SEVIRI RGB Cal Module - part II

• Chapter V: Ash RGB
•  
• Physical basis
• Creating Ash RGB images
• Typical colours of the Ash RGB images
• Examples of interpretation
• Comparison with other RGB types
• Benefits and limitations
• Exercise

Benefits and limitations

The main advantage of the Ash RGB is that it shows the three major volcanic effluents (ash, sulphur dioxide and ice crystals formed from water vapour) in distinct colours, enabling users to observe them drifting from the site of an eruption.

Limitations

• Limited detection of ash and sulphur dioxide when present with ice particles (mixed volcanic clouds).
• Black cirrus can be a part of either volcanic or non-volcanic cloud systems.
• Some features in the RGB image might have similar colour as the SO₂ plume (especially at high latitudes and near the edges of the images of full Earth disk), see Figs. 6 and 10.