I’ve spent a lot of time on this blog showing how badly maintained and situated the stations in the USHCN network are. And rightly so, the majority of them have issues. But, finding the good ones is actually more important, because they are the ones that hold the true unpolluted temperature signal. Unfortunately, the “good ones” are few and far between.
But when one comes along that is a real gem, it deserves to be highlighted. I present the USHCN climate station of record for Tucumcari New Mexico, COOP ID # 299156, located at the Agricultural Experiment station about 3 miles outside of the edge of town.
I “had” (he just moved to St. Louis) a nephew who lived in Tucumcari, and he just happened to be friends with the director of the experiment farm. Before my nephew left they both helped me get this survey done.
Click picture for additional images
Surfacestations.org image gallery link
This station has several advantages:
- Length of continuous record – going back to at least 1946 at this location, possibly to 1905 but NCDC MMS metadata stops at 1946.
- Length of continuous instrumentation – using mercury max/min thermometers
- Length of continuous data record – there doesn’t appear to be any missing years
- Lack of encroachment – 3 miles from the northeast edge of town, little development, little UHI. Tucumcari is well off the beaten path of development. Population actually declined 12% in recent years.
- Good siting – the station rates a CRN2 due to distant trees and sun angle, and one small asphalt road 70 meters away.
See the station survey report here (PDF) You can also make out the station on Google Earth using this link. After opening Google Earth, zoom in and the fenced outline and screen will be visible.
Eyeballing, you can see that the temperature data trend for Tucumcari is slightly positive over the last century, about 0.5°C, but there is a “bump” in 2000, which brings it to about 0.9°C. This same bump appears in neighboring stations such as in San Jon (33km away) and in Boys Ranch (135km away). There is nothing in the metadata location or equipment record to suggest a reason for the bump. So, either the bump is naturally occurring, or there is something we don’t know about that changed in the local environment, or we have another data set splicing error like the GISS Y2K debacle from last year.
Click for larger graph from NASA GISTEMP
I plotted the data provided by GISS (which you can find here) to show the effect of the “bump” at year 2000 on the overall trend:
Click for larger graph
Here is the data plot after the GISS homogeneity adjustment, I’ve hue shifted my saved version to red to help keep the graphs visually separate:
Click for larger graph from NASA GISTEMP
And here is the overlay of the USHCN data from GISTEMP and the data from the GISTEMP homogenization process:
In this case, the GISTEMP homogenization code appears to do what would be reasonably expected; reduce temperatures in the present to account for population growth and UHI. I’ve pointed out more than a few times that the GISTEMP homogenization adjustment often becomes flawed for truly rural sites like this when there are large cities within the 250km up to 1200km (depending on process) adjustment zone that Hansen uses, that have accelerating UHI trends. Due to these cities, often the past of a rural station gets adjusted cooler, resulting in an increased temperature trend, such as what happens at Cedarville, CA. Hopefully we’ll have a detailed analysis of that adjustment from John Goetz soon.
If you look at this list, you’ll see that there are a lot of rural stations within 250km. Tucumcari has the advantage of being truly in the middle of nowhere when it comes to other big cities. The closest big cities are Amarillo and Lubbock, but as I understand the algorithm used, when they are near the edge of the 250 km zone, their weighted value decreases.
In this case though, the GISTEMP homogeneity adjustment doesn’t take Tucumcari’s declining population into account, it only uses nightlights, and while the population may dwindle, town infrastructure usually doesn’t; streetlights counted around the station likely remain.
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Anthony, you say over at CA that you will look into irrigation changes as a possible cause of the warming in the 1990s.
Given Christy’s study (linked above), which finds a regional warming effect from irrigation, the total volume of water used in irrigation from the Tucumcari Project would be an interesting comparison to the temperature record.
All I could find online is 10 years data of total irrigated land in acres, which ends in 1992. Full records doubtless exist somewhere. Also I think volume of water used in irrigation is a better metric than area irrigated because volume will determine the amount of water vapour introduced into the atmosphere. The 2 may be closely related. However, one description of the scheme says,
“Irrigated pastures fill a niche in this area because of their ability to produce under varying levels of irrigation,” said Rex Kirksey, superintendent of NMSU’s Agricultural Science Center in Tucumcari. “Pastures remain a viable option in many situations where irrigation water is too limited or unpredictable for corn or alfalfa production.”
Which makes me think there isn’t a good relationship between area irrigated and water volume.
http://www.usbr.gov/dataweb/html/uctucprjdata.html
And at the risk of belabouring the point, the significance of Tucumcari may be that it shows the effect of irrigation without any other significant local effect. For those of you who didn’t read the Christy paper, he found, in a region remote from irrigation, temperatures declined over the 20th century.
BTW, what clued me into the irrigation effect is that here in Perth Western Australia a typical sunny day in summer is 35C to 38C. However, we get a few days each year when we go into the 40s. I think 44C was the hottest day this year. These hot days are invariably humid, although without cloud, and nights are much hotter than normal in summer; +10C or more on some nights. I realized the 40C+ days occur after rain in the interior and the normally dry winds from the interior become relatively humid.
Its hot because the air is humid and the sky is clear. The extra heat results from a near ground greenhouse effect from the extra water vapour.
REPLY: I just completed my basic research, posted on the main page, and like you could not find the overall water volume numbers for the entire project, only a portion. But I did find something else. Leakage. The irrigation canal system that serves the area near the USHCN station loses HALF of the water to the surrounding area, and it is getting worse.
Mosher, of course you mean you “couldn’t care less…” Totally opposite meaning from “could care less”.
[…] Sunday I posted about the USHCN climate station of record in Tucumcari, NM highlighting its positive points since it has all the hallmarks of a well sited station with a long […]
Anthony, I don’t know if you’ve addressed this already here or on Surface Stations, but seems germane to all the rural monitoring sites.
It’s interesting to me that NOAA acknowledges the importance of avoiding agriculturally developed sites in their licensing agreement handbook:
“Licensor and Licensee recognize the importance of maintaining Site integrity for among other things, to… minimize potential impacts from long-term land use and land cover changes on the climate record at the USCRN Site, such as irrigation and tilling of the land near the site, typically within 100 meters.” —From U. S. Climate Reference Network Site Information Handbook, Pg. 17.
But cultivation and irrigation, considered “natural” land uses, might tend to creep past these 100-meter barriers over time, and if Christy’s essay is right, these land uses affect temperature readings more than I realized.
Thanks for your ongoing investigation (I read on to part two of this).
I’m willing to bet irrigation affects temperatures kilometers away from the source.