bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature and light dependence of the VOC emissions of Scots pine
Authors: Tarvainen V. , Hakola H. , Hellén H. , Bäck J. , Hari P. , Kulmala M.
Published: April 2010

Abstract. The volatile organic compound (VOC) emission rates of Scots pine (Pinus sylvestris L.) were measured from trees growing in a natural forest environment at two locations in Finland. The emission rate measurements were carried out using a dynamic flow through technique with samples collected on adsorbent tubes and analyzed using thermodesorption followed by a gas chromatograph with a mass-selective detector (GC-MS). The standard emission potentials (at 303.15 K and 1000 µmol photons m−2 s−1) were calculated for the measured compounds using nonlinear regression to fit the experimental data to temperature and light dependent emission algorithms. The observed total VOC emission rates varied between 21 and 874 ng/g(dw)*h and 268 and 1670 ng/g(dw)*h in southern and northern Finland, respectively. A clear seasonal cycle was detected with high emission rates in early spring, a decrease of the emissions in late spring and early summer, high emissions again in late summer, and a gradual decrease in autumn. The main emitted compounds were Δ3-carene (southern Finland) and α- and β-pinene (northern Finland), with approximate relative contributions of 60–70% and 60–85% of the total observed monoterpene emission rates, respectively. Sesquiterpene (β-caryophyllene) and 2-methyl-3-buten-2-ol (MBO) emissions were initiated in early summer at both sites. The observed MBO emission rates were between 1 and 3.5% of the total monoterpene emission rates. The sesquiterpene emission rates varied between 2 and 5% of the total monoterpene emission rates in southern Finland, but were high (40%) in northern Finland in spring. Most of the measured emission rates were found to be well described by the temperature dependent emission algorithm. The calculated standard emission potentials were high in spring and early summer, decreased somewhat in late summer, and were high again towards autumn. The experimental coefficient β ranged from 0.025 to 0.19 (average 0.10) in southern Finland, with strongest temperature dependence in spring and weakest in late summer. Only the emission rates of 1,8-cineole were found to be both light and temperature dependent. However, there were irregularities with the performance of the exponential temperature algorithm, and our results suggest that especially during the spring recovery period of the vegetation there may be several different processes contributing to the VOC emissions of Scots pine.
Heterogeneous conversion of NO2 and NO on HNO3 treated soot surfaces
Authors: Kleffmann J. , Wiesen P.
Published: April 2010

Abstract. In the present study, the heterogeneous conversion of nitrogen oxide (NO) and nitrogen dioxide (NO2) was studied at atmospheric humidity levels on flame soot surfaces, which were treated with gaseous nitric acid (HNO3). In addition, the heterogeneous reaction of HNO3 on soot was investigated at atmospheric humidity. For the treatment of soot by pure HNO3 only reversible uptake with a surface coverage of ~1–2×1014 HNO3 cm−2 was observed for HNO3 mixing ratios in the range 250–800 ppbv. Only for higher HNO3 mixing ratios of >800 ppbv the formation of NO and NO2 was observed. The results were not affected by the addition of NO. In none of the experiments with HNO3 the formation of nitrous acid (HONO) was observed. For HNO3 mixing ratios <600 ppbv the upper limit yields for HONO, NO2 and NO were found to be <0.2%, <0.5% and <1%, respectively. Compared to untreated soot, the product formation of the reaction of NO2 with soot was not significantly affected when the soot surface was treated with gaseous HNO3 prior to the experiment. Only for high surface coverage of HNO3 the formation of HONO was suppressed in the initial phase of the reaction, probably caused by the blocking of active sites by adsorbed HNO3. Under the assumption that the experimental findings for the used model flame soot can be extrapolated to atmospheric soot particles, the results show that the reactions of HNO3 and HNO3+NO on soot surfaces are unimportant for a "renoxification" of the atmosphere and do not represent an atmospheric HONO source. In addition, the integrated HONO yield of ca. 1014 cm−2 in the reaction of NO2 with soot is not significantly influenced by simulated atmospheric processing of the soot surface by HNO3, and is still too small to explain HONO formation in the atmosphere.
Climatological features of stratospheric streamers in the FUB-CMAM with increased horizontal resolution
Authors: Krüger K. , Langematz U. , Grenfell J. L. , Labitzke K.
Published: April 2010

