Gysel, Martin
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Martin Gysel
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- PublikationHygroscopicity of the submicrometer aerosol at the high-alpine site Jungfraujoch, 3580 m a.s.l., Switzerland(Copernicus, 30.09.2008) Sjögren, Staffan; Gysel, Martin; Weingartner, Ernest; Alfarra, M. Rami; Duplissy, Jonathan; Cozic, Julie; Crosier, Jonathan; Coe, Hugh; Baltensperger, Urs [in: Atmospheric Chemistry and Physics]Data from measurements of hygroscopic growth of submicrometer aerosol with a hygroscopicity tandem differential mobility analyzer (HTDMA) during four campaigns at the high alpine research station Jungfraujoch, Switzerland, are presented. The campaigns took place during the years 2000, 2002, 2004 and 2005, each lasting approximately one month. Hygroscopic growth factors (GF, i.e. the relative change in particle diameter from dry diameter, D0, to diameter measured at higher relative humidity, RH) are presented for three distinct air mass types, namely for: 1) free tropospheric winter conditions, 2) planetary boundary layer influenced air masses (during a summer period) and 3) Saharan dust events (SDE). The GF values at 85% RH (D0=100 nm) were 1.40±0.11 and 1.29±0.08 for the first two situations while for SDE a bimodal GF distribution was often found. No phase changes were observed when the RH was varied between 10–90%, and the continuous water uptake could be well described with a single-parameter empirical model. The frequency distributions of the average hygroscopic growth factors and the width of the retrieved growth factor distributions (indicating whether the aerosol is internally or externally mixed) are presented, which can be used for modeling purposes. Measurements of size resolved chemical composition were performed with an aerosol mass spectrometer in parallel to the GF measurements. This made it possible to estimate the apparent ensemble mean GF of the organics (GForg) using inverse ZSR (Zdanovskii-Stokes-Robinson) modeling. GForg was found to be ~1.20 at aw=0.85, which is at the upper end of previous laboratory and field data though still in agreement with the highly aged and oxidized nature of the Jungfraujoch aerosol.01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationThe influence of small aerosol particles on the properties of water and ice clouds(Royal Society of Chemistry, 09.08.2008) Choularton, Thomas W.; Bower, Keith N.; Weingartner, Ernest; Crawford, Ian; Coe, Hugh; Gallagher, Martin W.; Flynn, Michael; Crosier, Jonathan; Connolly, Paul; Targino, Admir Créso; Alfarra, M. Rami; Baltensperger, Urs; Sjögren, Staffan; Verheggen, Bart; Cozic, Julie; Gysel, Martin [in: Faraday Discussions]In this paper, results are presented of the influence of small organic- and soot-containing particles on the formation of water and ice clouds. There is strong evidence that these particles have grown from nano particle seeds produced by the combustion of oil products. Two series of field experiments are selected to represent the observations made. The first is the CLoud-Aerosol Characterisation Experiment (CLACE) series of experiments performed at a high Alpine site (Jungfraujoch), where cloud was in contact with the ground and the measuring station. Both water and ice clouds were examined at different times of the year. The second series of experiments is the CLOud Processing of regional Air Pollution advecting over land and sea (CLOPAP) series, where ageing pollution aerosol from UK cities was observed, from an airborne platform, to interact with warm stratocumulus cloud in a cloud-capped atmospheric boundary layer. Combining the results it is shown that aged pollution aerosol consists of an internal mixture of organics, sulfate, nitrate and ammonium, the organic component is dominated by highly oxidized secondary material. The relative contributions and absolute loadings of the components vary with location and season. However, these aerosols act as Cloud Condensation Nuclei (CCN) and much of the organic material, along with the other species, is incorporated into cloud droplets. In ice and mixed phase cloud, it is observed that very sharp transitions (extending over just a few metres) are present between highly glaciated regions and regions consisting of supercooled water. This is a unique finding; however, aircraft observations in cumulus suggest that this kind of structure may be found in these cloud types too. It is suggested that this sharp transition is caused by ice nucleation initiated by oxidised organic aerosol coated with sulfate in more polluted regions of cloud, sometimes enhanced by secondary ice particle production in these