![]() A circular catchment opening for a rain gauge is the standardized shape since it presents a consistent catchment area shape to windblown precipitation independent of rain and wind direction.Ģ00 cm² catchment area rain gauges seem to be most popular worldwide among meteorological departments and have a diameter of 15.96 cm (Ø 6.28 in). The most popular size for professional meteorological use is 200 cm² which has been informally accepted as it is the minimum acceptable size with a circular opening for reasonably accurate precipitation measurement. Rain gauges are for the most part divided into the following size classes based on rain catchment opening area. Its advantage is however low maintenance and simple operation. Optical rain sensor like the RG-11 Hydreon Optical Rain Sensor is not a rain gauge and for this purpose it is the least reliable form of accumulated rain measurement with errors of up to 37% recorded by our testing. (Vaisala has quietly acknowledged this by removing the "5% “rainfall cumulative accumulation accuracy 5%*” as found on the WXT520 from the follow-on Weather Transmitter WXT530/WXT532 datasheets.) With this principle the stated 5% accuracy will be quite hard to reach outside of a laboratory and I would put it in the same category of “rain sensors” with the following RG-11. Needless to say, accumulated rain amounts are only very rough estimates based on manufacturer calibration equations. Some examples include Texas Electronics rain gauges that combine a siphon with a tipping bucket mechanism.Īcoustic precipitation measuring principle like Vaisala WXT520, WXT530 and WXT532 use is a rough estimate of rain fall rate based on the impact strength of raindrops hitting a metal surface. Since I do not have experience with siphoning rain gauges, I can only theorize that the fact that they are significantly less popular than tipping bucket rain gauges may suggest certain disadvantages in maintenance, use or cost. Siphoning rain gauges tend to have a rising error with the increase in rain intensity, much like most tipping bucket rain gauges. Practical experience has shown that maintaining them can be quite burdensome and wind induced pressure errors and vibration errors along with non-horizontal mounting errors and most significantly debris (leaves, insects, …) that falls into the weighing pan errors are a source of endless problems and frequent maintenance is a must. Weighing rain gauges have the advantage of being able to offer very high rain resolution, good rain accumulation accuracy and short term precipitation intensity measurement at least in the laboratory. Historically very popular designs include Pronamic, Davis Instruments and RainWise rain gauges among the many types. Self-emptying tipping bucket rain gauges are the most popular type of rain gauge despite having some drawbacks, many of which may be a thing of the past with the introduction of a new self-balancing tipping-bucket mechanism in the new MeteoRain line of rain gauges by BARANI DESIGN Technologies. If you would like others listed, please let us know in the comments bellow: There are many different measuring principles. Rain gauge measuring principle (rain gauge type) determines the general accuracy, reliability and maintenance requirements of the rain gauge. The correct and wrong way to mount your weather stationĪerodynamics of rain gauges and error due to wind (coming soon) WMO CIMO/TECO Guide to Instruments and Methods of Observation, 2018 edition - Volume V, chapter 6 on the Measurement of precipitation. Rain drop size and speed of a falling rain drop Rain gauge accuracy and WMO/NWS standards Practical guide to determining Rainfall Rate and Rain Intensity Error Guide to rain gauges: types, sizes, benefits and drawbacks
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