TY - JOUR A1 - Elíasson, Jonas A1 - Weber, Konradin A1 - Vogel, Andreas A1 - Pálsson, Thorgeir A1 - Yoshitani, Junichi A1 - Miki, Daisuke T1 - Investigation and Separation of Turbulent Fluctuations in Airborne Measurements of Volcanic Ash with Optical Particle Counters JF - Journal of Disaster Research N2 - The science of measuring airborne volcanic ash concentrations supports research in such fields as atmospheric environmental science and the modeling of atmospheric pollution from volcanoes, and is thus very valuable to the aviation industry. These measurements show large scatter directly traceable to turbulent fluctuations responsible for diffusing volcanic dust. Before semistationary components in observations can be compared to each other or to simulation results, they must be separated from fluctuations. In the design of the separation process, however, neither seasonal or diurnal periodicity nor random disturbance with known properties exists to serve as a guideline. It has been suggested that fluctuations could be eliminated through repeated convolutions of a simple 3-point filter enough times. The number of convolutions is chosen from the change in the rate of increase of a special variability parameter. When semistationary concentrations are separated from fluctuations, their statistics are compared to turbulence parameters and the autocorrelation of the series. The method is demonstrated using three measurement series from Sakurajima, Japan measured in 2013. It is concluded that this new method is simple and trustworthy where knowledge and experience of the environmental parameters can be utilized to support the results. They indicate a variability of 40% in the relative fluctuations of the PM10 and around 20% of the PM2.5. The relative fluctuations may be considered completely random, but normally distributed rather than a white noise with an evenly distributed variance spectrum. KW - Luftreinhaltung Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:due62-opus-50023 SN - 1883-8030 VL - 11 IS - 1 SP - 72 EP - 84 PB - Fuji Technology Press Ltd. ER - TY - JOUR A1 - Elíasson, Jonas A1 - Yoshitani, Junichi A1 - Miki, Daisuke A1 - Weber, Konradin A1 - Bölke, Christoph A1 - Scharifi, Emad T1 - Measurements of Particle Distribution and Ash Fluxes in the Plume of Sakurajima Volcano with Optical Particle Counter JF - Journal of Disaster Research N2 - Volcanic eruptions have caused very costly disturbances of international air traffic. This problem has been dealt with by simulating the formation and migration of dangerous ash plumes. However, the results of the simulations have sometimes been too safe, producing ash clouds that are too large. This was especially the case for the North Atlantic in 2010 (Eyjafjallajökull) and 2011 (Grímsvötn). Since 2012, an international cooperation team led by the Disaster Prevention Research Institute (DPRI) of Kyoto University has conducted airborne measurements of volcanic ash concentrations in the plume from Mount Sakurajima in Kagoshima Prefecture, Japan. This volcano was chosen because of its frequent but limited eruptions, which allow close observation. These measurement campaigns have provided data showing gravitational flattening of the plume, a new and previously unknown dispersion process of volcanic plumes. A new and previously unknown fallout process, called streak fallout, also has been measured. Results concerning plume flux, concentration distributions, aerosol (PM10) content of the plume, and content of very fine particles (PM2.5 and PM1) are presented, and the ways by which the observational methods can be used to produce reliable initial data and boundary values for simulations of plume dispersion are discussed. KW - Luftreinhaltung Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:due62-opus-50030 SN - 1883-8030 VL - 11 IS - 1 SP - 85 EP - 95 PB - Fuji Technology Press Ltd. ER -