How not to measure temperature, part 60

A good number of official climate stations of record in the USHCN network used for climate studies are at airports. All have been converted to the automated ASOS systems, and the placement of these is often chosen to be away from the airport tarmac so that temperature and dewpoint readings aren’t biased.

While climate monitoring is a secondary consideration of these stations. keeping these readings accurate is vital to aviation safety, particularly in calculating density altitude, which is used to determine the maximum takeoff weight for an aircraft and what runway takeoff length would be needed for a given weight.

But what happens to the accuracy when your “out of the way” station suddenly sits just a few feet from a building and parking lot being constructed?

Alert volunteer Janet Elias helped me locate the USHCN station in Lafayette, LA. The Microsoft Live Earth map showed quite a surprise in the making:


Click for a larger interactive image

Of course it didn’t always used to be this way, the Google Earth image, which is a bit older, shows the area before the construction started:


Click for a larger interactive image

Here is the NASA GISS plot of temperature for this station. A call to the LFT airport authority at this contact from their website told me that the contract for the new fire station facility was awarded in July of 2005 and that construction started shortly after that. The new fire station, show being constructed in the top photo is now complete.

So that calls into question the last two data points on this graph, for 2005 (21.11°C) and 2006 (21.19°C), which happen to be the two highest annual average temperatures since the 21.56°C recorded in 1973. For some reason, the 2007 data is not complete yet you can view it here.

Are 2005 and 2006 the real measure of air temperature or a result of bias from the new fire station being constructed within a few feet of the LFT ASOS temperature sensor?

How would NOAA or NASA or Hadley know if they don’t check out the station environment and examine for such issues?


Click for full sized original data plot

Previously I’ve touched on the problems with airports and the ASOS system, including the warm bias that the acres of asphalt runways, tarmac, and buildings can impart into the climate record from USHCN stations placed at airports. Plus we have the maintenance and accuracy issues of the HO83 thermometers used in the ASOS stations initially, which has been shown to be very serious.

The primary mission of the ASOS was for aviation, and remains that today.

So the question arises: why is NOAA, GISS, and HadCRUT still using data from these airport stations as part of the climate record? You can’t correct what you don’t know about or don’t evaluate, and it seems clear that such site level encroachment biases are not being examined in detail by climate researchers.

UPDATE- Reader Davis Smith writes:

Fifteen miles north of the Lafayette airport is another temperature site named Grand Coteau. It seems reasonable to expect the two to have similar trends (using GISS adjusted data) due to their proximity. A comparison of the two for recent years is here :


Click for larger image

Looks like a divergence circa 2004.

I also plotted the 106-year difference between the two sites:

http://davidsmith1.files.wordpress.com/2008/04/0417082.jpg

Both sites are flat land with the Grand Coteau MMTS located on a campus in a small town while the Lafayette airport is being encroached by the urban parts of Lafayette. My suspicion is that the trend difference reflects urbanization.

REPLY: Thanks David, UHI due to encroachment is certainly a factor, but so is local site bias. I suspect the two are additive in this case.

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26 thoughts on “How not to measure temperature, part 60

  1. Anthony,
    You bring up, by accident, another issue; The accuracy of the Goggle/Terraserver/etc. photos. Not the photos themselves but the “copyrights” on those photos. I’ve seen 4 years ago removed features on some of these carrying 2008 tags. Now I’m sure that they employ a full time division of lawyers at the firm of Dewey, Cheatham & Howe to claim this isn’t a violation of copyright law (it is) so I won’t go there. Rather I’d just like to remind your readers that nothing beats eyes on the ground in real time. That’s what you do and thanks for doing it.

  2. The “official” temperatures are from the weather station at the airport. The temperatures at my place, @ 12 miles away, are several degrees cooler.

  3. You bring up a good point about the accuracy of the HO83 electronic thermometers. I was a certified weather observer at the Lafayette airport from 1988 to 1996, and I can tell you that when we would take the weekly sling psychrometer readings to check the accuracy of the unit, the temperature reading of the HO83 would almost always be about one degree F. higher than the sling reading (tolerance was two degrees F.) I was there when they installed the ASOS units and were running them during the testing phase, and I recall that the temperature readings on it were also slightly lower on average than the HO83 (The ASOS unit was not officially commissioned until 1998.)

    I haven’t been out to the airport tower section in years, so I was surprised to see this photo. I had no idea they were putting a building and parking lot right next to the unit! Perhaps they haven’t gotten enough global warming out of the readings there?

  4. AW do not forget the CRN study done on the first CRN station comparing it to the ASOS nearby..

    REPLY: How could I forget what I’ve never seen? Linky?

  5. Another issue: growth. 30+ years ago, many airports were out in the ‘country’. Now cities have grown up around them. More concrete and asphalt. Official temps come from airports. Some years back, a professor at CU Boulder did a study showing how cities that had grown had much higher temperature increases than cities that had not grown. Forgot his name, probably got thrown out for his heretical view.

  6. Fifteen miles north of the Lafayette airport is another temperature site named Grand Coteau. It seems reasonable to expect the two to have similar trends (using GISS adjusted data) due to their proximity. A comparison of the two for recent years is here

    Looks like a divergence circa 2004.

    I also plotted the 106-year difference between the two sites:

    Both sites are flat land with the Grand Coteau MMTS located on a campus in a small town while the Lafayette airport is being encroached by the urban parts of Lafayette. My suspicion is that the trend difference reflects urbanization.

