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Volunteers aid residents in 'community weather network'

September 17, 2009

Nearly 300 weather watchers signed up in the first two weeks of the Arizona program; more are needed

Farmers, ranchers, emergency management personnel and the National Weather Service all count on climate information that often is provided by citizen weather observers as part of the Community Collaborative Rain, Hail and Snow Network, better known as CoCoRaHS.

September marks the expansion of CoCoRaHS into Arizona, the 48th state to join the network.

"We've had more than 290 volunteer observers sign up since Sept. 1, with many already taking measurements, and we are looking for more volunteer weather observers in all parts of the state," says Nancy Selover, Arizona State Climatologist and coordinator for the new Arizona CoCoRaHS.

CoCoRaHS, based at Colorado State University and formed in 1998, is a nonprofit, community-based network of volunteer weather observers of all ages and backgrounds working together to measure and report precipitation amounts (rain, hail and snow). By using low-cost and self-provided measurement tools, stressing training and education, and utilizing an interactive Web site, the aim of CoCoRaHS is to provide the maximum amount of data for natural resource education as well as research applications.

"As we say, every drop counts," says Selover.

"The effort in Arizona is especially important due to our extremes of topography and our desert climate, where precipitation is highly localized, particularly during the monsoon," she says. The White Mountains and Mogollon Rim average 40-44 inches per year, while Yuma averages less than four inches per year, Selover notes.

Given that the majority of the state's population lives in the Phoenix and Tucson metropolitan areas, so also do most of the volunteers.

"Since precipitation can be extremely localized, we encourage people in those two areas to continue to sign up, but we also need observers in smaller cities, towns and rural areas," Selover says. "We have very few volunteer observers in Mohave, Coconino, Navajo, Apache, La Paz, Yavapai, Gila, Pinal, Graham, Greenlee, Cochise, Yuma and Santa Cruz counties."

"We know you frequently hear on the news how much rain was measured at an official site, and say to yourself, 'That's not how much fell at my house.' Well, this is an opportunity for citizens to let us know how much rain, snow or hail actually did fall at their house."

According to Selover, nearly anyone can participate in this "fun, educational, community-based project." The basic requirements for being a CoCoRaHS weather observer include:

• Access to the Internet and the ability to browse the CoCoRaHS Web site, which is where observers enter their daily precipitation data, though reports by mail are also welcomed.

• An official-type, inexpensive CoCoRaHS rain gauge, which may be purchased from the group's Web site.

• A good property site with good exposure — as free as possible from tree and obstructions — where the rain gauge can be located about five feet off the ground.

• A willingness to enter precipitation data on a daily basis between 6-9 a.m. on the CoCoRaHS Web site.

Selover explains that while CoCoRaHS doesn't offer a pay check to volunteer observers, there are other benefits. For example, one of the neat things about participating in the CoCoRaHS network is walking away with the feeling of making an important contribution that helps others.

CoCoRaHS notes that volunteers who provide daily precipitation data help fill in a piece of the puzzle that affects many people in their part of the state in one way or another. CoCoRaHS also provides an opportunity to learn more about weather and water by participating collaboratively with local scientists.

Persons, including children, who are interested in becoming a CoCoRaHS observer can sign up online at by clicking the "Join CoCoRaHS" emblem.

Questions may be addressed to Selover, who is the state climatologist and a research professor at Arizona State University in the School of Geographical Sciences and Urban Planning. Her e-mail is and her phone number is (480)965-0580.

CoCoRaHS, through Colorado State University, is supported nationally through the National Oceanic and Atmospheric Administration (NOAA).