary production. Aitken and mode particles (20 nm) and accumulation mode particles (85 nm) both show HGF of 1.92 and 2.01 for particles generated through bubbling in natural and artificial sea water respectively. In the Aitken mode, the marine particles sampled in the atmosphere shows a monomodal HGF slightly lower than the one measured for sea salt particles artificially produced by bubble bursting in natural sea water (HGF = 1.83). This is also the case for the more hygroscopic mode of accumulation mode particles. In addition, the HGF of 85 nm particles observed in the atmosphere during clean marine sectors exhibits half of its population with a 1.4 HGF. An external mixture of the accumulation mode marine particles indicates a secondary source of this size of particles, a partial processing during transport, or an inhomogeneity of the sea water composition. A gentle 90 °C thermo-desorption results in a significant decrease of the number fraction of moderately hygroscopic (HGF = 1.4) particles in the accumulation mode to the benefit of the seasalt mode, pointing to the presence of semi-volatile compounds with pronounced hydrophobic properties. The thermo-desorption has no effect on the HGF of bubble generated aerosols, neither for synthetic or natural sea water, nor on the atmospheric Aitken mode, indicating that these hydrophobic compounds are secondarily integrated in the particulate phase. No difference between night and day samples is observed on the natural marine aerosols regarding hygroscopicity, but a more pronounced sensitivity to volatilization of the 1.4 HGF mode in the accumulation mode is observed during the day.

Role of organic and black carbon in the chemical composition of atmospheric aerosol at European background sites Role of organic and black carbon in the chemical composition of atmospheric aerosol at European background sites

Date added: 08/01/2001
Date modified: 07/23/2009
Filesize: 205.08 kB

Krivacsy, Z., Hoffer, A., Sarvari, Zs., Temesi, D., Baltensperger, U., Nyeki, S., Weingartner, E., Kleefeld, S., Jennings, S.G., 2001. Role of organic and black carbon in the chemical composition of atmospheric ,aerosol at European background sites. Atmospheric Environment 35, 6231-6244.


Abstract


The mass concentrations of inorganic ions, water-soluble organic carbon, water-insoluble organic carbon and black carbon were determined in atmospheric aerosol collected at three European background sites: (1) the Jungfraujoch, Switzerland (high-alpine, PM2.5 aerosol); (2) K-puszta, Hungary (rural, PM1.0 aerosol); (3) Mace Head, Ireland (marine, total particulate matter). At the Jungfraujoch and K-puszta the contribution of carbonaceous compounds to the aerosol mass was higher than that of inorganic ions by 33% and 94%, respectively. At these continental sites about 60% of the organic carbon was water soluble, 55-75% of the total carbon proved to be refractory and a considerable portion of the water soluble, refractory organic matter was composed of humic-like substances. At Mace Head the mass concentration of organic matter was found to be about twice than that of nonsea-salt ions 40% of the organic carbon was water soluble and the amount of highly refractory carbon was low. Humic-like substances were not detected but instead low molecular weight carboxylic acids were responsible for about one-fifth of the water-soluble organic mass. These results imply that the influence of carbonaceous compounds on aerosol properties (e.g. hygroscopic, optical) might be significant.

Remote Sensing of Air Pollution Remote Sensing of Air Pollution

Date added: 08/07/1979
Date modified: 07/06/2009
Filesize: 1.35 MB

O'Connor T.C,Remote Sensing of Air Pollution , Proceedings of Seminar: Airpollution- Impacts and Controls, National Board for Science and Technology, 1979, pp. 93-96


Abstract

 

Recent technological advances have enabled man to extend his remote sensing capabilities from looking at the visible world around him into other parts of the Electromagnetic spectrum and his vantage point from a tower or hill to an orbiting satellite. one can now stufy air pollution problems over widespread areas and at all levels in the atmosphere. The techniques used are reviewed briefly and their application to air pollution in the lower atmosphere considered.

Remote sensing instruments may be categorised by the region of the electromagnetic spectrum concerned; the purpose for which they are used the mode of action as passive or active; the signal recovery and data handling techniques; the platform used - ground, aircraft or satellite; and or fixed location instruments. Remote sensing techniques can be used to study aerosols and/or specific gases. They may be used to study pollution distribution in the horizontal and vertical directions, general air quality, plume tracking, source monitoring and other applications. Their advantages and disadvantages for air quality management are given.

Relative contribution of submicron and supermicron particles to aerosol light scattering...boun Relative contribution of submicron and supermicron particles to aerosol light scattering...boun

Date added: 08/06/2002
Date modified: 07/23/2009
Filesize: 399.76 kB

Kleefeld, C., C. D. O'Dowd, S. O'Reilly, S. G. Jennings, P. Aalto, E. Becker, G. Kunz, and G. de Leeuw (2002), Relative contribution of submicron and supermicron particles to aerosol light scattering in the marine boundary layer, J. Geophys. Res., 107(D19), 8103, doi:10.1029/2000JD000262.


Abstract


Measurements of the aerosol light scattering coefficient (σsp) at a wavelength of λ = 550 nm were conducted at a coastal atmospheric research station in the east Atlantic Ocean during June 1999. Size distribution measurements between diameters of 3 nm and 40 μm (at ambient humidity) were used to derive scattering coefficients from Mie theory. The calculated scattering coefficients were about a factor of 7.4 higher than the measured scattering coefficients. The discrepancy was explained by a reduced cutoff of the sampling system at particle diameters between 6 and 8 μm, dependent on wind speed. The calculated aerosol scattering was about 1 order of magnitude higher than previously reported measurements in the MBL and is attributed to supermicrometer particles at sizes d > 10 μm dominating aerosol scattering.

 

Relative contribution of submicron and supermicron particles Relative contribution of submicron and supermicron particles

Date added: 08/01/2002
Date modified: 07/23/2009
Filesize: 399.76 kB
Christoph Kleefeld, Colin O'Dowd, Sarah O'Reilly, S. Gerard Jennings, Pasi Alto, Edo, Becker, Gerard Kunz, Gerrit de Leeuw.The Relative Contribution of sub and super micron particles to aerosol light scattering in the marine boundary layer (MBL), J. Geophys. Res., 107, 10.1029/2000JD000262, 2002.

Abstract


Measurements of the aerosol light scattering coefficient (σsp) at a wavelength of λ = 550 nm were conducted at a coastal atmospheric research station in the east Atlantic Ocean during June 1999. Size distribution measurements between diameters of 3 nm and 40 μm (at ambient humidity) were used to derive scattering coefficients from Mie theory. The calculated scattering coefficients were about a factor of 7.4 higher than the measured scattering coefficients. The discrepancy was explained by a reduced cutoff of the sampling system at particle diameters between 6 and 8 μm, dependent on wind speed. The calculated aerosol scattering was about 1 order of magnitude higher than previously reported measurements in the MBL and is attributed to supermicrometer particles at sizes d > 10 μm dominating aerosol scattering.

Relationships Between Extinction, Absorption, Backscattering, and Mass Content of Sulfuric Acid Aer. Relationships Between Extinction, Absorption, Backscattering, and Mass Content of Sulfuric Acid Aer.

Date added: 07/31/1980
Date modified: 07/06/2009
Filesize: 638.52 kB

Pinnick, R.G., Jennings, S.G., and Chylek, P. (1980)- Relationship between extinction, absorption, backscattering and mass content of sulphuric acid aerosols. J. Geophys. Res., 85, 4059-4066.


