Eric Berger writes (excerpt below) at the Houston Chronicle “SciGuy” blog about the wicked hot record breaking temperatures people were getting in Houston on their iPhones. Turns out the whole issue is over station siting. While he located the station, doing some further investigation, I’ve got shots of the actual equipment and error analysis.
The curious case of why your iPhone reports crazy hot temperatures in Houston
Eric Berger – Houston Chronicle
Over the last several days I have seen a lot of reports on Twitter and elsewhere about very warm temperatures in Houston, a few degrees warmer than those being reported by the National Weather Service. They have come from people with iPhones.
For example the “Houston” location on your iPhone’s generic weather app reported a temperature of 109 degrees yesterday at 2:50 p.m. when in fact the official reading at Bush Intercontinental Airport at the time was 105.
Indeed no major weather station in the Houston area reported such a high temperature at the time. It got TechBlog‘s Dwight Silverman and I wondering what was going on. Where was Apple pulling this data from?
We started speculating on Twitter and didn’t begin to solve the mystery until Travis Tubbs chimed in.
After that Dwight archived the conversation in Storify, and it appears below (above), starting with Dwight’s initial tweet about the temperature getting back to a record 109 degrees Monday. (Officially, it didn’t. Monday’s high topped out at 107.)
…
So the mystery was solved, sort of. Apple gets its weather data from Yahoo!, which in turn gets it from The Weather Channel.
And for whatever reason the default iPhone weather data point is the Houston/Hermann Medical Center weather location. Whatever that is. It’s not an official National Weather Service site.
Full story here
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No, it isn’t an official NOAA station, it serves the heliport. But it is a MADIS station, registered with NOAA, and used for other purposes such as MESONET.
Te lat/lon of the station is listed at the Gladstone CWOP metadata site as 29.7140 -95.3950 and that bring up this image on Google Earth:
Clearly the lat/lon places it on the roof in the helipad, but even at max zoom, I can’t make out any weather station. I was however able to see a helicopter on the pad and a windsock on the Bing Maps image and I theorized the weather station might share the mast with the windsock.
Fortunately, certain people like to photograph helicopters in action, and I was able to locate this shot from a photographer’s FLICKR collection that showed the station:
If you enlarge the photo, you’ll see the anemometer and wind vane, and what looks like a gill shield for the thermometer, though I can’t be certain. Even if it isn’t, the thermometer will be nearby to serve the helipad.
What I found most interesting though was the temperature analysis provided by the NOAA MADIS website. Apparently the problems with this station are well known.
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Temperature
| 24 hours | Day time | Night time | |
| Average temperature error | -2.7 °F | -4.9 °F | -0.5 °F |
| Error standard deviation | 3.3 °F | 3.4 °F | 0.9 °F |
| Worst average temperature error | -3.8 °F | -6.5 °F | -1.0 °F |
| Worst standard deviation | 4.3 °F | 6.2 °F | 1.5 °F |
NOTE: If the error above is POSITIVE, then it means that the analysis temperature is HIGHER than the reported temperature. This means that your sensor is reading COLDER than expected
================================================================
Worst daytime temperature error of 6.5F …wow.
A look at their graph is also telling:
As is the note below it (red color theirs):
Your readings indicate a solar heating problem. This means that the sun can shine directly onto the temperature sensor (or it’s housing) and increase the temperature recorded significantly. This is often caused by the lack of a radiation shield, or the sensor is poorly sited. For information on radiation shields, see CWOP Radiation Shields, and information on siting, see CWOP Station Guide.
With error magnitudes like that, perhaps the Weather Channel Might want to use a different source of station data for reporting Houston temperatures.
Again, siting is the issue. The station might be fine for reporting helipad conditions, and it might very well be that hot of the roof of that building. Knowing that accurately is important for the safety of the helicrew, especially on days of high humidity and high density altitude that sap rotor lift efficiency.
