We shouldn’t measure climate data at airports with aviation instruments, period.

That’s perfect. What a great, “duh” summary to tie things up at the end of such a great post too. It’s hilarious because the statement’s truth is clearly provable, yet this is non-obvious to the people hired specifically to know these things. That, or intentionally ignored for some budgetary or political agenda.

Science ≠ politics, we’re much poorer when they’re confused.

I am surprised that the operating range of the AWOS sensor is -31F. I wonder if the newer Vaisala sensors they are putting into AWOS (HMP45D?) is adequate to -40F/C. Someone reading this post may know the answer to that.

My understanding with the current ASOS system is that the 1088 hygrothermometer is still used for temperature measurement and the mirror is still maintained and used as a backup dewpoint sensor. The Vaisala DTS sensor (a variant of the HMP 233) is now used as the primary dewpoint sensor and has been shown to be much more reliable (for the most part) than a chilled mirror system is out in the field. I believe this is the case at most ASOS sites, although there may still be some ASOS sites (second and third order stations) which are using the chilled mirror for obtaining dewpoint.

What happened to all the John Van Vliet aka John V. messages / discussions here that i have trouble finding back. Certainly google time machine hasnot forgotten them and bloggers refering to other blogshave not such as http://bigcitylib.blogspot.com/2008/09/decline-and-fall-of-surface-stations.htm

WotSoUp with this project. Is this a science blog or a collection of from the hip PE shooting?

REPLY: What that article from the “unbiased” champion of science “BigCityLib” does not mention is that JohnV did the analysis without any notice to me, terribly prematurely, before the project had even reached 30% of the nation in surveys. As a result, only 17 stations were used in the USA analysis that represented the “best” CRN1 and CRN2 stations. The geographic distribution was clustered and not representative of the entire USA network.

If I had done the same thing, given the few stations used, and shown a difference, I would have been vilified for using incomplete data and coming to a conclusion prematurely. This is why I have not done an analysis yet, only a running census of stations.

Thus, I’m working hard to get the majority of the USA surveyed so that a correct analysis CAN be done, rather than a hurried one for the purposes of denigrating the project before a majority can be completed.

But that obviously doesn’t matter to people like yourself that repeat this story again and again without bothering to look at what was done.

But, since you didn’t do your homework, and it is clear from your snark level, that you have no interest correct methodology, your criticism falls flat. – Anthony

tiny…

Hmmm. Thanks Jim. So all the AWOS sites are suspect for any reading below -31F and are at best in an uncalibrated non-linear range. While the Canadian Clippers are running down to -50F in some places (per whatever reported those temps…).

Do we know if they are prone to over, under, or random report when out of range? And do we know what Canada uses?

What I’m thinking about is the impact of having dodgy ‘lows’ averaged in with highs. If it’s a random non-calibrate it ought to sort of wash averaged over enough sites. If it’s ‘runaway low’ then the bunch of record lows becomes suspect. If it’s ‘fail to track lower and report high’, well that would show ‘global warming’ anytime real temps went record low; given the average h/l method. Is there anyway to characterize the probable impact of the error induced at below -31F?

How big a percentage of GISS is AWOS? Is there a geographical bias for or against very cold places? (We don’t do below in coastal California 8-) so it doesn’t matter here…)

Somehow more ‘settled science’ is decidedly unsettling.

To be honest, I did not know the specific temperature range of the AWOS until doing research on it yesterday. However, my general mistrust of AWOS in IL was based beforehand on years of experience with reports on both end of the temperature spectrum. I have no control or input into the siting, Q/C, maintenance, or archiving of the data. On the other hand, I should say that I was pleasantly surprised by the response of the airport operator and the vendor in this particular case.

One more thing on the Rochelle AWOS, Anthony. I talked to the airport manager today (Jan 20) and he said they replaced the temperature sensor last Thursday as well as calibrated it. Of course by that time, it had warmed up to -12F or so. So I still don’t know how it would perform at the -30 to -40F range.

As far as ASOS goes, yeah, I’m familiar with the sensor changes, undocumented moves, questionable exposure, etc. In fact, we have a running battle with the local media wanting to use the nearby ASOS site at the airport (KCMI) to break records set by our 120 year-old coop station in town (118470). I generally avoid ASOS sites for climate change studies. However, sometimes they are the only game in town with respect to historical records of winds, dewpoint, precipitation type, etc. I always try to warn people when they use those records.

To beng – yes, I wish there was another reliable instrument on site to confirm the observation. The downside to relying on automated systems is that there is no trained observer that you call and send out with the ol’ sling psychrometer.

Jim Angel

Even I have 2 thermometers outside the house. :)

Jim I’m just wondering, was the knowledge of the specification range of the AWOS sensor known prior to making the decision, or was it a product of the research here now in defending the decision?

