Jean-Baptiste Daban's cloud photo

Introduction

This pile-of-plates cloud display was photographed by

Jean-Baptiste Daban
Ingénieur de recherche au CNRS
Observatoire Midi-Pyrénées / Institut de recherche en astrophysique et planétologie, Toulouse

He took the picture at the observatory on Pic du Midi, in the French Pyrenees, using his Samsung SM-A426B cellphone camera. He tells me:

The location of the photographer is 42°56'12.3"N 0°08'34.1"E.
I don't know the exact altitude. Something around 2880 meters.

The camera saved the image as a jpeg file, dated 11:59:44 on Dec. 11, 2025 (in the +01.00 time zone). The field of view is 73.7 deg.

This is a reduced-size copy of the original photo, shrunk down to fit on the screen. Even at this reduced resolution, you can see how horizontally stratified the atmosphere is: flattened, nearly horizontal structure is obvious over a considerable range of heights.

Notice that there are several separate piles of plates here. Each pile has its own tilt; the individual plates in a pile are nearly parallel to one another, but slightly inclined to the local horizontal. The tilts are probably due to stratified air layers being pushed up over the mountains beneath them; this has to do with the Froude number of the flow.

Such structure is always present in the atmosphere, but it isn't usually visible. It happened to be unusually obvious at this time and place.

Here's a cropped version, shown at a larger scale: Photograph of clouds over Pic du Midi Observatory, cropped

For a very different example of such complex structure in the free atmosphere, see the green-flash pictures in this 1969 paper.

At this resolution, some digital artifacts are visible. Specifically, the camera tried to enhance the constrast, and this produced some overshoots at sharp edges, such as the dark line on the tops of several clouds (notably, the one directly above the largest dome) and at the edges of railings around the dome shutters.

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