Measurements · Meteorology
Precipitation
Also known as rainfall, rain gauge, storm rain
Accumulated precipitation depth.
What it is
What is precipitation?
Precipitation is water falling from the atmosphere to the ground in liquid or solid form (rain, drizzle, snow, sleet, and hail), and it is measured as the depth of water that accumulates on a flat surface, in millimeters, where 1 mm is one liter per square meter. It forms when water vapor in rising air cools, condenses onto particles, and grows into drops or crystals heavy enough to fall. A precipitation total is the accumulated depth over a period (an hour, a day, a storm), and it is distinct from precipitation intensity, which is the rate at which it falls.
Health and operational effects
Precipitation is a first-order driver of flooding, surface-water runoff, erosion, and combined-sewer overflows. It mobilizes pollutants on the ground while suppressing airborne dust. Accumulated rainfall is the input to drainage design, flood warning, agriculture, and water-resource management, and its prolonged absence defines drought.
Operationally, rainfall totals govern construction and earthworks schedules, the triggering of pollution controls at contaminated or industrial sites where runoff must be managed after rain, reservoir and stormwater operations, and crop irrigation decisions. On monitoring sites rainfall is essential context: it explains washout of airborne dust, dilution or first-flush spikes in water quality, and changes in ground and soil conditions that follow a wet spell.
How it is measured
How Precipitation Is Measured
The standard instrument is the tipping-bucket rain gauge: rain funnels onto a small see-saw of two tiny buckets that tips each time a fixed depth, commonly 0.2 mm, collects, sending a pulse. Counting pulses gives accumulation and their timing gives intensity. Tipping buckets are simple, rugged, and self-emptying, but they can under-read in very heavy rain and need heating to handle snow. Alternatives include weighing gauges, which weigh accumulated precipitation and handle snow well, and non-contact optical disdrometers and radar gauges that infer rate from how drops scatter a beam and can also classify precipitation type. Each trades cost against accuracy in snow and at extreme rates.
An instrument on Thiamis3
A third-party instrument connected to a Thiamis gateway, reporting into the same Environet account.
Placing precipitation sensors
Site the gauge in the open with its rim level and clear of wind eddies and obstructions. Accepted guidance is to keep it at a distance of at least twice the height of any surrounding obstacle, since buildings and trees both shelter the gauge and generate turbulence that blows rain and snow past the orifice. Wind-induced under-catch is the dominant error, worst for snow, and is reduced by low, sheltered but unobstructed sites or by fitted wind shields. The rim should sit at a standard height above the ground to avoid in-splashing from the surface.
Where it is monitored
Solutions That Monitor Precipitation
Each one links to the solution page showing what that industry measures it for.
Agriculture & Irrigation
Core parameterRainfall measurement anchors irrigation scheduling and crop-water accounting, telling growers how much water the crop has already received before deciding what to add.
Hydrology, Level & Flow
Core parameterRainfall is the input that drives every hydrological response, so precipitation monitoring is essential context for flood warning, stream gauging, and catchment management.
Weather Stations & Meteorology
Core parameterPrecipitation is a defining weather measurement for forecasting, hydrology, agriculture, and climate records.
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Questions
Precipitation FAQ
How is rainfall measured in millimeters?
A rain gauge collects rain over a known aperture and reports the depth it would form on a flat, impermeable surface, so 1 mm equals one liter of water spread over a square meter. This depth measure is independent of the gauge's size, which lets readings from different instruments and sites be compared directly.
What is the difference between rainfall total and intensity?
The total is how much water fell over a period, in millimeters, while intensity is how fast it fell, in millimeters per hour. The same 10 mm can arrive as a gentle day-long drizzle or a ten-minute cloudburst, and it is intensity, not total, that determines flash-flood and erosion risk.
Why do rain gauges under-read in wind and snow?
Wind accelerating over the gauge orifice carries drops and, especially, snowflakes past it rather than into it, so catch falls short of the true precipitation. The effect is worst for light, slow-falling snow, which is why exposed sites are avoided, wind shields are fitted, and snow is often measured with weighing gauges.
How do I monitor precipitation?
Precipitation is not part of the built-in Aethair sensors, so pair a Thiamis gateway with an external rain gauge or full weather station, sited with proper exposure. Use the configurator to combine precipitation with precipitation intensity, wind, and, for runoff and water-quality work, water sensors in the same configuration.
Monitor Precipitation on the Record
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