CoCoRaHS: Supplemental Volunteer Precipitation Observations for Mountainous Regions

CoCoRaHS - the Community Collaborative Rain, Hail and Snow Network -- was launched in 1998 in response to a local extreme rainfall event and subsequent flash flood at the base of the eastern foothills to the Rocky Mountains in northern Colorado in July 1997. Since then, CoCoRaHS has expanded nationally and now involves nearly 15,000 volunteers in all fifty states measuring precipitation in their own backyards. While the majority of these volunteers are located in the plains and coastal areas of the U.S., more than 2500 active volunteers live in or adjacent to mountainous areas of the U.S. High concentrations of volunteers are found throughout portions of the Appalachian Mountains, in populated regions of the Rocky Mountains and in portions of the Pacific coastal ranges, the Sierra and the Cascades. Despite the fact that CoCoRaHS gauges are limited to populated areas of the U.S., the large number of stations and the enthusiastic commitment of volunteers offers a substantial new data set at a very low cost to provide greater spatial resolution in precipitation monitoring. CoCoRaHS data are ingested daily by the National Weather Service, River Forecast Centers and the National Climatic Data Center. These supplemental data are routinely being used in many ways including hydrologic prediction, flood warnings, in quality control of official U.S. precipitation data sets and in the production and calibration of remotely sensed precipitation products. CoCoRaHS has already helped document a number of extreme precipitation events (both rain and snow). Examples will be shown and future plans will be described. The CoCoRaHS Rain Gauge holds up to eleven inches of precipitation.