Training Module on METOP AVHRR RGB Images

• Chapter V: AVHRR Cloud RGB


•  
• Aim
•  
• Physical Basis
•  
• How to create Cloud RGB images
•  
• Typical Colors
•  
• Examples of Interpretation
•  
• Benefits and limitations
•  
• Comparison of AVHRR Cloud and SEVIRI HRV Cloud RGBs
•  
• Exercises

Benefits and limitations

Benefits:

• This RGB type is useful during the convection period. The cores and anvils of convective clouds are easy to see.
• AVHRR Cloud RGBs visualize the cloudiness of developed fronts in an informative way.
• The color of snow-free land reflects the green vegetation fraction ('chlorophyll content'): the more green vegetation there is, the greener the pixel.
• Because the colors used are (relatively) close to the natural colors of the depicted features, this RGB type is easy to understand and convenient for the public.

Limitations:

• Low- and medium-level clouds and snow have similar colors.
• The color contrast between green vegetation and bare soil is not very high. Information on vegetation also depends on temperature.