Helen Czerski, “Inside the Dramatic Dance of Raindrops. From drizzles to deluges, a chaotic atmospheric choreography determines the size and shape of precipitation.” (Wall Street Journal, May 2, 2024)
Spring showers can arrive with a vengeance. I was sitting in a parked car a few days ago when a light pitter-patter began on the windshield, and less than a minute later huge raindrops were smacking into the glass, creating a deafening noise and making me extremely grateful I wasn’t outside. But the droplets were falling too fast for me to really see what they were up to before they hit. That seemed like a huge shame because a rainstorm is its own kind of dance party, one with dramatic but chaotic choreography.
Rain starts as water vapor high in the sky; the individual water molecules float free of one another, mixed in with the other gases that make up the atmosphere. When the conditions are right, they condense to join a liquid water droplet or freeze solid onto an ice crystal. At the start, these solid or liquid particles are very small and just drift along with the air currents. But as they grow in mass, they start to fall. Lots of raindrops start off as ice crystals and melt as they fall into warmer air. Once all the droplets are liquid and falling, the dance really gets going.
The smallest raindrops are around two thousandths of an inch across. These baby drops are spherical because the surface tension of the liquid squeezes the total surface area to be as compact as possible. Physicists find it strange that people often draw raindrops with a pointy end at the top, because the surface tension makes sure that there are no sharp corners—they’re all smoothed out incredibly quickly. Raindrops never have points.
As more water vapor condenses on to the drops, they grow. Large drops fall faster than small ones, so the larger ones start to catch up with the smaller drops beneath them, bumping into them and coalescing to form a bigger droplet. Once the drops grow to more than 1/25th of an inch across, they start to flatten on the underside and become rounder on the top to form a shape often known as a “hamburger bun.” The bigger they get, the flatter the bun.
The real dance is in the beautiful fluid movement of the droplet shapes. When two drops collide, the water pulses and curls until the shape settles down. But the new combined droplet may also shatter immediately, sometimes stretching out into a sheet before bursting into a shower of tiny droplets. The cycle repeats itself—catch-up and coalesce, catch-up and break—on and on until the drops reach the ground. The harder the rain, the more often droplets bump into each other and the more frantic the dance.
The mix of raindrop sizes hitting my windshield was the outcome of this tussle between the drops fusing and splitting in the sky above. The more that coalescence dominates, the larger the drops get. In warm rain in the tropics, raindrops can reach a third of an inch across (although one-tenth of an inch is much more typical in most places).
Each droplet is also dancing on its own, between the interactions with others. Droplets frequently oscillate, pulsing rhythmically at a rate that depends on their size, and the bigger the droplet, the more pronounced these gyrations are. A drop one-tenth of an inch across can wobble more than 200 times every second, and the wobbling not only slows it down slightly but also makes it drift sideways as it falls.
So the next time you’re sheltering underneath an umbrella in heavy rain, make the best of it by thinking of yourself as having a front seat at a natural spectacle instead of an unwanted inconvenience in your day. Wishing the rain away won’t make it stop, so you might as well imagine the dance up above and enjoy it.
What a beautiful writing… Rain Dance. Fascinated me. I haven never read something that is beautifully expressed/explained and also is kept its interesting touches too. Yes, it is so beautiful for a Physicist, oceanographer, author, broadcaster and Associate Professor, Dr Helen Czerski (UCL Mechanical Engineering), …etc. In loved her. I will keep followe her. Dear David, you are my guide for books, music, and such an interesting things, I can’t remember, is there anything that I didn’ like. Thank you so much, Have a nice day and new week, Love, nia
Thank you Nia. I so love her description of Rain too I felt I had to share the entire essay. Thanks for your kind words. Appreciate you. Dave
science is sexy!
I second that!
It’s!!!
Ehem… I live in Wetcoast and Raincouver, David. It’s May and the rain is not any warmer.
Laughing. I hear you Maria!
Maria, this made me laugh out loud. I once lived in Toronto and when travelling, I adored Vancouver and that whole region. I then said: Well, if I wouldn‘t alread live in such a green country myself (I‘m Swiss), I could easily move to Vancouver (preferably Vancouver. Island!) and it would just like home to me. But I never heard the words Wetcoast & Raincouver….. You lucky woman! So, so true.
Thank you, Kiki. It’s a beautiful area of Canada. There is so much to explore on the island and I do love the rain.
Simply gorgeous writing, and perspective. And now I know why rain slants sideways – I thought this was just due to wind. Truly fascinating, thanks DK.
So agree Laila! All a miracle….
I love everything about a rain dance
Me too Beth!
NOTHING better than the shelter of a car during a rain storm. Luke Bryan (a country singer you most certainly don’t know or listen to) has a song….. “Rain is a Good Thing”. Listen, let me know your favorite line.
Rain makes corn, corn makes whiskey
Or….
Start washin’ all our worries down the drain?
Yes! I get this. The California Sierra Nevadas, just got hit with more beautiful snow.
So glad. We need more snow!
Smiling! Should have listened to this before going out into a heavy rain. I truly appreciate it too in a warm car – I was in places where it rained so nard that you couldn‘t see the road ahead. THEN marvelling at the wonder of rain pummeling your car is heaven! What I also can wholeheartedly recommend is taking a boat in rain. You‘re safe and sound inside and can watch the rain lashing down the windows and merging with the lake. I did that quite often in a time I wasn‘t happy – it‘s so calming, there are very few ppl on the boat and it was a fantastic free ‚shrink lesson‘….
Boat in Rain! I’ve not done that Kiki. I’ve added it to my bucket list!
I lived close to Lake Zurich – I had boats crossing the lake from my living quarters to the other side. Sometimes I’d go off, other times I’d just return ‘home’, a happier, more settled woman, a smile on the rain-washed face….
Nice!
What a transition…from the dishwasher with it’s unnatural arrangement of water spraying to…Helen Czerski, “Inside the Dramatic Dance of Raindrops. What came to me via this brilliant writing was an accompaniment from Stravinsky’s “Rites of Spring.”
A beautiful reflection! Can’t wait to experience some rain very soon!
Yes!
I keep coming back to this. Can’t get over the fact that the passage reads like poetry.
Beautiful, right. Maybe it can inspire you to write SOMETHING!
Maybe it can…
Thank you
“So the next time you’re sheltering underneath an umbrella in heavy rain” We never use umbrellas & I know rain, so up close and personal…We’ve had several inches this past week, as well as frost and today it is 90…Will be watching the Aurora B again, tonight…
Aurora B! Enjoy!!!!