How to Read a Rain Gauge

Meteorologists and hydrologists use the rain gauge to measure the amount of liquid precipitation in a given area over a certain period. Surprisingly, the use of rain gauges dates back to the fourth century BC among the Indians and the Jews.

State treaties decreed that a rain gauge measuring 18 inches in diameter was to determine the planting schedule and the type of seed to be planted.

Over the years, the rain gauge has undergone various inventions and technological advancements. The Asians pioneered and later embraced by the Europeans.

Today, rain gauges are spread across the world and are used by governments, airports, schools, and primarily by farmers and gardeners who strive to better their farm produce.

How to Read a Rain Gauge

Measuring the amount of liquid precipitation using a rain gauge is simple. Although water is measured in volume, a rain gauge measures the amount of rainfall in centimeters or millimeters, units used to measure length.

The units are calibrated on one side of the measuring cylinder, so when a storm passes, measurements are made and then recorded.

It is crucial that your readings are precise because various professionals may rely on them. But before we proceed, you need to understand how a rain gauge works.

It has three main parts, the funnel, measuring tube, and overflow tube, all supported by a mounting bracket.

When there is rain, the funnel directs water to the measuring tube designed to magnify the measurements. It holds an inch of rainfall water when filled to the brim. When the rainwater exceeds an inch, the excess water will collect in the overflow tube.

You may notice that the surface of the water looks curved. That is the meniscus brought about by surface tension when water comes into contact with the tube’s sides. For the sake of accuracy, always take the readings of the lower meniscus.

How to Record the Rain Gauge Readings

Do not pour the overflow water away because it makes part of the readings. When the measuring tube is chock-full, we record an inch of liquid precipitation. Pour the overflow water into the measuring tube and total up the readings.

A challenge may arise when interpreting the readings, especially if the tube wasn’t filled to the brim. For instance, if the lower meniscus reads 0.40, you should record that you had four-tenths of an inch of water per unit area.

How to Read a Rain Gauge with a Float

Ever since the rain gauge invention, several modifications have been made to make the instrument better and more accurate. Some rain gauges are designed with a float so that when it rains, the float rises to mark the measurement. Some people find it quite tricky to see the meniscus since the water and the tube are colorless.

Often the float is brightly colored. Therefore, when the rain falls into the rain gauge, the float will rise from the bottom as the water rises. Take the readings at the bottom of the float, where it is in contact with the water. That is the accurate reading of the amount of liquid precipitation or fallen rainfall per unit area.

How to Read a Digital Rain gauge

With each passing day, technology advances, and it is always for the better. Trying to solve human problems while making the world a better place. On the forefront is meteorology, trying as much as possible, and not being left behind by other sectors. The invention of the digital rain gauge was a huge breakthrough.

It doesn’t require you to go out every day packed with a pen and notebook taking rainfall measurements. Most digital rain gauges are wireless, transmitting everyday precipitation data to a digital display in your house. All you have to do is observe the readings whenever you want. In fact, it holds on to previous rainfall records. If you wish, you can access weekly, monthly, or even yearly records.

Basically, there is no need for pen and paper unless you want to use the data for other statistical variations.

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Types of Rain Gauge

Over the years, the rain gauge has evolved into two main types.

  1. The recording type
  2. The non-recording type

Some people would call the rain gauge the pluviometer, ombrometer, or udometer. All of them are correct names referring to this instrument. They all measure the amount of rainfall but some record the readings automatically, while for others, you have to take the interpretations physically every day.

The recording type Rain Gauge

The amount of rainfall or liquid precipitation is recorded automatically. Hydrologists and meteorologists would refer to this type as integrating rain gauge. The name is because the instrument records the collective amount of rainfall over a certain period. There are three kinds of recording-type rain gauges.

  1. Floating type
  2. Weighing bucket type
  3. Tipping bucket type

 

  1. Floating type Rain Gauge

Often you will hear people referring to it as the syphon type rain gauge. It comprises a funnel that receives the rainwater, which accumulates into a container. In the container, there is a floating device that rises whenever water rises. When it reaches the top of the container, the connecting pipe or the siphon drains out all the precipitation.

As the water rises inside the container, the movement is recorded by a pen located inside the drum. The pen is attached to the float, which plots the graph inside the drum rotating in a clockwise direction.  Each time there is rainfall, the activity is recorded, forming a curve. The curve is what most would refer to as the mass curve of rainfall.

  1. The Weighing Bucket Type Rain Gauge

The weighing bucket is the most common recording type of rain gauges. The concept is similar to that of the floating type. However, the weighing type uses the weight of water instead of a float. There is a funnel that collects water to the bucket mounted on a weighing instrument.

When it rains, the bucket’s weight makes it moves, and the activity is mechanically transmitted to a pen that plots a curve on a clockwise rotating chart. The rotating chart is actuated with the rotation of a clock. Therefore the recording shows the value of rainfall in a given area over a certain period.

  1. Tipping Bucket Type

It is one of the most ancient instruments used to measure the amount of rainfall. The tipping bucket type comprises two buckets balanced on a fulcrum and a funnel that draws water into one of the buckets. Usually, the bucket doesn’t hold much water. Therefore, when it is filled, it loses balance and tips on one side, filling the other bucket with the water.

It goes back to position to be filled again for the next round of readings. Whenever the bucket tips and fill the other bucket, a switch sends electric signals to a pen that then plots to a clock actuated graph. The graph shows the value or the amount of rainfall over a certain period.

FAQ

What are the units of a rain gauge?

Although water is measured in volume, the rain gauge measures the water in either millimeters, centimeters, or inches. Most rain gauges, however, measure the unit of rainfall in millimeters per square meter.

Who invented the rain gauge?

The rain gauge is one of the most ancient weather recording instruments. It was used by the Indians and the Jews in the 4th century BC. However, the first standard rain gauge was invented in Korea, and then in 1662, Christopher Wren became the first British to invent the tipping bucket rain gauge.

Where should I put the rain gauge?

Place the rain gauge in an open location away from obstacles such as trees and buildings, which may affect the readings.

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Bottom Line

The invention of the rain gauge has proved to be very crucial, especially in weather study. As you take the readings, ensure you do it carefully because they could be used by professionals such as engineers and farmers. The two types of rain gauges, the recording, and the non-recording type, all work perfectly by providing precise data.

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