How airports like BWI help set outlier high temperature records

Mark Johnson, Chief Meteorologist of WEWS in Cleveland writes:

A friend of mine, Justin Berk, a local TV Met in Baltimore, MD had this story to tell today:

“There’s something fishy going on at BWI (Baltimore International Airport),” he says. Hourly obs at BWI airport (April 12, 2012) never went higher than 59 degrees.

(See the obs from BWI below – Anthony)

But, he noticed the official high temperature was listed as 62 degrees.
“There’s no way a jump of 3-4 degrees occurred and then fell back down between obs,” he added. Why the discrepancy? Justin called the local NWS office.

For a brief 10 minutes, the steady NW wind that persisted all day at BWI shifted to a westerly direction. That allowed the  HEAT from the nearby runway to provide a quick 3 degree warm-up between hourly obs. Once the winds shifted back to a NW direction, the temperature fell back to 59 degrees.

The NWS employee concurred that the extra warmth came from the runway.
Global Warming is real (thanks to poorly-sighted thermometers)! This is the second time Justin observed a false high temperature reading this week at BWI.

========================================================

I followed up on this, and his story checks out.

First the table of high/low for the day from BWI:

Source: http://www.nws.noaa.gov/climate/getclimate.php?wfo=lwx

And here are the hourly observations for the day from the BWI airport ASOS station:

Source: http://www.nws.noaa.gov/obhistory/KBWI.html (downloaded at 2AM EST 4/13)

Here in what the BWI ASOS station looks like along with compass points added:

Source: http://binged.it/HC0WPG

And here is a view looking to the west:

Source: http://binged.it/HFgGmM

Seems an open and shut case. This is not the first issue with weather observations at BWI, they also have issues with measuring snow, and I reported here:

BWI snow record rescinded: Another reason why airports aren’t the best place to measure climate data.

=============================================================

UPDATE: 3PM PST 4/13/12 The Capital Weather Gang tries to avoid the siting issue with an alternate explanation. This from comments.

I’ve posted a different perspective on this at washingtonpost.com: The case of the curious temperature spike at BWI airport: asphalt or the sun?

REPLY: Anything to avoid UHI it seems with you guys. As for sun/wind debate. It could very well be both. Asphalt absorbs sunlight pretty well. More sun coupled with a shift of wind to the asphalt area can easily make a quick 3 degree jump. Sunlight by itself on grass, not so much. You didn’t mention albedo in your article so I’ll assume you don’t understand it.

Bottom line – airports are a poor place for temperature observations used for climate purposes, as they aren’t representative and are very dynamic with land use changes, and, see this detailed analysis.

http://wattsupwiththat.com/2012/04/13/warming-in-the-ushcn-is-mainly-an-artifact-of-adjustments/

Airports are part of USHCN.

– Anthony

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82 Responses to How airports like BWI help set outlier high temperature records

  1. omnologos says:

    UHI, as it’s well known, is a phenomenon that happens locally everywhere but, as if by magic, globally nowhere.

  2. You sure do put a lot of effort into justifying USA as the worlds heaviest carbon poluter ;) Respect!

  3. Lew Skannen says:

    Stories like this are just so mundane and lacking in glamour that the MSM will never pick up on them. There is no looming disaster and no villain, no polar bear and no photogenic hero, just the steady constant corruption of data.
    Well done Anthony for taking the trouble of picking up on it but you can be sure few people outside WUWT will ever know.
    They will just read that another heat record has been broken somewhere…

  4. Rob says:

    I’ve noticed this at other locations as well. There is big discontinuity issue when NWS shifted from Cotton Region Shelters to MMTS, ASOS etc.

  5. Pete Olson says:

    ‘poorly sited’, not ‘sighted’

  6. Disputin says:

    Just goes to show what Anthony has said before – airport weather observations are collected for the use of aircraft using the runways, not as climatological records, for which they are nearly useless.

  7. Capell says:

    Is there no way of capturing data from the Davis WeatherLink system? The people who go to the expense of buying these stations (many of them private individuals) are likely to take care with the siting of the sensors, this network might be quite reliable.

  8. michael hart says:

    The scientist in me immediately starts think about new experiments that might be done to improve the data at airports. Given the high aspect-ratio of the runway and the flight paths, it would be interesting to have thermometers located both at the side of, and and at the ends of runways. The effect of prevailing wind might then appear to be greater.

    Also, think of all that lovely heat [and CO2 and water!] that the jets are cranking out at take off: probably biased towards the starting end of the runway. Has anybody done these relatively straight forward experiments?

  9. thisisnotgoodtogo says:

    It’s what they\ve telling us would happen…runway global warming

  10. Eric Dailey says:

    Great post, thanks. Good work by the local Mets.
    This house of cards will fall soon but in spite of journalism and not because of it. It’s time to wake up and realize we are being deliberately deceived by the press establishment and not just about CAGW.

  11. thisisnotgoodtogo says:

    It’s what they’ve been telling us would happen…runway global warming

  12. The real irony, is that if the climate “scientists” had been real scientists and a) looked at the data, b)admitted to themselves (or c) stopped lying) then they would have made it known that they needed a top notch metereological data collection system and that it was inappropriate in “such an important issue” to use fifth rate sites to measure data.

    But these guys are not real scientists. They are quite happy to use slip-shod data where it suits their purposes, and as I said, the real irony is that a pittance has been spent on the real area of need: ACCURATE TEMPERATURE MONITORING SITES and as a result of a woeful lack of a few billions on temperature monitoring, the world is spending trillions on unneeded and unwanted and economically harmful measures which will probably cost us all many more trillions in lost economic output.

    I can only liken it to a diamond dealer buying a supermarket set of scales … no that would at worst be a few percent loss. It’s more like they built a massive tower block based on a geological survey done by schoolkids using “eye spy minerals”.

  13. Tom Harley says:

    Nothing to see here…move along. BoM in Australia have most of their stations next to runways, previously favoring post offices. How else can they keep up their #pocket-lining from the government.

  14. Andrew says:

    Brings a whole new meaning to the term ‘Jet Stream’.

    But seriously, since jet-fuelled thermometer readings artificially increase the range of the data readings at a given site, in a given time period, it is not hard to see how the inappropriate use of ‘linear interpolation’ for filling-in gaps in the surface temperature record (eg. at neighbouring sites) over time can compound the original (UHI) bias by introducing a systemic source of warming bias into the wider temperature record.

    And as air traffic increases through time, this systemic warming bias effectively becomes self-amplifying… a bit like a virus initiating infection in one cell, replicating then releasing progeny viruses to infect other cells.

    Once again, “linear interpolation” of this nature is really extrapolation by another name… or to put it another way, a statistical method for transforming science into science fiction.