Abstract. The purpose of this study is to investigate horizontal transport processes in the winter stratosphere using data with a high spatial and temporal resolution. For this reason the Freie Universität Berlin Climate Middle Atmosphere Model (FUB-CMAM) with its model top at 83 km altitude, increased horizontal resolution T42 and the semi-Lagrangian transport scheme for advecting passive tracers is used. A new result of this paper is the classification of specific transport phenomena within the stratosphere into tropical-subtropical streamer (e.g. Offermann et al., 1999) and polar vortex extrusions hereafter called polar vortex streamers. To investigate the role played by these large-scale structures on the inter-annual and seasonal variability of the observed negative ozone trend in northern mid-latitudes, the global occurrence of such streamers were calculated based on a 10-year model climatology, concentrating on the existence of the Arctic polar vortex. For the identification and counting of streamers, the new method of zonal anomaly was chosen, which in comparison to other methods produced the best result in this study. The analysis of the months October–May yielded a maximum occurrence of tropical-subtropical streamers during Arctic winter and spring in the middle and upper stratosphere. Synoptic maps revealed highest intensities in the subtropics over East Asia with a secondary maximum over the Atlantic in the northern hemisphere. Furthermore, tropical-subtropical streamers exhibited about a four times higher occurrence than polar vortex streamers, indicating that the subtropical barrier is more permeable than the polar vortex barrier (edge) in the model, which is in good correspondence with observations (e.g. Plumb, 2002; Neu et al., 2003). Interesting for the total ozone loss in mid-latitudes is the consideration of the lower stratosphere, where strongest ozone depletion is observed at polar latitudes (WMO, 2003). In this particular region the FUB-CMAM simulated a climatological maximum of 10% occurrence of tropical-subtropical streamers over East-Asia/West Pacific and the Atlantic during early- and mid-winter. The results of this paper demonstrate that the regular occurrence of stratospheric streamers e.g., large-scale mixing processes of tropical-subtropical and polar vortex air masses into mid-latitudes, could play a significant role on the strength and variability of the observed total ozone decrease at mid-latitudes and should not be neglected in future climate change studies.
Changes of daily surface ozone maxima in Switzerland in all seasons from 1992 to 2002 and discussion of summer 2003
Authors: Ordóñez C. , Mathis H. , Furger M. , Henne S. , Hüglin C. , Staehelin J. , Prévôt A. S. H.
Published: April 2010

Abstract. An Analysis of Covariance (ANCOVA) was used to derive the influence of the meteorological variability on the daily maximum ozone concentrations at 12 low-elevation sites north of the Alps in Switzerland during the four seasons in the 1992–2002 period. The afternoon temperature and the morning global radiation were the variables that accounted for most of the meteorological variability in summer and spring, while other variables that can be related to vertical mixing and dilution of primary pollutants (afternoon global radiation, wind speed, stability or day of the week) were more significant in winter. In addition, the number of days after a frontal passage was important to account for ozone build-up in summer and ozone destruction in winter. The statistical model proved to be a robust tool for reducing the impact of the meteorological variability on the ozone concentrations and further ozone trend assessment. On average the explained variance ranged from 60.7% in winter to 71.8% in autumn, and the year-to-year variability of the seasonal medians of daily ozone maxima was reduced by 85% in winter, 60% in summer, and 50% in autumn and spring after the meteorological adjustment. For most of the stations, except some in the region around Zürich, no significantly negative trends (at the 95% confidence level) of either daily O3 or Ox (O3+NO2) maxima were found in summer despite the significant reduction in the precursor emissions in Central Europe. The lower effect of the titration by NO as a consequence of the reduced emissions could partially explain the significantly positive O3 trends in the cold seasons (on average 0.68 ppb yr−1 in winter and 0.58 ppb yr−1 in autumn). The increase of Ox found for most stations in autumn (on average 0.23 ppb yr−1) and winter (on average 0.40 ppb yr−1) could be due to increasing European background ozone levels, in agreement with other studies. The statistical model was also able to explain the very high ozone concentrations in summer 2003, the warmest summer in Switzerland for at least ~150 years. On average, the measured daily ozone maximum was 15 ppb (nearly 29%) higher than in the reference period summer 1992–2002, corresponding to an excess of 5 standard deviations of the summer means of daily ozone maxima in that period.
Technical Note: The new comprehensive atmospheric chemistry module MECCA
Authors: Sander R. , Kerkweg R. , Jöckel P. , Lelieveld J.
Published: April 2010

Abstract. In this technical note we present the multi-purpose atmospheric chemistry model MECCA. Owing to its versatility and modular structure, it can be used for tropospheric as well as stratospheric chemistry calculations. Extending the code to other domains (e.g. mesospheric or oceanic chemistry) is easily possible. MECCA contains a comprehensive atmospheric reaction mechanism that currently includes: 1) the basic O3, CH4, HOx, and NOx, chemistry, 2) non-methane hydrocarbon (NMHC) chemistry, 3) halogen (Cl, Br, I) chemistry, and 4) sulfur chemistry. Not only gas-phase chemistry but also aqueous-phase and heterogeneous reactions are considered. Arbitrary subsets of the comprehensive mechanism can be selected according to the research objectives. The program code resulting from the chemical mechanism can easily be used in any kind of model, from a simple box model to a sophisticated global general circulation model.
Column ozone and aerosol optical properties retrieved from direct solar irradiance measurements during SOLVE II
Authors: Swartz W. H. , Yee J.-H. , Shetter R. E. , Hall S. R. , Lefer B. L. , Livingston J. M. , Russell P. B. , Browell E. V. , Avery M. A.
Published: April 2010

