Two Airports

OK, right up front, I’m not sure what to make of this.

I started with looking for an Airport and a non-Airport to compare, but in Wunderground (who make these nice graphs) the non-airport stations around here “cut off” just a couple of years back. So I’m stuck with two airports. Given that, I decided to take one that has had a large growth profile to an International Airport and one where there has been growth, but a whole lot less. Same “back from the ocean behind some hills with a view out a bay” geography. Same ocean influenced climate. (More wind in Salinas, though). But in a “Farm Town” that has not had as much “boom” at the airport.

To me, it looks like there is just some “cyclicality” showing in the graphs. I think there is more of a ‘hot tarmac’ signature at the SJC San Jose International Airport in the 1998 peak graph (and less in the present “cloudy a lot” graph) and it looks like Salinas has less of that. But the dominant feature looks like ocean cycling to me. Then again, it mostly looks like “things change a lot”.

I tried to make all the graphs the same. Jan 1 – April 30; but Wunderground has its own way about things, so it mutated some of them to end on May 1. The vertical scale also wanders around, so you must keep an eye on that and adjust for it. Properly, the daily data ought to be downloaded and the graphs made from that, all on the same page (and with the ‘delta’ between them calculated). Maybe if I can see enough reason to do it from these graphs I’ll take a look at that. (Or someone else could … hint hint…)

I’ve semi-randomly chosen some representative dates. Sometimes because that was about as early as I could reliably find. Sometimes, like 1998, because it was a ‘peak’ of some sort.

Back in 1953

San Jose SJC 1953 Jan to April

San Jose SJC 1953 Jan to April

San Jose is about 50 F in winter, popping up to 60 F in tiny peaks. Spring comes and we get some ‘rolling cycle’ to it with more time spent hanging out at 60 F (about 16 C) and less down at 50 F ( 10C )

How does Salinas compare?

Salinas KSNS 1953 Jan to April

Salinas KSNS 1953 Jan to April

Darned near the same graph, IMHO. The humidity shows up (why it’s missing from SJC is an interesting question…) but other than that, “wiggles match” is the dominant theme.

New Little Ice Age Scare 1976

By this time SJC has turned into a commercial airport. Significant traffic. Not the full scale Big Traffic Major Airport of now. Then you could park in “short term parking” for something like $4 a day, dash all of 100 yards across the street, pick up your ticket at the counter about 30 feet inside, then step out the door 10 feet behind the counter and onto the tarmac near the stairs up to your plane. But it WAS tarmac… Now much more space is paved. They’ve added huge parking areas. A giant new terminal (and the associated taxiways So how does it look then?

San Jose SJC 1976 Jan to April

San Jose SJC 1976 Jan to April

The San Jose scale is compressed compared to Salinas. You’ve still got that 50/60 rolling, but it looks to me like some of those winter lows have been lifted just a tad, and in the last half of March, that ‘dip between the peaks’ seems to hang a degree or two higher in SJC compared to Salinas. At the end, we “cruise out” with SJC hanging almost on top of the 16 C line while Salinas “cycles” a bit more and drops below the line. I think we’re seeing that tarmac effect.

Salinas KSNS 1976 Jan to April

Salinas KSNS 1976 Jan to April

That 1990 “warming not a peak” point?

Here, the two scales match again, so a direct visual compare works better. While barometric pressure is almost a twin (these two are not very far from each other) the temperatures have a persistent if subtile departure. From March 15 to the end, Salinas “hangs the 16 C line” pretty consistently. SJC, though, “pops up” from time to time almost to the 24 C line. IMHO, those are the first sunny days of spring making that tarmac warm. The first part of the graph continues to look very “twin like” to me. Some of the warm days may hang a bit longer, but it’s hard to tell. January just before the 16th, for example, drops faster at KSNS than at SJC. The end of February seems to “hang high” just a bit longer at SJC also. Both are times of dropping barometric pressure. As our dominant storm track is from the north east, clouds ought to arrive at SJC before Salinas, not after.

