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Here are photos from West of Normandy, at 7-9am after sunrise on the 14th of may, from the visible satellite. It's a bit strange that they are visible from space, they are 2-3 miles wide? Are they jet engine trails? To see the original images you can rewrite the time on these hyperlinks to 8-15 etc...

https://archives.meteo60.fr/images_sat_vis/2019/semestre1/Sat_vis_20190514-08h00.png <-hours enter image description here enter image description hereenter image description here

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  • $\begingroup$ ok, have done so. $\endgroup$ – com.prehensible May 14 at 9:01
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Under the right conditions (in a basic sense, locally high relative humidity; see also this discussion on this site regarding contrail formation), the clouds initially formed by contrails may persist for hours and spread outwards to form larger areas of cirrus cloud. Additionally, NASA's Contrail Education Project website has some specific examples here showing the evolution of contrails and associated clouds over the course of a day, with extremely similar visual properties to those shown in the question. They also provide some discussion describing how large these clouds must be compared to what a typical weather satellite "sees":

In order to be seen, a contrail must be wide enough (and long enough) to change the brightness of a satellite pixel. Each pixel covers a portion of the Earth. The size of that area is determined by the resolution of the satellite instrument. Typical weather satellites, such as you see on the news, have pixels that might be 8 km, 4 km, or 1 km on a side. To show up in such an image, a contrail must be nearly 1 km wide!

In other words, yes, they are contrails (or more accurately, persistent clouds originating from contrails) as observed by satellite.

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    $\begingroup$ @uhoh Makes sense, added as a reference to the mention of contrail formations - thanks! $\endgroup$ – dplmmr May 15 at 2:29
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    $\begingroup$ They're both great answers, thanks! $\endgroup$ – uhoh May 15 at 3:40

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