Rochester Hole Punch Cloud
July 09, 2010
The photo above, taken from Rochester, New York, shows what looks to be a makeshift graft to patch up a hole in the sky or an audacious arrow pointing the way. It's actually a hole punch and fall streak formed by falling ice crystals produced by a passing aircraft. In order for the punches or holes to form, the cloud deck must be quite shallow. Supercooled water droplets in a mid-level cloud layer disturbed by a propeller or jet aircraft will freeze instantly and in so doing the heat of fusion is released. This latent heat warms the air and evaporates the undisturbed portion of the cloud. The bright icy wisps, falling ice crystals, that nearly fill the punch are referred to as fall streaks.
Photo details: Camera Maker: SONY; Camera Model: DSC-R1; Focal Length: 56.7mm; Aperture: f/13.0; Exposure Time: 0.010 s (1/100); ISO equiv: 160; Exposure Bias: none; Metering Mode: Matrix; Exposure: aperture priority (semi-auto); White Balance: Manual; Light Source: Cloudy; Flash Fired: No (Manual); Color Space: sRGB