Today's story comes from a long-time viewer. He set up two rain gauges side-by-side but measured a different amount of rain in each. He wanted to know which one is accurate and how to choose a good one.
We have a digital rain gauge on our studio's rooftop. Digital rain gauges like this one have a bucket inside of them that tips over when it gets full. The bucket can hold a certain amount of water. When it tips over, it triggers a switch that sends over a signal to a computer to add that amount of rainfall to its total. At our station, the sensor also calculates rainfall rate based on how long it takes between sensor tips.
That's called an automated gauge. The other one is a manual gauge, which is just a long tube. The gauge has marks on it to measure how many inches of rain have fallen. Manual gauges are the worldwide standard for measurement.
Manual or automated, location matters. You can see that our weather station is not blocked in any direction. No trees, buildings, or other objects are between it and the sky. But that's not the only reason two rain gauges can have different readings side by side.
To use a simple example, check out these two mugs. This one is short and narrow; this one is taller and wider. In general, the wider the gauge, the more accurate the measurement because it's less affected by wind blowing the rain in different directions.
Here's how you can maximize your rain gauge accuracy at home. First, choose an approved gauge. A standard one is four or eight inches wide. It includes a measuring stick, an overflow can, a collector funnel, and a measuring tube.
Then choose a good location. Your gauge should be level and as far as possible from any obstacles that could block rainfall. It should be placed to avoid wind. And it should be mounted high enough from the ground that water can't splash into it.
If you're interested in getting a rain gauge, and want to find something that meets international accuracy standards, check out CoCoRaHS- a national citizen science network of rain gauges. Meteorologists around the country - from our team, to the NWS, use this network extensively, and it's powered by home observers. They have a web page (linked above) with the specifics of what gauges they allow for their network - which is considered accurate enough to use for research and forecasting purposes.
And as always, if you've got a weather question you want answered, send us an email!
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