"Rain" vs. "Drizzle"
[I was looking through Posthaste for the Why Things Are on perceptions of weather and couldn't find it, but found instead this item about raindrops. From Style, March 10, 1995.]
James and Marie Elise Underwood of Morganza, Md., ask, "Why are
raindrops sometimes heavy, fat drops that splat across the windshield,
yet other times fine, small drops that, even in a heavy rain, seem to
fall lightly?"
Dear Jimmy and Marie: We've always wondered if rain has ever come
down so hard that it was fatal. Because we think killed-by-rain would be
a really poetic way to go.
The big hairy raindrops usually come from thunderheads, those tall
cumulus clouds common in summer. The wind currents force the droplets up
and down and they grow bigger and bigger, with the biggest drops being
about the size of a pea, a fifth of an inch across, according to Allan
Eustis, a meteorologist with the National Weather Service.
The larger the drop, the greater its terminal velocity. This is not
because gravity "pulls" it harder. It's because air pressure has more
effect on a small drop. It can't cut through the atmosphere as well.
A pea-sized drop can reach a terminal velocity of about 30 feet per
second. It hits your windshield with all that force because it's big and
fast, like a pro football linebacker.
The smaller drops tend to form in horizontally organized, layered
clouds, without all the convection and turbulence and drama. A typical
raindrop is 0.06 inches, or about one-seventeenth of an inch, across. At
that size it can't go much faster than about 13 feet per second. It just
pitter-patters.
Eustis points out that raindrops aren't teardrop-shaped. They have
flattened bottoms, because of the air pressure.
"They kind of look like hamburger buns," he said.
Eustis says that if the drops are less than 0.02 inches in
diameter, the precipitation is no longer considered rain. By definition
it's drizzle. (Before you tell anyone it's drizzling outside, please
verify the droplet diameter.)
By
Joel Achenbach
|
July 18, 2005; 2:26 PM ET
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Posted by: Phil from Brussels | July 18, 2005 2:49 PM | Report abuse
I remember reading something about this. Something about how many "pixels" the eye can resolve, and the maximum "frame-rate" the eyes sample images at. And how if you break those limits, say, with film, you can make people see some pretty crazy stuff.
Posted by: jw | July 18, 2005 3:05 PM | Report abuse
This is to Phil. I don't know how long you've been in Brussels, but it was my experience in my one week there (about 14 years ago) that every afternoon at approximately 2:30, everyone would open their umbrellas to the sky, shielding themselves from the rain which would fall, shrug their shoulders and exclaim: "C'est Belge." Yep, me too.
I find this weather disgusting and am tired of my glasses fogging up whenever I disembark from my air conditioned car. I am so looking forward to complaining about winter!
Posted by: firsttimeblogger | July 18, 2005 3:10 PM | Report abuse
Hi Firsttimeblogger,
Yep, rain is a consistent part of our climate, whether it's cold or hot.
But when in summer we have a week or two without it, it just gets so hot and yukky as it has for the last 2 weeks.
But the 21st of July is comming up. (our 4th) And then the weather changes. We call it the "drash National". It normaly poures on the poor soldiers who parade in Brussels. Yep, we have an army. I personally know all five of them.
I empathise with the glasses comment, I experience the same thing.
Posted by: Phil from Brussels | July 18, 2005 3:21 PM | Report abuse
Ha, "I personally know all five of them." That was good.
My glasses fog up, too (when I wear them). Drives me crazy (on the odd occasion that I wear them). It also happens during the winter here. If you put glasses on your cold face you immediately can't see anything for the fog. Cold glasses on a warm face will do the same thing.
Posted by: Sara | July 18, 2005 3:31 PM | Report abuse
Although my husband was skeptical about this fact, plastic glasses frames don't fog up as much as metal. My knowledge comes from years of skiing and playing soccer with 4 eyes.
Something to think about. Or not.
Posted by: lamb | July 18, 2005 5:58 PM | Report abuse
The comments to this entry are closed.
I'm going to use the fact that I'm the first to post to this article to ask a question. Hopefully you read this Joel (At least I hope I'm the first maybe someone just beat me to it while I type this)
What's the resolution of our eyes? Did anyone ever do any research on that?
I understand that the rods in our eyes aren't set up in a grid like the pixels of a screen, but I wonder if there is a way to calculate how many pixels we actually see, if any.
P.S. I would like to suck up a bit by stating that I must be your first Belgian fan.
P.P.S. Over here it's muggy aswel. It sucks. Time for a good thunderstorm.