Experiment config on July 13th. The screens were subsequently moved further apart. Note aspirated air temperature reference in forground.
I’ve been sorting through some of the data, and have found many similarities with many days of data. So I thought I’d present a typical day from this summer. The is 8/27/07, exactly one month after I started the experiment data logging.
I chose to show this day for starters because I can be certain that the whitewash was fully cured and no “newness effects” related to the conversion of CaOH to CaCO3 would remain. Whitewash cures by chemical reaction with air, not by drying.
First here is a 24 hour plot of the raw data, at 15 second sampling intervals, note that it gets noisy on the way to Tmax due to afternoon winds about 5-10 mph. Another factor for noises is that the response time of the NIST calibrated thermistors is fairly fast, in seconds.
Full size graph: paint-test-082707-raw.png
Since it is harder to visually determine separate Tmax and Tmin with noisy data, I ran it though a data smoothing algorithm to produce this plot.
Full size graph: paint-test-082707-smoothed.png
Here is the report from my data plotter on peaks for this graph:
Air Temp
Minimum = 55.38 at X = 8/27/2007 6:52:48 AM
Maximum = 95.04 at X = 8/27/2007 3:40:50 PM
Whitewash
Minimum = 56.22 at X = 8/27/2007 6:54:35 AM
Maximum = 96.94 at X = 8/27/2007 3:43:07 PM
Latex
Minimum = 55.92 at X = 8/27/2007 6:40:25 AM
Maximum = 97.74 at X = 8/27/2007 3:42:06 PM
Bare Wood
Minimum = 56.36 at X = 8/27/2007 6:39:24 AM
Maximum = 98.47 at X = 8/27/2007 3:42:36 PM
Since in regular use, COOP/USHCN stations report their daily max and min to NCDC for inclusion in the climatic database, I have provided zoomed graphs on the Tmax and Tmin periods.
Here is the zoomed Tmax graph:
Full size graph: paint-test-082707-tmaxzoom.png
And here is the zoomed Tmin graph:
Full size graph: paint-test-082707-tminzoom.png
As a secondary reference besides my own aspirated air temperature, I’m fortunate to have a CDF RAWS station within about 200 yards, on similar terrain and ground cover. It has a non-aspirated shield, and also has wind, and solar radiation among other sensors.
Here is the temperature plot from it:
Full size graph: temp-chi-raws-082707.png
A complete suite of plots, including wind and solar radiation in watts/m2 can be had from the CDEC data query web page.
As I wade though this data, I’ll be publishing additional days, and more detailed analyses, followed by a final report that covers everything that I’ve learned.
In the spring of 2008, I’ll be repeating this experiment at a slightly different location, there is a late afternoon bias for tree shading to the west that I want to remove from the experiment.
I’ll remind all readers that this is a single day, and that conclusions should not be drawn from it as it represents a single data point for Tmax/Tmin. Please be patient while I do further analysis.
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Rev, would you clarify how the NOAA (et alia) calculate daily temps. Is it just an average of T-max and T-min (which you said they record) or is it a continual average. If it is the latter, there wouldn’tseem to be too much difference. But if it is the former, the difference could be quite pronounced. (Yes I realize this is only a one-day graph. “Patiently” awaiting long-term averages!)
REPLY: As I understand it, the observer record the max and min daily temp, plus temp at time of observation on a small notepad form, then transcribes to a B91 form to mail in to NCDC. The observer rounds the max and min and observed temperature to the nearest whole number on the B91 form.
NCDC takes the B91 form and transcribes into a computer database. From there (as I understand it) a daily average is created, and from those, yearly average which is what me most often see in climate studies. – Anthony
Jerry Bono
I digitized the Chico points and took the average of 24 measures …. 78.14F.
If we average the Tmax and Tmin we get 76.0F. That is 2.14 degrees lower than the integrated value and that is a lot . That is about 1.9C difference between the two methods. When was the B91 form put in place? If it was decades ago like in the 30’s then I can see why this was done, GW was not an issue then. If it is a recent invention then shame shame shame.