Abstract


Linear relationships between aerosol extinction, absorption, backscatter, and mass content are derived for polydispersions of sulfuric acid aerosols. These relationships are independent of the form of the size distribution and are a consequence of approximating the corresponding Mie efficiency factors (the extinction efficiency Qe, the absorption efficiency Qa, and the backscatter gain G) by linear functions of the particle size parameter x. The relationships are valid only at particular wavelengths that depend on the range of particle sizes present in a particular polydispersion. For example, at a wavelength λ=0.694 μm the relation between aerosol backscatter coefficient σbs (m-1 sr-1) and mass content M(g m-3) is σbs=0.048M for 75% sulfuric acid (25% water) aerosol, under the restriction that particles in the poly-dispersion have sizes not exceeding about 1.5 μm in radius. Possible applications of the relationships are (1) inference of path-integrated mass content of sulfuric acid aerosol (for example, the clouds of Venus) from an infrared laser transmission measurement through the aerosol cloud, (2) determination of sulfuric acid aerosol mass content at a particular point in an aerosol cloud from aerosol absorption measurements at that point with a CO2(λ=10.6 μm) laser spectrophone, (3) inference of path-integrated stratospheric aerosol mass from aerosol extinction measurements made by solar occultation for wavelengths λ=0.55 and 1 μm, and (4) inference of vertical profiles of stratospheric aerosol mass from ruby lidar (λ=0.694 μm) backscatter measurements.

Relationships between condensation nuclei number concentration, tides, and standard meteorological variables at Mace Head, Ireland Relationships between condensation nuclei number concentration, tides, and standard meteorological variables at Mace Head, Ireland

Date added: 07/31/2000
Date modified: 07/23/2009
Filesize: 1.21 MB

O'Brien, E. W., Jennings, S.G., Geever, M., and Kleefeld, C. (2000). Relationships between condensation nuclei number concentration, tides, and standard meteorological variables at Mace Head, Ireland. J. Geophys. Res., 105, 1973-1986.


Abstract


The set of hourly averaged condensation nuclei (CN) data collected at Mace Head during 1991-1994 was examined for relationships that might exist between CN number concentrations and the more commonly measured meteorological variables, including tides. CN number concentrations at Mace Head can be characterized by typically low background levels (less than about 700 particles cm-3) when the wind is from the west, somewhat higher background levels (1000-4000 particles cm-3) when the wind is from the east, with sporadic bursts of short-lived discrete events of more than 10,000 cm-3 for several hours. These events occur typically during early afternoon and are normally associated with slack winds and anomalously warm, dry air. They appear to be independent of pressure, wind direction and precipitation. They can occur any time during the year, although the strongest events tend to occur during spring and autumn. Large-amplitude low tides also occur predominantly in the early afternoon during this observing period. We present evidence that large CN concentration events occur preferentially after exceptionally low tides during daylight. A neural network was employed to train the standard meteorological variables to predict CN concentrations. Baseline forecasts of CN counts for the final 180 days of the observing period were made using lagged values of all other variables. Further forecasts were made with some variables removed from the predictor set. The best correlation between the predicted values and the verifying data over the 180 days was 0.67, which was obtained from a 1-hour forecast using knowledge of all variables except temperature. Other variables whose removal improved the forecast (or whose presence degraded it) were pressure and wind speed. The best predictors of CN values were wind direction, relative humidity, and time of day. An elementary nearest neighbor, or historical analogue approach to predicting the same set of CN values generated lower correlations with the verifying data but generated a much more accurate probability distribution function.

Relationship between visible extinction absorption and mass concentration of carbonaceous smokes Relationship between visible extinction absorption and mass concentration of carbonaceous smokes

Date added: 07/31/1980
Date modified: 07/06/2009
Filesize: 1.99 MB

Jennings, S.G., and Pinnick, R.G. (1980)- Relationships between visible extinction, absorption and mass concentration of carbonaceous smokes. Atmos. Environ., 14, 1123-1129.


Abstract


A linear relation, independent of the size distribution, between visible and near-i.r. extinction coefficient σe(m−1) and mass concentration M (gm−3) of carbonaceous smokes is predicted. For a wavelength λ = 0.55μm the relation is σe/M = 9.5m2g−1, assuming a particle density of 2gcm−3. The relation is in good agreement with measurements on coal-fired stack plumes, oil smoke, soot and diesel exhaust that are available in the literature. A similar relationship between carbonaceous smoke visible and near-i.r. absorption coefficient σa, and mass concentration is also derived. The relations suggest that integrated mass concentration along a path within a carbonaceous smoke cloud can be inferred from measurement of the transmission from one end of the path to the other, and that the mass concentration at a particular location in the cloud can be determined from an in situ measurement of aerosol absorption at that location with a visible or near-i.r. laser spectrophone.

Relationship between visible extinction absorption and mass concentration of carbonaceous smokes Relationship between visible extinction absorption and mass concentration of carbonaceous smokes

Date added: 07/31/1980
Date modified: 07/22/2009
Filesize: 1.99 MB

Jennings, S.G., and Pinnick, R.G. (1980)- Relationships between visible extinction, absorption and mass concentration of carbonaceous smokes. Atmos. Environ., 14, 1123-1129.


Abstract


A linear relation, independent of the size distribution, between visible and near-i.r. extinction coefficient σe(m−1) and mass concentration M (gm−3) of carbonaceous smokes is predicted. For a wavelength λ = 0.55μm the relation is σe/M = 9.5m2g−1, assuming a particle density of 2gcm−3. The relation is in good agreement with measurements on coal-fired stack plumes, oil smoke, soot and diesel exhaust that are available in the literature. A similar relationship between carbonaceous smoke visible and near-i.r. absorption coefficient σa, and mass concentration is also derived. The relations suggest that integrated mass concentration along a path within a carbonaceous smoke cloud can be inferred from measurement of the transmission from one end of the path to the other, and that the mass concentration at a particular location in the cloud can be determined from an in situ measurement of aerosol absorption at that location with a visible or near-i.r. laser spectrophone.

Relation between absorption coefficient and imaginary index of atmospheric aerosol constituents Relation between absorption coefficient and imaginary index of atmospheric aerosol constituents

Date added: 07/31/1979
Date modified: 07/06/2009
Filesize: 512.02 kB
Jennings, S.G., Pinnick, R.G., and Gillespie, J.B. (1979)- Relation between absorption coefficient and imaginary index of atmospheric aerosol constituents. Appl. Opt., 18, 1368-1371.

Abstract


The absorption coefficient per unit mass α(cm2g-l) for aerosols in the wavelength range λ = 1.06–10.6 µm is shown to be a sensitive function of particle size distribution and of both imaginary and real indexes of refraction. Hence the imaginary index of refraction cannot be accurately determined from absorption measurements on an aerosol sample as attempted by S. A. Schleusener et al., Appl. Opt. 15, 2546 (1976), unless the size distribution and real index of the aerosol material are known. Similar difficulties arise in attempts to infer imaginary index from transmission measurements through aerosol samples as done by F. E. Volz, Appl. Opt. 11, 755 (1972); 12, 564 (1973) and K. Fischer, Beitr. Phys. Atmos. 43, 244 (1970). In addition, scattering losses can further complicate the determination of imaginary index from transmission measurements.

