Janet was worried about my upcoming visit.
“I don’t know if you have heard, but we are experiencing a very dusty winter because of the lack of snow. Be forewarned that I have not started my spring housecleaning—which usually occurs just before my St. Patrick’s Day Party in March, so expect some dust in the house.”
“I promise not to bring my white gloves to Anchorage,” I assured her. “I’ll be outside most of the time anyway.”
When weather conditions in Anchorage, Alaska are just right for photographing snowflakes, I catch a jet to Anchorage and stay at Janet and Jerry’s house in the Rabbit Creek area outside of town. Cooler than the Anchorage bowl, the woodsy setting is ideal for moose and snowflake watching.
I’m easy to have around: I set up my gear on their back porch and–while the getting is good–I go back and forth to the porch, day and night, coming inside to grab a snack, pee or take a nap.
A few days before my flight, I spent some time researching the origins of snow. I’ve been curious about the white stuff for years. And as a gardener, I bow down to snow as a gardener’s best friend: It provides a protective blanket for trees, shrubs and perennials. If the ground is bare when a hard freeze claws at the earth, plants have a tougher time surviving.
So this is cool: snow crystals are not just beautiful shapes of inert frozen water. They’re alive. Okay, not quite like soil, but there is more to them that meets the eye, or camera.
Back to my friend Janet and her concern about dust, and having too much of it on the furniture. “I have tried keeping the basic horizontal surfaces clean,” she says, “but I get up in the morning and they are dusty again. Rather than ‘go crazy’, I have released on the phenomenon and just ‘walk on by’. Hope you can do the same.”
To Janet, dust is the enemy; to a snowflake, dust is a necessity.
Really? To explain, we need to understand how clouds form and how they create snow. It begins when the wind pushes a mass of warm, moist air into a different mass of air, say, a cold one. Meteorologists call this a weather front, the mixing zone or edge where two air masses collide. Precipitation, including snowfall, often occurs along such weather fronts.
If the collision pushes the warm air mass upward, then it cools, causing water vapor to condense into water droplets—countless bazillions of them. Each droplet requires a nucleus on which to condense and these are provided by particles of dust in the air. This collection of liquid droplets is what you see from earth as clouds.
So now, if the clouds continue to cool, dust plays another role in making snow. Contrary to popular belief, water droplets do not freeze immediately when the temperature dips below 32 degrees F. Rather, they remain liquid in a supercooled state. Dust provides a solid surface, a seed if you will, to jump-start the freezing process much like a pearl in an oyster forming around a bit of grit.
In a matter of minutes, the frozen droplets will grow into full-sized snowflakes and drop out of the clouds, tumbleweeding their way down to Earth. “At the center of many snowflakes, too tiny for even the microscope to see, lies a solitary speck of dust that gave the crystal its start,” says Ken Libbrecht in his “Field Guide to Snowflakes,” available through Amazon.
Share this factoid with your friends: From the time a snowflake forms, to the time it touches down in the palm of your hand, it’s about 20 minutes. Amazing.
Remember I said that snowflakes are alive and somewhat related to soil? In the January 2013 issue of the National Geographic, Stanford University microbiologist Nathan Wolfe wrote an article about bacteria called “Small, Small World.” (“They’re invisible. They’re everywhere. And they rule.”)
“Above the air we breathe,” he says, “the upper atmosphere also contains microbes, floating as high as 22 miles above Earth’s surface.” Wolfe believes they could go even higher and there is evidence that some bacteria not only tolerate high levels of ultraviolet radiation, but “some metabolize and perhaps even reproduce inside clouds.
“In fact they may play a part in the formation of snowflakes that require a nucleator, or small particle, to crystallize around.
In 2008, Brent Christner and his colleagues at Louisiana State University showed that microorganisms were “the most efficient ice nucleators present in snow.”
“That’s right,” says Wolfe, “Snow is literally alive.”
Hopefully Janet can relax now, knowing that dust has a higher purpose.