Volcanic ash detection and cloud top height estimates from the GOES-12 imager: Coping without a 12 Mm infrared band

The Geostationary Operational Environmental Satellite (GOES)-12 Imager, which was activated 1 April 2003, has been re-configured with the addition of a 13.3 mum Infrared (IR) spectral band, in place of the "split window'' 12.0 mum band. Since the latter channel had been successfully used for volcanic ash detection from GOES for nearly ten years, there is some concern about the impact of this change on short term warnings and forecasts for aviation operations over North and South America. The first significant volcanic eruptions observed by the new GOES-12 satellite occurred during 12-15 July 2003 at the Soufriere Hills Volcano, Montserrat. GOES-12 was able to observe the eruption clouds adequately during this period using multi-spectral techniques. Based on comparisons with multi-spectral images from the GOES Sounder, GOES-12 ash detection capability for this event was equal in quality to what would have been available from prior GOES with a 12.0 mum band.