Regional-scale Ozone Deposition to North-East Atlantic Waters Regional-scale Ozone Deposition to North-East Atlantic Waters

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 4.87 MB

Coleman, L., S. Varghese, O.P. Tripathi, S G. Jennings, C.D. O’Dowd, Regional-scale Ozone Deposition to North-East Atlantic Waters, Adv. in Meteorol., Volume 2010, Article ID 243701, doi:10.1155/2010/243701 2010.


A regional climate model is used to evaluate dry deposition of ozone over the North East Atlantic. Results are presented for a deposition scheme accounting for turbulent and chemical enhancement of oceanic ozone deposition and a second non-chemical, parameterised gaseous dry deposition scheme. The first deposition scheme was constrained to account for sea-surface ozone-iodide reactions and the sensitivity of modelled ozone concentrations to oceanic iodide concentration was investigated. Simulations were also performed using nominal reaction rate derived from i

n-situ ozone deposition measurements and using a preliminary representation of organic chemistry. Results show insensitivity of ambient ozone concentrations modelled by the chemicalenhanced scheme to oceanic iodide concentrations, and iodide reactions alone cannot account for observed deposition velocities. Consequently, we suggest a missing chemical sink due to reactions of ozone with organic matter at the air-sea interface. Ozone loss rates are estimated to be in the range of 0.5–6 ppb per day. A potentially significant ozone-driven flux of iodine to the atmosphere is estimated to be in the range of 2.5–500Mmolec cm2 s1, leading to amixing-layer enhancement of organo-iodine concentrations of 0.1–22.0 ppt, with an average increase in the N.E. Atlantic of around 4 ppt per day.

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

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

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


Abstract


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

 

Regional model simulation of North Atlantic cyclones Present climate and idealized response to incre Regional model simulation of North Atlantic cyclones Present climate and idealized response to incre

Date added: 08/01/2008
Date modified: 07/23/2009
Filesize: 2.79 MB
Semmler, T., S. Varghese, R. McGrath, P. Nolan, S. Wang, P. Lynch, and C. O'Dowd, Regional model simulation of North Atlantic cyclones: Present climate and idealized response to increased sea surface temperature, J. Geophys. Res., 113, D02107, doi:10.1029/2006JD008213, 2008.

Abstract

 

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

Regional climate simulations of North Atlantic cyclones: changes .. in a climate change scenario Regional climate simulations of North Atlantic cyclones: changes .. in a climate change scenario

Date added: 08/06/2008
Date modified: 07/23/2009
Filesize: 4.19 MB

Semmler, S. Varghese, R. McGrath, P. Nolan, S. Wang, P. Lynch, C. O'Dowd, Regional climate simulations of North Atlantic cyclones: changes in frequency and intensity in a climate change scenario, Climate Res. Vol. 36: 1–16, 2008, doi: 10.3354/cr00732,  2008


Abstract

 

Frequency and intensity of cyclones over the North Atlantic are investigated using 2 data sets from simulations with the Rossby Centre regional climate model RCA3. The model domain comprises large parts of the North Atlantic and the adjacent continents. RCA3 is driven by ECHAM5- OM1 general circulation model data for May to December from 1985 to 2000 and May to December from 2085 to 2100 assuming the SRES-A2 emission scenario. We apply an objective algorithm to identify and track tropical and extratropical cyclones, as well as extratropical transition. The simulation
indicates increase in the count of strong hurricanes and extratropical cyclones. Contrasting, and generally weaker, changes are seen for the less extreme events. Decreases of 18% in the count of extratropical cyclones and 13% in the count of tropical cyclones with wind speeds of ≥18 m s–1 can be found. Furthermore, there is a pronounced shift in the tracks of hurricanes and their extratropical transition in November and December—more hurricanes are seen over the Gulf of Mexico, the Caribbean Sea and the western Sargasso Sea and less over the southern North Atlantic.

Regional climate model simulations of North Atlantic cyclones frequency and intensity changes Regional climate model simulations of North Atlantic cyclones frequency and intensity changes

Date added: 08/01/2008
Date modified: 07/23/2009
Filesize: 4.19 MB
Semmler, T., S. Varghese, R. McGrath, P. Nolan, S. Wang, P. Lynch, and C. O'Dowd (2008) 'Regional climate model simulations of North Atlantic cyclones: frequency and intensity changes'. Climate Research, 36 :1-16.

Abstract


Frequency and intensity of cyclones over the North Atlantic are investigated using 2 data sets from simulations with the Rossby Centre regional climate model RCA3. The model domain comprises large parts of the North Atlantic and the adjacent continents. RCA3 is driven by ECHAM5- OM1 general circulation model data for May to December from 1985 to 2000 and May to December from 2085 to 2100 assuming the SRES-A2 emission scenario. We apply an objective algorithm to identify and track tropical and extratropical cyclones, as well as extratropical transition. The simulation indicates increase in the count of strong hurricanes and extratropical cyclones. Contrasting, and generally weaker, changes are seen for the less extreme events. Decreases of 18% in the count of extratropical cyclones and 13% in the count of tropical cyclones with wind speeds of ≥18 m s–1 can be found. Furthermore, there is a pronounced shift in the tracks of hurricanes and their extratropical transition in November and December—more hurricanes are seen over the Gulf of Mexico, the Caribbean Sea and the western Sargasso Sea and less over the southern North Atlantic.

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

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

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


Abstract


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

 

Rapid growth of hydrofluorocarbon 134a and hydrochlorofluorocarbons 141b, 142b, and 22 from Adv Rapid growth of hydrofluorocarbon 134a and hydrochlorofluorocarbons 141b, 142b, and 22 from Adv

Date added: 08/06/2004
Date modified: 07/23/2009
Filesize: 791.05 kB

O'Doherty, S., et al. (2004), Rapid growth of hydrofluorocarbon 134a and hydrochlorofluorocarbons 141b, 142b, and 22 from Advanced Global Atmospheric Gases Experiment (AGAGE) observations at Cape Grim, Tasmania, and Mace Head, Ireland, J. Geophys. Res., 109, D06310, doi:10.1029/2003JD004277.


Abstract


An update of in situ Advanced Global Atmospheric Gases Experiment (AGAGE) hydrofluorocarbon (HFC)/hydrochlorofluorocarbon (HCFC) measurements made at Mace Head, Ireland, and Cape Grim, Tasmania, from 1998 to 2002 are reported. HCFC-142b, HCFC-141b, HCFC-22 and HFC-134a show continued rapid growth in the atmosphere at mean rates of 1.1, 1.6, 6.0, and 3.4 ppt/year, respectively. Emissions inferred from measurements are compared to recent estimates from consumption data. Minor updates to the industry estimates of emissions are reported together with a discussion of how to best determine OH concentrations from these trace gas measurements. In addition, AGAGE measurements and derived emissions are compared to those deduced from NOAA-Climate Monitoring and Diagnostics Laboratory flask measurements (which are mostly made at different locations). European emission estimates obtained from Mace Head pollution events using the Nuclear Accident Model (NAME) dispersion model and the best fit algorithm (known as simulated annealing) are presented as 3-year rolling average emissions over Europe for the period 1999–2001. Finally, the measurements of HCFC-141b, HCFC-142b, and HCFC-22 discussed in this paper have been combined with the Atmospheric Lifetime Experiment (ALE)/Global Atmospheric Gases Experiment (GAGE)/AGAGE measurements of CFC-11, CFC-12, CFC-113, CCl4, and CH3CCl3 to produce the evolution of tropospheric chlorine loading.

