Day Microphysics

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

Description: This RGB is useful for cloud analysis, convection, fog, and fires.

  • The visible reflectance in red approximates the cloud optical depth and amount of cloud water and ice
  • The 3.9-µm shortwave infrared solar reflectance in green gives a qualitative measure for cloud particle size and phase
  • The 10.8-µm infrared brightness temperature produces blue shading as a function of surface and cloud top temperatures (the warmer the surface, the greater the blue contribution); therefore warmer land and ocean surfaces appear blueish whereas colder cloud tops have less blue input and appear more orange and red

Coverage: Daytime only

Channels: MSG 0.8-µm VIS; 3.9-µm IR (solar reflected component only); 10.8-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)

For more information, see http://www.atmos-chem-phys.net/8/6739/2008/acp-8-6739-2008.pdf.

Advantages:

  • Can clearly distinguish between ice phase clouds at high elevations and water phase clouds at lower elevations, providing a 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

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

Links:

References:

  • Rosenfeld, D, 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, I.M. Lensky, 1998: Satellite-Based Insights into Precipitation Formation Processes in Continental and Maritime Clouds, Bull. Amer. Meteor. Soc., 79, 2457-2476.

Additional Information:

Loop:

MSG Daytime Microphysics RGB animation, 14 Aug 2003 1200 to 415
Click to play animation.

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


Example:

Daytime Microphysics RGB based on Rosenfeld and Lensky over southern Europe and northern Africa, 17 Jan 2006 1312 UTC

This daytime microphysics RGB shows a variety of important microphysics effects. Deep red indicates thick, high cloud while violet indicates lower cloud with large 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 would make it yellow). The droplet size is small and temperatures range from -5 degrees C in eastern Spain and -25 degrees C in western Spain, making it a mid-level, supercooled water cloud that is not too thick.


Exercise:

MSG Daytime Microphysics RGB west of Spain, 30 Jan 2009

This RGB shows a variety of important microphysical effects. Thick, high clouds are red while lower clouds with large water drops are magenta. Within the magenta stratocumulus to the west of Spain and France, notice the embedded streaks that are more whitish blue. These are ship tracks caused by ship exhaust, which produces local clouds with much smaller droplet sizes than the surrounding clouds. The features in green over Spain are mid-level water clouds whose small droplets have temperatures of -5ºC in eastern Spain and -25ºC in western Spain. Therefore, green indicates supercooled liquid water, a condition that can lead to aircraft icing.

What color is the post-frontal convective cloud in this RGB scene? (Choose the best answer.)

The correct answer is C.

The post-frontal convective clouds, which are orange-red, are just west of the frontal system and moving into Spain and Portugal.