Volcanic ash and aerosol detection versus dust

detection using GOES and MODIS imagery

Bernadette ConnellCooperative Institute for Research in the Atmosphere

Colorado State University

2nd International Conference on Volcanic Ash and Aviation SafetyJune 21-24, 2004

Alexandria, Virginia, USA

Main Features“Easy” to implement techniques:

BT11.0um-BT12.0um

BT11.0um-BT3.9um (night)Estimated “reflected” 3.9um (day)False color 3.9/11.0/12.0um product BT8.5um-BT12.0um (ash and/or aerosol)

Examples of volcanic constituents vs. dust with GOES and MODIS data

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: BT11.0-BT3.9 = 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

• BT8.3um – BT12.0um = negative for SO2 and H2SO4 • BT8.3um – BT12.0um = negative for silicates, but sensitive to

particle size.

Ash/Dust in the 11.0 – 12.0 um range• BT11.0um-BT12.0um = negative for ash/dust

= positive for ice/water cloud

Popocatepetl Volcano, Mexico22 January, 2001 22:45 UTCGOES-8 imagery

Visible 3.9 um

10.7 um

Popocatepetl Volcano, Mexico22 January, 2001 22:45 UTCGOES-8 imagery

GOES imagery and products 23 January 2001 04:45 UTC

Popocatepetl, Mexico

10.7 um BT10.7-BT3.9

BT10.7-BT12.0False color: 10.9/BT10.7-BT12.0/BT10.7-BT3.9

GOES-8 BT10.7-BT12.0 MODIS Terra BT11.0-BT12.0

MODIS Terra BT8.5-BT12.0

Popocatepetl, Mexico

22 January, 2001 04:45 UTC GOES, 04:50 UTC MODIS

3 8 13 18Hour after eruption

-12

-10

-8

-6

-4

-2

larg

es

t B

T1

0.7

- B

T1

2.0

Popocatepetl, 22 January 2001Montserrat, 21 October 1997Montserrat second burst Reventador, 3 November 2002

18 April, 2001 19:30 UTC

DUST detection with GOES imagery

visible 10.7 um

BT10.7-BT12.0 Reflectance

DUST detection

18 April, 2001 19:30 UTC

MODIS Aqua true colorGOES-8 BT10.7-BT12.0

MODIS Aqua BT11.0-BT12.0 MODIS Aqua BT8.5-BT12.0

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)

BT10.7-BT12.0?

• What are we seeing using the 8.x um region (ash/dust/aerosol)?

• How can we best combine this information with other information on SO2 detection?