 

Raindrop interactions and rainfall rates within clouds Raindrop interactions and rainfall rates within clouds

Date added: 11/30/1972
Date modified: 07/06/2009
Filesize: 787.75 kB

Brazier-Smith, P.R., Jennings, S.G., and Latham, J. (1973)- Raindrop interactions and rainfall rates within clouds. Quart. J. Roy. Met. Soc., 99, 260-272.


Abstract

 

Experiments showed that when a pair of water drops of raindrop dimensions collide and separate in air at their relative terminal velocities satellite drops are generally produced. Although the numbers and sizes of satellites resulting from individual interactions are highly variable a typical event produces about 3 satellites each having a volume of 0.04 ViVj/(Vi + Vj), where Vi and Vj are the volumes of the parent drops.

A full stochastic treatment is presented of the development of rainfall in a volume within a cloud where water is being released by condensation at a constant rate J. The production of satellites and an experimentally verified expression for the coalescence efficiency are incorporated into these calculations. Computations are made of the variation with time of the cloud water content, C, the rainwater content, L, the radar reflectivity, Z, the rainfall rate, P, and the drop-size distribution. The calculations show that the crucial parameter in governing the intensity and duration of rainfall is J, and that the microphysical processes are of secondary importance; C, L and P are all insensitive to and the production of satellite drops. The influence upon rainfall development of the break-up of large raindrops on attaining their maximum size within a cloud is found to be even less than that of the satellites.

The drop size distribution after several minutes of growth is insensitive to the initial spectrum but is markedly dependent upon and the production of satellites, which tend eventually to produce a bimodal spectrum. The radar reflectivity increases very rapidly with time (typically by about an order of magnitude every 2 1/2 minutes) and depends quite strongly on , but is unaffected by the production of satellites.


 

Quasi-Lagrangian investigation into dimethyl sulfide oxidation in maritime air using a combinat Quasi-Lagrangian investigation into dimethyl sulfide oxidation in maritime air using a combinat

Date added: 08/06/2000
Date modified: 07/23/2009
Filesize: 1.6 MB

James, J. D. ; Harrison, Roy M. ; Savage, N. H. ; Allen, A. G. ; Grenfell, J. L. ; Allan, B. J. ; Plane, J. M. C. ; Hewitt, C. N. ; Davison, B. ; Robertson, L.  2000, Quasi-Lagrangian investigation into dimethyl sulfide oxidation in maritime air using a combination of measurements and model, J. Geophys. Res. Vol. 105 , No. D21 , p. 26,379 (2000JD900375)


Abstract


Using a combination of field measurement data and a modified photochemical box model, strong evidence is presented to suggest that the rate of daytime oxidation of dimethyl sulfide (DMS) by OH radicals is insufficient to describe the measured conversion. Quasi-Lagrangian measurements were made at two sites in the eastern Atlantic (Research Vessel and Mace Head Research Station, Ireland) as part of the Atmospheric Chemistry Studies in the Oceanic Environment (ACSOE) program. Periods of connected flow between the two sites were identified, air parcel transit times were estimated, and measurements of the main DMS oxidation products (MSA, SO2, and nss-SO42-) were compared with model predictions to establish whether the model's chemical mechanism could account for observed changes. The main finding was that during daytime periods with maritime air masses, the model failed to predict a sufficient increase in DMS oxidation products during the estimated transit time. This was despite a tendency to overprediction of the progress of nitrogen chemistry during air mass advection, and independent checks on the model estimates of hydroxyl radical concentrations through measurements. In the light of this, the involvement of halogen species (most probably halogen oxides) or heterogeneous oxidation processes is tentatively suggested as the cause of enhanced daytime DMS oxidation in the marine boundary layer (MBL). Increasing the rate constant for the OH + DMS reaction by a factor of 3.3 (as a crude way of simulating parallel channels of DMS oxidation) permitted model results to reproduce the measurements very much more closely.

 

Quantification of the carbonaceous matter origin in submicron marine aerosol particles by dual carbo Quantification of the carbonaceous matter origin in submicron marine aerosol particles by dual carbo

Date added: 08/25/2011
Date modified: 08/25/2011
Filesize: 5.12 MB

Ceburnis, A. Garbaras, S. Szidat, M. Rinaldi, S. Fahrni, N. Perron, L. Wacker, S. Leinert, V. Remeikis, M. C. Facchini, A. S. H. Prevot, S. G. Jennings, and C. D. O'Dowd. Quantification of the carbonaceous matter origin in submicron marine aerosol particles by dual carbon isotope analysis,  Atmos. Chem. Phys., 11, 8593–8606, 2011, doi:10.5194/acp-11-8593-2011



Abstract.

 

Dual carbon isotope analysis of marine aeroso samples has been performed for the first time demonstrating a potential in organic matter apportionment  etween three principal sources: marine, terrestrial (non-fossil) and fossil fuel due to unique isotopic signatures. The results presented here, utilising combinations of dual carbon isotope analysis, provides conclusive evidence of a dominant biogenic organic fraction to organic aerosol over biologically active oceans. In particular, the NE Atlantic, which is also subjected to notable anthropogenic influences via pollution transport processes, was found to contain 80% organic aerosol matter of biogenic origin directly linked to plankton emissions. The remaining carbonaceous aerosol was of terrestrial origin. By contrast, for polluted air advected out from Europe into the NE Atlantic, the source apportionment is 30% marine biogenic, 40% fossil fuel, and 30% continental non-fossil fuel. The dominant marine organic aerosol source in the atmosphere has significant implications for climate change feedback processes.

 

Quantification of Coastal New Ultra-Fine Particles Formation from In situ and Chamber Measurements during the BIOFLUX Campaign Quantification of Coastal New Ultra-Fine Particles Formation from In situ and Chamber Measurements during the BIOFLUX Campaign

Date added: 08/01/2005
Date modified: 07/23/2009
Filesize: 1014.54 kB

Sellegri, K., Y. J. Yoon, S. G. Jennings, C. D. O’Dowd, L. Pirjola, S. Cautenet, H. Chen, T. Hoffmann, Quantification of Coastal New Ultra-Fine Particles Formation from In situ and Chamber Measurements during the BIOFLUX Campaign. Environ. Chem. 2, 260. doi:10.1071/EN05074, 2005.


Abstract


Secondary processes leading to the production of ultra-fine particles by nucleation are still poorly understood. A fraction of new particles formed can grow into radiatively active sizes, where they can directly scatter incoming  solar radiation and, if partly water soluble, contribute to the cloud condensation nuclei population. New particle formation events have been frequently observed at the Mace Head Atmospheric Research Station (western Ireland), under low tide and sunny conditions, leading to the hypothesis that new particles are formed from iodo-species emitted from macroalgae.