San Jose SJC 1990 Jan to April

San Jose SJC 1990 Jan to April

Salinas KSNS 1990 Jan to April

Salinas KSNS 1990 Jan to April

The Hot Peak of 1998

OK in 1998 we hit a peak and we’ve been falling ever since. How do these two look then?

San Jose SJC 1998 Jan to April

San Jose SJC 1998 Jan to April

Salinas KSNS 1998 Jan to April

Salinas KSNS 1998 Jan to April

Now it’s the barometric pressure scale that has shifted in one and not the other. Adjusting for that, they continue to look like substantially the same result.

Temperatures? Also a divergent scale. That right there tells you they were different enough for the software to choose different scalings. But let’s try to pick some points to compare “datum for datum”. The last two peaks in SJC are about 21 C. For KSNS, it’s closer to 19-20 C. The “dip” at the start of April is about 10 C for both, but that mid April “pip” goes higher at SJC. Hardly showing at all in KSNS. That warm spell each side of March 15… it’s about 16C with a pip to about 18 C at the end in SJC. For KSNS, it’s more like 15 C and the “pip” struggles to get over the 16 C line, even then not holding hardly at all. January continues to be 50 F / 60 F cycling for both, with a sporadic drop to 45 F or so on cold dips. Then it looks like at the start of February on another plunge of barometric pressure SJC “hangs high” a bit longer compared to KSNS. KSNS drops to 50 F and lays there, cycling a little each side in just a couple of days. SJC takes a week or so, finally matching in Mid February. To me, it looks like it just took a while to cool down all the cement and tarmac.

By this point, SJC is a major international airport. It’s had acres and acres of paving added. Flight schedules are much more often and much larger aircraft. All around, it’s just a more paved, more solar collecting, and warmer place.

Now, in 2011

OK, time passes. The Pacific Decadal Oscillation shifts. This winter and spring has been very overcast and it has rained a lot. There have been some sunny days, but not nearly as many as in the last couple of decades. It’s been too cold to plant tomatoes even at the start of April ( I’ve sometimes put them in end of March ) and the sun has been gone for weeks at a time. We have had a “couple of weeks rain / couple of weeks not” pattern of alternating warm and cold. So any evidence of differential solar heating? (Again, note that the scales are quite different, so we do this one “by the numbers” as well…) Barometric pressures look like a substantial match to me.

San Jose SJC 2011 Jan to April

San Jose SJC 2011 Jan to April

Salinas KSNS 2011 Jan to April

Salinas KSNS 2011 Jan to April

At about Jan 10th, Salinas does a plunge to about 40 F that SJC doesn’t follow. Hanging up closer to 44 F. It looks like “cold spikes” get clipped at SJC. (Perhaps those 20 miles of homes and factories in all directions… and the incessent traffic…) Mid January, we pop up to that usual 60 F “warm time”, but KSNS is more prone to cooling dips, while SJC just goes to the warm line and hugs it.

It looks to me like on that rising barometric pressure in Feb start, SJC warms up quickly in the sun while KSNS takes a bit longer to “come along”. Due to the differing scales, it’s hard to see if temperatures are much different in the end of February. The biggest thing I see is that SJC is much more “steady”. Excursions are dampened.

Mid March, we’re back near that 60 F line, but with Salinas just a bit lower, on average, than SJC. April looks to start about the same at both places to me. Again, the different scales make it harder to see for sure, but that “end of the graph” month or two looks very similar in both places. I guess being under clouds most of the time does that… The very start of April “dip” looks deeper at KSNS, but it would be better to use the numbers than trying to back out the distortion of the graph visually.

In Conclusion

Not much new. It looks to me like you can see the UHI impact in the dead of winter, and a solar / tarmac impact during the springtime (that is exacerbated by a PDO shift from “cloudy spring” to “sunny spring” and back on a 30 year basis). I think it’s pretty clear that compared to 1953 when these were “near twins” that SJC is now a degree or two warmer AND with much reduced volatility, especially downward volatility looks dampened to me.

IMHO, this kind of comparison needs to be done for each and every one of the Airport thermometers in the GHCN. It needs to be done at the “month by month” and preferably even “weather regime by weather regime” basis.

There is a significant UHI visible, and a significant Solar Tarmac effect seems to be evidenced at well.

