It's ugly, but coffee can works
Feb. 18, 2003
As soon as it started raining last week, I started getting calls and notes about rain gauges. It was like you had all forgotten how they work or something. Just relax, OK? All will soon be made clear.
This one was pretty typical of the lot:
Which empty can, when placed in the same location during a non-wind-driven rainstorm, will give the most accurate rainfall measurement: a small tomato paste can, a tuna can, a 42-ounce fruit juice can or a 33-inch diameter, 32-gallon garbage can?
Geezo-peezo. Do you suppose this guy has all that stuff piled up on his kitchen table and he's just sitting there contemplating the array and wondering which one would make the best rain gauge?
The simple truth of the matter, people, is that pretty much any container with straight sides and a flat bottom is going to give you a pretty fair idea of how much rain fell on your back yard. A coffee can and a ruler would do just fine.
An empty coffee can. An empty coffee can with no lid. I've learned I have to be very specific with some of you people.
If you don't like the looks of an empty coffee can, you can buy a perfectly serviceable plastic rain gauge at the hardware store for just a few bucks.
The problem comes if you want to get really picky and record very precise rainfall amounts, and I bet some of you do. You could always get a gauge with an infrared optical measuring system, automatic emptying device and wireless transmission of its readings, but that's going to cost you a bit.
Did you know that there is such a thing as an acoustic rain gauge that they use to measure rainfall on the ocean? It analyzes the sound of raindrops hitting the surface of the sea? Isn't that cool? I wonder who thought that up.
Anyway, serious weather people use a rain gauge with wide openings and a funnel in the bottom that routes the water into a narrow tube that is calibrated to measure by hundredths of an inch. Anything less than 0.01 of an inch is a trace.
They also use a "tipping bucket" gauge in which the funnel leads to two buckets balanced like a set of scales. Each bucket holds 0.01 of an inch of water. When one side is full, it tips down and the water is dumped out and the other bucket fills. The totals are recorded electronically.
Now, if you really want to go high-tech, you'll have to get yourself a distrometer. A distrometer measures rainfall by analyzing the sizes and distributions of raindrops. I have no idea how it works and I am not inclined to find out. I suspect it does not involve a coffee can.
Reach Thompson at firstname.lastname@example.org or (602) 444-8612.