Infrared satellite imagery


Hi! This is Sean from the Billings National
Weather Service Office. In this short presentation, I will talk about infrared satellite imagery
and some of its uses. As we recall from a previous video, infrared imagery measures
temperature, so the brighter the colors, the colder, and generally higher, the clouds are.
In the top two images, we have a comparison between infrared and visible satellite imagery
from the same time. In the infrared image on the top left, we see that thunderstorms
located over central Missouri and western Illinois are producing a large area of very
bright cloud tops, which means these cloud tops are very cold and extend quite high into
the atmosphere. We would not know that by looking at the visible satellite image on
the top right. The bottom picture shows an average vertical
temperature profile of the lowest 20 kilometers, roughly the lowest 12 miles, of the atmosphere.
The orange line indicates that, generally speaking, the atmosphere cools quite rapidly
through the lowest six or seven miles of the atmosphere. On average, when we reach about
7 miles above sea level, the temperature has cooled to well below -50 degrees Celcius,
equivalent to -58 degrees Fahrenheit! These very cold temperatures aloft equate to the
very bright colors we see in the infrared image on the top left.
Like visible satellite imagery, infrared imagery helps meteorologists distinguish several important
features. Here, we can see examples of five of those phenomena. In the top left image,
we can see a cold front extending from the eastern Great Lakes southwestward into northern
Kansas. Ahead of the front, there is a line of enhanced cloudiness, while behind it we
see clearing skies. A cluster of thunderstorms, with its very cold cloud tops shows up nicely
in the top middle image, while hurricanes appear as bright, swirling masses of clouds,
which we see in the top right image. In the bottom left image, we see a strong winter
storm. The brighter clouds form a comma shape, which is quite typical with a strong winter
or spring storm as clouds wrap around an area of low pressure. In the bottom right image,
large forest fires appear as dark hot spots, which are circled in red. Thanks for watching! Remember, satellite imagery
on our website can be accessed by clicking on the satellite image towards the bottom
of the main page.

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