Alphabet Soup: CoCoRaHS

As scientists, we tend to get carried away with our acronyms. Sometimes they can be clever (such as Verification of the Origins of Rotation in Tornadoes Experiment, or VORTEX), and others there’s an acronym within an acronym (TOVS is an optical vertical sounder, but the ‘T’ stands for TIROS, which stood for Television Infrared Observation Satellite). In a world of scientific jargon, how are users going to figure out what each acronym means and what function it poses? Well have no fear, I’m here to break down some of these acronyms used to describe weather and climate data sets in which I’m calling: Alphabet Soup.

In our last segment, I highlighted one of the premier datasets archived by NOAAs National Center’s for Environmental Information: GHCN-D. That dataset is unique, because it’s a combination of numerous weather and climate datasets. The dataset with the most stations in GHCN-D is a precipitation based network, and today we will talk about it in more detail.


CoCoRaHS is an interesting acronym on its own. It’s a fluid word with consonants and vowels, but some of the letters are capitalized and some are not. There’s also some duplication in the name (‘Co’), but they don’t exactly mean the same thing. The acronym stands for the Community Collaborative Rain Hail, and Snow network. While temperature is somewhat continuous in space, it is not the same case for precipitation. One side of the town can experience torrential downpours, while the other side is high and dry with little or no precipitation recorded. It’s important for there to be as many observations as possible, to capture these small scale features of precipitation.

In July 1997, there was a devastating flood in Fort Collins, Colorado where the Spring Creek rose above its flood levels and created problems for the area. One of the official weather stations reported 6” of rain in a two day period, sending the station from 10% below normal to about 50% above normal in such a quick span. Unofficial stations in the surrounding area reported higher values, and there was speculation of reports up to 15” of rain. Because there were not enough rain gauges to capture the extent of rainfall, it was unclear how much water fell in the area.

A year later, the Colorado Climate Center began the CoCoRaHS program in the state of Colorado. They asked residents to submit a report of how much precipitation (or lack thereof) occurred in their area, including rain, snow, and hail. Their mission statement is to:

  1. Provide accurate high-quality precipitation data for our many end users on a timely basis.

  2. Increase the density of precipitation data available throughout the country by encouraging volunteer weather observing.

  3. Encourage citizens to have fun participating in meteorological science and heightening their awareness about weather.

  4. Provide enrichment activities in water and weather resources for teachers, educators and the community at large to name a few. 

Standard rain gauge used in the CoCoRaHS project.

Standard rain gauge used in the CoCoRaHS project.

Over time, the network received support from NOAA and NSF, and quickly grew to all 50 states, including Puerto Rico and the US Virgin Islands. Canada and The Bahamas have also gotten involved, making this an international effort. This has become a very successful citizen science project, with over 40,000 stations to date.

If you want to become a CoCoRaHS observer, it’s very simple. Head to the CoCoRaHS webpage and sign up. You will need to purchase a rain gauge, but they are usually under $40 at various online stores. Once set up and properly sited, dump the water out each morning at 7am local time, and report the amount of precipitation that fell (or didn’t fall) online through either a webpage or an app provided by the organization. Afterwards, you can compare your results with neighboring stations, through a web mapping portal. They also provide numerous tutorials to help you report the odd ball information, such as hail and snow depth.

Before anyone asks, YES I do have a CoCoRaHS station, my data is plotted below. For the year 2018, I’ve had 54.37” of rain, which smashes the records…going back to 2014. Since this is such a short term station, it's probably not the best idea to include this in any long term climate monitoring.