Dust

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

Description: Based on infrared channel data, this RGB is designed to monitor the evolution of dust storms during both day and night. This is challenging because the appearance of dust changes radically from day to night.

Coverage: Both day and nighttime

Channels: MSG 8.7-µm IR; 10.8-µm IR; 12.0-µm IR

Color scheme:

  • The color of dust varies, from red for very high-level dust (quite rare), to bright magenta for low-level dust during daytime, to dark magenta for low-level dust at night
  • Thick, high-level clouds are red
  • Thin, high-level clouds are dark blue/black except in sandy areas where they are greens and yellows
  • Thick, middle-level clouds are brown
  • Thin, middle-level clouds are green
  • Low clouds are pink when the atmosphere is warm and olive green when the atmosphere is cold
  • The background appears in shades of green and blue

Advantages:

  • Can follow the evolution of dust plumes during both day and night
  • Can depict dust plumes over land and sea

Limitations:

  • The lack of solar channels can impede the detection of dust plumes, especially over the ocean; however, high-level dust clouds are always easy to detect given the large thermal contrast between elevated dust and the underlying surface
  • It’s almost always easier to detect low-level dust clouds during the day when there’s a larger thermal contrast between the land and elevated dust; this contrast is smaller at night, making it more difficult to detect low-level dust with satellite products at night

Links:

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

Loop: This animation shows how dust (in magenta) can be easy to detect, especially during daytime, and more difficult to detect at night. Higher clouds are deep red or black but can also be shades of yellow and green over sandy areas. Notice the tremendous dust storm moving through Iraq and the Persian Gulf near the start of the loop.


MSG Dust RGB  03 Mar 2004 0112 UTC showing dust at night

Example: Notice how the dust RGB identifies dust at night, something that most dust enhancements fail to do. The key is the channel differences, which help identify dust regardless of the time of day.


Exercise:

MSG-1 Dust RGB 10-09, 09-07, 0925  June 2003, 1000 UTC

In this daytime dust RGB, notice how dust looks over water (below the black arrow) vs. land (beside the white arrows). Over which surface is dust easier to detect? (Choose the best answer.)

The correct answer is B.

Infrared RGBs will always show dust better against a heated land surface than against water bodies, which radiates at a similar temperature to the dust.