[The following are excerpts of an email conversation between myself and Rex Hervey of NDBC. When CHAMP first started feeding data from this station to NDBC, some questions were raised about the accuracy of its barometric pressure readings. It so happened we had some similar questions about the WXT barometric pressures at
LCIY2 at the same time. In due course of time we determined that the pressure readings were all correct within instrument tolerances, and later (March 2010) we would add a redundant analog barometer to PVGF1 just to be sure. Still, the model analyses shared by Rex are interesting enough to include on this blog.]
On June 25th, 2009, Rex wrote:
We are releasing the data from Port Everglades with the exception of pressure. It looks like it is about one mb low. We will continue to watch it. If you can apply an offset, I can give you one after we have more time to look at it. Picture is not up yet, but here is the web page: http://www.ndbc.noaa.gov/station_page.php?station=PVGF1
My reply on July 5th, 2009 was:
Can you tell me more about how you know the station's air pressure is off? I assume you're comparing it with reports from surrounding stations but I'd like to know which ones. The WXT520 weather transmitter is newly-calibrated and I'm not aware that we've had any problems with them in the past.
I could also put a standalone barometer out there for comparison purposes, although that will have to wait until we can coordinate another visit.
Rex followed up on July 6th, 2009 with:
It is compared to surrounding stations and numerical model analyses. Now that we have had a week or so to look at it, the bias is only about .3 to .4 mb low compared to model analyses. That is within limits, so we will release it.
On August 12th I asked for another look at the situation, and Rex replied the same day with the following text and images:
I sent some plots comparing the baro reading with the NWS numerical model analyses. Green Xs are from the model. One is over the last 2 months; the other is over the last month. It appears as though it may be drifting closer to the model results over time. Overall it is -.26 mb off, and more recently only -.15 mb off. My initial evaluation after start up was only over a few observations. I clearly should have given it more time.
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| One month. |
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| Two months. |
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