With these flaws, the lack of the ten-to-one exaggeration of depth, and some measurements being taken in the dark with a flashlight, my data were only approximate. That evening I found that the bottom of the gauge sagged in the middle, leading to an even deeper measurement than the downtilt side. The gauge tilts slightly, so I took a measurement on the uptilt side and the downtilt side and calculated an average. On the morning of September 12th, the gauge was so full and heavy, with over seven inches (178 mm) of rain that I decided to stick a meter stick in the gauge to measure the rain amount, and save pouring into the inner tube for the end of the storm. The funnel and inner tube doesn’t quite fit, so, I leave the gauge open and then pour the rain into the inner tube using the funnel. I inherited it from a weather-observing neighbor who moved away. This is equivalent to how the GLOBE rain gauge measures rain: the inner tube acts like a 10x magnifying glass for the area of the rain gauge. Thus, each inch in the tube is equivalent to 0.1 inches (a tenth of an inch) of rainfall.

The inner tube’s diameter is just small enough to make the depth of rain ten times what it would be in a gauge without the tube and funnel. It has a funnel that deposits rain into an inner tube with a smaller diameter (like this one), but bigger. The gauge is the same type the National Weather Service uses. It’s also about the many possible sources of error when making rain measurements – from old rain gauges to growing trees and even, possibly, inquisitive raccoons.īy Monday morning (September 16), I had measured over 16 inches, or 405 millimeters (mm), in our backyard rain gauge from the storm which began September 10. This is the story of my attempts to measure rain during the storm.

Which brings us to the questions – How do you measure rain? And how accurate are the measurements? Even though I have done weather research for many years, during this storm I was reminded how hard it is to measure rain accurately. You also learned that rainfall amounts vary a lot. The Boulder, Colorado area received huge amounts of rain in mid-September. For more information about her research, visit Peggy’s home page.Ī guest post by NCAR scientist Peggy LeMone Peggy LeMone is an NCAR Senior Scientist who studies weather and cloud formation.

Rain measuring meter