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Instrument Description

Rain Gauge


Summary

A rain gauge collects and records precipitation (rain and snowfall).

Table of Contents

1. Sensor/Instrument Overview
2. Sensor/Instrument Layout, Design, and Measurement Geometry
3. Manufacturer of Sensor/Instrument
4. Calibration
5. References
6. Document Information

1. Sensor/Instrument Overview

Sensor/Instrument Name

Rain gauge

Sensor/Instrument Introduction

The rain gauge is an instrument used to collect precipitation. In some cases, human observers determine precipitation amounts. With newer gauges, accumulation is measured automatically.

Sensor/Instrument Mission Objectives

The collection of precipitation data is useful for verification of climate model simulations, investigations of the global hydrological cycle, and climate change detection studies.

Key Variables

Precipitation

Scanning or Data Collection Concept/Principles of Operation

Standard (or Official) Rain Gauge

For 24-hour collection, a standard rain gauge is typically used. This is a hollow metal tube with an open top that collects precipitation. The observer uses a ruler to measure the depth of the water in a small inner tube. In the winter, the small tube is taken out, and snow falls directly into the large tube. Then, snow is melted down and poured into the small tube to be measured.

Automatic Rain Gauge

The tipping bucket gauge automatically tips when a certain amount of precipitation accumulates inside of it. Total precipitation is determined by the number of tips.

Another type of automatic rain gauge is tall and typically cone-shaped. It collects all types of precipitation continuously into a bucket. Its weight presses down on a scale, and every 15 minutes, a hole is punched in a ticker tape or a marking is made on paper by pen to record the bucket's weight. This is useful for hourly collections.

2. Sensor/Instrument Layout, Design, and Measurement Geometry

Sensor Description

The standard rain gauge is comprised of two basic elements: A funnel or standard 8-inch opening at the top and a collection device at the bottom. Precipitation measurements may be obtained using a ruled edge on the collection container. Or precipitation may be measured by hand using a standard ruler. Automatic rain gauges (tipping and weighing gauges) are attached to automatic counters or scales. The rain gauge is placed in areas free and clear of overhead obstruction, and oftentimes, includes a surrounding screen that mitigates the effects of wind.

3. Manufacturer of Sensor/Instrument

Manufacturers of the rain gauge vary.

4. Calibration

Specifications

Typically, rain gauges are calibrated to meet National Weather Service or World Meteorological Organization specifications for statistical accuracy.

Standard gauge: Accumulation measurements (in mm) are obtained using a standard ruler or the ruled edge on the rain gauge's container, and are recorded on a regular basis by human observers.

Automatic gauge with attached or remote counter device: The precipitation amount necessary to trigger the tipping bucket mechanism is set by the manufacturer of the gauge. Timers on the automatic counter device are programmed by either manufacturer or user.

5. References

Aquatic Eco-Systems, Inc. 1998. Rain gauge, Internet page. http://www.aquatic-eco.com/products/rg6/rg6.htm.

GENEQ. 1998. The Rainew tipping bucket rain gauge, Internet page. http://www.geneq.com/catalog/en/rainewg.htm.

GENEQ. 1998. Recording rain gauges, Internet page. http://www.geneq.com/catalog/en/rraing.htm.

Global Precipitation Climatology Center. 1998. Readme for the Global Precipitation Climatology Center (GPCC) rain gauge analysis for the Global Precipitation Center Project (GPCP), Internet page. http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/hydrology/readme_html/gpcc_rain_gauge_readme.html

NWSFO Jackson Cooperative Observer Program. 1998. Gauges, Internet page. http://www.jannws.state.ms.us/coop4.html.

Squitter Electronics, Inc. 1998. Tipping bucket rain gauge, Internet page. http://www.spdweb.com/squitter/tipping.htm.

USA TODAY. 1997.Weather: Old fashion device measures rainfall, Internet page. Researched by Chad Palmer. (October): http://www.usatoday.com/weather/wrngauge.htm.

USA TODAY. 1997.Weather: Rain gauge uses gravity to measure rainfall, Internet page. Researched by Chad Palmer. (October): http://www.usatoday.com/weather/wtipgage.htm.

Weathermall. 1998. Wireless rain gauge--single display, Internet page. http://www.weathermall.com/wsc/wirel1.htm.

6. Document Information

Document Revision Date

Revision Date: May 4, 1998
Review Date: April 22, 1998
Document ID: NSIDC-0059
Document Curators: NSIDC Writers
Document URL: http://nsidc.org/data/docs/daac/rain_gauge_instrument.gd.html