Weather Related Organizations > CoCoRaHS

Cocorahs: recommended changes

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dcriner:
They want precipitation reported 7am - 7am. I don't necessarily arise that early, and want to walk out to my gauge, so I often go by my Davis weather station, as electronically recorded on weatherundergound.  (My Davis station tracks very closely with my manual Cocorahs rain gauge.)

Cocorahs should allow automatic hourly electronic data updates, and break it down however they want.

DW7240:
Hi,

I agree with you dcriner, my only concern with your suggestion is that COCORAHS don't recognise any form of electronic readings, they only want readings from their own specified gauges, namely their own 4" plastic funnel and tube.

What they should do is find a suitable electronic (tipping bucket) gauge, but clearly more accurate then the Davis models (as we have read on this forum, the comparisons in readings from the two types can be wide and varied)  I personally have found these differences from using both types of gauges.  My manual readings are taken at 8:00 a.m. and compared with the Davis.  Looking at their website, and seeing the meso style map they have on their site, you will see the variations in times of readings from other users, anything from 6:00 - 10:00 a.m.  Their suggestion of 7:00 a.m. I think is the next best time from average day break (6:00 a.m.) At the end of the day, they are happy with the readings from anytime near the 7:00 a.m. criterior.

So my point to this is - electronic gauge with same specs as the manual version, and clearly at a price which is affordable to us users without compromising quality and accuracy.  Not sure if that's all achievable - hence why they don't offer anything yet to fill the gap.

Anybody else want to chip in on this, I'm sure others would benefit from ideas and views on this, after all, most of our weather stations are completely electronic, accurate, and serve a purpose, a  manual rain gauge is like going backwards - ok it maybe more accurate - but I feel it shouldn't be, if so, I'm going back to reading a wet/dry bulb thermometer and logging everything in a text book - this is how I started, no computer, nothing electronic, just simple graphs with a bit of maths thrown in for good measure.

Nick. dw7240.com.

miraculon:

--- Quote from: dcriner on May 09, 2017, 08:37:25 PM ---They want precipitation reported 7am - 7am. I don't necessarily arise that early, and want to walk out to my gauge, so I often go by my Davis weather station, as electronically recorded on weatherundergound.  (My Davis station tracks very closely with my manual Cocorahs rain gauge.)

Cocorahs should allow automatic hourly electronic data updates, and break it down however they want.

--- End quote ---

I make my observation at 8AM. They may "want" the observation at 7AM, but there is some flexibility.

On using TBR for CoCoRaHS, this would simply not work for snow conditions. The heaters in the TBR melt/evaporate a significant amount and it becomes lost from the readings.

See this: https://cocorahs.org/Content.aspx?page=faqgeneral#7am

Which shows:


--- Quote ---Do I have to check my rain gauge at 7am? No, but we would prefer it if you did. If you check your gauge at other times, your data may not be directly comparable to other data. If you check your gauge at night, your data will be in our reports but won't show up on our maps. We only map data that is collected within two hours of 7am.
--- End quote ---

My 8AM data shows in both the "New" map and the "Classic" just fine with my 8:00 AM ob. I even set the normal observation time to 8AM.

Greg H.

ValentineWeather:
They would prefer 6AM when NWS observations ends but realizing many won't make the time they compromised on 7AM.

My tipping bucket is normally very close with rain but not by accident, I spend hours calibrating several times yearly. I shoot for rain rate of 6" per hour for my area using professional calibrator and usually within .01 of 8" SRG. 

Snow won't work at all the average evaporation is around 30%.

floodcaster:
7am is the "ideal" time but generally 6 to 8 am is ok. Being consistent regarding reporting time of  your daily report is important. CoCoRaHS uses the same type of manual gauge for a couple of reasons...accuracy and consistency. With all observers using the same gauge we are comparing "apples to apples".   -Bill

From the CoCoRaHS web site:

--- Quote ---Why does CoCoRaHS not use automated rain gauges?

We are often asked why CoCoRaHS does not encourage the use of automatic rain gauges to report 24 hour precipitation totals.  After all, many weather enthusiasts already have electronic home weather stations with automatic rain gauges to record precipitation  -  why should they also purchase a separate CoCoRaHS gauge?
Unfortunately, it turns out that 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 like you test their automated gauges against either the CoCoRaHS 4" diameter gauge or the National Weather Service (NWS) 8" diameter Standard Rain Gauge.  We have also tested National Weather Service 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 (our tests indicate that 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 our project because we are interested in observing and understanding natural precipitation variability, as accurately as possible.  If we're all using different kinds of gauges with different abilities to catch precipitation, it's too hard to determine if differences in rain or snowfall are "real" or due to the kind of instrument that was used to report the measurement.

Because of these test results, we have asked our observers to please set up a CoCoRaHS 4" gauge along with their automated gauge and see for themselves.  Many observers have converted to using the 4" gauge as their daily measurement when they see the results, and then use their automated gauge as a backup when they are gone.  It is very good to use the two in combination.  But whenever people do use their automated gauge as their measurement, we request that they mention that in the daily "observation notes".

For those of you who decide it's too much trouble to purchase a CoCoRaHS gauge in addition to your automatic system, you may still be able to share your data with the National Oceanic and Atmospheric Administration (NOAA - the organization that oversees the NWS) via their Citizen Weather Observation Program (CWOP).  This program makes home weather station data available to the NWS for certain real time applications. WeatherUnderground is another system for web-based data sharing. 

For climate data and research applications, as well as supporting the "NowCasting" goals of NOAA, we encourage you to use the 4" diameter high capacity manual rain gauge and join CoCoRaHS.
--- End quote ---

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