Atmospheric
Optics
Siberian Optics
~ Peter Leenan captured this scene from the flight deck high over frozen east Siberia. Plate habit ice crystals in the stratus reflect the sun to form a lower sun pillar and subsun. Ghostly alto cumulus poke through the stratus.
All images ©Peter Leenan, shown with permission
This image show the thin stratus with the ground showing though in places. Care is needed not to mistake a river or lake reflection for a subsun. Check how it varies in intensity as crosses the cloud/landscape.
The circle is an artifact from the flight-deck window.
Lenticularis add to the oddness of the cloudscape.
Thanks to Ian Loxley of the Cloud Appreciation Society for cloud identification.
Pillars & Subsuns
Both are formed by reflection from plate crystals. The reflection can be external or internal from the opposite large hexagonal face. In effect, the cloud of untold millions of crystals acts as a huge mirror.
Pillars form when the crystals wobble from horizontal. Subsuns are from crystals aligned horizontal rather precisely. As here, both types can be present at once.
These plate crystals are highly idealised. Those creating pillars are large, wobbly and probably imperfect. Some will approach snowflakes in their geometry.
