Training Module on METOP AVHRR RGB Images

• Chapter III: METOP AVHRR Day Microphysics RGB


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• Aim
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• Physical Basis
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• How to create METOP AVHRR Day Microphysics RGB images
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• Typical Colors
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• Examples of Interpretation
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• Benefits and limitations
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• Comparison with SEVIRI Day Microphysics RGB images
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• Exercises

METOP AVHRR Day Microphysics RGB

EUMETSAT's recommendation for Microphysics RGBs is that the red component should be used for information on cloud thickness, the green one for microphysical information, and the blue one for temperature.

The METOP AVHRR instrument only uses one microphysical channel during daytime (NIR1.61), which means it can only be used to create Day Microphysics RGBs.

The Meteosat SEVIRI instrument uses two channels that provide microphysical information during daytime: NIR1.6 and IR3.9. The SEVIRI standard Day Microphysics RGB uses IR3.9 channel data since it is more sensitive to cloud top particle size than NIR1.6 data.

METOP AVHRR Day Microphysics RGB images are created by combining data from three different channels. The 0.87 micrometer channel (NIR0.87) is visualized in red, the 1.61 micrometer channel (NIR1.61) in green and the 10.8 micrometer channel (IR10.8) in blue. It is a daytime RGB since it uses shortwave channels.

Aim

The aim of this RGB type is to provide general cloud analysis with good color contrast between different cloud types and between clouds and the surface. It contains information on cloud thickness, cloud top phase, particle size and cloud top temperature.