Hole Punch Clouds Above Paris

January 10, 2017


January 2017 Viewer's ChoicePhotographer: Bertrand Kulik
Summary Authors: Bertrand Kulik; Jim Foster

The photo above shows an impressive sky-scrape of the City of Light. The bright, comma-shaped features are actually ice crystals falling through holes (at top and left center) in this altocumulus cloud deck. They're commonly referred to as fallstreaks. Hole punch clouds originate when an aircraft flies through a thin, mid-level cloud deck. These clouds are typically composed of supercooled water droplets, which when disturbed by a propeller or fuselage for instance, instantly freeze, falling toward the surface. As this freezing occurs, latent heat is released, the ambient air is warmed and the undisturbed portion of the cloud, about the entry point of the aircraft, often evaporates.

Photo Details: Camera Model: Canon EOS 7D; Lens: 17-70mm; Focal Length: 17.0mm; Aperture: ƒ/11.0; Exposure Time: 0.0031 s (1/320); ISO equiv: 100; Software: Adobe Photoshop CC 2015 (Windows).