Do you know how rainfall is measured? Watch the complete measurement process in this video: Average annual rainfall is an important piece of climate information – recorded by a variety of methods. Precipitation (which is usually rain but also includes snow, hail, sleet, and other forms of liquid and standing water falling on the ground) is measured in units over a specified period of time.
In the United States, precipitation is usually expressed in inches during a 24-hour period. This means that if an inch of rain fell in a 24-hour period and, theoretically, the land was not absorbed by the ground and did not fall downhill, there would be a one-inch layer of water covering the ground after the storm.
A low-tech method for measuring precipitation is to use a container with a flat bottom and straight sides (such as a cylindrical coffee can). While the coffee will help you determine if the rainfall has decreased by an inch or two, small or precise amounts of rain are difficult to measure. Now a video of a child playing with a big snake is going viral on social media. You can see it by clicking on Snake viral video.
How is rainfall measured?
Both amateur and professional meteorologists use more sophisticated instruments, also known as rain gauges and tipping buckets, to more accurately measure precipitation.
- Rain gauges often have large openings at the top for rain. The rain falls and is trapped in a narrow tube, sometimes one-tenth the diameter of the top of the gauge. Because the tube is thinner than the top of the liquid, the units of measurement are more on a ruler and accurate measurements to one-hundredth (1/100 or .01) of an inch are possible.
- When less than 1.0 inches of rain falls, that amount is known as “trace” rain.
- A tipping bucket records rain on an electronically rotating drum or electronically. It is a funnel, similar to a simple rain gauge, but the funnel leads to two smaller “buckets”. The two buckets are balanced (somewhat sight-seeing) and each hold .01 inch of water.
- When one bucket is full, the tips drop down and the rest of the bucket fills with rainwater. Each drop of the dollop forces the device to increase the amount of rain by .01 inch.
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