[wxqc] Barometer Accuracy and Standard Deviation of ASOS Stations?

[dshelms at comcast.net]

Hi Geoffrey,

The FMH-1 is the source for ASOS/AWOS observing system, and the sensor performance standards are listed in Appendix C:
http://www.ofcm.gov/fmh-1/pdf/O-APNDXC.pdf

Here is the link to the full FMH-1:
http://www.ofcm.gov/fmh-1/fmh1.htm

The CWOP Guide lists performance standards, largely based in national and international performance standards:
http://mywebpages.comcast.net/dshelms/CWOP_Guide.pdf

Yes, all presure instruments tend to drift.  I believe the ASOS pressure instruments are calibrated against the NIST standard annually.  Local (temperatrue) conditions will influence pressure to a small degree.

Parascientific makes the "traveling standard" barometer used to calibrate the official NWS pressure measurements.  They have a nice technical refernce page worth checking out:
http://www.paroscientific.com/digibaroapp.htm

Dave
CW0351



 -------------- Original message ----------------------
From: wa4ikq at nevets.oau.org (Geoffrey Dick)
> Does anybody on this list know the targeted, or expected accuracy
> for Barometric Pressure of ASOS calibrated stations?  Once calibrated,
> how much standard deviation is tolerated?
> 
> For several months, I have been tracking barometric pressure of 3 
> airports that are within 12 miles of my location.  The stations
> are within a few meters in elevation of one another.
> Using the daily Gladstone summary, I see them wandering slowly,
> over several days, +/-0.8 millibars many times in opposite 
> directions from one another.  Could temperature, weather station
> power supplies, or some other environmental component be a factor? 
> 
> Geoffrey Dick
> WA4IKQ, AS140
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