Decorative outdoor rain gauges

How Does A Rain Gauge Measure And How It Works?

Types And The Working Procedure Of Rain Gauge

Different types of rain gauges have developed over time. Considering place, working process, cost, and necessity, people, as well as different weather stations, use different types of rain gauge. Some examples are:

Non-Recording Rain Gauge

The most widely and commonly used rain gauge is this type. This type of gauge is preferred the most by the meteorological institutions.

Non-recording rain gauge consists of a 127mm of the cylindrical vessel and a base of a diameter of 210mm. At the top of the funnel, there is a circular brass which can fit the vessel well.

There is a receiving bottle of 75-100mm which is thinner than the cylinder and connected to the base. The funnel is inserted on the neck of the bottle for collecting rainfall.

Here, the receiving bottle has the capacity of collecting 100mm water. So, during heavy rainfall, the vessel would be exceeded frequently and hence, the rainfall should be measured for 3-4 times the initial reading by a graduated measuring glass.

The instrument should be kept clean all the time especially in dry weather for the accuracy of the result and for keeping it free from dust.

Recording Rain Gauge

Recording gauge can be subdivided again into three types, and they are:

Weighing Bucket

This is the most common self-recording gauge. The receiver bucket of this type is supported by the spring or weighing mechanism.

If there is heavy rainfall, then the weight of the bucket increases and the increased weight is shifted to a pen that records the measurement on a clock driven chart.

The curve or graph that is formed by plotting the accumulated rainfall in the receiver bucket is called the mass curve that helps to know the information about different rainfall.

Tipping Bucket

This is a type of gauge that is used commonly in the home weather station. The collector funnel of this bucket is made in such a way that it is connected with two containers horizontally where the rain is directed. When the bucket reaches the required weight, the bucket is flipped and discharged due to the gravitational force.

The number of flips or the switchovers is measured by the optical system, and this record gives the measurement of the precipitation.

One major benefit of using this instrument is that along with the rainfall it measures the rate of precipitation. But as usual, every material comes with a drawback. If the precipitation becomes high, then jam occurs that results in an inaccurate measurement of the rainfall.

Again, the flip of the bucket occurs when the water reaches a certain weight. If the rainfall is not enough to achieve that weight, then the amount of accumulated water will not be counted.

Optical Gauge

This gauge has a funnel on the photodiode. The measurement is done by visual irregularities. Here the drops of rainfall are directed by a beam of light and by measuring the intensity of the light the rate of precipitation is measured.

Weather: Measuring the Rain

Measuring the Rain

Rain gauges are thought to be the most ancient weather instruments, and they’re believed to have been used in India more than 2,000 years ago. A rain gauge is really just a cylinder that catches rain. If an inch collects in the cylinder, it means an inch of rain has fallen. It’s that simple. Most standard rain gauges have a wide funnel leading into the cylinder and are calibrated so that one-tenth of an inch of rain measures one inch when it collects inside. The funnel is 10 times the cross-sectional area of the tube. Rainfall as low as .01 inches can be measured with this instrument. Anything under .01 inches is considered a trace. This standard rain gauge is shown in the following figure.

Rain gauge—rainfall measurements.

Weather-Speak

A rain gauge is an instrument that measures the amount of rainfall at a given time interval.

In the more modern era, a common rain gauge is called the tipping bucket type. A bucket doesn’t really tip—a pair of small receiving funnels alternate in the collection of the rain. When one fills up with water, it tips and spills out, and the other comes into place to do the collecting. These little funnels tip each time rainfall amounts to .01 inches. The tip triggers a signal that is transmitted and recorded.

Of course, these rain gauges have a problem when the temperature drops below freezing, so the standard versions are heated for the occasion.

What about snowfall? When snow falls on these heated rain gauges, it melts, and a water equivalent is determined. The recorded precipitation is always expressed in terms of rainfall or melted snow. The snow depth doesn’t count—unless, of course, you have to shovel it! Sometimes a foot of snow amounts to just a half-inch of water, other times it amounts to three inches of water. It really depends on the water equivalent of the snow, which varies widely.

On the average, 10 inches of snow is equivalent to one inch of rain, but that’s only an average. If a rain gauge measures one inch of water during a snowstorm, an observer can’t automatically assume that 10 inches of snow has fallen. The snow depth can only be determined the old-fashioned way—by measuring it.

That depth is determined by taking an average of three or more representative spots. A ruler is stuck into the snow, and its depth is recorded. Because of blowing and drifting, the determination of three or more representative locations is not always easy. You would think that there would be a better way, but there really isn’t.

Most recently, Doppler radar has been used to estimate rainfall. We’ll take a look at this newest technology in the next section.

An instrument used by the meteorologists to measure the amount of rainfall over a period of time is the rain gauge. Rainfall is generally measured in millimeters or inches. There are many kinds of gauges – standard graduated cylinders, weighing gauges and tipping bucket gauges.

The standard rain gauge instrument generally consists of a funnel connecting to a graduated cylinder which is marked in millimeters. It has an outer cylinder which is 20 cm in diameter and 50 cm tall. When the rainwater overflows the inner cylinder, the large outer cylinder holds it. The amount of water in the outer cylinder and the inner cylinder are taken for rainfall measurement.

