The Week of Nice Sunsets and Sunrises
2016-08-01 20:54:02.000 – Adam Gill, Weather Observer/IT Specialist
This week on the summit has had quite the number of phenomenal sunrises and sunsets. This week we have been dominated by high pressure with weak fronts traversing through the region. The biggest reason that we had such perfect conditions for colorful sunrises and sunsets was due to the placement of a stubborn stationary front just to our south. The center of the high was anchored just off to the northwest and it was moving very dry air into the region in the mid atmosphere. High clouds were strewn overhead due to the stationary front to the south but the summits stayed in the clear as dry air was kept in place by the high. There was even some virga falling out of the high clouds that really helped show the color of the sunsets and rises.
Since it is summer time, the sun will rise in the northeast and set in the west –northwest direction. This is important because all the clouds were to the south so the sun was able to rise and set without being obscured. This morning was really an exception because there was one small break in the cloud deck off to the northeast with showers in the region that really illuminated all the colors of a sunset.
So why are there so many different colors during a sunset when during the day the sky is just blue? Well that reason is due to scattering of light in the atmosphere. During the day, visible light does not have to pass through much thickness of the atmosphere. Light will scatter out starting with smaller wavelengths and longer wavelengths will penetrate further through the atmosphere. So the colors of the rainbow go from violet to red, with violet being the shortest wavelength. Violet will get mostly scattered out even at mid-day with blue being the next most heavily scattered light. It is the reason that the sky looks blue. At sunset and sunrise, visible light from the sun has to penetrate through a much greater thickness of the atmosphere because it is entering the atmosphere at such a low angle. This causes most of the blue light to be scattered out leaving only the longer wavelengths of yellow, orange, and red left. This visible light will then be reflected off of clouds and other obscurations in the atmosphere to give us all the colors!
Adam Gill, Weather Observer/IT Specialist