Looking at the zoomed Tmax, if we take the average Tmax for the three boxes and compare to the air temp, the boxes are 2.69F hotter than the air. Similarly, for Tmin, the boxes are an average 0.78F hotter. If this holds for these stations in general, then the daytime Tmax has 3 times the error than an early morning Tmin. It bothers me that the Tmax difference is so large.
Is there any accounting for this?
If this is a typical day, which clearly shows a differences between each Stevenson screens only a few feet apart.
This could mean that instrumental temp used around the world are really uncertain since their location are inconsistent (as shown with your other project surfacestations.org), sometimes moved around, with different type of instrument and their maintenance unknown.
This could also mean that we are mislead by instrumental temp which don’t corroborate well with satellite, balloon and up to date proxies
Could you possibly adopt a theme? “Stevenson Ranch” is catchy. We could make all kinds of snarky comments about stray heifers and bleached bones and such. The media would eat it up and unwittingly give venue to the opposition.
The thermal mass of the enclosures appears to contribute a variable and erratic error in all cases. Makes one wonder if the housing of the reference thermistor has the same characteristic? Bottom line: We have no idea what the historical air temperature was, and it is difficult to envision a correction scheme which could exactly correct these errors to the accuracy the modelers seem to think we have.
Thanks for the info, Rev.
So, for this particular (summer) day, the T-Max/T-Min average was 0.51F warmer for latex than whitewash.
T-max was 0.8 higher for latex at T-Max and 0.29F lower for T-min on that day.
It will be interesting to see if this basic effect holds, and what the seasonal variance will be. (Whitewash weathering may well make all it harder to figure.)
keeping thermometers in boxes. that should give accurate temps measurements. yah.
More good in-put. I had an introduction to painting a SS in the mid 70’s. This experience was done mid-May. Others at higher elevation done later. Used latex exterior white (the kind that corroded thru the can bottom in 1 year). Frequent camping/jeepin trips to the Sierra Nevada allowed observations of other SS in State and National Forest applications. There were several stations that used white wash. My quess (of today) at these locations the supervisor was a purist. These must have been done annually, I always saw “well maintained” white washed units in July.
I never gave this SS-temp a thought.
Dude, you need to irrigate your yard! 😉
Hi Anthony,
Good to see you’re plowing forward on this project. It should provides some useful observations about the historic record. I had a couple of random questions occur to me as I was looking this over:
1. Is this an effort to validate a previous study(s), or is this a new twist? (btw, you should publish either way, in this layman’s unsolicited opinion)
2. Is the image of the CRSs facing south? (yes, you taught me well!)
Godspeed, Anthony!
REPLY:
1. New study, AFIK no other researcher has done this type of test with 3 screens in parallel
2. Yes the photo was taken looking south
One simple thing to look is a ‘simulation’ of what an observer would record for all three stations WRT Tmax and Tmin. That is scan though the daily data,
record the Tmax and tmin, round as an observer would round and report
out the measures, so if whitewash records a Tmax of 95.3F that’s recorded
as 95, as an obsever would do. and if latex reports 95.6 for that day, then
round to 96F as an observer would do. same for Tmin. It might make
an instructive quick pass through the data.
REPLY: Mosh, great suggestion!
Anthony, make sure you double check the rounding rules, I’m not sure
what Noaa suggest for xx.5, futher when (tmax/tmin)/2 is calculated
this figure is also rounded, JerryB and I once had a convo about this
over on CA, he hasnt been around much, so you might have to go back
to source data over at USHCN to figure out the rounding rule. My vague recollection was that they rounded UP at .5
Come to think of it, if it’s rounded to whole numbers, you get a +1C at T-max and flat at t-min. So the plus-half-a -degree dif. actually comes in at a +1C.
Hmmm.