To me, this all just shows that averaging it all together and hoping it comes out better is a gross error. Averaging is just hiding the important details of what really is happening. And that is not “Global Warming”, it is “Airport Tarmac”.

OK, that’s what I’m seeing; but this is pulling a lot of “vision” out of some pretty thin tea leaves and I could just be putting a load of “confirmation bias” into it. So if more folks could take a look and see what you see… So, you seeing something else?

Post Script

Salinas Airport has a photo gallery here, so you can look around:

It starts with a Blue Angels show, so you need to scroll in a ways to see the grounds.

The SJC site has a photo montage on the top page:

These two places are about 60 miles from each other ( or about 100 km).

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About E.M.Smith

A technical managerial sort interested in things from Stonehenge to computer science. My present "hot buttons' are the mythology of Climate Change and ancient metrology; but things change...
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14 Responses to Two Airports

  1. George says:

    I am not sure Salinas is a good analog with San Jose, Gilroy or Hollister would probably be closer. Salinas is on the other side of the mountains in Monterey Country and the climate is more coastal, closer to Watsonville in climate than San Jose.

    Hollister is KCVH and is in the same climate zone or Reid Hillview, KRHV, in South San Jose which really hasn’t seen a lot of change over the past 30 years or so. Small airport surrounded by suburban housing.

  2. E.M.Smith says:


    Gilroy is reliably hotter than San Jose. Further from the water. Hollister might work well, I’ll take a look.

    The airport at San Jose is right where the air comes off the bay, so it’s more “marine influence” than a bit further inland. If you go just a few miles up 101, you have Moffett Field that is basically fronting the salt marsh.

    Basically, the comparison hangs on the first graph being so close to identical. I probably ought to have done a ‘bracket’ of a few years each side; but this was what I had time to do today. At any case, if the first graph had been “offset” by 5 F, then I’d have just subtracted 5 F at each compare and the rest would have stayed the same.

    At any rate, I think the “lower hills” to the ocean at Salinas is compensated by the greater distance from water, with the result that the ’53 graphs are near twins. Then again, if 52 or 55 are “way different”, the whole idea hits the rocks…. but it really is about what the thermometers say then and now what we think they ought to say…

  3. George says:

    I have been in Salinas when the breeze comes in from the West and it can get pretty cold and damp quickly. Also, the fog will come in that far pretty often (I used to have friends there and visited frequently a few years back). The climate in Salinas is closer to that of Watsonville or Corralitos.

    By the way, if you ever want some awesome locally made sausage, try:

    Corralitos Market & Sausage Company
    569 Corralitos Rd
    Corralitos, CA 95076

  4. Adam Gallon says:

    I had a play with WolframAlpha. It appears to use airports/airbases.
    Comparing the nearest point to me, RAF Cranwell (EGYD), somewhere that’s not changed greatly, certainly since hard runways were laid, post WW2.
    WolframAlpha gives temperatures since 1930, Cranwell has several missing years, but has a solid record since the early 70s.
    Over the period from 1930, it’s yearly mean temperature has a linear trend of 0.04F +/-0.036F/yr. (Virtually no significant increase?)
    Choosing “temperature +London” gives London City Airport (EGLC) , a small commuter airport, 7 miles East of central London, with a temperature history from the late 1930s on WA (The airport itself dates from 1987)
    The trend for this place is 0.072+/-0.02F/yr.
    Would one be right in questioning the Climatologists’ view, that there’s been no real UHI effect for London since circa 1900?
    Just for fun, I’ve looked at Heathrow Airport (EGLL), surprisingly, the linear trend is more like Cranwell than London City, 0.047+/-0.016F/yr.
    Things temperaturewise, do seem to be on a bit of a downslope, since ~ 2000 (But using that as a start point would be cherrypicking, wouldn’t it?)

  5. George says:

    The problem with California temperatures is the strong influence of the PDO. You have to go back to at least the 1930’s to capture complete cycles and California has changed considerably in land use since 1930.

    In 1930 the population of San Jose was 57,651. In 1960 it was 204,196. in 1990 it was 713,600 and in 2010 it was 945,942.

