Rain gauges
Introduction
A rain gauge is a type of instrument used by meteorologists and hydrologists to gather and measure the amount of liquid precipitation over a set period of time. It is also known as a pluviometer, ombrometer, or udometer. The data collected by rain gauges plays a crucial role in weather forecasting and climate study, as well as in the management of water resources.
History
The first known records of rain gauges are from the Ancient Greeks, who used simple tools to measure rainfall. However, the invention of the standardized rain gauge, often attributed to the Korean scientist King Sejong the Great, occurred in the 15th century during the Joseon Dynasty. This gauge, known as the Cheugugi, was used to determine tax rates based on the predicted rice production.
In the 17th century, Richard Towneley and Christopher Wren developed the tipping bucket rain gauge in England. This design is still widely used today due to its simplicity and accuracy.
Types of Rain Gauges
There are several different types of rain gauges, each with their own advantages and disadvantages. The most common types include the standard rain gauge, the tipping bucket rain gauge, the weighing rain gauge, and the optical rain gauge.
Standard Rain Gauge
The standard rain gauge, also known as a graduated cylinder rain gauge, is the simplest type of rain gauge. It consists of a graduated cylinder with a funnel at the top, placed in an open area. The rainwater collected in the cylinder is measured in millimeters.
Tipping Bucket Rain Gauge
The tipping bucket rain gauge is a more complex type of rain gauge. It consists of a funnel that directs rain into a small seesaw-like container. After a certain amount of water has been collected, the container tips, dumping the water and sending an electrical signal.
Weighing Rain Gauge
The weighing rain gauge, or weighing precipitation gauge, measures the weight of the precipitation instead of the volume. This type of gauge can measure any form of precipitation, including rain, snow, sleet, or hail.
Optical Rain Gauge
The optical rain gauge uses a row of collection funnels and a light source to measure rainfall. When a raindrop falls through a funnel, it interrupts the light beam, and the amount of light received by the sensor decreases. This change in light intensity is then converted into rainfall measurements.
How Rain Gauges Work
Rain gauges work on the principle of accumulation. In a standard rain gauge, the rain falls into a funnel that directs the water into a graduated cylinder. The level of water in the cylinder represents the amount of rainfall, usually measured in millimeters or inches.
In a tipping bucket rain gauge, the rainwater fills a small bucket within the gauge. Once the bucket reaches a certain level, it tips over, emptying the water and sending an electrical signal that is recorded as a rainfall event.
In a weighing rain gauge, the weight of the collected precipitation is measured. The weight is converted into an equivalent depth of water that would cover a flat, horizontal surface, giving the amount of rainfall.
In an optical rain gauge, the amount of light received by the sensor decreases as raindrops fall through the funnels. This change in light intensity is converted into rainfall measurements.
Uses and Applications
Rain gauges have a wide range of uses and applications. They are used by meteorologists for weather forecasting and by hydrologists for water resource management. They are also used in agriculture to help farmers manage irrigation and plan for crop yields. In addition, rain gauges are used in scientific research to study climate patterns and changes.
Maintenance and Calibration
Rain gauges require regular maintenance to ensure accurate readings. This includes cleaning the gauge to remove debris and checking for damage. Calibration of rain gauges is also important to ensure accuracy. This is typically done by comparing the readings from the rain gauge with a known standard.