13th Conference on Applied Climatology and the 10th Conference on Aviation, Range, and Aerospace Meteorology

Wednesday, 15 May 2002: 3:45 PM
Detection of airborne volcanic ash with GOES: issues and prospects for the coming decade
Gary P. Ellrod, NOAA/NESDIS/ORA, Camp Springs, MD
Geostationary Operational Environmental Satellites (GOES) provide an excellent platform for monitoring hazardous airborne volcanic ash clouds due to their high imaging frequency, multi-spectral capabilities, and good resolution (1 km visible, 4 km InfraRed (IR)). Brightness temperature differences between GOES IR bands at 12.0 and 10.7 micrometers, and other multi-spectral techniques have been successfully employed at operational Volcanic Ash Advisory Centers (VAACs) in North and South America for tracking volcanic ash clouds since first becoming available on GOES-8 in 1994.

Beginning with the GOES-12 spacecraft (launched July 23, 2001 and checked out by November 2001) through GOES-P (scheduled for 2007 launch), the 12.0 micrometer band (4 km) on the GOES Imager will be replaced by a 13.3 micrometer band (8 km initially). The lower resolution (10 km) Sounder will remain unchanged. The effects of this change need to be assessed, and alternative strategies devised to maintain the integrity of the operational volcanic ash alerting system.

An impact study has been completed using GOES-8 Imager and equivalent Sounder channels for prior eruptions, and for one small eruption observed during GOES-12 checkout on 9 October 2001. The results indicate that there will most likely be some degradation of ash detection capability, especially at night, but that analysts armed with animated imagery will still be able to identify and track ash clouds, and issue timely advisories for aircraft avoidance.

Recommended multi-spectral images for operational ash detection during the next 6-8 years utilize the 3.9, 10.7 and 13.3 micrometer bands on the reconfigured GOES Imagers. In the event of a strong volcanic eruption that results in a long-lived ash cloud, the GOES Imager will need to be supplemented at low-mid latitudes with data from higher resolution instruments such as MODIS or AVHRR on polar-orbiting spacecraft, or the low resolution GOES Sounder. Examples from these systems will be shown for recent eruptions.

By the end of the decade (circa 2008), an Advanced Baseline Imager (ABI) will be implemented on GOES-Q or R, providing greatly improved ash detection capability. Although planning for ABI is still in progress, it will likely have a minimum of 12 spectral bands (including restoration of the 12 micrometer band), at twice the resolution (2 km IR, 0.5 km visible), with faster scanning that allows frequent global coverage with no regional conflicts as with the current Imagers. Additional channels are also being considered to provide detection of both ash and SO2 gas emissions, a unique indicator of significant volcanic activity.

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