Interesting Facts About the Rain Gauge

Have you also been aroused by why we need to determine the amount of rain? The answer is quite simple; it is necessary to evaluate the amount of rainfall, as our agriculture highly depends on it. Certain plants require high rainfall for a more extended period, whereas others require the least amount of rainfall and spoil in excess water. Many crops need moderate rainfall to grow efficiently. Therefore, rainfall plays a significant role in determining the quality and quantity of the crops. Now, we know that the measurement of rainfall is necessary, so there must be an instrument to measure it. Well, there comes the rain gauge. It is a meteorological instrument that measures the precipitation over a unit area for a given time. The records of rainfall date back to ancient Greeks, and history consists of several mentions of such instruments that measure the rainfall. 

Types of rain gauges

The two primary categories of classification of rain gauges are as follows:

• Non-recording type rain gauge: This type of rain gauge is very commonly used for meteorological purposes. This consists of a cylindrical vessel with a diameter of 127 mm and a base up to 210 mm in diameter. The funnel consists of a circular brass rim at the top, of diameter 127 mm. There is a receiving bottle of approximately 70 to 100 mm in height. The funnel shank is placed within the neck of this receiving bottle. This bottle can have a capacity of 100 mm or more according to the rainfall. The readings are often taken 3 to 4 times daily.

The graduated measuring glass will measure the water present in this receiving bottle. It is necessary to do this measurement at a regular time daily. Moreover, protect the instrument from dirt accumulation, affecting the readings. 

• Recording type rain gauge: These types of rain gauges give automatic records of the rainfall without any interference from the readings of the bottle. Moreover, it does not require any mechanical work to measure the precipitation amount.

The sub-categories of recording type rain gauges are as follows:

• Tip-bucket type rain gauge: This rain gauge comprises a sharp-edged receiver of 30 cm. A funnel is present at the end of this receiver. There are two buckets under this funnel arranged so that when bucket one receives 0.25 mm of water, it starts to tip and discharge the water into the container. As a result, bucket two comes under the funnel. This generates the electric circuit, which causes the pen to mark on the recording sheet. These recordings are stored at the gauge station.

Demerits of tip-bucket type rain gauge: It is difficult to record the number of tips during the high intensity of rainfall that gives too close signals. Moreover, rusting and dirt can affect the normal reading of the device.

• Weighing bucket-type rain gauge: The most commonly used recording type rain gauge is the weighing bucket-type rain gauge. They give the plot of rainfall against the time. The curves formed due to these rain gauges are termed the mass curve. They consist of a bucket for receiving the precipitation. A lever balance or spring balance supports this bucket. The increase in weight causes the movement of the bucket. This movement causes the pen to trace markings on the clock-riven chart. 

Demerit of weighing bucket-type rain gauge: Heavy rainfall can lead to the overflow of the bucket, altering the readings. 

• Natural syphon-type rain gauge: Natural syphon-type rain gauges, also known as floating syphon-type rain gauges, work similarly to the weighing bucket-type rain gauges. It has a rectangular container for collecting the water, which enters this container through the funnel. The float present at the bottom rises with the water level. This activates the clockwork, and the movement gets recorded by the pen. When the float reaches the top due to the continuous rise in water, the siphon releases all the water from the connecting pipe. 

Demerit of natural syphon-type rain gauge: Any defect in the arrangement can lead to severe errors. 

Conclusion

As we know, measuring rainfall is essential for proper and high yield of crops. Therefore, it is necessary to have an instrument that can measure it. A rain gauge is a meteorological device that measures the amount of precipitation in a unit area for a given time. There are two primary rain gauge categories: recording type and non-recording type. The recording type gauges further have subtypes, such as tip-bucket type, weighing-bucket type, and natural-syphon type rain gauges.