Nubes iridiscentes, una rareza meteorológica
[Carta de libélula:]
Nubes iridiscentes: una de las rarezas que coleccionamos por aquí…
No confundir con las nubes noctilucentes de la alta atmósfera …
(“Lee” significa a sotavento, porque se forman a sotavento de las montañas. E “iridiscente”, porque cada gota de agua dentro de esa nube es un pequeño arcoiris.)
Invisible to the human eye, air flowing over the Rocky Mountains bobs up and down in giant waves known as lee waves. On Jan. 2nd, these waves became temporarily visible when clouds caught in the wave-pattern lit up with beautiful iridescence:
"The pastel colors were lovely and the billowing cloud shapes were quite fascinating," says photographer Harold Leinbach of Boulder, Colorado. "I took the picture using my Canon Rebel XT."
Iridescence is caused by droplets of water diffracting sunlight. We often see hints of iridescent color in ordinary clouds far from mountain ranges. Lee waves intensify the phenomenon, creating a sky-wide tableau of vivid pastel.
Atmospheric optics expert Les Cowley explains: "For brightly-colored iridescence you need cloud droplets of all the same size. You get that if all the droplets have formed at the same time and experienced the same history. Dynamic conditions inside a lee cloud are just what the doctor ordered. The clouds look stationary but inside there is a ‘factory conveyor‘ with uniform droplets formed at one end and evaporated at the other. Voila - iridescence."
Lee waves may be found downwind of all mountains–not just the Rockies. If you live in the lee, keep an eye out for pastels in the sky.
LECTURAS A LA SOMBRA DE UN COCOTERO La bitácora de poesía y cosas aledañas de ELOÍSA OTERO 
el misterio de la luz, origen del color… (dice JR), en realidad es una cuestión puramente física… (y se enreda con lo de la fragmentación…)
REUQETEMUAKSSSS
Comment by islakokotero — February 10, 2009 @ 11:53 pm