Tipping bucket rain gauges has a collector balanced on a pivot. It has reed switches and magnets that are used to generate the pulses that are in turn counted by electronic circuit within the device.

The rain gauge monitor counts the number of times the ‘collecting cups’ tip backwards and forwards. Each time this happens a certain amount of water has been collected. Knowing how many times the cups have rocked backwards and forwards will give an indication of how much rainfall there has been.

Rain gauges should be placed in an open area where there are no obstacles like buildings or trees to block the rain. This is also to prevent the water collected on the roofs of buildings or the leaves of trees from dripping into the rain gauge after a rain, resulting in inaccurate readings.

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Use a Rain Gauge to Measure Sprinkler Output to Help Keep Your Lawn Green and Healthy

Using a rain gauge to measure the output of your sprinkler is a great way to manage your lawn irrigation. Your lawn needs at least 1 to 1-1/2 inches of water each week—either by rain or watering–to stay healthy. While this is a good rule of thumb, it is based on your lawn’s water needs as averaged throughout the year. It is likely your lawn will require more water during the summer months and less water during the spring and fall months when the weather tends to be rainier and cooler.

Depending on your sprinkler, it can take between 15 and 30 minutes to apply ½ inch of water. It’s a good idea to measure your sprinkler’s output with a rain gauge to learn how long it needs to run to achieve that ½ inch of water. Also, because sprinklers don’t always put down water evenly, you should measure at several different output locations.

Three Lawn Watering Steps for Success:

1. Water deeply 1-2 times per week with about ½ inch of water each time. Watering daily will give your grass a shallow root system that will dry out faster and lead to a weakened lawn. Watering deeply will allow your lawn to develop a deep root system that will be stronger and more drought resistant.

2. Water early in the day if possible. It is cooler and less windy in the morning so you will have less evaporation. Plus, a wet lawn at night on a regular basis can lead to fungus and disease problems. If morning watering is not possible, watering at any time is always better than not watering at all.

3. During a prolonged drought, you can let your lawn go dormant and turn brown. A healthy lawn is amazingly resilient and will bounce back when rainfall and cooler temperatures return in the fall. Limit foot traffic as much as possible because dormant lawns cannot tolerate a lot of use without causing damage.

Here’s a general rule of thumb in the gardening world:

Most plants need around 1 inch of water every week.

While this sounds simple enough, it’s hard to know what 1 inch of water looks like. And without a rain gauge, you really have no way of knowing.

A rain gauge allows you to keep track of precipitation and irrigation output, so as not to overwater – which is not only wasteful, but could encourage disease and cause harm to plants.

There are some fancy models on the market, but for the home gardener, high-tech equipment isn’t really necessary.

In fact, you can even make your own if you want (tutorial with step-by-step photos coming soon!). Here’s everything we’ll cover in this article:

With this basic tool, you’ll be better able to care for your garden and spend less time watering unnecessarily.

What Is a Rain Gauge?

It’s a tool used to measure precipitation, most often rain. There are several types, but as a gardener, you will just need a standard gauge.

The basic model is a graduated cylinder that captures rainfall. It’s marked with measurements, usually inches in the US.

When the rain stops, you just read the cylinder much like you would a measuring cup. It’s that easy.

Other models include the tipping bucket, weighing gauge, and optical gauge. All of these can do more than the standard version, and are used to gain more sophisticated readings.

For instance, the tipping bucket can measure the rate of precipitation.

The weighing gauge measures precipitation mass via a sensor. Because it uses mass, it can measure snowfall and hail too.

And the optical gauge is crazy advanced and detects optical irregularities. I’ll be honest – this one is over my head and far beyond what is necessary for gardening purposes.

Let’s keep things simple!

How to Use It (and Where to Buy)

Rain gauges are great for measuring not only rainfall, but also water put out by sprinkler systems.

Stratus Precision Rain Gauge with Mounting Bracket, available on Amazon

There are several different versions of the standard models, from more expensive ones geared towards professionals to very basic ones that you just stick in the ground.

If you choose one to stick directly into the ground, keep in mind you may get some splashback that could skew the reading.

American Science & Surplus Basic Rain Gauge, available via Amazon

Also, leaves from any plants overhead can block rain from reaching the cylinder, or even drip moisture from their leaves into the cylinder, throwing off your reading.

Because of these factors, put the gauge a little ways off the ground and in an open area to ensure a more accurate reading.

The model that I have is bolted to my deck. It’s in a spot that is easy to see right when I walk out of my door, so I don’t have to go out of my way to check it.

Decorative options are even available, like this frog in his rain gear, to add a touch of whimsy to the landscape.

Resin Frog in Rain Gear Rain Gauge, available from Plow & Hearth

Once the sky clears, I check it, take a mental note, and dump it into a plant. That’s it.

If it has a minimum of 1 inch of water in it, I don’t worry about my perennials that week. And honestly, I don’t worry about my perennials anyway unless it has been dry for at least a couple of weeks, or I see signs of wilting.

