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At a glance

What: An illustrated talk with Gavin Pretor-Pinney, cloud book author and founder of the international Cloud Appreciation Society

When: April 11, 7-8:30 p.m.

Where: Finley Community Center

Sponsored by: Sonoma Land Trust

Tickets: $10-$15, sonomalandtrust.org/join_in/events.html

We humans live at the bottom of an ocean of air. And one of the fascinating displays this ocean creates can be found just overhead, visible for anyone, everywhere to see: the ever-changing cinemascope of clouds.

After childhood, most people tend to lose interest in the shape-shifting billows and wisps, and largely stop paying attention.

But that’s a mistake, according to Gavin Pretor-Pinney.

A warm, witty, articulate Englishman and former magazine publisher, Pretor-Pinney is author of the best-selling “Cloudspotter’s Guide” (Tarcher Perigee, 2007) and “Cloud Collector’s Handbook” (Chronicle Books, 2011).

A TED Global speaker, Pretor-Pinney has presented TV documentaries for the BBC. He’s also founder and now full-time head of an unusual organization, the international Cloud Appreciation Society.

He didn’t set out to start it –– he half-jokingly attached the title to a lecture he was asked to give in 2003. Not only was the talk well-attended, but people approached him to join, and he was forced to admit it didn’t actually exist. Now it does, with members in 94 countries. Recently, he says, the U.S. has had the fastest growing membership.

Everyone knows clouds, but understanding clouds is an ongoing challenge. Scientists are still trying to figure out why they behave the way they do, and what mechanisms drive them.

They’re deceptively complicated, and unraveling their mysteries is serious business, considering the powerful influence they have on life everywhere on Earth.

They transport and deliver essential water over vast distances, reflect intense solar heat back into space like a sunshade, and move tremendous amounts of energy around the atmosphere.

But they’re also the stuff of poets, songwriters and dreamers, a freely available source of delight, inspiration, beauty and perspective.

Pretor-Pinney manages to capture both sides, the whimsy and the natural wonder.

The Society’s website posts daily samples of sinister wall clouds, shimmering sunsets and a stunning array of the many other formations clouds adopt, captured and sent in by members from around the world.

In his TED talk and presentations, one of which is coming to Santa Rosa on April 11 at the invitation of Cloud Society members here in California, sponsored by the Sonoma Land Trust, Pretor-Pinney also rolls out images of dancing cats in sombreros, pistol-packing snowmen, and the other fun things people see in clouds overhead. He also offers tips and guides.

Why clouds?

Growing up in urban England, Pretor-Pinney remembers being 4 or 5 years old and seeing bright white clouds against the blue, wondering if he could walk on them and what they were made of.

Most people, he’s found, have similar childhood memories. In spite of other differences, watching clouds is one of the few personal experiences common to all people.

They’re seen and appreciated by humans everywhere, and probably always have been, going back into the dim recesses of time. For mariners or farmers, reading and understanding them was once a critical survival skill.

And life, in the words of the Cloud Society’s Manifesto, would be immeasurably poorer without them.

“If we’re prepared to stop and look up,” Gavin says, “they’re actually quite humbling. And it’s an entirely free way to short-circuit some day-to-day stresses and concerns.”

Inside, fluffy clouds are not much more than a collection of water drops or ice crystals. But under the influence of sunlight, atmospheric disturbances, landforms and physics, they can adopt a dizzying array of shapes and sizes.

The World Meteorological Organization’s official current Cloud Atlas lists more than 100 cloud types, though scientists usually categorize them into ten general groups.

Different types lurk at different altitudes, high or low, from the ground (fog) to no more than four miles above the surface. So it’s not far-fetched to say we live with our heads in the clouds.

David Romps studies the internal workings of clouds as an Associate Professor and Director of the UC Berkeley Atmospheric Sciences Center. He says that while science knows many of the basic facts of clouds, researchers are still discovering the details and much is yet unexplained.

For example, it’s not clear why clouds have a certain size, what speed they’ll rise, or why they clump.

That’s because, Romps said, there’s a number of dynamic forces going on in clouds all at the same time.

It all starts with water vapor. Only a 1 percent fraction of the entire atmosphere is made up of water vapor, most of it evaporated from the land or oceans by the heat of the sun. But evaporating that much vapor from liquid water takes a lot of energy.

Imagine, Romp saud, the amount of heat you have to add just to get one pot of water to boil and steam. Over hundreds of square miles of tropical ocean and jungle, the energy driving evaporation is enormous.

Once in the air, the evaporated water molecules float about until they’re chilled below a certain temperature. Then, if they bump into something like airborne particles of dust, sand, or bacteria, the vapor condenses back into liquid water, forming droplets. That’s what forms clouds.

When the droplets condense, they unleash the stored energy the water vapor collected during evaporation. That release of energy is what drives the clouds to rise, boiling, high into the atmosphere.

To put things into perspective, Romps says, the condensation in one rain cloud, one kilometer wide, releases heat at the rate of tens of gigawatts, which is faster than the entire state of California is consuming electrical energy.

Locally and around the globe, that energy drives the movement and mixing of the entire atmosphere.

The warm rising air creates areas of low pressure near the earth’s surface, and further out, pushes down cooler air, which mounds into denser, high pressure zones. As Californians know, strong lows carry and deliver dense rain and snow, while stationary high pressure can deflect rainstorms for long periods of time, producing drought.

One cubic kilometer of cloud can contain one ton of liquid water, and ten tons of water vapor.

Of course, lying on your back on the beach, the clouds look like something else entirely.

Bows and flows of angel hair and ice cream castles in the air

And feather canyons everywhere, I’ve looked at clouds that way

That’s how songwriter Joni Mitchell and singer Judi Collins captured the essence of cloud watching in song in 1968.

Seeing images in clouds is both entertaining and creative, and a peculiar ability of the human mind.

We see clouds as six-legged pigs or winged pirates in the sky due to a phenomenon known as pareidolia (pronounced par-i-DOH-lee-a). It’s a trick of the brain that also causes us to see faces on burnt toast and profiles on rock outcrops.

Astrophysicist Carl Sagan speculated it was likely an evolutionary protection: having the ability to rapidly see faces and forms amid the shadows and shapes in brush or grass would have been an asset when wolves and lions lay in ambush.

Better to interpret something incorrectly, than miss the predator.

In modern times, cloud watching is more of a relaxed form of nature immersion, or imaginative entertainment.

It’s also, as Pretor-Pinney describes it, an invitation to daydream, something our screen-obsessed culture tends to leave less and less space for. That “idle mode” we enter when we watch the sky without a time scale or running narrative, he says, is something we no longer seem to appreciate as valuable.

He notes that studies show the parts of the brain that are active while daydreaming are the same ones lit up while concentrating on a task.

“Ever-changing clouds are also an antidote cheaper than psychoanalysis, and beautiful for their own sake,” he says.

Stephen Nett is a Bodega Bay-based Certified California Naturalist, writer and speaker. Contact him at snett@californiasparks.com.

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