Sunrise 126: Ault Park (An Early Twilight Clear Sky Sunrise)

Ice wrinkles at Heekin Overlook against the autumn twilight sky. It was a cool 32F with 76% humidity and 8% cloud cover this morning (although I see no clouds, do you?)

Just as I’m packing it up to head home, a puffy robin perches on a branch, giving me a quick moment to snap his picture before he flies off to join his friends.

There is something that I’ve learned about the sunrise through the course of pursuing this project. It stems from the differences that I’ve found in analyzing the various “species” of sunrise. What I have found, specifically, is how different a clear sky sunrise is from a sunrise whose sky is filled with clouds. If it is particularly humid it is even more drastic because humidity tends to draw out the sunrise color evolution so a cloudy humid sunrise has most of its color display after “first light”. The clear sky sunrises, however, have a tendency to get too bright too quickly so most of the subtle color changes occur before “first light”. This is especially true on a non-humid day, where the first blast of sun light can be almost blinding! This morning’s sunrise was one of the “humid clear sky” type, so the color display was present but the sun did not immediately take on a yellow hue and instead stayed a deep shade of red as it rose up over the horizon.

The main difference about these clear sky sunrises, which dominated most of the summer mornings when we weren’t having thunderstorms, and most of the autumn mornings when we weren’t getting invasions of winter rain fronts, is that often times the best colors occur 15, 20, or even 30 minutes before the expected sunrise time. If there is even a hint of cloud activity in the sky, you can see deep purple and magenta highlights across the clouds in the upper atmosphere as early as 40 minutes before sunrise as the curvature of the earth provides a glimpse of the upcoming sunrise. The colors can start off high in the atmosphere and swing down to the horizon quickly, and they can be gone in a matter of minutes as I found out the hard way a few days ago.

So this morning I decided to get up earlier than usual since the forecast had me getting excited over the possibility of clear skies. I arrived at the overlook by 7:20am, a full 28 minutes before sunrise. I was surprised to find that the ambient light was already bright enough where I had no trouble seeing with the naked eye. In fact, I could have arrived 20 minutes earlier and still had plenty of atmospheric color shifting to watch. As I look at the sunrise calendar, I see that “Civil Twilight” started at 7:14am. I am coming to realize that this is probably a good indicator of when one should attempt to “show up” to observe the full evolution of a clear sky sunrise. Today’s sunrise was actually quite humid, evident by the “red globe” effect that the sun appeared with, rather than the “bright blinding yellow light” effect that a dry sunrise with clear skies would produce. I would even venture to say that the Nautical Twilight time of 6:41am would have been an appropriate time to show up this morning. Heck, on a completely dry day where the first light would penetrate deep into the atmosphere, the Astronomical Twilight time of 6:08am would not be a bad idea, although that would take some serious commitment.

7:23am; 25 minutes before sunrise and 10 minutes after the start of “Civil Twilight“. No, that link does not take you to a page about vampires, I promise!

Heekin Overlook, 20 minutes before sunrise

Twilight over the Little Miami River Valley. Check out the standing water down in the fertile corn fields. I’m surprised that there was no fog this morning considering that there has been 3 days of raining followed by a clear morning. But the fog must have been just around the corner given the high humidity in the atmosphere.

Twilight and the Water Tower over standing water in the valley.

First Light: Sunrise 126. These high humid sunrises are kind of funny because it isn’t like the drama-queen low-humidity sunrises that alert you of their impending arrival by presenting their region of the sky with a bright orange and yellow aura 5 or 6 minutes before they actually waltz in the door. Nope, these deep blood red humid sunrises sneak up on you. I’ll look away for a quick minute, or fill up my coffee cup, and I look up and am lightly shocked to see the tip of the sun peeking out from behind the far ridge line, without an entourage or dramatic display of color.

Sunrise 126!

A close-up of the sun rising over the Little Miami River Valley. Note the deeper reds and purples still in the sky just above the horizon, as if the sunlight can’t penetrate very far into the atmosphere. Compare this to a similar picture of a less humid sunrise.

Please stay tuned for tomorrow’s sunrise. It’s currently forecasted at 68% cloud cover, which means I could get lucky and get a dramatic sunrise for the first time in months!