It’s all a matter of perspective: measuring rain from the ground.
Citizen scientists can contribute much to the understanding of rainfall patterns by reporting precipitation totals at their location. The Community Collaborative Rain, Hail and Snow Network, or CoCoRaHS, collects reports of daily rain, hail and snow events from citizen scientists that are used by a variety of organizations and individuals ranging from the National Weather Service to insurance adjusters and water resources managers. Citizen scientists can join the CoCoRaHs network and contribute data or simply examine the data archives to inquire about local rainfall patterns. CoCoRaHS originated in 1998 at the Colorado Climate Center at Colorado State University. It now has over 12,000 observers in thirty-nine states. (Adapted from What is CoCoRaHS?)
- Rain Gauge: CoCoRaHS Website has a list of suppliers, approximately $20–25
- Wooden 4" X 4" Post with a beveled top for mounting gauge
- Tools for placing the post into the ground such as a shovel, drill, screwdriver, hammer, nails/screws and level to attach gauge to post.
- Detailed map of your location
- Google Earth (to identify the latitude and longitude of your test site)
- Data sampling sheet, available in the Tools section of this guide and from idoscience.net, where you can share your observations with other citizen scientists.
Do not take measurements during a severe storm, flood, or lightning event.
Locate a sampling site
- For accurate measurements, your rain gauge should be placed away from any permanent structures such as fences or buildings; 2-5’ above the ground; away from sprinkler systems, dogs and vandals and be easily accessible so that you can check it on a daily basis. You may be able to place the gauge in your yard, but you may wish to identify other locations within your community as well, particularly if you are interested in studying regional variability in rainfall patterns.
- Using the map, identify possible rain gauge locations at various places in your region. Choose potential locations that are publicly accessible or where you have permission from the land owner to access the location on a daily basis.
- Locate the site(s) in Google Earth. Place the cursor over the sampling site(s) and note the latitude and longitude that appears in the bottom left corner of the Google Earth window. Record this information on the data sampling sheet.
- Select a sample location at the site. Look for objects that might adversely affect your collection of precipitation, as outlined in step one. Use the CoCoRaHS training manual pdf for more detailed specifications.
- Place the post in the ground with the beveled end on top. Using the level, make sure the post does not lean in one direction or another.
- Secure the post to make sure it does not wobble.
- Mount your rain gauge on the post, with the gauge top a few inches above the top of the post. Place a level on the gauge to make sure the rain collector is level when you attach it to the post.
- On your data sheet, note the condition of your rain gauge. Describe the surroundings (distance from trees and buildings).
- If you wish to report your data to the CoCoRaHS network, complete the appropriate paper work to register your location with CoCoRaHS.
Use the CoCoRaHS training manual to learn how to read the gauge.
There are a variety of training options on the CoCoRaHS site. From the home page or resources link, one can download additional training slide shows files. Alternately, go to the Indiana page to listen to a web cast of how to use your rain gauge.
Check your rain gauge daily at 7 am (in your local time zone). The hours of 5-9 am (in your local time zone) are acceptable. Record the amount of rain in the gauge on your data sheet and report your rainfall to the CoCoRaHS Website. For more details review the information on the CoCoRaHS Website.
Do not collect rainfall measurements during a lightning event.
Other measurements that may be of interest are hail and snow. These are also described on the CoCoRaHS Website.