[wxqc] C4443 Dew Point errors

zmwp01 at valornet.com zmwp01 at valornet.com
Fri Jan 6 10:57:13 EST 2006 

Good morning Dave,
It seems another station(may be the same one as below) is causing
a large shift in the analysis data for my station again. When comparing
my DP to the two airports and others near me I am very close but the
analysis data is showing 4-6 degF below all others. I would really like
for this to be cleared up so the QC graphs have merit again.
In the meantime I have been using two airports and five nearby
stations for my reference.
Thank you,
Martin

> Hummm... I had not seen that station before when I looked at your nearby
> station.  Lets see what can be done to get that bugger fixed or gone so
> it isn't messing up the analysis.
>
> Dave
> CW0351
>
>  From MADIS:  TLSA2 (AWS) Holland Hall School Tulsa, OK
> time    slp         t / td          dir / spd / gst/pcp   presWx &
> skyCover
> (UTC)  (mb)          (F)                    (mph)  (in.)
> 1329 1020.7(S) 29.0(S)/-33.3(S) 120°(C)/002(S)/---/0.00"
> 1314 1021.0(V) 29.0(V)/-33.3(Q)  96°(V)/001(V)/---/0.00"
> 1259 1020.7(V) 28.0(V)/-34.0(Q) 110°(V)/002(V)/---/0.00"
> 1244 1020.7(V) 28.0(V)/-34.0(Q) 100°(V)/002(V)/---/0.00"
> 1224 1020.7(V) 28.0(V)/-34.0(Q) 110°(V)/001(V)/---/0.00"
>
> zmwp01 at valornet.com wrote:
>
>>Good morning Dave,
>>
>>There is a station TLSA2 (Holland Hall School Tulsa,OK) that has
>>been steadily reporting a dew point value -40 to -50 degF below
>>the neighboring stations. This station is only a few miles from mine
>>and may the cause of the offset in my ANALYSIS data.
>>I discovered that the ANALYSIS data from other stations not so close
>>to TLSA2 fell right in line with my DP data.  A comparison of the other
>>five closest stations falls in line with my data also.
>>Hope this is of some help to you.
>>
>>Best regards,
>>Martin
>>
>>
>>
>>>Hi Martin,
>>>
>>>When in doubt, use the nearby ASOS stations as your source for truth as
>>>personal weather station data my not be accurate.  The +3F dew point
>>>bias exists for your station because most of your closest 5 neighbors
>>>have average dew points as least 3 F less than your average dew point
>>>most of the time... at least that was the case in your station's
>>>longer-term analysis statistics, but more recently your data is more in
>>>line with the other stations.
>>>
>>>Much of the time, the QCMS analysis for individual CWOP stations is
>>>comprised of mix of CWOP and non-CWOP stations.  AWS/WxBug folks have
>>>recently been allowing their data to be views on the MADIS Mesomap, but
>>>that is not always the case.  But even if AWS/WxBug observations are not
>>>plotting on the MADIS Mesomap, they are likely used in the determination
>>>of the station analysis (that is, if there are near-by AWS/WxBug
>>>stations which is generally the case in the more populated areas).  My
>>>point is that it is not always obvious which stations are influencing
>>>the your station's analysis.  When we have questions about the analysis
>>>input, we generally ask MikeB to that a look at what is going on.
>>>
>>>If you are still interested on the details of the MADIS QCMS analysis
>>>technique, please check out this page especially the spatial
>>>consistency/OI technique section:
>>>http://www-sdd.fsl.noaa.gov/MSAS/qcms_descrip.html
>>>
>>>
>>>Regards,
>>>
>>>Dave
>>>CW0351
>>>
>>>
>>>
>>>zmwp01 at valornet.com wrote:
>>>
>>>
>>>
>>>>Good morning Dave,
>>>>
>>>>I definitely appreciate your time to help me understand the
>>>>interpretation
>>>>of this collected weather data. This has turned out to be
>>>>a fascinating venture for me. I would have never guess such a network
>>>> was
>>>>in place for coordinating and compiling so many weather stations.
>>>>My hat is off to you, Russ, Philip, and all your team members.
>>>>I guess what has me puzzled about the +3F error in my humidity is
>>>>that most of the stations in Tulsa County must have the same error or
>>>>greater since they usual have a similar reading or higher as
>>>> illustrated
>>>>in the link you referenced below. The same can be seen on most other
