Rain Gauge : A rain gauge is a meteorological instrument used to measure precipitation in its liquid form in a specific area over a predetermined period of time. It is typically used as part of a weather station to measure current and determine future weather conditions, monitoring the water cycle, as well as refining forecasting models.

The Different Types Of Rain Gauges

• Graduated Cylinder Rain Gauge (Standard Rain Gauge)
• Tipping Bucket Rain Gauge
• Weighing Precipitation Gauge
• Optical Rain Gauge
• Acoustic Rain Gauge

1. Graduated Cylinder Rain Gauge

Also known as the standard rain gauge, the graduated cylinder rain gauge is a simple, measured glass cylinder. It is used by all professional weather services in manned stations and is the most accurate way of directly measuring rainfall.

The water gets collected by a cylindrical funnel, from where it flows directly into the graduated cylinder or captured by a container and then poured into a measured cylinder.

This rain gauge has to be measured and emptied on a daily basis, which means it can only be used in a manned weather station.

2. Tipping Bucket Rain Gauge

The tipping bucket rain gauge is an automated rain meter that uses a "tipping bucket" mechanism to measure rainfall. It is used by professional weather services' remote weather stations and is also popular and widely used in home weather stations.

Like a standard rain gauge, it uses a collector funnel with a narrow pipe at the bottom to capture rainfall. From the pipe, the water drops onto a finely-balanced seesaw device with small buckets on each side.

At any point, one of the buckets is positioned directly under the pipe. When enough water collects in the bucket, its weight makes it drops to the bottom and empties itself while lifting the opposite bucket into position under the pipe.

This process keeps repeating as rainwater continues to flow through the funnel onto the buckets. Each time a bucket drops to the bottom, it triggers an electronic switch. In turn, the switch sends a wireless or landline signal to a base station.

Each signal represents a specific amount of rain that has been set up and calibrated in the tipping bucket mechanism. By counting each signal and adding it up, weather stations can calculate the rainfall over any given period.

As the water flows out of each bucket, it drains through predesigned openings in the rain gauge, meaning there is no need for anyone to maintain the system. This advantage makes it ideal for use in remote weather stations, which is also hard to reach.

3. Weighing Precipitation Gauge

A weighing precipitation gauge consists of receiving bucket mounted on a weighing device, usually a mechanical mechanism such as a spring. The rain accumulates in the container, and the increased weight compresses the springs.

The amount of compression gets measured and used to calculate the weight of the water. The measurement can be recorded manually with a pen on a drum or electronically with a data-logger and send to the base weather station via landline or wireless connection.

The weighing precipitation gauge has some advantages over the tipping bucket system, including the ability to capture and measure snow and other solid forms of precipitation. It is also better equipped to handle large downpours.

Most modern systems are also self-emptying, reducing the amount of maintenance required on this type of rain gauge. Some weighing gauges are heated as well, which allows them to melt solid forms of precipitation and prevent a build-up of snow.

4. Optical Rain Gauge

An optical rain gauge consists of a laser/infrared diode and photosensitive sensor situated in enclosed spaces on opposites sides and below a row of funnels that receive rainfall. Each funnel has a small opening at the bottom through which raindrop forms when enough precipitation accumulates inside the container. Once the waterdrop grows large enough, it falls from the funnel and through the space between the laser diode and photosensor.

As the drop falls through the beam of light, it scatters it enough for the photosensor to detect and measure it. These measurements are recorded and send through a landline or wireless connection to the base weather station.

Optical rain sensors have the advantage of not only measuring the amount of rainfall but also the intensity and frequency of the rain through precise detection by the photosensitive detector.

5. Acoustic Rain Gauge

Also known as hydrophones, acoustic rain gauges are used to measure the rainfall over large bodies of water like dams, lakes, and the ocean.

The device itself gets place underneath the water's surface. The hydrophone can sense and measure the impact of the raindrops hitting the surface of the water.

Each raindrop makes a unique sound, depending on its size and speed, which is called a sound signature. An acoustic rain gauge is sensitive enough to detect the different sound signatures to calculate the size and frequency of different raindrops.