UPDATE: A second nearby station has been located, also showing a lower high temperature. See below.
First let me say that the Carefree, AZ Skypark airport, and the airport observer have not done anything wrong. I commend them for their service as a NOAA Cooperative Observer, a volunteer job done for the good of the country. The station was installed by NOAA/NWS Phoenix personnel and it is their responsibility for things like this difference in daytime high temperatures, such as I discovered below.
But after looking at the ground photos of the NOAA climate station, I have only one word to describe it: FUBAR
First some review; read my essay on what I discovered from metadata investigation of the station: A Carefree Record High Temperature in Arizona
I showed a map with all the new records plotted. But, there was a curious red dot record high temperature “anomaly” on it, 109°F in Carefree, AZ on July 8th, the only one for that entire week in the entire state.
From that essay, this image shows the station is surrounded by Asphalt tarmac:
click to enlarge imageAnd thanks to WUWT reader Glen Sheldon, we have photos from the ground (on 07/13/2010) that confirm what I suspected; the station temperature sensor is mounted directly over asphalt at roof level, both of which contribute to anomalously high temperature readings.
I don’t know how often the outdoor fireplace is used, but when it is, I’m sure it helps keep the cold away.
Seasoned surfacestation.org volunteers have seen worse sitings, but this one has severe siting violations worth noting:
- NOAA 100 foot rule ? – pfft!
- Over asphalt plus physically on a building – rates a CRN5 “worst of the worst”
- Wind sheltered on one side due to the beam – southerly wind, not so much
- At roof level – will pick up waste heat from the building when wind blows across the flat roof
- Incorrect height – WMO/NOAA standard is 1.5 meters – this is twice that
- Other heat sources nearby, Pepsi machine – waste heat like an A/C unit, nearby outdoor fireplace
- Nearby tree – listed as an obstruction in the NCDC metadata
- Nearby automobile parking – radiator inward, under the sensor
In case anybody wonders about NOAA rooftop stations that give erroneous high temperature readings, this one should provide an excellent primer because NOAA closed it in 1999 due to similar siting problems.
How not to measure temperature, part 48. NOAA cites errors with Baltimore’s Rooftop USHCN Station
NOAA then wrote an internal technical competency manual on it advising that it is not good practice. I guess WSO Phoenix never read it.
Reference: NOAA Professional Competency Unit 6 (PCU6) manual (PDF)
But the thing that really hit me was the data they compiled, comparing to other nearby stations, and thus proving the case for rooftop bias with this station:
They cite the table with:
The table to its right summarizes a comparison of 12 months of overlapping data that was collected on the rooftop and at the new relocated site (for data continuity), relocated several blocks away at ground level with other nearby standard, ground based stations. A combination of the rooftop and downtown urban siting explain the regular occurrence of extremely warm temperatures. Compared to nearby ground-level instruments and nearby airports and surrounding COOPs, it is clear that a strong warm bias exists, partially because of the rooftop location.
Maximum and minimum temperatures are elevated, especially in the summer. The number of 80 plus minimum temperatures during the one-year of data overlap was 13 on the roof and zero at three surrounding LCD airports, the close by ground-based inner Baltimore harbor site, and all 10 COOPs in the same NCDC climate zone. Eighty-degree minimum are luckily, an extremely rare occurrence in the mid-Atlantic region at standard ground-based stations, urban or otherwise. Temperatures can be elevated on roofs due to the higher solar radiation absorption and re-radiation associated with many roof surfaces including black tar, shingles, stone, and metal. During the colder months, ongoing upward heat transfer through the roof from the heated interior of the building also can contribute to the warm bias although stronger winter winds tend to create better mixing and minimize this impact.
The table shows that the rooftop station has Tmax >90°F more than twice as often as other stations and a Tmax >100°F 13 times where no nearby station achieved it. Similarly we have this station recording a Tmin >80°F where no other stations did.
But here we still find stations just like this in NOAA’s climate monitoring network 11 years after Baltimore’s station was closed for the same reason.
The Carefree Skypark COOP should either be closed, go to rain only, or relocated, as it is not used for airport operations, only for NOAA climate reporting. The station is polluting the climate record. NOAA needs to determine how long this has been going on and if the record is even worth keeping. I doubt it is. Also of note, this station is used to adjust other stations nearby in the “homogenization” process, further polluting the climate record.