  15. KnR says:

    Airport weather stations are intended to provide data for flights and out of the airport , so such features are not a problem for there intended purpose . Expect that now these stations data is being used for 101 things with great claims being made to its precision and how well its represents the local area.
    The reality is there used, not because there a good idea, but because they exist and save actual having to set up another one that would provide valid data. They are the duck tape of weather measurement , a fair temp fix that is easy to use but is actual in no way a good nor permanent fix to the problem.

  16. Steven Mosher says:

    omnologos says:
    April 13, 2012 at 12:24 am (Edit)
    UHI, as it’s well known, is a phenomenon that happens locally everywhere but, as if by magic, globally nowhere.

    #############

    its rather easy to understand
    1. Its a function of windspeed and direction. Note the temperature changed for 10 minutes
    when the wind changed.

    2. Its a function of timing. If that wind change happens at 19:54.. no change to TMAX

    does UHI exist. Yup. DO you get it every hour of every day? nope. conditions have to be right.

    Do you know what they do when they want to study UHI? They look for days when the synoptic conditions are such that you can actually measure it.

    At this place, you nee a westerly wind at the right time of the day.

    Its not a big mystery why UHI is real and why it doesnt show up in the record.

  17. Its not a big mystery why UHI is real and why it doesnt show up in the record

    It does show up in the record. It just doesn’t show up that well when you smear min/max temps over large geographic areas in the method so beloved by climate scientists.

    The data is fine. The problem is the method.

  18. Andrew says:

    RE
    Steven Mosher says:
    @ April 13, 2012 at 2:35 am
    —————
    Nonsense.

    Please address my point (@ 2:27 am) re how inappropriate interpolation results in a self-amplifying and systemic warming bias into the temperature record…

    Are you seriously suggesting that all readings taken at this site, for example, when the wind direction is from the west are culled from the record?

    And what about other sites where a UHI bias may not yet have been identified?

  19. ChristianP says:

    Hello,
    Sorry for my bad English, I am French.

    On the map 2 D, I see the W here :
    http://meteo.besse83.free.fr/imfix/wbaltimore.jpg

    If the soil is very dry with a sparse grass, for the T max of the day with sun, it is warmer that the runway (in a study at Nice aeroport in France (“Topoclimatologie et habitat”, Pierre Carrega), for example, the temperature surface max in september, is 46°C for the runway for 62°C for a sparse grass with soil dry (water reserve in the soil : 9 mm for a maximum 150 mm). The night, the runway stay very much warmer that the sparse grass.

    In your case, also there are some clouds and a wind variability for generate this value without runway, it is not unusual to observe these differences. Here for several stations with and without ventilated radiation shields, it is very common in the natural sites with yours conditions.

    At Baltimore in this site very open for to get a good natural ventilation, there are not a big problem on the T max with a ventilated radiation shield, if the fan is good. This difference is not make by the runway (you can check with an other same station before the runway at the same distance of the runway, for this wind direction. In the Var in France, I like to do this kind of test )

  20. gator69 says:

    Nice. Right between the runways. Jet exhaust and hot pavement. Perfect.

  21. Andrew says:

    And what about southerly winds transporting jet exhaust heat from the adjacent runway (see pic 2)? Or for that matter easterly winds from the (same) adjacent runway?

  22. DavidH says:

    I can’t see what the problem is. If the wind shifted and the thermometer recorded 3 degrees higher in between the reported hourly observations, then isn’t that rightly the maximum for the day? Are we arguing here that observed temperatures should be adjusted according to our preferences? (There’s already one team playing that game.) As long as past brief spikes and dips in temperatures have been faithfully recorded then these 3 degrees shouldn’t be any cause forma concern. Or am I being too optimistic that the dips haven’t been discarded by “the team” and only the spikes kept?

  23. mfo says:

    I’m a bit confused.
    The photo shows the main runway running east/west lying to the north of the weather station. I think that the tarmac area to the south of the weather station is the mid-field cargo complex on which are parked quite a few large vehicles. Please do correct me if I’m wrong

    The Google photo map shows an aircraft waiting to take off at the eastern end of the main runway, with the weather station located just south of the western end of the main runway where the aircraft leave the ground to begin their ascent:
    http://maps.google.com/maps?spn=0.036009,0.046450&t=h&hl=en&ll=39.175361,-76.668332&fc=1

    It seems very odd to locate a weather station just south of that part of the runway from where aircraft are taking off, particularly as they are taking off into the wind which is then being blown back towards the weather station.

    It seems clear there must be a considerable UHI effect at this location. The faa map of the airport is:
    http://aeronav.faa.gov/d-tpp/1204/00804AD.PDF

  24. Espen says:

    DavidH says:
    April 13, 2012 at 3:25 am
    I can’t see what the problem is. If the wind shifted and the thermometer recorded 3 degrees higher in between the reported hourly observations, then isn’t that rightly the maximum for the day?

    Suppose there were nearby construction workers laying new tarmac as the wind shifted, so the spike was 10 degrees higher – still “rightly the maximum”?

    As long as past brief spikes and dips in temperatures have been faithfully recorded then these 3 degrees shouldn’t be any cause forma concern

    The problem is that the new mantra for alarmism-by-press-release is to count the number of new record maxima set.

  25. Andrew says:

    RE
    Andrew says:
    @ April 13, 2012 at 3:22 am

    Correction: sorry, that ought to be “…northerly winds transporting jet exhaust heat from the adjacent runway….”

  26. Roger Caiazza says:

    David H at 3;25AM
    The problem is related to “representativeness”. Our concern is just how much of the observed temperatures are caused by the increase in GHG concentrations. Temperatures that represent or can be used to calculate that effect should not be affected by local conditions which can change irrespective of changes in the atmosphere. As Anthony has been trying to point out, airport measurements poorly represent temperatures to be used for GHG attribution calculations and this example shows definitively that local conditions at airports affect temperature.

    There is another problem illustrated. The new meteorological sensing systems collect one-minute data averages and those data are being used to set the daily maximum values. At some point in the past, the data were collected with manual observations. Clearly there is a much greater change of higher maxima and lower minima now that we have continuous data.

  27. Matthew W says:

    Would the new weather stations with the wind screens have prevented that problem/false reading?

  28. SandyInDerby says:

    Steve Mosher
    are you saying that if it’s windy then the UHI doesn’t exist? In very simple terms surely the heat is spread round over a larger area with a lower increase in temperature. I think of it like a fan blowing on an auto’s radiator the amount of heat (or energy or whatever you want to call it) remains the same in the whole system, its just that different things and volumes are warmer/cooler. If you only measure the temperature of the radiator then you’re mislead, no?

    To my simple mind on windy days UHI is spread further down wind, the windier the day the further down wind it goes and, perhaps, becomes harder to measure.

    Thanks

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  30. Gail Combs says:

    I thought this set of paired temperature data does a bang-up job of showing how airports are rotten for gathering the accurate temperature data

    The city is on the North Carolina/Virgina border and right on the ocean. Not that far from Baltimore (a 230 mile drive). Take a look at the city vs the airport! Norfolk City and

    Norfolk International Airport

    Other Coastal Cities in North Carolina:
    Elisabeth City

    Wilmington NC

    Here is the raw 1856 to current Atlantic Multidecadal Oscillation Amazing how the temperatures follow the Atlantic ocean oscillation as long as the weather station is not sitting at an airport isn’t it?

