eli5 How do they calculate how many inches of rain has fallen?

Question

Where I live it does not rain a lot. When it does the news always say that it rain 1/8 of an inch or so, but I can see that my pool has increased 2 or 3 inches.

I don’t think this could be from runoff as the edges if the pool are angles away from the pool to prevent runoff from entering the pool. I have also had buckets left out where there is significantly more water than was reported.

Any reasoning for this? Could the rain vary so much that the weather station is just getting a significantly different amount of rain?

Thanks

In: Planetary Science

Answer 1

You have basically answered your own question. Rainfall can vary over surprisingly small areas, and a single weather measuring station could be providing data for a huge area.

As for how it is measured, they typically have a funnel with a set area at the top that collects the rain, and then they literally look at how deep the pool that’s collected is.