I’m looking into doing some longer term data comparisons between the Carefree, AZ AP station and the nearby private observer station. If I’m able to obtaining the data, we’ll have a look in a future post.
Again I close with what I opened with:
The Carefree, AZ Skypark airport, and the airport observer have not done anything wrong. I commend them for their service as a NOAA Cooperative Observer, a volunteer job done for the good of the country. The station was installed by NOAA/NWS Phoenix personnel and it is their responsibility.
UPDATE: A second nearby station has been located, a MESONET station, and it’s high temperature on that day was also considerably lower, 4°F lower than the airport.
Data follows.
08 Jul 7:00 pm 93 49 22 NE 5G13 33 11% OK
08 Jul 6:48 pm % 0.00 OK
08 Jul 6:45 pm 93 49 22 NE 5G15 33 8% OK
08 Jul 6:33 pm % 0.00 OK
08 Jul 6:30 pm 95 49 21 E 4G14 93 20% OK
08 Jul 6:18 pm % 0.00 OK
08 Jul 6:15 pm 99 45 16 E 3G08 93 17% OK
08 Jul 6:03 pm % 0.00 OK
08 Jul 6:00 pm 100 42 14 SW 3G04 99 16% OK
08 Jul 5:48 pm % 0.00 OK
08 Jul 5:45 pm 100 42 14 SW 3G08 99 14% OK
08 Jul 5:33 pm % 0.00 OK
08 Jul 5:30 pm 100 44 15 NNW 3G08 126 16% OK
08 Jul 5:18 pm % 0.00 OK
08 Jul 5:15 pm 99 45 16 SW 4G10 126 15% OK
08 Jul 5:03 pm % 0.00 OK
08 Jul 5:00 pm 101 47 16 SSW 4G09 571 63% OK
08 Jul 4:48 pm % 0.00 OK
08 Jul 4:45 pm 103 45 14 SW 4G15 571 59% OK
08 Jul 4:33 pm % 0.00 OK
08 Jul 4:30 pm 103 38 11 ENE 4G08 659 64% OK
08 Jul 4:18 pm % 0.00 OK
08 Jul 4:15 pm 103 38 11 ENE 3G08 659 60% OK
08 Jul 4:03 pm % 0.00 OK
08 Jul 4:00 pm 100 44 15 SSW 3G13 714 62% OK
08 Jul 3:48 pm % 0.00 OK
08 Jul 3:45 pm 104 44 13 SW 2G08 714 59% OK
08 Jul 3:33 pm % 0.00 OK
08 Jul 3:30 pm 103 43 13 SW 4G14 802 64% OK
08 Jul 3:18 pm % 0.00 OK
08 Jul 3:15 pm 105 42 12 SSW 6G15 802 62% OK
08 Jul 3:03 pm % 0.00 OK
08 Jul 3:00 pm 101 41 13 SE 6G14 852 63% OK
08 Jul 2:48 pm % 0.00 OK
08 Jul 2:45 pm 102 47 16 S 5G10 852 62% OK
08 Jul 2:33 pm % 0.00 OK
08 Jul 2:30 pm 100 42 14 S 5G13 522 37% OK
08 Jul 2:18 pm % 0.00 OK
08 Jul 2:15 pm 102 44 14 SSE 5G15 522 36% OK
08 Jul 2:03 pm % 0.00 OK
08 Jul 2:00 pm 100 46 16 SE 2G14 923 63% OK
08 Jul 1:48 pm % 0.00 OK
08 Jul 1:45 pm 101 48 17 S 2G15 923 62% OK
08 Jul 1:33 pm % 0.00 OK
08 Jul 1:30 pm 100 46 16 SSE 6G17 945 63% OK
08 Jul 1:18 pm % 0.00 OK
08 Jul 1:15 pm 99 45 16 SE 4G19 945 63% OK
08 Jul 1:03 pm % 0.00 OK
08 Jul 1:00 pm 99 45 16 ESE 4G10 951 63% OK
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It would be useful to also have pictures of the nearby private station for comparison, assuming that this can be done while respecting the privacy of the owner. The commentary assumes that this station is perfectly sited.
No it doesn’t. The commentary merely says that two nearby stations give wildly different results.
It is a red herring to worry if those other sites are poor if they are not used officially.
The onus is on NOAA to site their stations properly.
Anthony,
It’s a bit late, but then, I just got here;
In your reply to John C at 9:40 AM, your link is messed up. Misspelling,
“www.surfacesattions.org”
Duck Xing