Nacreous Clouds - take 2
Finally another sighting of those rare nacreous clouds. More on flickr .
Comments
Is this related to the northern light effect?
No, not linked at all. Northern lights are caused by particles from the Sun, while this type of clouds is still unclear what it actually is. NASA just launched a mission to found out more about it (http://en.wikipedia.org/wiki/Aeronomy_of_Ice_in_the_Mesosphere).
Nacreous clouds or mother of pearl clouds will only be seen just after sunset or before sunrise, they form in the stratosphere at heights of between 6-18 miles when the temperature there falls below -80°C and are ‘probably’ composed of ice particles with a liquid coating of nitric acid tri-hydrate. They appear bright because they are high enough to be illuminated by the sun long after local sunset and the pastel colours arise through diffraction or interference effects in much the same way that colours appear in a film of oil on a puddle of water. Aurora borealis (northern lights) & aurora australis is the emissions of photons in the Earth's upper atmosphere & not connected to these clouds formations.
Rob Benedict (UK)
Life Line
Merge branch 'xdebug_3_5'
Merged pull request #1111
Disable 'declaration after statement' warning in zend_smart_string.h,…
Specify bicycle parkings covers
Specify street/place names to addresses
Survey housenumbers
Specify whether crosswalks have tactile paving
Specify whether roads have sidewalks
Determine whether ATM allows depositing cash
Survey if places still exist
Survey if places still exist
Specify access to places
Specify whether steps have handrails
Specify width of opening
Specify parking types
Specify whether public transport stops have tactile paving
Survey opening hours
Specify step counts
Survey tactile paving on steps
Specify whether steps have a ramp
Specify which way leads up for steps
Specify path surfaces
Specify whether there are cycleways
Created an entrance
Created a bicycle_parking

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