What Goes Into a Rainfall Measurement?

Posted: October 9, 2017, 4:07 pm by mpriante


A rainy day can spoil even the simplest of tasks. Whether you're planning on going shopping, going out for a daily jog, any bout of rain can be an issue. As it turns out, whether it affects your plans or not, rainfall is beneficial in the right quantities and to the right person. A landscaper may be able to work with just a light rainy day, but a contractor paving a sidewalk or a driveway would need things to stay totally dry. Even for a gardener, knowing how much rain has fallen can impact decisions on whether to water plants or not. As you can see, it's fairly beneficial to have rainfall amounts recorded and documented. So, that raises the question… how do we measure rainfall? 

Rainfall measurements are collected using rain gauges. These devices typically have a cylindrical design made out of plastic or metal. Some are cheap while others can be quite expensive. Some personal weather stations even have digital rain gauges that can automatically measure rainfall (and empty it too!). With so many options to choose from, you don’t really *need* a fancy automated weather station to measure rain. There are even how-to guides online that’ll help you make your own rain gauge from scratch! 

Once you decide on purchasing (or making) your own rain gauge, you’ll be ready to measure rainfall when you have one. It is important to follow a few basic tips on how to take measurements and get accurate readings from your gauge:

Have your rain gauge placed in a suitable location. If it's on the ground, make sure the gauge is secure enough where it won't be knocked over, stepped on, or blown over. You could also prop it up on a wooden post or a table, keeping it above the ground. This is especially helpful if your location typically floods easily, which could contaminate your measurement. 

After it rains, it's time to check your gauge. Typically rainfall measurements are recorded to the hundredth of an inch, though if your setup only marks every half inch or every inch, you may need to estimate the number as best as you can. Buying a rain gauge with detailed measurement markings can help to alleviate the guesswork. 

And that’s a basic understanding of rainfall measuring techniques. Remember, accurate readings are not only interesting but are very useful to meteorologists and researchers. We use this type of data to help verify our forecasts and to help make better predictions in the future! 

If you’re thinking about becoming a serious rainfall (or snowfall) observer, check out the Community Collaborative Rain, Hail, and Snow Network (CoCoRaHS). They are a nonprofit community-based network of volunteers that help collect rainfall data, as well as hail and snowfall data. Because it’s non-profit, anyone can join for free and the data that they collect from users is free for the public to use as well. With more data, you can help forecasts for your area improve over time!

Associate Meteorologist
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