Quantification of carbon dioxide, methane, nitrous oxide and chloroform emissions over Ireland from atmospheric observations at Mace Head Quantification of carbon dioxide, methane, nitrous oxide and chloroform emissions over Ireland from atmospheric observations at Mace Head

Date added: 08/01/2002
Date modified: 07/23/2009
Filesize: 738.69 kB

Biraud, S., Ciais, Philippe, Ramonet, Michel, Simmonds, Peter, Kazan, Victor, Monfray, Patrick, O’Doherty, Simon, Spain, Gerard, and Jennings, S. Gerard. 2002. Quantification of carbon dioxide, methane, nitrous oxide, and chloroform emissions over Ireland from atmospheric observations at Mace Head, Tellus, 54B, pp. 41-60.


Abstract


Flux estimates of CO2, CH4, N2O and CHCl3 over Ireland are inferred from continuous atmospheric records of these species. We use radon-222 (222Rn) as a reference compound to estimate unknown sources of other species. The correlation between each species and 222Rn is calculated for a suite of diurnal events that have been selected in the Mace Head record over the period 1995-1997 to represent air masses exposed to sources over Ireland. We established data selection criteria based on 222Rn and 212Pb concentrations. We estimated flux densities of 12 × 103 kg CH4 km-2 yr-1, 680 kg N2O km-2 yr-1 and 20 kg CHCl3 km-2 yr-1 for CH4, N2O and CHCl3, respectively. We also inferred flux densities of 250 x 103 kg C km-2 yr-1 for CO2 during wintertime, and of 760 x 103 kg C km-2 yr-1 for CO2 during summer night-time. Our CH4 inferred flux compare well with the CORINAIR90 and CORNAIR94 inventories for Ireland. The N2O emission flux we inferred is close to the inventory value by CORINAIR90, but twice the inventory value by CORINAIR94 and EDGAR 2.0. This discrepancy may have been caused by the use of the revised 1996 IPCC guidelines for national greenhouse gas inventories in 1994, which include a new methodology for N2O emissions from agriculture. We carried out the first estimation of CHCl3 emission fluxes over Ireland. This estimation is 4 times larger than the CHCl3 emission fluxes measured close to the Mace Head station over peatlands. Our CHCl3 emission fluxes estimate is consistent with the interpretation of the same data by Ryall (personal communication, 2000), who obtained, using a Lagrangian atmospheric transport model, CHCl3 fluxes of 24 ± 7 kg CHCl3 km-2 yr-1. Our estimates of CO2 emission fluxes during summer night-time and wintertime are close to those estimated from inventories and to one biogeochemical model of heterotrophic respiration.

Production of peroxy radicals at night via reactions of ozone and the nitrate radical in the ma Production of peroxy radicals at night via reactions of ozone and the nitrate radical in the ma

Date added: 08/06/2001
Date modified: 07/23/2009
Filesize: 1.44 MB

Salisbury, G., et al. (2001), Production of peroxy radicals at night via reactions of ozone and the nitrate radical in the marine boundary layer, J. Geophys. Res., 106(D12), 12,669–12,687.


Abstract


In this paper, a substantial set of simultaneous measurements of the sum of peroxy radicals, [HO2+RO2], NO3, hydrocarbons (HCs), and ozone, taken at Mace Head on the Atlantic coast of Ireland in spring 1997, is presented. Conditions encountered during the experiment ranged from semipolluted air masses advected from Britain and continental Europe to clean air masses off the North and mid-Atlantic, where mixing ratios of pollution tracers approached Northern Hemispheric background mixing ratios. Average mixing ratios of peroxy radicals varied from 2.5 to 5.5 parts per trillion by volume (pptv) at night depending on wind sector, and were observed to decay only very slowly from late afternoon to early morning (0.1–0.5 pptv h−1). Measurements of OH and HO2 on two nights using the Fluorescence Assay by Gas Expansion (FAGE) technique give an upper limit for [OH] of 2.5×105 molecules cm−3 and an average upper limit [HO2]/[HO2+RO2] ratio of 0.27. A modeling study of the 1/e lifetimes of the peroxy radicals, assuming no radical production at night, yielded mean lifetimes of between ∼ 8–23 min for HO2 and 3–18 min for CH3O2. Given these lifetimes, it may be concluded that the peroxy-radical mixing ratios observed could not be maintained without substantial production at night. No significant correlation is observed between measured [HO2+RO2] and [NO3] under any conditions. Calculation of the reaction rates for ozone and NO3 with hydrocarbons (HCs) shows that the ozone-initiated oxidation routes of HCs outweighed those of NO3 in the NE, SE and NW wind sectors. In the SW sector, however, the two mechanisms operated at similar rates on average, and oxidation by NO3 was the dominant route in the westerly sector. The oxidation of alkenes at night by ozone was greater by a factor of 4 than that by NO3 over the whole data set. The HC degradation rates from the three “westerly” sectors, where tracer mixing ratios were relatively low, may be representative of the nighttime oxidative capacity of the marine boundary layer throughout the background Northern Hemisphere. Further calculations using literature values for OH yields and inferred RO2 yields from the ozone-alkene reactions show that peroxy radicals derived from the ozone reactions were likely to make up the major part of the peroxy-radical signal at night (mean value 66%). However, the NO3 source was of similar magnitude in the middle of the night, when [NO3] was generally at its maximum. The estimated total rates of formation of peroxy radicals are much higher under semipolluted conditions (mean 8.0×104 molecules cm−3 s−1 in the SE wind sector) than under cleaner conditions (mean 2.4×104 molecules cm−3 s−1 in the westerly wind sector). A model study using a campaign-tailored box model (CTBM) for semipolluted conditions shows that the major primary sources of OH, HO2, and CH3O2 (the most abundant organic peroxy radical) were the Criegee biradical intermediates formed in the reactions of ozone with alkenes.

 

PRODUCTION OF METHANOL, ACETONE AND. ACETALDEHYDE DURING LONG-RANGE. TRANSPORT PRODUCTION OF METHANOL, ACETONE AND. ACETALDEHYDE DURING LONG-RANGE. TRANSPORT

Date added: 08/07/2003
Date modified: 08/07/2008
Filesize: 32.63 kB
Stanton, J.C.; Pilling, M.J.; Hopkins, J.R.; Lewis, A.C.Production of methanol, acetone and acetaldehyde during long-range transport [EGU04-A-07457].

Production Of Cn by Gaseous Reactions Production Of Cn by Gaseous Reactions

Date added: 08/07/1963
Date modified: 07/23/2009
Filesize: 4.02 MB
Tom OConnor ,Production Of Cn by Gaseous Reactions, Journal de Recherches Atmospherique, pg 127 - 133 (1963)
Abstract

 

The production of condensation Nuclei as a result of gaseous reactions is discussed.  A Portable nucleus counter used to investigate sources of nuclei in the littoral zone is described. Laboratory experiments show that decaying seaweed emits a gas which forms condensation nuclei on irradiation with ultra violet or sunlight. It also emits H2S and the significance of this in the natural cycle of sulphur in the atmosphere is considered. Electrically heated wires produce very small condensation nuclei and also NO2.

