Archive for December 20th, 2017

I have the privilege (really!) to patrol Monday morning parking lot duty from 7:15 until 7:50. On most Monday mornings there are no more than 2 or 3 cars in the parking lot when I arrive. That makes for some quiet moments to consider the day, pray about concerns, and look around. Quiet allows you to observe better. One morning I saw various seeds under the trees: Bald Cypress cones, acorns, and Sweet Gum balls. Another morning I saw oak leaves of various sizes and broadness on the ground. Looking up into the tree I could see that smaller ones generally came from the top of the tree and larger ones from the bottom. These larger ones are called shade leaves. They are competing for the sparse sunlight in the shade cast by the rest of the tree. Yet a third morning I spied leaves popping up a few at a time in the direction from one bush to another. I kept watching and every 5 to 10 seconds the leaves would pop up an inch or so. After every few minutes the movement of the leaves would retrace the path back toward the first bush. I concluded that I was seeing a mouse or other vermin forging a tunnel just under the leaves and mulch on this frosty morning.

Speaking of frost, the very next week the morning was even colder, around 27 degrees (-2.8 degrees Celsius). As I approached my usual vantage point for watching cars, students, and nature, I saw that the golden brown Bald Cypress needles had fallen to the ground in the last week and this morning were fringed in frost. I went to investigate and caught a hold of an early arriving former student, requesting that he snap a picture and e-mail it to me (gonna have to get one of them new fangled smart phones one of these days).

Bald Cypress needles

The most Exquisite Lace

I retreated back to my self-appointed post. Still there were but few cars in the lot and none nor no one stirring. I glanced over toward the frosted needles once or twice. Then between two bushes I spied a curious sight about which I was at first incredulous. In fact, a few minutes later a student came to pass my way and I requested the use of her young eyes to see if she would see what I think I was yet seeing. She confirmed that there were indeed the appearance of heat waves between the bushes. Imagine, heat waves on a frosty morning! She went on and I was left standing to contemplate how this could be. Moments later a small breeze kicked up and the waves were gone. That only served to confirm my belief that they had been heat waves.

Heat waves are caused by varying densities of fluid (air in this case) refracting light passing through them. Usually the warmer fluid is rising, forming a convective cell. As it randomly snakes upward the background images are gently contorted by the light passing through the foreground fluid.

But what was forming the heat waves? As my eyes scanned the parking lot and Cypress needles, it seemed to me that the frost was heavier during the short period I had been standing there. That may have only been to my sight because of the increasing light as the sun rose, but it brought a possibility to mind. When frost forms, water vapor in the air turns directly into solid ice crystals on the grass or windshield. This process is called deposition, which is the opposite of sublimation, and skips the liquid state going either way. The heat given off by changing from gas to liquid and liquid to solid is about 8 times more than the heat given off by the same amount of liquid water cooling from 100 to 0 degrees Celsius. Needless to say, a significant amount of energy is given off by the deposition of frost. Frosty heat waves, that is shimmering amazing.*

*If my conclusion is correct







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