Many perennials can handle a lengthy dry spell. But you need to know your plants. Hydrangeas and other heat-sensitive plants may need to be babied during drought.

I like to stick with native perennials myself, which are more tolerant of drought and local soil conditions.

As for annuals and edibles, you’ll want to be more diligent in checking your soil’s moisture level.

Measuring Sprinkler Output

If you want to measure sprinkler output, it might be a little tricky to find a good open location for your gauge – unless you’re focused on your lawn.

In the garden, do your best to keep gauges out from under plants but still in the middle of the action.

If you use a sprinkler on a regular basis, it’s helpful to get an idea of how long it takes for your system to produce an inch of water.

To do this, set your rain gauge out in the lawn. Then start your sprinkler up so that the gauge is within the sprinkler’s path.

After 15 minutes, check the amount collected. Take note, and then dump it.

Repeat this process two to three times and take the average of the results. The final measurement gives you a general idea of how much water your sprinkler produces in a 15-minute time span.

Use this measurement to figure out how long you’ll need to run your sprinkler in order to provide your garden or lawn with an inch of water.

It would be annoying to have to run out and check all the time, so getting an idea of your sprinkler’s flow rate will allow you to set your system on a timer and forget about it.

Keep in mind that sprinklers result in more runoff and evaporation than other forms of irrigation, like drip irrigation.

Supplemental Watering

No matter what, I always check the soil, especially around my annuals and edibles.

Checking the soil is the best way to get an idea of moisture needs. If the top 2 inches are dry, it’s time to grab the hose.

And while 1 inch of rain per week is sufficient in most cases, there are some exceptions.

If it’s a heavy, short downpour and there’s significant runoff, you may be surprised by how little penetration occurs.

Also, if you have a raised bed, the soil will likely dry out faster than a garden planted at ground level. So plan on hand watering raised beds more frequently than ground level gardens in the absence of rain.

One inch of water should penetrate the soil somewhere between 6 and 15 inches deep. But your soil type can dramatically affect this.

Clay soils, which are denser, won’t be as deeply penetrated by a 1-inch rain event as loamy and sandy soils.

Also, if temperatures are consistently above 90°F, moisture needs may jump from 1 inch per week to 2 inches per week.

As a general practice, try to water in the morning before the heat sets in. This will help to ease the heat stress placed on your plants.

It will also give your plants time to dry out completely during the day. Wet conditions in the coolness of night make a nice, cozy environment for diseases to develop – and we don’t want that!

Mulching your garden with wood chips, pine straw, or organic matter is also a great way to retain soil moisture and reduce the need for hand watering.

Take the Guesswork Out of It

As basic and essential as water is to your garden, it’s not always easy to know when to supplement, or how much your garden needs.

And for some reason, it’s easy to think your garden needs more water than it actually does.

Using a rain gauge is a great way to take some of the guesswork out of it.

This simple tool gives you a general idea of how much water has hit the soil, which will limit how often you find yourself reaching for the hose.

And coupled with checking your soil before you water, it will give you a lot more confidence in caring for your garden.

I don’t know about you, but I often have a hard time remembering what I did yesterday, let alone the last time it rained.

So having a rain gauge as a reference keeps me from drowning my garden, and gives me more confidence in how often I do choose to get the hose out.

Have you used a rain gauge? Do you find it helpful? Share your favorites (or DIY construction tips) with us in the comments!

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Product photos via Stratus, American Science & Surplus, and Plow & Hearth. Uncredited photos: . With additional writing and editing by Allison Sidhu.

About Amber Shidler

Amber Shidler lives in Cincinnati, Ohio and holds a dual bachelor’s degree in botany and geography. For four years she worked as a horticulturist, but is now a stay-at-home mom. With experience in landscape design, installation, and maintenance she has set her sights on turning her tenth-of-an-acre lot into a productive oasis. Amber is passionate about all things gardening, especially growing and enjoying organic food.

What Is A Rain Gauge: Garden Rain Gauge Info And Types Of Rain Gauges

Rain gauges are a great way to save water in the landscape. There are different types that can be used depending on your needs. Keep reading for additional information on exactly what is a rain gauge and how a rain gauge can be used in the home garden.

What is a Rain Gauge?

Rain gauges for home use are a fundamental tool in the home landscape. With a garden rain gauge, maintenance of garden irrigation can be managed and therefore, results in healthier plants and lawn. A rain gauge may prevent drought stressed plants or conversely, over watered areas which may contribute to a slew of issues.

Overwatering is not only costly but may promote shallow roots, which in turn increase the plants susceptibility to disease. Overwatering is also environmentally unfriendly and encourages pollution risks from garden care products.

How a Rain Gauge Can Be Used

Of course, the amount of water plants need varies according to season and landscape, but most require some water every week during the warmest months. A rain gauge measures not only rain, but dew and mist. A garden rain gauge also can be used to keep track of sprinkler output, completing the task of managing irrigation.

To assure an accurate reading, the rain gauge should be placed in an open area away from trees, the house and other outbuildings. Position the rain gauge twice as far away as the height of a tree or other object and be sure to empty it after every rain shower.

