Dear Tom,
Sometimes dew forms all night. Can it be measured? If so, how?
–Norm Victorson
Dear Norm,
The National Weather Service’s weather observation program does not include measurements of dew. However, the amount of water contributed by dew can be determined, and a variety of techniques exist to do the job, though with varying degrees of accuracy. Dew can be measured most easily and accurately by weighing it. A piece of sod (or other material representative of the soil surface in the area for which dew measurements are desired) is placed on a scale that records the weight increase as dew accumulates. Unfortunately, accurate measurements of dew are not possible in densely vegetated areas. For example, little or no dew forms under a dense forest canopy, but it does accumulate on leaves at the top of the canopy.
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Write to: ASK TOM WHY, 2501 Bradley Pl., Chicago, IL 60618 or: asktomwhy@wgntv.com
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