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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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Dimethyl sulfide and its oxidation products in the atmosphere of the Atlantic and Southern Ocea Dimethyl sulfide and its oxidation products in the atmosphere of the Atlantic and Southern Ocea

Date added: 08/06/1996
Date modified: 07/23/2009
Filesize: 823.17 kB

Davison, B., C.D. O'Dowd, C.N. Hewitt, M.H. Smith, R.M. Harrison, D.A. Peel, E. Wolf, R. Mulvaney, M. Schwikowski and U. Baltensperger, Dimethyl Sulfide and its Oxidation Products in the Atmosphere of the Atlantic and Southern Oceans, Atmos. Environ., 30, 1895-1906, 1996


Abstract


Dimethyl sulfide, methane sulfonate, non-sea-salt sulfate and sulfur dioxide concentrations in air were obtained during a cruise between the U.K. and the Antarctic during the period October 1992-January 1993. In equatorial regions (30°N to 30°S) the atmospheric DMS concentration ranged from 3 to 46 ng (S)m-3 with an average of 18 ng(S)m-3. In the polar waters and regions south of the Falkland Islands concentrations from 3 to 714 ng(S)m-3 were observed with a mean concentration of 73 ng(S)m-3. Methane sulfonate concentrations were also enhanced in the vicinity of the Antarctic Peninsula and in the Weddell Sea. A simple model of DMS oxidation was used to estimate the ocean to atmosphere flux rate, and this was found to be within the range of previous estimates, with a mean value of 1011 ng (S) m-2 h-1.

 

Dimethyl sulfide, methane sulfonic acid and physicochemical aerosol properties in Atlantic air Dimethyl sulfide, methane sulfonic acid and physicochemical aerosol properties in Atlantic air

Date added: 08/06/1996
Date modified: 07/01/2009
Filesize: 1.18 MB

Davison, B.M., C.N. Hewitt, R.M. Harrison, M. Schwikowski, U. Baltensperger, C. O'Dowd and M.H. Smith. Dimethyl sulfide, methane sulfonic acid and physico-chemical aerosol properties in Atlantic air from the United Kingdom to Halley Bay. J. Geophys. Res., 101, 22855-22874, 1996.


Abstract


The concentrations of dimethyl sulfide in air were obtained during a cruise between the United Kingdom and the Antarctic in the period October 1992 to January 1993 using a method of sampling and analysis optimized to avoid interferences from oxidants. In equatorial regions (30°N to 30°S) the atmospheric DMS concentration ranged from 3 to 46 ng (S) m-3, with an average of 18 ng (S) m-3, In the polar waters and regions south of the Falkland Islands, concentrations from 3 to 714 ng (S) m-3 were observed, with a mean concentration of 73 ng (S) m-3. The concentrations of a range of DMS oxidation products were also obtained. No clear relationships between reactant and product concentrations were seen. Information on particle number concentration, Fuchs surface area and the thermal volatility characteristics of the ambient aerosol was obtained, but again no clear relationships with sulfur concentrations were observed. Accumulation mode particle concentrations averaged 25 cm-3 in the clean marine and polar air masses south of 58°S while background condensation nuclei (CN) concentrations were of the order of 400-600 cm-3. Simplistic calculations suggest that a particle source strength of about 20-60 particles cm-3 d-1 is required to sustain this background CN concentration. It is not clear whether boundary layer nucleation of new CN or entrainment from the free troposphere provided the source of CN. Periods of elevated CN concentrations (>4000 cm-3) were regularly observed in the boundary layer over the Weddell Sea and were attributed to bursts of new particle formation. However, shortly after these nucleation events the CN concentration rapidly decayed to the background level through coagulation losses, suggesting little impact on the background CN or cloud condensation nuclei (CCN) concentration.

 

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

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

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


Abstract


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

Distribution and Sea-Air Fluxes of Biogenic Trace Gases in the Eastern Atlantic Ocean Distribution and Sea-Air Fluxes of Biogenic Trace Gases in the Eastern Atlantic Ocean

Date added: 08/06/2000
Date modified: 07/27/2009
Filesize: 1.44 MB

Baker, A. R., S. M. Turner, W. J. Broadgate, A. Thompson, G. B. McFiggans, O. Vesperini, P. D. Nightingale, P. S. Liss, and T. D. Jickells (2000), Distribution and Sea-Air Fluxes of Biogenic Trace Gases in the Eastern Atlantic Ocean, Global Biogeochem. Cycles, 14(3), 871–886.


Abstract


A number of atmospherically important trace gases (dimethyl sulphide (DMS), methyl iodide (CH3I), and nonmethane hydrocarbons (NMHCs)) were measured simultaneously in the eastern Atlantic Ocean during May 1997. This investigation was part of the U.K. Atmospheric Chemistry Studies in the Oceanic Environment (ACSOE) Community Research Program and covered a 200 by 200 nautical mile (1 nautical mile is 1.852 km) area to the west of the Mace Head Atmospheric Research Station on the coast of Ireland. Different spatial and temporal patterns were observed for each of the gases, showing that distinct sources dominate their production in this region: specific species of phytoplankton (DMS), macroalgae (CH3I), total phytoplankton biomass (isoprene), and photochemistry (ethene). Sea-to-air fluxes of the gases are calculated for near and offshore domains, and their temporal variations are discussed. A simple photochemical box model has been used to assess the contributions of the gas fluxes to the levels of the gases observed at Mace Head. Results show that the area studied may constitute a substantial source of DMS, a weak source of CH3I, a small source of ethene at night, and an insignificant source of isoprene to atmospheric levels of these gases measured at Mace Head in western Ireland.

 

Diurnal cycles of short-lived tropospheric alkenes at a north Atlantic coastal site Diurnal cycles of short-lived tropospheric alkenes at a north Atlantic coastal site

Date added: 08/07/1999
Date modified: 07/27/2009
Filesize: 210.82 kB

A.C. Lewis J.B. McQuaid, N. Carslaw, M.J. Pilling.,; Short Communication Diurnal cycles of short-lived tropospheric alkenes at a north Atlantic coastal site,. Atmospheric Environment 33 (1999) 2417Ð2422 2419


Abstract


Observation of diurnal cycles in atmospheric concentrations of reactive alkenes are reported from measurements performed at a North Atlantic coastal site (Mace Head, Eire 53°19'34N; 9°54'14W). Species seen to exhibit distinct cycles included isoprene, ethene, propene, 1-butene, iso-butene and a substituted C6 alkene. Five hundred and thirty air mass classified measurements were performed over a 4 week period at approximately hourly frequency and demonstrate that during periods when air flow resulted from unpolluted oceanic regions a clear daily cycle in concentrations existed, peaking at around solar noon for all species. These observations support the proposed mechanism of production via photochemical degradation of organic carbon in sea water. The observed concentrations showed strong correlation (propene R2 > 0.75) with solar flux, with little relationship to other meteorological or chemical parameters. The species' short atmospheric lifetimes indicate that the source of emission was from local coastal waters within close proximity of the sampling site. At solar noon concentrations of reactive alkenes from oceanic sources were responsible for up to 88% of non-methane hydrocarbon reaction with the hydroxyl radical at this coastal marine site.

 

DOAS measurements of I2, BrO,IO, OIO and NO3 at mace head, ireland DOAS measurements of I2, BrO,IO, OIO and NO3 at mace head, ireland

Date added: 08/06/2003
Date modified: 07/27/2009
Filesize: 33.33 kB

Saiz-Lopez, A., Shillito, J. A., Coe, H., and Plane, J. M. C.: Measurements and modelling of I2, IO, OIO, BrO and NO3 in the mid-latitude marine boundary layer, Atmos. Chem. Phys. Discuss., 5, 9731-9767, 2005.


Abstract


Time series observations of molecular iodine (I2), iodine oxides (IO, OIO), bromine oxide (BrO), and the nitrate radical (NO3) in the mid-latitude coastal marine boundary layer (MBL) are reported. Measurements were made using a new long-path DOAS instrument during a summertime campaign at Mace Head on the west coast of Ireland. I<2 was detected using the B3Π(0+u)−X1Σxg electronic transition between 535 and 575 nm. The I2 mixing ratio was found to vary from below the detection limit (~5 ppt) up to a nighttime maximum of 93 ppt. Along with I2, observations of IO, OIO and NO3 were also made during the night. Surprisingly, IO and OIO were detected at mixing ratios up to 2.5 and 10.8 ppt, respectively. A model is employed to show that the reaction between I2 and NO3 is the likely nighttime source of these radicals. The BrO mixing ratio varied from below the detection limit at night (~1 ppt) to a maximum of 6 ppt in the first hours after sunrise. A model shows that this diurnal behaviour can be explained by halogen recyling in sea-salt aerosol building up photolabile precursors of atomic Br during the preceding night. In the same campaign a zenith sky DOAS was employed to determine the column density variation of NO3 as a function of solar zenith angle (SZA) during sunrise, from which vertical profiles of NO3 through the troposphere were obtained. On several occasions a positive gradient of NO3 was observed over the first 2 km, possibly due to dimethyl sulphide (DMS) removing NO3 at the ocean surface.