Types of Rain Gauges

Check with your local garden supplier or online retailers for different types of rain gauges for home use. An automatic type of rain gauge that registers inside the home is perfect for the hi-tech gardener, but most types of rain gauges are fairly simple devices that are mounted on a post with a screw or stuck in the ground with a spike, or stand atop the ground with an often decorative holder.

With a few basic materials, a rain gauge can also be crafted at home. You will need a straight sided glass that can be marked with a measuring scale and a coat hanger or wire bent to create a holding rack. Also, a hammer and some nails to secure the rack. You will want to position the rain gauge away from overhead objects and take care to fasten it securely so the wind doesn’t tip the garden rain gauge over. A fence edge or the like is ideal. Attach the holding rack and slip in the glass. Ta-da! You are ready to record your local precipitation.

Using a Rain Gauge to Measure Sprinkler Output

The rain gauge is also a great tool to manage your irrigation. One to 2 inches of water per week is recommended for most lawns and gardens. To use the rain gauge to measure the output of your sprinkler system, be sure it is in the path of the area being watered.

After the sprinkler system has run for at least 30 minutes, measure the depth of water and multiply by two to figure the output of water over the course of an hour. Through trial and error, the next time you irrigate, the flow rate (gallon per minute) can be “reduced to ½ over 30 minutes. If the flow rate isn’t contributing to runoff, then reduce the running time to 20 minutes and re-measure to see if you are now at ½.”

The only certain way to know how much precipitation is affecting the garden, and hence manage our precious water reserves, is to use a garden rain gauge. Keeping track of rainfall amounts is a great way to cut costs and conserve water in the landscape.

Contents

  1. Definition
  2. Types of rain gauges and how they work
    1. Graduate cylinder
    2. Tipping bucket
    3. Weighing gauge
    4. Optical gauge
  3. Manufacturers and models
  4. Share your data
  5. Sites

Definition

First, let’s head to the most important question and define what actually a rain gauge is.

The rain gauge is a meteorological instrument for measuring the amount of precipitation (especially rainfall amounts) fallen during a given time interval at a certain location. In short – the rain gauge are used to measure rainfall. It is commonly used in personal or automatic weather stations. There are different types gauges, some use direct measurement technique or others are completely automatic.

You probably wonder what type of measurement units are used, and the answer is – usually inches (millimeters) or liters per square meter.

The rain gauge consists of two important parts:

  • a collector funnel;
  • mechanism to receive and measure the collected water;

The interior of the rain gauge funnel has special coating to reduce the wetting of the surface. The cone of the funnel should be deep enough, which allows the water to flow without any risk of splash. Mesh filter are used to prevent debris like leaves of bird droppings from clogging the gauge.

Place the rain collecting device at a sufficient height (usually 3 feet from the ground), and at a distance of several feet from other objects ensures that there will be no water rebound from floor or objects around.

Types of gauges and how they work

To answer this question we must first define different types of rain gauges.

The rain gauges were originally manual, that is to say, a meteorological technician had to come and regularly check the rainfall amounts and empty the unit – a tedious job especially with high amounts of rain. With technological advancement in the early twenty-first century, the gauges were equipped with sensors that enable electronic collection of data to be continuous and form a distance. However, manual rain gauges are reliable and accurate and are still used by amateurs or networks of volunteer observers.

There are four types of gauges:

  • graduated cylinder (called standard or direct reading gauge);
  • tipping bucket;
  • weighing gauges;
  • and optical;

Graduate Cylinder (standard gauge)

The standard rain gauge was developed at the beginning of the twentieth century and consists of a graduated cylinder (2 cm diameter) in which the collection funnel drains. Most of these gauges use scale from 0.2 mm to 25 mm. If the main unit accumulates too much water, the surplus is directed to a bigger container with diameter around 20 cm.

You record the total rainfall by measuring the total height reached on the cylinder. This is a straight forward device and quite easy to use.

Tipping Bucket

The tipping bucket gauge is made of collector funnel that directs the rain towards a two small containers, positioned on either side of a horizontal axis. The water collects inside one of the buckets that flip horizontally when it reaches the required weight, and discharges trough the force of gravity. The amount of precipitation is measured by the number of switchovers carried by the buckets, detected by a mechanical or optical system.

The advantage of this type of gauge is that it measures the rate of precipitation in addition to the total rainfall. However, when the precipitation rate is too high it may jam and report inaccurate rainfall data.

Tipping bucket rain gauge is not as precise as direct measurement, because if the rain ends before one of the buckets is full, the water inside will not be counted. Later a gust of wind can tip it and give a false accumulation when there is no rain.

The tipping bucket is the most commonly used type of rain gauge in home weather stations. Often times they use remote wireless communication to send their data.

Weighing gauge

This type of rain uses the mass of accumulated water inside the collection container to calculate precipitation amount. Earlier models were recording the data by moving the tip of a stylus on to a graphic paper specially calibrated for this purpose. With the advance of technology the data is collected by a sensor and converted into numerical values directly into a logger.

This type of rain gauge measures all the rainfall and can measure solid precipitation, such as snow and hail. However, it is more expensive than direct-reading rain gauge and requires more maintenance than the tipping buckets.

