[wxqc] Fw: RE: Davis Comments on Rainfall Measurements

Sun Jan 1 16:34:14 EST 2006

Dave
Thanks. you answered my question. when I said "MF" I was referring to "RFI"
or "EMF" electrical interference. I was having a problem with the gauge
incrementing ever few days. but after I installed two 1000Pf Capacitors
across the sensor leads it took care of the problem. it was a known problem
at Peet Bros, and there Tec support told me how to fix it.

I hope you and your's have a great and prosperous New Year.
Jim

-----Original Message-----
From: wxqc-bounces at lists.gladstonefamily.net
[mailto:wxqc-bounces at lists.gladstonefamily.net]On Behalf Of Dave Helms
Sent: Sunday, January 01, 2006 9:57 AM
To: Discussion of weather data quality issues
Subject: Re: [wxqc] Fw: RE: Davis Comments on Rainfall Measurements

Hi Jim,

It doesn't matter what the rain droplet size is for the Peet Pro gauge,
since the Pro's funnel orifice actually forms the droplet that is
counted by the internal electrode shorting.

I think when you write "mf", you are referring to "morning fog" or dew,
right?  False precip from dew can be a problem for all automated and
even manual precip gauges.  Some data logging applications will not
remove spurrious 0.01 precip totals, if configured to do so.  I am
always correcting my station precip totals from my Peet Pro gauge using
Weather Display application after comparing its totals with my manual
gauge.  I encourage you to not ignore spurrious precip totals, but try
and correct them after the fact in your station climate record if the
reports are obviously incorrect.  In real-time reports to CWOP and NOAA,
erroreous precip from automated stations are QC'd and processed
aaccordingly so I would not be too concerned about the occassional dew
induced precip report as these are not operationally significant.

Cheers,

Dave
CW0351

jim wrote:

