1. Atmospheric Research, Australia 21-25 June 20042nd International Conference on Volcanic Ash and Aviation Safety Alexandria, VA. 1 Detection of upper level SO 2 via the GOES Sounder Fred Prata 1, Anthony Schreiner 2, Gary Ellrod 3 and Timothy Schmit 4 1 CSIRO Atmospheric Research, Australia 2 Cooperative Institute for Meteorological Satellite Studies (CIMSS) University of Wisconsin-Madison Madison, WI 53706, U.S.A. 3 NOAA/NESDIS, Office of Research and Applications Camp Springs, Maryland 4 NOAA/NESDIS, Office of Research and Applications Madison, WI 53706, U.S.A.

2. 21-25 June 20042nd International Conference on Volcanic Ash and Aviation Safety Alexandria, VA. 2 Atmospheric Research, Australia The GOES Sounder

3. 21-25 June 20042nd International Conference on Volcanic Ash and Aviation Safety Alexandria, VA. 3 Atmospheric Research, Australia The GOES Sounder

4. 21-25 June 20042nd International Conference on Volcanic Ash and Aviation Safety Alexandria, VA. 4 Atmospheric Research, Australia SO 2 from GOES Infrared channel near 7.3 µm SO 2 absorption (channel 11) Reference channel (channel 9) Upper-level SO 2 only (>3 km) Example – Montserrat

5. 21-25 June 20042nd International Conference on Volcanic Ash and Aviation Safety Alexandria, VA. 5 Atmospheric Research, Australia SO 2 Retrieval from Sounder Data Absorption measurement. GOES channel 11 brightness temperatures are colder than expected, because of the presence of SO 2. Reference channel. A second channel is used to eliminate background effects. The O 3 channel was used (channel 9). Brightness temperature difference (  BT). The  BT is related to transmittance and then to absorber amount through radiative transfer modelling.

6. 21-25 June 20042nd International Conference on Volcanic Ash and Aviation Safety Alexandria, VA. 6 Atmospheric Research, Australia GOES-12 SO 2 retrieval using the ozone channel as reference

7. 21-25 June 20042nd International Conference on Volcanic Ash and Aviation Safety Alexandria, VA. 7 Atmospheric Research, Australia Montserrat GOES AIRS TOMS HYSPLIT JULY 13, 2002

8. 21-25 June 20042nd International Conference on Volcanic Ash and Aviation Safety Alexandria, VA. 8 Atmospheric Research, Australia Conclusions It appears that the GOES sounder is capable of detecting Upper Troposphere Lower Stratosphere SO 2. Unprecedented temporal resolution heralds new possibilities for monitoring SO 2 and ash. Changes to the ABI will permit purposeful SO 2 detection using the 7.3 µm channel. More work is required to validate the SO 2 retrievals and to find the ‘optimum’ reference channels.