The Community Collaborative Rain, Hail and Snow Network (CoCoRaHS)—A Great Way to Learn and Teach about Our Climate

The Community Collaborative Rain, Hail and Snow Network (CoCoRaHS) has grown from a small local network of a few dozen volunteers in northern Colorado to a network of well over 1000 active participants and growing rapidly. The network now encompasses almost all of Colorado and Wyoming as well as much of Nebraska. Kansas and New Mexico are now joining. A high density network focused on accurate measurements of rain, hail and snow, is a great supplement to existing observing networks and is yielding many useful results as well as new research and teaching opportunities. With every day's precipitation online in map form, the fascinating and always-differing patterns of precipitation are evident to scientists as well as the general public. Data are being used in assessing water supply and demand by local utilities and water resource managers. Dense networks afford helpful information to hydrologists assessing storm water runoff and peak flows. Timely reports of heavy rain and hail help meteorologists issue appropriate severe weather warnings. Accurate local rain and hail observations provide ground-truth data for testing and evaluating new algorithms for estimating rainfall and hail severity from radar. Teachers are getting students involved in the project to provide opportunities for collecting data for real research.

Several examples of recent findings on rain, hail and snow characteristics in the Rocky Mountains and Central Great Plains will be presented. For example, during calendar year 2004, measurable precipitation fell somewhere in the state of Colorado on 306 days. However, on only 94 days did precipitation fall at more than half of the reporting stations in the state, pointing out the localized nature of precipitation in this region. Similarly, while most individual locations received hail on only 2-5 days during the year, over the state as a whole, hail was reported on 118 days in 2004. More data analysis will be described, and goals for the future will be presented.