Using RGBs in Different Situations

So far, we’ve seen three ways of viewing a scene that contains dust:

  • A single satellite image, such as a longwave infrared image, which depends on the thermal contrast of dust against the background
  • Channel differences (or BTDs), which sharpen the depiction of dust plumes
  • An RGB that combines the inputs from the first two options into something that’s easy to interpret

The real test of an RGB is whether it can perform in varied conditions.

Click each tab and see how the dust product does.

Two RGBs, one dust, the other natural, depicting the same scene

This dust RGB animation shows how the dust storm evolves over four days and nights. You can tell when the sun is up since the heated land appears in warmer, bluish colors. Pinks and yellows predominate during the night and then fade to a bluish color typical of land during the day. Thick, high clouds are dark red while thin, high clouds are dark blue/black. Low cloud features are shades of orange. Dust aloft is magenta.

Dust RGB animation showing the evolution of a dust storm over several days over Saudi Arabia
Click to play animation.

Notice the strong system pushing through the Persian Gulf midday through the period followed by a major dust outbreak. At what time does the dust outbreak reach the southern shore of the Saudi Peninsula? (Choose the best answer.)

The correct answer is B.

Notice how the dust pushes offshore after it reaches the coast.

still of animation
Click to play animation.

This dust RGB animation occurs over the Atlantic Ocean for nearly a week. Which of the following are evident? (Choose all that apply.)

All three choices are correct.

Several dust plumes have arisen from specific source regions over Africa. This dust moves over the ocean and eventually reaches the Americas.

Dust is usually found at middle and low levels of the atmosphere and is often obscured by higher clouds on satellite products.

Note that this dust RGB can be useful for tropical cyclone forecasting over the Atlantic Ocean because dust and the dry air that contains it tend to dampen storm strength.

Dust RGB over northern Africa overlaid with 1000-hpa winds and contours of divergence

RGBs do not by themselves provide quantitative information. But we can get this kind of information by overlaying model data.

In this example, the RGB provides the location of the dust front while the overlays provide information about the winds associated with that front and the airmass behind it.