Dual pathways for atmospheric sulfuric acid-water nucleation mechanisms Dual pathways for atmospheric sulfuric acid-water nucleation mechanisms

Date added: 04/08/2009
Date modified: 11/01/2009
Filesize: 988.72 kB
Laaksonen, A.,  M. Kulmala, T. Berndt, F. Stratmann, S. Mikkonen, A. Ruuskanen, K.E.J. Lehtinen, M. Dal Maso, P. Aalto, T. Petäjä, I. Riipinen, R. Janson, F. Arnold, M. Hanke, J.Ücker, B. Umann, K. Sellegri,  C.D. O’Dowd, Y. Viisanen, Dual pathways for atmospheric sulfuric acid-water nucleation mechanisms,, Atmos. Chem. Phys.,  8, 7255–7264, 2008.

Abstract


Atmospheric new particle formation is generally thought to occur due to homogeneous or ion-induced nucleation of sulphuric acid. We compare ambient nucleation rates with laboratory data from nucleation experiments involving either sulphuric acid or oxidized SO2. Atmospheric nucleation occurs at H2SO4 concentrations 2–4 orders of magnitude lower than binary or ternary nucleation rates of H2SO4 produced from a liquid reservoir, and atmospheric H2SO4 concentrations are very well replicated in the SO2 oxidation experiments. We hypothesize these features to be due to the formation of free HSO5 radicals in pace with H2SO4 during the SO2 oxidation. We suggest that at temperatures above 250K these radicals produce nuclei of new aerosols much more efficiently than H2SO4. These nuclei are activated to further growth by H2SO4 and possibly other trace species. However, at lower temperatures the atmospheric relative acidity is high enough for the H2SO4–H2O nucleation to dominate.

Eastern Atlantic Spring Experiment 1997 (EASE97) 2 Comparisions of model concentrations of OH... Eastern Atlantic Spring Experiment 1997 (EASE97) 2 Comparisions of model concentrations of OH...

Date added: 08/06/2002
Date modified: 07/27/2009
Filesize: 640.01 kB

Carslaw,m N.; Creasey, D.J.; Heard, D.E.; Jacobs, P.; Lee, J.D.L.; Lewis, A.C.; McQuaid, J.B.; Pilling, M.J.; Bauguitte, S.; Penkett, S.A.; Monks, P.S.; Salisbury, G. (2002) Eastern Atlantic Spring Experiment 1997 (EASE97) - 2. Comparisons of model concentrations of OH, HO2, and RO2 with measurements, Journal of Geophysical Research, 107, pp.4190/ ACH5


Abstract


An observationally constrained box model has been used to investigate the chemistry of the marine boundary layer at the Mace Head Atmospheric Research Station, a remote site on the west coast of Ireland. The model aims to simulate concentrations of the hydroxyl (OH) and hydroperoxy (HO2) radicals measured by an in situ fluorescence assay by gas expansion instrument, and the sum of peroxy radicals ([HO2] + Σ[RO2]) as determined by a peroxy radical chemical amplification instrument. The model has been constructed based on observed concentrations of nonmethane hydrocarbons, measured in situ during the campaign by gas chromatography. The chemical mechanism for the model is a subset of a comprehensive master chemical mechanism. This paper details comparisons of the concentrations of modeled and measured radical species from a field campaign held at Mace Head during spring 1997. The air masses arriving at the site have been split into three categories depending on their origin and chemical characteristics and model-measurement comparisons carried out for each air mass. The average model-measurement ratios are 2.4 for [OH], 3.6 for [HO2], and 0.9 for ([HO2] + Σ[RO2]), respectively, between 1100 and 1500 hours: the level of agreement is better for all three sets of radicals in the cleanest air mass. Possible reasons for the observed discrepancies are discussed. In addition, a rate of production analysis is used to identify key OH and HO2 reactions in the three air masses. The rate of OH production from HO2 with NO exceeds that from ozone photolysis by factors of 2–6 in the polluted air masses studied. In cleaner air from the northern polar region, primary production from ozone photolysis exceeds that from HO2 + NO by a factor of 2.5. HO2 and CH3O2 dominate the peroxy radical composition in all air masses, but peroxy radicals derived from the oxidation of nonmethane hydrocarbons are more important in polluted air masses.

 

Eastern Atlantic Spring Experiment 1997 (EASE97)1. Measurements of OH and HO2 concentrations at Eastern Atlantic Spring Experiment 1997 (EASE97)1. Measurements of OH and HO2 concentrations at

Date added: 08/06/2002
Date modified: 07/01/2009
Filesize: 285.24 kB

Creasey, D. J., D. E. Heard, and J. D. Lee (2002), Eastern Atlantic Spring Experiment 1997 (EASE97) 1. Measurements of OH and HO2 concentrations at Mace Head, Ireland, J. Geophys. Res., 107(D10), 4091, doi:10.1029/2001JD000892.


Abstract


We report measurements of the hydroxyl (OH) and hydroperoxy (HO2) radicals, taken over 20 days, in the remote marine boundary layer at Mace Head, Ireland, during April and May 1997. OH was monitored directly by laser-induced fluorescence (LIF) spectroscopy at 308 nm, and HO2 was measured by chemical conversion to OH upon the addition of NO, with subsequent detection by LIF. The detection limit of the instrument at midday for OH was 6.0 × 105 molecule cm−3 (0.0024 parts per trillion by volume (pptv)) and for HO2 was 3.0 × 106 molecule cm−3 (0.12 pptv), as defined for a signal integration period of 2.5 min and a signal-to-noise ratio of 1. Midday OH and HO2 concentrations were between 2.0–6.0 × 106 molecule cm−3 (0.08–0.24 pptv) and 0.5–3.5 × 108 molecule cm−3 (2.5–14 pptv), respectively. OH concentrations correlated well with the rate of OH production from ozone photolysis for clean air from the Arctic containing low concentrations of both NOx and nonmethane hydrocarbons. A lower correlation was observed in more polluted air that originated from the United Kingdom and continental Europe. Measurements of OH and HO2 were made throughout two nights, and although no evidence was seen for OH above the detection limit, up to 2 pptv of HO2 was observed. The measured HO2/OH ratio was in good agreement with the predictions of a steady state expression for NO in the range 75–400 pptv.

 

Eddy correlation measurements of ozone fluxes over coastal waters west if Ireland Eddy correlation measurements of ozone fluxes over coastal waters west if Ireland

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 980.87 kB

McVeigh, P., C. O’Dowd, and H. Berresheim, Eddy correlation measurements of ozone fluxes over coastal waters west if Ireland,  Adv. in Meteorol., Volume 2010, Article ID 754941, doi:10.1155/2010/754941, 2010.

 


 Measurements of ozone fluxes using the eddy-correlation (EC) technique were carried out for the first time at the Mace Head atmospheric research station, on the west coast of Ireland between August-October 2009. Vertical exchange of ozone was measured from a tower platform at 22m above mean sea level to study fluxes over coastal waters excluding the tidal region. The results were averaged over 30 min and exhibited predominantly downward but also upward transport of ozone in the boundary layer. Data quality was found to be high based on inspection of cospectra and micrometeorological measurements. During the study period, a major physical influence on O3 fluxes was found to be wind speed. Measured fluxes were of the same magnitude as reported in previous open ocean studies ranging from approximately +0.2 to 0.5 μg m2 s1 (0.017 μg m2 s1 on average, corresponding to a deposition velocity of 0.25mm s1 or a surface resistance of 4.13 s mm1). These results are considered to represent ozone fluxes over shallow coastal waters west of Ireland for conditions during summer and fall not affected by phytoplankton blooms.

Effect of Horizontal Resolution on Meteorology and Air-Quality Prediction with a Regional Scale Mode Effect of Horizontal Resolution on Meteorology and Air-Quality Prediction with a Regional Scale Mode

Date added: 05/12/2011
Date modified: 05/12/2011
Filesize: 4.49 MB

Varghese, S., B. Langmann and C. D. O’Dowd, Effect of Horizontal Resolution on Meteorology and Air-Quality Prediction with a Regional Scale Model, Atmos. Res., doi:10.1016/j.atmosres.2011.02.007, 2011

 


 

Horizontal resolution sensitivity can significantly contribute to the uncertainty in predictions of meteorology and air-quality from a regional climate model. In the study presented here, astate-of-the-art regional scale atmospheric climate-chemistry-aerosol model REMOTE is used to understand the influence of spatial model resolutions of 1.0°, 0.5° and 0.25° on predicted meteorological and aerosol parameters for June 2003 for the European domain comprising North-east Atlantic and Western Europe. Model precipitation appears to improve with resolution while wind speed has shown best results for 0.25° resolution for most of the stations compared with ECAD data. Low root mean square error and spatial bias for surface pressure, precipitation and surface temperature show that the model is very reliable. Spatial and temporal variation in black carbon, primary organic carbon, sea-salt and sulphate concentrations and their burden are presented. In most cases, chemical species concentrations at the surface show no particular trend or improvement with increase in resolution. There has been a pronounced influence of horizontal resolution on the vertical distribution pattern of some aerosol species. Some of these effects are due to the improvement in topographical details, flow characteristics and associated vertical and horizontal dynamic processes. The different sink processes have contributed very differently to the various aerosol pecies in terms of deposition (wet and dry) and sedimentation which are strongly linked to the meteorological processes. Overall, considering the formance of meteorological parameters and chemical  pecies concentrations, a horizontal model resolution of 0.5° is suggested to achieve easonable results within the limitations of this model.

