pale blue

Thin cirrus clouds over sea are pale blue in the Snow RGB images.

Meteosat, SEVIRI Snow RGB image for 07 March 2014 09:25 UTC (left) and 11 March 2015 09:10 UTC (right)

Note that thicker semitransparent ice clouds are orange even over sea.

Explanation of the colours of the thin semitransparent clouds over sea (see the recipe):

In case of semitransparent clouds the satellite measures mixed radiation consisting of the radiation emitted or reflected by the semitransparent cloud itself and the radiation originated from below and transmitted through it. That is why the colour of a semitransparent cloud depends not only on the characteristics of the cloud itself, but also on the transparency and the colour of the underlying surface.

• The colour of the almost thick semitransparent cloud approximates the colour of the thick ice clouds (orange, characterised by relatively low blue component).
• The colour of the very thin cirrus clouds approximates the colour of the underlying clouds or surface (dark blue in case of sea).
• The colour of the thin cirrus is between the colour of the thick ice cloud and that of the underlying cloud or surface. Over the bluish sea, the colour of the very thin cirrus ‘loses’ its orange characteristic.

Semitransparent ice clouds can be shown in several colours in the Snow RGB images: from orange, yellowish to pale blue colours.

The colour of the thin cirrus is in between the colour of the thick ice cloud (orange) and that of the underlying cloud or surface. Thicker cirrus clouds are orange, thin cirrus clouds can also appear orange (over thick ice clouds or snowy land), light blue (over desert), pale blue (over sea), light yellowish (over water clouds) etc. The image below shows cirrus clouds over sea and desert.

Meteosat, SEVIRI Snow RGB image for 15 March 2015 11:25 UTC

Thin cirrus looks like a yellowish, bluish veil, see the images below. The images below show thin cirrus clouds over snow, water clouds, land and sea.

Meteosat, SEVIRI Snow RGB images for 07 March 2014 09:25 UTC (left) and 24 January 2010 09:10 UTC

Explanation of the colours of the semitransparent clouds (see the recipe):

In case of semitransparent clouds the satellite measures mixed radiation consisting of the radiation emitted or reflected by the semitransparent cloud itself and the radiation originated from below and transmitted through it. That is why the colour of a semitransparent cloud depends not only on the characteristics of the cloud itself, but also on the transparency and the colour of the underlying surface.

• The colour of the almost thick semitransparent cloud approximates the colour of the thick ice clouds (orange).
• The colour of the very thin cirrus clouds approximates the colour of the underlying clouds or surface (orange, white, dark blue, red, green, light blue).
• The colour of the thin cirrus is between the colour of the thick ice cloud and that of the underlying cloud or surface.