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<DIV>Hi Larry,</DIV>
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<DIV>We want people to send altimeter pressure values to CWOP (corrected for elevation above sea level, but not virtual temperature). Using altimeter pressure values allow people to directly compare their pressure with near-by ASOS altimeter reports (XX.XXINS) without knowing exactly what your elevation is.</DIV>
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<DIV>I believe the QCMS method of using your neighbor's pressure values can result in some problems as they could have pressure problems too. Thus, I wouldn't get too excited about small QCMS derived pressure (altimeter) has a small bias. I believe you are on the right track by using local ASOS altimeter pressure values to adjust your station's pressure. </DIV>
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<DIV>When making pressure adjustments, compare several pressure readings, with the same observation times, during nearly uniform high pressure and light winds (low pressure gradients). Avoid doing comparisons with area ASOS altimeter pressures values during moderate wind events and near thunderstorms. </DIV>
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<DIV>Hope this helps,</DIV>
<DIV> </DIV>
<DIV>Dave</DIV>
<DIV>CW0351</DIV>
<BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #1010ff 2px solid">-------------- Original message -------------- <BR><BR>> Philip, <BR>> <BR>> I, too, receive QA reports on my WX data. First question is do the reports <BR>> only show reports that are considered in error? If so, it appears all my <BR>> daily reports are erroneous. <BR>> <BR>> In particular, I have been adjusting my baro to coincide with the reports <BR>> from the local airports at: <BR>> http://www.crh.noaa.gov/den/awebshtml/webpres.shtml <BR>> and have been pretty successful in doing so based on the regression analysis <BR>> from MesoWest at: <BR>> http://www.met.utah.edu/cgi-bin/droman/regress_database.cgi?stn=AP190 <BR>> <BR>> A couple of question regarding pressure readings. First, I calibrate my <BR>> barometer to give reading of altimeter pressure as opposed to sea level <BR>> pressure. Is that correct? Second, I think I understand how your QA works <BR>> by comparing my reading with 5 nearby stations. How effective is the QA if <BR>> the stations around me have their stations reporting sea level pressures or <BR>> are generally incorrect? <BR>> <BR>> Please explain the difference, if any, between what I have been using to QA <BR>> my reports, MesoWest, with the QA reports I receive from you. <BR>> <BR>> I want to get it right and right now I'm not sure which to believe as they <BR>> are so different. Reminds me of the old Chinese proverb "A man with one <BR>> watch always knows what time it is. A man with two is never quite sure." <BR>> <BR>> Thanks <BR>> Larry <BR>> K0ANI <BR>> AP190 <BR>> <BR>> "The only reason for time is so that everything doesn't happen at once." <BR>> --Albert Einstein <BR>> <BR>> <BR>> -----Original Message----- <BR>> From: wxqc-bounces@lists.gladstonefamily.net <BR>> [mailto:wxqc-bounces@lists.gladstonefamily.net] On Behalf Of Philip <BR>> Gladstone <BR>> Sent: Saturday, November 27, 2004 9:03 AM <BR>> To: Discussion of data quality issues <BR>> Subject: Re: [wxqc] questions <BR>> <BR>> Stan, <BR>> <BR>> Stan Horzepa wrote: <BR>> <BR>> >Accordingly, my POT TEMP of 36 is 2.4 degrees higher than the computed <BR>> >value, my DEW PNT of 33.6 is 6.9 degrees higher than the computed value, <BR>> and <BR>> >my FF of 10.4 is 3.5 knots higher than the computer value. Is that a <BR>> correct <BR>> >interpretation? <BR>> > <BR>> > <BR>> This is correct. <BR>> <BR>> The error values are calculated for each reading that your station <BR>> reports. If the error exceeds a threshold, then the record is included <BR>> in the email that is sent to you. <BR>> <BR>> The threshold for temperature & dewpoint is 6 F and that is why this <BR>> particular record was sent. <BR>> <BR>> >How big a computed error should one be concerned with? I imagine local <BR>> >conditions play some part in causing a local reading to be out of kilter <BR>> >with the computed value, but when is a local reading so far out of whack <BR>> >with the computed value that it indicates that something is wrong with the <BR>> >weather station equipment. My guess is that if my POT TEMP of 36 is 2.4 <BR>> >degrees higher than the computed value, then that is not something to be <BR>> too <BR>> >concerned about, but if my DEW PNT of 33.6 is 6.9 degrees higher than the <BR>> >computed value, is that something I should check out? <BR>> > <BR>> Personally, I wouldn't bother checking anything unless you get a <BR>> significant number of error readings. Also, a check of the graph may <BR>> show you that there is a consistent bias in your values. This bias may <BR>> be due to local conditions, or it could be a calibration error. <BR>> <BR>> Philip <BR>> <BR>> -- <BR>> Philip Gladstone <BR>> * Check out the live pondcam at http://pond.gladstonefamily.net <BR>> <BR>> <BR>> <BR>> _______________________________________________ <BR>> wxqc mailing list <BR>> wxqc@lists.gladstonefamily.net <BR>> http://pond1.gladstonefamily.net:8080/mailman/listinfo/wxqc </BLOCKQUOTE></body></html>