Effect of instrumental particle sizing resolution on the modelling of aerosol radiative parameters Effect of instrumental particle sizing resolution on the modelling of aerosol radiative parameters

Date added: 03/04/2010
Date modified: 03/04/2010
Filesize: 886.14 kB

Chamaillard, K., S. G.  Jennings, D. Ceburnis, Y.J. Yoon and C. O’Dowd.  Effect of instrumental particle sizing resolution on the modelling of aerosol radiative parameters. doi:10.1016/j.jqsrt.2009.11.005, Journal of Quantitative Spectroscopy and Radiative Transfer Volume 111, Issue 5, 2010, Pages 753-771


 

 Abstract.

 

A more realistic estimation of the scattering and hemispheric backscattering coefficients, ssp and sbsp, and their respective optical cross section, Csca and Cbk, of aerosol particles is presented on the basis of the exact resolution of the width of the size bins of the particle counter instruments when size distribution measurements are used, and, with the exact optical detector instruments ability. The scattering and hemispheric back scattering cross sections, Csca and Cbk, of the particles are averaged over the full size bins of the particle counter instrument, while the sequantities are usually estimated only on the value of the mean geometric diameter of each size bin. Six instruments, the APS, ASASP-X, DMPS,FSSP-100, ELPI, and SMPS frequently used in particle size distribution measurements are reviewed, for spherical sea-salt particles at a wavelength l=0.55 mm. The comparison using the conventional geometric mean diameter versus the use of the full size bin leads to large amount of errors for the optical cross section with non-negligible effects on their respective optical coefficients.The maximal accuracy expected for these optical quantities depend on the particle diameter as well as on the channel width of the instruments, and are also function of the angular detector probe used to measure them..

 


Effects of continental boundary layer evolution convection  turbulence and entrainment on... Effects of continental boundary layer evolution convection turbulence and entrainment on...

Date added: 08/06/2001
Date modified: 07/01/2009
Filesize: 740.44 kB

Nilsson, E.D., U. Rannik, G. Buzorius, C.D. O'Dowd, Effects of continental boundary layer evolution, convection, turbulence and entrainment on aerosol formation, Tellus B, 53, 441-461,, 2001.


Abstract


Aerosol nucleation events occurring in the continental boundary layer over the boreal forest region in Finland, during the BIOFOR experiment, have been examined to elucidate the rôle of micrometeorology in promoting such events. Invariably, during the spring campaign of 1999. nucleation events occurred in Arctic and polar air masses during cold air outbreaks. Under clear-sky conditions, typical of these synoptic meteorological patterns, the boundary layer evolution was characterized by the rapid growth of a mixed layer, convection and strong entrainment, first from the residual later and later from the free troposphere. It was found that the freshly nucleated particles were detected within two hours from the onset of strong turbulent kinetic energy, independent of how fast the boundary layer evolved. When considering the growth time from cluster size of ≃ 1 nm to detectable sizes of 3 nm. the nucleation and onset of strong turbulence coincided almost exactly. The most likely site for nucleation to take place was the mixed layer or the entrainment zone, while the forest canopy and the free troposphere could be excluded as the nucleation region. There are several possible explanations for the correlation between the onset of turbulence and nucleation: (1) new aerosols or clusters may have been entrained from the residual layer into the mixed layer where they then (in the case of clusters) underwent growth to detectable sizes: (2) two or more precursor gases may have been mixed with each other over the entrainment zone; (3) the adiabatic cooling in the rising convective plumes and the turbulent fluctuation in temperature and vapors by the entrainment flux may have enhanced aerosol formation; (4) a sudden decrease in preexisting aerosol due to dilution of the mixed layer aerosol by entrained air may have reduced the vapor sink enough to initiate nucleation. However, the lack of vertical profile measurements of nucleation mode aerosols, precursor vapors and turbulent fluctuations throughout and above the mixed-layer results in it remaining an open question as to which one of these processes dominates.

 

Effects of particulate complex refractive index and particle size distribution variations on atmospheric extinction Effects of particulate complex refractive index and particle size distribution variations on atmospheric extinction

Date added: 08/01/1978
Date modified: 07/01/2009
Filesize: 851.05 kB
Jennings, S.G., and Pinnick, R.G.  (1978)- Effects of particulate refractive index and particle size distribution variations on atmospheric extinction and absorption for visible to middle-IR wavelengths. American Meteorological Society Third Conference on Atmospheric Radiation, Davis, California, 6-9.

Abstract


A comprehensive sensitivity study has been made, using Mie theory, to determine the effect of realistic variations in values of real and imaginary parts of the complex index of refraction on volume extinction and absorption coefficients for a wide range of lognormal particle size distributions (defined by geometric mean radius r sub g and geometric standard deviation sigma sub g). Wavelengths lambda from visible (0.55 micrometers) through middle-infrared (10.6 micrometers) were considered. Extinction is independent of complex index to within 20 percent for the majority of realistic particle size distributions, providing lambda < or = 2 micrometers. However, changes in extinction by up to an order of magnitude are caused by realistic variations in refractive indexes for 2 < or = lambda < or = 10.6 micrometers, with real index being more important in affecting extinction than imaginary index.

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

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

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


Abstract


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

 

Electrical charging of water drops in polarizing electric fields. Electrical charging of water drops in polarizing electric fields.

Date added: 08/01/1975
Date modified: 07/01/2009
Filesize: 2.02 MB

Jennings, S.G.  (1974)- Electrical charging of water drops in polarizing electric fields.  J. Electrostatics, 1,  15-25.


Abstract


Measurements were made of the electric charge acquired by drops of mean radius of about 750 μm as they fell through a cloud of water droplets of mean radius 16 μm, in the presence of a vertical electric field E, the value of which could be varied from 4.5 to 27 kV m−1. It was found that the proportion of interactions which resulted in separation (and, therefore, in electric charge transfer, as a consequence of the inductive process of electrification) decreased from about 1% in the weaker fields to about 0.2% in the strongest ones.

This work suggests that the collisions between polarised raindrops and cloud droplets in natural clouds could give rise, very effectively, to the production of electric fields of about 30 kV m−1 but that significantly larger fields could not be produced since all collisions in higher fields would result in permanent coalescence.

Electrostatic Deposition in ionic Diffussion Electrostatic Deposition in ionic Diffussion

Date added: 08/31/1968
Date modified: 07/21/2009
Filesize: 1.69 MB
F. Anderson, P.J Nolan and T.C. O'Connor, Electrostatic Deposition in ionic Diffussion, Volume 66, Section A, No. 5, 1968

Abstract

 

Errors in the determination of ionic diffusion coefficients caused by the neglect of electrostatic deposition are examined. Correction formulae applicable to low ionic concentrations are derived for cylindrical channels. These are similiar to the Fuchs formulae for rectangular channels. Formulae applicable in the case of high ionic concentration are also derived.

For singly charged particles the correction tot the diffusion coefficient under the usual experimental conditions is about two or three per cent. The error becomes large when the number electronic charges per ion aproaches 100. Previous Dublin experiments with multiply charged nuclei are examined in this connection and corrections applied. The Corrections do not invalidate the main conclusion of these experiments that the Einstein equation B=D/KT does not apply in the absence of charge equilibrium.

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

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

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


Abstract


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

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

Emission rates of C8–C15 VOCs from seaweed and sand in the inter-tidal zone at Mace Head, Irela Emission rates of C8–C15 VOCs from seaweed and sand in the inter-tidal zone at Mace Head, Irela

Date added: 08/07/2002
Date modified: 07/27/2009
Filesize: 167.86 kB

Emission rates of C8 - C15 VOCs from seaweed and sand in the inter-tidal zone at Mace Head, Ireland (2002) J.H. Sartin, C.J. Halsall, S. Hayward and C.N. Hewitt, Atmospheric Environment , 36, 5311 - 5321


Abstract


Emission fluxes for a range of C8-C15 volatile organic compounds (VOCs) were determined from the seaweed Fucus spiralis (spiral wrack) and an adjacent sand surface during low tide on the coastline of Mace Head, Ireland. These two surface types, assessed using dynamic flux chamber systems, are typical of the Mace Head inter-tidal zone. A range of n-alkanes and oxygenates were routinely identified in the measurement of chamber air. Examination of the odd/even n-alkane ratios and use of the carbon preference index (CPI) suggested a biogenic source for these compounds (CPIs >2 in for all samples). Fluxes of n-pentadecane, the most predominant n-alkane, ranged from 0.2 to 5.1mugm-2h-1 (0.9-24nmolm-2h-1), while oxygenates such as nonanal and decanal had fluxes ranging from <0.1 to 4.4mugm-2h-1 (<0.1-31nmolm-2h-1) and <0.1 to 4.6mugm-2h-1 (<0.1-30nmolm-2h-1), respectively. Seaweed emission rates for n-pentadecane were correlated with photosynthetically active radiation (PAR) (rs=0.94) while emissions from sand showed correlation with temperature (rs=0.85). This suggests a possible biochemical route controlling the release of n-pentadecane from spiral wrack, and temperature-driven volatilisation from sand. Volatilisation from residual seawater trapped in the sand may explain the comparable flux of both n-alkanes and oxygenates from this surface. Unlike the n-alkanes, oxygenate fluxes from sand correlate with PAR, suggesting a photodependent production from organic carbon residues present in seawater. Comparison with previous flux estimates from coastal seawater indicates that the two source types (Fucus spiralis and bare sand) are significant but not dominant sources of these VOCs.