Abstract. Direct observation of the Sun at large solar zenith angles during the second SAGE III Ozone Loss and Validation Experiment (SOLVE II)/Validation of International Satellites and study of Ozone Loss (VINTERSOL) campaign by several instruments provided a rich dataset for the retrieval and analysis of line-of-sight column composition, intercomparison, and measurement validation. A flexible, multi-species spectral fitting technique is presented and applied to spectral solar irradiance measurements made by the NCAR Direct beam Irradiance Atmospheric Spectrometer (DIAS) on-board the NASA DC-8. The approach allows for the independent retrieval of O3, O2·O2, and aerosol optical properties, by constraining Rayleigh extinction. We examine the 19 January 2003 and 6 February 2003 flights and find very good agreement of O3 and O2·O2 retrievals with forward-modeling calculations, even at large solar zenith angles, where refraction is important. Intercomparisons of retrieved ozone and aerosol optical thickness with results from the Ames Airborne Tracking Sunphotometer (AATS-14) are summarized.
A practical demonstration on AMSU retrieval precision for upper tropospheric humidity by a non-linear multi-channel regression method
Authors: Jiménez C. , Eriksson P. , John V. O. , Buehler S. A.
Published: April 2010

Abstract. A neural network algorithm inverting selected channels from the AMSU-A and AMSU-B instruments was applied to retrieve layer averaged relative humidity. The neural network was trained with a global synthetic dataset representing clear-sky conditions. A precision of around 6% was obtained when retrieving global simulated radiances, the precision deteriorated less than 1% when real mid-latitude AMSU radiances were inverted and compared with co-located data from a radiosonde station. The 6% precision outperforms by 1% the reported precision estimate from a linear single-channel regression between radiance and weighting function averaged relative humidity, the more traditional approach to exploit AMSU data. Added advantages are not only a better precision; the AMSU-B humidity information is more optimally exploited by including temperature information from AMSU-A channels; and the layer averaged humidity is a more physical quantity than the weighted humidity, for comparison with other datasets. The training dataset proved adequate for inverting real radiances from a mid-latitude site, but it is limited by not considering the impact of clouds or surface emissivity changes, and further work is needed in this direction for further validation of the precision estimates.
Measurements of tropospheric NO2 with an airborne multi-axis DOAS instrument
Authors: Wang P. , Richter A. , Bruns M. , Rozanov V. V. , Burrows J. P. , Heue K.-P. , Wagner T. , Pundt I. , Platt U.
Published: April 2010

Abstract. The AMAXDOAS instrument is an airborne multi-axis DOAS instrument covering the spectral range from 300 to 600 nm. During one flight of the SCIAVALUE campaign on 19 March 2003, the AMAXDOAS onboard the DLR Falcon detected tropospheric NO2 over Europe under both cloudy and cloud free conditions. By combining the measurements in nadir and zenith direction, and analysing the spectra in the UV and the visible spectral region, information was derived on where the bulk of the observed NO2 was located. Vertical columns of up to 5.7×1016 molec cm-2 were observed close to Frankfurt, in good agreement with surface measurements of 16.4 ppb. On several occasions, strong tropospheric NO2 signals were also detected when flying above clouds. The ratio of zenith and nadir measurements indicates that the NO2 observed was located within the cloud, and assuming the same profile as for the cloud free situation the NO2 vertical column was estimated to be 5.0×1016 molec cm-2. The results are relevant for the retrieval of tropospheric NO2 columns from space-borne instruments in cloudy situations.
Balloon-borne Limb profiling of UV/vis skylight radiances, O3, NO2 and BrO: technical set-up and validation of the method
Authors: Weidner F. , Bösch H. , Bovensmann H. , Burrows J. P. , Butz A. , Camy-Peyret C. , Dorf M. , Gerilowski K. , Gurlit W. , Platt U. , von Friedeburg C. , Wagner T. , Pfeilsticker K.
Published: April 2010

Abstract. A novel light-weight, elevation scanning and absolutely calibrated UV/vis spectrometer and its application to balloon-borne Limb radiance and trace gas measurements is described. Its performance and the novel method of balloon-borne UV/vis Limb trace gas measurements has been tested against simultaneous observations of the same atmospheric parameters available from either (a) in-situ instrumentation (cf., by an electrochemical cell (ECC) ozone sonde also deployed aboard the gondola) or (b) trace gas profiles from inferred UV/vis/near IR solar occultation measurements performed on the same payload. The novel technique is also cross validated with radiative transfer modelling. Reasonable agreement is found (a) between measured and simulated Limb radiances and (b) inferred Limb O3, NO2 and BrO and otherwise measured profiles when properly accounting for all relevant atmospheric parameters (temperature T, pressure P, aerosol extinction, and major absorbers).
SCIAMACHY validation by aircraft remote measurements: design, execution, and first results of the SCIA-VALUE mission
Authors: Fix A. , Ehret G. , Flentje H. , Poberaj G. , Gottwald M. , Finkenzeller H. , Bremer H. , Bruns M. , Burrows J. P. , Kleinböhl A. , Küllmann H. , Kuttippurath J. , Richter A. , Wang P. , Heue K.-P. , Platt U. , Wagner T.
Published: April 2010

Abstract. For the first time three different remote sensing instruments – a sub-millimeter radiometer, a differential optical absorption spectrometer in the UV-visible spectral range, and a lidar – were deployed aboard DLR's meteorological research aircraft Falcon 20 to validate a large number of SCIAMACHY level 2 and off-line data products such as O3, NO2, N2O, BrO, OClO, H2O, aerosols, and clouds. Within two main validation campaigns of the SCIA-VALUE mission (SCIAMACHY VALidation and Utilization Experiment) extended latitudinal cross-sections stretching from polar regions to the tropics as well as longitudinal cross sections at polar latitudes at about 70° N and the equator have been generated. This contribution gives an overview over the campaigns performed and reports on the observation strategy for achieving the validation goals. We also emphasize the synergetic use of the novel set of aircraft instrumentation and the usefulness of this innovative suite of remote sensing instruments for satellite validation.
Cloud chemistry at the Puy de Dôme: variability and relationships with environmental factors
Authors: Marinoni A. , Laj P. , Sellegri K. , Mailhot G.
Published: April 2010

