Retrieval of Ash Plume Altitude from IASI TIR Radiances: A Feasibility Study.
Vandenbussche, Sophie1; Theys, Nicolas1; Clarisse, Lieven2; Kochenova, Svetlana1; Vandaele, Ann Carine1; Kumps, Nicolas1; De Mazière, Martine1
1Belgian Institute for Space Aeronomy, BELGIUM; 2Free University of Brussels, BELGIUM
Ash can be emitted in large amounts during volcanic eruptions. It represents a non-negligible climate forcing (absorption, scattering and emission of radiation) and a major threat to commercial jet aircrafts (melted ash blocks the engines). Both impacts of ash plumes are strongly dependent on their altitude which currently is poorly characterised. Ash shows strong and typical spectral features in the Thermal Infrared (TIR) atmospheric window (800-1200cm-1), allowing the retrieval of ash atmospheric load and of some ash properties.
IASI instruments flying onboard Metop-A since 2006 and Metop-B since 2012 are well suited for such retrievals, as they offer a continuous spectral coverage in the TIR with sufficiently high spectral resolution and signal-to-noise ratio. Furthermore, those instruments are excellent candidates for long-term climate studies and for future eruptions monitoring because they offer global Earth coverage twice a day for at least 15 years, followed by a New Generation instrument planned in 2020.
In the last years, we have developed a strategy to retrieve vertical profiles of mineral dust concentration in the low troposphere using IASI TIR measurements. Mineral dust is another type of aerosols with strong typical spectral features in the TIR atmospheric window which we exploit for our retrievals. Based on this experience, we study here the possibility to obtain information on ash plumes height using a similar strategy. The main difference is that ash may be found a lot higher in the troposphere, and up to the lower stratosphere, while dust is generally located below 6km altitude.