As much as I enjoy Kootenay Lake, I must admit that living at the bottom of a deep valley has a disadvantage: I cannot see the green flash from home. I have seen the green flash many times from elsewhere, but never from around here.
As I haven’t seen the green flash locally, why write about it in this blog? Two reasons: a colleague just sent me questions about it (thus, the timing); I believe it could be seen locally (if the proper vantage could be found).
The green flash is, indeed, a flash of greenish light. It sometimes accompanies the low Sun (sunrise or sunset). It is real and it is photographable. Below is a picture I took of it many years ago, albeit one taken at the Coast. The island of green light seen atop this setting Sun is one of various forms the flash can take, yet this picture does show the form commonly seen around mountains. (Discussion continues below).
The Earth’s atmosphere acts as a prism to slightly separate colours. This colour dispersion would normally give the low Sun a thin red rim on the bottom and a thin blue rim on the top. However, air scatters most of the blue to the surrounding sky leaving the upper rim greenish. The green rim is too thin to be seen by the human eye in the absence of some refractive magnification. There are a few different atmospheric temperature structures which can produce the needed magnification. As noted, the picture shows the one most likely to be encountered around mountains.
The image of the low Sun appears as above when viewed through an undulating temperature inversion such as one sculpted by mountain waves. Serrations appear on the sides and seemingly move up (setting) or down (rising) the Sun. At the top of the Sun, serrations from each side join to form a small island of green light that lasts for perhaps a second—the green flash.
Around here, a mountaintop is the best place for an observer to gain the necessary unobstructed view of the Sun at the astronomical horizon. But, where is such a vantage to be found? Where locally can one get to the top of ridge or mountain by car (needed to pack tripod, lens, and camera) knowing that half of the journey will be in the dark: Kootenay Pass? Mount Buchanan? Where in the summer? Where in the winter?
I invite suggestions.
The Kootenay-Lake Website offers a discussion and more pictures of the local clouds in mountain waves, and local mirages from atmospheric refraction.
Hi Alistair
The sky is fascinating and always seems to be saying something different about the beautifull Kootenays.