Introduction to CoCoRaHS

CoCoRaHS is an online network of volunteer rainfall observers.  Here is the description directly from the CoCoRaHs Website.

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, stressing training and education, and utilizing an interactive Web-site, our aim is to provide the highest quality data for natural resource, education and research applications. We are now in all fifty states.

 

Other data can also be provided if the observer so desires.  The instrument used is a professional grade 4-inch in diameter rain gauge.  The cost for the gauge is about $35.00, which usually must be ordered as only cheaper (and less accurate gauges) are commonly sold in stores.   All volunteer observers in the network should use this type of standard professional gauge for accuracy and consistency of the data.

DSCN7045

My 4-inch plastic rain gauge – the one used in the CoCoRaHS Network.

Below are this morning’s (August 16) CoCoRaHS rainfall readings for Douglas County in the 24 hours ending about 7 AM, reflecting the thundershower that moved through the area between 6 and 7 AM.   An approximate time of 7 AM is encouraged for the daily rainfall measurement.  This also allows the observer’s measurements to make the maps in order to easily compare with other observers.

 

GetMap

Douglas County 24 hour CoCoRaHS precipitations amounts as of about 7 AM on August 16, 2017.  Similar maps are available on their website for every US state and county.  However, not all counties have CoCoRaHS volunteer observers, so some counties will have no data.

Notice the typically highly variable amounts from the showers that moved northeastward across the Lawrence area early this morning.  A narrow swath in the city received over 6 tenths of an inch, a swath which extends to the southwest and northeast of the city as well, while three observers in the north-central portion of town measured just under 2 tenths of an inch.  The ‘official’ climate station out at the Lawrence Airport came in with 0.20 inches, which agrees closely with the three observers in the north-central part of Lawrence.

However, which source of rainfall information is more representative and gives a better idea of what actually fell within Lawrence, the official NWS amount measured out at the airport, or the CoCoRaHS Network?   Why, of course, the seven-station CoCoRaHS network within Lawrence is far more representative of what actually fell across the city, as the network readings offer both a range and location of of the values and a better overall average. The average of all seven of the CoCoRaHS readings within the city is 0.39 inches, nearly double the amount measured by the official site out at the airport.

The National Weather Service (NWS) utilizes the automated aviation weather observing equipment at the Lawrence Airport as the ‘official climate site’ and disseminates that amount as the ‘Lawrence 24-hour rainfall.’  This is then picked up and disseminated by the various media.

This then begs the following question:  What happens when there is a malfunction with the automated equipment at the airport and, as a result, no rainfall measurement can be obtained?  While I have already alluded to this question in the first caption of my previous post, ‘Encore Storm Recap,’ I will discuss this issue further in my next post!

 

 

 

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