What does a Rain Gauge Measure and How It Works

Measuring rainfall is a long-drawn practice first performed as back as the 4th century. Records were kept even then for comparing and weighing through various methods. It was in the 13th century that the mechanism of "rain gauge" was invented. Since then, the fundamental unit of rain gauge has been developing across different regions in different ways. However, the concept and purpose remain the same.

how does a rain gauge work

What is Rain Gauge? 

Rain Gauge is a meteorological instrument that is used by meteorologists and hydrologists to measure the rain precipitation in a given amount of time per unit area. It is also known by the names of udometer, pluviometer, and ombrometer. 

The instrument has an unembellished design that consists of a collection container that is placed in an open area that will serve the purpose of a recipient. While collecting the rain in this small container is assumed that the same amount of rain precipitation is occurring all around the container. Hence, the area covered by the container does not make any difference in the final calculation.

Even so, the container should be of adequate size, being neither too small nor too big. The precipitation is measured in millimeters(mm).The rain gauge can be of different types, the most popular design being a standard cylindrical vessel. It has been made in such a way that the container does not allow the water to be evaporated before the measurement has taken place. 

Within a large geographical area, standard instruments are used in each region to avoid any sort of discrepancies, as it may eventually lead to faulty large-scale observations. This job of designing a standard rain gauge is given to the World Meteorological Organization, which plays an effective role in providing standard designs that are expected to be opted by everyone.

As I said, rain gauges are of different types, and despite there being a standard rain gauge, in some parts of the world, other types have been proven to be more efficacious. In this article, we will discuss each type of rain gauge and how they function.

Types of Rain Gauges

Rain Gauges fundamentally measure the rain precipitation, and there are several types of rain gauges, each one performing differently. Yet one thing can be assured that from all the methods, you will get a near accurate intel on the amount of rainfall in your area.

Although there are several kinds of rain gauges in general, some of them indigenous mechanisms which occur only in certain specific regions, there are three broad types of rain gauges. They are:

  • Standard Rain Gauge,
  • Tipping Bucket Gauge
  • Weighing Gauge. 

How Does a Rain Gauge Work?

Each type of gauge performs its primary function of measuring rainfall and a few distinctive functions. Let us discuss this in detail. 

Working of Standard Rain Gauge: 

This gauge for measuring rainfall is used so widely that even meteorological departments have opted for this method. In this mechanism, an 8-inch diameter funnel-shaped or cylindrical collected is linked with a measuring tube and is placed in an open area where it can receive rain.

This design is further kept into a larger outer container in case the inner container starts overflowing. Although there is no clearly defined size of the collector mentioned in any of the WMO pamphlets, it has been advised that the collector should neither be too small nor too big. Rainfall is generally measured by measuring the height of the water in the inner cylinder.

The excess water collected in the outer container is poured into another container wherein the measurements are further taken. This gives one the total rainfall. Some measures are taken to avoid any kinds of leakage, so the observations are not contaminated in any way. The rain gauge performs its function by magnifying the rain by a factor of 10. Magnification of rain helps in attaining accurate measurements.

Working of Tipping Bucket Rain Gauge: 

The operation of a tipping bucket rain gauge is completely different from the standard rain gauge. While the design of the standard rain gauge is simple and unembellished, the design of the tipping bucket rain is considerably more comprehensive. Even the accuracies of both differ with standard rain gauge being slightly more accurate.

The design of the tipping bucket rain gauge is that of a seesaw. You have a funnel that collects the rain and transfers it to a different small container. This design may underestimate heavy rain when a definite amount of rain is caught by the funnel, the shaft tips, and does the trick of measuring the amount. This may not give accurate figures because if rainfall stops before the shaft moves, you may get faulty data.

The distinctive feature of the tipping bucket rain gauge is its tendency to estimate the nature of the rain, that is, if the rain is light, medium, or heavy. The basic design of Tipping Bucker Rain Gauge has developed over time, like any other rain gauge, but the underlying mechanism remains the same.

Working of Weighing Rain Gauge:

A weighing gauge is a unit consisting of a storage bin that is used to record the mass. The mass is measured using a rotating drum-like object, and this design is considered best for climatology use, as recognized by the New York National Weather Service office.

These gauges are accurate in measuring the intensity of rainfall, which is why it is considered better than the tipping bucket rain gauge. The weighing mechanism of the weighing method allows you to measure the time and depth both at the same time.

Unlike the tipping bucket rain gauge, the weighing gauge can also measure other forms of precipitation, such as hail and snow, which is why they are more expensive and high-maintenance.

Conclusion: 

Measuring rainfall has become essential for the follow-up proceedings, such as determining the climatic conditions of a region and weather forecasts. Due to so much depending upon the measurement of rainfall over an area, it is essential to have precise data. Faulty data may lead to other faulty observations.

Thus, choosing an accurate means of measuring rainfall is essential. The Standard Rain Gauge has been credited by the World Meteorological Organisation, and also the meteorological departments across the states have recognized it as the most accurate and precise mechanism.

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