Optical gauge

The optical gauge is has a funnel on top of a photodiode or a laser diode. Rainfall is measured by detecting optical irregularities. The funnel directs the drops at the light beam, then by measuring the intensity of scintillation it can electronically determine the rate of precipitation.

Manufacturers and Models

What are you going to buy in terms of manufacturer and the model is all dependent on you budget and use case. If you are looking for professional grade – electronic rain gauges- you have to lock at companies like Young with their models 52202 / 50202 and HOBO with their Rain Gauge Data Logger.

But for weather enthusiast and volunteer observers the choices are more and less expensive.

I am going to list a couple of models for you to have general idea what’s on the market.

If you are interested in buying standard type rain gauge you have two options:

Stratus RG202

Availability and Price

This is highly reliable rain gauge, recommended by the National Weather Service, and used by CoCoRaHS enthusiast around US. It can measure up to 11 inches of precipitation with 1 inch inner and 13 inch outer tube. The inner scale is easy to read and can measure 1/100ths of an inch of rain which that gives good accuracy. The installation is easy; just make sure it’s not close to buildings or trees.

If you are not looking for remote electronic device I strongly recommend this one.

Pros:

  • record more than 6 inches of rain
  • easy to read
  • affordable price
  • accurate

Cons:

  • can have problem with high winds
  • needs direct reading
  • if more than 1 inch of rain occurs additional work is needed to calculate the total

AcuRite 5-inch Rain Gauge

Availability and Price

This is easy to read standard type rain gauge by AcuRite. It measures up to 6 inch of rain and the scale is on every 1/10ths of an inch. The gauge has options to be mounted on the fence or stick on the ground. It is made of hard plastic but don’t let it freeze with water inside because it may break.

This model is not as good as Stratus RG202, and can’t be use for reporting precipitation with any of the networks. But if you don’t need all of this it’s reliable and easy to read device.

Pros:

  • cheap
  • easy to read

Cons:

  • can’t be used for reporting with CoCoHaRs or Coop
  • measures only 5 inches
  • scale every 10ths of an inch
  • prone to freezing

For the wireless (remote) tipping bucket type gauges the choice spectrum is much wider. Lest see couple of options.

Oregon Scientific RGR126N

Availability and Price

The second wireless rain gauge in our short list is Oregon Scientific RGR126N. The biggest advantage of this type of sensors is that you are skipping the hassle to go outside and check the unit, and the ability on some of the devices to log historical data.

The RGR126 adopts the tipping bucket design and features two part system – outside sensor and inside display unit. This model also includes an outside thermometer for some temperature readout.

The data resolution of RGR126N is .04 inches which makes it quite accurate. The indoor unit will display daily and cumulative rainfall for the past 10 days. Data can be transmitted from up to 300 feet.

The only maintenance you have to do is check for clogging and change batteries every 12 months. You can use Lithium AA batteries for longer operation.

The RGR126N is a pretty decent gauge with reasonable price.

AcuRite 00899

Availability and Price

This is a cheap wireless rain gauge that has all the necessary parts like self emptying tipping bucket and indoor display unit.

The unit has 0.01 inch precision – very good for device in this price segment. It has flood alarms and can report historical data.

It’s a great device for birthday present or young amateur meteorologist.

Be sure to check the AcuRite website on how to calibrate the device.

RainWise Rainew W

Availability and Price

If you are looking for professional and affordable wireless rain gauge this device may satisfy your needs. The RainWise RAINEW meets all the NWS specifications and standards for statistical accuracy. The device is calibrated and has data resolution of 100ths of an inch and can measure up to 9.99 inches of rain.

It comes with their 8 inch self-emptying tipping bucket that will spare you the trips outside to empty the gauge. Just position the bucket in an open area and read the date on the indoor display.

The thing I like about this model is the convenient minimalist dual display for tracking both current and cumulative (annual) precipitation amounts. No additional data and no fancy stuff. Any of the counters can be set to zero at any given time.

The transmitter operates up to 300 feet away. To power the console use 3 AA batteries that will give you up to 9 months life and for the gauge use 2 AA with 12 months life span.

Share and view precipitation data

With today’s fast and reliable digital communication I cannot point how easy is to share your data. It is an important part of being a amateur meteorologist. So please consider doing it.

There are two major volunteer observer programs you can share your data with –

  • The National Weather Service – Cooperative Observer Program (Coop)
  • Community Collaborative Rain, Hail and Snow Network (CoCoRaHS)

They are both community projects and the only thing you need is enthusiasm and some equipment (rain gauge or home weather station) to collect data.

CoCoRaHS

CoCoRaHS is a network originated with the Colorado Climate Center at Colorado State University in 1998 thanks in part to the Fort Collins flood a year prior. This is a community project everyone can help young old or in between. The only requirements are and enthusiasm for watching and reporting weather conditions and a desire to learn more about how weather can affect impact our lives.

On CoCoRaHS site you will find lots of materials on how to mount you rain gauge, how to measure rain snow and hail. Be sure to check what type of gauge you can use because the network does not use any automatic type instruments. I think you pretty much have to use the Stratus RG202.

