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Weather Station Hardware => Davis Instruments Weather Stations => Topic started by: SpHwk on January 20, 2018, 09:09:30 AM
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I installed a new SHT31 sensor in my 5162 two days ago. According to CWOP (EW8090) my humidity readings are still out of range within 24 hours. I am not buying it. My station is sighted reasonably well, other than my anemometer needing to get back up to 32'. It is not close to any roofs, asphalt, or concrete that would throw it off. I am in a heavily treed area but the nearest trees are about 50' away. I don't have fan aspiration on it so it's response will be a little slower. The stations CWOP is showing as a reference appear to be solid stations (Airport, and gov sensors).
Any thoughts?
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Any thoughts?
Stop caring about their "analysis".
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Looks to me like your average DP error is almost exactly the same as the mean error of your four nearest stations (assuming that column headed 'Dewpoint' in the table is the mean error). Don't know about the day/night differences, but looks like you're in good company for the mean error.
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Any thoughts?
Stop caring about their "analysis".
+1
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When you say you are sighted "reasonably well", does that mean you are in the sun or shade? You should be located in the sun, or humidity will be too high.
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I have seen posts in the past dealing with CWOP results not agreeing. I want my station to be highly accurate, not just "in the range". Maybe I am placing too much importance on CWOP, certainly if they are averaging all of the nonsense contributors on WU.
One thing that might contribute to my readings being different is the many swamps around us compared to the airport with no trees and a ton of concrete.
DoctorKnow
Yes, It has full sun exposure with very little shading. It gets slight shading late afternoon in the winter from one tree.
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For on-site comparison, you can purchase a psychrometer for $30 or less. Or, if you are connected with an educational institution, you might be able to borrow one from their science department for a day or two.
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I wouldn't discount the trees or microclimate too heavily. I'm in the same boat, down low adjacent to a wooded area with a stream running through it. My humidity readings regularly run on the high side.
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. According to CWOP (EW8090) my humidity readings are still out of range within 24 hours.
Any thoughts?
Pick one of the following:
1. Report something close to what CWOP says you should report.
2. Report the raw measurement from your sensor.
3. Report the actual humidity at the site of your sensor.
Note that 2 and 3 may be identical.
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You look fine here. http://mesowest.utah.edu/cgi-bin/droman/meso_base_dyn.cgi?stn=E8090&unit=0&timetype=LOCAL
and...
http://mesowest.utah.edu/cgi-bin/droman/regress_database_top.cgi?stn=E8090
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Whoa whoa whoa... I just went back and reread the OP.
Your station RH is being compared to other stations 6.3 to 36 MILES away? As I said originally, don't worry about it. IMO, there is no way to accurately compare data from stations that far apart...
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Thanks for the responses. I may pick up a psychrometer for comparison sake. SpartanWX, your comment about the micro climate got me thinking a little more about this. I left out a tiny little detail here, duh... I have a small 1/4 acre pond that is right at 100' n.w. of my station. I completely blew this off when thinking about the humidity. In addition to that he back of my property is heavily wooded. It can go from being completely dry as it is now to being 1-6" underwater when we get heavy rain.
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The mesowest page is something I had not previously seen. As SLOweather stated my distance from other stations may be the difference. Since I just replaced the temp / humidity sensor and am seeing the same results it makes sense that my reading are reasonable, but I still plan to verify with a psychrometer.
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You could always e-mail Phil Gladstone at CWOP and let him know what the issues are. I know what you mean about wanting high accuracy, not just in-range. I just recently went to a Vue unit from a LaCrosse 2813. Even with the LaCrosse unit, I did everything I could to make sure it could be as accurate as possible. This included placing the anemometer on a mast above the chimney, the T/H sensor in a radiation shield, and the rain gauge level on a fence post. I was always usually at 99% or higher with each of the CWOP ratings.
CWOP does not pull data from WU for their site. You have to use software to upload your data to their server. However, there are people with really crappy stations that either malfunction and/or are sited poorly. There is someone in my community a few block from me with an Ambient station that is clearly having issues with pressure. I watch his rapid fire data from time to time and it spikes about .21 inches. For example, just now I watched his pressure go from 30.29 to 30.08 and back up to 30.29 in about a 90 second span. His CWOP summary page is full of errors. I wish they would purge the stations that report poor data over a long period of time. I know the worst 5% they do not chart.
Also, another reason you want accurate data is because the NWS/NOAA actually uses your data for weather forecasts through CWOP/MesoWest, although maybe a small sliver of their overall method. Not sure if you knew this, but here is your "government weather" page: https://www.wrh.noaa.gov/mesowest/getobext.php?wfo=mtr&sid=E8090&num=48
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I joined the CWOP list and had also gone back and checked my data analysis page. It appears that my reading are now within their expected readings after replacing the sensor.
I plan to upgrade to a 24hr fars in the near future. This will likely help also as we generally have very little breeze or wind here.
CWOP also shows my anemometer sheltered from the wind. It was at 27' but had problems with the pole and had to drop it. I have not had the time to appropriately fix it and put it at 32'. This is going to require guy wires which i was hoping to avoid.
Another consideration of accuracy is not only my ponds proximity but also my sprinkler system. I have the ISS sited so that the sprinklers wont throw water on/in it, but that doesn't mean the sprinklers couldn't throw off my humidity readings. There is no place i can really site it far enough away from the trees, that is not covered by the sprinklers. :-(
Thanks for the link to the NOAA page, iv'e seen it before but hadn't looked at it in a while.