[wxqc] Calibrating anemometers
Victor Engel
brillig at gmail.com
Sun Jul 9 11:09:39 EDT 2006
I report to CWOP, but it hasn't been long enough for a quality check yet. My
neighbor does not. Yes, the nearby red oak is big enough to shelter from the
wind. I think I'll take our data and do a statistical analysis on our
differences by wind direction. If it's a shelter anomaly, we each should
have directions that register higher than the other, I would think.
Regarding the plot that you suggest, how would you recommend doing that?
On 7/9/06, Gerry Creager N5JXS <gerry.creager at tamu.edu> wrote:
>
> thanks fo rthe map/aerial photo reference. Makes this a *little* easier.
>
> Victor Engel wrote:
> > Thank you for the reply.
> >
> > Here is a brief description of the siting. If you want, go to
> >
> http://www.wunderground.com/stationmaps/gmap.asp?zip=78757&magic=1&wmo=99999
> > <
> http://www.wunderground.com/stationmaps/gmap.asp?zip=78757&magic=1&wmo=99999
> >
> > and zoom in as far as possible while keeping North Allandale and North
> > Central Austin SKYWARN in the picture. Then click on Satellite to see
> > the buildings, trees, etc. Our stations are the two closest together on
> > the map. In fact, you have to zoom in considerably before the symbols
> > stop overlapping.
> >
> > Mine is the north one, North Allandale. The anemometer is mounted on a
> > pole 12 feet above my two storey house. The house is 28 feet tall. It's
> > mounted on the northernmost peak of the second storey, just northwest of
> > a large red oak (casting its shadow on the street). My neighbor's unit
> > is mounted on a taller pole over a single storey house two doors south
> > of my house. It's actually one house north of where the symbol
> > indicates. His house is surrounded by trees, but they are short trees
> > (I'm not sure whether they taller than the pole or not). Both our units
> > are at 40 feet. My pole extends farther if I want it to, but I wanted
> > the same height for now (from the ground -- I think the ground is
> > slightly higher at my house).
>
> The overhead imagery suggests the red oak you identified near your
> instrument is taller and provides a significant section of blockage in
> azimuth. The predominant wind in central Texas (I'm in College Station)
> is generally from the southeast. Your tree is potentially shielding you
> and giving you lower readings. It'd be hard for me to be certain
> without visiting and doing a site survey. You might want to draw a plot
> of obstructions to your anemometer and see if that's the only problem.
>
> > My equipment is brand new, having been installed less than a month. In
> > fact, tomorrow I am reinstalling the anemometer pole, because it's
> > slightly tilted (perhaps by 3 degrees or so). We also both have Davis
> > Vantage Pros, but his is wired, and mine is wireless. And he's running
> > different software than I am. I don't know how much difference the
> > software would make.
>
> One would hope it's not a software glitch. May be, however. I just
> can't say.
>
> > I believe my neighbor's equipment is several years old. It was installed
> > when I moved into the neighborhood over 3 years ago, and I think it was
> > up for some time before that.
>
> Off the top, then, I'd expect yours to register more sensitivity than
> his...
>
> > You may also notice temperature differences that are significant during
> > the day. I have a fan aspirated shelter. I don't think my neighbor does,
> > and he has told me that his temperatures are too high due to a
> > restriction in siting caused by a limitation imposed by cable length.
>
> If both of you are reporting to CWOP I can check these easily.
>
> > Anyway, I don't intend to make any adjustments any time soon. But his
> > will frequently register a breeze when mine doesn't register anything.
> > That makes me wonder if something is adjusted too tight or if I screwed
> > up attaching the cups somehow. I don't see what I could have screwed up,
> > though. Is there a period of time before lubrication gets broken in? I
> > wouldn't expect so.
>
> Lubricants tend to wear "out" and not "in". I don't know if your
> construction practices might have caused a problem, but if you're gonna
> have the instrument down, anyway, to reinstall its pole, you might want
> to conduct a brief inspection to see if there are any obvious anomalies.
>
> gerry
>
> > On 7/8/06, *Gerry Creager N5JXS* <gerry.creager at tamu.edu
> > <mailto:gerry.creager at tamu.edu>> wrote:
> >
> > Having followed a bit of this (I've been missing in action on
> vacation)
> > the obvious question arises: What are the similarities and
> differences
> > in instrument siting? Are you measuring at the same heights above
> > ground? Is your anemometer shielded by buildings or trees preventing
> it
> > from seeing higher readings (I know my station suffers from this).
> > Calibrating (or making ad hoc changes to cal'd instruments) is a
> step
> > one shouldn't undertake lightly. Dr. Lee's comment about sending it
> > back to Davis makes the most sense if you're worried about cal.
> >
> > You also fail to mention the age of the instrument and whether
> casual
> > inspection suggests the device may have suffered normal wear that
> could
> > cause performance degradation.
> >
> > Gerry
> >
> > Victor Engel wrote:
> > > What techniques do people use to calibrate anemometers? My
> > neighbor and
> > > I each have a Davis Vantage Pro anemometer, and his readings are
> > usually
> > > higher than mine. Wind gusts, especially, are stronger on his. My
> > wind
> > > direction sensor, however, seems to be more sensitive than his.
> > >
> > > Victor
> > >
> > >
> > >
> >
> ------------------------------------------------------------------------
> > >
> > > _______________________________________________
> > > wxqc mailing list
> > > wxqc at lists.gladstonefamily.net
> > <mailto:wxqc at lists.gladstonefamily.net>
> > > http://pond1.gladstonefamily.net:8080/mailman/listinfo/wxqc
> > <http://pond1.gladstonefamily.net:8080/mailman/listinfo/wxqc>
> > >
> > > The contents of this message are the responsibility of the
> author.
> >
> > --
> > Gerry Creager -- gerry.creager at tamu.edu <mailto:
> gerry.creager at tamu.edu>
> > Texas Mesonet -- AATLT, Texas A&M University
> > Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.862.3983
> > Office: 1700 Research Parkway Ste 160, TAMU, College Station, TX
> 77843
> > _______________________________________________
> > wxqc mailing list
> > wxqc at lists.gladstonefamily.net <mailto:
> wxqc at lists.gladstonefamily.net>
> > http://pond1.gladstonefamily.net:8080/mailman/listinfo/wxqc
> >
> > The contents of this message are the responsibility of the author.
> >
> >
> >
> > ------------------------------------------------------------------------
> >
> > _______________________________________________
> > wxqc mailing list
> > wxqc at lists.gladstonefamily.net
> > http://pond1.gladstonefamily.net:8080/mailman/listinfo/wxqc
> >
> > The contents of this message are the responsibility of the author.
>
> --
> Gerry Creager -- gerry.creager at tamu.edu
> Texas Mesonet -- AATLT, Texas A&M University
> Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.862.3983
> Office: 1700 Research Parkway Ste 160, TAMU, College Station, TX 77843
> _______________________________________________
> wxqc mailing list
> wxqc at lists.gladstonefamily.net
> http://pond1.gladstonefamily.net:8080/mailman/listinfo/wxqc
>
> The contents of this message are the responsibility of the author.
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://pond1.gladstonefamily.net:8080/pipermail/wxqc/attachments/20060709/0daf3a6e/attachment.html
More information about the wxqc
mailing list