 

Emissions from Ships with respect to Their Effects on Clouds Emissions from Ships with respect to Their Effects on Clouds

Date added: 08/06/2000
Date modified: 07/01/2009
Filesize: 302.93 kB

Hobbs, P.V., T.J. Garrett, and co-authors, 2000: Emissions from ships with respect to their effects on clouds, J. Atmos. Sci., 57, 2570-2590


Abstract


Emissions of particles, gases, heat, and water vapor from ships are discussed with respect to their potential for changing the microstructure of marine stratiform clouds and producing the phenomenon known as ship tracks. Airborne measurements are used to derive emission factors of SO2 and NO from diesel-powered and steam turbine-powered ships, burning low-grade marine fuel oil (MFO); they were ∼15-89 and ∼2-25 g kg-1 of fuel burned, respectively. By contrast a steam turbine-powered ship burning high-grade navy distillate fuel had an SO2 emission factor of ∼6 g kg-1. Various types of ships, burning both MFO and navy distillate fuel, emitted from ∼4 X 1015 to 2 X 1016 total particles per kilogram of fuel burned (∼4 X 1015-1.5 X 1016 particles per second). However, diesel-powered ships burning MFO emitted particles with a larger mode radius (∼0.03-0.05 μm) and larger maximum sizes than those powered by steam turbines burning navy distillate fuel (mode radius ∼0.02 μm). Consequently, if the particles have similar chemical compositions, those emitted by diesel ships burning MFO will serve as cloud condensation nuclei (CCN) at lower supersaturations (and will therefore be more likely to produce ship tracks) than the particles emitted by steam turbine ships burning distillate fuel. Since steam turbine-powered ships fueled by MFO emit particles with a mode radius similar to that of diesel-powered ships fueled by MFO, it appears that, for given ambient conditions, the type of fuel burned by a ship is more important than the type of ship engine in determining whether or not a ship will produce a ship track. However, more measurements are needed to test this hypothesis. The particles emitted from ships appear to be primarily organics, possibly combined with sulfuric acid produced by gas-to-particle conversion of SO2. Comparison of model results with measurements in ship tracks suggests that the particles from ships contain only about 10% water-soluble materials. Measurements of the total particles entering marine stratiform clouds from diesel-powered ships fueled by MFO, and increases in droplet concentrations produced by these particles, show that only about 12% of the particles serve as CCN. The fluxes of heat and water vapor from ships are estimated to be ∼2-22 MW and ∼0.5-1.5 kg s-1, respectively. These emissions rarely produced measurable temperature perturbations, and never produced detectable perturbations in water vapor, in the plumes from ships. Nuclear-powered ships, which emit heat but negligible particles, do not produce ship tracks. Therefore, it is concluded that heat and water vapor emissions do not play a significant role in ship track formation and that particle emissions, particularly from those burning low-grade fuel oil, are responsible for ship track formation. Subsequent papers in this special issue discuss and test these hypotheses.

 

Emissions of CH3Br, organochlorines, and organoiodines from temperate macroalgae Emissions of CH3Br, organochlorines, and organoiodines from temperate macroalgae

Date added: 08/05/2001
Date modified: 07/01/2009
Filesize: 249.05 kB

Baker1 J.M.; Sturges W.T.1; Sugier J.; Sunnenberg G.; Lovett A.A.; Reeves C.E.; Nightingale P.D.; Penkett S.A., Emissions of CH3Br, organochlorines, and organoiodines from temperate macroalgae, Chemosphere: Global Science Change, Volume 3, Number 1, January 2001 , pp. 93-106(14)


Abstract


The production rates of a range of low molecular weight halogenated organics have been determined in cultures of five temperate species of macroalgae collected from the north coast of Norfolk, England. Compounds studied included CH3Br, the chlorinated organics CH3Cl, CH2Cl2 and CHCl3, and the iodinated organics CH3I, C2H5I, and CH2ClI. Measurements of a wider range of halocarbon concentrations in an isolated rockpool and in air over the seaweed bed were also conducted to evaluate the local impact of the seaweeds on halocarbon concentrations in the natural environment. Estimates for the global emissions of some of the key halogenated compounds from macroalgae have been derived. In general macrophytes appear not to be globally significant producers of the particular halocarbons studied. In coastal regions, however, the impact on local atmospheric composition and chemistry could be greater.

 

Equilibrium Size of Atmospheric Aerosol Sulfates as a Function of Particle Acidity and Ambient Relative Humidity Equilibrium Size of Atmospheric Aerosol Sulfates as a Function of Particle Acidity and Ambient Relative Humidity

Date added: 07/31/1993
Date modified: 07/01/2009
Filesize: 557.48 kB

Kelly, B.P., & Koutrakis, P. (1993)- Equilibrium size of atmospheric aerosol sulphates as a function of particle acidity and ambient relative humidity. J. Geophy. Res. 98, pp. 7141-7147.


Abstract


Acid aerosol events in Uniontown, Pennsylvania, were studied during the summer of 1990. Size-fractionated acid aerosols were collected using a microorifice cascade impactor. The collected samples were analyzed for hydrogen, sulfate, nitrate, and ammonium ion concentrations. These measurements show evidence of a relationship between the mass median geometric aerodynamic diameter of sulfate particles and both particle acid content (H+/SO4=) and ambient relative humidity. Sulfate particle size increases with both increasing acid content and relative humidity. Considering the uncertainties involved, the growth of atmospheric sulfate particles observed in this study was found to be in good agreement with that predicted on the basis of laboratory-derived data. To our knowledge, this is the first time that such a relationship has been observed under real atmospheric conditions. Therefore the results of this study suggest that laboratory experiments and thermodynamic calculations can be used in order to understand the chemistry of atmospheric sulfates and their impacts on visibility reduction. In addition, we present evidence to suggest that the chemical composition of acid aerosol particles may be related to the ambient relative humidity.

Estimating European emissions of ozone-depleting and greenhouse gases using observations and a Estimating European emissions of ozone-depleting and greenhouse gases using observations and a

Date added: 08/07/2003
Date modified: 07/27/2009
Filesize: 1.48 MB

Manning, A. J., D. B. Ryall, R. G. Derwent, P. G. Simmonds, and S. O'Doherty (2003), Estimating European emissions of ozone-depleting and greenhouse gases using observations and a modeling back-attribution technique, J. Geophys. Res., 108(D14), 4405, doi:10.1029/2002JD002312.


Abstract


The Numerical Atmospheric Dispersion Modeling Environment (NAME) dispersion model driven by three-dimensional (3-D) synoptic meteorology from the Unified Model has been used to determine the fraction of air arriving at Mace Head, Ireland, from different European regions over a 6-year period. These data, along with observations of pollutants at Mace Head and a best fit algorithm, have been used to derive emission estimates over Western Europe. The algorithm starts from randomly generated emission maps and iterates toward the best solution. Using an idealized case study, it has been shown to be effective at distinguishing between distinct source regions. The technique has been applied to two ozone-depleting gases, CFC-11 and CFC-12, and two greenhouse gases, methane and nitrous oxide. The emissions derived compare favorably with existing inventories. The technique is able to provide information regarding the emission distribution across Europe and to estimate area and country contributions; information that for some species is not readily available by other means. It is a different methodology to those currently used and so is a useful tool in verifying existing inventories.

 

Estimating relationships between air mass origin and chemical composition Estimating relationships between air mass origin and chemical composition

Date added: 08/06/2001
Date modified: 07/27/2009
Filesize: 1.49 MB

Methven, J., M. Evans, P. Simmonds, and G. Spain (2001), Estimating relationships between air mass origin and chemical composition, J. Geophys. Res., 106(D5), 5005–5019.


Abstract


Observations of a chemical at a point in the atmosphere typically show sudden transitions between episodes of high and low concentration. Often these are associated with a rapid change in the origin of air arriving at the site. Lagrangian chemical models riding along trajectories can reproduce such transitions, but small timing errors from trajectory phase errors dramatically reduce the correlation between modeled concentrations and observations. Here the origin averaging technique is introduced to obtain maps of average concentration as a function of air mass origin for the East Atlantic Summer Experiment 1996 (EASE96, a ground-based chemistry campaign). These maps are used to construct origin averaged time series which enable comparison between a chemistry model and observations with phase errors factored out. The amount of the observed signal explained by trajectory changes can be quantified, as can the systematic model errors as a function of air mass origin. The Cambridge Tropospheric Trajectory model of Chemistry and Transport (CiTTyCAT) can account for over 70% of the observed ozone signal variance during EASE96 when phase errors are side-stepped by origin averaging. The dramatic increase in correlation (from 23% without averaging) cannot be achieved by time averaging. The success of the model is attributed to the strong relationship between changes in ozone along trajectories and their origin and its ability to simulate those changes. The model performs less well for longer-lived chemical constituents because the initial conditions 5 days before arrival are insufficiently well known.

