Dew Point

I’ve been send data to CWOP for about a month now.

hi
the dew point is calculated from the temperature and humidity
your humidity is reading not too flash either…i.e the DP differences follow the humdity differences
the station type you are using does not have a very accurate humidity sensor (the ws2010)

My dew pt’s are effected by the road next to the property. When I moved the station, I had to put it closer to the edge of the property since there was no other place to put it. Now my dew pts at night are spiked as a result.

Are your readings that calculate the DP taken from the 2010 or VP2? The VP2 with FARS should not be showing those spikes. My VP2 with FARS graph for comparison…

The FARS should keep your readings consistent. It looks like your spikes occur during daytime readings only…

It’s from the VP2. I have it located about 5’ above ground level but it is over some plants that are about 2’ high and not the short grass as is suggested. Didn’t think it would make that much difference. Will it? I’m taking the WS-2010 out of my signature. I don’t even track it any longer.

hummm
the stations that the quality control is checked against…how do you know they are accurate too??

Brian, I don’t know about their accuracy. I’m just going by the CWOP comparison. Could a combination of the variance in the temp and humidity recorded be causing the spikes? If you look at my page you’ll see they are not very smooth.

yes

Is there a way of smoothing them? Or would that effect the accuray even more? Something like you did for the wind speed. That really made a difference in the apperance of the graph.

i dont think that would do much…that would not affect some underlying reason for having an incorrect temperature and humidity reading in the first place…(and a resulting dew point (although if your temperaure is reading too high, then your humdity will read too low…and so the DP still should be reasonable)

in 10.25p I now have a 1 hour smooth added to the year to date graph (via graph history)
for temperature/humdity and dew point…
looks much better

Dewpoint is one of the most variable parameters measured in CWOP. Most of the dewpoints in home wx stations are calculated and not measured directly. I looked at your 28 day comparison and you were within tolerance at:

http://weather.gladstonefamily.net/site/C3754

If you really want to try and compare nearby sites I would try around the middle of a windy day when the air has really been mixed out to compensate for any localized effects. The QC data provided by the CWOP site is a great service…I refer to it a lot…but you have to be sure the nearby sites are accurate as well. My location is getting flagged for dewpoint but the nearest site to mine is an AWOS that has been reporting dew points several degrees above the surrounding ASOS and AWOS locations. I compare my own site with a sling psychrometer.

yes, very good points!

One last thought…I had to reset the batteries in my FARS after it arrived, shipping had apparently rocked them loose enough that they weren’t taking a charge from the solar panel.

I just checked, my fan is running. But I’ll check in the morning before work. If they aren’t fully charging they’ll most likely be dead by then. One thing about this area. Many of the stations I’ve checked may be on the water or at least closer to it than I am. This area has several rivers and large creeks plus the Chesapeake Bay is about 5 miles from me. I know for sure four within a radius of 12 miles are on the water. I often see a temp reading of 8-10 degrees difference between them and my station. They are also more exposed than I am. My house is surrounded by tall oak and popular. I’ve had winds 1-2 mph and they are seeing 15-20. I’m going to look into a sling psychrometer. It is almost Father’s Day.