Jul 24 2007
Tucson USHCN Weather Station
I was wondering when someone would finally get around to posting pictures of the Tucson USHCN surface station online. That day was yesterday. It was originally posted (I’m guessing) at SurfaceStations.org, and quickly picked up by Climate Audit.
The biggest complaint offered by these sites seems to be that the station is in a parking lot. It’s true that situating a weather station in a parking lot is not the best location. However, we need to think about what effect this will have on temperature and precipitation measurements. Everything else equal, a temperature reading taken over an asphalt surface will be higher than one taken over a grassy area. But we’re not interested in temperature. Wait a minute, I thought we were interested in temperature. Nope, it turns out we’re interested in the change in temperature. Just because the station is located in a hot spot means it will add a positive bias, but it does not necessarily mean that it will introduce a change in the trend.
One of the first commenters on the Climate Audit blog said that if the station had a way to measure CO2 we would likely see a large daily change, presumably due to its location in a parking lot. While it’s true that we would see a diurnal signal, it’s source would not be the automobiles in the parking lot. Let’s have a look-see at the (very out of date) satellite image. They circled nicely in orange the location of the surface station. My office, in case you were wondering, is on the top floor of the north “arm” of the building directly to the north of the station, and “my” window faces south. Yup, I can see the station from my desk. This building is called the Physics and Atmospheric Sciences Building (hereafter PAS). Notice that there is a road to the north of PAS, 4th St., and a road to the south of the station Lowell St. To the east of the X-shaped building (one of the math buildings) is another street (unnamed in the photo). But notice that the parking lot does not connect to any of the streets! If you want to actually park in this lot, you need to drive on the sidewalk. This is not a public parking lot. The lot is hardly used. The cars and trucks seen in the (at least 3 year old) satellite image are quite possibly the same as the ones that I can see right now.
Let’s go back to the issue of the location of the site, as if we ever left that topic. It’s in an asphalt parking lot. Directly to the north is an area of grass. The logical question that springs to mind is whether it would be better to have the station situated on the grass rather than the asphalt. I’m not sure if any of you have been to Tucson, or anywhere else in the Southwest, but there isn’t a lot of natural grass. The grasses we do have are very scrubby, not green, and do not look like the nicely manicured area seen in the photos. The emissivity of the asphault is higher than that of grass. That’s why it’s hotter when you stand over the asphault compared to a grassy area. However, the native rocky terrain of the Southwest also has a high emissivity. [I tried to find a plot of the spectral emissivity of dry soil, but couldn't locate one quickly.] I would posit that the dry soil has spectral characteristics more closely related to the asphalt than the grass.
Located one block east of the station is a “power plant”. This is a totally worthless observation. Yes, it does produce quite a lot of heat. But so does the rest of the city! Is it any warmer at the station because of the location of the “power plant”? Absolutely not.
However, there are a few gems hidden in that link. In the caption to that image, it says that the station is “ringed with 4-10 story buildings.” Granted, there is at least one building 10 stories tall nearby, seen best in tucson looking NW2. The building I’m in, directly to the north, is 4 stories. The buildings to the south and southwest are also around 4 stories. The building to the east is, at most, 7 stories tall. Here’s a tip for estimating the size of buildings… count the windows! And then we get “The site is very loud” as if the loudness of a site mattered at all.
[Added August 17: Several commenters have pointed out that I misunderstood the "4-10 story buildings" comment, and it appears I have. One also points out that it made me look like a "total ass". While I agree it makes me look somewhat silly for not reading thoroughly enough, I hardly agree it makes me look like this.]
Anyway, how does any of this change the temperature readings. Let’s compare the temperature readings from this station and those taken at the airport. Both data sets have the same lowpass filter applied.
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The black curve is the temperature data taken at the airport, and the blue data from the USHCN station at UA. The USHCN data actually extend back until the late 1800s, but the other time series does not. The airport site did move from the downtown airport (no longer in existance) to the current airport, but I’d be hard-pressed to tell you when that occured by just looking at the data. The airport is located at the extreme south side of Tucson. The USHCN data set plotted is their temperature corrected for the urban heat island effect.
We can see that the USHCN data has a positive bias when compared to the airport data. However, this does not necessarily mean that it is wrong. It is entirely possible that the temperature difference seen is natural, possibly due to elevation differences, or other means. But the two curves follow the same patterns over long time scales. I would argue that the changes in temperature seen are not due to the location of the USHCN surface station because the airport station is not located in a parking lot.
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16 Responses to “Tucson USHCN Weather Station”
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What does the raw data for the USHCN look like, and why does it end in 2000? Someone claimed it moved to present site in 2001.
You said: “But notice that the parking lot does not connect to any of the streets! If you want to actually park in this lot, you need to drive on the sidewalk. This is not a public parking lot. The lot is hardly used. The cars and trucks seen in the (at least 3 year old) satellite image are quite possibly the same as the ones that I can see right now.”
Looking at the photo, I count 8 vehicles from today’s price of about $15K to $30K. ..so let’s estimate about $160K of vehicles. Are these pictures of the site old or is this not a public parking lot, but one used by the university and still being used?
