[wxqc] Barometric Pressure Errors

[Dave Helms]

FYI.. Dry adiabatic lapse rate is 5.5 F degrees per 1,000 feet (10 C 
degrees per 1,000 meters); cooling going up, warming going down:
http://daphne.palomar.edu/jthorngren/adiabatic_processes.htm
... the atmosphere will be dry adiabatic so long at the air in not 
saturated (then use the moist adiabatic lapse rate).  Down in the 
valley, there will be less mixing/wind during the day, so maybe locally 
higher temps.  Exception:  We know that in California, the folks about 
3,000 ft or so can be much warmer than lower elevations due to the 
influence of the  warm high subsidence inversion which can significantly 
warm temperature as you gain elevation.  Then there are 
katabatic/drainage winds...  The rule I follow is all rules are made to 
be broken.

Dave
CW0351

Tisha Hayes wrote:

> Hi,
> Thanks for your feedback on my thread. Yes, I found that the elevation 
> setting in the Davis Vantage Pro2 was incorrect. Once I corrected the 
> elevation I was able to pull the accuracy to within 1 milliBar of the 
> closest "official" barometric pressure at the Gadsden Regional Airport.
>
> I too have the same issues with the local airport elevation since it 
> is at 530 feet AMSL and my ground elevation is 890 feet with the 
> barometer mounted at 915 AMSL.
>
> Topographically I believe that my readings will differ from the 
> nearest airport as I am on the crest of a mountain (Lookout Mountain) 
> and the airport is down in the valley to the south (situated on the 
> Gadsden Mushwad Complex (geological)). Winds coming out of the west 
> and southwest will need to lift as they approach the mountain and my 
> local conditions vary significantly from 850' on Lay Springs Road to 
> 1250' at the crest and down to 590' at Owls Hollow Road. Eventually I 
> want to situate several stations across my property (3/4 miles wide 
> East-West, 1/2 mile North-South). It is noticably cooler up here than 
> down in town and my thermometer in my car can show up to a 10 degree 
> difference in the four mile drive.
>
> Thanks Again!
>
> Tisha Hayes
> Sr. Engineer
>
> On 7/17/06, *Thomas E. Salzer* <tom.es at verizon.net 
> <mailto:tom.es at verizon.net>> wrote:
>
>     Hello,
>     I stumbled across your barometer calibration thread while doing a
>     search on
>     barometry. I was wondering whether the problem was resolved, and
>     what you
>     concluded. I had no idea it was that complicated. However, it
>     seems to me
>     that everyone agrees on sea level pressure. The difference is how
>     one makes
>     corrections for altitude. If one simply uses elevation, they will
>     get a
>     different result than if dew point and temperature are included. I
>     set my
>     barometers to local airport postings, but the local airport is
>     only 233 feet
>     above sea level, so a small calibration error might not be apparent.
>     I hope to hear about your resolution of this matter.
>     Best regards,
>     Tom Salzer
>
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>
> -- 
> 've seen things you people wouldn't believe. Attack ships on fire off 
> the shoulder of Orion. I watched C-beams glitter in the dark near the 
> Tannhauser gate.
>
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