Check the CoCoRaHs official data sheet to get an idea what reporting form looks like.

Coop

Every day thousands of volunteers in the Coop program collect and submit data from their weather stations. This citizen observer effort officially began in 1890. The cooperative observer program is at the heart of climate measurement in the United States. There are over 11,000 stations across the country.

The observer careful records of whether form the foundation of the climate information. Each station has precise scientific instruments to measure temperature precipitation evaporation and snow depth.

If you are interested about reporting data to this program, check their website for additional info.

Be advised that you may need a personal weather station to share the full spectrum of data that NWA can collect and process.

Read more: What Is Home Weather Station and How to Choose One

Rainlog.org

Rainlog.org is Arizona’s cooperative rainfall monitoring network

The collected data is used for variety of applications, from watershed management activities to drought planning at local, county, and state levels.

To participate you need a rain gauge and access to the Internet. Than all you need to do is set your rain gauge, install it and report on daily basis. You can use all types of rain gauges with Rainlog.org

Sites with live rain gauge data

There is couple of sites with live precipitation data reported by amateurs with rain gauges across USA.

  • COOP Land Based Stations
  • CoCoRaHs
  • Rainlog Org

Three Best Uses for a Rain Gauge

The rain gauge is an instrument that is used to measure the amount of rainfall or precipitation over a particular period of time at a specific place. However, there are a couple of uses it serves and forms it may take, which are quite interesting. Here are some of these uses which you might consider keeping this tool for.

1. Measuring

Generally, as the name itself suggests, a rain gauge (or “pluviometer”) is an instrument that is used as a form of measurement. Hence, the basic design of this tool does just that, measuring for the purpose of collecting data about falling precipitation. This is the most common use for a rain gauge and several different types have been developed for this purpose.

A tipping bucket rain gauge incorporates a large copper cylinder along with some levers, a funnel, and a recorder that is made up of a wheel and a pen. The levers are situated on a pivot point which is like a scale and whenever a certain amount of precipitation has been reached, the lever then tips and sends the signal to the recorder. Meanwhile, the pen moves either up or down as it records the lever movement together with the quantity of precipitation.

A more advanced version of this instrument is the optical rain gauge. This gauge is made up of a row of funnels, a laser diode, and a phototransistor detector. When there is enough water in the funnels to create a single drop, it falls down, passing through the laser beam. Thus, every time a water drop passes through the laser beam path, this will create a small flash which is detected by the phototransistor detector and recorded as data.

2. Weighing Precipitation

A special weighing rain gauge features a rotating drum, a pen, and a storage bin. The storage drum collects any form of precipitation while the pen positioned below the drum records its weight.

3. Studying the Weather

A rain gauge is a crucial instrument utilized in the study of the weather phenomenon as well. Meteorologists and hydrologists use these instruments so that they will be able to examine and then gauge the exact level of precipitation or rainfall following a particular time frame. Long term data can help scientists predict weather patterns and learn from any trends exhibited in their data.

These are the most common uses of several types of rain gauges. Overall, whatever kind of rain gauge you prefer to use, what you should keep in mind is the purpose you’re using it for. This will determine the best kind of gauge for the topic you’re using it to study.

8 inch Rain Gage

8 Inch Non-Recording
Standard Rain Gauge

Introduction | Rain gauge description | Major gauge components
Installation of the 8-Inch gauge | Wind shield
Snowfall and the SRG | SRG comparisons with other rain gauges

Introduction

The purpose of this page is to provide information on the 8-inch non-recording standard rain gauge (SRG). It describes the four major components of the gauge, the installation and exposure of the gauge, the use of wind shields, and measuring snowfall. It ends with a comparison of the SRG with other types of rain collectors.

Rain gauge description

In its simplest form, an 8-inch Standard Rain gauge is an open mouth can with straight sides. Every climatological station in the “A” Network must be equipped with a SRG. Even though the SRG is preferred, the 11 inch plastic gauge is an acceptable substitute in stations other than those in the “A” Network.

At National Weather Service (NWS) Cooperative Weather Stations, the SRG is the center around which all documentation evolves. Spacial coordinates (latitude, longitude), as well as elevation, are fixed from the Standard Rain gauge location. Also, azimuth and range calculations for co-located equipment and obstructions within 200 feet are based on the SRG location. It is the primary point from which all distances and elevation angles for the station, as required on the B-44, are determined. If an 11 inch plastic rain gauge is used in lieu of a SRG, it too becomes the primary point of calculations.

The 8-inch standard rain gauge is a simple non recording gauge consisting of four major components. These include:

  • Measuring Stick
  • Overflow Can
  • Collector Funnel
  • Measuring Tube
  • The 8-inch gauge used in the National Weather Service is of a standardized design used throughout the world for official rainfall measurements. This standardization provides uniformity, continuity, and credibility of precipitation data worldwide.

