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. Note that the dust RGB is nearly identical to the ash RGB but has slightly different tuning (temperature difference thresholds and enhancement of individual red, green, and blue inputs are slightly modified).

The current MODIS, MSG SEVIRI, and Suomi NPP imagers have the necessary channels to make this product. Future JPSS VIIRS, FY-3 MERSI-2, GOES-R ABI, Himawari AHI, FY-4 AGRI, and MTG FCI instruments will also have the needed channels for producing a dust RGB.

Coverage: Both day and nighttime

Channels:

• Polar-orbiting satellites:
  
  • MODIS:
    Red: 12.0 minus 11.0 µm IR BT difference
    Green: 11.0 minus 8.6 µm IR BT difference
    Blue: 11.0 µm IR
  • Suomi NPP and future JPSS VIIRS:
    Red: 12.0 minus 10.8 µm IR BT difference
    Green: 10.8 minus 8.6 µm IR BT difference
    Blue: 10.8 µm IR
  • FY-3 MERSI-2:
    Red: 12.0 minus 10.8 µm IR BT difference
    Green: 10.8 minus 8.55 µm IR BT difference
    Blue: 10.8 µm IR
• Geostationary satellites:
  
  • MSG SEVIRI and future MTG FCI:
    Red: 12.0 minus 10.8 µm IR BT difference
    Green: 10.8 minus 8.7 µm IR BT difference
    Blue: 10.8 µm IR
  • Future GOES-R ABI:
    Red: 12.3 minus 10.35 or 11.2 µm IR BT difference
    Green: 10.35 or 11.2 minus 8.5 µm IR BT difference
    Blue: 10.35 or 11.2 µm IR
  • Future Himawari AHI:
    Red: 12.35 minus 10.45 or 11.2 µm IR BT difference
    Green: 10.45 or 11.2 minus 8.60 µm IR BT difference
    Blue: 10.45 or 11.2 µm IR
  • Future FY-4 AGRI:
    Red: 12.0 minus 10.7 µm IR BT difference
    Green: 10.7 minus 8.5 µm IR BT difference
    Blue: 10.7 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 or black, except in sandy areas where they may appear in shades of are green and yellow
• Thick, middle-level clouds appear brown
• Thin, middle-level clouds appear green
• Low clouds appear pink when the atmosphere is warm and olive green when the atmosphere is cold
• Moist low levels, particularly a moist boundary layer, appear in bluish shades
• Land and water backgrounds appear 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 water surfaces

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 is almost always easier to detect low-level dust clouds during the day when there is a larger thermal contrast between the land and elevated dust; this thermal contrast is smaller at night, making it more difficult to detect low-level dust with satellite products at night

Live data links:

• EUMETSAT Available Near-Real-Time Products, http://oiswww.eumetsat.org/IPPS/html/MSG/RGB/
• EUMeTrain, a site providing daily and archived satellite imagery, model output, case studies, and training resources, covering Europe, Middle East, Africa, and North Polar Regions, http://eumetrain.org

Additional information:

• EUMETSAT training materials:
  
  • MSG Dust RGB Interpretation Guide, http://oiswww.eumetsat.org/IPPS/html/bin/guides/msg_rgb_dust.ppt
  • MSG Channels Interpretation: Guide to weather, surface conditions and atmospheric constituents, http://oiswww.eumetsat.org/WEBOPS/msg_interpretation/index.php

Reference:

Lensky I. M. and D. Rosenfeld, 2008: Clouds-Aerosols-Precipitation Satellite Analysis Tool (CAPSAT). Atmos. Chem. Phys., 8, 6739-6753.

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Exercise: