Nightime temp error

[merlinwx]

I see a definite trend developing between daytime and nightime temp QC readings.  Daytime readings tract right on top of QC tracks but right at sunset the actual and QC tracks split to about 4.5 degrees difference (actual above QC).  Then before sunrise, QC and actual converge to coincidence.  Anyone else seeing anything like this?   

[jgillett]

Yep. Been seeing that here almost since day-1 (over 4 years now) with my VP2. Finally gave up worrying about it.

[DanS]

I see a definite trend developing between daytime and nightime temp QC readings.  Daytime readings tract right on top of QC tracks but right at sunset the actual and QC tracks split to about 4.5 degrees difference (actual above QC).  Then before sunrise, QC and actual converge to coincidence.  Anyone else seeing anything like this?  

I see on your CWOP pages that the closest site is 13 miles away and if that's what they use for QC I personally wouldn't sweat it. I also see some other remote possibilities from your station installation pics. The fat tree limb underneath and/or the huge stones on the ground below could retain heat from the daytime sun.?.? If you really have a problem with it you could try a temporary relocation to another area free of these possible 'heat retainers' to see if the QC temp charts change.

Here is my CWOP temp graphs with one sensor (DW2642) mounted next to the house (north side under an overhang). The DW4009 sensor is out in the open with grass below and nothing nearby that holds the days heat like the house obviously does here. VTCC is the nearby airport.



My 2 bucket tips worth.

[ocala]

I agree with Dan I wouldn't sweat it either. It's just the micro-climate for your area.
Below is my graph for 3 days. You can see I'm below the other stations in the area at night. It's been that way for 5 years.
Oh yeah, interesting installation there on the tree. I have never seen a station mounted on a tree.

[merlinwx]

I agree with Dan I wouldn't sweat it either. It's just the micro-climate for your area.
Below is my graph for 3 days. You can see I'm below the other stations in the area at night. It's been that way for 5 years.
Oh yeah, interesting installation there on the tree. I have never seen a station mounted on a tree.

I think you're right about micro-climate.  There is a neighbor VP2 station about a mile down the road at the same elevation (non reporting station).  I've been comparing my data with his and we seem to be tracking within .5 degree.  Researching the reporting stations around my area, looks like the same thing happens at night just to a slightly lesser degree.  I still find the phenomenon interesting...makes you wonder about the QC algorithms MADIS uses.  Don't think I'll worry about it...I'm probably closer to truth than MADIS in this case.

[ocala]

All MADIS can go by is what's reported to them. They don't check each station for the correct installation.
A station that has sensors mounted over asphalt  or concrete on a hot day is going to be different then one mounted over grass. Also, said station is always going to be an outlier in regards to data. That is going to throw off  the QC analysis. Even if all the stations around you are mounted correctly their differences in elevation will affect the temp reading. Don't get caught up in getting two thumbs up for your station. You just need to know that your set up is correct. Judging by your post here you already do.

[Stetson1]

Closest station to me is 2 miles away and 2 hundred feet higher. We track pretty close but the overall QC is off by 4 degrees every night. The rest of the stations in my area are anywhere from 3.4 to 8 miles away. 2 miles here could mean 300-500 feet in elevation change so I would expect some differences, but seriously 8 miles in my QC is a little over a 1000 feet different elevation wise. In addition, I have a creek that runs behind my house and everyone in the neighborhood knows we have an interesting micro-climate going on.

I used to worry about my ratings and decided that it was a waste of time.

Todd