In an earlier posting, I had suggested doing a simple airport Heat Island audit via the expedient of Wunderground.
Then time passes, and over on WUWT, the topic of airports came up again. This was in a thread about the Solomon Islands where the temperature was being measured at an airport:
It was a nice warm sunny afternoon, so I posted a link to the above article, and some temperatures. They showed the airport and the area just down wind a bit warmer than the spaces on either side.
This morning, overcast and cool, makes a nice comparison.
San Jose Airport (SJC) – 62F 7:53 am
Santa Clara (95050) – 61.6 F 8:14 am
Berryessa (Milpitas) – 61.1 8:14 am
Willowglen (95126) – 62.1 8:08 am
Winds “calm” to zero all around. (The term in parens is the search term given to Wundertground to find that station)
At the bottom of the page at Wunderground, they give a table of stations in the area. I notice this one.
The map on that ASOS page shows the SJC airport. Hmmm….
So how can the airport be both 1 F and 2 F hotter than the surroundings at the same time? I smell a “Dig Here!”…
The ASOS stations are used for “QA” on all the others in part of the USHCN QA process as published. And here it is the one that stands out as a degree warmer than pretty much all the others in the list. (The exceptions being a unit on Mount Allison reading 72 F (inside somewhere having coffee?), RAWS CDF portable on Mt. Hamilton 66F, and El Camino – Wolf at 65.1 F ( Looks to be a home near a shopping mall).
The history chart for Mt. Allison shows a fairly steady 70-ish range when you look at the History for KCAMILPI6. Looks very much like a sensor inside somewhere to me (or stuck on a window?)
The portable Mt. Hamilton RAWS record shows a wobble between 65 F and 70F all night long for the History for MTR098. I’d guess it was in an unheated garage all night. Kept stable by the attached building?
The El Camino / Wolf site has a nice web page with neat graphs. Clearly someone “into” weather, but odd that it is running a bit hotter than the surroundings and someone that interested would not notice. See:
Why mention these? Because all the others in the area are very close in range and indicating 61.x F (with some showing lower as they are near colder places, like History for MPEAC1 on Calaveras Road; out in the country toward a reservoir) that is showing 57F. A different air basin and behind a mountain or two. Looks like an opportunity to do an easy UHI study here too. (Dig Dig!)
We have a fairly clear example, though only two times so far, of the SJC airport being hotter, and the ASOS being even hotter, than the surrounding UHI infested area that is itself warmer than the ‘countryside’ nearby.
The Context Map
So for the SJC airport to be reading 62F implies that either they round up (where IS that .x anyway?…) or that it’s a touch warmer than the surroundings. The “nearby airports” box lists 4 airports (one of them SJC) All reported at very similar times. Moffett NAS (Naval Air Station) is also at 62 F, while Reid Hillview (small private planes) is at 61F as is Palo Alto (small private planes but on the other side of Moffett NAS from SJC.
You can find Moffett field near the water in the upper left. Palo Alto airport is just a bit more up the bay toward that creek entering. Then follow 101 to the right and you reach SJC. More or less north is Milpitas, and if you had continued on that line from Moffett to SJC you will see Reid airport. Willow Glen is that pod of residential area just to the left of downtown San Jose and south of SJC.
OK, so we have 2 very large “international” scale jet ports running 1 F higher than the two private prop plane airports near them. Palo Alto is right on the bay (as is Moffett) and ought to be substantially the same if not identical to Moffett. SJC is just down 101 a few miles and is “near” the bay though not on it. Barryessa is a bit further on toward the hills in the east on a more or less northern path, with Santa Clara snuggled up right next to SJC on the west side (and so a few miles east of Moffett also). Reid Hillview Airport is south east of SJC and south of Barryessa (though a touch east of south of Barryessa, a bit more on a line from Moffett through SJC).
Looking at all this, under a dead calm overcast sky where everything ought to be the same, it sure looks to me like the two major airports are about 1 F hotter than their surrounds. I’m also a bit worried that this looks like it could be a rounding artifact. I’d hate to think that “global warming” came down to “rounding error” as airports round their temperatures… But those two ‘puddle jumper’ airports are also rounded, and they say 61 F.
As a first cut airport audit, I think this system will work. I’ll be watching those stations through the day and seeing if, as the sun comes out, we get some added separation between the stations.
Yesterday. All My Temperatures Seemed So Far Away..
FWIW, the temps yesterday evening were:
SJC (via airport code): 74 F
Barryessa (Milpitas): 72F
Willow Glen (95126) 76.3 F (though this was “north willow glen”)
Santa Clara (95050) 71.9 F
There was a slight wind to the south, toward North Willow Glen, from the airport. ALso, SJC was reported as 43 minutes earlier TOD, so might have had a TOD bias). Times for the other stations were around 8:35 pm.
What I put in the posting on WUWT in comments was:
Using SJC and 95050 that gets a Santa Clara station (San Jose Airport has one side basically against Santa Clara) gives SJC at 74 F with Santa Clara at 71.9 F (Santa Clara is measured 43 minutes after SJC, so there is a chance of a TOD error). Barryessa, California, on the other side has 72 F and the same TOD as Santa Clara.
North Willow Glen, just south of the airport past a couple of freeways has 76.3 at the same 8:35 pm time as Santa Clara but SJC has a S wind indicate with “calm”, so my guess would be that we are getting our usual evening ‘cool’ drift in from the bay sending the SJC heat island breeze toward North WIllow Glen. Sure, it could be plain old UHI added in from downtown San Jose (right on the other side of the airport…)
We generally get a slow southernly drift to the air, so that Willowglen reading could be an artifact of warm airport air drifting in, or just that the particular thermometer runs a bit warm. I’ll be looking around that area for comparison stations to try to sort that bit out.
In any case, I think there is enough here to make large commercial airport temperatures demonstrably suspect in the 1 F range. AND to do a specific ASOS vs nearby audit.
For those wanting to check the temperatures themselves, here are the links to the target sites:
If you see anything interesting, please put the facts (temp, time of day, etc.) in a comment. As the overcast breaks up into ‘fluffy clouds’ today I’d expect to see some significant bouncing around as some places are under cloud and others under sun, then stabilization late in the afternoon under clear skys. We’ll see…
So is this the ASOS?
Scrolling around on Google Earth, this was the only thing that looked like it had a tower and some gear boxes around it. So is this the ASOS? It’s near the north end of the runway, off to the side, about where folks put thermometers at airports.
Looks kind of hot and forbidding to me…