 

Estimating source regions of European emissions of trace gases from observations at Mace Head Estimating source regions of European emissions of trace gases from observations at Mace Head

Date added: 08/07/2001
Date modified: 07/27/2009
Filesize: 1004.2 kB

D.B. Ryall, R.G. Derwent, P.G. Simmonds, and S.J.O'Doherty. Estimating source regions of European emissions of trace gases from observations at Mace Head. Atmos. Environ. Vol 35, (2001), 2,507-25,23.


Abstract


A technique is described for identifying probable source locations for a range of greenhouse and ozone-depleting trace gases from the long-term measurements made at Mace Head, Ireland. The Met. Office's dispersion model NAME is used to predict concentrations at Mace Head from all possible sources in Europe, then source regions identified as those which consistently lead to elevated concentrations at Mace Head. Estimates of European emissions and their distribution are presented for a number of trace gases for the period 1995-1998. Estimated emission patterns are realistic, given the nature and varied applications of the species considered. The results indicate that whilst there are limitations, useful information about source distribution can be extracted from continuous measurements at a remote site. It is probable that much improved estimates could be derived if observations were available from a number of sites. The ability to assess emissions has obvious implications in monitoring compliance with internationally agreed quota and protocols.

 

EUCAARI ion spectrometer measurements at 12 European sites – analysis of new-particle formation even EUCAARI ion spectrometer measurements at 12 European sites – analysis of new-particle formation even

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 2.55 MB

Manninen, H. E, .T. Nieminen, E. Asmi, S. Gagné, S. Häkkinen, K. Lehtipalo, P. Aalto, M. Vana, A. Mirme, S. Mirme, U. Hõrrak, C. Plass-Dülmer, G. Stange, G. Kiss, A. Hoffer, N. Tör\H{o}, M. Moerman, B. Henzing, G. de Leeuw, M. Brinkenberg, G. N. Kouvarakis, A. Bougiatioti, N. Mihalopoulos, C. O'Dowd, D. Ceburnis, A. Arneth, B. Svenningsson, E. Swietlicki, L. Tarozzi, S. Decesari, M. C. Facchini, W. Birmili, A. Sonntag, A. Wiedensohler, J. Boulon, K. Sellegri, P. Laj, M. Gysel, N. Bukowiecki, E. Weingartner, G. Wehrle, A. Laaksonen, A. Hamed, J. Joutsensaari, T. Petäjä, V.-M. Kerminen, and M. Kulmala, EUCAARI ion spectrometer measurements at 12 European sites – analysis of new-particle formation events,
Atmos. Chem. Phys., 10, 7907–7927, doi:10.5194/acp-10-7907-2010, 2010


  

We present comprehensive results on continuous atmospheric cluster and particle measurements in the size range 

1–42 nm within the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) project. We focused on characterizing the spatial and temporal variation of new particle formation events and relevant particle formation parameters across Europe. Different types of air ion and cluster mobility spectrometers were deployed at 12 field sites across Europe from March 2008 to May 2009. The measurements were conducted in a wide variety of environments, including coastal and continental locations as well as sites at different altitudes (both in the boundary layer and the free troposphere). New particle formation events were detected at all of the 12 field sites during the year-long measurement period. From the data, nucleation and growth rates of newly formed particles were determined for each environment. In a case of parallel ion and neutral cluster measurements, we could also estimate the relative contribution of ion-induced and neutral nucleation to  the total particle formation. The formation rates of charged particles at 2 nm accounted for 1–30% of the corresponding total particle formation rates. As a significant new result, we found out that the total particle formation rate varied much more between the different sites than the formation rate of charged particles. This work presents, so far, the most comprehensive effort to experimentally characterize nucleation and growth of atmospheric molecular clusters and nanoparticles at ground-based observation sites on a continental scale.

EUCAARI: European Integrated project on Aerosol Cloud Climate and Air Quality interactions EUCAARI: European Integrated project on Aerosol Cloud Climate and Air Quality interactions

Date added: 04/28/2009
Date modified: 11/01/2009
Filesize: 670.53 kB

Kulmala, M., A. Asmi, H. K. Lappalainen, K. S. Carslaw, U. P¨oschl, U. Baltensperger, Ø. Hov, J.-L. Brenquier, S. N. Pandis, M. C. Facchini, H.-C. Hansson, A. Wiedensohler, and C. D. O’Dowd. Introduction: European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) – Integrating aerosol research from nano to global scales, Atmos. Chem. & Phys., 9, 2825-2841, 2009.


Abstract

 

The European Aerosol Cloud Climate and Air Quality Interactions project EUCAARI is an EU Research
Framework 6 integrated project focusing on understanding the interactions of climate and air pollution. EUCAARI works in an integrative and multidisciplinary way from nano to global scale. EUCAARI brings together several leading European research groups, state-of-the-art infrastructure and some key scientists from third countries to investigate the role of aerosol on climate and air quality. Altogether 48 partners from 25 countries are participating in EUCAARI.  
During the first 16 months EUCAARI has built operational systems, e.g. established pan-European measurement network for Lagrangian studies and four stations in developing countries. Also an improved understanding of nanoscale processes (like nucleation) has been implemented in global models. Here we present the research methods, organisation, operations and first results of EUCAARI.

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

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

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


Abstract


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

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

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

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


Abstract


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

European greenhouse gas emissions estimated from continuous atmospheric measurements and radon 222 at Mace Head, Ireland European greenhouse gas emissions estimated from continuous atmospheric measurements and radon 222 at Mace Head, Ireland

Date added: 07/31/2000
Date modified: 07/24/2009
Filesize: 1.37 MB

Biraud, S., Ciais, P., Ramonet, M., Simmonds, P.G., Kazan, V., Monfray, P., O'Doherty, S., Spain, T.G., and Jennings, S.G. (2000).European greenhouse gas emissions estimated from continuous atmospheric measurements and Radon 222 at Mace Head, Ireland. J. Geophys. Res., 105, 1351-1366.


Abstract


Flux estimates of CO2, CH4, N2O. and CFCs over western Europe have been inferred from continuous atmospheric records of these species at the atmospheric research station of Mace Head, Ireland. We use radon (222Rn) which has a fairly uniform source over continents as a reference compound to estimate unknown sources of other species. The correlation between each species and 222Rn is calculated for a suite of synoptic events that have been selected in the Mace Head record over the period 1996/97. In the following, we describe the method and its uncertainties, and we establish data selection criteria that minimize the influence of local sources over Ireland, in the vicinity of the station, in order to select synoptic events originating from western Europe. We estimate western European flux densities of 45-30 103 kg C km-2 month-1 during wintertime for CO2, of 4.8-3.5 10 kg CH4 km-2 yr-1, 475-330 kg N2O km-2 yr-1. 2.5-1.8 kg CFC-11 km-2 yr-1 for CFC-11, and 4.2-2.9 kg CFC-12 km-2 yr-1 for CFC-12. Our estimates are independent, although in good agreement with those produced by inventories, except for CFC- 1 where our estimate is much lower than the inventory.

European source strengths and Northern Hemisphere baseline concentrations of radiatively active European source strengths and Northern Hemisphere baseline concentrations of radiatively active

Date added: 08/07/1998
Date modified: 07/24/2009
Filesize: 339.88 kB

Derwent, RG, Simmonds, PG, O'Doherty, S, et al , European source strengths and northern hemisphere baseline concentrations of radiatively active trace gases at Mace Head, Ireland, ATMOS ENVIRON, 1998, Vol: 32, Pages: 3703 - 3715, ISSN: 1352-2310


Abstract


Greenhouse gas measurements have been made continuously with high frequency and precision at the remote baseline monitoring station at Mace Head on the Atlantic Ocean coastline of Ireland since 1987. By using three independent methods, the two-hourly observations have been sorted by air mass origins into those from unpolluted' or Northern Hemisphere baseline air masses and those from polluted European air masses. Northern Hemisphere baseline methane, nitrous oxide and carbon dioxide concentrations have risen throughout the 10 year period and their respective mid-1996 levels are the highest mid-year levels recorded so far. For ozone, the mid-1996 annual mean concentrations was within 0.1 ppb of the highest mid-year level. The elevated greenhouse gas concentrations found in polluted air masses provide clear evidence for the presence of substantial emission sources in Europe. Using a simple climatological long-range transport model and a sophisticated Lagrangian dispersion model, it has been possible to estimate the magnitudes of the greenhouse gas emissions required to support the observations. Estimates of European source strengths of methane, nitrous oxide, carbon monoxide and halocarbons agree well with the available emission inventories. Using the Mace Head observations, significant additional contributions to global climate change have been identified from the trace gases: methane, nitrous oxide and tropospheric ozone, over and above that driven by carbon dioxide. The radiative forcing consequences of a range of HCFCs and HFCs will only become of significance should their emissions grow to become comparable with those of the CFCs that they have replaced.

