Sandy deserts

Sandy deserts appear greenish yellow in the AVHRR Cloud RGB images, rocky deserts appear dark green.

The images below show desert areas.

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

AVHRR Cloud RGB image of Sahara for 23 July 2016 at 06:58 UTC

Explanation of the colours of desert areas (see the recipe):

• 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.