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JennGM
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| Posted: Oct 19 2010 at 12:44pm | IP Logged
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This may be more of a math/science question. We were talking about weather in our nature club, and brought some rain gauges, and also made a homemade rain gauge.
But a question came up on how an inch is measured accurately, like what meterologists officially use. What size area or volume (I'm not sure what the geometric terms are...brain fuzzy right now, so let's say bottom of the can or jar) is needed to be able to insert a ruler and say "we got an inch of rain!".
I couldn't find a satisfactory answer, so hoping I can get some help here.
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lapazfarm
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| Posted: Oct 19 2010 at 3:59pm | IP Logged
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Since rain is measured as a function of depth alone, it does not matter what size container you use, as long as the sides are vertical and the bottom is the same size as the opening.
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Theresa
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lapazfarm
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| Posted: Oct 19 2010 at 4:04pm | IP Logged
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Here is a nice explanation of the more official method:measuring precipitation
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Theresa
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JennGM
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| Posted: Oct 19 2010 at 4:14pm | IP Logged
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lapazfarm wrote:
| Since rain is measured as a function of depth alone, it does not matter what size container you use, as long as the sides are vertical and the bottom is the same size as the opening. |
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Thank you, Theresa. That is quite helpful.
EXCEPT, how about the rain gauges that use a funnel top? I've found two different types of instructions, one either flat sided and bottomed container with a ruler, or something like a liter bottle, halved, then the top inserted so it's like a funnel. That's just one example, though. Technically the funnel wouldn't change anything?
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Jennifer G. Miller
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lapazfarm
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The funnel wouldn't change anything as long as the diameter of the top of the funnel is the same as the bottle bottom, as in the following:
If, however, your funnel top is a larger diameter than your bottom, then you just have to calibrate your scale to adjust for this difference. Makes it a bit more complicated.
(Notice how the scale changes depending on depth.)
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JodieLyn
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| Posted: Oct 19 2010 at 7:19pm | IP Logged
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what's really nice about the top larger than bottom with it calibrated to be accurate.. is that it's much easier to measure when you have low amounts of rainfall.
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JennGM
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| Posted: Oct 19 2010 at 8:21pm | IP Logged
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The visuals help so much, Theresa! Thanks for humoring my simple question.
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Jennifer G. Miller
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4Real Forums : Exploring God's Creation in Nature and Science
Topic: Rain Gauges
