Coverage: Daytime only, requires solar reflectance information

Channels:

• Polar-orbiting satellites:
  
  • MODIS:
    Red: 0.86 µm NIR reflectance
    Green: 3.8 µm SWIR (reflected solar component only)
    Blue: 11.0 µm IR
  • NOAA and Metop AVHRR:
    Red: 0.865 µm NIR reflectance
    Green: 3.74 µm SWIR(reflected solar component only)
    Blue: 10.8 µm IR
  • Suomi NPP and future JPSS VIIRS:
    Red: 0.865 µm NIR reflectance
    Green: 3.74 µm SWIR (reflected solar component only)
    Blue: 10.8 µm IR
  • FY-3 imagers:
    Red: 0.865 µm NIR reflectance
    Green: 3.74 µm SWIR (reflected solar component only)
    Blue: 10.8 µm IR
• Geostationary satellites:
  
  • MSG SEVIRI and future MTG FCI:
    Red: 0.8 µm NIR reflectance
    Green: 3.9 µm SWIR (reflected solar component only)
    Blue: 10.8 µm IR
  • Future GOES-R ABI:
    Red: 0.865 µm NIR reflectance
    Green: 3.90 µm SWIR (reflected solar component only)
    Blue: 10.35 or 11.2 µm IR
  • Future Himawari AHI:
    Red: 0.860 µm NIR reflectance
    Green: 3.85 µm SWIR (reflected solar component only)
    Blue: 10.45 or 11.2 µm IR
  • Future FY-4 AGRI:
    Red: 0.825 µm NIR reflectance
    Green: 3.75 µm SWIR (reflected solar component only)
    Blue: 10.7 µm IR

Color scheme:

• The surface appears in shades of blue
• Low clouds appear yellow to greenish (small droplets) to magenta (large droplets)
• High ice clouds appear deep red (large ice particles) to bright orange (small ice particles)

Advantages:

• Can clearly distinguish between ice phase clouds at high elevations and water phase clouds at lower elevations, providing a pseudo three-dimensional view of the atmosphere
• Can identify subtle microphysical variations within clouds that are not apparent on other images or RGBs
• Helps discriminate between precipitating and non-precipitating water clouds
• Can help identify severe convective clouds with strong updrafts (see also the ‘Convection’ RGB)

Limitations:

• The RGB is complicated in terms of the number and variety of colors and requires expertise to interpret it but it is a very powerful product
• Only available during daytime

Live data links:

• EUMETSAT 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, the Middle East, Africa, and North Polar Regions, http://eumetrain.org/

Additional information:

• EUMETSAT training materials:
  
  • MSG Day Microphysics RGB Interpretation Guide, http://oiswww.eumetsat.org/IPPS/html/bin/guides/msg_rgb_microphysics.ppt
  • Understanding Convective Clouds Through the Eyes of (MSG) Cloud Particle Size. http://www.rtc.dmi.gov.tr/FILES/KURS/334/DOCS/JochenKerkman3.pdf
  • MSG Channels Interpretation: Guide to weather, surface conditions and atmospheric constituents, http://oiswww.eumetsat.org/WEBOPS/msg_interpretation/index.php
  • Applications of Meteosat Second Generation (MSG) for Insights Into Cloud Processes, http://oiswww.eumetsat.org/WEBOPS/msg_interpretation/PowerPoints/Channels/cloudintroduction.ppt

References:

• Rosenfeld, D. and I. M. Lensky, 2008: Clouds-Aerosols-Precipitation Satellite Analysis Tool (CAPSAT). Atmos. Chem. Phys., 8, 6739-6753. http://www.atmos-chem-phys.net/8/6739/2008/acp-8-6739-2008.pdf
• Rosenfeld, D. and I. M. Lensky, 1998: Satellite-based insights into precipitation formation processes in continental and maritime clouds. Bull. Amer. Meteor. Soc., 79, 2457-2476.

Example 1:

Loop: This loop shows convection (in orange) erupting over northern Italy. The outflow boundary emanating from it appears in greenish yellow.

---

Example 2:

This daytime microphysics RGB shows a variety of important microphysical cloud features. Deep red indicates thick, high cloud while violet indicates lower cloud with large water drops. Notice the more whitish blue, embedded streaks within the violet stratocumulus to the west of Spain and France; these are ship tracks caused by ship exhaust that produce local clouds with much smaller particles than the surrounding clouds.

Green indicates mid-level water cloud that is not too thick (otherwise more red, indicative of ice, would make the cloud appear yellow). The droplet size is small and temperatures range from -5 degrees C in eastern Spain to -25 degrees C in western Spain, making it a mid-level, supercooled water cloud that is not too thick.

---

Exercise:

This RGB shows a variety of important microphysical cloud features. Thick, high clouds are shades of orange-red while lower clouds with smaller water drops are a greenish-blue color. The features in greenish-yellow over western Spain and along the east coast of Spain are low-level water clouds composed of smaller droplets.