  31. BarryW says:

    BWI, was originally called Friendship airport and dates from the early 1950′s. It’s expansion has been huge, now having more traffic than Washington National. With all the asphalt and concrete that has been laid, it’s got to have it’s own mini UHI issues. Wiki says that the expansions started in the 70′s. Interesting coincidence.

  32. shrnfr says:

    I really, really like having weather stations at the airport. They provide the information that can be used to have the pilot take off and land their aircraft safely. However, they are only indicative of the “climate” at the airport. To use them for anything else is foolish, but sadly we have many fools among us.

  33. James says:

    Sorry, I’m not buying this. Theres a more logical reason for this. Notices in those obs that the winds were 10 mph gusting to 18. That is PLENTY of wind to mix out that heat coming from that tarmac. This article acts if while the ASOS station had NW winds the tarmac to its west has no/ calm winds. It doesn’t work like that. Those NW winds were blowing over that tarmac and mixing out. So what caused the jump?

    If you have ever looked at a topographical map for the BWI area there is the MD fall line about 3 miles to the west of the airport. Its a fall of 300-600 feet over 2 miles. I’ve noticed even at my house (which is 9 miles away and in a wooded area) that when the wind blows from the west you get an increased jump in temperatures due to downsloping from the fall line. Thats NOT an ASOS placing problem, it’s natural and has been there way before the airport ever existed.

  34. rgbatduke says:

    This happens at RDU as well. An interesting consequence of this is appearing. I subscribe to Weather Underground and keep its page open in a browser panel all day. Recently I’ve noted an interesting discrepancy between the NWS forecasts for RDU and reality. First, the forecast is almost always high compared to what the day turns out to be, on average in the area. Second (and perhaps more interesting) it often remains high even well into the day of the forecast as the temperatures are obviously not going to make the mark, perhaps because there is unexpected cloud cover and the temperature is in no way going to make 84, it will be lucky to make 78. Third, weather underground actually has a regularly updated local forecast one can click through too with the expected temperature every four hours, and this will often have reasonable predictions that aren’t aligned with the NWS forecast. Fourth, the minimum temperature predictions for a day are often absurdly incorrect, but in a way that again almost always makes them higher.

    For example, on the Weather Underground page for Durham, NC right now the low temperature prediction for Friday is given as 41F. The temperature outside right now is 41F. However, at 5 am, the temperature outside was 35 F — a few short degrees away from a disastrous frost (that for some reason they failed to warn of yesterday). The Weather Underground’s hourly report (that you have to click through to see) clearly shows the drop to 35 around 5 am, but the NWS forecast is what they put up on their main page and it is already absurdly wrong. What’s up with that?

    One thing that’s “up” is that somebody who just looks at the NWS numbers and doesn’t actually track temperature is left with the impression that the minimum temperature of the day is some 3K/6F warmer than it really is/was. When they do the same thing on the warm side with the high temperature, the whole day appears warmer than it is, was, or will be. Since most people do not track the actual temperature but instead look only at the forecasted temperatures in the newspapers or on weather sites, by posting consistently high forecasts the NWS effectively shifts reality several degrees warmer everywhere in the minds of the people. After all, nobody posts the maximum and minimum temperature actually observed yesterday so nobody knows how accurate the forecasts were or what the high and low really were unless they look!

    I would bet that even a cursory examination of NWS forecasts would reveal the high bias — it is quite pronounced in Durham and I have no reason to believe that it isn’t as obvious elsewhere. Sadly, today isn’t even an unusual case — a low forecast higher than the already observed low for the day.

    The big question then is, why? I’m not one for conspiracy theories — I find it difficult to believe that there is a fiendish person in the NWS who has coded “add 3F to all forecast numbers” into their computers. Perhaps it is just this phenomenon at work. The “official” Raleigh/Durham temperature site is generally taken to be RDU (the airport). Never mind that the airport is flanked by three roads that carry several million cars past the airport every day, maintaining a blanket of local CO_2 and H_2O from the car exhaust over the airport itself. Never mind that (as a busy airport hub) it has jets idling and landing and taking off every few minutes all day long, dumping equally huge amounts of CO_2 and H_2O from burned jet fuel out in the sky directly overhead (in case the cars alone weren’t enough). Never mind that 40 years ago when I first arrived in Durham to go to Duke, the entire airport was the size of a small-town bus terminal with a dozen planes a day and a tenth of the car traffic going anywhere nearby. Never mind that today Raleigh, Durham, Morrisville, and Cary have grown out to surround the airport with city and stores so that the haze and greenhouse gases of the entire urban area continue to blanket it no matter what direction the wind blows. And then yeah, it has a lot of runways, all black tarmac, and I’m quite certain that when the wind blows just right it spills all that extra heat right onto its weather station(s). It could well be that its peak temperature is several degrees warmer in spikes, that it stores enough heat in its runways and traps it with the local greenhouse blanket at night to keep is lows several degrees higher than they are ten or fifteen miles away on the outside of the urban ring that surrounds it. Maybe NWS forecasts are just (correctly) forecasting spurious temperature readings caused by siting the area’s official temperature at a flawed site.

    The big question at this point is — why bother? We don’t need to make any single weather site “the” official site for an area any more. Weather Underground also accepts input from citizen-owned weather stations and makes them available in a standard web format to anybody that clicks through to them. There are dozens of them in Durham and the surrounding area. There are rural sites and urban sites. All of them record the temperature all day long (and the wind and rainfall) so that graphs of them are instantly available, and all of them have history automatically stored so you can see the record of any station on any given day since the station was established (or various averages).

    Of course this is horribly unscientific. People site their stations (I’m sure) wherever they like on their property, more often at a location dictated by esthetics or a need to cable it up than by weather measurement perfection. Some are in the woods, some in open fields, some on the sunny side of the house, some on the shady side, some are urban and some are rural, some sit on hills and some in valleys, and all of these things will cause the local readings to be a few degrees warmer or cooler than the readings that would have been obtained as close as the other side of the house. Still, doing a flat average of all of these sites, “sight unseen”, within a given radius around RDU would beat the hell out of using RDU alone simply because one could hope quite reasonably for these variations to correctly average out to a meaningful average temperature.

    Better still would be to locate not a single official station but a web of official stations at selected urban, suburban, rural farmland and rural woodland sites in a 30 mile circle around RDU and use an average of them all. The record of them all would also provide meaningful data on the UHI effect and quite aside from “UHI” per se on the actual spatial granularity of temperature variation on the ground. My own belief is that “weather station measured” temperatures vary by degrees F over lateral distances as little as tens of meters, and that much of that variations is highly systematic and consistent.

