Well, this is an interesting graph…
So “what is it?”
On the 25th, at the middle of the night local time, I collected a sample of “major airports and ‘nearby’ list of stations from Wunderground”. About 30 pages of it (cut / past, cut / past, cut / past, coffee, cut / past, cut / past,..)
The idea being to look through it for any interesting patterns in the data.
Mostly I noticed that while a very few airports were “near the middle” of all the surrounding stations (often in Europe where there were not a lot of ‘nearby’ stations in the listings) there were many cases where the airport was nearer the high end than the low or middle. (Often in the USA which seems to have more stations than anywhere else).
There was a little bit of Cherry Picking, in that I tossed (i.e. didn’t bother with the cut / paste ) on those stations that were not interesting. (Usually those without much ‘nearby’). This is also ‘unscientific’ in that I’ve not done the niceties of a truly random sample (depending on my brain to just ‘pick a city’ of interest) and not statistically valid (maybe 20-something locations total). Also I have no idea how Wunderground chooses to pick ‘nearby’ stations nor what ordering process ‘ranks’ them down the page. Oh, and while I mostly picked the large “international” airport, sometimes I didn’t. So for Sacramento, they have 2 or 3 airports that are “in town” (including military bases) and the new Sacramento International Airport is some dozen odd miles north of town out in the middle of farms and fields. Any “nearby” station will be far far away… so I picked one of the stations “near town”. That way the “nearby” stations have some hope of actually being nearby.
So in this posting I just started looking at the very last station I picked. Salt Lake City International Airport.
And it is curious…
The first data item is the graph is Salt Lake City International Airport. The data snagged for it at that time is:
3:42 AM MDT on July 25, 2012 (GMT -0600)
Elev: 4226 ft
Lon: 112.0° W
Lat: 40.8° N
Source Rapid Fire Updates™
Updated 49 min 54 sec ago
I then took the listing of ALL stations given below it (after allowing a minute or two to stabilize on the loading of the page). Looking through that list, I tossed the highest and the lowest.
MesoWest NWS, Salt Lake City, UT 32 °F
1400 W 4700 S Taylorsville, Ut, Taylorsville, UT 75.4 °F
Which are the very first and sixth from last listed, respectively. MesoWest had a second entry in the table (item #3 in the graph) that made it pretty clear that the freezing temperature was bogus:
MesoWest North Salt Lake #2 , Salt Lake City, UT 74 °F
and prompted me to pitch the highest and lowest as likely spurious (and not contributing much anyway.
For each city, the remaining data are stuck in an Open Office spread sheet, the average of all values calculated, and a plot made. Yes, I’ve done all this in degrees F. Sometimes I remember to swap the settings on Wunderground over to C, but often I don’t. As I’m in the USA it comes up in F by default (and since what scale is used is, really, completely irrelevant, I typically just don’t care…) And at 2 AM and later I’m not at my “most likely to care about what folks in Europe do or like” state anyway ;-) If it bothers you, you are welcome to repeat the process in whatever scale you like.
Back at the graph
The average of all 26 data items is 68.81 and that makes the Airport 4.19 F to the hot side of the average ( or 2.313C if I’ve converted correctly).
Now IF the airport were representative of the sample area, one would expect it to be closer to the mean. Hmmm….
If, on the other hand, airports tend to be located in broad lower valley areas where it is warmer than the surroundings, have large vertical mixing from the air traffic (that is warming on cold still nights) and has acres (hectares) of tarmac and concrete that are not as cooling as plants with transpiration; one would expect them to be a bit warmer than representative.
Yes, I need to ‘plot up’ all the other stations I sampled. Yes, it ought to be done with more formal analysis and methods. Yes, it would be very interesting to take all the stations and plot them by geographical data like relative distance to airport and relative elevation. This is a starting point, not an end. There is only one of me and “things take time” working solo. (Anyone else who would like is welcome to “Dig Here!” into any of those, as it looks fruitful…)
But for now, what we have is this one station and this one graph… and it is interesting.
First off, it is pretty clear that the Airport is close to the top of the graph. Yes, there are other stations near the same value, but it’s not in the middle nor near the bottom. It’s near where a line connecting the “tops” would run. This is not a cool station; nor even a median one.
Second, there looks to be more dispersion of values to the right than to the left. WUWT? One can only wonder. More of the graphs will need to be done to see if this is a “one off” or a common artifact. Are the stations laid out in physical distance order from the selected station? Is it a random artifact? Don’t know. All ‘future investigations’ and “Dig Here!” fodder.
I’m reminded of the way the long term graphs of GHCN have a bottle brush aspect where older data have more range and the later data (largely from airports) are more narrowly constrained in range and somewhat warmer. Could this, indirectly, be evidence that all airports are like that in some way? (“Dig Dig…here…”)
Finally, just the magnitude of the difference from the mean is surprising. 4 F warmer? 2 C is 4 x the IPCC “warming” so it would only take 25% of stations in this condition to account for all of the “warming” in the GHCN (and we know that airports are more than 1/2 of the GHCN stations). Yes, it will take looking at the rest of the sample and a formal analysis to figure out what impact this actually has; but on the face of it, it is clear that the Salt Lake City International Airport is unrepresentative of the actual average temperature measured in that area. (And as it cools into the evening, stations reporting ‘late’ ought to be high in comparison to the airport).
I’m sure there’s more that can come from this one little graph, but those are the big bits that stand out to me.
The Data Capture
Here is a copy of what I grabbed to make this graph. It’s just a straight cut / paste, so will be hard to read. Maybe someone can find an interesting pattern in it. If nothing else, it documents where the graph came from.
Salt Lake City International, UT 3:42 AM MDT on July 25, 2012 (GMT -0600) Elev: 4226 ft Lon: 112.0° W Lat: 40.8° N Source Rapid Fire Updates™ Updated 49 min 54 sec ago Get Free Weather Stickers® Share: Tropical Weather: Invest 98l (North Atlantic) Invest 90e (East Pacific) Weather Summary Jessica Parker Weather Underground Forecast for Wednesday, July 25, 2012. A low pressure system over the Northern Plains is expected to move eastward Wednesday and Thursday and become the main weather producer for the nation. Showers and thunderstorms will continue from the Northern and Central Plains to the Great Lakes and Ohio Valley. In particular, a slight risk of severe thunderstorms is expected from the Upper Mississippi and Mid-Missouri valleys across the Great Lakes, with the main threat of hail and damaging winds. Apart from this system, a frontal boundary will remain over the Mid-Atlantic and parts of the Tennessee Valley and Southeast. Showers and thunderstorms are anticipated with this system. Elsewhere, unsettled weather will persist over portions of the Gulf States. Expect showers and thunderstorms to become more widespread in the afternoon and evening especially over the coastal region. In addition, monsoonal flow will keep scattered showers and thunderstorms going over the Four Corners region. Farther north, a weak front in the northern Intermountain West may trigger a few showers and thunderstorms. Another hot day is in store for portions of the Central Plains, Mississippi Valley and Ohio Valley Wednesday and Thursday. Afternoon temperatures are expected in the 100s with possible heat indicies 105 to 110. Moreover, minimum nighttime temperatures will only fall into the mid-70s. Continue Reading… Weather Underground Broadcast Network Salt Lake City International Weather at a Glance Weather Station Salt Lake City (KSLC) Elevation 4226 ft Station Select Now Scattered Clouds Temperature 73 °F Feels Like 73 °F Wind(mph) 10 Sunrise / Set 6:18 AM 8:49 PM Weather Stations Station Location Temp. Windchill Dew Point Humidity Wind Precipitation Elevation Updated Type Website MesoWest NWS, Salt Lake City, UT 32 °F 32 °F - - North at - 0.00 in / hr 4220 ft 3 hr 42 min 54 sec ago MADIS SLC Mosquito Abatement District, Salt Lake City, UT 73.2 °F - 53 °F 49% South at 7.0 mph 0.00 in / hr 4229 ft 7 sec ago Rapid Fire MesoWest North Salt Lake #2 , Salt Lake City, UT 74 °F - - - SE at 7 mph 0.00 in / hr 4208 ft 57 min 54 sec ago MADIS BIGFOOT_SALTLAKE, Salt Lake City, UT 67.8 °F - 50 °F 53% East at 0.0 mph 0.00 in / hr 4250 ft 48 sec ago Normal downtown SLC, SALT LAKE CITY, UT 69.9 °F - 55 °F 60% NNW at 6.8 mph 0.00 in / hr 4266 ft 1 min 7 sec ago Rapid Fire Decker Lake, West Valley City, UT 71.1 °F - 52 °F 51% SE at 5.8 mph 0.00 in / hr 4243 ft 3 sec ago Rapid Fire APRSWXNET Woods Cross UT US, Bountiful, UT 71 °F - 54 °F 55% East at 2 mph 0.00 in / hr 4235 ft 27 min 54 sec ago MADIS West Valley, West Valley City, UT 69.1 °F - 51 °F 53% ENE at 1.3 mph 0.00 in / hr 4285 ft 5 sec ago Rapid Fire West Valley , Centennial Park, West Valley City, UT 68.5 °F - 54 °F 60% ESE at 0.0 mph 0.00 in / hr 4269 ft 4 sec ago Rapid Fire MesoWest Hawthorne , Salt Lake City, UT 73 °F - - - East at 3 mph 0.00 in / hr 4304 ft 1 hr 57 min 54 sec ago MADIS MesoWest WBB/U UTAH , Salt Lake City, UT 71 °F - 51 °F 49% NE at 7 mph 0.00 in / hr 4806 ft 27 min 54 sec ago MADIS University of Utah Campus, Salt Lake City, UT 68.4 °F - 48 °F 48% SE at 0.0 mph 0.00 in / hr 4757 ft 55 sec ago Normal Chelsea Cove, Bountiful, UT 67.8 °F - 53 °F 58% ESE at 0.0 mph 0.00 in / hr 5130 ft 4 sec ago Rapid Fire MesoWest BOUNTIFUL , Bountiful, UT 66 °F - 54 °F 65% ENE at 1 mph 0.00 in / hr 5049 ft 27 min 54 sec ago MADIS 1922 E 900 South, Salt Lake City, UT 71.4 °F - 47 °F 42% NNE at 0.9 mph 0.00 in / hr 4693 ft 2 sec ago Rapid Fire MesoWest U of U Mountain Met Lab , Salt Lake City, UT 67 °F - 49 °F 52% ENE at 9 mph 0.00 in / hr 4996 ft 27 min 54 sec ago MADIS Bountiful Bench, Bountiful, UT 63.5 °F - 48 °F 53% NE at 0.0 mph 0.00 in / hr 4986 ft 0 sec ago Rapid Fire MesoWest BOUNTIFUL/F G HOUSE , Bountiful, UT 67 °F - 60 °F 78% East at 1 mph 0.00 in / hr 4760 ft 37 min 54 sec ago MADIS MesoWest Natural History Museum Utah , Salt Lake City, UT 65 °F - 50 °F 58% NNE at 6 mph 0.00 in / hr 5061 ft 27 min 54 sec ago MADIS MesoWest Magna , Salt Lake City, UT 70 °F - - - SW at 4 mph 0.00 in / hr 4291 ft 57 min 54 sec ago MADIS Bonneville Golf Course, Salt Lake City, UT 64.3 °F - 46 °F 51% NE at 7.0 mph 0.00 in / hr 4865 ft 1 sec ago Rapid Fire 1400 W 4700 S Taylorsville, Ut, Taylorsville, UT 75.4 °F - 58 °F 55% East at 0.0 mph 0.00 in / hr 4281 ft 3 hr 34 min 41 sec ago Rapid Fire APRSWXNET West Bountiful UT , Woods Cross, UT 70 °F - 55 °F 60% South at 0 mph 0.00 in / hr 4330 ft 23 min 54 sec ago MADIS Service Dog Equipment, Magna, UT 65.5 °F - 49 °F 55% WSW at 0.0 mph 0.00 in / hr 4252 ft 0 sec ago Rapid Fire Mueller Park Canyon, Bountiful, UT 60.1 °F - 34 °F 37% NNE at 0.0 mph 0.00 in / hr 5200 ft 7 sec ago Rapid Fire Salt Lake Avenues, Salt Lake City, UT 67.1 °F - 51 °F 56% NE at 4.7 mph 0.00 in / hr 5233 ft 2 min 9 sec ago Normal Magna, UT 74.3 °F - 51 °F 44% SW at 0.9 mph 0.00 in / hr 0 ft 13 sec ago Rapid Fire
I just added Reno, Nevada as well. It has the same general pattern, but with what looks like even more range of nearby values. Analysis as above, pulled out highest and lowest outliers. They are:
MesoWest HIDDEN VALLEY 70
MesoWest BIG MEADOW 50
Same general look to the data. I changed the range of the graph to start with the first station on the axis and end at the last station, stretched it out a bit so the number of each station can be seen (for easier comparison to the data listing below – but remember the two ‘left out’ station when counting…) but we get the same ‘dropping to the right’ effect.
Reno at 68 F compares with the average of all (other than the two outliers) data at 62.75 F is 5.25 F or 2.92 C hotter than the average.
The Data (minus the weather report as it is largely a repeat):
Reno, NV 2:35 AM PDT on July 25, 2012 (GMT -0700) Elev: 4534 ft Lon: 119.8° W Lat: 39.5° N Source Rapid Fire Updates™ Updated 40 min 42 sec ago Tropical Weather: Invest 98l (North Atlantic) Invest 90e (East Pacific) Weather Underground Broadcast Network Reno Weather at a Glance Weather Station Reno (KRNO) Elevation 4413 ft Station Select Now Clear Temperature 68 °F Feels Like 68 °F Wind(mph) 9 Sunrise / Set 5:53 AM 8:17 PM Weather Stations Station Location Temp. Dew Point Humidity Wind Precipitation Elevation Updated Type Website MesoWest UNR CAMPUS , Reno, NV 66 °F 44 °F 45% East at 0 mph 0.00 in / hr 4479 ft 1 hr 15 min 47 sec ago MADIS MesoWest RENO RAIL YARD , Reno, NV 67 °F 40 °F 37% SW at 2 mph 0.00 in / hr 4460 ft 34 min 47 sec ago MADIS University Heights, Reno, NV 66.9 °F 42 °F 40% West at 4.5 mph 0.00 in / hr 4852 ft 1 min 21 sec ago Rapid Fire MesoWest DRI - NNSC , Reno, NV 67.0 °F 37 °F 34% NNW at 6.0 mph 0.00 in / hr 4950 ft 29 sec ago MADIS MAP DRI_RENO (P090), NV , Reno, NV 67 °F 39 °F 36% North at 8 mph 0.00 in / hr 5009 ft 35 min 47 sec ago MADIS Cashill / Caughlin Ranch, Reno, NV 60.6 °F 40 °F 47% WNW at 3.0 mph 0.00 in / hr 5040 ft 20 sec ago Rapid Fire South West Reno, Reno, NV 58.3 °F 34 °F 40% WSW at 0.0 mph 0.00 in / hr 5005 ft 16 sec ago Rapid Fire Panther Valley, Reno, NV 63.9 °F 40 °F 42% North at 6.0 mph 0.00 in / hr 4988 ft 3 sec ago Rapid Fire Juniper Hills, Reno, NV 57.9 °F 40 °F 50% North at 0.0 mph 0.00 in / hr 4820 ft 4 sec ago Rapid Fire Lakeridge Springs, Reno, NV 67.4 °F 41 °F 38% WSW at 0.0 mph 0.00 in / hr 4930 ft 3 hr 33 min 28 sec ago Normal MesoWest Sparks - UNR Ag. Exp. Farm , Reno, NV 59 °F 48 °F 68% SE at 3 mph 0.00 in / hr 4390 ft 45 min 47 sec ago MADIS Northwest, Reno, NV 61.2 °F 32 °F 34% - at - 0.00 in / hr 5270 ft 5 sec ago Rapid Fire MesoWest HIDDEN VALLEY , Reno, NV 70 °F - - North at - 0.00 in / hr 5321 ft 3 hr 0 min 47 sec ago MADIS MesoWest Sparks Boulevard , Sparks, NV 68 °F 42 °F 39% NW at 0 mph 0.00 in / hr 4385 ft 37 min 47 sec ago MADIS North West Reno, Reno, NV 62.0 °F 38 °F 42% WNW at 3.0 mph - / hr 5295 ft 10 min 39 sec ago Normal MesoWest DRY CREEK , Reno, NV 61 °F - - North at - 0.00 in / hr 4760 ft 40 min 47 sec ago MADIS Sparks - Shadow Mountain Area, Sparks, NV 60.7 °F 47 °F 59% SE at 0.0 mph7 0.00 in / hr 4401 ft 6 sec ago Rapid Fire Sun Valley, Sun Valley, NV 65.3 °F 40 °F 39% SSW at 0.0 mph 0.00 in / hr 4770 ft 4 min 12 sec ago Normal MesoWest BLACK SPRINGS , Sun Valley, NV 62 °F 42 °F 48% NNW at 0 mph 0.00 in / hr 5172 ft 46 min 47 sec ago MADIS APRSWXNET Reno NV , Sun Valley, NV 63 °F 38 °F 39% West at 0 mph 0.00 in / hr 5140 ft 22 min 47 sec ago MADIS Sparks, off Vista/Satellite Dr., Sparks, NV 64.9 °F 37 °F 36% NNE at 0.0 mph 0.00 in / hr 4511 ft 0 sec ago Rapid Fire APRSWXNET Sparks NV , Sparks, NV 67 °F 41 °F 38% West at 0 mph 0.00 in / hr 4596 ft 16 min 47 sec ago MADIS Golden Valley, Reno, NV 59.4 °F 39 °F 47% WNW at 0.0 mph 0.00 in / hr 5370 ft 2 sec ago Rapid Fire Sunset Pointe, Sparks, NV 64.8 °F 23 °F 20% NW at 0.0 mph 0.00 in / hr 4739 ft 41 sec ago Normal APRSWXNET Reno NV , Reno, NV 62 °F 37 °F 40% South at 1 mph 0.00 in / hr 4786 ft 17 min 47 sec ago MADIS Sparks-Kiley Ranch, Sparks, NV 67.0 °F 42 °F 40% South at 0.0 mph 0.00 in / hr 4469 ft 9 min 27 sec ago Normal APRSWXNET Reno NV , Reno, NV 62 °F 35 °F 37% SSE at 5 mph 0.00 in / hr 5186 ft 28 min 47 sec ago MADIS Double Diamond Ranch, Reno, NV 60.4 °F 43 °F 53% North at 0.0 mph 0.00 in / hr 4442 ft 15 sec ago Rapid Fire Reno South Hills, Reno, NV 59.7 °F 44 °F 56% South at 2.2 mph 0.00 in / hr 4545 ft 6 min 38 sec ago Normal MesoWest SOUTH RENO - WOLF RUN GOLF COUR, Reno, NV 61.0 °F 33 °F 34% SW at 4.0 mph 0.00 in / hr 4879 ft 28 sec ago MADIS Thomas Creek Estates, Reno, NV 59.5 °F 33 °F 37% SSW at 3.0 mph 0.00 in / hr 4984 ft 1 min 30 sec ago Normal Damonte Ranch, Reno, NV 58.1 °F 42 °F 55% South at 1.6 mph 0.00 in / hr 4465 ft 1 sec ago Rapid Fire MesoWest BIG MEADOW , Reno, NV 50 °F - - North at - 0.00 in / hr 8299 ft 1 hr 35 min 47 sec ago MADIS
One is interesting.
Two is an oddity.
Three is a pattern… I’m working on #3 now…