Dear Tom,
Why are raindrops small in the winter and large in the summer?
Jensen
Dear Jensen,
Your observation is unusual but correct. The answer has to do with the very different ways in which the weather works in the colder and warmer portions of the year.
Raindrops become large only when rising currents of air, or updrafts, are strong enough to keep the drops aloft long enough for them to grow.
That brings us to the difference between summer and winter weather processes. In the warm season, strong daytime heating by sunlight heats the ground and overlying air, and the atmosphere is unstable: warm air underneath, cold air above. Given sufficient heating, warm air rises in updrafts that build into showers and thunderstorms whose powerful rising currents can support large raindrops.
In winter, sunlight is weak and provides little heat. The lower level of the atmosphere is cold, updrafts are gentle and raindrops fall before they can grow large.
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