    Still, I think it would be very interesting to write a top article on the possibly inadvertent “NWS Prediction Fraud”, if one could obtain the records that would clearly demonstrate it. Given that the NWS predictions are the reality for most people, a systematic bias in those predictions is all that is needed to provide the illusion of warming in the United States.

    rgb

  35. JT says:

    A few years ago, WUWT did a piece on the same subject. I took it to heart and drove to BWI on a sunny day with a slight NW breeze. There is a road that completly circles the airport. I drove the circle twice and observed that that temp was ~3 degrees warmer downwind of the airport compared to upwind. On the downwind side (near the park on Dorsey Road) the runway is only a few hundred feet from the road. This spot had one of the highest recorded temps according to my car thermometer.

    Accurate for landing a Jet, not so good for recording high and low regional temperature records.

  36. exNOAAman says:

    Here you will notice the temp for the Baltimore Science Center, (in the heart of downtown), was also 62F:
    http://www.weather.gov/data/obhistory/KDMH.html
    But…take a close look and note that it is a reasonable climb from 61.
    And, as I have written before; BWI normally runs a few degrees cooler than Balto city. BWI expanded a few years back and made things even hotter.
    Here also is the UMBC station, 6 miles away, near my office.: http://weather.umbc.edu/
    Unfortunately, their site often malfunctions, and I can’t get it to give up yesterday’s plot. Maybe someone else here could? I watch it all day, and it never got out of the 50s yesterday…unless it sneaked by me.

  37. Dr. Elliott Althouse says:

    I have never understood why average daily temperatures are not calculated by averaging readings made every ten minutes throughout a 24 hour day. In Southeastern Virginia, my home, we have many instances of warm air at night ahead of cold fronts in the winter that yield a daily high temperature in the 60s even though the temperature was in the 60s for under one hour and was under 40 for the following twenty three, yet the daily average temperature is listed as 50. This happens at least three times each winter, and has happened more than once in the same week. Since there are no warm fronts that are as starkly temperature contrasted as cold fronts, nor as numerous, There would always be an overall warm bias in these averages.

  38. Bill Tuttle says:

    Gail Combs says:
    April 13, 2012 at 5:21 am
    I thought this set of paired temperature data does a bang-up job of showing how airports are rotten for gathering the accurate temperature data.

    The ASOS stations are for reporting conditions at the airport. Period.

    Using the readings as proxies for the surrounding area is foolhardy. I’ve seen temperature differences of +5°C between what the tower was reporting and what I was reading on my free air temp gauge at my location just outside the control zone. And at my altitude (500 feet AGL), the adiabatic lapse rate only accounted for one degree of the difference.

  39. Corey S. says:

    Mosher,
    “Its not a big mystery why UHI is real and why it doesnt show up in the record.”

    Didn’t it just show up in this record? It may not show up all the time in the record, but it looks as though it does show in some of the record. As you say, ‘conditions have to be right’…and they were.

  40. Don says:

    Statistical analysis shows that this is not an “open and shut case.” The following are some standard deviations (2000-2010) for daily high temperatures:

    BWI: 18.292°
    DCA: 17.949°
    MD Science Center: 18.653°
    National Arboretum: 18.651°
    Vienna: 17.095°

    If there were a problem with the siting of the ASOS, one would expect a much larger difference in the variability of high temperatures between the Maryland Science Center and BWI. If one expands the area to include the Washington, DC area, one finds greater variability among sites in and around Washington, DC than between the Maryland Science Center and BWI.

    In the end, what very likely happened was that downsloping, not heat from the airport runway led to the brief bounce in BWI’s temperature.

  41. Dr. Elliott Althouse says:

    Don- If the temperature was consistently higher there would be no impact on deviation. Only if it was a sporadic event would you see statistical evidence. On non-windy days, heated jet exhaust will at some point waft past the station, yielding the temprary high temperature. This is why airports are lousy station sites.

  42. Matthew W says:

    Corey S. says:
    April 13, 2012 at 7:02 am
    Didn’t it just show up in this record? It may not show up all the time in the record, but it looks as though it does show in some of the record. As you say, ‘conditions have to be right’…and they were.
    ======================================================================
    If the above example is correct, would you actually call it “UHI”?
    This is just a siting issue

  43. eric1skeptic says:

    Similar problem at nearby DCA (Reagan National). The area around the ASOS station is covered in dark gray gravel. Anthony noted it in 2010 when it was running hot: http://wattsupwiththat.com/2010/06/01/hot-air-in-washington-dc-more-asos-failures/

    Believe it or not, they have added more gravel since then. I took this google capture about a year ago (it’s still the same currently) http://i433.photobucket.com/albums/qq51/palmer2/national-asos.jpg Left is from Anthony’s post, right is current.

  44. JohnWho says:

    Steven Mosher says:
    April 13, 2012 at 2:35 am
    omnologos says:
    April 13, 2012 at 12:24 am (Edit)
    UHI, as it’s well known, is a phenomenon that happens locally everywhere but, as if by magic, globally nowhere.

    #############

    its rather easy to understand
    1. Its a function of windspeed and direction. Note the temperature changed for 10 minutes
    when the wind changed.
    2. Its a function of timing. If that wind change happens at 19:54.. no change to TMAX
    Its not a big mystery why UHI is real and why it doesnt show up in the record.

    And the cloud cover at each recorded event, and the moisture content in air, the physical change(s) for different recorded events, and more.

    It is entirely possible that every improperly sited station would need it’s own unique highly tuned adjustments as no two recording events would be under the exact repeated circumstances.

    We know there is a UHI/LHI effect but has any site been shown to have been properly adjusted, let alone the entire network?

  45. Pamela Gray says:

    However, to be succinctly correct, one would have to say that in this instance, man-made warming was caused by the burning of fossil fuels.

    Instead of carbon exchanges and hidden taxes, let’s shut down transportation and see how the greenies like THAT one! How will they get to their next conference in Cancun?????

  46. John F. Hultquist says:

    mfo says:
    April 13, 2012 at 3:37 am

    “It seems very odd to locate a weather station just south of that part of the runway from where aircraft are taking off, . . .

    It might be odd if the purpose was a long term study of climate. For the pilot about to lift-off along that ribbon of concrete the “real close” measurements are just fine. Weather data from a irrigated green park a few miles away are not superior.
    ————————————————–

    Anthony placed a table from BWI in his report. Notice it does begin with the heading “CLIMATE REPORT.”
    The “climate” seems to be a lot colder this Apr. 13th than in 2011. !!

  47. RobRoy says:

    Seems to me if a thermometer is anywhere near pavement of any sort, then it will manifest UHI. The severity of this UHI would depend upon the prevailing winds. Trying to correct this thermometer data would be pure guesswork.

  48. Rod says:

    I concur with rgbatduke that this has been a problem at RDU ever since they moved the location of obs equipment from the NE sector of the airport to the current ASOS site in the NW sector near the north end of the 10K ft runway in 1994.