 

Evaluating measurements new particle concentrations, source rates and spatial scales during .. Evaluating measurements new particle concentrations, source rates and spatial scales during ..

Date added: 07/31/2002
Date modified: 07/24/2009
Filesize: 863.78 kB

Kaarle Hameri , Colin O'Dowd, Claudia Hoell, Evaluating measurements new particle concentrations, source rates and spatial scales during coastal nucleation events using condensation particle counters. ,JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 107, NO. D19, 8101, doi:10.1029/2001JD000411, 2002


Abstract


Condensation particle counters (CPCs), used to examine particle production in the coastal environment, are evaluated for their ability to differentiate ultrafine sizes between 3 and 10 nm, along with their ability to count high total particle number concentrations encountered during coastal nucleation events. Four ultrafine particles counters, with a 3 nm detection limit, were deployed in a spatial array comprising a triangular distribution with nodes approximately 100 m apart (two at 3 m height, one at 10 m). A fourth node was deployed at 20 m. The 10 m and 20 m node comprised additional CPCs with detection limits of 5 and 10 nm. Size cutoff efficiency calibrations were performed in the field, and all CPCs were found to be within the manufacturer's specifications. During the nucleation events it was found that peak particle concentrations of the order of 180,000 cm−3 were encountered, and as a result, coincidence calibrations were also performed in the laboratory. It was found that, at concentrations over 100,000 cm−3, the CPCs significantly underestimated the true concentrations by a factor of about 5–6. Total particle concentrations were also measured using a 30-times dilution system and an ultrafine CPC, along with integrated total concentration derived from the ultrafine Differential Mobility Particle Sizer (DMPS). Comparison of laboratory-derived corrections for coincidence and both the diluted CPC total concentrations and DMPS concentrations revealed very good agreement and confirmed that peak particle concentrations during coastal nucleation bursts result in new particle concentrations as high as 1.2 × 106 cm−3. The DMPS total concentration was somewhat lower than the diluted CPC concentration, suggesting that the recommended method of measuring such high concentrations is to dilute the sample significantly. The lower concentrations from the DMPS are partially due to the 10 min integration time being insufficient to resolve peaks seen by the CPC operated at 1 Hz. Taking the corrected concentrations in account, 3 nm particle source rates were calculated to be >105 cm−3 s−1. The spatial array of CPCs revealed that within the general coastal nucleation plume, there are numerous microplumes with spatial scales of the order of 10–100 m when sampling is conducted near the source region. Further from the source region these microplumes merge into the general coastal plume.

Evaluation of a Lagrangian box model using field measurements from EASE (Eastern Atlantic Summe Evaluation of a Lagrangian box model using field measurements from EASE (Eastern Atlantic Summe

Date added: 08/07/2000
Date modified: 07/24/2009
Filesize: 696.19 kB

Evans, M.J., D.E. Shallcross, K.S. Law, J.O.F. Wild, P.G. Simmonds, T.G. Spain, P. Berrisford, J. Methven, A.C. Lewis, J.B. McQuaid, M.J. Pilling, B.J. Bandy, S.A. Penkett, and J.A. Pyle, Evaluation of a Lagrangian box model using field measurements from EASE 1996, Atmos. Environ., 34, 3843-3863, 2000, (Ser. No. ACP048).


Abstract


The Cambridge Tropospheric Trajectory model of Chemistry and Transport (CiTTyCAT), a Lagrangian chemistry model, has been evaluated using atmospheric chemical measurements collected during the East Atlantic Summer Experiment 1996 (EASE '96). This field campaign was part of the UK Natural Environment Research Council's (NERC) Atmospheric Chemistry Studies in the Oceanic Environment (ACSOE) programme, conducted at Mace Head, Republic of Ireland, during July and August 1996. The model includes a description of gas-phase tropospheric chemistry, and simple parameterisations for surface deposition, mixing from the free troposphere and emissions. The model generally compares well with the measurements and is used to study the production and loss of O3 under a variety of conditions. The mean difference between the hourly O3 concentrations calculated by the model and those measured is 0.6 ppbv with a standard deviation of 8.7 ppbv. Three specific air-flow regimes were identified during the campaign - westerly, anticyclonic (easterly) and south westerly. The westerly flow is typical of background conditions for Mace Head. However, on some occasions there was evidence of long-range transport of pollutants from North America. In periods of anticyclonic flow, air parcels had collected emissions of NOx and VOCs immediately before arriving at Mace Head, leading to O3 production. The level of calculated O3 depends critically on the precise details of the trajectory, and hence on the emissions into the air parcel. In several periods of south westerly flow, low concentrations of O3 were measured which were consistent with deposition and photochemical destruction inside the tropical marine boundary layer.

 

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

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

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


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

 

Evaluation of mixing height retrievals from automatic profiling lidars and ceilometers in view of fu Evaluation of mixing height retrievals from automatic profiling lidars and ceilometers in view of fu

Date added: 08/12/2011
Date modified: 08/12/2011
Filesize: 1.59 MB

Haeffelin, M.,  F. Angelini, Y. Morille, G. Martucci, S. Frey, G. P. Gobbi, S. Lolli, C. D. O'Dowd, L. Sauvage, I. Xueref-Rémy, B. Wastine,  Evaluation of mixing height retrievals from automatic profiling lidars and ceilometers in view of future integrated networks in Europe, Bound. Lay. Met., DOI 10.1007/s10546-011-9643-z, 2011

 

The determination of the depth of daytime and nighttime mixing layers mustbe known very accurately to relate boundary-layer concentrations of gases or particles to upstream fluxes. The mixing-height is parametrized in numerical weather prediction models, so improving the determination of the mixing height will improve the quality of the estimated gas and particle budgets. Datasets of mixing-height diurnal cycles with high temporal and spatial resolutions are sought by various end users. Lidars and ceilometers provide vertical profiles of backscatter from aerosol particles. As aerosols are predominantly concentrated in the mixing layer, lidar backscatter profiles can be used to trace the depth of the mixing layer. Large numbers of automatic profiling lidars and ceilometers are deployed by meteorological services and other agencies in several European countries providing systems to monitor  the mixing height on temporal and spatial scales of unprecedented density. We investigate limitations and capabilities of existing mixing height retrieval algorithms by applying five different retrieval techniques to three different lidars and ceilometers deployed during two 1-month campaigns.We studied three important steps in the mixing height retrieval process, namely the lidar/ceilometer pre-processing to reach sufficient signal-to-noise ratio, gradient detection techniques to find the significant aerosol gradients, and finally quality control and layer attribution to identify the actual mixing height from multiple possible layer detections. We found that layer attribution is by far the most uncertain step. We tested different gradient detection techniques, and found no evidence that the first derivative, wavelet transform, and two-dimensional derivative techniques have different skills to detect one or multiple significant aerosol gradients from lidar and ceilometer attenuated backscatter. However, our study shows that, when mixing height retrievals from a ultraviolet lidar and a near-infrared ceilometer agreed, they were 25–40% more likely to agree with an independent radiosonde mixing height retrieval than when each lidar or ceilometer was used alone. Furthermore, we point to directions that may assist the layer attribution step, for instance using commonly available surface measurements of radiation and temperature to derive surface sensible heat fluxes as a proxy for the intensity of convective mixing. It is a worthwhile effort to pursue such studies so that within a few years automatic profiling lidar and ceilometer networks can be utilized efficiently to monitor mixing heights at the European scale. 

Evasion of mercury from coastal and open waters of the Atlantic Ocean and the Mediterranean Sea Evasion of mercury from coastal and open waters of the Atlantic Ocean and the Mediterranean Sea

Date added: 08/07/2003
Date modified: 07/24/2009
Filesize: 240.1 kB

Gardfeldt, K., Sommar, J., Ferrara, R., Ceccarini, C., Lanzillotta, E., Munthe, J., Wangberg, I., Lindqvist, O., Pirrone N., Sprovieri, F., Pesenti, E. (2003)   Evasion of mercury from coastal and open waters of the Atlantic Ocean and the Mediterranean Sea. Atmospheric Environment. Vol. 37-S1, 73-84.


