Some Color - By Request

I received a complaint that my posts have been featuring too much brown and gray.  Well, that tends to happen during the winter.  Fortunately, winter is a prime time for a wonderful atmospheric event that quickly turns a dreary day into a colorful diorama.

Most people are familiar with the fact that sunlight is made up of a broad pallet of colors, as demonstrated by passing light through a prism to reveal individual bands of color from red to violet.  As sunlight comes streaming through the atmosphere, it collides with air molecules and certain colors are deflected from the light stream.  This process is known as scattering and the scattered colors become visible.  Colors at the violet/blue end of the spectrum are most easily deflected and are broken out for us to see.  That’s what produces the blue sky.  Evening sunlight cuts diagonally through the atmosphere, so the light must travel a longer path.  By the time it reaches us, the violet and blue have already been removed from the beam to create a blue sky somewhere out west and we see the remaining colors from the red end of the spectrum. 

The scattering effect occurs each evening, but to get the best display, you need a platform upon which the show can be displayed.  That role is assigned to clouds that pick up the red and orange colors and present them for us to see.

Best condition for viewing occurs when clouds cover the sky, but don’t reach the western horizon.  The low angle of the sun allows the light to pass through the greatest distance of air and then hit the under sides of the clouds.

The back side of a storm front usually produces the best display, because there is usually a sharp delineation between the moisture laden clouds and the dry air pushing them along.

Naked winter trees backlit by the evening sky put the colorful display to best use.

Whether you get orange, red or pink is a function of the distance the light has actually traveled and the amount of scattering that occurred during the journey.

Blue Jay Barrens has been in the path of a series of clippers moving through out of Canada.  Several have passed through just at dusk and have left wonderful conditions for beautifully colored skies.

The timing isn’t always perfect.  Most of the storms have been in a hurry and sometimes drift away without putting on a show.  These sunsets have no bearing on the biological functions at Blue Jay Barrens, but they do a wonderful job of entertaining me.