But it also underscore a point I’ve made time and again: rooftops aren’t a representaive location for climate monitoring, as we’ve seen a couple of days ago with this rooftop GHCN station # 2076548 photographed in Tampico, Mexico:
As we’ve seen time and again, GHCN stations are often sited at airports, and while runway and helipad conditions are imperative to know, especially when they differ from surrounding ambient, such stations sited in odd places don’t translate well for other applications, be it long term climate monitoring or a simple iPhone app for infotainment purposes.
If people reading iPhones can spot such problems and know the temperature data isn’t valid, and a citizen run CWOP program can use MADIS analysis of the data sight unseen and note it’s FUBAR, why can’t our meteorological experts at The Weather Channel figure it out?
It has been what I call “an air conditioned summer” here in Greece at the Corinth area. I have a plot of temperatures, and they never went over 36C . Most of the time around 32C with fair breezes blowing, Very pleasant, On hot years we have hit 40C and once 42C.
Theo, I’m not sure what you mean by “a hole”, but given the general lack of any topography in this coastal plain (old sea bed, by the way), it’s hard to characterize Houston as being in a hole. The elevation in Houston is around 50 feet above MSL, and varies only by a few feet throughout the area (discounting the cuts by creeks and bayous). And it’s ~50 miles to the Gulf of Mexico, so there is a very, very shallow decline in elevation. Thus, rain runoff is very slow, and a foot or two difference in elevation can determine whether an area floods. It’s so flat, that the Soap Box Derby has to commandeer highway overpasses for their competitions.
“Marcos says:
August 31, 2011 at 12:06 am
Maybe we should start a campaign to have city’s ‘official’ weather stations moved away from airports and rooftops and into their main parks to help (somewhat) from poor siting and UHI. For Houston that would mean using Herman Park instead of Intercontinental Airport. IIRC, NYC already uses the Central Park reading”
Not a bad idea, but instead of Hermann Park, why not Memorial Park? Granted it’s been a few years since I was last in Houston, but I recall Memorial being more “natural” than Hermann. Or as natural as an urban park can be.
I used to read Eric’s blog, but I don’t anymore. He is a completely biased AGW advocate although he claims he is undecided. (He’s lying.) As with most watermellons, he’s also a misanthrope.
GeneDoc says:
August 31, 2011 at 10:40 am
OK, “hole” was too much. It is a short walk from downtown to sea level. Also, the metropolitan area is not strung along a coast as Miami is. It stretches northwest, north, and northeast, preventing it from getting the benefit of the sea breeze.
Why can’t our meteorological experts at The Weather Channel figure it out?
Because they don’t want?
The NWS does a much better job.
Memorial Park would be a much better site. It’s much larger, mostly forested, and probably would shield the site from UHI somewhat, but not entirely. I’d probably put it near one of the baseball or soccer fields.
As far as rainfall runoff goes (my day job), Houston is pretty darn flat. It’s hard to design drainage systems, because we get so much rain and there’s nowhere to put it. That, combined with the clay soils that don’t soak anything up, means that we have to dig huge holes to offset increases in runoff from development (a good thing to do, but expensive), and ofttimes we have to pump the water out of the holes, because it’s cheaper than digging a much shallower hole that would gravity drain (and you can’t run an 8′ deep storm sewer system into a 3′ deep pond, anyway).
This is ridiculous. An entire city 50 miles wide and 50 miles long being read from a single thermomenter on top of a hospital not 2 miles from my old apartment. That area is nearly treeless, completely waterless (well, there is a nearby park, but it’s nothing compared to the East side which is covered in trees and has the Ship Channel going all the way up to downtown), has horrific traffic, and is smack dab in downtown’s heat island.
Next to check: Waco TX
Sometimes it seems they break a record a day, every day (for past year, winter AND summer).
I have zero evidence but the climate reporting looks wacko in Waco.
“Only two things are infinite, the universe and human stupidity, and I’m not sure about the former.” – Einstein.