Winter Sunsets

We have been having spectacular sunsets in recent days.  What a special time this has been as we turned the page on an old year and entered a new decade--a rare "blue"  moon and colorful sunsets!  Our house faces east, so the sunsets brighten our back yard and gardens.  Since our house is constructed with large and spacious windows across the back, these sunsets light up the entire house with their rich colors for a few minutes each evening.

It is a popular misconception that colorful sunsets are the serendipitous result of manmade dust and pollution.  As a scientist at NOAA says, if that were the case, then cities such as London, New York City and Los Angeles would be  would be celebrated for their twilight hues.  In fact, tropospheric aerosols (i.e. dust) do not enhance sky colors; they subdue them.  Clean air is the main ingredient in brightly-colored sunrises and sunsets.

Sunlight takes a longer path through the atmosphere at sunrise and sunset than during the middle part of the day.  Because an increased amount of violet and blue light is scattered out of the beam along the way, the light which reaches an observer is reddened.  Sunsets are red because the daytime sky is blue!

So why are winter sunsets so  frequently more spectacular than those of summer?  Air circulation is more sluggish during the summer, and the photochemical reactions which result in the formation of smog proceed more rapidly at that time of the year.  Winter sunsets are more colorful in fact because the air is circulating more briskly and the clearer air yields the brightest colors.

Enjoy this evening's sunset!  And for the full effect, click on the picture for a view that will fill your screen.