    There are two basic type of the 8-inch gauge: a large capacity gauge and a small capacity gauge. The traditional large gauge has a capacity of 20 inches whereas the smaller gauge’s capacity is 7 inches. The 20 inch gauge is the norm throughout the National Weather Service. However, other agencies like the U.S. Forest Service often use the smaller gauge. The inner measuring tube of the large NWS gauge holds 2.0 inches of precipitation. The measuring tube of the small gauge holds 0.50 inch. For the remainder of this document we will be referring the NWS 20 inch capacity gauge.

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    Major gauge components

    Measuring Stick

    Precipitation is measured in the measuring tube of the Standard Rain gauge with a black laminated measuring stick approximately 24″ long. The stick is graduated in white, easy to read marks every one hundredth of an inch. To measure rainfall, the stick is inserted through the orifice of collector funnel and allowed to extend to the bottom of the measuring tube. The stick should be removed immediately. The precipitation collected in the measuring tube will “wet” the stick. Read, record and report the liquid measurement to inches and hundredths (i.e., 1.34 inch).

    The insertion of the stick displaces the collected water slightly upward. However, this error is considered negligible. Also, it should be understood that 0.005 inch of precipitation, one-half of one stick division, is required to wet a previously dry funnel before water will flow into the measuring tube. This unavoidable error is also considered negligible.

    If the rainfall is greater than the measuring tube capacity, water will overflow into the overflow can. The measuring stick should not be used directly in the overflow can. Instead, water from the overflow can should be poured into an empty measuring tube for measurement with the stick.

    Overflow Can

    The overflow can of the Standard Rain gauge collects water when rainfall greater than 2.00 inches occurs during the observation period and overflows the measuring tube. The maximum capacity of the overflow can is 20 inches.

    In addition to serving as an overflow collector for rainfall, the overflow can also is used as the primary collector in frozen precipitation events. When solid precipitation is expected, only the overflow can is left in place outside. Both the collector funnel and the measuring tube are removed to allow snowfall to collect directly in the overflow can. Obviously, if the funnel were left in place, snow would quickly accumulate and mound it over. Also, freezing rain would quickly plug the small orifice of the funnel.

    To determining precipitation in these events, i.e., the water equivalent of solid precipitation, the solid precipitation accumulated in the overflow can is not measured directly in the overflow can. Instead, the contents of the overflow can are melted and poured into the measuring tube for measurement. This facilitates the measurement of the water content of solid precipitation to the nearest hundredth of an inch as required for precipitation measurements.

    The overflow can also be used to cut snow samples for the determination of water content of snow on the ground. If ice or dense snow accumulation on the ground are persistent problems at a Cooperative Weather Station, the overflow can may be fitted with a snow cutter. This cutter is a saw-toothed piece of metal which slips over the top of the overflow can.

    CAUTION The snow cutter is very sharp and potentially dangerous, if not handled properly.

    Observers issued a snow cutter should be admonished to take extreme care during use. They should also be advised to store the cutter away from children. Specific procedures for measuring solid precipitation using the SRG are outlined below.

    The primary problem associated with the overflow can is leaks. Overflow cans develop leaks at the bottom and/or at vertical seams after being subjected to freezing temperatures while holding water. Some leaks are apparent upon visual inspection. Smaller leaks may require the visiting NWS representative to add water to the can. If leaks are detected, they must be repaired or the overflow can replaced.

    Collector Funnel

    Two types of collector funnels are used with the SRG. Older units are made of copper while newer funnels are made of fiberglass. Rainfall is caught in the collector funnel and conducted into the measuring tube. The funnel is 8 inches in diameter with a knife edged rim. It is designed to readily slide over the overflow can. Some lock into place with 2 slots fitting over corresponding screws in the overflow can. The collector funnel also serves as a deterrent to evaporation.

    The cross-sectional area of the collector is 10 times that of the measuring tube. Therefore, the depth of the water standing in the measuring tube is exactly 10 times the depth of the precipitation that has fallen.

    Caution should be taken when handling the metal collector funnels. Dents in the lower edge of the funnel can make it difficulty or impossible to fit over the overflow can. If necessary, a small hammer can be used to remove dents so it will fit over the can. Also, fiberglass collector funnels are easily cracked or broken, if dropped.


    Collector Funnel and Measuring Tube

    Measuring Tube

    The measuring tube is a 20 inch tall cylindrical straight walled tube used as the receptacle for collected precipitation. It holds 2.0 inches of precipitation. Due to the cross-sectional area relationship between the collector funnel and the measuring tube, 1 inch of rainfall fills the measuring tube to a depth of 10 inches. Two types of tubes are in use. The older units are made of brass while the newer units are made of plastic. All things considered, the older brass units are better suited for NWS applications in all regions. The plastic measuring tubes are more prone to damage as the bottoms are simply glued in place The brass unit can also develop leaks from freezing temperatures.

    As previously mentioned with overflow cans, measuring tubes with leaks should be replaced with spares.

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    Installation of the 8-Inch gauge

    Supports for the SRG are now made of aluminum. Older units are made of steel or wood. The gauge support should normally be installed to where the bottom of the gauge is about 10-15 inches above the ground. In areas that experience deep snow pack, however, the installed height above the ground is often significantly higher.


