** GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing **

http://cimss.ssec.wisc.edu/goes/shortcourse/nsc_aviation1_hands_on.html



16 June 2017 - Where are you expecting turbulence?

Clear Air Turbulence (CAT) is defined as the erratic movement of air masses in the absence of visual clues, such as clouds. In this short exercise, you will see GOES-16 Visible (0.64 um) imagery, GOES-16 Clean Window Infrared Imagery (10.3 um) and Water Vapor Imagery, both lower (6.2 um) and upper (7.3 um) channels:

Visible Imagery (0.64 um) from GOES-16

GOES-16 Visible Imagery [click to play animated GIF] **Click to play** The GOES-16 Visible Animation shows units of Reflectance -- how much sunlight is reflected off of the clouds? (That is, the albedo). Where are the in-flight turbulence risks? Why do you answer that way?

Clean Window (10.33 um) imagery from GOES-16

GOES-16 Clean Window [click to play animated GIF] **Click to play** The GOES-16 Clean Window measures radiation that has been emitted from the Earth (in clear skies) or from cloud tops (over thick clouds). It is called "Clean" because very little absorption of energy occurs at this wavelength; absorption, when it happens, results in cooler brightness temperatures because the absorbed energy is then re-emitted from a higher, usually colder, part of the atmosphere

Upper Level Water Vapor (6.2 um)

GOES-16 Upper-Level Water Vapor (6.2 um) [click to play animated gif] **Click to play** The Upper Level Water Vapor channel on GOES-16 (6.2 um) is affected strongly by the absorption of atmospheric energy at that wavelength by water vapor. If there is water vapor between the emitting surface (the Earth, or a thick cloud), water vapor will quickly absorb the emitted energy, and then re-emit it from a higher (usually cooler) level. Structures in water vapor imagery -- transverse bands (that is, bands that are perpendicular to the flow) -- have been related to turbulence using legacy GOES Imagery.

Mid-Level Water Vapor (6.9 um)

GOES-16 Mid-Level water Vapor [click to play animated gif] **Click to play**"Mid-Level" Water Vapor is, as the name suggests, in between the Upper Level Water Vapor (above) and the low-level water vapor (below). That is, the information represented in the animation at the link is between the other levels. Whether or not a feature is visible in 1, 2 or all 3 water vapor animations is evidence of that feature's depth.

Low-Level Water Vapor (7.3 um)

GOES-16 Low-Level water Vapor [click to play animated gif] **Click to play**"Low-Level" Water Vapor is detected using a wavelength at which absorption of atmosperic energy is not greatly sensitive to water vapor. (It is, however, a region that is sensitive to absorption by sulfur dioxide -- so be careful using this if volcanism is active) Because water vapor is not quite so effective at absorbing energy at this wavelength (7.3 um, compared to 6.9 and 6.2 um), energy emitted at a particular level has a better chance of escaping to space where the satellite can detect it. Another way of saying that is that the computer can see farther down into the (clear) atmosphere with this wavelength than with the upper- and mid-level water vapor channels.

For Turbulence to be reported, aircraft must fly through it. And Airliners spend a lot of money trying to figure out how to avoid turbulence. Click the animation below to play the Low-Level Water vapor with turbulence reports superimposed.

Low-Level Water Vapor Infrared (7.3 um) Imagery from GOES-16, along with reports of turbulence

GOES-16 Low-Level Water Vapor and Turbulence Reports [click to play animated GIF] **Click to play** The GOES-16 Low-Level Water vapor animation at this link is overlain by pilot reports of turbulence.

Now, having identified the regions of Clear Air Turbulence based on the Pilot Reports in the animation above, ask yourself: What has caused the turbulence that was observed? Turbulence occurred near Denver, over NW Arkansas, over the deep South, over Indiana, near Chicago, and north of Green Bay! Click the following links to see individual images
VISIBLE Clean IR Upper-Level Water Vapor Mid-Level Water Vapor Lower-Level Water Vapor Lower-Level Water Vapor with PIREPs
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