Also, are you aware of the HO83 sensor issues with ASOS? Did you know that many of them have been retrofitted with Vaisala sensors, leaving only the HO83 portion for dewpoint determination, while an entirely new Vaisala aspirated sensor assembly is attached to the other side?

Also Jim, I think it is unfair to characterize my article as having “…charges of political motives and the like” since I focused solely on sensor issues. I made no charge of any political motive of any kind.

Andrew ♫

Andrew asks his girlfriend Mona Lisa to pose for a portrait on Jan 1, 2009. He uses a pencil and a piece of paper only. She sits for him, he sketches, and its fantastic. So much so, Andrew states:

“This sketch is perfect”

He puts the sketch on the table in his basement and it sits there.

A month later, Feb 1st, 2009, he has a party at his house and people convene in his basement. Andrew’s friend Alfred sees the painting and says:

“That painting is perfect! Except Mona Lisa’s forehead is too big”

Andrew says: “No it isn’t, I should know how big my own girlfriend’s forehead is.” ;)

So we have a problem. How do we know who is right? Is it Andrew or Alfred?

The only way to tell who is right is to go find Mona Lisa and look at her forehead again and compare it to the sketch. To correct the problem with the sketch, we now need to go find an eraser too. I didn’t make the sketch with all the tools I would eventually need to be right in Feb 1st 2009, cause I didn’t know I would need them. The sketch I made was wrong. In any case, the statement

“This sketch is perfect” from Jan, 1 2009, is wrong.

I should never make such a statement, given the current understanding.

Anyone who ever says, “The science is in…” is wrong.

AGW will always be wrong, unless in the future someone understands the earth and every thing that happens in it. Right now, It’s too big a claim on it’s face.

Temperature is really a local issue someone is trying to make bigger than it really is. Local measurements are for local results. That’s why it is vital that we get good measurements as often as possible, wherever possible, and record them as history.

Andrew ♫

Another thing to consider in this discussion is that the AWOS sensor was design to operate reliably in the range of -31F to 131F (according to a Vaisala brochure I have). The ASOS sensor was design to operate in the range of -80F to 130F, according to the NWS ASOS site. So that raises another interesting issue – should we rely on AWOS for record cold temperatures outside it’s normal operating range?

Furthermore, while we wish the level of uncertainty in any measurement system is fixed with respect to temperature, in reality it can increase as you get out on the temperature extremes. This makes it even more challenging for determining state records.

Overall, if you set aside charges of political motives and the like, determining state records in a non-trivial exercise and an interesting climate/meteorology problem in itself.

Jim Angel

Hi. Though it may not be easy to spot my comment among this huge number of other comments on this blog, I would like to ask you whether there exists a social study based on the following (or very similar) method::

1. Let S be a set of temperature readings.
2. Redistribute S in a group of scientists for them to analyze the temperatures. Let their findings and conclusions be named “Findings+”.
3. Invert all temperature values in S using the function f(x)=(K-x), where ‘x’ is the temperature and K is a constant. This produces dataset Sinv.
4. Redistribute Sinv in the same group of scientists for them to analyze the temperatures. Let their findings and conclusions be named “Findings-”.
5. Finally, compare “Findings+” with “Findings-”: For all data points D in S: Let P(D) be a property attributed to the data point D and Pinv(D) be the expected “inverted meaning of P(D)”. Then, if “Findings+” contains P(D), “Findings-” should contain Pinv(D).

From the comparison we should be able to determine whether scientific findings are either biased toward higher/lower temperatures or are unbiased.

Exists there a scientific article which uses such a method?

METAR = Aviation Weather Observation (Don’t ask, it’s French)

KRPJ = Station Identification, Rochelle, IL

16150Z = The date and time (16th, 1505 Universal time = 0905 CST)

AUTO = Automatic weather station with no human involvement

23005KT = Wind direction and speed (from 230 degrees, 05 Knots)

10SM = Visibility (10 statute miles)

CLR = Sky Conditions (Clear, in this case)

M35/M39 = Temperature/Dewpoint in degrees C to the nearest degree (-35/- 39) {the “M” signifies “Minus”}

A3070 = Altimeter setting (30.70 Inches Hg) {what the barometric pressure would be if the airport were at sea level}

RMK AO2 = Remark: Weather station type AO2, which has a more sophisticated precipitation discriminator which can tell the difference between rain and snow, etc.

T13531394 = Temperature/Dewpoint to the tenth of a degree C (-35.3/-39.4 {the “1″ in front signifies “minus”, don’t ask me why they just don’t use a minus sign}

You are asking the wrong question, “scientifically.” The question shouldn’t be ‘who do I trust’? That is not scientific. The question should always be ‘what does the data say?’

Until we can say ‘this is the data’ and everyone (who currently disagree) agree and records it as history, starting today, we have no knowledge to build on.

Andrew