[wxqc] Relative Humidity vs. Dewpoint

[Victor Engel]

My QC reports are coming in now. An example is at

http://weather.gladstonefamily.net/qchart/C6155?date=20060714&addnl=CW6155

The first thing I notice is the barometric pressure. I haven't added any
adjustment yet -- that will wait for appropriate weather so I can make a
good comparison to the airport.

What I'm writing about now, though, is the graphs for dew point and relative
humidity. I notice my dewpoint is slightly higher than the analysis. But
that's not unexpected, since my yard has tall grass and a fishpond. However,
relative humidity (on the same webpage) is pretty well right on target. Is
the discrepancy because my temperatures are slightly higher than analysis?
The amount it's off, is actually close to my own expectation. Davis Vantage
Pro documentation for the aspirated unit lists 0.5 degrees error in bright
sunlight. The report lists -0.6 degrees during the day and -0.1 degrees at
night.

I'm also curious about one other thing.The temperature graph seems to show
more of a temporal error, where the graph is slightly out of phase, than an
amplitude or vertical offset error. I'm fairly certain the time on my unit
is correct. Is the CWOP analysis performed on data that is delayed?

Victor
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