1. Volcanic ash and aerosol detection versus dust detection using GOES and MODIS imagery Bernadette Connell Cooperative Institute for Research in the Atmosphere Colorado State University 2nd International Conference on Volcanic Ash and Aviation Safety June 21-24, 2004 Alexandria, Virginia, USA

2. Main Features  “Easy” to implement techniques:  BT 11.0um -BT 12.0um  BT 11.0um -BT 3.9um (night)  Estimated “reflected” 3.9um (day)  False color 3.9/11.0/12.0um product  BT 8.5um -BT 12.0um (ash and/or aerosol)  Examples of volcanic constituents vs. dust with GOES and MODIS data

3. Ash/Dust in the 3.9 – 11.0 um range DAY: higher reflectance for ash/dust clouds and water droplets; lower reflectance for ice particles NIGHT: BT 11.0 -BT 3.9 = negative for thin ash/dust clouds = negative for ice cloud = positive for water cloud Volcanic Aerosol vs. Ash/Dust in the 8.5 – 12.0 um range BT 8.3um – BT 12.0um = negative for SO 2 and H 2 SO 4 BT 8.3um – BT 12.0um = negative for silicates, but sensitive to particle size. Ash/Dust in the 11.0 – 12.0 um range BT 11.0um -BT 12.0um = negative for ash/dust = positive for ice/water cloud

4. Popocatepetl Volcano, Mexico 22 January, 2001 22:45 UTC GOES-8 imagery Visible3.9 um 10.7 um

5. Popocatepetl Volcano, Mexico 22 January, 2001 22:45 UTC GOES-8 imagery

6. GOES imagery and products 23 January 2001 04:45 UTC Popocatepetl, Mexico 10.7 umBT 10.7 -BT 3.9 BT 10.7 -BT 12.0 False color: 10.9/BT 10.7 -BT 12.0 /BT 10.7 -BT 3.9

8. GOES-8 BT 10.7 -BT 12.0 MODIS Terra BT 11.0 -BT 12.0 MODIS Terra BT 8.5 -BT 12.0 Popocatepetl, Mexico 22 January, 2001 04:45 UTC GOES, 04:50 UTC MODIS

9. 18 April, 2001 19:30 UTC DUST detection with GOES imagery visible 10.7 um BT 10.7 -BT 12.0 Reflectance

11. DUST detection 18 April, 2001 19:30 UTC MODIS Aqua true colorGOES-8 BT 10.7 -BT 12.0 MODIS Aqua BT 11.0 -BT 12.0 MODIS Aqua BT 8.5 -BT 12.0

12. Summary remarks and points to ponder Variability of eruption cloud: If multi-channel imagery is available, use it! What is the significance of large (or small) BT 10.7 -BT 12.0 ? What are we seeing using the 8.x um region (ash/dust/aerosol)? How can we best combine this information with other information on SO 2 detection?