Abstract


Dissolved gaseous mercury (DGM) was measured in coastal Atlantic seawater and in the Mediterranean Sea. The Atlantic measurements were performed during September 1999 at the Mace Head Atmospheric Research Station, situated on the Irish west coast. The measurements in the Mediterranean Sea were made along a 6000 km cruise path from 14 July to 9 August 2000 in the framework of the Med-Oceanor project. Total gaseous mercury (TGM) concentrations in air were continuously measured with a 5 min time resolution using an automated mercury analyser (Tekran 2537A) during both expeditions. Paired TGM and DGM samples from all campaigns showed that the surface water was supersaturated with elemental mercury. The mercury evasion was estimated using a gas exchange model (J. Geophys. Res. 97 (1992) 7373), which uses salinity, wind speed and water temperature as independent parameters. The predicted average mercury evasion from the coastal Atlantic water was 2.7 ng m-2h-1 implying that the concentration of TGM in the Atlantic air is enhanced by mercury evasion from the sea. Measurements in different regions of the Mediterranean Sea showed spatial variations in DGM concentrations. The highest DGM concentration (∼90 pg l-1) was observed at a location in the Strait of Sicily (37° 16N 11° 52E). The mercury evasion in the eastern sector of the Mediterranean Sea (area: 32-36°N, 17-28 E) was generally higher (7.9 ng m-2h-1) than that observed in the Tyrrhenian Sea (4.2 ng m-2h-1) or in the western sector (2.5 ng m-2h-1) (areas: 38-42°N, 8-13°E and 38-41°N, 7-8°E, respectively). Estimations of mercury evasion were also made at Mediterranean coastal sites using a dynamic chamber technique. In addition, a newly developed method making continuous in situ DGM measurements possible was tested.

 

Evidence for Substantial Variations of Atmospheric Hydroxyl Radicals in the Past Two Decades Evidence for Substantial Variations of Atmospheric Hydroxyl Radicals in the Past Two Decades

Date added: 08/01/2001
Date modified: 07/01/2009
Filesize: 1.28 MB

Prinn, R. G.; Huang, J.; Weiss, R. F.; Cunnold, D. M.; Fraser, P. J.; Simmonds, P. G.; McCulloch, A.; Harth, C.; Salameh, P.; O'Doherty, S.; Wang, R. H. J.; Porter, L.; Miller, B. R.,Evidence for Substantial Variations of Atmospheric Hydroxyl Radicals in the Past Two Decades, Science, Volume 292, Issue 5523, pp. 1882-1888 (2001).


Abstract


The hydroxyl radical (OH) is the dominant oxidizing chemical in the atmosphere. It destroys most air pollutants and many gases involved in ozone depletion and the greenhouse effect. Global measurements of 1,1,1-trichloroethane (CH3CCl3, methyl chloroform) provide an accurate method for determining the global and hemispheric behavior of OH. Measurements show that CH3CCl3 levels rose steadily from 1978 to reach a maximum in 1992 and then decreased rapidly to levels in 2000 that were lower than the levels when measurements began in 1978. Analysis of these observations shows that global OH levels were growing between 1978 and 1988, but the growth rate was decreasing at a rate of 0.23 +/- 0.18% year-2, so that OH levels began declining after 1988. Overall, the global average OH trend between 1978 and 2000 was -0.64 +/- 0.60% year-1. These variations imply important and unexpected gaps in current understanding of the capability of the atmosphere to cleanse itself.

Evidence of a natural marine source of oxalic acid and a possible link to glyoxal Evidence of a natural marine source of oxalic acid and a possible link to glyoxal

Date added: 03/14/2013
Date modified: 03/14/2013
Filesize: 410.96 kB
Rinaldi, Matteo, Stefano Decesari, Claudio Carbone, Emanuela Finessi, Sandro Fuzzi, Darius Ceburnis, Colin D. O’Dowd, Jean Sciare, John P. Burrows, Mihalis Vrekoussis, Barbara Ervens, Kostas Tsigaridis, and Maria Cristina Facchini, Evidence of a natural marine source of oxalic acid and a possible link to glyoxal, J. Geophys. Res., 116, D162,04, 12 PP., 2011, doi:10.1029/2011JD015659, 2011 __________________________________________________ Abstract. This paper presents results supporting the existence of a natural source of oxalic acid over the oceans. Oxalate was detected in “clean‐sector” marine aerosol samples at Mace Head (Ireland) (53°20’N, 9°54′W) during 2006, and at Amsterdam Island (37°48′S, 77°34′E) from 2003 to 2007, in concentrations ranging from 2.7 to 39 ng m−3 and from 0.31 to 17 ng m−3, respectively. The oxalate concentration showed a clear seasonal trend at both sites, with maxima in spring‐summer and minima in fall‐winter, being consistent with other marine biogenic aerosol components (e.g., methanesulfonic acid, non‐sea‐salt sulfate, and aliphatic amines). The observed oxalate was distributed along the whole aerosol size spectrum, with both a submicrometer and a supermicrometer mode, unlike the dominant submicrometer mode encountered in many polluted environments. Given its mass size distribution, the results suggest that over remote oceanic regions oxalate is produced through a combination of different formation processes. It is proposed that the cloud‐mediated oxidation of gaseous glyoxal, recently detected over remote oceanic regions, may be an important source of submicrometer oxalate in the marine boundary layer. Supporting this hypothesis, satellite‐retrieved glyoxal column concentrations over the two sampling sites exhibited the same seasonal concentration trend of oxalate. Furthermore, chemical box model simulations showed that the observed submicrometer oxalate concentrations were consistent with the in‐cloud oxidation of typical marine air glyoxal mixing ratios, as retrieved by satellite measurements, at both sites.

Evolution of the aerosol, cloud and boundary layer dynamic and ACE2 Evolution of the aerosol, cloud and boundary layer dynamic and ACE2

Date added: 08/06/2000
Date modified: 07/01/2009
Filesize: 1.38 MB

Osborne, S.M., D.W.Johnson, R. Wood, B.J. Bandy, M.O. Andreae, C.D. O'Dowd, P. Glantz, K.J. Noone, C. Gerbig, J. Rudolph, T.S. Bates, and P.K. Quinn, Evolution of the aerosol, cloud and boundary layer dynamic and thermodynamic characteristics during the second Lagrangian experiment of ACE-2, Tellus, 52B(2), 375-400, 2000, (Ser. No. ACP149).


Abstract


We present observations from the 2nd Aerosol Characterisation Experiment where over a 29-h period between 16–18 July 1997 a tagged column of air was followed by a fully instrumented aircraft. The Lagrangian framework this offered made it possible to measure the evolution of the aerosol size distribution, the cloud structure and microphysics, and the dynamic and thermodynamic structure of the marine boundary layer within a polluted airmass advecting off northwest Europe over the sub-tropical North Atlantic Ocean. The salient observations are presented and analysed. Processes responsible for the evolution are suggested, but quantification of their respective rates must be taken up by future modelling studies. Stratocumulus capped the boundary layer throughout the period that produced negligible washout of aerosol. This implies that the conversion of a continental to a maritime airmass within the cloud-capped sub-tropical marine boundary layer is not controlled by the drizzle process but by entrainment from the free troposphere. We find evidence of processing of aerosol particles by stratocumulus cloud, in particular by aqueous-phase reactions. The processing of the aerosol, realised by modification of the aerosol size distribution in the particle diameter range 0.1–0.5 mum, was complicated by rapid changes in boundary layer height and structure, and also by entrainment of both polluted and relatively clean aerosol from the free troposphere. The cloud microphysics was affected by these changes in the boundary layer aerosol through changes in the cloud condensation nuclei activation spectra. The cloud microphysics was also strongly affected by changes in the dynamics of the boundary layer which included variations (e.g., diurnal) in cloud thickness and an increase in vertical wind speed. Thermodynamic changes within the boundary layer included decoupling due to an increasing sea-surface temperature and a change in the subsidence rate in the free troposphere superimposed on diurnal decoupling. Hypotheses have been devised so that future modellers can focus their efforts to either validate or invalidate potentially important processes.

 

Experimental studies of the effect of rough surfaces and air speed on aerosol deposition in a test chamber Experimental studies of the effect of rough surfaces and air speed on aerosol deposition in a test chamber

Date added: 07/31/2002
Date modified: 07/01/2009
Filesize: 915.07 kB

Lai, A.C.K., Byrne and AJH Goddard. Experimental studies of the effect of rough surfaces and air speed on aerosol deposition in a test chamber. Aerosol Science and Technology, 36: 973-982, 2002.


Abstract

 

Understanding the fate of particles indoors is important for human health assessment because deposited particles, unless resuspended, cannot be inhaled. To complement studies in real buildings, where control of variables is often difficult, an experimental test chamber facility (8 m3) was designed to study particle deposition under well-stirred conditions using monodisperse tracer aerosol particles in the range of 0.7 to 5.4 mum. The use of neutron-activatable tracers facilitated simultaneous surface sampling and aerosol concentration decay measurements.

 

Aerosol deposition on both smooth surfaces and regular arrays of three-dimensional roughness elements under 3 different airflow speeds was investigated in the test chamber.It was expected that the texture of the chamber surface would significantly influence particle deposition, but some counterintuitive results were observed: under the lowest airflow condition and for the smallest particle size, particle deposition onto rough samples was found to be less than on the corresponding smooth surfaces.

 

The ratio of particle deposition on rough surfaces relative to smooth surfaces increased with particle size and magnitude of airflow. For the largest particle size and airflow speed, particle deposition on the rough surfaces exceeded that on the smooth surfaces by a factor of 3.

Experiments on water drop interactions Experiments on water drop interactions

Date added: 09/06/1977
Date modified: 08/06/2009
Filesize: 1.27 MB

Jennings, S.G. (1977)- Experiments on water drop interactions. Phys. Ed., 12, 381-385.


