Colorful contrails

Soumyadeep Mukherjee, taken from Kolkata, India

As Mukherjee was taking photos of an atmospheric sundog earlier this week, he noticed these spectacular examples of iridescent contrails. These rainbow-like contrails take on their colorful appearance when water ice droplets of similar size refract sunlight toward the ground. As can clearly be seen here, such iridescence typically results not from contrails produced by engine exhaust but from aerodynamic contrails: when the drop in pressure experienced by air flowing over the wings triggers condensation. Aerodynamic contrails form best in warm, humid air — conditions when exhaust contrails often do not form.