  7. Isn’t there some algore-ithm that is supposed to “clean” stations up by going to stations 1200 km away? If so, why don’t they just go to closer stations, as in this situation? Well, technically it’s unphysical anyway, since there is no reason to suppose a priori that trends should be similar/identical even for to well placed, clean stations a short distance apart. Of course, as we have seen, you have to try something, becuase the contaminations are so widespread that throwing the dubious stuff out would be equivalent to getting rid of all of it-and the meaning (what little there is) along with it!

    Perhaps at some point they will give up on the surface record and start looking for other “indicators” of AGW? You know, becuase ice melts when it gets warm, clearly any trends in glaciers ~must~ be due to AGW (to which I might comment-have you ever heard of salt? Actually, as long as there is little rain/snow, the small retreat every summer will make a trend.)

  8. The same situation has occurred here in Rockford, IL. Not only was there new construction but I think they moved from the Stephenson Screen across the street from the runways to a spot on the airport either near or between the runways. If I remember the last time I looked up the data it showed jumps in the temperature when they initially built and again when they expanded the UPS hub which is now the second largest hub in the nation.

    You can’t tell me that a dramatic increase in nightly flights is not going to affect the low temperature for the day.
    DKK

  9. Actually moving the stations away from the tarmac may not be a good idea from an aviation safety point of view. The reason there is weather stations at airports is that pressure and temperatures are needed to calculate takeoff performance and to set altimeters. To do this properly you want to know conditions on the runway, not over a grassy field some distance away. Airport weather stations are trying to accomplish two conflicting functions.

  10. You say, above, divergence occurs around 2004. My take on the GISS graph is that the two stations recorded roughly similar temps for nearly 8 years, til about 2003. Then the Lafayette temps stepped up a degree C. Your contact says the firehouse came in 2005, so, who knows what was going on 2 years prior?

  11. Hmmmm up tick in 03 fire station complete in 05 Lets see maybe they built the BBQ first and then started on the rest of the station. Some one check the bottom of the sensor housing for smoke stains…….

    It seems that NOAA would try to install new stations in national forests or state forest (clearings) using remote readouts. The current system is terrible. the current system with so far 54% ? with bias of >=2C. I don’t think that they will ever be able to do away with surface temp sensors but surely we can find better ways of measurement.

    Bill Derryberry

  12. Mike Bryant
    That’s the point alarmists don’t want us to know: During the Holocene the earth was 2 or 3° C warmer than today, yet Greenland did not melt.
    History is filled with lots of such inconvenient truths.

  13. Anthony,

    That comparison of two stations about 15 miles apart is very illuminating, and the differences between them can range beyond the level of supposed warming of the planet over the 20th century; so arguably those station differences just 15 miles apart are very significant.

    So much for the claim that temperatures correlate well over distances up to 1200 km.

    In the end, it doesn’t matter if climate models are any good or not; the raw data that is being fed into them is clearly bogus, and the degree of violation of the Nyquist criterion for sampled data systems, is so huge, that any claimed value for the mean global temperature has to be taken with a grain of salt. You only have to violate Nyquist by a factor of two to get aliassing noise all the way down to zero frequency, which of course is the sought average. It’s the old garbage in-garbage out syndrome. And apaprently the station temperature records even violate the Nyquist criterion for the temporal variation, by at least a factor of two as well, since once per 24 hours reporting is inadeuqte to reconstruct the daily temperature cycle either.

    So we have junk data going into junk models, and being reported as science.

    George

  14. That comparison of two stations about 15 miles apart is very illuminating, and the differences between them can range beyond the level of supposed warming of the planet over the 20th century; so arguably those station differences just 15 miles apart are very significant.

    Especially when beastly FILENET intrudes. (Sigh.)

    Also consider all those urban adjustments being lowballed as a result of being compared with rural sites with CRN4&5 violations!

  15. I decided to do some checking on this new building and the location of the ASOS site at the LFT airport. The new building is the new ARFF building, constructed about two years ago. The ASOS unit has since been moved, and judging from the lack of disturbed ground around the old site, some time ago. I couldn’t positively ID the new site, but I suspect it is close to the south end of runway 4L. There is an anemometer boom visible in that vicinity. Will check with NWS Lake Charles to see if they’ll tell me something definite.

    Interesting info on the area’s temperature differences. The LFT airport site clearly suffers from urban heat island effects more so than the surrounding region. I remember consistent large positive temperature bias at the airport as compared to the NWS certified temperature site located across town at KLFY TV, especially when there was a west to northwest wind blowing ( the airport is on the southeast end of Lafayette, Louisiana.) For that matter, you can compare the readings from KLFY and the airport as well as other sites in the area via the regional climate summary put out by the Louisiana Office of State Climatology. Here is a link to the monthly data, updated daily.

    http://www.losc.lsu.edu/divisions.html

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  18. Perhaps someone could explain why station pairs are used.

    To be able to see signs of global warming linked to CO2 you need two things (1) accurate CO2 data and (2) accurate temperature data. There is I believe accurate instrumental CO2 data but only since 1958 at Mauna Loa, as for temperature, well there are thousands of high quality rural weather stations throughout the world and especially in the US and the northern hemisphere that have long histories and NO UHI bias. These stations are totally uncontaminated and provide temperature data from a totally natural environment like Mauna Loa supposedly does for CO2.

    What do warmers such as Hanson/Giss do, well, they compare data from a highly UHI contaminated urban city weather station with CLEAN data from a neighbouring RURAL station. They then Use some secret algorithm put all the data through a computer which then gives them the result in degrees C. The odd thing is that the result always appears to show a steep rising temperature trend when the neighbouring RURAL CLEAN data shows only a flat or a slightly rising temperature trend.

    Would it not have been more logical to have discarded the contaminated data from the Urban stations and used only the clean data from the Rural sites.
    Surely data from fewer clean stations is preferable.

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