Water And Oceanography

Understanding Rain Drops



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Elementary school teachers everywhere should be called on the carpet and forced to change their bulletin boards and calendars. Young children everywhere have been mislead. Those cute little teardrop shaped raindrops are a sham, a ruse, and terrible inaccuracy. It's time to begin over and learn about raindrops.

A German physicist, Philipp Lenard, began his study of rain drops in 1898. A great deal of his research focused on the behavior of raindrops as they fell from the clouds. He created an innovative vertical wind tunnel so he could very the airflow and simulate atmospheric updrafts and examine the raindrops.

By adjusting the airflow rate he was able to balance a drop in the air stream. Based on his observations he was able to determine that small drops (less than .08 inches) in diameter fell as spheres. Larger drops actually deformed from the spherical shape while falling through the air. Lenard described the drops with a flattened bottom and a rounded top, like a hamburger bun. (If I ever make the April calendar, that's how my raindrops will be shaped!)

Gary England, Oklahoma City's favorite weatherman, describes a cloud as "A good mixture of liquid drops, dust, and air all just churning around like your Mom might be stirring it up in a bowl." He was speaking to an elementary school class, but it's easy to understand and accurate.

Within the cloud condensation of water vapor created tiny water droplets, less than the width of a human hair. These are much too small to break away from the cloud and be drawn to the earth by gravity in the form of a rain drop. Somehow the drops need to bump into each other and join to fall in that little hamburger bun shaped drop that decorates your umbrella. The mystery in the rain drop is how they collide in such a fast manner as to be able to build up to a rainstorm in just 15 minutes. Scientists in a controlled environment can produce rain drops, but it takes at least an hour. So what is the mixing mechanism that makes the droplets join and form raindrops heavy enough to fall? To this point it is still a debate.

Does this information help one to appreciate the mystery of the rain drop? Perhaps, and a betting man may believe that the next time one sees a thunderhead coming his way he may remember that somehow little spherical bits of moisture are joining to form the drops that will eventually bring the death of the cloud. A sense of humor will help one note that they aren't the cute little tear drop shapes he colored at school.

Reference:
www.currents.ucse.ede
www.suite101.com

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