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Snowpacks contain many carbonaceous species that can potentially impact on snow albedo and arctic atmospheric chemistry. During the OASIS field campaign, in March and April 2009, Elemental Carbon (EC), Water insoluble Organic Carbon (WinOC) and Dissolved Organic Carbon (DOC) were investigated in various types of snow: precipitating snows, remobilized snows, wind slabs and depth hoars. EC was found to represent less than 5% of the Total Carbon Content (TCC = EC + WinOC + DOC), whereas WinOC was found to represent an unusual 28 to 42% of TCC. Snow type was used to infer physical processes influencing the evolution of different fractions of DOC. DOC is highest in soil influenced indurated depth hoar layers due to specific wind related formation mechanisms in the early season. Apart from this specific snow type, DOC is found to decrease from precipitating snow to remobilized snow to regular depth hoar. This decrease is interpreted as due to cleaving photochemistry and physical equilibration of the most volatile fraction of DOC. Depending on the relative proportions of diamond dust and fresh snow in the deposition of the seasonal snowpack, we estimate that 31 to 76% of DOC deposited to the snowpack is reemitted back to the boundary layer. Under the assumption that this reemission is purely photochemical, we estimate an average flux of VOC out of the snowpack of 20 to 170 mu g(C) m(-2) h(-1). Humic like substances (HULIS), short chain diacids and aldehydes are quantified, and showed to represent altogether a modest (

In summer 2004 the long-range transport of particles emitted from large forest fires in Canada and Alaska contributed significantly to the aerosol loading of the free troposphere over Europe . Airborne in situ measurements on the intercontinental transport of aerosols from biogenic and anthropogenic origin were performed at the European west coast as a part of the ICARTT-ITOP study (Intercontinental Transport of Ozone and Precursors). During the study the German Falcon 20 E-5 research aircraft was operating from an airport north of Paris. The aircraft was equipped with extensive in-situ aerosol and trace gas instrumentation. Measurement flights were performed over the European west coast probing the entire tropospheric column from the boundary layer to the upper free troposphere. Trajectory analyses were conducted for all the measurement flights and permitted the identification of the plume origin for several forest fires cases. Simultaneously to the airborne in-situ measurements, black carbon data from the high-alpine research station Jungfraujoch (JFJ; 3580 m asl) in Switzerland showed elevated BC levels during this period. Trajectory analyses confirmed that the JFJ station was probing the same forest fire plume as the Falcon during the measurement flights at the European West coast.

The mass fraction of black carbon (BC) in the atmospheric aerosol and its mixing state are important for the direct aerosol climate effect. These properties also determine if BC is incorporated into cloud hydrometeors (i.e. droplets and ice crystals) and are important because the microphysical and optical properties of the cloud are altered (indirect aerosol effect). Measurements were performed during several Cloud and Aerosol Characterization Experiments, in winter 2004 (CLACE3), summer 2004 (CLACE3.5), winter 2005 (CLACE4) and summer 2005 (CLACE4.5) at the high Alpine research station Jungfraujoch (3580 m asl).

Within the WMO Global Atmosphere Watch (GAW) program continuous measurements of aerosol parameters have been performed at the Jungfraujoch high Alpine site since 1988. This measurement site is located on an exposed mountain col in the Bernese Alps, Switzerland, at 3580 meters altitude. Throughout the year the station is within clouds about 40% of the time. In warm months, the site is influenced by injection of planetary boundary layer air into the free troposphere during sunny afternoons due to thermal convection, while in winter it is usually in the undisturbed free troposphere. Several intensive field studies, named CLACE (Cloud and Aerosol Characterization Experiment), have been performed in both summer and winter within international collaborations. State-of-the-art instrumentation is employed to characterize the aerosol size distribution (Scanning Mobility Particle Sizer, SMPS; Optical Particle Counter, OPC). The University of Manchester and the Max Planck Institute in Mainz operated two Aerodyne Aerosol Mass Spectrometers (AMS) to measure the size segregated chemical composition. Other measured parameters were the hygroscopic properties of the particles (Hygroscopicity Tandem Differential Mobility Analyzer, H-TDMA), cloud microphysics (Particulate Volume Monitor, PVM; Forward Scattering Spectrometer Probe, FSSP; Cloud Particle Imager, CPI), and particle morphology (Environmental Scanning Electron Microscope, ESEM). An Air Ion Spectrometer (AIS) and an outdoor SMPS were also employed. The latter two instruments are especially well suited to measure nanometer sized particles (charged particles and sum of neutral and charged particles, respectively) in order to elucidate their formation mechanisms and rates. Different inlets are used for these instruments: A heated inlet (25°C) designed to prevent ice build-up and to evaporate cloud particles at an early stage, ensuring that the cloud condensation nuclei and/or ice nuclei are also sampled. This is called the total inlet. An interstitial inlet operated with a PM2 cyclone impactor removed all cloud droplets and ice crystals from the ambient air. Within a cloud the sampled air thus represents the interstitial (or unactivated) aerosol fraction. In addition, the Institute for Tropospheric Research (IFT) operated a Counterflow Virtual Impactor (CVI, Mertes et al., 2005). The CVI was part of a new prototype sampling system (Ice-CVI) that allows for the separation of small ice particles from large ice crystals, cloud droplets and interstitial aerosol particles. The extracted ice particles are dried airborne in the system and the remaining residual particles which correspond to the former ice nuclei were analyzed with a variety of different instruments. Differencing the response downstream of the different inlets provides insight in the fractionation of aerosol particles between the cloud phase and the interstitial phase.