What Kind of Rain Gauges Should I Use to Build My Precipitation Monitoring Network?

Rain gauge networks play a crucial role when it comes to community safety, water resource management, and scientific research. Whether you’re a meteorologist, floodplain manager, or farmer, you need to know how much rain you’re getting and where with as much accuracy as possible.

Moving forward, we’ll explore different kinds of rain gauges and sensors you can use to build a network and the strengths and weaknesses of each, including:

• Standard rain gauges
• Tipping bucket rain gauges
• Weighing precipitation sensors

And answer some related questions, like…

• What is a siphoning gauge? Do I need one?
• Do I need heated rain gauges?
• Do I need wind screens for my gauges?
• What is a disdrometer? Do I need one?
• What else do I need to build a great network?

Comparing different rain gauges

Whether you’re designing a new gauge network or expanding an existing one, it’s important to select the right hardware so you can build a system that fits your budget while allowing for maximum station density and data quality.

Standard rain gauges

A standard rain gauge is a lot like the consumer tube gauge you might see in someone’s garden, except it’s much bigger and designed for scientific accuracy. A collection cylinder sits inside a larger container, where it’s fed by a funnel. When it rains, water enters the funnel and fills the cylinder until someone comes, confirms the rainfall using a measuring stick, and empties the gauge.

(Photo by Famartin)

The National Weather Service Standard Rain Gauge (SRG) can collect up to 20 inches of rain for verification with human measurement.

If the cylinder fills, any overflow falls into the outer container, where it can be collected and manually measured later. Of course, that begs the question: What happens if you open the gauge and the outer cylinder is also full? Well, that means you maxed out the system.

That design flaw means that standard rain gauges need to be monitored and emptied judiciously. If the device becomes full or leaks, your ability to measure with precision goes out the window. With that said, standard gauges can still be part of an effective precipitation monitoring network and are certified for National Weather Service research.

Tipping bucket rain gauges

In the field, tipping buckets may look like standard gauges to the untrained eye, but what’s going on inside is why they remain the gold standard for precipitation measurement. Water enters through an opening in the top and is funneled down onto a pivoting spoon (single tipper) or teeter-totter (double tipper).

The High Sierra Model 2408-00 is a double tipper with a teeter-totter shaped bucket.	The Davis Instruments Aerocone Rain Collector uses a single spoon-style tipping bucket.

Basically, the tipping bucket method breaks down to multiplication. A given volume of rainfall tips the bucket, and the device keeps track of how many times the bucket has tipped. So, in a way, the tipping bucket method isn’t directly measuring rainfall; it’s tracking how many times a mechanical process occurs. That means tipping bucket rain gauges will almost always experience some degree of undercount for a couple of reasons:

1. The device doesn’t count whatever amount of precipitation below the tipping threshold is still in the chamber at the end of the storm.
2. Water continues to flow through the funnel during the tipping process. That means water can splash or spill away from the collection area during the tip.

The good news is that because those limitations are so well understood, there are formulae that you can apply after the fact to correct the data with a high degree of accuracy. That’s one of the reasons why tippers are still the foundation of most networks: they get the job done, and even if the data isn’t perfect, there are plenty of ways to adjust it so it’s still valuable.

Weighing precipitation gauges

A weighing precipitation gauge does exactly what its name suggests – it measures rainfall by weight instead of volume (like the standard gauge) or process (like the tipping bucket).

When it rains, precipitation falls into a collection chamber, as with other types of gauges mentioned above. The device weighs the contents of the collection cup at a fixed interval, records that information, and then empties to ensure the chamber never overflows.

The LAMBRECHT meteo rain[e] weighing precipitation sensor also includes a traditional tipping bucket to get the best of both approaches.

Weighing gauges also enable you to quantify the amount and rate of all types of precipitation with a high degree of accuracy – including frozen rain, snow, and sleet. Frozen precipitation can gum up the funnel systems and small chambers that feed most rain gauges, but a weighing system (especially a self-heating one) can easily turn that precipitation into accurate, useful data.

What’s a siphoning gauge?

