CoCoRaHS: A national climate observing system of volunteer observers providing a “gauge-full” of data for climate applications

CoCoRaHS (The Community Collaborative Rain, Hail and Snow Network), is celebrating its 10th anniversary in 2008. This fast-growing nationwide project now engages over 10,000 volunteers of all backgrounds and ages in thirty-four states who measure precipitation in their own backyards. Within the next year, the network will most likely become the largest supplementary source of daily precipitation observations in the United States. With this national focus, CoCoRaHS is now able to show regional precipitation patterns as they sweep across the country and detailed local patterns on a sub-county level.

Applications of CoCoRaHS data include seasonality of size distributions of daily rainfall events as well as probabilities and aerial extent of extreme events. CoCoRaHS allows quick and easy hail analysis, such as stone size distribution, storm duration and time of day distributions and how these vary regionally across the country. Measuring snow is challenging, but CoCoRaHS is showing that volunteer effort is yielding high quality data suitable for research, analysis and data quality control.