Production Flux of Sea-Spray Aerosol. Rev. of Geophys., Production Flux of Sea-Spray Aerosol. Rev. of Geophys.,

Date added: 05/12/2011
Date modified: 05/12/2011
Filesize: 2.68 MB

de Leeuw, G., E. Andreas, M. Anguelova , C. Fairall , E. Lewis , C. O'Dowd , M. Schulz , S. Schwartz , Production Flux of Sea-Spray Aerosol. Rev. of Geophys., doi:10.1029/2010RG000349, 2011


 

Knowledge of the sizeand compositiondependent production flux of primary sea spray aerosol (SSA) particles and its dependence on environmental variables is required for modeling cloud microphysical properties and aerosol radiative influences, interpreting measurements of particulate matter in coastal areas and its relation to air quality, and evaluating rates of uptake and reactions of gases in sea spray drops. This review examines recent research pertinent to SSA production flux, which deals mainly with production of particles with r80 (equilibrium radius at 80% relative humidity) less than 1 mm and as small as 0.01 mm. Production of sea spray particles and its dependence on controlling factors has been investigated in aboratory studies that have examined the dependences on water temperature, salinity, and the presence of organics and in field measurements with micrometeorological techniques that use newly developed fast optical particle sizers. Extensive measurements show that waterinsoluble organic matter contributes substantially to the omposition of SSA particles with r80 < 0.25 mm and, in locations with high biological activity, can be the ominant constituent. Orderofmagnitude variation  remains in estimates of the sizedependent production flux per white area, the quantity central to formulations of the production flux based on the whitecap method. This variation indicates that the production flux may depend on quantities such as the volume flux of air bubbles to the surfacet hat are not accounted for in current models. Variation in estimates of the whitecap fraction as a function of wind speed contributes additional, comparable uncertainty to production flux estimates.  

Proceedings of the Royal Irish Academy The Calibration of a photo-electric nucleus counter. Proceedings of the Royal Irish Academy The Calibration of a photo-electric nucleus counter.

Date added: 08/31/1946
Date modified: 07/22/2009
Filesize: 4.32 MB
P.J Nolan, L.W. Pollack, Proceedings of the Royal Irish Academy The Calibration of a photo-electric nucleus counter., Volume L1, Section A, No. 2, 1946

Abstract

 

Models of nucleus counterm designed to measure photo-electrically the decrease in intensity of a beam of light which has passed one or more times through an artificially produced fog, are described by L.W. Pollak and W.A. Morgan in a paper.

Primary versus secondary contributions to particle number concentrations in the European boundary layer Primary versus secondary contributions to particle number concentrations in the European boundary layer

Date added: 03/12/2013
Date modified: 03/12/2013
Filesize: 2.77 MB

C.L. Reddington, K.S. Carslaw, D.V. Spracklen, M.G. Frontoso, L.Collins, J. Merikanto, A. Minikin, T. Hamburger, H.Coe, M. Kulmala, P. Aalto, H. Flentje, C. Plass-Dülmer, W. Birmili, A. Wiedensohler, B. Wehner, T. Tuch, A.Sonntag, C. D. O'Dowd, S.G. Jennings, R.Dupuy, U. Baltensperger, E. Weingartner, H.-C. Hansson, P. Tunved, P. Laj, K. Sellegri, J. Boulon, J.-P. Putaud, C. Gruening, E. Swietlicki, P. Roldin, J. S. Henzing, M. Moerman, N. Mihalopoulos, G. Kouvarakis, V. Ždímal, N. Zíková, A. Marinoni, P. Bonasoni, and R. Duchi,Primary versus secondary contributions to particle number concentrations in the European boundary layer, Atmos. Chem. Phys., 11, 12007-12036, 2011, www.atmos-chem-phys.net/11/12007/2011/ doi:10.5194/acp-11-12007-2011


 

 

 

Abstract. It is important to understand the relative contribution of primary and secondary particles to regional and global aerosol so that models can attribute aerosol radiative forcing to different sources. In large-scale models, there is considerable uncertainty associated with treatments of particle formation (nucleation) in the boundary layer (BL) and in the size distribution of emitted primary particles, leading to uncertainties in predicted cloud condensation nuclei (CCN) concentrations. Here we quantify how primary particle emissions and secondary particle formation influence size-resolved particle number concentrations in the BL using a global aerosol microphysics model and aircraft and ground site observations made during the May 2008 campaign of the European Integrated Project on Aerosol Cloud Climate Air Quality Interactions (EUCAARI). We tested four different parameterisations for BL nucleation and two assumptions for the emission size distribution of anthropogenic and wildfire carbonaceous particles. When we emit carbonaceous particles at small sizes (as recommended by the Aerosol Intercomparison project, AEROCOM), the spatial distributions of campaign-mean number concentrations of particles with diameter >50 nm (N50) and >100 nm (N100) were well captured by the model (R2 >0.8) and the normalised mean bias (NMB) was also small (18% for N50 and 1% for N100). Emission of carbonaceous particles at larger sizes, which we consider to be more realistic for low spatial resolution global models, results in equally good correlation but larger bias R2 >0.8, NMB =52% and 29 %), which could be partly but not entirely compensated by BL nucleation. Within the uncertainty of the observations and accounting for the uncertainty in the size of emitted primary particles, BL nucleation makes a statistically significant contribution to CCN-sized particles at less than a quarter of the ground sites. Our results show that a major source of uncertainty in CCN-sized particles in polluted European air is the emitted size of primary carbonaceous particles. New information is required not just from direct observations, but also to determine the “effective emission size” and composition of primary particles appropriate for different resolution models.

 

Primary submicron marine aerosol dominated by insoluble organic colloids and aggregates Primary submicron marine aerosol dominated by insoluble organic colloids and aggregates

Date added: 04/08/2009
Date modified: 11/01/2009
Filesize: 220.61 kB
Facchini, M.C.,  M. Rinaldi, S. Decesari, C. Carbone, E. Finessi, M. Mircea, S. Fuzzi, D. Ceburnis, R.  Flanagan, E. D. Nillsson, G.  de Leeuw, M. Martino,  J. Woeltjen and C.D. O’ Dowd, Primary submicron marine aerosol dominated by insoluble organic colloids and aggregates,, Geophys. Res. Letts., doi:10.1029/2008GL034210, 2008.

Abstract

 

The chemical properties of sea-spray aerosol particles produced by artificially generated bubbles using oceanic waters were investigated during a phytoplankton bloom in the North Atlantic. Spray particles exhibited a progressive increase in the organic matter (OM) content from 3 ± 0.4% up to 77 ± 5% with decreasing particle diameter from 8 to 0.125 mm. Submicron OM was almost entirely water insoluble (WIOM) and consisted of colloids and aggregates exuded by phytoplankton. Our observations indicate that size dependent transfer of sea water organic material to primary marine particles is mainly controlled by the solubility and surface tension properties of marine OM. The pattern of WIOM and sea-salt content in the different size intervals observed in bubble bursting experiments is similar to that measured in atmospheric marine aerosol samples collected during periods of high biological activity. The results point to a WIOM/sea-salt fingerprint associated with submicron primary marine aerosol production in biologically rich waters.