Abstract. The chemical composition of cloud water was investigated during the winter-spring months of 2001 and 2002 at the Puy de Dôme station (1465 m above sea level, 45°46'22'' N, 2°57'43' E) in an effort to characterize clouds in the continental free troposphere. Cloud droplets were sampled with single-stage cloud collectors (cut-off diameter approximately 7 μm) and analyzed for inorganic and organic ions, as well as total dissolved organic carbon. Results show a very large variability in chemical composition and total solute concentration of cloud droplets, ranging from a few mg l−1 to more than 150 mg l−1. Samplings can be classified in three different categories with respect to their total ionic content and relative chemical composition: background continental (BG, total solute content lower than 18 mg l−1), anthropogenic continental (ANT, total solute content from 18 to 50 mg l−1), and special events (SpE, total solute content higher than 50 mg l−1). The relative chemical composition shows an increase in anthropogenic-derived species (NO3−, SO42− and NH4+) from BG to SpE, and a decrease in dissolved organic compounds (ionic and non-ionic) that are associated with the anthropogenic character of air masses. We observed a high contribution of solute in cloud water derived from the dissolution of gas phase species in all cloud events. This was evident from large solute fractions of nitrate, ammonium and mono-carboxylic acids in cloud water, relative to their abundance in the aerosol phase. The comparison between droplet and aerosol composition clearly shows the limited ability of organic aerosols to act as cloud condensation nuclei. The strong contribution of gas-phase species limits the establishment of direct relationships between cloud water solute concentration and LWC that are expected from nucleation scavenging.
Emission scenarios for air quality management and applications at local and regional scales including the effects of the future European emission regulation (2015) for the upper Rhine valley
Authors: Ponche J.-L. , Vinuesa J.-F.
Published: April 2010

Abstract. Air quality modeling associated with emission scenarios has become an important tool for air quality management. The set-up of realistic emission scenarios requires accurate emission inventories including the whole methodology used to calculate the emissions. This means a good description of the source characteristics including a detailed composition of the emitted fluxes. Two main approaches are used. The so-called bottom-up approach that relies on the modification of the characteristics of the sources and the top-down approach whose goal is generally to reach standard pollutant concentration levels. This paper is aimed at providing a general methodology for the elaboration of such emission scenarios and giving examples of applications at local and regional scales for air quality management. The first example concerns the impact of the installation of the urban tramway in place of the road traffic in the old centre of Strasbourg. The second example deals with the use of oxygenated and reformulated car fuels on local (Strasbourg urban area) and regional (upper Rhine valley) scales. Finally, we analyze in detail the impacts of the incoming European emission regulation for 2015 on the air quality of the upper Rhine valley.
A curved multi-component aerosol hygroscopicity model framework: 2 – Including organics
Authors: Topping D. O. , McFiggans G. B. , Coe H.
Published: April 2010

Abstract. This paper describes the inclusion of organic particulate material within the Aerosol Diameter Dependent Equilibrium Model (ADDEM) framework described in the companion paper applied to inorganic aerosol components. The performance of ADDEM is analysed in terms of its capability to reproduce the behaviour of various organic and mixed inorganic/organic systems using recently published bulk data. Within the modelling architecture already described two separate thermodynamic models are coupled in an additive approach and combined with a method for solving the Köhler equation in order to develop a tool for predicting the water content associated with an aerosol of known inorganic/organic composition and dry size. For development of the organic module, the widely used group contribution method UNIFAC is employed to explicitly deal with the non-ideality in solution. The UNIFAC predictions for components of atmospheric importance were improved considerably by using revised interaction parameters derived from electro-dynamic balance studies. Using such parameters, the model was found to adequately describe mixed systems including 5–6 dicarboxylic acids, down to low relative humidity conditions. The additive approach for modelling mixed inorganic/organic systems worked well for a variety of mixtures. As expected, deviations between predicted and measured data increase with increasing concentration. Available surface tension models, used in evaluating the Kelvin term, were found to reproduce measured data with varying success. Deviations from experimental data increased with increased organic compound complexity. For components only slightly soluble in water, significant deviations from measured surface tension depression behaviour were predicted with both model formalisms tested. A Sensitivity analysis showed that such variation is likely to lead to predicted growth factors within the measurement uncertainty for growth factor taken in the sub-saturated regime. Greater sensitivity was found for the value of dry density used in the assumed form of the dried out aerosol. Comparison with a coupled thermodynamic approach showed that assumed values for interactions parameters may lead to erroneous results where a simple additive approach may provide more accurate results. However, where available, the use of coupled thermodynamics can better reproduce measured behaviour. Further work (and laboratory data) is required to assess whether this difference lies within the experimental uncertainty of observed hygroscopic behaviour for a variety of systems.
Direct evidence for coastal iodine particles from Laminaria macroalgae – linkage to emissions of molecular iodine
Authors: McFiggans G. , Coe H. , Burgess R. , Allan J. , Cubison M. , Rami Alfarra M. , Saunders R. , Saiz-Lopez A. , Plane J. M. C. , Wevill D. , Carpenter L. , Rickard A. R. , Monks P. S.
Published: April 2010