    That is HUGE growth. It has changed from a farm town surrounded with orchards and fields to the third largest city in California (tenth largest in the US). It is behind only LA and San Diego.

  6. R. de Haan says:

    I really think the entire AGW doctrine is nothing more but a totally unproven theory.

    As Joe Bastardi pointed out in his latest publication where he updated the Central England Temps since 1659 (which is Little Ice Age territory, there is not much ‘change’ in the record.

  7. E.M.Smith says:


    Always up for a pointer to a local “little known” place that does things really well… and though I’m the only one in the family who likes it, I have a great fondness for “kraut and sausages” thanks to my Dad and the Amish farm history. Oh, and breakfast sausages too… Oh, and a Polish on a Bun with mustard and kraut… Oh, and BBQ Czech sausages … Oh…

    Yes, I’m familiar with how Salinas is different from San Jose. Especially in the summer when you can get a cold ocean wind rip up Salinas while San Jose bakes behind just slighly taller mountains. Part of why this is restricted to the late winter / early spring quarter. You don’t get the hot inland areas pulling in the ocean fog… (And it is dominated by the general cloud cover and major storm cycle).

    For me, the close match in 1953 is the key bit. That says that this part of the year, in those times, was about the same (within my ability to see it in the data).

    So while you have a nice “theoretical”, it’s not showing in the early data. So might I ask that if you would like to persue that particular theoretical further that maybe you spend some time looking at comparative 1950-60 years for “exceptions” or “contra patterns”? Showing that I accidentally landed on an odd match in 1953? (As I’m dealing with some family medical things right now so don’t have the time to sort through those data…)

    Simlarly, you could look at the data for 1953 (and nearby years) for other quarters (especially the summer quarter, IMHO) to validate when they match, and when that Salinas cold breeze off the ocean dominates. (That IIRC my times there tends to be summer / fall).

    In other words: Put some data and analysis behind your theoretical, please…

    Per the PDO:

    You don’t need a full cycle if you are doing comparisons of two places in the same cyclical area. I’m not looking at “rise per year over the time period” (that would need to exceed 60 years data to be valid). I’m looking at specific states in the PDO, in different growth histories, and trying to tease out what the data say.

    So, in a very hot PDO phase when there is more sun and less clouds, it looks like SJC has more “excess warmth” compared to KSNS. Sunshine matters and tarmac matters. Looked at recently (that spring clouds and rain part in 2011) there is almost not difference (so when the sun can’t warm the tarmac, the wind and rains make both places about the same). Roll it back to 1953 we were in about the same point in the PDO. ( 1953+60 = 2013 then 2013 – 2011 = 2 years off from a match. On a 20-30 year half cycle, or 50 – 60 year full cycle, that’s pretty good). At that point we’re just not seeing any difference to speak of, even in the sunny parts of that year.

    So it’s not a matter of plotting a trend, it’s a matter of comparing “like to like” points in the PDO and looking for “delta T” then asking “Why?”. That it points at UHI, urban growth, and tarmac growth is NOT a source of error in the analysis, it’s the answer to “Why?”.

    That was sort of the whole point of the exercise. Find a place that HAS grown fast, and with a rapidly growing airport, but with a very nearby place that has not grown nearly as fast (so is more like it was); AND where the early year (would rather have years, but didn’t have time to complete it… and seasons… and…) matches very well, then look at “Delta T over time and ask Why?”.

    To me it’s pretty clear that for SJC there is a ‘cold winter bottom clipping’ as the UHI prevents the dips of winter cold from dipping as far AND there is some springtime “sunny tarmac” bump during times when the sun is out. (PDO phase of sunny spring vs present PDO phase of cloudy spring). Yes, it’s just a pointer to “Dig Here!”; but I think it’s a pretty good one.

