Sand and bare soil
Bare soils and deserts appear red in the Natural Colour RGB images.
The reflected solar radiation at NIR1.6 from sand and non-vegetated surfaces is stronger than reflected solar radiation in both visible channels (VIS0.6 and VIS0.8) as can be seen in the image below of the Arabian peninsula. Sandy deserts are shown in red colours.
Rocky fields and vegetationless mountains appear darker (green circles). Reflected solar radiation at 1.6 micrometer has about the same intensity over rocks than radiation measured in both VIS channels.
Natural Colour RGB for 12 September 2013 12:00 UTC
When the vegetation cover deteriorates during the hot summer months, the colour changes from green to red as can often be observed over land around the Mediterranean Sea.
Explanation of the colours of sand and bare soil in the Natural Colour RGB (see the recipe):
• Sandy deserts and bare soils reflect short wave solar radiation much stronger at 1.6 micrometer than at 0.6 and 0.8 micrometer. Therefore the red channel is dominant over the green and blue colour beam.
• For rocky deserts and mountains, the predominance of the reflected solar radiation at 1.6 micrometer diminishes so that the resulting colour is a dark red to dark grey (all 3 channels show the same intensity of reflected solar radiation).