Wednesday, November 24, 2010

One more reason to stay indoors

I've always been fascinated by cold weather conditions for some reason. I was just reading some posts at the Weather Doctor about the coldest temperature recorded in North America: -81.4 degrees Fahrenheit (-63 Celsius) in a town called Snag in the Yukon in February 1947. At that temperature, the water in one's breath froze as soon as one exhaled, producing a hissing sound, and then a tinkling sound when the newly-produced ice particles hit the ground. Plus, a small plume remained at head level for several minutes afterwards. It reminds me of the excellent Jack London story "To Build a Fire" where the main character spits and hears it crackle and freeze before it hits the ground.

As he turned to go on, he spat speculatively. There was a sharp, explosive crackle that startled him. He spat again. And again, in the air, before it could fall to the snow, the spittle crackled. He knew that at fifty below spittle crackled on the snow, but this spittle had crackled in the air. Undoubtedly it was colder than fifty below--how much colder he did not know.

For me, though, the most bizarre aspect of the temperature was how it affected the nature of sound. The cold, combined with the still air, made sound carry much farther and hug the ground.

One of the most notable traits of the day, remembered by both Toole and Blezard, was the enhanced audibility and crystal clarity of sounds due to the denser air and absence of wind. In addition, the strong surface temperature inversion bent the sound waves back toward the surface, thus causing sounds to hug the ground.

"At 80 below, the talking of the Indians and the barking of dogs in the village could be plainly heard at the airport four miles away," recalled Blezard. "An aircraft that flew over Snag that day at 10,000 feet [3050 m] was first heard when it was over 20 miles [32 km] away. Later, when overhead, still at 10,000 feet, the engine roar was deafening. It woke everyone who was sleeping at the time, because they thought the airplane was landing at the airport."

Isn't that wild?


Anonymous said...

It was -30 C here last week. Now it's -15 C and it feels warm. I can walk around with no hat and my jacket unzipped. Now that's odd.

Jim S. said...

That kind of freaks me out. Where exactly are you?