http://joshuacolwell.com/blog/index.php/2006/pastel-clouds/ Science, astronomy, politics, movies, and various minutiae. Tue, 13 Mar 2012 23:50:00 +0000 hourly 1 http://wordpress.org/?v=3.3.2 http://joshuacolwell.com/blog/index.php/2006/pastel-clouds/comment-page-1/#comment-395 Eric Jensen Thu, 30 Nov 2006 02:00:18 +0000 http://joshuacolwell.com/blog/index.php/2006/pastel-clouds/#comment-395 The pastel (or "irridescent") cirrus clouds also seem to require strong updrafts and cold temperatures. The waves driven by flow of air over the mountains can have very strong updrafts that will drive formation of large numbers of ice crystals. Competition for vapor amongtst the large number of crystals limits there growth and keeps them small enough for the diffraction effect to work. If the clouds are high and cold, the vapor available for condensation is very limited, which further limits their growth. The wave clouds in these photos did indeed form at unusually high altitudes and low temperatures. The particles in irridescent cirrus need to be much smaller than those in typical cirrus. The pastel (or “irridescent”) cirrus clouds also seem to require strong updrafts and cold temperatures. The waves driven by flow of air over the mountains can have very strong updrafts that will drive formation of large numbers of ice crystals. Competition for vapor amongtst the large number of crystals limits there growth and keeps them small enough for the diffraction effect to work. If the clouds are high and cold, the vapor available for condensation is very limited, which further limits their growth. The wave clouds in these photos did indeed form at unusually high altitudes and low temperatures. The particles in irridescent cirrus need to be much smaller than those in typical cirrus.

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