    Typical gauge Support

    Ensure that the SRG is vertical with the 8 inch collector opening level. Installation stakes supplied with the new aluminum supports (see figure) are driven into the ground in a pattern which facilitates the attachment of the assembled support. When driving of stakes, ensure that the tops of all three are level before mounting the support. This will prevent distortion of the support and make installation easier. Adjustments to the alignment of the three installed stakes relative to the support can be easily accomplished with a hammer. Once the SRG support in completely installed, the SRG should be inserted into the support and leveled. This is accomplished by gently driving in the appropriate stake(s) to attain a level posture for the 8 inch opening of the SRG.

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    SRG exposure

    The exposure of the rain gauges is of primary importance in the accuracy of precipitation measurements, especially snowfall. An ideal exposure eliminates all turbulence and eddy currents near the gauge that tend to reduce the catch, especially with increased wind speed.

    Rain gauges should not be located in wide-open spaces or on elevated sites such as tops of buildings as wind and resulting turbulence will likewise reduce the precipitation catch. Roof locations are not acceptable. The best location for a gauge is where the gauge is uniformly protected in all directions, such as in an open grove of trees.

    Prior to initial installation of the SRG, extreme care should be given to assuring proper exposure. Even so, one must be extremely concerned regarding obstructions which may affect the catch in the gauge. As a general rule concerning an objects height and distance relationship:

    The height of the projection should not exceed twice its distance from the gauge.

    When relating this rule to basic geometry, the projection above the gauge should not exceed 30 degrees above an artificial horizon drawn across the top of the gauge. An imaginary 30 degree cone surrounding the SRG should not be encroached.

    Good exposures are not always permanent. Over the years, SRGs may become influenced by trees, brush, or new constructions necessitating the move of the SRG to a site having better exposure.

    Proper exposure should not be compromised!

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    Wind shields

    SRGs are sometimes installed in locations where wind effects which reduce gauge catch can not be reduced by site selection. In such cases, use of a wind shield may be advisable, particularly at stations subject to excessive snowfall.

    Two type of shields have had wide use in the United States. They are the Nipher Shield, a flared metal device that attaches to the precipitation gauge, and the Alter type which consists of 32 free swinging galvanized metal leaves, or baffles, attached to a steel ring 4 feet in diameter and supported by 3 or 4 galvanized pipes. One of the quadrants of the Alter’s ring is hinged to allow for easy, safe access to the gauge. These shields can be used on the SRG or Recording Rain gauges. The installed shield’s leaves should extend 1/2 inch above the level plane of the orifice.

    Both types of shields can greatly improve catches at very windy sites. The Alter has become the standard in the United States. The main benefit of using a wind shield occurs during snow season in windy areas.

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    Snowfall and the SRG

    For the purposes of this document, the term snowfall also includes glaze, hail, and other forms of solid precipitation.

    Snowfall is collected in the SRG’s overflow can with the funnel collector and measuring tube removed. This allows snow to fall directly into can to provide a representation of the snowfall at the site. Snowfall, the depth of newly fallen snow since the last scheduled observation, is not measured directly in the overflow can. Instead, snowfall is ordinarily measured on a nearby grassy surface a short distance away from the SRG. It is also advisable to use a snow board to provide a cleared surface for determining newly fallen snow. Snow Boards are discussed thoroughly in Section 2.5.4 of Weather Service Operations Handbook #2 (WSOH02). Snowfall is measured in inches and tenths (i.e., 1.3). Even though snow measuring sticks are available, it is common practice for the SRG’s measuring stick to be used where one tenth on the measuring stick equals one inch of snow.

    Snowfall collected in the SRG Overflow Can is to be melted and measured in the measuring tube to provide the 24 hour precipitation. The measuring tube and measuring stick are used to allow measurement of the water content of the snowfall to be measured to the nearest hundredth of an inch as required.

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    SRG comparisons with other rain gauges

    Universal Weighing Rain gauge

    Observers may encounter differences in the catch between a recording rain gauge and a nearby SRG. Such differences are, in fact, typical.

    Studies by Jones (1969) showed that recording rain gauges, such as the Universal, with their sloping shoulders below the orifice collected 2 to 6 percent less rain than the 8″ Standard Rain gauge which has straight sides. The slope of the Universal’s shoulder can induce upward wind currents that may carry away some of the raindrops. Larger errors occur with snowfall.

    The tipping bucket has characteristics that can produce errors when compared to the SRG. During very light rains in warm weather, water can accumulate in the tipping bucket slowly enough to allow losses from evaporation before the bucket is tipped. During intense rainfall, some error will result as water continues to pour into the already filled bucket during the tipping motion. With an actual rainfall rate of 5 inches per hour, the recording rate in gauges with a mercury switch may be 5 percent too low (Parsons 1941). This error has been reduced to about one-half this magnitude in newer types of tipping bucket gauges.

    The Automated Surface Observing System (ASOS) uses a tipping bucket and automatically makes a correction to the one-minute rainfall accumulation in heavy rainfall situation. Whenever more than 0.10 inch of rainfall is measured in one minute, rainfall is added to the one-minute total to compensate for the tipping bucket lose during heavy rainfall.

    The information and pictures on this page are courtesy of the NWS Training Center.

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