Super-cooled Clouds (1 of 3)
At temperatures below -20 degs. C, clouds consist mostly of ice particles, while below -40
degs. C they are composed entirely of ice particles. However, between 0 degs. C and -20 degs. C, a significant number of clouds may be primarily composed of water droplets. Water droplets below 0 degs. C are supercooled, and clouds containing large, supercooled droplets can pose
an extreme hazard to aviation. During day-time, 3.9 um imagery can be used to infer droplet phase at cloud top because of differences in reflection between ice particles and water droplets, as discussed earlier in the section on emission and reflection. By using the 3.9 um imagery to identify phase, and the 10.7 um imagery to determine cloud top temperature, cloud tops consisting of supercooled water droplets may be located.
During the night-time hours, water clouds can also be distinguished from ice clouds by using
the "fog product" (see discussion on "night-time fog"). Similar to the day-time application described above, the "fog product" and the 10.7 um imagery can be used together to locate
cloud tops consisting of supercooled water at night.
The user should keep in mind that when multilayered clouds are present, locating supercooled clouds may not be possible because of other cloud decks obscuring them from the satellite's view.
Night-time and day-time examples of supercooled water identifying imagery are presented on the following display pages.
Continue or go back to the Imagery Application summary page.