Primary Marine Organic Aerosol: A Dichotomy of Low Hygroscopicity and High CCN Activity Primary Marine Organic Aerosol: A Dichotomy of Low Hygroscopicity and High CCN Activity

Date added: 11/17/2011
Date modified: 11/17/2011
Filesize: 532.27 kB

Ovadnevaite, J., D. Ceburnis, J. Bialek, C. Monahan, G. Martucci, M. Rinaldi, M.C. Facchini, H. Berresheim, D. R. Worsnop and C. O’Dowd. Primary Marine Organic Aerosol: A Dichotomy of Low Hygroscopicity and High CCN Activity, Geophys. Res. Letts, 38, L21806, doi:10.1029/2011GL048869., 2011


Abstract. High-time resolution measurements of primary marine organic sea-spray physico-chemical properties reveal an apparent dichotomous behavior in terms of water uptake: specifically sea-spray aerosol enriched in organic matter possesses a low hydroscopic Growth Factor (GF~1.25) while simultaneously having a cloud condensation nucleus/condensation nuclei (CCN/CN) activation efficiency of between 83% at 0.25% supersaturation and 100% at 0.75%. In contrast, the activation efficiency of particles dominated by non-sea-salt (nss)-sulfate ranged between 48-100% over supersaturation range of 0.25%-1%. Simultaneous retrieval of Cloud Droplet Number Concentration (CDNC) during primary organic aerosol plumes reveals CDNC concentrations of 350 cm-3 for organic mass concentrations 3-4 mg m-3. It is demonstrated that the retrieved high CDNCs under clean marine conditions can only be explained by organic sea-spray and corroborates the high CCN activation efficiency associated with primary organics. It is postulated that marine hydrogels are responsible for this dichotomous behavior.

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

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

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


Abstract


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

Primary and secondary organic marine aerosol and oceanic biological activity: recent results and new Primary and secondary organic marine aerosol and oceanic biological activity: recent results and new

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 672.69 kB

Rinaldi,M., S.Decesari, E. Finessi, L.Giulianelli, C.Carbone, S.Fuzzi, C.D. O'Dowd, D.Ceburnis and M.C. Facchini, Primary and secondary organic marine aerosol and oceanic biological activity: recent results and new perspectives for future studies, Adv. in Meteorol., Volume 2010, Article ID 310682, doi:10.1155/2010/243701, 2010.

 


 

One of the most important natural aerosol systems at the global level is marine aerosol that comprises both organic and inorganic components of primary and secondary origin. The present paper reviews some new results on primary and secondary organic marine aerosol, achieved during the EU project MAP (Marine Aerosol Production), comparing them with those reported in the recent literature.Marine aerosol samples collected at the coastal site ofMaceHead, Ireland, show a chemical composition trend that is influenced by the oceanic biological activity cycle, in agreement with other observations. Laboratory experiments show that seaspray  aerosol from biologically active sea water can be highly enriched in organics, and the authors highlight the need for further studies on the atmospheric fate of such primary organics. With regard to the secondary fraction of organic aerosol, the average  chemical composition and molecular tracer (methanesulfonic-acid, amines) distribution could be successfully characterized by adopting a multitechnique analytical approach.

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

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

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


Abstract.

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

 

Potential for photochemical ozone formation in the troposphere over the North Atlantic as deriv Potential for photochemical ozone formation in the troposphere over the North Atlantic as deriv

Date added: 08/06/2002
Date modified: 07/23/2009
Filesize: 1.34 MB

Reeves, C. E., et al. (2002), Potential for photochemical ozone formation in the troposphere over the North Atlantic as derived from aircraft observations during ACSOE, J. Geophys. Res., 107(D23), 4707, doi:10.1029/2002JD002415.


Abstract


In this paper, ozone (O3), water vapor (H2O), carbon monoxide (CO), and peroxide concentrations and photolysis rates measured in the troposphere over the North Atlantic during two Atmospheric Chemistry Studies in the Oceanic Environment (ACSOE) aircraft field campaigns are used to calculate the concentration of nitric oxide (NO) required for net photochemical O3 production (nPO3) to be positive (NOcomp). NOcomp tended to show a decrease with altitude, although it was sometimes found to be low in the marine boundary layer (MBL) where H2O concentrations were high and O3 concentrations were low. nPO3 was calculated for the spring when NO data were available and was found to be mostly negative and generally increased from about −0.5 to −0.2 ppbv hr−1 in the MBL to +0.04 ppbv hr−1 at about 7–8 km altitude. The results suggest that much of the lower and middle troposphere over the eastern North Atlantic during spring is in a state of slow net photochemical O3 destruction. However, in the upper troposphere, the system changes to one of net photochemical production, which results from the drier environment and higher NO concentrations. Furthermore, examples of net O3 production were also observed in the lower and middle troposphere associated with either in situ sources of NO or long-range transport of pollution. The paper also illustrates the sensitivity of this O3 production/loss state to H2O and NO concentrations, photolysis rates, and temperatures.

 

Potential for photochemical ozone formation in the troposphere over the North Atlantic as deriv Potential for photochemical ozone formation in the troposphere over the North Atlantic as deriv

Date added: 08/06/2002
Date modified: 09/11/2009
Filesize: 1.34 MB

Reeves, C. E., et al. (2002), Potential for photochemical ozone formation in the troposphere over the North Atlantic as derived from aircraft observations during ACSOE, J. Geophys. Res., 107(D23), 4707, doi:10.1029/2002JD002415.


Abstract


In this paper, ozone (O3), water vapor (H2O), carbon monoxide (CO), and peroxide concentrations and photolysis rates measured in the troposphere over the North Atlantic during two Atmospheric Chemistry Studies in the Oceanic Environment (ACSOE) aircraft field campaigns are used to calculate the concentration of nitric oxide (NO) required for net photochemical O3 production (nPO3) to be positive (NOcomp). NOcomp tended to show a decrease with altitude, although it was sometimes found to be low in the marine boundary layer (MBL) where H2O concentrations were high and O3 concentrations were low. nPO3 was calculated for the spring when NO data were available and was found to be mostly negative and generally increased from about −0.5 to −0.2 ppbv hr−1 in the MBL to +0.04 ppbv hr−1 at about 7–8 km altitude. The results suggest that much of the lower and middle troposphere over the eastern North Atlantic during spring is in a state of slow net photochemical O3 destruction. However, in the upper troposphere, the system changes to one of net photochemical production, which results from the drier environment and higher NO concentrations. Furthermore, examples of net O3 production were also observed in the lower and middle troposphere associated with either in situ sources of NO or long-range transport of pollution. The paper also illustrates the sensitivity of this O3 production/loss state to H2O and NO concentrations, photolysis rates, and temperatures.

 

PM10 Concentration Measurements In Dublin City PM10 Concentration Measurements In Dublin City

Date added: 07/31/1998
Date modified: 07/03/2009
Filesize: 4.08 MB

Jennings, S.G. (1998). How dirty is Dublin air? Technology Ireland, 30, 40-43.


Abstract


Mass concentration of ambient particulate matter with an aerodynamic diameter less than 10μm (PM10) are reported for the first time for a range of sites in Dublin City over a 6 month period from January 1st 1996 to June 30th 1996. PM10 gravimetric mass concentration measurements are made with low flow Partisol 2000 air samplers using an impaction type PM10 inlet and 47mm diameter glass fibre filters. In addition, much finer time resolution measurements (minimum sampling frequency of 30 minutes) are made using a tapered element oscillating microbalance (TEOM) PM10 mass monitor. These PM10 mass concentrations methods are also compared with mass concentration inferred using the standard black smoke method. Analysis of the ambient mass concentration data with reference to traffic density and meteorological influences are presented. Results for the first six months of 1996 show that the average PM10 values range from a high of 49 μg/m3 at the Dublin city centre site to 14 μg/m3 at one of the suburban sites. Intercomparison between PM10 and black smoke mass concentrations show that the relationship is site specific. Statistical analysis between PM10 levels and car traffic number show a positive correlation while a weak negative correlation is found between PM10 levels and rainfall amount, wind speed and air temperature.