Any of the rain gauges we mentioned above could also incorporate an internal siphon, although they’re most common for tipping buckets. Siphons regulate water as it flows through the system to prevent the gauge from becoming overwhelmed by intense rainfall. If you operate in a region of the world with moderate to high rainfall intensities, then siphoning is a needed option to maintain the best accuracy for your gauge.

When a siphon works correctly in a tipping gauge, it ensures that each tip represents exactly the calibrated amount and gives the bucket a chance to reset without missing any rain, improving overall data accuracy. If the siphon fails, however, it can lead to a backed-up collection funnel or “double-tipping,” both of which significantly decrease the reliability of the gathered data.

What’s a heated gauge?

If you work in an area where it’s important to measure snow and ice with accuracy, heated sensors are the way to go because they eliminate freeze-up, which means you’ll never “miss” a storm because collection wasn’t possible. On the other hand, if freezing temperatures are rare in your area or you’re not concerned with snow and ice, you likely don’t need heated rain gauges.

Some heated sensors achieve this by circulating liquid ethylene glycol (antifreeze) through the unit, while others use electric heating elements, which draw additional power and increase the complexity of the installation.

With that said, heated gauges bring their own unique challenges that you may have to account for. Electric heating creates flux that can actually push small, light snowflakes away from the collection funnel, reducing data accuracy during light storms. On the other hand, heavy, clumpy snow can overwhelm systems that rely on ethylene glycol. That’s why, if you do need heated gauges, it’s important to understand your measurement goals and area very well.

Do I need windshields for my rain gauges?

Wind and rain often go hand-in-hand, but wind and precision precipitation measurement do not. All rain gauges are designed for precipitation that’s falling downward, and blown horizontal rain cannot be captured accurately by any device.

Windshields (alternatively called “wind shields” or “wind screens”) physically protect the area around the mouth of the gauge by surrounding it with panels, leaves, or staves to minimize water blowing out of the intake and keep horizontal gusts away from the device. They’ve also been proven effective for snowfall monitoring campaigns.

If you’re managing an area that’s known to be gusty and data accuracy matters, you should consider shields for your gauges. It’s important to recognize that no shield is perfect, though. Wind is an unavoidable challenge of the space.

What is a disdrometer, and do I need one?

All disdrometers are rain gauges, but not all rain gauges are disdrometers. The gauges explored above are primarily designed to measure rainfall (totals) and intensity (rate). Disdrometers monitor and analyze actual raindrops to provide additional information on droplet size, velocity, and variation thereof.

Depending on the situation, disdrometers can achieve this use a variety of methodologies, including…

• Optics: A series of lasers or infrared beams “sees” raindrops as they fall onto a glass lens.
• Acoustics: A sensor within a large body of water “listens” to raindrops as they hit the surface.
• Radar: A series of radar waves is directed into a storm to map the size and distribution of droplets before they reach the ground.

With that said, disdrometers will always sacrifice accuracy on volume in favor of providing those more granular insights about droplets. That means they can help you dive deeper into understanding a storm if you’re studying precipitation at a scientific level, but if you just want to know how much it rained, a tipping bucket or weighing gauge is a much better investment than a disdrometer.

What do I need besides rain gauges to build a precipitation monitoring network?

There’s more to network design than deciding which kind(s) of rain gauges you want to use. It’s equally important to think about…

• The density of the network: How many stations will you include and how far apart will they be spaced? Are there key areas within your network of especially high interest or importance?
• Your telemetry strategy: Many of the sensors above are still compatible with traditional pen-and-chart recording, but if you want modern on-demand remote access to information, you need to consider how you’ll get data from your gauges into your hands.
• Your data viewing, reporting, and analysis platform: Are you comfortable working from scratch with raw data from your gauges, or would you prefer software that structures that data into a narrative? What kinds of graphs, charts, or reports would be useful for your work? What other data would you like to see side-by-side with your gauge network?

…If you need help wrapping your head around any of those pieces, AEM is here to help. We can help you scale your rain gauge network to your area and goals, connect you with the equipment you need to deliver reliable data, and show you how to turn your data into difference-making actions you wouldn’t have known to take otherwise.