>>>>days.
>>>>I have also been using the NOAA Mesomap for my comparisons.
>>>>I currently have two weather stations, a Davis VP2+ (6163), which is
>>>>online with CWOP and a Davis VP2+ (6162) which is not online
>>>>and being monitored locally. The second station has been moved to
>>>>different locations on my property to see the effects on the data.
>>>>So far both stations have been within +/- 1 of each other on most
>>>>data points when place in the same location.
>>>>Both stations are only a few months old.
>>>>This brings to mind the interest in understanding how the ANALYSIS data
>>>>is
>>>>generated if it is the only true reference in this case.
>>>>Your time and effort to help me understand how all this works is
>>>>much appreciated.
>>>>
>>>>Thanks again,
>>>>Martin
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>>Hi Martin,
>>>>>
>>>>>In comparing to the near-by ASOS stations:
>>>>>http://weather.gladstonefamily.net/qchart/C4443?date=20051129&addnl=KRVS&addnl=KTUL&Add+to+charts=Add+to+charts&.cgifields=addnl
>>>>>... and the MADIS QCMS ANALYSIS, both show an approximate 3F "moist"
>>>>>bias.   While  people have shown  cases where the QCMS ANALYSIS has
>>>>>problems, I believe in this case  it is correct.  Having a 3F moist
>>>>> bias
>>>>>(e.g. the RH and dew point typically are higher than "truth") is just
>>>>>barely out of spec, so you are still providing reasonably good data
>>>>>despite the less than perfect humidity observations.
>>>>>
>>>>>It is the nature of the thin film capacitor technology (which most
>>>>>personal weather stations use to sense humidity) to "drift" out of
>>>>>calibration.  What type of weather station hardware do you operate?
>>>>>
>>>>>Here is a "classic" thread on diagnosing and resolving humidity
>>>>>measurement issues which you may wish to peruse:
>>>>>http://pond1.gladstonefamily.net:8080/pipermail/wxqc/2005-July/subject.html
>>>>>http://pond1.gladstonefamily.net:8080/pipermail/wxqc/2005-July/000334.html
>>>>>http://pond1.gladstonefamily.net:8080/pipermail/wxqc/2005-July/000336.html
>>>>>http://pond1.gladstonefamily.net:8080/pipermail/wxqc/2005-July/000338.html
>>>>>http://pond1.gladstonefamily.net:8080/pipermail/wxqc/2005-July/000345.html
>>>>>
>>>>>
>>>>>Regards,
>>>>>
>>>>>Dave
>>>>>CW0351
>>>>>
>>>>>
>>>>>
>>>>>Sam Drinkard wrote:
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>>zmwp01 at valornet.com wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>Here are a few links that reference my station CW4443(C4443)
>>>>>>>http://pond1.gladstonefamily.net:8080/cgi-bin/wxqchart.pl?site=C4443
>>>>>>>http://www.findu.com/cgi-bin/wxpage.cgi?CW4443
>>>>>>>http://www.met.utah.edu/cgi-bin/droman/meso_base.cgi?stn=C4443
>>>>>>>I should have been more specific, sorry.
>>>>>>>
>>>>>>>Martin
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>I looked at the graphs, and see first off there is a bad case of the
>>>>>>"jaggies" in there.  Comparing almost all the stations did not reveal
>>>>>>anyone with really flakey looking lines, but then again, it's hard to
>>>>>>see so many at one time and my eyes aren't that good :-(  From what I
>>>>>>saw of strictly your data, I don't see anything to indicate a big
>>>>>>problem.  I've certainly seen worse on DP from my own station too.  I
>>>>>>always seem to run a tad too warm on DP, and sometimes too cool with
>>>>>>temps, but I refuse to try to "fix" the temp problem, as it's still
>>>>>>within limits.  I believe from looking at yours Martin, you are in
>>>>>> the
>>>>>>same category I am w/r/t the error(s).  The graph for 11/11 does show
>>>>>>the 5º plus diffs, but is that a spurious reading or anomoly or is
>>>>>>that what it looks like more times than not?
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
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>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
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>>>>
>>>>
>>>>
>>>>
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>>
>>
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