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Monthly CoCoRaHS Precipitation Summaries |
What is CoCoRaHS?
CoCoRaHS is an acronym for the Community Collaborative Rain, Hail and Snow Network. CoCoRaHS is a unique, non-profit, community-based network of volunteers of all ages and backgrounds working together to measure and map precipitation (rain, hail and snow). By using low-cost measurement tools
(including a manual rain gauge), stressing training and education, and utilizing an interactive Web-site, the goal of CoCoRaHS is to provide the highest quality data for natural resource, education and research applications. CoCoRaHS has observers in all fifty states.
The Sawgrass Key weather station is automatic, so why measure rainfall with a maunal rain gauge for CoCoRaHS?
CoCoRaHS does not encourage the use of automatic rain gauges to report 24 hour precipitation totals. Rain gauges are not all created equal and do not all report the same. The Colorado Climate Center has been involved in rain gauge studies for many years and have had dozens of volunteers test their automated gauges against either the CoCoRaHS 4" diameter gauge or the National Weather Service (NWS) 8" diameter Standard Rain Gauge. CoCoRaHS has also tested NWS Automated Surface Observing System tipping bucket rain gauges (not unlike the tipping bucket gauges that come with most home weather stations, but sturdier and a lot more expensive).
While the NWS and CoCoRaHS gauges compare quite well with each other (tests indicate the CoCoRHS gauge has a collection efficiency of 101-105% compared to the standard NWS gauge), the majority of automated rain gauges, when summed over several months or years, report less precipition than actually fell by a significant amount -- sometimes 25% or more. Moreover, none of the automated gauges work well in areas that receive snow. This is not acceptable for the CoCoRaHS project because they are interested in observing and understanding natural precipitation variability, as accurately as possible.
Generally, the automated Sawgrass Key Davis Vantage Pro2 tipping bucket rain gauge and CoCoRaHS manual rain gauge, which are mounted right next to each other at the same height, vary by less than 5% during light to moderate rainfall. During heavy rain events like typical Florida thunderstorms, the Davis rain gauge typically measures 20% less than the CoCoRaHS rain gauge which is consistent with findings from the Colorado Climate Center. Since September 2008, the automated tipping bucket rain gauge has measured 15% less than the CoCoRaHS manual rain gauge.
Therefore, we provide the following summaries of CoCoRaHS rainfall measurements as part of the Sawgrass Key Weather Station.
| Click on a link below to look at tabular data for a specific month/year |
