METEOSAT SECOND GENERATION (MSG) APPLICATIONS OF METEOSAT SECOND GENERATION (MSG) RGB IMAGES: PART 06 NOT RECOMMENDED RGB COLOUR COMPOSITES Author: Jochen Kerkmann (EUMETSAT) kerkmann@eumetsat.de

NOT RECOMMENDED RED-GREEN-BLUE COLOUR COMPOSITES PART 6: NOT RECOMMENDED RED-GREEN-BLUE COLOUR COMPOSITES

Channel Selection The selection of the channels to be combined in a RGB composite should be based on the physical properties represented by the channels (e.g. IR10.8 provides cloud top temperature, VIS0.6 provides cloud optical thickness, VIS0.8 provides "greeness" of vegetation etc…) It does not make sense to combine channels that represent the same physical property!

(Cloud) Physical Properties represented by the MSG Channels VIS0.6: optical thickness and amount of cloud water and ice VIS0.8: optical thickness and amount of cloud water and ice "greeness" of vegetation NIR1.6, IR3.9r: particle size and phase WV6.2, WV7.3: mid- and upper level moisture IR8.7, IR10.8, IR12.0: top temperature IR8.7 - IR10.8: phase and optical thickness IR12.0 - IR10.8: optical thickness IR3.9 - IR10.8: optical thickness, phase, particle size IR13.4 - IR10.8: top height WV6.2 - IR10.8: top height, overshooting tops

Not Recommended Schemes for RGB Image Composites 1. 2. 3. 4. RGB 01,02,09i: although known from AVHRR, this combination duplicates the visible information. It is better to create RGB 12,12,09 instead. RGB 04i,09i,10i: also known from AVHRR (night-time), but duplication of cloud top temperature information. It is better to use the RGB 10-09,09-04,09 during night-time. RGB 07i,09i,10i: combines three times the top temperature information; the resulting image will not have many colours. It is better to use the brightness temperature differences (e.g. RGB 10-09,09-07,09). RGB 05i,08i,11i: combines three sounding channels, which are not useful for cloud observation. Again, it is better to combine these channels with other channels to get relevant physical properties (e.g 05-09 (top height); 05-06 (top height, WV structure); 06-11 (SO2 concentration)).

1. Not Recommended RGB 01,02,09 MSG-1, 13 June 2003, 14:00 UTC RGB 01,02,09i (not recommended) RGB 12,12,09i (recommended) MSG-1, 13 June 2003, 14:00 UTC

2. Not Recommended RGB 04i,09i,10i RGB 04i,09i,10i (not recommended) RGB 10-09,09-04,09 (recommended) MSG-1, 03 February 2004, 03:00 UTC

3. Not Recommended RGB 07i,09i,10i RGB 07i,09i,10i (not recommended) RGB 10-09,09-07,09 (recommended) MSG-1, 26 May 2004, 12:00 UTC

4. Not Recommended RGB 05i,08i,11i RGB 05i,08i,11i (not recommended) RGB 05-06,04-09,03-01 (recommended) MSG-1, 08 September 2003, 12:00 UTC