[wxqc] Dew Point Error for CW6532 Tucson

Tue Oct 10 17:22:14 CDT 2006

The location the entire unit is in now probably gives good 
temperature readings, because it's over grass and in a somewhat 
clearing with trees all around, so it takes relatively little direct 
sun. The problem with the location is that the same things that 
shield it from a lot of direct sun (the trees) also puts it in a bit 
of a rain shadow.

I'm pretty committed to moving the anemometer to the roof. I can 
easily move that without moving the temp / rain unit by adding the 
extra wireless transmitter (that's what I did at my own home 
already). It's just a question of whether or not there is any point 
to moving the rest of the unit.

//John

At 07:32 AM 10/10/2006, you wrote:
>John,
>
>I faced the same exposure problem as you. In my opinion it's more 
>important to provide to MADIS accurate temperature/dewpoint data, 
>etc. than wind data. You should buy the fan aspirated temperature 
>shield kit if you can, it's only $84.00 at Provantage.
>
>The stock temperature shield that comes with the #6152 Vantage Pro2 
>is very inaccurate (up to +6 deg. F) at times, especially during 
>high sun angle times when there is little wind.
>
>By the way the wireless wind vane/anemometer option is $106. I had 
>to buy both to get accurate readings on my oak tree laden property.
>
>Take Care,
>Thomas F. Giella, KN4LF
>Retired Meteorologist & Space Plasma Physicist
>Lakeland, FL, USA
><mailto:flycylone at tampabay.rr.com>flycylone at tampabay.rr.com
>
>NWS Tampa Bay, FL SKYWARN Observer #POL-10A
>CWOP Station #AR692/KN4LF
>
>Live Lakeland, FL Weather Observations: 
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>Lakeland, FL Daily Climatological Weather Data Archive: 
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>September 2006 Lakeland, FL Daily Climatological Weather 
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>
>----- Original Message -----
>From: <mailto:jjames at jameshillfarm.com>John James
>To: <mailto:wxqc at lists.gladstonefamily.net>Discussion of weather 
>data quality issues
>Sent: Tuesday, October 10, 2006 2:18 AM
>Subject: Re: [wxqc] Dew Point Error for CW6532 Tucson
>
>...days passed......
>
>Okay, I read the document, and another that was mentioned yesterday.
>Both are somewhat helpful, but neither really does any weighting. In
>the CWOP document, I can play with the location of my temp / rain
>sensor and just about get an equal score regardless of which option I
>choose. The Vantage Pro 2 is not a unimount system:  I can separately
>mount the anemometer up on the roof by itself. If I do that, however,
>I still leave my temp / rain sensor in the shadow of some trees -
>probably fine for temp, but definitely shorting me when it comes to
>most rain situations. I can move the sensor to the roof and probably
>get a great rain figure, but then have to deal with the roof
>affecting the temp readings.
>
>So, here's my practical question: currently, most of my readings are
>wrong, and to make any fix I either need to buy the property next
>door (very pricey!), or I need to buy some weather hardware. I could
>buy another wireless transmitter and move the anemometer to the roof
>by itself. I could buy a fan / power unit and make my temp with
>radiation and UV shielding and make it fan aspirated. Which would be
>preferrable?
>
>//John
>
>
>At 04:51 AM 10/4/2006, you wrote:
> >John,
> >
> >Yep, that is the problem with a unimount system.  Precip and temperature
> >are probably the most valuable for climate and hydrologic
> >considerations.  Wind and temperatures are more important for weather
> >prediction (modelers need "good" surface winds, e.g. not buried in the
> >canopy).   We recommend that people put their temperature and rain gauge
> >near 2 meters/5 feet and the anemometer at 10 meters/33 feet or above
> >the canopy, obviously; this implied separating the sensor package.
> >
> >For folks who must compromise (almost everyone does), we have a table in
> >the CWOP Guide that considers typical siting option limitations that
> >home owners encounter:
> >http://mywebpages.comcast.net/dshelms/CWOP_Guide.pdf
> >
> >
> >Dave
> >CW0351
> >
> >John James wrote:
> >
> > > At 08:13 PM 10/3/2006, you wrote:
> > >
> > >>
> > >> The first thing that catches my eye is that you have the temp/dpt
> > >> attached to a 6 ft. sensor from your rooftop (not familiar with the
> > >> term parapet, so maybe I'm wrong). While this is fine for the
> > >> anemometer and even the rain gauge, the temperature/dpt sensors
> > >> should be located at 2m off the ground (5-6 feet). Very sharp
> > >> inversions can set up at night, on the order of 5-10F within 30-40
> > >> feet of the surface, especially where terrain and standing water
> > >> bodies are an issue. Likely you're sampling a "different airmass"
> > >> above your roofline than you would be closer to ground level.
> > >>
> > >> Evan
> > >>
> > >>
> > >
> > >
> > > This brings up something I've been wrestling with a bit. I have a
> > > station up at my cabin that has been giving incorrect readings. I have
> > > a two story house and a somewhat wooded area in both front and back of
> > > my house. I don't have a very good clearing for wind, and was going to
> > > move the anemometer to the roof, but I don't think I'm getting good
> > > rainfall readings either due to the trees. I was thinking of moving
> > > the entire station to the roof, but knew that would alter the other
> > > readings. The unit is a Vantage Pro 2 Plus. I get the feeling I'm
> > > wrestling with which measurement I want to be more incorrect.
> > >
> > > //John
> > >
> > >
> > >
> > 
> ------------------------------------------------------------------------------
> > > John W. James
> > > CW4661, CW4663
> > > Web:  < <http://www.jameshillfarm.com/>http://www.jameshillfarm.com/>
> > >
> > > Current weather conditions:  <IMG
> > > 
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> > >
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>
>---------------------------------------------------------------
>John James
>mail:  <mailto:jjames at jameshillfarm.com>jjames at jameshillfarm.com 
><mailto:jjames at jameshillfarm.com>
>Current
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>
>
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---------------------------------------------------------------
John James
mail:  jjames at jameshillfarm.com  <mailto:jjames at jameshillfarm.com>
Current 
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