Description:

This product helps to distinguish between high and low clouds and can help reveal wind shear. It is very simple and easy to understand. Note that the spectral channels and color scheme are the same as those used for the nighttime visible RGB.

The product can be produced for any meteorological satellite since all carry the minimum requirement of one visible and one longwave IR channel, and most also carry at least one shortwave IR channel within the 3.5 to 4.0 µm spectral region to replace the Vis channel during nighttime.

Coverage: Daytime only, although some who generate 24-hour product loops insert shortwave infrared imagery in place of the visible channel at night for continuity.

Channels:

• Polar-orbiting and geostationay satellites:
  
  • Daytime:
    
    • Red & Green: GOES 0.6 µm Vis
    • Blue: GOES 10.8 µm IR
  • Nightime:
    
    • Red & Green: GOES 3.9 µm IR
    • Blue: GOES 10.8 µm IR

Color scheme:

• White indicates thick, cold ice clouds
• Light blue indicates cold terrain or cold, thin ice clouds (cirrus)
• Subdued yellow or green often indicates land
• Dark blue shows water
• Brighter yellow shades indicate low clouds or fog

Advantages:

• Uses the traditional visible and longwave infrared window channels that forecasters are familiar with, combining them in an optimal way to distinguish higher/colder clouds from lower/warmer clouds
• Is found on NOAA-NESDIS Web pages, making it accessible and useful for comparison to other imagery

Limitations:

• Since it only uses two channels, it is only a pseudo-RGB product and it cannot distinguish between some features of interest, such as snow cover vs. cloud, or water cloud vs. ice cloud
• Does not incorporate a water vapor channel and therefore does not show water vapor plumes

Data links:

• NOAA-NESDIS Geostationary Satellite Server, http://www.goes.noaa.gov/goes-e.html

Example:

This GOES-East (GOES-12) Vis and IR RGB shows an intense Northeaster storm over New England on April 15, 2007. High cirrus clouds appear in light blue, tracing the circulation aloft. The yellow shades highlight low-level clouds, including mountain induced wave clouds over the Virginias. Wind gusts near the time of the image are overlaid in black.

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Exercise:

In this GOES loop over the Gulf of Mexico, the RGB during the daytime is increasingly dominated by the brightness temperature signal from longwave infrared imagery as nighttime approaches.