View at EarthSky Community Photos. | Bonnie Nickel in San Diego, California, USA, captured this photo of a jet contrail casting a shadow on clouds on January 3, 2021. She wrote: “This jet contrail shadow was one among several seen at this location at breakfast time today. The jets appeared to be flying straight up.” Thank you, Bonnie!
Like anything that is not completely see-through, the water vapour from jet planes, called jet contrails (NOT chemtrails), can cast shadows. These can create some interesting photo opportunities, and we show a few here, submitted by EarthSky readers. As well, even though shadow casting is normally nothing strange, the appearance of contrail shadows can at times make us scratch our heads: are they actually above the contrail or below?
View at EarthSky Community Photos. | Bonnie Nickel in San Diego, California, USA captured this photo of a shadow-casting jet contrail around mid-day on November 22, 2020. She wrote: “I just happened to be lucky enough to see this spectacular contrail and its shadow while running errands this morning.” Thanks again, Bonnie!
We wondered what light source was creating the shadow and asked an expert, Les Cowley at the great website Atmospheric Optics. On his page about jet contrails, you can read what he 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 …
In other words, he said, the jet itself and its contrail are always higher up than the shadow, which is cast on clouds below. By email, Les told us:
Contrail shadows often don’t look ‘right’ and seem as if the contrail is below the clouds. But the shadow casters – the sun and moon – always shine downwards so the shadow must be below the contrail.
Like all statements there is an exception! At sunset and sunrise rays can travel very slightly upwards to illuminate the underside of clouds. Under those circumstances however a contrail shadow would be a long way from the contrail.
And that might be the case for some of the photos showcased here. You will need to check the time the photograph was taken and the distance of the shadow to try to discern whether the shadow is below (which is normally the case) or maybe actually above the contrail!
Contrail shadow at a low sun and and an upper tangent arc (halo), captured by Don Spain of Hillview, Kentucky on January 20, 2017. He 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…” Even though the sun is low in this photograph, the shadow is not above the contrail. How do we know? You can tell by the distance of the shadow from the contrail, which is too close. Thanks, Don!
Not one, but two jet contrail shadows in an image also depicting the sun with a beautiful 22-degree halo caused by ice crystals (please don’t stare into the sun and take good care taking pictures of it). This was captured by Jüri Voit in Estonia on July 29, 2017. Thank you Jüri!
Janet Furlong in Culpeper, Virginia captured this beautiful photo of a shadow from a jet contrail, cast on clouds, on November 23, 2013. She said a cold front had moved in that day and that there was a 40% temperature difference that evening from the evening before. As for this contrail shadow, she said her dad had been fascinated by it and asked her to photograph it.
Here’s another image of a different part of the sky, on the evening that Janet Furlong captured her contrail shadow in the image above. Notice the beginnings of the contrail and shadow on the right side of this photo. Thank you, Janet!
Fern Zalin Jones sent us this photo of her with a contrail shadow in the background, atop a singing dune at Kelso Dunes in California, USA on November 11, 2017. She wrote: “That is me, triumphant!” Photo by Greg Lewis.
The other end of the contrail shadow, captured on November 11, 2017 at Kelso Dunes in California, USA. Image via Fern Zalin Jones.
Bottom line: Shadows from jet contrails often appear to be above the cloud, seemingly cast by a low-altitude bright light shining upwards. In fact, the shadow is normally cast on clouds below the jet and its contrail since the sun (and the moon) are above. View iamges submitted by EarthSky readers here.
Read more about jet contrail shadows at Les Cowley’s website, Atmospheric Optics.
This is a contrail, not a chemtrail.
Source:
https://earthsky.org/todays-image/jet-contrail-casts-a-shadow