Head in the Clouds

Have you ever spent a lazy afternoon watching the clouds go by? University of Utah meteorologist Tim Garrett spends lots of time observing clouds, but for him it’s not a relaxing pastime; it’s his job. “I want to understand how clouds work,” he says. “They appear and disappear, they’re constantly evolving. Why?” Garrett hopes to uncover some simple principles that guide the behavior of these “ephemeral beasts.”

Garrett’s interest in the nature of clouds isn’t purely academic. Understanding the details of how clouds work is important to scientists trying to predict the future effects of climate change. As the Earth warms, clouds might act like a blanket, trapping heat in the atmosphere just like greenhouse gases do, and making the problem worse.

Or instead, clouds might act like a shield, reflecting sunlight back into space and slowing the effects of global warming. It all depends on how the clouds themselves react to a changing climate: different kinds of clouds have different effects on the atmosphere. Nobody knows which ones will dominate. But a better understanding of how clouds work might help predict what will happen in the future.

Garrett's work unraveling the mysteries of clouds takes a lot of different forms. He's done research on how pollution affects snowfall and sea-ice melting in the Arctic, on the size of ice crystals in cirrus clouds, and on the motions in clouds. He relies on data collected by satellites, airplanes, and ground-based weather stations to draw his conclusions, but he swears that one of the best sources of information is something everyone has access to: the sky outside. "I just look at the sky and there's huge amounts of information there," he says. "I look at a cloud and think, 'How much light would this reflect? What can I see through the cloud? What does the sun look like?' The most sophisticated instrument ever developed is the human eye. If you're patient, and keep your eye on the sky, you can learn a lot."

What can you notice about clouds? Check out these videos of clouds evolving, or go look at the sky outside!

Watch timelapse videos of clouds evolving!

Figuring out Fall Foliage

If you happen to go outside this month, you might notice that the trees around town are doing something predictable, yet strange: they're changing colors! Leaves fade from brilliant green to red, orange, and yellow, then droop to brown as they litter the ground. This happens ever year, but why? Where do the colors come from?

As winter approaches, the nights get longer. That signals trees to start shedding their leaves, which (unlike the twigs, branches, and trunks) aren't adapted to withstand the cold of winter. To make that happen, the tree gradually cuts off the supply of fluids to the leaves. Without a constant supply of sugars and sap, the chemicals in the plant start to change.

First, chlorophyll decays. Chlorophyll is a chemical that absorbs sunlight and turns it into energy through a process called photosynthesis; it's also what gives leaves their green color. During the spring and summer months, the plant produces lots of chlorophyll, but in the fall production slows down and what's there starts to fade.

As the amount of chlorophyll in a leaf decreases, other colors that were hidden in the leaf all along start to show up. These are the yellow and gold hues, and they're caused by a set of chemicals called carotenoids. At the same time, another set of chemicals, anthocyanins, turn the leaves red and crimson as they're produced in the leaves.

Eventually, the leaves, cut off from the fluids in the rest of the tree, dry up and fall off. They'll provide food and insulation for the tree as they decompose around it. The tree is now ready for winter!

Escaping the heat of a record-hot summer

Feel a little overheated this summer? You're not alone. The National Weather Service announced this week that Summer 2007 was the hottest summer on record in Salt Lake City. The average temperature for June, July, and August was 79.3 degrees, beating the previous record (set in 1994) of 78.6 degrees.

79.3 degrees may not seem that warm, but keep in mind that's the average temperature. Every sweltering day tugged that average temperature up, and every cool evening tugged it back down. This year, the hot days were so hot and the evenings so not-that-cool that the average ended up way above normal (by 5.4 degrees). And it's not just this year that it's been warm: five of the top seven hottest Salt Lake summers have been in the last 13 years.

Sweaty humans, high A/C bills, and melted ice cream cones aren't the only results of high summer temps. Warm weather affects all kinds of things in the natural world, including the life cycles and habitats of plants and animals. In fact, Eric Rickart and Becca Rowe, biologists here at UMNH, are using the Museum's collections to understand how things have changed over the years. They're finding out how animals react to the heat by comparing information about small mammals collected in the 1920s to new data the team is collecting now. The work is still in progress, but so far it seems like the animals are moving up higher into the mountains to escape the increasing heat. While Eric and Becca's research is in Nevada, it provides good clues to what might be happening all over the west.

So next time your thermometer reads 103 degrees, maybe it's time to make like the critters and head for the hills. I recommend making some kind plan, because I bet we're not done with off-the charts heat. Let's just hope we all keep our cool.

Other Summer 2007 records:

• In St. George, July 6th was an all-time record high minimum at 92 degrees (that means it never got cooler than that, even at night!)
  
• July was the hottest month ever recorded in Salt Lake City, with an average monthly temperature of 84 degrees (previous record was July 2003 at 83.4 degrees).
• This August tied with August 2003 for the record high monthly minimum average in Salt Lake City, at 67.8 degrees (that means it stayed really warm, even at night).
  
• The summer included 17 days that were 100 degrees or warmer, the 2nd most all-time in a summer, and 47 days over 95 degrees, which is third most all-time.
• There were 7 record-breaking daily high temperatures in Salt Lake City, on June 16, July 6, July 14, July 15, August 13, August 14, and August 16.

Did you notice any interesting changes due to this summer's warmth? How did the heat affect you?