A rain gauge is an instrument used to measure the amount of liquid precipitation over a specified time period. Standard, tipping bucket, and weighing gauges are the most common types.
A rain gauge (pluviometer) is a meteorological instrument designed to collect and measure the depth of liquid precipitation falling on a unit area over a defined time interval. The standard non-recording gauge consists of a cylindrical collector with a funnel that directs precipitation into a measuring tube with a cross-sectional area one-tenth that of the collector, magnifying the depth tenfold for accurate manual reading. Tipping bucket gauges use a two-compartment bucket mechanism that tips when a preset volume (typically 0.2 or 0.25 mm equivalent) is collected, generating an electrical pulse recorded by a data logger, enabling continuous, automated measurement with temporal resolution. Weighing precipitation gauges continuously measure the weight of accumulated precipitation, providing high-accuracy measurements of both liquid and solid (snow, ice) precipitation. Gauge placement follows standardized guidelines: the gauge should be in an open area with surrounding obstacles no closer than twice their height, away from buildings, trees, and other obstructions that cause wind effects. Wind-induced undercatch is the most significant source of measurement error, particularly for snow, and wind shields such as the Alter or Nipher shield are used to reduce this bias. Rain gauge networks form the backbone of precipitation monitoring systems and are essential for hydrology, agriculture, and weather forecasting.