Downtown Denver was covered with a stratocumulus stratiformus opacus layer yesterday morning, with the perlucidus variety visible to the East. The underside was well defined and lumpy, varying from light gray to medium gray with a dark bluish tinge. No, this was not the work of some terrorist mastermind filling the city with some kind of plague, or even an instance of the Mile City’s legendary air pollution. No, it was purely Mother Nature’s handiwork. You see, I’ve become a cloudspotter.
I didn’t have my camera yesterday, so I will show you here some cirrus clouds, looking a bit like a dove to me, with a jumbo jet and a nearly first quarter moon over the Pacific Ocean from Ocean Beach, San Francisco this July.
Actually, I’ve always loved clouds, but aside from “fair weather” cumulus, the towering summertime cumulonimbus storm clouds, and high flying cirrus ice clouds, I didn’t know my stratus from my altocumulus. That’s not to say that I can identify them with 100 percent confidence now, but I am trying.
I have a Golden Science Guide Weather book dating to my gradeschool days nearly 5 decades ago, among others, to attest to my lifelong interest. But my recent intrigue with clouds was spawned by a wonderful book, The Cloudspotter’s Guide, by Gavin Pretor-Pinney [New York, A Perigee Book, Penguin Group (USA), 2006]. If you have even a passing interest in clouds, I heartily recommend it. It has black and white charts and photos for the most part. Where some may prefer color, I actually like the black and white better, as that somehow gives it an aura of authenticity to me. (However, a new book with spectacular color photos has been released in the UK, and will be distributed in the US in November as Hot Pink Flying Saucers and other clouds — I’ll try to review it here when I have a chance to see it) Chapters begin with great illustrations in the style of woodcuts, and Pretor-Pinney’s prose is a masterful weaving of fact and storytelling in an informal as well as informational style. Here is an example:
SO WHAT EXACTLY is a Cumulus cloud? It may feel rather unsatisfying to hear that it is just water. And yet, like all clouds, that is all it is. The curious cloudspotter might therefore wonder why it looks so different from a glass of the stuff down here on the ground. The cloud’s white, opaque appearance is because the water is in the form of countless tiny droplets (well, around 350,000,000,000 per cubit feet in actual fact), each only a few thousandth of a millimetre across. And this array of innumerable tiny surfaces scatters the light in all directions, giving the cloud its diffuse, milky appearance as compared swith the single surface of a container of water. It is like the rough face of etched glass compared with a smooth pane: all the minute angled surfaces of the roughened glass make it look white as they scatter the light every which way.
Apparently always a cloud aficionado, Pretor-Pinney formed The Cloud Appreciation Society a few years ago, which now boasts nearly 10,000 members world-wide. It has a photo gallery of hundreds of cloud photos sent in by members, some of which are quite spectacular. You can peruse the online catalog for all the various types of clouds, as well as “Clouds that look like things,” “Clouds with names” — [alas! only one here], “Tuba and Twisters,” sunrises and sunsets, optical effects and more. Beware though, that you should not start this with only a little time on your hands. If you like beautiful photos, you will linger here.
Pretor-Pinney also is co-founder of The Idler, a UK magazine dedicated to the fine art of loafing! I have never seen the magazine, but the website is a hoot!
Well, yesterday morning’s brooding, lumpy gray wool blanket evolved into a more sedate, dull sheet yesterday afternoon, although tiny patches of blue broke it up to give it a little texture. And of course it rained last night. I can’t complain too much, because we can always use a little rain in our semi-arid environment. But I’m hoping for something more exciting. It’s too early for snow. But wait a minute, I need to take a look out the window — you just never know.
May you have cloudy skies!
Larry S.
P.S. Thanks to Mike Nelson and Scott Mace, two world-class meteorologists from Denver’s 7. Any errors in cloud identification are entirely mine!
I like to view clouds from inside an airplane. When you’re above them looking down is the most amazing thing. The clouds look like land, and it looks like and amazing fantasy landscape.
The noctilucent clouds we did a previous show on are really interesting. We also did one on cloud twilight zones.
Hey, Shaun, funny you should mention the thing about seeing clouds from above and imaginning a landscape, as there is a place in the book were Pretor-Pinney mentions that. In fact he spoke of a painting of clouds, which when viewed upside down looks like a landscape. There are also some good images on The Cloud Appreciation Society website that look like that when you turn them the wrong way (or stand on your head in front of the monitor!)
Larry S.
Nice post Larry! Your top picture looks like a dove to me, too …
Deborah
I love clouds too….However -
That number density of droplets seems way too high. 350 billion per cubic foot?
That’s 12.36 million drops per cubic cm(!) For a typical cloud droplet size
distribution function, you’d need a water content of something like 15000 g/m^3
to get that many droplets per cubic foot, or 30,000x what is typical.
Pretor-Pinney must mean something more like 350 *million* droplets per cubic *yard*.
Well, I’m not sure. By my quick calculation, it looks like about 125 million 20 micron droplets would equal a cubic centimeter. Of course if there were that many (packing considerations aside), it would be liquid water. But at one tenth that density it doesn’t seem that unlikely to me. However, I am not a meteorologist and make no pretensions to it. But I will pass this on to see if we can get Mr. Pretor-Pinney to comment.
Larry S.
Kirk, you are completely right! The US publishers introduced a number of numerical errors when they changed the units of measurement from the ones I used in the original UK edition. I originally gave a figure of 10,000,000,000 droplets per cubic meter in a young cumulus cloud. This might be a little high, but is more like it. Somehow, the US publishers took it on themselves to multiply this by 35 when converting it into a square foot.
I’ll tell the publishers that they have introduced an error here.
Well spotted. Many thanks for pointing it out.
Gavin Pretor-Pinney
Thanks, Gavin, I appreciate your response. I hope that maybe at some time we can have you as a guest blogger! Maybe if you were here you could help the ID the clouds from Denver today … oh, wait a minute, I just looked out the window and it is …. CLEAR again! Drat!
Larry S.
Glad to have been of some assistance.
I am an astronomer by profession, but I love the clouds (it’s rather a kind
of a love-hate relationship, if you get what I mean…) and enjoy noodling over
radiation transfer problems.
I love clouds, always have. The first thing I do when I go outside is look towards the sky. And if clouds are up there, I get a smile on my face. Guess I’m extra lucky that I married an airline pilot and spent alot of time with my head in the clouds.
Thanks for the correction. Larry, as a reality check you can ask yourself what it would be like to inhale 0.6 liters (about 2.5 cups of water) with each 6 liter lungful of air. . . . .ouch…even if it is in little microdroplets. . .
David,
That doesn’t sound like much fun, does it? Maybe unless you are a fish.
LS