Rainfall Measuring Instruments

For meteorologists, hydrologists and even the casual gardener, measuring liquid precipitation can provide vital information. There are many tools and instruments available to measure rainfall; these instruments are known as rain gauges or udometers. They range from inexpensive to high tech, and some are even decorative. Different models offer different features, including expanded weather information and remote access. For best results, a rainfall measuring instrument should be placed in an open area and brought in during major storms.

The first rainfall measuring instruments were developed hundreds of years ago, and the basic design has only changed slightly. Most gauges are constructed of glass and brass, as these materials are highly weather resistant and allow you to mount the gauge either on a tree or a post. A funnel is attached to a granulated cylinder with a standard diameter of two centimeters. Rainfall is then measured by the water collected in the glass cylinder, which may be encased within a larger cylinder to catch overflow.

A weighing gauge, as it sounds, measures the mass of precipitation in an outdoor storage bin. These can be used to measure rain, sleet or snow, and are sometimes more costly than a traditional brass cylinder. They are also significantly larger, and because they are often mounted in cement (particularly for scientific or government weather studies) can withstand more intense weather patterns and storms. A sensor or vibrating wire may be used to measure and record the mass of the precipitation.

The tipping bucket is a type of rainfall-measuring instrument, primarily used to determine how heavy a period of rain was during a specified amount of time. Rain drops pool on a small collector spout, which tips like a seesaw when it reaches a certain level and funnels the water out. This tipping, which usually occurs around a fraction of an inch of rain, sends a signal to a pen that records the time of the tipping. More tipping in a short amount of time indicates heavy rainfall. However, this system is less accurate due to false tips and the inability to gauge precisely how much rainfall occurred in the long term.

On the more advanced side of rainfall measurement are digital weather sensors. These devices, which can cost up to $200, display time, date, weather forecast, temperature, humidity, dew point, wind speed and direction and air pressure, in addition to rainfall data. Many can connect wirelessly to a home computer to store weather data and even create analytical charts and graphs. Some are even solar powered. They use a laser diode or internal tipping cups to digitally measure rainfall.