How can you measure the size of a raindrop, and
what is the range of the smallest to largest size of raindrop?
There are a number of ways to measure raindrop size.
One is to simply put a very thin sheet of aluminum foil
(the thickness that you find in a gum wrapper) outside
and let the raindrops fall on it. The drops will make
a dent in the foil that is perhaps 50% larger than the
size of the drop. you can measure across each dent to
get an approximate idea of the droplet diameter.
You can also spread a thin layer of baking grease, like Crisco
on a piece of hard plastic or smooth wood and put it outside.
The raindrops will make a hole in the grease that is not much
larger than the raindrop diameter, which you can then measure.
These measurement techniques will work well for sparse raindrops,
not a heavy rain (which will just spread all over the surfaces).
Raindrops can be amazingly small (drizzle can be as small as
less than 0.01 inch in diameter) or very large (particularly
for melted small hail, which can be a quarter inch in diameter
David R. Cook
Climate Research Section
Environmental Science Division
Argonne National Laboratory
Clouds contain huge numbers of tiny droplets of moisture. Raindrops are
formed when these tiny droplets are enlarged, first by moisture from the
surrounding air condensing on them and then by coalescing with other
droplets during their descent. Raindrops vary in size from about 0.02 in.
(0.5 mm) to as much as 0.33 in. (8 mm) in thunderstorms. From the time they
leave the bottom of the cloud, evaporation takes place and, if the cloud is
high, the air warm and dry, and the raindrops small, so that they fall
slowly, they may evaporate completely before they reach the earth. If they
do so, the drops are called virga.
The above paragraph from encyclopedia.com. Here is the link:
Other links about raindrop size:
(excellent article by a
Wendell Bechtold, meteorologist
Forecaster, National Weather Service, Retired
Weather Forecast Office, St. Louis, MO
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Update: June 2012