Visible/Infrared

Table describing some of the most widely used RGB products, with a sample image for the VIS / IR RGB

Description: This GOES product helps to distinguish between low and high 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.

Coverage: Daytime only, although some loops intersperse a shortwave/longwave infrared RGB at night for continuity.

Channels:

  • GOES 0.6-µm VIS (red and green)
  • GOES 10.8-µm IR (blue)
  • GOES 3.9-µm IR (red and green at night)

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
  • Yellow shows low clouds or fog

Advantages:

  • Uses the traditional visible and infrared channels that forecasters are familiar with, combining them in an optimal way
  • Is standard on many NESDIS web pages, making it a useful standard for comparison

Limitations:

  • Since it only uses two channels, it cannot distinguish between some features of interest, such as snow cover and cloud
  • Does not show water vapor plumes

Example:

GOES VIS/IR RGB for 15 Apr 2007 showing an intense Northeaster over New England

This VIS/IR RGB shows an intense Northeaster over New England. High cirrus clouds appear in light blue, tracing the circulation aloft. The yellow shows low-level clouds, including mountain-induced wave clouds over the Virginias. Wind gusts at about the time of the image are overlaid in black.


Exercise:

still of animation
Click to play animation.

In this GOES loop over the Gulf of Mexico, the RGB during the daytime is replaced with longwave infrared imagery at night.

At the beginning of the loop, the blue at the edges of the storm marks the first arrival of thin cirrus over the Gulf Coast states. Before the sun goes down, we see yellow near the storm center. What does the yellow signify? (Choose the best answer.)

The correct answer is C.

The yellow comes mainly from water droplets detected by the visible sensor. The droplets make up the eyewall surrounding the storm center.