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

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

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


Abstract


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

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

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

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


Abstract


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

 

Physical characterization of aerosol particles during nucleation events Physical characterization of aerosol particles during nucleation events

Date added: 07/31/2001
Date modified: 07/03/2009
Filesize: 435.73 kB

Aalto, P.P., K. Hämeri, E. Becker, R. Weber, J. Salm, J.M. Mäkelä, C. Hoell, C.D. O'Dowd, H. Karlsson, H-C. Hansson, M. Väkevä, I. Koponen, G. Buzorius, and M. Kulmala, Physical characteristics of aerosol particles during nucleation events. in press Tellus B, 53, 344-345,, 2001.


Abstract


Particle concentrations and size distributions have been measured from different heights inside and above a boreal forest during three BIOFOR campaigns (14 April–22 May 1998, 27 July– 21 August 1998 and 20 March–24 April 1999) in Hyytia¨la¨, Finland. Typically, the shape of the background distribution inside the forest exhibited 2 dominant modes: a fine or Aitken mode with a geometric number mean diameter of 44 nm and a mean concentration of 1160 cm−3 and an accumulation mode with mean diameter of 154 nm and a mean concentration of 830 cm−3. A coarse mode was also present, extending up to sizes of 20 mm having a number concentration of 1.2 cm−3, volume mean diameter of 2.0 mm and a geometric standard deviation of 1.9. Aerosol humidity was lower than 50% during the measurements. Particle production was observed on many days, typically occurring in the late morning. Under these periods of new particle production, a nucleation mode was observed to form at diameter of the order of 3 nm and, on most occasions, this mode was observed to grow into Aitken mode sizes over the course of a day. Total concentrations ranged from 410–45 000 cm−3, the highest concentrations occurring on particle production days. A clear gradient was observed between particle concentrations encountered below the forest canopy and those above, with significantly lower concentrations occurring within the canopy. Above the canopy, a slight gradient was observed between 18 m and 67 m, with at maximum 5% higher concentration observed at 67 m during the strongest concentration increases.

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

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

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


Abstract


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

Physical and chemical properties of aerosol during the North Atlantic Marine Boundary Layer Exp Physical and chemical properties of aerosol during the North Atlantic Marine Boundary Layer Exp

Date added: 08/07/2003
Date modified: 07/27/2009
Filesize: 32.66 kB
Coe, H.; THE NAMBLEX AEROSOL TEAM Physical and chemical properties of aerosol during the North Atlantic Marine Boundary Layer EXperiment (NAMBLEX) [EGU04-A-03236].
Abstract

 

A wide range of particle physical and chemical measurements were made at Mace Head on the Atlantic coast during the North Atlantic Marine Boundary Layer EXperiment during August 2002. The measurements included particle number, and size distribution from 10 nm to 20 um diameter. These data will be used to show how the loss rates of gaseous species with different uptake coefficients to aerosol impacts on the lifetime of species in the MBL and indicates the extent to which aerosol are an effective sink for a range of species. An Aerodyne Aerosol Mass Spectrometer was used to make continuous measurements of sulphate, nitrate and organic mass loading in the submicron size range at high time resolution. These data are compared with the analyses of filters from multi stage impactor sample collections. The air masses sampled during the experiment are characterised in terms of the aerosol physics and chemistry and comparisons between the AMS and the impactor samples will be shown.Westerly winds provide near background concentrations but significant loadings were observed in several air masses. Gas phase VOC data will be used as a guide to the photochemical age of the air and this will be compared with the aerosol components measured by the AMS. Correlations between gas phase oxidised VOC and the organic aerosol loading will be shown.

Photochemical ozone formation in north west Europe and its control Photochemical ozone formation in north west Europe and its control

Date added: 08/07/2003
Date modified: 07/23/2009
Filesize: 635.36 kB

DERWENT, R.G., Jenkin, M.E., Saunders, S.M., Pilling, M.J., Simmonds, P.G., Passant, N.R., Dollard, G.J., Dumitrean, P. and Kent, A., 2003: Photochemical ozone formation in north west Europe and its control. Atmos Environ, 37, 1,983-1,991.


Abstract


A photochemical trajectory model together with a Master Chemical Mechanism and a highly speciated emission inventory for organic compounds have been used to describe the formation of ozone in north west Europe and to identify the most prolific ozone-forming organic compounds. Observations are reviewed to assess the impact of emission controls on their urban volatile organic compound (VOC) concentration trends with time. The observed trends are then used to deduce the likely trends in episodic peak ozone concentrations and to compare them with observed trends in peak ozone concentrations. It is concluded that it is likely that motor vehicle emission controls have brought about a substantial reduction in episodic peak ozone concentrations in north west Europe during the 1990s.

 

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

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

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


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

 

Peroxy radical formation at Mace Head during NAMBLEX Peroxy radical formation at Mace Head during NAMBLEX

Date added: 08/07/2003
Date modified: 07/23/2009
Filesize: 34.15 kB
Fleming, Z.L.; Monks, P.S.; Rickard, A.R.; Heard, D.E.; Stills, T; Sommariva, R; Brough, N; Penkett, S.A.; Lewis, A.C.; Lee, J.D.Peroxy radical formation at Mace Head during NAMBLEX [EGU04-A-04097].

Abstract

 

Analysis of peroxy radical (HO$_2$ + $\Sigma$RO$_2$) data taken using the dual inlet Leicester/UEA PEroxy Radical Chemical Amplification (PERCA) instrument during the North Atlantic Marine Boundary Layer Experiment (NAMBLEX 2002) at the Mace Head Atmospheric Research Station in county Galway, on the west coast of Ireland will be presented.
Photolysis rate coefficients of a variety of compounds (including ozone, formaldehyde and nitrous acid), measured using a spectral radiometer were seen to explain to a large extent the shape of the diurnal variation in the peroxy radicals. In the evening, (after the ozone photolysis is no longer significant) on many days there was still a large amount of radical production appearing to come from formaldehyde photolysis. On a minute timescale, NO$\rm _x$ is shown to suppress radical production but for the averaged peroxy radicals versus NO$\rm _x$ the relationship in daylight hours

there is a maximum in radical production at a NO$\rm _x$ level of just less than 0.5 ppbv and a marked shape to these plots. At nighttime, evidence for an increase in radical production with increasing NO$\rm _x$ shows that NO$_3$ chemistry is a contributor to radical production. Net photochemical ozone production and destruction rates were calculated using amongst other measurements, the peroxy radical data and showed that there were few periods during daylight hours when more ozone was destroyed than produced. In general there was usually a small overall production of ozone. The highest ozone producing periods were when the radical concentrations were high and the NO$\rm
_x$ relatively low. HO2 data was compared with total peroxy radical data to examine the ratios of organic to hydrogen peroxy radicals. As the NO$\rm _x$ concentration increased, the proportion of HO$_2$ increased. Examining the contribution of a variety of VOCs to radical production (via their reaction with OH) may explain the variation in
the HO$_2$ : RO$_2$ ratio.

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