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
Literally they use a graduated cylinder and read how much rain collects in it. I mean, it’s a [calibrated and standardized](https://www.weather.gov/iwx/coop_8inch) cylinder but that’s essentially what it is.
Is that 1/8 the forecast, or the actual measurement taken by the weather station? And how far are you from the weather station? It’s entirely probable that the local landscape is such that you tend to get a bit more of the rain event than they do
The rain is collected in a container and the depth of water is measured. It is that simple. You need a straight sided container with the opening the same size as the base.
Yes the amount of rain can easily vary between locations (just like any weather) so you might get more or less than the nearest weather station.
Measuring rain is quite simple, just put out an empty cup and however many inches get filled up in the cup is how much rain fell, but what is also important is *where* that measurement is taken. The measurements you see on the news usually come from the closest weather observation station, which more often than not is located at the closest airport to your city. Having very accurate & up-to-date weather reports is obviously very important for take off & landings, so that’s usually what your local news casters are listening to when they are looking for weather data like the amount of precipitation that fell.
So if you happened to be located right in the brunt of a storm and got tons of rain, but the closest airport was 30 miles away on the edge of the storm, that’s more than likely what explains the discrepancy in what was reported versus what you observed.
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.
I used to wonder about this too. My dad put a Tupperware tub and a test tube (flat bottom) in the backyard when it rained. The tub had more volume, but exactly the same height! Amazing!
Until high school when I learned about dimensions.
Maybe the news is saying there was 1/8″ *in the past hour*, or *this afternoon*, whereas it’s been drizzling all day long?
But yes, the rainfall can vary in different places, of course. I live ten miles from my Sister, and I often get heavy rain while she has none, or vice-versa. The terrain is important. Air rising from hills creates heavier rain; flat areas gets less.
Finally, people (including news anchors) make mistakes.
Latest Answers