Introducing the new
Premium CoCoRaHS Gauge

Yes! It is the “premium CoCoRaHS gauge” and is an approved gauge for measuring precipitation for the CoCoRaHS network.

Yes! Ten carefully-selected field testers across the United States critically evaluated the features, measurements, and accuracy of the TROPO gauge. The 2-month long field testing and evaluation campaign addressed (1) installation, (2) handling & features, (3) measurement and accuracy, and (4) the user guide. The field testing campaign helped inform final design tweaks to the TROPO, edits to the user guide and solidified endorsement by CoCoRaHS. For a very comprehensive and independent scientific evaluation of the TROPO, visit https://wermenh.com/tropo/.

The true weight of an inch of water in a four-inch diameter cylindrical vessel is 206 grams, but when filled to the 1.00 inch mark on the Stratus gauge, it only weighs 201 grams. The Stratus gauge has a known and documented error, but in order to keep your measurements consistent with the gauge you're using, CoCoRaHS recommends that if you own a Stratus gauge, divide the weight of precipitation by 201. If you own and use the accurate TROPO gauge, divide by 206.

The TROPO is designed to minimize evaporation loss from the gauge, but sometimes condensed water from evaporation is trapped within the gauge and rain droplets themselves cling to the sides of the tubes from surface tension. This amount of water is negligible and only amounts to about .005”, or less, and does not impact your measurements. To minimize the surface tension of the water, try using Rain-X® Plastic Water Repellent Trigger. This is specifically designed to repel water from polycarbonate plastic and it will not harm the gauge.

Pour out the 1" (25.4 mm) of water from the inner tube and pour in the water left over in the outer tube into the inner tube and note the amount. Then simply add the 1" (25.4 mm) to whatever you measured from the outer tube (using the inner tube) to get an accurate total. Note: After a big storm, you might have to do this several times if the outer tube has more than 1" (25.4 mm) of water in it. Alternatively, you can use a scale to determine the weight (in grams) of the entire gauge, filled with water, then subtract the dry weight of the gauge and divide this number by 206 to get the rainfall in inches, or divide by 8.1 to get the rainfall in mm.

Knowing that one inch of water equals 206 grams within a 4-inch diameter cylinder, we used a CoCoRaHS-approved scale, and tared the scale (to 0) with the gauge on the scale, then poured water into the TROPO until it reached 206 grams and then checked to make sure the meniscus was at the 1.00” marking on the inner cylinder. And sure enough, it was perfect.

This could be due to numerous reasons, but assuming all things equal, the primary reason is because the TROPO gauge is perfectly calibrated whereas other popular 4” rain gauges are not. During our calibration, testing and comparison evaluations, we found that the “Stratus” All-Weather precipitation gauge and the “Outback Blue” precipitation gauge were off by about 4%. In other words, when the Stratus inner tube was filled with 206 g of water, which is mathematically equivalent to 1.00” of water, .04” of water overflowed past the 1.00” marking.

Technically excess snow may end up in the outer tube, but the spout is very small and its impact on the snow core sample/SWE is negligible. The errors in collecting a representative snow core are much larger than what the small spout would contribute. We discussed this with the CoCoRaHS team and they agree. If you are concerned about this, you can tape off the spout to prevent it from impacting the snow core.

The extra tall cap on the TROPO is prone to blowing off, so we engineered a way for the cap to snap on without any moving parts. As a result of this tight fit, some may initially find it difficult to remove the cap. For some tips and tricks on how to more easily affix and remove the cap, see the Knowledge Base section below. Alternatively, you can apply a small amount of grease on the 3 dots inside the cap to allow them to snap in/out easier. We also think repeated use of the gauge will eventually make it easier to operate.

First, use a scale to determine the weight of the dry, empty outer tube; write the weight down on the bottom of the tube with a Sharpie for future reference. When the outer tube contains precipitation, weigh it and subtract the dry weight of the tube to determine the weight of just the precipitation. Take the weight in grams and divide it by 206 g (or weight in ounces divided by 7.27 oz). For example, if the precipitation weighed 80 g (2.8 oz), the precipitation depth would be 80 g divided by 206 g (or 2.8 oz divided by 7.27 oz), both equate to 0.39 inches (9.9 mm) of precipitation. Easy, fast and accurate!

This is by design so the outer gradations are not used to provide anything more than an estimate of the accumulated precipitation. For an accurate measurement, you must repeatedly decant the precipitation collected in the outer tube into the inner tube that offers precise measurement gradations.

To buy replacement/extra parts and other weather instruments, visit our online store at store.climalytic.com. It’s also really handy having at least one extra outer tube so that you can quickly swap out gauges amidst heavy precipitation events at your observation time.

View our 2023 Annual American Meteorological Society conference poster (in the Knowledge Base section below) for our top 10 reasons manual precipitation gauges are so important.

You can download the user guide and other TROPO resources in the Knowledge Base section below.

There are a number of citizen science organizations and observer networks that value precipitation data. The largest such network is the Community Collaborative Rain, Hail and Snow Network, or CoCoRaHS. CoCoRaHS is a network of volunteer weather observers in the United States, Canada, and the Bahamas.

Yes, please contact us for bulk order discounts and/or reseller opportunities.

First compute the volume of 4” diameter (2” radius) cylinder that is 1” long. Using the equation π*r^2*h equals 12.57 cubic inches. Then, we know the density of water, which is not compressible, is 16.387 grams per cubic inch, so if you multiply volume (12.57) by density (16.387) you get 206 grams.

How far up should the top of the TROPO gauge extend above the post, fence or post it’s attached to? There is not an official requirement for this, but to limit splashing from the post or fence into the gauge, or wind under/over-catch impacts, we recommend the top of the TROPO be positioned as far above the post or fence as the bracket will allow. It is strongly recommended that the wooden post be beveled at the top to limit any splashing into the gauge.

See https://climalytic.com/tropo#specs

We offer free replacement of damaged or defective parts upon arrival, but otherwise we don't offer a warranty. The UV-resistant polycarbonate material we're using is slightly flexible and can accommodate some freezing precipitation in the inner tube without damage, but we can not be responsible for misuse of the gauge, including cracked inner tubes as the result of freezing.

Life expectancy will vary depending on climate and care, but the UV-resistant poly-carbonate plastic is extremely durable and the same material greenhouses are made of. We're confident the plastic will last at least 10 years. The labels were added using a highly durable laser printing technique, which we also expect to last at least 10 years. Assuming a 15 year life span, the cost is only USD $0.018 (1.8 cents) per day!

We understand the price might be high for some, but we assure you the TROPO will last longer, preform better and offer a much better user experience than any other 4” gauge on the market. We’ve done our best to keep the price down as much as possible, but if you are looking for a lower price here are some options: (1) Pool together 12 CoCoRaHS observers who want to upgrade and buy a case of 12 of gauges, which drops the individual price down to $74.99 (including shipping!). (2) Wait for another sale that offers a deeper discount. (3) At some point in the future, we hope sponsors will help offset some of the costs for new and existing CoCoRaHS observers.

Looping an elastic insect repellent band or bracelet around the top of the gauge can help. Replace the band frequently for best results. Also, avoid installing the gauge near a light that naturally attracts bugs at night.