Evaluation of quantitative satellite-based retrievals of volcanic ash clouds

David J Schneider, USGS Alaska Volcano Observatory, Anchorage, United States, Michael J Pavolonis, NOAA Madison, NESDIS/STAR, Madison, WI, United States, Stephan Bojinski, World Meteorological Organizat, Geneva, Switzerland, Richard Siddans, STFC Rutherford Appleton Laboratory, Didcot, United Kingdom and Gareth Thomas, Rutherford Appleton Laboratory, Didcot, United Kingdom