    @Adam Gallon:

    Gee, isn’t it cloudy in Britain quite a bit? ;-)

    At this point I’d be willing to speculate that if you repeated this exercize for a sunny place, like the South of France, you would find a similiar Airport Tarmac Solar Effect (ATSE) with a “sunny bump”, but if you look at places with less sun, you don’t find an ATSE. So if one selectively looked for “airport heat islands” at the wrong time of year or in cloudy places, you would find none… Thus “proving” it didn’t matter. But a sunny place with a good “A/B” shows it will contaminate the aggrigate data…

    I first started suspecting this from some of the “by month” dT/dt graphs for places like France. Spring months were warming while other months were cooling.

    So, IMHO, the ‘lack of warming” at the UK locations you site is something of a confirmation of the thesis that it’s the solar heated tarmac … or lack of it…

    @R. de Haan:

    IMHO, it’s an error term in all the adjustments and infilling and homogenizing that largely arises from UHI and putting all the thermometers at major airports just as the Jet Age expanded them greatly. (over 90% now).

    The rest is just overactive imagination that doesn’t want to actually look at the data and ask it what is has to say.

    Not everyone can look at 100 pages of temperature numbers and see what it says… or even a few hundred graphs of monthly data and pick out a small divergence. They would rather play with computer models…

  8. oMan says:

    Chiefio: nice work. Thanks, both for the results; and for the clear exposition of your strategy, your method, your sources. If we are ever going to get anywhere on this issue, we need much more of this. And your example should embarrass the “scientists” with their massive grants and peer-reviewed publications.

    Also agree that the plural of garbage is more garbage. Until the fine grain has been captured and evaluated (real numbers from real sites in real time and across time) and used to identify (or dismiss) putative drivers such as UHI, it is pointless and indeed hopelessly misleading to aggregate numbers and claim that they produce some kind of “robust synthesis” of what’s going on. But as you say above, most people would “rather play with computer models.” Big mistake.

  9. tckev says:

    Yet again, another fine post. Unfortunately those AGW fools will not see it for all the hokey hockey sticks.

    By the way here’s an interesting little site –

    Shows taxation with no representation – all for UN organized AGW funding.
    We didn’t have better use for that money did we?

  10. E.M.Smith says:


    Interesting map. Lets you clearly see that the “Pigeons” are the USA, Canada, Australia, and in huge measure, Europe. While the “fleecers” all all the tropical “3 rd worlders”. The USA leading the pack in being “committed”… (and we ought to be… to an asylum…)

    Japan has a giant pledge, but looks like it’s “busy” at the moment so has not “committed” (hari kari?) yet.

    $us 100 Billion PER YEAR is what they want?

    Sheesh… Almost makes me glad we’re completly broke…. Someone needs to tell them to go borrow it directly from China as our credit is not so good any more…

  11. R. de Haan says:

    Japan? Fukushima is boosting the progress of useless wind solar power and bio fuel.

    It’s a disgrace.

    People have become brain dead making investments in companies who base their products on Voodoo Science
    like this:

  12. R. de Haan
    People have become brain dead …
    That´s “progressive tanatophrenia” :-)

  13. E.M.Smith says:


    Well, I tried to get the “history and almanac” page for KRHV and KCVH. KRHV gives the history for KSJC while KRVH uses KSNS for history. You end up back at the same two I’ve used.

    Why they don’t have history for the other stations is an interesting question…

    I’ll add a chart for the rest of the year for SJC and SNS so you can see how they diverge in summer. That’s when the inland heating pulls the cool wiind into Salinas but doesn’t do as good a job for San Jose. That inland breeze keeps getting warmer as it runs down the valley to Gilroy, then eventually Hollister, so I’d expect Hollister to be even more ‘out of kilter” with SJC (as it is down wind of a 50 mile warming run…) For RHV, it’s on the East Side of the valley. It’s in the same UHI bowl, and the winds tend to drift that way, so it ought to show almost the same warming trend as SJC (though less ‘at the airport tarmac’ effect, it has added miles of pavement around it, including the Eastridge Shopping Center parking lots just off the end of the runway).

    It would have been nice to have the historical data / charts to show that, but Wunderground has decided “something nearby” is close enough for historical work…

    Don’t know what the deal is with Wunderground but the changes in the last couple of years have not been for the better.

    At any rate, for now we’re sticking with SJC and SNS during the part of the year when inland doesn’t heat and they both are “marine influence from a few miles away”.

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