>Dave
>My Gauge is also a Peet Pro rain gauge. I was more concerned on over
>counting because Ill get a couple drops this week then a couple next week
>etc then all of a sudden the gauge increments .01 and no rain in sight. or
>should I even worry about it. The only problem I had with the gauge is I
had
>to put a couple of capacitors in the sensor leads to dissipate mf.
>Jim
>
>-----Original Message-----
>From: wxqc-bounces at lists.gladstonefamily.net
>[mailto:wxqc-bounces at lists.gladstonefamily.net]On Behalf Of Dave Helms
>Sent: Saturday, December 31, 2005 2:52 PM
>To: Discussion of weather data quality issues
>Subject: Re: [wxqc] Fw: RE: Davis Comments on Rainfall Measurements
>
>
>Hi Jim,
>
>I have a Peet Pro rain gauge that "counts" drops by running the rain
>through a funnel which makes a standard sized droplet.  These "standard"
>droplets then "shorting" the drops across electrodes, which I think you
>are describing.  My "shorting" gauge has no moving parts, and
>performance reasonably well in my relatively wet location (52+ inches of
>precip this year).
>
>When it rains, the humidity goes up very quickly so I wouldn't think
>evaporation accounts for any significant precip under-reporting (of
>course evaporation does happen in the desert, called virga, but if rain
>never hits the ground then it is not recorded as rainfall).  Anyway,
>this under-reporting from evaporation (however small) should be equal
>for all automated gauges.  A manual gauge or weighing gauge could
>evaporate some  rainfall if you wait too long to retrieve the precip
>measurement.  Weighing gauges reduce evaporation by putting a small
>amount of light oil in the gauge which stops evaporation of precip as it
>"floats" ontop of new rain (or the rain "sinks" under the oil).
>
>Dave
>CW0351
>
>jim wrote:
>
>
>
>>Dave
>>While it seems a lot of people are on the subject of rain gauges. what are
>>some of the thoughts on Electronic non tipping bucket type. rain gauges. I
>>guess the gauge counts a "standard size drop" and after so many drops it
>>increments .01 the only adjustment is at the console. I have one and I
>>thought it would be good here in the desert as drops are few and far
>>between, and a drop can evaporate before it is measured in a tipping
bucket
>>type.
>>Jim
>>CW4367
>>-----Original Message-----
>>From: wxqc-bounces at lists.gladstonefamily.net
>>[mailto:wxqc-bounces at lists.gladstonefamily.net]On Behalf Of Dave Helms
>>Sent: Friday, December 30, 2005 11:53 PM
>>To: Discussion of weather data quality issues
>>Subject: Re: [wxqc] Fw: RE: Davis Comments on Rainfall Measurements
>>
>>
>>Hi Leroy,
>>
>>It is true with "convective" type rain, characterized by rainshowers and
>>thunderstorms, is highly variable in time and space.  During that
>>winter, rain is typically "stratified" especially ahead of warm front
>>where rainfall is nearly uniform over larger areas.  Large elevation
>>differences will also cause rainfall to be quite variable over short
>>distances (e.g. windward maximum and leeward rain shadow).   All these
>>differences in the distribution of rain make it as yet a challenge for
>>NOAA to do automated QC on precip reports.  MADIS does not yet do
>>rainfall QC, and at the River Forecast Centers, humans sift through the
>>precip reports to generate composite rainfall estimates.  Given that
>>professionals struggle with determining aerial precip measurement
>>accuracy, the best way for hobbyists to monitor automated precip gauge
>>performance is to cut the distance uncertainty error to zero by having a
>>co-located manual gauge.
>>
>>Here is my custom sensor array solution to automated and manual rain
>>gauge co-location:
>>http://www.flickr.com/photos/76833808@N00/57509378/
>>
>>I have contacted a company that will sell the 4" manual rain gauge for
>>$20.25 (part # RG100), plus shipping.  This is a much reduced "group
>>rate" for CWOP, just tell them you are with "Citizen Weather" (CWOP is
>>not getting a commission here, just helping to save members $$$).  The
>>company, Construction Safety Products, Inc., can be reached via the
>>phone at 1-800-592-6940, ask for the Forestry Dept., or order online at
>>www.cspoutdoors.com
>>
>>Dave
>>CW0351
>>
>>LeRoy Lambert wrote:
>>
>>
>>
>>
>>
>>>*/Here is what I got from Davis on the accuracy of my rain gauge/*
>>>*//*
>>>*/LeRoy/*
>>>*//*
>>>
>>>----- Original Message -----
>>>*From:* Randy MacAulay <mailto:randym at davisnet.com>
>>>*To:* LeRoy Lambert <mailto:leroydl at verizon.net>
>>>*Sent:* Friday, December 30, 2005 1:42 PM
>>>*Subject:* RE:
>>>
>>>LeRoy,
>>>As long as the rain collector is level and the tipping buckets are
>>>clean and tipping freely, then the rain collector should be very
>>>accurate.It can be calibrated by adjusting the height of the posts
>>>that the buckets rest on. I always caution people when comparing
>>>readings to different types of collectors in different locations. If
>>>you doubt the accuracy of your rain collector, you can send it in for
>>>evaluation. We can even have it NIST certified.
>>>
>>>
>>>Randy MacAulay
>>>Davis Instruments
>>>Technical Support
>>>randym at davisnet.com
>>>Phone: (510) 732-7814
>>>FAX: (510) 670-0589
>>>
>>>
>>>
>>>   ----------------------------------------------------------------------
>>>
>>>
>>>
>>>
>>--
>>
>>
>>
>>
>>>   *From:* LeRoy Lambert [mailto:leroydl at verizon.net]
>>>   *Sent:* Friday, December 30, 2005 7:45 AM
>>>   *To:* Support
>>>   *Subject:*
>>>
>>>   */I'm seeing reports from people at COP finding your rain gauge
>>>   reading as much as 30%  off.  Is there a way to check the
>>>   accuratisy or calibrate the tipping bucket gauge?/*
>>>   *//*
>>>   */LeRoy/*
>>>
>>>------------------------------------------------------------------------
>>>
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>>>
>>>
>>>
>>>
>>>
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>>
>
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