Colour Interpretation Guide



Cloud RGB - Recipe

Red: Channel 1 (0.63 micron)
Green: Channel 2 (0.87 micron)
Blue: Channel 4 (10.8 micron)

Thin high-level clouds

Sandy desert appears greenish yellow in the AVHRR Cloud RGB images. Rocky desert appears grey with some greenish tones.

The images below show deserted areas.


AVHRR Cloud RGB image of Sahara for 04 September 2014 at 07:58 UTC


Explanation of the colours of desert areas (see also the recipe on the left side):
• For deserted areas the VIS0.63 and NIR0.87 reflectivity values are close to each other; for sandy desert they are medium strong, while for rocky desert weaker, thus the red and green signals are medium strong for sandy desert and weaker for rocky desert.
• The blue signal (IR10.8 brightness temperature) is low during daytime as the land surface temperature is high.

As a consequence, sandy deserts appear greenish yellow (the eye is more sensitive for green than for red), while rocky deserts appear grey with some greenish tones in the AVHRR Cloud RGB images.