Abstract. Renewal of ultrafine aerosols in the marine boundary layer may lead to repopulation of the marine distribution and ultimately determine the concentration of cloud condensation nuclei (CCN). Thus the formation of nanometre-scale particles can lead to enhanced scattering of incoming radiation and a net cooling of the atmosphere. The recent demonstration of the chamber formation of new particles from the photolytic production of condensable iodine-containing compounds from diiodomethane (CH2I2), (O'Dowd et al., 2002; Kolb, 2002; Jimenez et al., 2003a; Burkholder and Ravishankara, 2003), provides an additional mechanism to the gas-to-particle conversion of sulphuric acid formed in the photo-oxidation of dimethylsulphide for marine aerosol repopulation. CH2I2 is emitted from seaweeds (Carpenter et al., 1999, 2000) and has been suggested as an initiator of particle formation. We demonstrate here for the first time that ultrafine iodine-containing particles are produced by intertidal macroalgae exposed to ambient levels of ozone. The particle composition is very similar both to those formed in the chamber photo-oxidation of diiodomethane and in the oxidation of molecular iodine by ozone. The particles formed in all three systems are similarly aspherical and behave alike when exposed to increased humidity environments. Direct coastal boundary layer observations of molecular iodine, ultrafine particle production and iodocarbons are reported. Using a newly measured molecular iodine photolysis rate, it is shown that, if atomic iodine is involved in the observed particle bursts, it is of the order of at least 1000 times more likely to result from molecular iodine photolysis than diiodomethane photolysis. A hypothesis for molecular iodine release from intertidal macroalgae is presented and the potential importance of macroalgal iodine particles in their contribution to CCN and global radiative forcing are discussed.
Implementation issues in chemistry and transport models
Authors: Strahan S. E. , Polansky B. C.
Published: April 2010

Abstract. Offline chemistry and transport models (CTMs) are versatile tools for studying composition and climate issues requiring multi-decadal simulations. They are computationally fast compared to coupled chemistry climate models, making them well-suited for integrating sensitivity experiments necessary for understanding model performance and interpreting results. The archived meteorological fields used by CTMs can be implemented with lower horizontal or vertical resolution than the original meteorological fields in order to shorten integration time, but the effects of these shortcuts on transport processes must be understood if the CTM is to have credibility. In this paper we present a series of CTM experiments, each differing from another by a single feature of the implementation. Transport effects arising from changes in resolution and model lid height are evaluated using process-oriented diagnostics that intercompare CH4, O3, and age tracer carried in the simulations. Some of the diagnostics used are derived from observations and are shown as a reality check for the model. Processes evaluated include the tropical ascent, tropical-midlatitude exchange, the poleward circulation in the upper stratosphere, and the development of the Antarctic vortex. We find that faithful representation of stratospheric transport in this CTM using Lin and Rood advection is possible with a full mesosphere, ~1 km resolution in the lower stratosphere, and relatively low vertical resolution (>4 km spacing) in the middle stratosphere and above, but lowering the lid from the upper to lower mesosphere leads to less realistic constituent distributions in the upper stratosphere. Ultimately, this affects the polar lower stratosphere, but the effects are greater for the Antarctic than the Arctic. The fidelity of lower stratospheric transport requires realistic tropical and high latitude mixing barriers which are produced at 2°×2.5°, but not lower resolution. At 2°×2.5° resolution, the CTM produces a vortex capable of isolating perturbed chemistry (e.g. high Cly and low NOy) required for simulating polar ozone loss.
Stratospheric intrusions induced by a Rossby Wave breaking and its interaction with the subtropical jet during PICO3 campaign
Authors: Carré A. , Ravetta F. , Cammas J.-P. , Mascart P. , Duron J. , Ancellet G. , Lambert D.
Published: April 2010

Abstract. This study documents several processes of stratosphere-troposphere transport (STT) in the subtropical region. A case study of the interaction between a Rossby Wave breaking over the Canary Islands and a subtropical vortex core situated further south is analysed with ozone airborne measurements (in-situ and Lidar). The investigation is conducted using a Reverse Domain Filling technique to reconstruct high-resolution potential vorticity fields with a Lagrangian approach and with simulations of a mesoscale model. Results show irreversible STT associated with tropopause folding, Rossby Wave Breaking and the filamentation of the subtropical vortex core.
The heterogeneous chemical kinetics of N2O5 on CaCO3 and other atmospheric mineral dust surrogates
Authors: Karagulian F. , Santschi C. , Rossi M. J.
Published: April 2010

