Colour Interpretation Guide


thick clouds

date
NPP VIIRS

length
True Colour RGB - Recipe

author
Red: VIS0.67
Green: VIS0.55
Blue: VIS0.49

Thick Clouds

Thick clouds usually appear white in the VIIRS True Colour RGB images. The images below show some examples.

thick clouds
NPP, VIIRS True Colour RGB image for 25 October 2018, 12:24 UTC

low clouds
NPP, VIIRS True Colour RGB image for 28 September 2018, 10:49 UTC

low clouds
NPP, VIIRS True Colour RGB image for 30 October 10:49 UTC

Note that:
• The colour brightness depends not only on the cloud characteristics but as well as on the solar and satellite viewing directions. Towards the edge of the swath the whitish colour may be saturated white, while along the sub-satellite track it might be slightly darker.
• Snow and ice appear also white.
• Thin clouds and high concentration aerosol plumes appear greyish.

Explanation of the colour of thick clouds in the True Colour RGB (see also the recipe on the left hand side):

The cloud elements strongly scatter the visible radiation and the absorption of visible radiation within the cloud is very low. For thick clouds the reflectivity values are high (close to 100 %) and similar in the tree visible channels. As a consequence, thick clouds appear (almost) white in the True Colour RGB.