Rain (Rainfall) Facts
When you listen to the weather report and hear that there is a chance for light rain or that it is currently drizzling, there is actually a scientific method for defining the terminology. Now, if the person making the report is just a local broadcaster looking out the window to render an opinion, then the definitions listed below are not guaranteed to apply, but if the forecast is coming from a certified weatherman, then there is a pretty good chance that the number of drops per second per square foot really does fall within the ranges below.|
Weather radar displays present rainfall intensity legends that report units of dBZ, which are decibels relative to "Z," with "Z" being the reflectivity factor.
| ||Number of Drops|
(per ft2 per sec)
|Diameter of Drops|
(in. per hr.)
|Light Rain||26||1.24||0.04|| |
One interesting tidbit not included in the table above is that technical difference between rain and a shower. Rain refers to precipitation from stratiform clouds like stratus and altostratus, and tend to occur over a large area for a long time. Showers originate from cumulus and cumulonimbus clouds and cover a relatively small area for a short time.
So, when somebody remarks that, "we have had a ton of rain," just how much rain is that?
Answer: 0.01 inches of rain over an acre of land equals 62,726 cubic inches, or 1.1 tons.
How fast does rain fall?
Answer: Around 30 km per hour (18.6 mph), depending on the updraft.