NASA Satellite Reveals Guadalupe Island Glory

June 17th, 2015 by Roy W. Spencer, Ph. D.

Anyone who has traveled on airplanes a lot has probably seen the glory (or halo) phenomenon when looking at the shadow of the airplane on the cloud deck below. A rainbow-colored circle can sometimes been seen.

But the same kind of phenomenon can sometimes be seen in color satellite imagery….but it requires the right conditions. The following image was taken yesterday, south of California (click image for full size).

Optical glory phenomenon seen by the NASA MODIS imager on 16 June 2015.

Optical glory phenomenon seen by the NASA MODIS imager on 16 June 2015.

When the sun reaches it’s northernmost extent in late June, it is almost directly over the marine stratocumulus cloud deck that often exists southwest of California. As the NASA color imagers on the Aqua and Terra satellites pass over, they are looking straight down. In the imaginary “satellite shadow” region below, under the right conditions, the glory phenomenon can be seen, but only a few time each year.

Due to the latitude of Mexico’s Guadalupe Island, and the persistent marine stratocumulus layer there, I’ve found this to be the best place to see the event. The reason the glory is elongated is that the satellite imager doesn’t actually take a 2-D photo, but scans directly under the satellite path below, basically building up an image with a bunch of narrow scans. Repeated image slices through the circular glory builds up an elongated glory.

Pretty cool.


14 Responses to “NASA Satellite Reveals Guadalupe Island Glory”

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  1. Alick says:

    Elongated glory region below. Hmm.

  2. mpainter says:

    One can sometimes spot glory effects in the clouds ( fair weather cumulus), but I would not offer an explanation, myself. By glory effect, I mean a color dispersion, not necessarily a complete halo.

  3. mpainter says:

    Alick,
    ha ha, a fallen angel?

  4. jimc says:

    A rainbow has a very wide angular radius (42 deg for blue, 40 deg for red). Seeing a full circle would require a FOV at least twice that. That seems really wide. Maybe thatís required if the satellite has a very low altitude?

    • I think I estimated 5 or more deg. angular diameter before. The satellite altitude is 700 km, and I think the glory was 50+ km wide. Wikipedia says 5 – 20 deg wide, depending on cloud drop size. Given the drop size dependence, I’ll bet the most intense examples occur with a very uniform drop size.

  5. John Smith says:

    wow … thanks

  6. jimc says:

    Hum, apparently a different mechanism from rainbows. The Wikipedia article suggested it is not well understood. Another mystery. The universe is an amazing place.

  7. KevinK says:

    Nice picture, just to be clear the “glory” is a imaging artifact caused by the satellite imaging system. It is not an actual image of actual color rings out in the atmosphere. It only happens (becomes observable) when all of the angles between the source (the Sun), the scatterer (the clouds) and the observer (the satellite camera) are aligned exactly correct (about once a year in a small location on the surface of the Earth with just the right droplet size). You could not fly around in a small plane and “see” this glory outside your plane window. It is a “virtual image”, similar to the multiple “ghost” images of the sun when a sunset was photographed with an older camera lens without multi-layer anti reflection coatings.

    Cheers, KevinK

  8. KevinK says:

    Here is only one article about “ghosts” and “flare” inside an imaging system;

    https://photographylife.com/what-is-ghosting-and-flare

    The same principles apply to satellite imaging systems, the scattered light from water droplets in the atmosphere create an additional virtual light source that is dispersed with angle depending on the wavelength (like a prism). This causes the “glory” effect.

    The fact that the satellite image is formed from “Stitched” together swaths across the imaged area stretches out the round glory into an oblong virtual image as the satellite moves across the Earth’s surface.

    Note that in some older camera lenses the “ghost” image can actually be an unfocused (blurry) image of a hexagon, pentagon or heptagon. This is an unfocused image of the mechanical “iris” which was a set of metal blades (6, 7, 8 or 9) that closed inwards to reduce the diameter of the lens “stop” or aperture. Satellites do not normally have these mechanical iris parts.

    Nothing magical to see here, but the resulting images are quite cool.

    Cheers, KevinK.

  9. dlb says:

    You can also see the aura around the shadow of your head when you walk across a dew laden lawn.

  10. Chester says:

    Dr. Spencer,

    Can you give some enlightenment on the perpetual gloom and rain that’s been occurring in western PA since early June. I haven’t been able to find any technical reasons for, or how long this pattern will last.

    Thanks

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