Fog & Stratus, GeoColor

Example of a GeoColor Fog and Stratus RGB

Description: A robust, all-purpose, product for general forecaster support both day and night. Is particularly useful for detecting low clouds and fog both day and night. During the day, the clouds are superimposed on NASA’s Blue Marble image, at night, on a DMSP OLS product that shows city lights. Note that GeoColor Low Cloud is not a standard RGB but is still largely built using RGB methods.

Coverage: Day and night

Channels:

  • Daytime: 0.6-µm VIS (on NASA’s Blue Marble background)
  • Nighttime: GOES 3.9-µm IR and 10.8-µm IR (on a DMSP OLS background showing city lights)

Color scheme:

  • Clouds from the visible channel are white during daytime
  • At night from infrared data, low clouds and fog are pink and high clouds are white

Advantages:

  • Intuitive and easy-to-interpret
  • Operates 24 hours a day
  • Can detect low clouds and fog day or night

Limitations: Is sometimes a gap in low-cloud detection near sunrise and sunset because of contamination by solar radiation

Link: http://www.nrlmry.navy.mil/NEXSAT.html

Example:

2 images, one GOES IR from 31 Mar 2010 1215 UTC and a corresponding GeoColor Low Cloud over a DMSP OLS image

On the left is a nighttime GOES infrared image over Texas. As you can see, no low clouds or fog are evident. But they appear in orange in the low cloud product on the right. The yellow city lights are from the DMSP OLS background.


Loops:

GOES-East VIS/IR (Day/Night) animation, 29 Mar 2010 from 0712 to 1345 UTC
Click to play animation.

In this infrared loop, the white clouds are associated with a frontal system over the eastern seaboard, and the states of Michigan, Ohio, Kentucky, Tennessee, Alabama, and Georgia are almost cloud free. When the sun comes up and the GeoColor product switches to visible data, low clouds appear over these states. The appearance of unsuspected fog and stratus at sunrise is known as a ‘sunrise surprise.’

GOES-East VIS/IR (Day/Night) animation, 29 Mar 2010 from 0712 to 1345 UTC
Click to play animation.

This animation is the GeoColor Low Cloud product. Nighttime clouds are evident in pink. Notice how they turn white when the sequence switches to daytime.