@article{EliassonYoshitaniWeberetal.2014, author = {Eliasson, Jonas and Yoshitani, Junichi and Weber, Konradin and Yasuda, Nario and Iguchi, Masato and Vogel, Andreas}, title = {Airborne Measurement in the Ash Plume from Mount Sakurajima: Analysis of Gravitational Effects on Dispersion and Fallout}, series = {International Journal of Atmospheric Sciences}, volume = {2014}, journal = {International Journal of Atmospheric Sciences}, publisher = {Wiley}, issn = {2314-4122}, doi = {10.1155/2014/372135}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:due62-opus-50955}, pages = {16}, year = {2014}, abstract = {Volcanic ash concentrations in the plume from Sakurajima volcano in Japan are observed from airplanes equipped with optical particle counters and GPS tracking devices. The volcano emits several puffs a day. The puffs are also recorded by the Sakurajima Volcanological Observatory. High concentrations are observed in the puffs and fallout driven by vertical air current, called streak fallout. Puffs dispersion is analyzed by the classical diffusion-advection method and a new gravitational dispersion method. The fluid mechanic of the gravitational dispersion, streak fallout, and classical diffusion-advection theory is described in three separate appendices together with methods to find the time gravitational dispersion constant and the diffusion coefficient from satellite photos. The diffusion-advection equation may be used to scale volcanic eruptions so the same eruption plumes can be scaled to constant flux and wind conditions or two eruptions can be scaled to each other. The dispersion analyses show that dispersion of volcanic plumes does not follow either theories completely. It is most likely diffusion in the interface of the plume and the ambient air, together with gravitational flattening of the plumes core. This means larger boundary concentration gradients and smaller diffusion coefficients than state of the art methods can predict.}, subject = {Vulkanismus}, language = {en} } @inproceedings{VogelWeberFischeretal.2012, author = {Vogel, Andreas and Weber, Konradin and Fischer, Christian and Prata, A. J. and Durant, A. J.}, title = {Aircraft in situ and remote sensing measurements of emissions from Etna volcano, Sicily}, series = {Geophysical Research Abstracts: EGU General Assembly 2012}, booktitle = {Geophysical Research Abstracts: EGU General Assembly 2012}, publisher = {Copernicus}, address = {G{\"o}ttingen}, year = {2012}, abstract = {Volcanoes emit particles (silicates and sulphate aerosol) and gases (e.g., water and sulphur dioxide) which influence the radiative balance of the atmosphere. The rate at which sulphur dioxide oxidises to sulphate aerosol is poorly constrained and measurements of downwind abundance are required to quantify the rate at which this process occurs. During July and November 2011, a series of measurements were performed in emissions from Etna Volcano, Sicily, using the University of Applied Sciences (Dusseldorf) research aircraft. Both in situ and remote sensing instrumentation was simultaneously deployed to quantify the down-wind characteristics of gases and particles in the plume emitted by the volcano. In situ particle characteristics were measured using a Grimm 1.109 optical particle counter (microparticles 0.25-32 microns) and Grimm 1320 diffusion electrometer (nanoparticles 25-300 nanometers). Column abundance of sulphur dioxide was measured using a vertically-pointing differential optical absorption spectrometer (DOAS). These measurements were compared to horizontal pathlength-integrated measurements of sulphur dioxide from the Airborne Volcanic Imaging Object Detector (AVOID). Down-wind plume dispersion was discriminated through a series of aircraft transects below and through the volcanic plume. The emissions contained large amounts of nanoparticles relative to microparticles, which reflects gas-phase nucleation of sulphate aerosol. The AVOID system discriminated horizontal layering of volcanic aerosol at altitudes of up to 12,000 ft from a detection range of >50 km. Plume boundaries were discriminated using a combination of the in situ and DOAS measurements in order to compare to the pathlength-integrated measurements from AVOID.}, subject = {Forschungsflugzeug}, language = {en} }