  49. Don says:

    Standard deviation is fluctuation. If the Airport had a siting issue with the kind of problem alleged in the opening message, one would expect larger variability from high temperatures due to runway-related spikes. That isn’t the case. BWI’s high temperature variability is similar to that of nearby sites. It is highly unlikely that the Airport is suffering from runway-induced temperature spikes that distort its overall temperature record.

    Consistent warmth e.g., UHI, would lead to a higher temperature average and particularly less variability in low temperatures.

  50. Don says:

    Also, just so my point is clearer, I’m not saying that the runway has no impact. I’m suggesting that its impact is so small that it cannot explain the temperature bounce in question. Downsloping winds can lead to such scenarios and I believe that is what happened at BWI.

  51. DonS says:

    Pete Olson says:
    April 13, 2012 at 12:52 am:
    ‘poorly sited’, not ‘sighted’

    Pete, I’m sure many of them are poorly sighted as well.
    Sure would be interesting to see a collection of USAF obs taken taken downwind of the runway just after ten tankers and ten bombers had completed a MITO (minimum interval takeoff). At least to old SAC types.

  52. thelastdemocrat says:

    THe BWI and Raleigh-Durham stories show how this is perfect for maintaining a steady boost to global temps: our economy will continue on, we will have our population expand, and the invisible hand of the marketplace will make air travel cheaper (in the long run) and or the gains to be gained by traveling will be lucrative enough that air travel will steadily grow. Steady air travel growth means more heavily utilized runways, and more parking lots.

    Siting thermometers at airports is abt the best way to build in a steadily increasing bias. Freeways are not good, because in busy areas they will tend to hit their max traffic pretty early on. Suburban sprawl might be OK but you don’t exactly know which way the sprawl will move, or what mix of use will happen where. between green space, residential, and commercial.

    The airport is the one centralized location to have local temp build steadily across time.

  53. D. J. Hawkins says:

    DavidH says:
    April 13, 2012 at 3:25 am
    I can’t see what the problem is. If the wind shifted and the thermometer recorded 3 degrees higher in between the reported hourly observations, then isn’t that rightly the maximum for the day? Are we arguing here that observed temperatures should be adjusted according to our preferences? (There’s already one team playing that game.) As long as past brief spikes and dips in temperatures have been faithfully recorded then these 3 degrees shouldn’t be any cause forma concern. Or am I being too optimistic that the dips haven’t been discarded by “the team” and only the spikes kept?

    The problem is that the average temperature for that day at that location is the average of the high and low. This is what Hadley and GISS use for calculating the extent of global warming or cooling. The implied assumption is that the temperature varies smoothly and gradually from the day’s high to low and the next high, etc. and that the high and low can be averaged to determine the mean temperature for that 24 hour period. If the true high were actually 59, then the average temperature would be 48, not 50. And if you think that 2 degrees is a trifle, remember that the temperature anomolies are reported to the nearest 0.01 degree (for better or worse). Now, how many sites need to be affected in a similar manner over the course of a month to move that month’s anomoly by 0.02 or 0.05?

  54. RobW says:

    I had a discussion with a retired meteorologist last night. He too is firmly in agreement that AGW is a crock.

  55. Justin Berk says:

    I am the guy that first reported this (Justin Berk) and have noticed it for years. I have made many attempts to get NWS to acknowledge it, which sometimes is met with the response that a tech certified that it is accurate. I did get a response today that I will write about on my Examiner.com page and will be posted on my Facebook page for conversation. I’d like to chat with anyone else who sees the scientific importance. If +3 degrees is not such a big deal in these conditions, consider that these conditions of prevailing wind and afternoon sun occur more than 50% of the year. Doing some crude estimates, 1/2 the days and 1/2 the daily temperature extremes would results in +.75F higher results over the course of a year (on average). Wouldn’t that throw off our data set since ASOS was implemented for much of the nation… umm around 10-15 years ago?
    Anthony, you and I both wrote about the 106F reading in the summer of 2010. I wish you would have linked your story here. You pointed out the exhaust from the structure just west northwest of this ASOS with exhaust. This is similar Chicago’s temp jump in ’97 or ’98 after they moved their sensor next to the exhaust from the building. They had to go back and adjust it after some diligent scientists placed heavy scrutiny.
    Please contact me on my FB page to chat https://www.facebook.com/pages/Justin-Berk-Meteorologist/54875673475

    I encourage many of you to check out http://www.surfacestations.com to see how many weather stations are not complying with NWS/NOAA standards in the US. It is alarming!

    * Note that nearby Weatherbug stations are almost always cooler and they are calibrated. I wanted to do a comparative study for my former TV station last spring, but we never made it happen. What caught my attention was a date over the weekend with a +4F spike over hourly observations. If wind gusts must be a 1 minute average, why don’t we have a criteria for how long a temperature is measured to qualify. The spike based on a one tome reading seems inaccurate considering the history with the wind direction. Heck west-southwest is worse. When we get back into the 80s on Sunday and Monday, look out. Many have asked if we can hit 90F on Monday. Honestly- I don’t think so, but based on this ASOS site, all bets are off.

  56. Neil Jordan says:

    Re Gail Combs says:
    April 13, 2012 at 5:21 am
    and
    Bill Tuttle says:
    April 13, 2012 at 6:37 am

    The GISS figure headings caught my eye. The link labeled Norfolk International Airport shows GISS figure heading “Norfolk/Int., (36.9 N, 76.2W)” The link labeled Norfolk City shows GISS figure heading “Norfolk/Nas (37.0 N, 76.3 W)”

    Is it possible that Norfolk/Nas is actually Norfolk/NAS as in Naval Air Station, Norfolk? I checked the coordinates of the airports with Google Earth, and the rounded values closely match the GISS coordinates, which is consistent with NAS Norfolk being northwest of Norfolk International. The city itself is generally north of the airport.

    If Norfolk/Nas is indeed Norfolk NAS, it would be worthwile to investigate the differences between station locations that result in such large differences in readings.

  57. Trevor says:

    So what about all the days when the wind is blowing from the west ALL DAY LONG? The max temp and highest hourly temps will be in sync, and it will never be detected that the temp is being influenced by jet engines. NWS may or may not adjust this day, after being called on it. But they won’t be called on all the days when the influence of 200 hot jet engines and hundreds of acres of asphalt is the “norm”.

    And what about all the other stations at airports, at water treatment plants, within 10 feet of buildings, near busy roads, etc.? Jesus, after the work of Anthony and the volunteers of the surface stations project, how can ANYONE, with a straight face, point to the temperature record and claim it as PROOF that the planet is warming?!So what about all the days when the wind is blowing from the west ALL DAY LONG? The max temp and highest hourly temps will be in sync, and it will never be detected that the temp is being influenced by jet engines. NWS may or may not adjust this day, after being called on it. But they won’t be called on all the days when the influence of 200 hot jet engines and hundreds of acres of asphalt is the “norm”.