Abstract. Uptake experiments of N2O5 on several mineral dust powder samples were carried out under continuous molecular flow conditions at 298±2 K. At [N2O5]0=(4.0±1.0)×1011 cm−3 we have found γss values ranging from (3.5±1.1)×10−2 for CaCO3 to (0.20±0.05) for Saharan Dust with γss decreasing as [N2O5]0 increased. We have observed delayed production of HNO3 upon uptake of N2O5 for every investigated sample owing to hydrolysis of N2O5 with surface-adsorbed H2O. At high and low [N2O5] Arizona Test Dust and Kaolinite turned out to be the samples to produce the largest amount of gas phase HNO3 with respect to N2O5 taken up. In contrast, the yield of HNO3 for Saharan Dust and CaCO3 are lower. On CaCO3 the disappearance of N2O5 was also accompanied by the formation of CO2. For CaCO3 sample masses ranging from 0.33 to 2.0 g, the yield of CO2 was approximately 42–50% with respect to the total number of N2O5 molecules taken up. The reaction of N2O5 with mineral dust and the subsequent production of gas phase HNO3 leads to a decrease in [NOx] which may have a significant effect on global ozone.
Studies of aerosol at a coastal site using two aerosol mass spectrometry instruments and identification of biogenic particle types
Authors: Dall’Osto M. , Harrison R. M. , Furutani H. , Prather K. A. , Coe H. , Allan J. D.
Published: April 2010

Abstract. During August 2004 an Aerosol Time-of-Flight Mass Spectrometer (TSI ATOFMS Model 3800-100) and an Aerodyne Aerosol Mass Spectrometer (AMS) were deployed at Mace Head during the NAMBLEX campaign. Single particle data (size, positive and negative mass spectra) from the ATOFMS were imported into ART 2a, a neural network algorithm, which assigns individual particles to clusters on the basis of their mass spectral similarities. Results are very consistent with previous time consuming manual classifications (Dall'Osto et al., 2004). Three broad classes were found: sea-salt, dust and carbon-containing particles, with a number of sub-classes within each. The Aerodyne (AMS) instrument was also used during NAMBLEX, providing online, real time measurements of the mass of non-refractory components of aerosol particles as function of their size. The ATOFMS detected a type of particle not identified in our earlier analysis, with a strong signal at m/z 24, likely due to magnesium. This type of particle was detected during the same periods as pure unreacted sea salt particles and is thought to be biogenic, originating from the sea surface. AMS data are consistent with this interpretation, showing an additional organic peak in the corresponding size range at times when the Mg-rich particles are detected. The work shows the ATOFMS and AMS to be largely complementary, and to provide a powerful instrumental combination in studies of atmospheric chemistry.
Distinct wind convergence patterns due to thermal and momentum forcing of the low level jet into the Mexico City basin
Authors: de Foy B. , Clappier A. , Molina L. T. , Molina M. J.
Published: April 2010

Abstract. Mexico City lies in a high altitude basin where air quality and pollutant fate is strongly influenced by local winds. The combination of high terrain with weak synoptic forcing leads to weak and variable winds with complex circulation patterns. A low level jet entering the basin in the afternoon leads to very different wind convergence lines over the city depending on the meteorological conditions. Surface and upper-air meteorological observations are analysed during the MCMA-2003 field campaign to establish the meteorological conditions and obtain an index of the strength and timing of the jet. A mesoscale meteorological model (MM5) is used in combination with high-resolution satellite data for the land surface parameters and soil moisture maps derived from diurnal ground temperature range. A simple method to map the lines of wind convergence both in the basin and on the regional scale is used to show the different convergence patterns according to episode types. The low level jet is found to occur on most days of the campaign and is primarily due to thermal forcing which is very similar from day to day. Momentum mixing from winds aloft into the surface layer is much more variable and can determine both the strength of the jet and the pattern of the convergence zones. Northerly flows aloft lead to a weak jet with an east-west convergence line that progresses northwards in the late afternoon and early evening. Westerlies aloft lead to stronger jets and a north-south convergence line through the middle of the basin starting in the early afternoon. Improved understanding of basin meteorology will lead to better air quality forecasts for the city and better understanding of the chemical regimes in the urban atmosphere.
Isoprene oxidation products are a significant atmospheric aerosol component
Authors: Matsunaga S. N. , Wiedinmyer C. , Guenther A. B. , Orlando J. J. , Karl T. , Toohey D. W. , Greenberg J. P. , Kajii Y.
Published: April 2010

Abstract. Glycolaldehyde, hydroxyacetone, and methylglyoxal, which are known isoprene oxidation products, were collected during two field experiments using an annular denuder sampling system and compared to a model calculation. The compounds in gas and aerosol phases were determined during both experiments. Global variation and distribution of the aerosol mass contribution of the compounds were predicted using the measurements, the box model results, and gas-phase concentrations and humidity simulated by a global 3-D model. Here we report the estimates of a global annual contribution of 35 (10–120) Tg of aerosol organic matter from isoprene.
Large eddy simulation of urban features for Copenhagen metropolitan area
Authors: Mahura A. , Leroyer S. , Mestayer P. , Calmet I. , Dupont S. , Long N. , Baklanov A. , Petersen C. , Sattler K. , Nielsen N. W.
Published: April 2010

