| Summary: | Between April 19 and May 18, 2010, altogether 17 flights were performed by the DLR Falcon research aircraft to survey and sample the emissions of the Eyjafjalla volcano on Iceland. The measurements were performed on request of the Deutscher Wetterdienst (DWD, German Weather Service) and the Bundesministerium für Verkehr, Bau und Stadtentwicklung (BMVBS, Federal Ministry of Transport, Building and Urban Development). The Falcon was instrumented with a downward looking, scanning 2-μm-wind-Lidar (providing qualitative aerosol backscatter as well as horizontal wind), and several in-situ instruments: The particle instrumentation, including wing station aerosol spectrometer probes (PCASP, FSSP-300, 2D-C) covered particle number and size from 5 nm to some tens of μm. Further in-situ instruments measured aerosol absorption (PSAP), O3, CO, SO2 and H2O mixing ratios and standard meteorological parameters. In this contribution we focus on the first results of the in-plume measurements of particle size distribution, total fine mode particle number concentrations and absorption coefficient and SO2. A key result is that the total volume and mass of (aged) volcanic ash is dominated by particles of some µm size, with only less than 10 percent typically residing in the size range below 2.5 μm particle diameter. Possible systematic errors due to counting statistics of large particles and uncertainties in refractive index, however, remain large at present.
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