regions.01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationHygroscopic growth and water uptake kinetics of two-phase aerosol particles consisting of ammonium sulfate, adipic and humic acid mixtures(Elsevier, 02/2007) Sjögren, Staffan; Gysel, Martin; Weingartner, Ernest; Baltensperger, Urs; Cubison, Michael J.; Coe, Hugh; Zardini, Alessandro A.; Marcolli, Claudia; Krieger, Ulrich K.; Peter, Thomas [in: Journal of Aerosol Science]The hygroscopic growth of solid aerosol particles consisting of mixtures of ammonium sulfate and either adipic acid or Aldrich humic acid sodium salt was characterized with a hygroscopicity tandem differential mobility analyzer and an electrodynamic balance. In particular, the time required for the aerosol particle phase and the surrounding water vapor to reach equilibrium at high relative humidity (RH) was investigated. Depending on the chemical composition of the particles, residence times of > 40 s were required to reach equilibrium at 85% RH, yielding up to a 7% reduction in the measured hygroscopic growth factors from measurements at 4 s residence time compared to measurements at equilibrium. We suggest that the solid organic compound, when present as the dominant component, encloses the water-soluble inorganic salt in veins and cavities, resulting in the observed slow water uptake. Comparison with predictions from the Zdanovskii-Stokes-Robinson relation shows enhanced water uptake of the mixed particles. This is explained with the presence of the salt solution in veins resulting in a negative curvature of the solution meniscus at the opening of the vein. In conclusion, it is important for studies of mixtures of water soluble compounds with insoluble material to allow for sufficient residence time at the specified humidity to reach equilibrium before the hygroscopicity measurements.01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationThe effect of physical and chemical aerosol properties on warm cloud droplet activation(Copernicus, 2006) McFiggans, Gordon B.; Artaxo, Paulo; Baltensperger, Urs; Coe, Hugh; Facchini, Maria Cristina; Feingold, Graham; Fuzzi, Sandro; Gysel, Martin; Laaksonen, Ari; Lohmann, Ulrike; Mentel, Thomas F.; Murphy, Daniel M.; O'Dowd, Colin D.; Snider, Jefferson R.; Weingartner, Ernest [in: Atmospheric Chemistry and Physics]Abstract. The effects of atmospheric aerosol on climate forcing may be very substantial but are quantified poorly at present; in particular, the effects of aerosols on cloud radiative properties, or the "indirect effects" are credited with the greatest range of uncertainty amongst the known causes of radiative forcing. This manuscript explores the effects that the composition and properties of atmospheric aerosol can have on the activation of droplets in warm clouds, so potentially influencing the magnitude of the indirect effect. The effects of size, composition, mixing state and various derived properties are assessed and a range of these properties provided by atmospheric measurements in a variety of locations is briefly reviewed. The suitability of a range of process-level descriptions to capture these aerosol effects is investigated by assessment of their sensitivities to uncertainties in aerosol properties and by their performance in closure studies. The treatment of these effects within global models is reviewed and suggestions for future investigations are made.01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationSecondary organic aerosols from anthropogenic and biogenic precursors(Royal Society of Chemistry, 2005) Baltensperger, Urs; Kalberer, Markus; Dommen, Josef; Paulsen, Dwane; Alfarra, M. Rami; Coe, Hugh; Fisseha, Rebeka; Gascho, Astrid; Gysel, Martin; Nyeki, Stephan; Sax, Mirjam; Steinbacher, Martin; Prévôt, André S.H.; Sjögren, Staffan; Weingartner, Ernest; Zenobi, Renato [in: Faraday Discussions]Secondary organic aerosol (SOA) formation from the photooxidation of an anthropogenic (1,3,5-trimethylbenzene) and a biogenic (α-pinene) precursor was investigated at the new PSI smog chamber. The chemistry of the gas phase was followed by proton transfer reaction mass spectrometry, while the aerosol chemistry was investigated with aerosol mass spectrometry, ion chromatography, laser desorption ionization mass spectrometry, and infrared spectroscopy, along with volatility and hygroscopicity studies. Evidence for oligomer formation for SOA from both precursors was given by an increasing abundance of compounds with a high molecular weight (up to 1000 Da) and by an increasing thermal stability with increasing aging time. The results were compared to data obtained from ambient aerosol samples, revealing a number of similar features.01A - Beitrag in wissenschaftlicher Zeitschrift