Challenges to using the 0. 8-12. um difference product

Challenges to using the 10.8-12.0 um difference product

• For optically thick plumes, when water and ice are mixed with the volcanic debris, the ‘ash’ signal may be confused

• Low ash concentrations can be difficult to detect

Challenges to using the 3.9-10.8 um difference product

• Limitations to measurements for cold scenes at 3.9 um:

• The steep slope of the Plank function at cold temperatures (<-50 C), the instrument noise at 3.9 um becomes very large

• Uncertainties with properties of reflectance/emittance/transmittance of the ash cloud

Other uses of satellite imagery for volcano monitoring

• Hot spot detection (with IR3.9 channel)

• Determination of cloud height with VISIBLE shadow technique (with HRV channel)