    And what about all the other stations at airports, at water treatment plants, within 10 feet of buildings, near busy roads, etc.? Jesus, after the work of Anthony and the volunteers of the surface stations project, how can ANYONE, with a straight face, point to the temperature record and claim it as PROOF that the planet is warming?!

    Damn, if I could put 89% of the thermometers that make up the official temperature record of the US inside my refrigerator, I could “prove” that we are in the middle of the worst ice age this planet has ever seen.

    Damn, if I could put 89% of the thermometers that make up the official temperature record of the US inside my refrigerator, I could “prove” that we are in the middle of the worst ice age this planet has ever seen.

  58. buntChE70 says:

    2-3 ° F max temperatures in between the hourly temps are routine for the KIAH the weather station at Houston Intercontinental particularly in the summer.

    My father inlaw flies free flight model planes at the Randolph AFB auxilary air field in Seguin, Tx. (on weekends when the airfield is not being used). They commonly launch from an abandoned runway. He uses a thermocouple with digital readout to look for thermals. He who knows how to launch into a thermal wins.

    I have observed 3 &deg F; spikes when a gust of wind comes along. The spikes last no more than a minute followed by cooler air. I haven’t really thought about it before but we are on the runway and the airfield is not builtup like IAH. My point is that it might not be just the concrete but maybe the open field that is the source of the hot air. I was not paying much attention to whether the gust was across or along the runway. Admittedly, not enough observation here for any conclusions.

    This is no attempt to discredit UHI. More a point that point by point near surface air temperature measurement in general is a lousy way to determine global temperature trends.

    I think the point made earlier that at some point in time all temperature measurements were made manually on the hour (as determined by the individual) then, I suppose, recorded by circular analog charts, and now recorded digitally on some frequent basis. So there is a bias introduced over time. Perhaps Anthony could address the evolution of weather station instrumentation. Or provide the link in the likely event that he has already covered the topic.

  59. Gail Combs says:

    rgbatduke says:
    April 13, 2012 at 5:45 am

    This happens at RDU as well. An interesting consequence of this is appearing. I subscribe to Weather Underground and keep its page open in a browser panel all day. Recently I’ve noted an interesting discrepancy between the NWS forecasts for RDU and reality….
    _________________________
    Just to add to what you were saying, I am about 30 – 45 mins southeast of RDU in the country. It was 30F when I got up yesterday (5AM) and there was ice on the water tanks compared to your “… 5 am, the temperature outside was 35 F…”

  60. Gail Combs says:

    I should also say using Wunderground, you can not prove we are having “Global Warming” around here.

    Central North Carolina (Sanford) Monthly temps over 90F for 2004 & 2010
    April 2010 (1)………..April 2004 (6)
    1day – 91F……………..2 days – 91F
    …………………………….4 days – 93F

    In 2011 the April highs ranged from 55F to 86F we did not see temps over 90F (91F) until May23th!!!

    So far in 2012 we have had highs ranged from 60F to 84F. Right now it is a chilly 67F.

  61. Dave A says:

    Dear exNOAAMan

    I have buckets of data
    Here’s the KDMH Plot since the beginning of the year http://www.theglobalthermometer.com/igraphs/stations/KDMH.png
    and here’s KBWI
    http://www.theglobalthermometer.com/igraphs/stations/KBWI.png

    ignore the 30C + peak at the beginning of the year I have to strip this out of all the USA data as NOAA (helpfully) redesigned their website for USA only weather stations and it took me a little while (2days) to begin to capture the new non-METAR style data :-)

    It’s a work in progress I needed a second, unadulterated, opinion with which to push back on the scaremongering. So far I’ve proved that the first 3 months of this year were warmer than last but that’s hardly a shock :-)

    Happy to provide the raw data to anyone who would like to squeeze the truth out of it

    Dave

  62. I’ve posted a different perspective on this at washingtonpost.com: The case of the curious temperature spike at BWI airport: asphalt or the sun?

    REPLY: Anything to avoid UHI it seems with you guys. As for sun/wind debate. It could very well be both. Asphalt absorbs sunlight pretty well. More sun coupled with a shift of wind to the asphalt area can easily make a quick 3 degree jump. Sunlight by itself on grass, not so much. You didn’t mention albedo in your article so I’ll assume you don’t understand it.

    Bottom line – airports are a poor place for temperature observations used for climate purposes, as they aren’t representative and are very dynamic with land use changes, and, see this detailed analysis.

    http://wattsupwiththat.com/2012/04/13/warming-in-the-ushcn-is-mainly-an-artifact-of-adjustments/

    Airports are part of USHCN.

    – Anthony

  63. “Anything to avoid UHI it seems with you guys?” C’mon Anthony. I wrote a detailed blog discussing its prominent role in DC summer temperature trends. Is there a global warming signal in Washington D.C. summer temperatures?

    Excerpt: “it would appear, a large fraction [of the warming] is due to urbanization with some smaller, more nebulous contribution from greenhouse gases.”

  64. Andrew says:

    Don says:
    April 13, 2012 at 9:20 am

    You are testing the difference between sites over a rrealtively short time frame. What if, in the absence of a putative UHI bias at BWI, its ‘real’ temperature profile (ie. prior to its develpment as a major hub which someone above noted took place during the1970s) was significantly lower than the site you compared it to?

    In those circumstances, you are in fact highlighting the UHI bias by pointing to a lack of statistical variance in comparing a naturally warmer site not influenced by UHI with a naturally colder site (influenced by UHI?

    So indeed, you are right to say it is “not an open and shut case”. But not for the reason you identify.

    Furthermore, I made the point earlier that widespread and inappropriate use of linear interpolation to fill in data gaps between sites may provide for a statistical transmission mechanism in which UHI bias is propagated systemically throughout the temperature record.

    In addition, as air traffic and tarmac area increases, the frequency of UHI bias at directly effected sites (eg. BWI) will incease through time, in effect, amplifying the bias transmitted by interpolation through the record.

    So it might even be the case that your statistical comparison of sites is invalid because it fails the necessary assumption that the sites (data) are independent. That is, the data from each site could very well be directly related through interpolation.

    It seems that many assume that UHI is really a localised problem effecting only those sites directly concerned. But that is not justified. Again, linear interpolation works to propagate a UHI bias throughout the recorded temperature record.

    Surely, this must have been identified by now…?

  65. Scott Covert says:

    Don, thanks for the SD calc.
    That is not what I would have expected. Is the SD stated for all data or just Max temp?
    Could you show SD for Min temp and Max if the previous was the SD for all data?

    I agree with you, the SD should be higher at an airport in my opinion.

  66. Andrew says:

    The more I think about it (see my comment above) the more the ugly truth dawns on me that the land surface temperature record has been systematically corrupted.

