CoCoRaHS: Better Data, Better Climate Preparedness

Jackson Parr, climate hazards planning educator with the UW-Madison Division of Extension, installs a precipitation gauge volunteers monitor to check rainfall or snowfall amounts for the CoCoRaHS Network, a national weather monitoring network of volunteers. Photo by Katie Hohmann.

Volunteer rainfall monitoring program makes scientists out of citizens

by JACKSON PARR, climate hazards planning educator, University of Wisconsin-Madison Division of Extension

If you have ever stood in the sunshine on a dock on the bay and looked out to see a rainstorm approaching, then you have pondered the spatial distribution of rainfall intensity and its importance in our understanding of climate, if only subconsciously. 

Rainfall must start at some point and stop somewhere else. All along that rain cloud’s path, raindrops of different sizes fall at different speeds. These differences matter when it comes to everything from operating the Forestville Dam and preparing for inundated roads in Sturgeon Bay to watering a vegetable garden and deciding when it’s time to cancel dinner reservations on the patio. 

The Community Collaborative Rain, Hail and Snow Network (CoCoRaHS) is a national weather monitoring network of volunteers that use precipitation gauges to check rainfall or snowfall amounts and submit that data to the national database. Every morning, volunteers check the gauge mounted outside their house and record how much rain fell in that spot over the last 24 hours. The more rain gauges and volunteers across the peninsula, the clearer the picture we have of how a rainstorm behaves as it moves across the bay and out to Lake Michigan. Recording dry rain gauges is equally important in identifying localized drought conditions. 

“With the peninsula you get these lake effect bands and the local differences can be huge,” said Kevin Erb, conservation professional training program director at the University of Wisconsin-Extension and State Coordinator for CoCoRaHS. “The need for localized data is much greater where we have these lake effect snow and rain storms, which you just don’t see other places.

CoCoRaHS is supported by the National Weather Service (NWS), the National Oceanic and Atmospheric Association (NOAA) and other local, state and federal agencies. The data that volunteers submit is used to inform flood risk advisories, drought outlooks, streamflow monitoring, and more. Researchers use the data in Door County to help model the movement of groundwater contaminants. The Door County Climate Change Coalition uses the data to plan its watering resources during the organization’s annual tree planting events. My mom checks her rain gauge because I set it up for her and she likes to be helpful. The possibilities are endless. 

Trends Revealed

The frequency and severity of rain events is increasing across the state. In Door County, the previous decade saw the highest frequency of 2-inch rain events since monitoring began in 1905. That amount of rain should only fall on the county once per year based on historic data, but they have happened about twice as frequently in the past decade.

For context, we would expect a 1-inch rainfall to happen dozens of times each year, whereas a 3-inch rainfall is only predicted to happen about once every five-to-10 years.

The primary, long-term rain gauge for the county is located a few miles north of Sturgeon Bay. Without a network of rain gauges across the county, weather and climate models would be over reliant on what is happening at that single point, blind to the nuance across one of the most geologically unique and climatically varied counties in the state.

In addition to CoCoRaHS, there is an expanding network of sophisticated weather monitoring stations across the county and the state. This mesonet, branded as Wisconet for the state network, collects rainfall and other metrics, reporting back to a central database every five minutes. The data is publicly available and can be found at wisconet.wisc.edu/. Wisconet and CoCoRaHS both play an important role in taking a climate snapshot of Door County. 

Anyone with access to a view of the sky and a reliable alarm clock can participate in CoCoRaHS. Here’s how:

• Get the standard CoCoRaHS rain gauge from WeatherYourWay.com. That way, all volunteers are using the same equipment to take accurate readings.
• Mount that rain gauge somewhere easily accessible with a clear view of the sky. 
• Create an account on cocorahs.org. 
• Begin monitoring by picking a time each morning between 7:00-9:00am to check your rain gauge and record your data on the CoCoRaHS website. We’re looking for total precipitation in a 24-hour period, so whether it’s 7:00am or 9:00am, just be consistent. If you sleep in for a day or leave town for a month, just start recording again when you’re able. It’s just as important to log “zero”, as that helps us understand droughts. 
• Your observation will be publicly viewable on a national map immediately, but you’ll need to be somewhat consistent over a few months, or more than 100 observations, before National Weather Service and others consider your data reliable and begin using it in their own processes.

“It’s an opportunity for people to invest less than a minute a day and feel they are having an impact and contribution to science,” said Erb.There is a dedicated team of scientists and specialists across the state available to help you participate in CoCoRaHS. If you have any questions on the program or how to participate, contact Jackson Parr, Climate Hazards Planning Educator with the University of Wisconsin-Madison, at [email protected].