Abstract. The large eddy simulations employing the SUBMESO model with the urban soil layer model SM2-U were performed for the model domain covering the Danish Island of Sealand and including the Copenhagen metropolitan area. Monthly and diurnal cycle variability were studied for the net radiation, sensible and storage heat fluxes, surface's temperatures, and others. These were evaluated for selected urban vs. non urban related types of covers/surfaces and urban districts such as city center, high buildings, industrial, and residential. Results showed strong effects of urban features on temporal and spatial variability. They are useful and applicable for verification of numerical weather prediction models and development of urban canopy parameterizations.
A group contribution method for estimating the vapour pressures of α-pinene oxidation products
Authors: Capouet M. , Müller J. F.
Published: April 2010

Abstract. A prediction method based on group contribution principles is proposed for estimating the vapour pressure of α-pinene oxidation products. Temperature dependent contributions are provided for the following chemical groups: carbonyl, nitrate, hydroxy, hydroperoxide, acyl peroxy nitrate and acid. On the basis of observed vapour pressure differences between isomers of diols and dinitrates, a simple refinement is introduced in the method, which allows to account for the influence of the substitutions on the vapour pressure for the hydroxy and nitrate functionalities. In general, the predicted vapour pressures of multifunctional compounds show a better agreement with experimental data (within a factor 2–3) than the UNIFAC method (Asher et al., 2002). Among the α-pinene products identified to date, pinic acid and hydroxy pinonic acid are predicted to be the least volatile compounds, with estimated vapour pressures of 3×10−6 torr and 6×10−7 torr, respectively. The vapour pressure of the other primary products range from 10−5 to 10−3 torr, with hydroxy hydroperoxides presenting the lowest values. Noting that multifunctional carboxylic acids, in particular pinic acid, are believed to be mostly present as dimers in laboratory conditions, we suggest that the partial vapour pressure of the pinic acid dimer should be close to the experimental subcooled vapour pressure for pinic acid (estimated at ~10−6 torr) due to its large contribution to the total concentration (dimer+monomer) in experimental conditions.
New particle formation in air mass transported between two measurement sites in Northern Finland
Authors: Komppula M. , Sihto S.-L. , Korhonen H. , Lihavainen H. , Kerminen V.-M. , Kulmala M. , Viisanen Y.
Published: April 2010

Abstract. This study covers four years of aerosol number size distribution data from Pallas and Värriö sites 250 km apart from each other in Northern Finland and compares new particle formation events between these sites. In eastern air masses almost all events were observed to start earlier at the eastern station Värriö, whereas in western air masses most of the events were observed to start earlier at the western station Pallas. This demonstrates that particle formation in a certain air mass type depends not only on the diurnal variation of the parameters causing the phenomenon (such as photochemistry) but also on some properties carried by the air mass itself. The correlation in growth rates between the two sites was relatively good, which suggests that the amount of condensable vapour causing the growth must have been at about the same level in both sites. The value of condensation sink was frequently much higher at the downwind station. It seems that secondary particle formation related to biogenic sources dominate in many cases over the particle sinks during the air mass transport between the sites. Two cases of transport from Pallas to Värriö were further analysed with an aerosol dynamics model. The model was able to reproduce the observed nucleation events 250 km down-wind at Värriö but revealed some differences between the two cases. The simulated nucleation rates were in both cases similar but the organic concentration profiles that best reproduced the observations were different in the two cases indicating that divergent formation reactions may dominate under different conditions. The simulations also suggested that organic compounds were the main contributor to new particle growth, which offers a tentative hypothesis to the distinct features of new particles at the two sites: Air masses arriving from Atlantic Ocean typically spent approximately only ten hours over land before arriving at Pallas, and thus the time for the organic vapours to accumulate in the air and to interact with the particles is relatively short. This can lead to low nucleation mode growth rates and even to suppression of detectable particle formation event due to efficient scavenging of newly formed clusters, as was observed in the case studies.
Retrieval of stratospheric ozone profiles from MIPAS/ENVISAT limb emission spectra: a sensitivity study
Authors: Glatthor N. , von Clarmann T. , Fischer H. , Funke B. , Gil-López S. , Grabowski U. , Höpfner M. , Kellmann S. , Linden A. , López-Puertas M. , Mengistu Tsidu G. , Milz M. , Steck T. , Stiller G. P. , Wang D.-Y.
Published: April 2010

Abstract. We report on the dependance of ozone volume mixing ratio profiles, retrieved from spectra of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), on different retrieval setups such as different a-priori profiles, regularization strengths and spectral regions used for analysis. MIPAS is a spaceborne limb-viewing Fourier transform infrared (FTIR) emission spectrometer, by which vertical profiles of various trace gases can be measured simultaneously. Purpose of this investigation is to check and to optimize the current retrieval setup. The choice of different a-priori profiles, of a different approach to retrieve the continuum radiation, and of a weaker regularization than in the reference data version (V2_O3_2) causes only small to moderate deviations of up to ±0.2, −0.3 and ±0.5 ppmv, respectively, in the retrieved ozone volume mixing ratios below 60 km altitude. Use of different microwindow sets optimized for polar, mid-latitude and tropical conditions results in deviations of up to ±1.5 ppmv in the altitude region of the ozone maximum, exceeding the total estimated retrieval error of 0.65 ppmv (polar regions) – 1.2 ppmv (tropics) in this height region. Therefore, to avoid latitudinal artefacts, one fixed set of microwindows is considered more appropriate for retrieval of a whole orbit rather than a latitude-dependent microwindow selection. For this task the microwindow set optimized for the polar atmosphere was found to be better suitable than its midlatitude and tropical counterparts. The results from the different microwindow sets, which variably cover MIPAS spectral bands A (685–970 cm−1) and AB (1020–1170 cm−1), indicated a positive bias of up to 1ppmv between the ozone maxima retrieved from the ozone emission in MIPAS band AB only and from combined analysis of MIPAS bands A and AB. Further investigations showed that this discrepancy can be caused by a bias between the radiance calibration of level-1B spectra of bands A and AB or by a bias between the spectroscopic data used in bands A and AB.
On the ability of chemical transport models to simulate the vertical structure of the N2O, NO2 and HNO3 species in the mid-latitude stratosphere
Authors: Berthet G. , Huret N. , Lefèvre F. , Moreau G. , Robert C. , Chartier M. , Pomathiod L. , Pirre M. , Catoire V.
Published: April 2010

