Contrail shadow

Contrail shadow and tangent arc by Don Spain on January 20, 2017.

Don Spain of Little Bear Mobile Observatory in Hillview, Kentucky wrote:

My sky spotter Nancy called me from downtown and said I should check the sky for possible sundogs. I am well south of her location and did not see any sundogs, but saw two different atmospheric phenomena.

The most obvious is the shadow of the jet contrail on the clouds…

Don also mentioned that the shadow was “higher than the clouds.” In fact, it’s not. On his page about jet contrails, Les Cowley at the great website Atmospheric Optics said:

Contrail shadows sometimes appear counter-intuitive. [They may seem to be cast] by a low altitude bright light shining upwards and casting the contrail shadow on a higher cloud.

The reverse is the case …

Les also confirmed to me by email that the jet itself and its contrail are always higher up than the shadow, which is cast on clouds below.

But back to Don’s photo. He captured another, very delicate sky phenomenon, called a tangent arc. It’s very near the center of Don’s photo, near the bottom of the image, and appears slightly concave with respect to the sun: a little arc of light. Don said he showed the arc in the photo to a couple of local weathermen, and and they both agree it is a tangent arc.

Contrail shadow and tangent arc by Don Spain on January 20, 2017.

Bottom line:

Read more about jet contrail shadows at Les Cowley’s website, Atmospheric Optics.

This is a contrail, not a chemtrail.

from EarthSky http://ift.tt/2jsIZ2i