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Name: Diana
Status: other
Grade: other
Location: AL
Country: N/A
Date: 12/22/2005


Question:
How can you measure the size of a raindrop, and what is the range of the smallest to largest size of raindrop?


Replies:
Diana,

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 or more).

David R. Cook
Climate Research Section
Environmental Science Division
Argonne National Laboratory


Dear Diana-

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:

http://encyclopedia.com/html/section/rain_formationofraindrops.asp

Other links about raindrop size:

http://www.shorstmeyer.com/wxfaqs/float/float.html

(excellent article by a TV weatherman)

www.gi.alaska.edu/ScienceForum/ASF2/236.html

Wendell Bechtold, meteorologist
Forecaster, National Weather Service, Retired
Weather Forecast Office, St. Louis, MO


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