Abstract

 

A series of experiments is described which demonstrate the interactions of water drops. These experiments were used in a project with second year undergraduates and should be easy to adapt for school use. Photographic, stroboscopic and droplet stream formation techniques are used. Droplet-droplet collisions and collisions with plane and curved air-water interfaces are involved. It is considered that the experiments provide a good basis for the understanding of the relative roles of kinetic energy and surface energy in governing water droplet behaviour.

Explaining global surface aerosol number concentrations in terms of primary emissions and particle f Explaining global surface aerosol number concentrations in terms of primary emissions and particle f

Date added: 01/31/2011
Date modified: 01/31/2011
Filesize: 972.89 kB

Spracklen, D. V., K. S. Carslaw, J. Merikanto, G. W. Mann, S. Pickering, J. A. Ogren, B. Andrews, U. Baltensperger, E. Weingartner, M. Boy, M. Kulmala, H. Lihavainen, J. Hatakka, N. Mihalopoulos, G. Kouvarakis, S. G. Jennings, C. O’Dowd, W. Birmili, A. Wiedensohler, R. Weller, J. Gras, P. Laj, R. Griffin, B. Bonn, and B. Bandy, Explaining global surface aerosol concentrations in terms of primary emissions and particle formation, Atmos. Chem. Phys., 10, 4775–4793, doi:10.5194/acp-10-4775-2010, 2010


 

Abstract

 

We synthesised observations of total particle number (CN) concentration from 36 sites around the world. We found that annual mean CN concentrations are typically 300–2000 cm−3 in the marine boundary layer and free troposphere (FT) and 1000–10 000 cm−3 in the continental boundary layer (BL). Many sites exhibit pronounced seasonality with summer time concentrations a factor of 2–10 greater than wintertime concentrations. We used these CN obser-vations to evaluate primary and secondary sources of particle  number in a global aerosol microphysics model. We found that emissions of primary particles can reasonably reproduce the spatial pattern of observed CN concentration (R2=0.46) but fail to explain the observed seasonal cycle (R2=0.1). The modeled CN concentration in the FT was biased low (normalised mean bias, NMB=−88%) unless a secondary source of particles was included, for example from binary homogeneous nucleation of sulfuric acid and water (NMB=−25%). Simulated CN concentrations in the continental BL were also biased low (NMB=−74%) unless the number emission of anthropogenic primary particles was increased or a mechanism that results in particle formation in the BL was included. We ran a number of simulations where we included  an empirical BL nucleation mechanism either using the activation-type mechanism (nucleation rate, J , proportional to gas-phase sulfuric acid concentration to the power one) or kinetic-type mechanism (J proportional to sulfuric acid to the power two) with a range of nucleation coefficients. We found that the seasonal CN cycle observed at continental BL sites was better simulated by BL particle formation (R2=0.3) than by increasing the number emission from primary anthropogenic sources (R2=0.18). The nucleation constants that resulted in best overall match between model and observed CN concentrations were consistent with values derived in previous studies from detailed case studies at individual sites. In our model, kinetic and activation-type nucleation parameterizations gave similar agreement with observed monthly mean CN concentrations.

 

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

Date added: 08/07/2006
Date modified: 07/24/2009
Filesize: 645.4 kB

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


Abstract


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

Extinction and Liquid Water Content Measurements at CO2 Laser wavelengths Extinction and Liquid Water Content Measurements at CO2 Laser wavelengths

Date added: 07/31/1987
Date modified: 07/01/2009
Filesize: 601.9 kB

Nolan, P.F., and Jennings, S.G. (1987). - Extinction and liquid water content measurements at CO2 laser wavelengths. J. Atmos. and Oceanic Technol., 4, 391 - 400.


Abstract

 

Measurements have been made of both extinction coefficients in an evaporating laboratory cloud at wavelength λ = 10.591 μm using a CO2 laser, and of liquid water content (LWC) at the center of the cloud using a continuous filtration LWC device. Cloud uniformity has been promoted and monitored within the laboratory chamber. The measurements give an overall linear relation between extinction and liquid water content independent of droplet-size distribution in reasonably good agreement with the Chýlek prediction. The measurements show significantly better agreement with the Chýlek prediction for the narrower cloud drop-size distributions. The broader size distribution data show an underestimate in extinction compared to the Chýlek prediction, providing the first experimental evidence for the large radius limit (radius 12 μm) in use of the Chýlek relation.

Extinction and liquid water content of fog at visible wavelengths Extinction and liquid water content of fog at visible wavelengths

Date added: 07/31/1983
Date modified: 07/01/2009
Filesize: 2.27 MB

Jennings, S.G. (1983)- Extinction and liquid water content of fog at visible wavelengths. Appl. Opt., 22, 2514-2515.


Abstract


Field intercomparison of filter pack and impactor sampling for aerosol nitrate, ammonium, and s Field intercomparison of filter pack and impactor sampling for aerosol nitrate, ammonium, and s

Date added: 08/07/2004
Date modified: 07/24/2009
Filesize: 759.95 kB

Field Intercomparison of Filter Pack and Impactor Sampling for Aerosol Nitrate, Ammonium, and Sulphate at Coastal and Inland Sites, Z. Huang, R.M. Harrison, A.G. Allen, J.D. James, R.M. Tilling and J. Yin, Atmos. Res., 71, 215-232 (2004).


Abstract


An intercomparison has been performed on the coarse (>2.5 μm) and fine fraction (<2.5 μm) mass concentrations of particulate nitrate, ammonium, and sulphate determined simultaneously by filter pack and MOUDI samplers. Five intensive field campaigns have been carried out in summer and winter seasons, both at coastal sites (Mace Head, Ireland, and Tenerife, Spain) and at an inland site (University of Birmingham, West Midlands, UK). Comparison between particle sulphate measurements shows that sulphate measurements are the same with both filter pack and MOUDI, independent of sampling site or season. For both nitrate and ammonium, the MOUDI results are observed to be usually less than those from the filter pack, especially in the case of polluted air masses. During periods when the measured concentration products [NH3][HNO3] are low (<0.1 ppbv2), the ammonium concentrations obtained with the two samplers are matched very well with each other, but for nitrate, the filter pack system provides 15% higher mass concentrations than the MOUDI which are attributable to different inlet efficiencies. During more polluted periods, however, when there are high levels of gaseous ammonia and nitric acid in the atmosphere (with the measured concentration products [NH3][HNO3]>0.1 ppbv2), significantly negative sampling artefacts are observed for both nitrate and ammonium concentrations obtained with the impactor relative to the filter pack. Nevertheless, it is shown that both filter pack and MOUDI are capable of collecting ammonium nitrate from polluted air masses although the absolute efficiency is unknown. From the measurements obtained with the MOUDI in summertime at both coastal and inland sites, it is observed that about 64% of collected particle nitrate is present in the coarse (>2.5 μm) mode; but in wintertime, only about 29% of particle nitrate is found to reside in the coarse particles collected at the inland site. The lower efficiency of the MOUDI for ammonium nitrate relative to the Teflon filter is in marked contrast to the reported higher efficiency of the Berner impactor than the Teflon filter for sampling nitrate from polluted air.

 

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

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

Abstract


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

First experimental evidence of new particle formation from organic vapours over forests First experimental evidence of new particle formation from organic vapours over forests

Date added: 07/31/2002
Date modified: 07/01/2009
Filesize: 97.37 kB

O'Dowd, C.D. K. Hämeri, P. Aalto, and M. Kulmala, First experimental evidence of new particle formation from organic vapours over forests, Nature, 416, 497-498, 2002.


Abstract


Aerosol particles produced over forested areas may affect climate by acting as nuclei for cloud condensation, but their composition (and hence the chemical species that drive their production) remains an open question. Here we show, to our knowledge for the first time, that these newly formed particles (3–5 nm in diameter) are composed primarily of organic species, such as cis-pinonic acid and pinic acid, produced by oxidation of terpenes in organic vapours released from the canopy

Flood or Drought: How Do Aerosols Affect Precipitation? Flood or Drought: How Do Aerosols Affect Precipitation?

Date added: 09/12/2008
Date modified: 07/01/2009
Filesize: 1.93 MB

Flood or Drought: How Do Aerosols Affect Precipitation? Daniel Rosenfeld, Ulrike Lohmann, Graciela B. Raga, Colin D. O'Dowd, Markku Kulmala, Sandro Fuzzi, Anni Reissell, and Meinrat O. Andreae (5 September 2008) Science 321 (5894), 1309. [DOI: 10.1126/science.1160606]


Abstract


Aerosols serve as cloud condensation nuclei (CCN) and thus have a substantial effect on cloud properties and the initiation of precipitation. Large concentrations of human-made aerosols have been reported to both decrease and increase rainfall as a result of their radiative and CCN activities. At one extreme, pristine tropical clouds with low CCN concentrations rain out too quickly to mature into long-lived clouds. On the other hand, heavily polluted clouds evaporate much of their water before precipitation can occur, if they can form at all given the reduced surface heating resulting from the aerosol haze layer. We propose a conceptual model that explains this apparent dichotomy.

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