    UHI bias at some monitoring sites has been transmitted to all other sites in space and through time through the inappropriate use of linear interpolation. The pre-requisite of statistical independence of data in spatial and in time series analyses is NOT satisfied. The monitoring sites are all linked by UHI and interpolation in space and time and the time series analyses generated from these data are INVALID.

    The land surface temperature record is correctly regarded as a work of fiction and ought not be used for anything other than highlighting the misdeeds of crooked climate scientists. It most definitely should NOT be used to determine government policy.

  67. johanna says:

    Being a bit of a weather nerd, I regularly check the local BOM temperature readings from Canberra airport during the day and night. Apart from the factors others have mentioned, the airport is unrepresentative of the surrounding area in that it is devoid of trees, flat, and surrounded by turf farms (grass doesn’t mind airport noise). As a result, the extremes in summer and winter are magnified.

    Also, weird things happen, like the temperature rising up to 2 degrees C for no apparent reason in the middle of a cold, clear night for about an hour and then falling back again. It can’t be planes because there is a curfew. At other times, the readings just drop out altogether for a period (they are updated every ten minutes). Anyway, the bottom line is that our ‘official’ temperature records are based on these dodgy figures.

    Given that reliable little weather stations are cheap as chips these days, plus, as rgb pointed out, lots of people have their own, it is a mystery why such third rate data is still considered acceptable. As Prof. Brown pointed out, averaging a bunch of these readings, something that could be done on a laptop these days, would produce much more reliable data even allowing for individual siting issues.

  68. Andrew says:

    RE
    johanna says:
    @ April 13, 2012 at 4:37 pm

    “Given that reliable little weather stations are cheap as chips these days, plus, as rgb pointed out, lots of people have their own,…”
    ——————

    Mmmm. But imagine if the Get UP! crowd or some other mass activist pro-GHG movement decided to manipulate the dataset, eg., by siting the devices on tens of thousands of window sills across the nation… if the activist flock was large enough… how could mass deception be controlled.. because let’s face it, these cults are defined by the capacity for mass deception.

  69. walterdnes says:

    Been there, done that. Early on in my career with Environment Canada, I was a “meteorological technician” (fancy name for professional weather observer). Even after winning a competition for an office job, I still did a couple of relief stints at YVR (Vancouver Int’l A) as an observer, when people were on course or on vacation and the place was short-staffed. This was in the early 1980′s.

    One afternoon, the temperature suddenly jumped a few degrees on the temperature sensors. The regular observing routine included a comparison between the automatic sensor, and a regular mercury dry bulb every 6 hours (syno hour). This wasn’t a syno hour, but I went and checked anyways, and the mercury thermometer had gone up as well. Not only that, it definitely felt warmer outdoors. When I got back into the office, I noticed that the wind had turned around. Instead of being a light sea breeze from Georgia Strait, it was now a light land breeze from Richmond.

    This probably happened a lot, but as a temporary relief observer, I wasn’t that familiar with the vagaries of the site, and it was new to me.

  70. jayhd says:

    This discussion makes me think of the George Carlin hippy dippy weatherman routine where he states “temperature at the airport is 88 degrees, which is stupid because I don’t know anybody who lives at the airport”. Given the problems that Mr. Berk has noted, and George Carlin’s astute observation, perhaps airport temperatures should only be used for things pertaining to airport operations.

    Jay Davis

  71. Don says:

    Scott,

    I just ran it for maximum temperature, as that’s what the author suspected was problematic. FWIW, there was an even closer match between BWI and relatively nearby Beltsville:

    Mean annual high temperature at Beltsville: 65.76°
    Mean annual high temperature at BWI: 65.76°

    Standard deviation in daily high temperatures:

    Beltsville: 18.259°
    BWI: 18.292°

  72. Don says:

    Scott,

    I ran the numbers of BWI vs. Beltsville for the low temperatures:

    Average low:

    Beltsville: 45.73°
    BWI: 45.96°

    Standard Deviation:

    Beltsville: 16.987°
    BWI: 16.880°

  73. eric1skeptic says:

    johanna said: “Also, weird things happen, like the temperature rising up to 2 degrees C for no apparent reason in the middle of a cold, clear night for about an hour and then falling back again.”

    That can happen on partly cloudy nights. A patch of clouds canl prevent heat from leaving the earth as quickly as it would without the clouds. When combined with a small amount of horizontal air movement from a warmer (cloudier) location or a bit of mixing from warmer air aloft (given radiational cooling causing a temperature inversion), the near-ground air temperature can pop up a degree or two for seemingly no reason.

  74. Leo Morgan says:

    @ Steve Mosher,
    thanks for that.
    As a quick aside, may I say that I was sure I knew your name, but due solely to my ignorance, I couldn’t place it. A quick Google search turned up the following link, which you may well have seen – but there may well be others like myself who would benefit from the reminder. http://blogs.telegraph.co.uk/news/jamesdelingpole/100022057/steven-mosher-the-real-hero-of-climategate/
    Sadly, Google searching for me tells you nothing about me. I have no such claim to fame, being merely a private citizen earnestly trying to be well informed.
    This is not the only area in which I am profoundly ignorant, of course. Please accept that I’m not being disingenuous when I ask “specifically who is the ‘they’ that you’re alluding to, and why are you confident that they really do do this?”
    As a separate matter, your brief explication of UHI asserts that it is a function of wind speed and direction. My mental image of UHI is that of cities spreading out in all directions around thermometers, which would mean thermometer readings would rise regardless of wind direction, or , it seems to me, speed. Accordingly UHI would show up in the record.That’s what I understood Roy Spencer’s map of ‘Global Warming’ vs city size to prove. http://wattsupwiththat.com/2012/03/30/spencer-shows-compelling-evidence-of-uhi-in-crutem3-data/
    Of course, its more likely that I’m wrong than that you are. Still, could I ask you to clarify where I’ve gone wrong?

  75. John M says:

    I noticed the same thing a few years ago for the Allentown airport. I was watching closely because the forecast high was advertised to set a record. Then, like now, the media were hyperbolic about “RECORD HIGHS!”

    Here’s the Weatherunderground link to the data for the day in question.

    http://www.wunderground.com/history/airport/KABE/2010/4/7/DailyHistory.html?req_city=NA&req_state=NA&req_statename=NA

    Note the very subtle bump in the temperature curve slightly after 2 PM, which appears to briefely top out somewhere above 90F. If you look at the hourly readings (usually recorded at nine minutes before the hour for some reason), the record has a “non-hourly” reading entered for 2:16 PM of 87.8 F. This is the highest reading on the tabular data, yet the recorded high for the day is 92 F, which I guess coincides with the little temperature blip on the graph. This was indeed recorded as “a record”. At about the same time, the highest wind gust of the day was recorded.