Abstract. In this paper we study the impact of the modelling of N2O on the simulation of NO2 and HNO3 by comparing in situ vertical profiles measured at mid-latitudes with the results of the Reprobus 3-D CTM (Three-dimensional Chemical Transport Model) computed with the kinetic parameters from the JPL recommendation in 2002. The analysis of the measured in situ profile of N2O shows particular features indicating different air mass origins. The measured N2O, NO2 and HNO3 profiles are not satisfyingly reproduced by the CTM when computed using the current 6-hourly ECMWF operational analysis. Improving the simulation of N2O transport allows us to calculate quantities of NO2 and HNO3 in reasonable agreement with observations. This is achieved using 3-hourly winds obtained from ECMWF forecasts. The best agreement is obtained by constraining a one-dimensional version of the model with the observed N2O. This study shows that modelling the NOy partitioning with better accuracy relies at least on a correct simulation of N2O and thus of total NOy.
Horizontal and vertical profiles of ozone, carbon monoxide, non-methane hydrocarbons and dimethyl sulphide near the Mace Head observatory, Ireland
Authors: Purvis R. M. , McQuaid J. B. , Lewis A. C. , Hopkins J. R. , Simmonds P.
Published: April 2010

Abstract. The distribution of trace gases upwind and above the Mace Head Atmospheric Research Station, Ireland has been determined using measurements made from aircraft. The observations indicate excellent agreement between most non-methane hydrocarbons, dimethyl sulphide (DMS) and ozone measured at the surface, at 390 m overhead and in upwind boundary layer regions of the coastal Atlantic. Vertical profiles above the observatory indicated that local convective events result in a marine influence being detected at 3 km and above. The observation of isoprene from maritime sources at these levels was indicative of very rapid uplift on the hour timescale. Measurements of trace gases were also made directly upwind of the observatory over coastal regions and as far as the deep open ocean beyond the continental shelf. A maximum of 240 pptV DMS was observed in the boundary layer near to the shelf region, declining to a concentration of around 40 pptV at the coastline. The upwelling of nutrient rich waters at the ocean shelf location may be a possible explanation for the high abundance of DMS in these regions. The observations suggest that this region, some 150–200 km from the observatory, would under these environmental conditions have a major influence in the determining the DMS observed on-shore. The spatial distribution of ethene within boundary layer over coastal and deep waters differed significantly from DMS with an almost uniform abundance over all ocean regions.
Ambient formaldehyde measurements made at a remote marine boundary layer site during the NAMBLEX campaign – a comparison of data from chromatographic and modified Hantzsch techniques
Authors: Still T. J. , Al-Haider S. , Seakins P. W. , Sommariva R. , Stanton J. C. , Mills G. , Penkett S. A.
Published: April 2010

Abstract. Ambient formaldehyde concentrations are reported from the North Atlantic Marine Boundary Layer Experiment (NAMBLEX) campaign at Mace Head on the west coast of Ireland during August 2002. The results from two techniques, using direct determination via gas chromatography and the Hantzsch technique, show similar trends but a significant off set in concentrations. For westerly air flows characteristic of the marine boundary layer, formaldehyde concentrations from the gas chromatographic and Hantzsch technique ranged from 0.78–1.15 ppb and 0.13–0.43 ppb, respectively. Possible reasons for the discrepancy have been investigated and are discussed, however, no satisfactory explanation has yet been found. In a subsequent intercomparison the two techniques were in good agreement. The observed concentrations have been compared with previous formaldehyde measurements in the North Atlantic marine boundary layer and with other measurements from the NAMBLEX campaign. The measurements from the Hantzsch technique and the GC results lie at the lower and upper ends respectively of previous measurements. In contrast to some previous measurements, both techniques show distinct diurnal profiles with day maxima and with an amplitude of approximately 0.15 ppb. Strong correlations were observed with ethanal concentrations measured during NAMBLEX and the ratio of ethanal to formaldehyde determined by the gas chromatographic technique is in good agreement with previous measurements. Some simple box modelling has been undertaken to investigate possible sources of formaldehyde. Such models are not able to predict absolute formaldehyde concentrations as they do not include transport processes, but the results show that oxygenated VOCs such as ethanal and methanol are very significant sources of formaldehyde in the air masses reaching Mace Head.