Thursday, December 17, 2009


The painting below shows two shadowbeams, which are slightly darker than the background sky, slanting down to the left, where they intersect a cast shadow on the floor of the Hudson Valley.

The shadowbeams above were cast by natural clouds, but they most often occur when a jet contrail aligns with the line of sight. The dark beam below is cast by a contrail that's not visible in the photo; it's to the left offscreen.

The shadow is a bar of unilluminated vapor seen edge-on. The adjoining illuminated air is a notch lighter in value. The darker beam is usually only visible when there is a light hazy sky behind it.
Previously: Sunbeams
Contrail shadow photo courtesy Atmoptical.


Mary Bullock said...

Shadow Beams!?! Who knew? What a really bizarre but beautiful piece of information - Thanks!

Whimsical Trovers said...

That is totally awesome. I've seen them before but never knew what I was looking at. Or that they had a name that sounds like something out of the Lord Of The Rings.

JP said...

Hah! What a timely post. I just used this idea today for a piece I was working on. Thanks Jim!

Jacob Collins said...

Hi Jim,

Who painted the Hudson Valley painting?


James Gurney said...

Jacob, I should have mentioned--the painting is by me.

For those who don't know the spot in the Catskills of New York state, the view from the North Lake trail that heads from the Laurel Canyon house around to Sunset point and eventually to the Catskill Mountain House site. The view is looking east over the base of Kaaterskill Clove.

Jacob Collins said...

Its beautiful, Jim. I suspected that it might be yours, but it seemed a little tighter than some of your landscapes. I'll try to find that spot next summer.


Paul Clark said...

I was recently flying to San Diego when I noticed a line on the ground that kept following us. I never thought about our contrail casting a shadow since we were so high! Thanks for the enlightenment - I was truly stumped!

Anonymous said...

Is that what this is then?

The Moon rose behind those buildings about 10 minutes after I took that picture.

James Gurney said...

20C: Yes, that looks like a shadowbeam, all right. Check out this post about the shadowbeam behind the shuttle plume: