Author Topic: CoCoRaHS  (Read 2746 times)

Blicj11

  • Storm
  • *****
  • Posts: 3941
    • EW3808
    • KUTHEBER6
    • Timber Lakes Weather
  • Station Details: Davis Vantage Pro2 Plus | WeatherLinkIP Data Logger | iMac (2019), 3.6 GHz Intel Core i9, 40 GB RAM, macOS Ventura 13.6 | Sharx SCNC2900 Webcam | WeatherCat 3.3 | Supportive Wife
CoCoRaHS
« on: October 01, 2014, 11:21:37 PM »
For my fellow CoCoRaHSians out there, I am just curious about the gap between your PWS precipitation readings and your CoCoRaHS gauge readings. Do your manual readings tend to closely follow your PWS or is there a bit of a spread? At my place my CoCoRaHS readings are always lower than my Davis readings. The manual gauge is not located next to my ISS because I can't get to that location during snow season. I'm not obsessing about the difference in readings but am curious about your own observations.
Blick


Steve

  • Global Moderator
  • Storm
  • *****
  • Posts: 1555
    • DW8454
    • KOHAVON11
    • Avon Weather
  • Station Details: Davis Wireless VP2 Plus w/24 hr FARS, Leaf & Soil Station, 2023 Mac mini M2 Pro, 32GB RAM, Mac OS 14, WeatherCat 3.2
Re: CoCoRaHS
« Reply #1 on: October 02, 2014, 12:23:41 AM »
My CoCoRaHS gauge and my ISS are about 8 feet apart. The ISS is about 24" higher than the CoCoRaHS gauge. The correlation between the two varies with rain intensity, direction, windspeed and direction. Usually, the CoCoRaHS gauge reads higher than the ISS gauge. I occasionally adjust the daily setting in WeatherCat if the difference is significant. I generally trust the CoCoRaHS gauge over the ISS gauge.

CLICK HERE if you'd like to see 3+ years of daily comparisons.





I hope that helps,
Steve
Steve - Avon, Ohio, USA


CWOP: DW8454 - WU: KOHAVON11 - AWEKAS - CoCoRaHS
PWSweather - WeatherCloud - Twitter - Facebook

Felix

  • Gale
  • ****
  • Posts: 439
  • Station Details: Davis VP-2 Plus, FARS, WeatherLink IP. Sharx cams.
Re: CoCoRaHS
« Reply #2 on: October 02, 2014, 07:45:32 PM »
...The correlation between the two varies with rain intensity, direction, windspeed and direction. Usually, the CoCoRaHS gauge reads higher than the ISS gauge. I occasionally adjust the daily setting in WeatherCat if the difference is significant. I generally trust the CoCoRaHS gauge over the ISS gauge.

That's been my experience as well....the nearby (30 feet away) CoCoRaHS gauge typically reads higher.

I'd add one more variable to your list which seems to make a difference at my site...the number of rainfall periods during the past 24-hour period.

Sometimes my Davis gauge is right on the button (compared to the CoCoRaHS manual gauge) and other times it's off by two or three hundredths. I've always figured that the rain likely stopped just before the bucket tipped the last time so that accounts for a hundredth. And then if there are multiple rainfall periods during the day with evaporation taking place out of the bucket between showers, that could account for some additional error. Plus, if the wind direction is such that the mounting pole partially shields the Davis collector, I get even more error.

I have a friend in another state with a WeatherHawk 600-series station and he tells me the raindrop-counting solid state sensor correlates nearly 100% with his nearby CoCoRaHS gauge (both gauges well outside the influence of any obstacles).

HantaYo

  • Strong Breeze
  • ***
  • Posts: 193
    • CW3993
    • KCOSALID1
  • Station Details: Davis Vantage Pro Plus via Keyspan Serial/USB adapator running on 10.9.4
Re: CoCoRaHS
« Reply #3 on: October 03, 2014, 02:46:11 AM »
I usually notice a couple of hundredths more from my Davis VP for rain precipitation depending on wind, precipitation intensity and amount.  For snow, it is all over the map- which is why I do a snow board core.   

LesCimes

  • Strong Breeze
  • ***
  • Posts: 223
    • CW9832
    • KGAGRACE1
    • Weather Underground
  • Station Details: Vantage Pro 2 on a MacMini (2009) Mac OS 10.11.6
Re: CoCoRaHS
« Reply #4 on: January 11, 2015, 01:56:02 AM »
Am tardy responding to this thread but will add in my 2? worth. My CoCoRaHS rain gauge is on the same post as my VP2 gauge. The readings are almost always identical. Once in a while one gauge reads .01" more than the other, but not always the same gauge.