While sitting in an Airbus cruising at 10 km above sea-level, I saw the clouds were below the plane. I thought clouds at 10 km altitude were rare already, but this webpage http://science.nasa.gov/headlines/y2008/25aug_nlc.htm
surprised me with the amazing NLCs. They are tiny ice crystals smaller than 100nm (1/4 wavelength of blue light) and exist as high as 83 km ! This altitude is the edge of space where meteors and auroras glow.
BTW, see this strange cloud pattern, captured through the glass of a car window:
發表於 2008-8-27 23:30:33