    Two private weather stations in the vicinity shows no such blip.

    http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=KPAWHITE2&month=4&day=7&year=2010

    http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=KPACOPLA2&month=4&day=7&year=2010

    Neither of the non-airport locations got above 90 F, nor did the smaller airport on the other side of town:

    http://www.wunderground.com/history/airport/KXLL/2010/4/7/DailyHistory.html?req_city=NA&req_state=NA&req_statename=NA

    Not being as pro-active as Justin Berk, I didn’t call the weather service, but I did send a polite e-mail asking about the blip. I received back a somewhat polite response that basically said “We know what we’re doing, sir.”

    As others have pointed out, although the daily temperature readings recorded at “official” weather stations are then subject to further processing and stuck into temp-o-matic algorithms for temperature trend analyses, the raw data are used for purposes of reporting “RECORD HIGHS!”

  76. Bob Gegg says:

    I received the same response as John M when I contacted the NWS office in San Diego re; Palm Springs AP faulty readings and also the Reno NWS regarding their airport faulty readings. Bob G

  77. rgbatduke says:

    Just to add to what you were saying, I am about 30 – 45 mins southeast of RDU in the country. It was 30F when I got up yesterday (5AM) and there was ice on the water tanks compared to your “… 5 am, the temperature outside was 35 F…”

    Interesting. To the southeast, too — the exact direction it is often a bit warmer (closer to the coast, over in the sandhills). We just missed a frost the last three nights running (low of 37F last night, fortunately for my peach and plum trees:-) which makes this, in the end, a rather normal year, if anything running relatively cool at the moment however warm March was. I generally consider 4/15 to be “last frost”, although I’ve had killing frosts in the first week of May in the last fifteen years (it killed all of my azaleas, that are winter hardy but very vulnerable to frost after they bloom) and spent an absolutely frigid Easter in mid-April three or four years ago all the way out on Ocracoke (right on the Atlantic, mind you, generally moderated by the ocean) fishing in a mix of snow and sleet in a 40 mph freezing wind (that yes, killed all of my peaches and plums back in Durham). But many years back in the 80s I used to plant my tomatoes 4/1 and get away with it.

    Personally, I think the most interesting way to compute average temperature in the US would be to:

    a) Contact the Weather Underground, or any other similar group that receives regular input from user-contributed weather stations.

    b) Take the data from these stations. It typically is an hourly or better timeseries, and available backward for many years per station.

    c) Cover the US with an icosahedral grid at a granularity such that most grid cells have at most one station.

    d) Sum local temperature times area for a suitable (adaptive) area per station, per time, applying a simple accept/reject criterion to “mark out” stations that are obviously down.

    e) Do an actual time average of the temperature per site! One has the data, why not? Indeed one can do this and compare the result to the average obtained from (max + min)/2 and get a clear idea of the bias inherent in the latter (if any).

    f) Compute the spatiotemporal average temperature by dividing out by area and time, using the actual data over the actual year.

    Come on, folks, it isn’t that hard. No need for any corrections, just compute the damn averages by summing and dividing. The only adjustable parameter, the average area assigned per site, can be computed using an algorithm that can be precisely normalized a variety of unbiased ways. Indeed, one measure of a good algorithm for doing the spatial integration required in the average is that it should produce the same result as all of the other good algorithms for doing so (there are several one can use) so that the result does not depend on algorithm or any personal choices that could lead to bias. Either Willis or I could come up with numerically sound algorithms for estimating an integral over a 2D surface from irregularly spaced data points, if only because we would actually look them up and test them with e.g. Monte Carlo data to be sure that they give the right answers (and at the same time, estimate their probable error bars).

    The key to doing this is to not correct for anything but a station being offline entirely or emitting obviously spurious results (a constant but incorrect/inconsistent temperature all day long). That way one ends up with a dynamic spatial map of temperatures. In fact, one could make a damn movie out of it — a false color scheme for temperatures, an hour a second, and you could watch the US temperatures evolve at the granularity of the stations from overhead over an entire year in a little less than three hours. UHI and probable spurious spikes would be perfectly evident. Child’s play.

    rgb

  78. Dave Dodd says:

    Simple method to remove noise (UHI) from data sampling: sample many times per reporting period (eg 3600 samples/hr) and simply average them. Even a “dumb” programmer can usually handle this algorithm without even understanding sampling theory. From my personal experience, mathamaticians/climate-scientists make LOUSY programmers when dealing with reality! Hands-on technicians, or even mechanics, do the best job. Just sayin’.

    ANTHONY: How come I have no cursor??? Feels like I’m using DOS ED:-)

  79. P. Solar says:

    “For a brief 10 minutes, the steady NW wind that persisted all day at BWI shifted to a westerly direction. That allowed the HEAT from the nearby runway to provide a quick 3 degree warm-up between hourly obs. Once the winds shifted back to a NW direction, the temperature fell back to 59 degrees. ”

    There is one big problem with this. Looking at the source linked in the article I noticed rather a lot of “things” on the supposed runway. Source: http://binged.it/HC0WPG

    Now most runways I’ve seen have been devoid of any object larger than a piece of DC-10 engine cowling. (No, I’m not joking but that’s another story).

    So I went to the link and zoomed out one step.
    http://www.bing.com/maps/?v=2&cp=qhw0dm8m8q77&lvl=19.64&dir=0.14&sty=b&where1=39.1666,%20-76.6833&for
    m=LMLTCC

    Ah! there’s “another” runway to the north of the ASOS location. So the ” steady NW wind that persisted all day at BWI ” was, in fact, coming directly over the REAL runway (not the smaller access road to the south of the sensor).

    Now I don’t know much about weather but our host knows a thing or two so perhaps there’s an explanation in different air masses or the part of the city over which the air just past.

    I would have thought that a notable change in wind direction would usually be accompanied by a change in temp. I’ll let Anthony go into that in more detail.

  80. E.M.Smith says:

    It’s important to remember that the purpose of the thermometer at the airport is to report the temperature over / near the runway. That is the air in which the wings will fly. Cold air lifts the plane better than warm air and pilots do a ‘density alititude’ calculation to know if they can get off the ground or not. Part of that calculation is air temperature.

    You do NOT want a false low as then you think you can fly when you can’t. The result can be a crash at the end of the runway. So all the primary users want that thermometer measuring the hot air over the tarmac and if it is in error, to error high; as that is the side of safety.

    The use of Airports is “exactly wrong” for climate purposes.

  81. johanna says:

    Prof. Brown and E M Smith – just a hurrah for your posts. What is so baffling is that fixing this problem is neither difficult nor expensive.

    It may not matter much in the world of Mr Mosher’s arcane data collection/processing (we had a brush about Paris elsewhere where he said in answer to a question about why the numbers didn’t fit Paris – we didn’t include Paris) – but people living in cities are being forced into all kinds of expensive policy measures based on these shoddy statistics.

  82. Eric in CO says:

    As a former helicopter pilot that spent lots of time on tarmacs and runways, I can tell you that is a horrible place for a thermometer. A slight breeze can kick off a warm blast to your face instantly from the asphalt heating. Not to mention possible turbine engine heat (800+ C) Funny I never get a hot blast of wind when camping.

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