Natural Color

Table describing some of the most widely used RGB products, with a sample image for the natural color RGB

Description: This RGB is similar to true color in that it depicts surface and atmospheric features, such as vegetated areas, deserts, clouds, and ocean. But it is made from satellites without the requisite solar channels for true color, using a combination of visible and near-infrared channels instead. Many of the features have natural-looking colors but some do not. For example, snow is cyan.

Coverage: Daytime only
                
Channels: MSG 0.6-µm VIS; 0.8-µm VIS; 1.6-µm NIR

Color scheme:

  • Low clouds are white
  • Vegetation is green
  • Deserts are reddish brown
  • Snow cover and high ice clouds are cyan

For each of the three channels, a solar zenith angle correction is recommended to make the images brighter and enhance the contrast for low sun elevations present at high latitudes and during mornings and evenings.

Advantages:

  • Does a good job of depicting many surface and near-surface features
  • Provides an intuitive and compelling view of the Earth

Limitations:

  • High ice clouds and snow cover are both cyan, making them hard to differentiate
  • Thin cirrus clouds are difficult to detect

Loop:

Global MSG natural product RGB, 20 April 2009, 0600
Click to play animation.

This loop shows the day/night terminator move across the scene, illustrating the product’s daytime-only use. The RGB is particularly useful for showing surface type, such as vegetation (green) and desert (reddish brown), and flooded areas (black).


Example:

MSG Natural Color RGB  3 Oct 2005 with an eclipse over the Mediterranean, 3 Oct 2005

Since this RGB is based solely on solar channels, we see a large shadow area over the western Mediterranean Sea where a solar eclipse is centered. Notice that high clouds are cyan; low clouds are white; vegetation is green; and bare land and desert are brownish red.


Exercise:

MSG Natural Color RGB Overlaid with ECMWF Wind Analysis 250 hPa  1 Jan 2008 1200 UTC

The cyan streak over North Africa parallels the wind direction indicated by the green wind barbs plotted for 250 hPa. Why do they align so well? (Choose the best answer.)

The correct answer is A.

The cyan in this RGB can represent either high ice clouds or snow cover. Since snow cover in extremely unlikely in this part of Africa, we must be seeing cirrus clouds.