Evan Jones (22:45:12) said:
“Come to think of it, if it’s rounded to whole numbers, you get a +1C at T-max and flat at t-min. So the plus-half-a -degree dif. actually comes in at a +1C.
Hmmm.”
I see his point. It’s possible that there is a “rounding bias” that may not be accounted for.
It may not make a difference, but I’m seeing from .1-.4, round down, and from .5-.9, round up. That makes a +.1 rounding bias (4 readings would be rounded down, while 5 readings would be rounded up).
Also, why have digital thermometers with an accuracy in tenths or hundredths, if you’re going to the nearest whole number?
nobody has paid much attention to the rounding bias. My QUICK glance at USHCN suggested an upward bias. However, if this rule is always followed, then there is no trend bias just a DC offset
Actually, that comes out to an average +0.2C offset, using only T-Max/Min.
Because we are not adding and then rounding, we are rounding, then adding.
And I guess it’s a + 0.3C bias if you toss in TOBS.
“Ah’m a headin’ fer the last roundup!”
But wouldn’t this tend to put a “step” into the curves that Anthony posted, that is, a temp at 51 degrees (example) wouldn’t appear to change until a temp of 51.5 degrees is reached, then a step up to 52?
Same on the low. A temp of 51 wouldn’t appear to drop until the temp reached 50.4, then a drop to 50.
It would appear to “flat-top” the curves.
Hope I’m making sense.
Hmmm.
Yes. But since they aren’t measuring continually, it doesn’t show up.
Asi it is, measuring at three points gives three 10% opportunities for an upward bump.
But as St. Mosh says, it’s an offset, not a trend.
Unless methods have changed!
Was there a time when only T-Min/Max was used? If so, adding TOBS would create a spurious +0.1C upswing in the record. (Or almost 15% of last century’s warming.)
Not to keep beating this horse, but it’s appearing, at first glance, that the time of obs is being overridden.
Here’s what I mean:
Example: let’s say that the temp rises through 50.5. That would be raised to 51, at, say, 10am. If the temp never goes above 51.5, there will never be anything recorded over 51.
If the temp reaches Tmax at noon, then drops below 50.4, then the recorded temp would be drop to 50 (at, say 2pm).
That means, that no matter what the Tmax really was, you would have recorded a “window” of temps, not a “snapstot” of Tmax.
The reading would be showing the temp of 51 from 10 am to 2 pm, and totally missing the Tmax.
Maybe I’m just reading this too deep.
Well you have to round it off somewhere.
But it seems a bit crude to round to the nearest degree when one is spitballing over amounts less than the MoE.
OTOH, I suppose one can get by with oversampling. But still …
There is a clear pattern of rushing to print with stuff that helps you and holding off with what hurts you. Why are you publishing one day only? If it’s non-representative, why is it shown? If it is representative, show that mathematically.
I don’t trust you to pick a day at random. I think you will show stuff that helps your preconception preferentially.
REPLY: TCO, its all coming, just not on the schedule you demand. I can’t do everything at once, and I don’t really care if you think you can’t trust me. That’s funny coming from you ….people who have interest and character, collaborate with me and reveal themselves. You don’t. You are still just another phantom with no name other than “TCO”. As far as I can tell your email and website are bogus. So don’t lecture me about trust please. Trust is a two way street, and you’ve provided nothing.
Like I’ve said, I’m one man, with a business, a family, and many things to do. Doing this and the surfacestations.org project simultaneously on my own dime. Its a balancing act.
When I get time there will be more, in the meantime please be patient. No wonder CA folks voted you “most irritating”.
Rounding.
I worked at the National Ocean Service/NOAA for 32 years. When I started, we used odd/even rounding, i.e., odd numbers round up, even round down. I even wrote my computer subroutines to round this way.
95.5 = odd, round up = 96
92.5 = even, round down = 92
With large enough sample sizes, this should remove any round up bias.
REPLY: True, but the NWS lets the observers do the rounding before recording the data, and it is unlcear if they use this method.