The raw data from here only goes until December 2002. I don’t know why that is. The urban heat island effect removed data only goes until December 2000. Again, I don’t know why. I downloaded the data yesterday.
Below I’ve plotted the raw temperature and the urban heat island effect removed temperature. I’ve still applied a lowpass filter to get rid of the yearly cycle.
This particular lot is classified as a
misc lot. I don’t know what that means. I’ll check when I leave work if there are any signs. I thought I took out that part about the cars not moving in at least 3 years. But the eastern most car in both the satellite image (old) and the ones taken recently is red. That obviously doesn’t prove anything. My point is that this particular lot doesn’t get a lot of use.
Thanks for posting on this topic. I think it is important for some of the people who operating these stations to speak out, where possible, about what Mr. Watts is attempting.
A question: Mr. Watts and Mr. McIntyre often refer to stations like Tucson’s as being “out of compliance” with USHCN “guidelines” (or some such terminology). But when I glanced at these guidelines I saw a five tier rating system (if I remember this all correctly). So, is there any sense that your station is “out of compliance” with some set of standards? Or just not rated as highly as it might be if, say, it was set somewhere else.
I don’t actually run the station. I can just see it from my office. I don’t know what sort of criteria are used for station placement. I can put you in contact with the person who is responsible for the site and you can ask him. Just post a reply and I’ll email you.
But a major point that I was going to blog about, but a waskly wabbit beat me to it, is “that the ONLY stations which contribute to the overall trend [in the GISSTEMP] are the RURAL stations.” The UofA Tucson station will not contribute to the overall trend because of the way they adjust for the urban heat island effect.
“Just because the station is located in a hot spot means it will add a positive bias, but it does not necessarily mean that it will introduce a change in the trend.”
okay, but are there not guidelines for where you put temperature measuring stations ? Presumably it is a bad thing to do things that are against the guidelines, like putting your measuring stations in hot spots ?
The argument about trend is interesting, and one wonders how long the asphalt has been there; clearly moving the measuring equipment to a site with asphalt could introduce a spurious trend.
“It is entirely possible that the temperature difference seen is natural, possibly due to …”
Wouldn’t it be better to do the experiment right ? I don’t think you know what the effect of having the sensor above asphalt is; yet you are arguing “that the changes in temperature seen are not due to the location of the USHCN surface station …”
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Please put me in touch with the person responsible for the site. Also, I would like to quote some of your remarks above (eventually).
If the site had in the past not been on tarmac
then its temperature would have been lower and
the tarmac siting will now be giving a false picture of the temperature rise.
I have found that when such a surface is wet it is cooled to the same temperature as surrounding grassy areas.
I don’t suppose it rains enough in Tucson for
you to do a plot of rainy day temperatures only.
But this should give a better indication of the true temperature rise
Which version of the Tucson Airport temperature data did you download?
While GISS attempts to adjust to rural sites in the US, other gridcell composites (CRU, NOAA) appear to use unadjusted data and GISS uses unadjusted data outside the US. GISS also has a substantial error in many US series for 2000 and after and have just (yesterday) overwritten all their USHCN data.
[Response: I used data from the NCDC, Tucson International Airport Coop ID 028820.]
This link leads to a menu - I presume that you used the DS3220 version ?? It has a price tag of $40. Could you please email me a copy of the version that you used so that I can reconcile it to other versions. Thanks.
[Response: Emailed as requested.]
The “4-10 story buildings” note means that there are buildings ranging from 4 to 10 stories tall, not 4 buildings 10 stories tall.
It’s good that you removed the silly statement about the same cars being there as 3 yrs ago, since the white one in the recent photo appears to be a 2007 model year Honda Civic coupe.
The “ringed with 4-10 story buildings” statement does not imply there are 4 buildings that are 10 stories each - it means there are buildings which are between 4 and 10 stories “ringing” the site. It was a simple error in reading comprehension on your part, but it would have been nice if a comrade of yours had pointed this out so that you could’ve removed your condescending discussion of the issue (”Here’s a tip for estimating the size of buildings… count the windows!”). Instead, you’ve got a paragraph that has been sitting there unnoticed for about 4 weeks now, making you look like a total ass.
Yes. It was my mistake. It’s been fixed.
I like your style even though you are probably a liberal. The main thing is to be in favor of truth and of making things better understood. The hoi polloi Steve M camp followers will try to mess with you, but don’t let them scare you. I can flame their cherry asses if they mess with you.
[Response: I most identify with the libertarians. In general, I'm a social liberal and a fiscal conservative, which means that everyone hates me. Oh, and Steve M.'s camp has already been here. But the thought of flaming cherry asses will keep me up at night.
]
Kiss, kiss. Sleep tight.
One thing you might consider about asphalt is that it does tend to change in ways that are fundamentally different than a site surrounded by normal ground cover. Take a look at freshly tarred asphalt. It’s a very dark black. If you would have looked at the same lot right before the crew came in, you would see it has a somewhat different (and lighter) color. No doubt you could correct for the effect but I doubt anybody actually does it because… you’re not supposed to be putting your site in the middle of a parking lot so who would think to apply the correction? Where would you get the data of when/how often they redid the parking lot?
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