Friday, August 24, 2012

Sea-Tac Heat

Roughly a year ago, I provided some evidence that the construction of the third Sea-Tac runway, with the ancillary taxiways and removal of a vegetated slopes, has resulted in an anomalous warming at the airport during warm summer days, particularly when the winds are from the north or northwest.  This is important for a number of reasons.  First, Sea-Tac is the spotlighted station on many local TV weathercasts (see image).  Second, it serves as a example of issues with our observational networks, where urbanization and construction can produce a warming signal distinct from the true warming of the general atmosphere.


Well, we had some warm weather recently...do we see the Sea-Tac warm anomaly?
For example, 4 PM this afternoon?  Here is a plot of nearby stations (KSEA is the airport).  72F at the airport (where the winds were north-northwest) and cooler for the nearby locations.



Or a few weeks ago, when the airport was 87F?  Again, nearby locations were cooler.



In the old days, Boeing Field, closer to the urban core of the city, was generally warmer than Sea-Tac.  But is that true now? Here is a plot of the temperatures at these two locations for the last four weeks.  Note that on the warm days (generally ones with lots of sun and northerly winds), Sea-Tac (SEA) was warmer than Boeing Field (BFI), often by several degrees.
Multiple such urbanization/development issues at locations around the world, and it is clear that it can obscure the true background temperature change signal that we are looking for.  Organizations, such as the National Climatic Data Center, have tried to develop algorithms to spotlight or remove such problems, but there success so far is mixed.  Satellite observations of temperature above the surface are a bit less problematic, although they have their own issues (like calibration of replacement satellites).

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I will talk about some of the above issues during my talk on Orcas Island on Wednesday.


9 comments:

Justin Wilkerson said...

I can't help but notice the greater difference between Sea-tac and surrounding areas is seen on the cooler of the 2 days. A two day sample isn't enough to confirm what I'm thinking, but it does compare with what I see from my own station.

I live in the middle of an residential area, there was no place that I could put my sensor that abides with every rule of the siting guidlines. I settled for putting it on the roof. It is clear of obstructions, has a cover from the sun, etc. But it is exposes to the heat from I believe a combination of the nearby road and the roof.

The roof itself doesn't get too hot, I've gone up there in the middle of a warm day and felt it, but it could be reflected radiation (its a white-grey roof, not black).

In any case, I've noticed a trend for my sensor to depart from more official numbers MORE on days that are sunny yet cool rather than the very hot days.

On the hot days mine just warms up faster, but still ends up the same.

but a day where it is partly cloudy, windy, etc so the expected high is around 70-72 (like we've been recently) its not uncommon for my sensor to pick up to 75-76.

Sorry for the long post. Guess I'm just curious if you notice this. If Sea-tac tends to be closer to surrounding temps on the hotter sunny days vs the cooler sunny days.

diggingintheclay said...

IMHO this is a huge issue but challenging to show and quantify. Notice that on many of the warm days on the 4 week overlay SEA has a higher max but also a lower min than BFI. There are a few exceptions (e.g. 5/6th Aug) which may be down to wind strength or direction. This, I guess, allows many to say that any difference will be negligible.
- Verity Jones

As these are both airfields the differences are in the bigger area around the sensors; I looked at a set of roof weather stations a while back with differences in the surfaces:
http://diggingintheclay.wordpress.com/2010/07/17/thermal-absorption-a-black-and-white-and-green-issue/
This was only a quick, crude examination, but readily shows up the issues.

Steve Bloom said...

Gosh but isn't this almost Wattsian in tone?

Cliff, yes these things are problems and adjustments may not be perfect, which is why ~20 years ago it was decided to build the Climate Reference Network. Perhaps in your follow-up post you could check on the trend there. Unless the nearest CRN station was one of the very late installs, there should be enough of a record for a meaningful cross-check.

Cliff Mass Weather Blog said...

Wattsian?

The Climate Reference Network is generally first class...but unfortunately, there are so few of them and they are limited in time. By the way, I think very highly of Watt's surface station work...he has revealed how problematic many (most) of our surface stations are, as well as the poor QC work done by NCDC over the years. A national embarrassment, really...cliff

Steve Bloom said...

"he has revealed how problematic many (most) of our surface stations are, as well as the poor QC work done by NCDC over the years."

Has he really? For sure that's what he claims, but the literature says otherwise. Have a look at it, Menne et al. in particular.

Re CRN, I note two stations close enough for the trends to be worth comparing. One has about a five year record and the other a ten year one. You could also have a look at their paired USHCN stations. Plus of course there will be yet other USHCN stations in the region.

Cliff Mass Weather Blog said...

Steve,
Yes, Watts work is quite compelling and he has made an important contribution with his web site: surfacestations.org. We have problems with urbanization, poor temperature sensor locations, and problematic quality control...cliff

dbostrom said...

Something I don't understand, Cliff.

You dismiss certain climate bloggers and information sites as being of little value as the authors lack credentials, without specifying any actual problems with their conveyance of facts. A mild form of ad hominem attack, if you will; you center your critique on personal attributes without addressing matters of fact.

At the same time, you're endorsing Watts' work-- ignoring that it has be shown fallacious-- and you appear to have no problem with Watts' lack of credentials.

Your standard of judgment for approval does not obviously appear connected with scientific merit.

As I've said elsewhere, I think you're rather naive when it comes to the entire so-called "climate debate." It's hard otherwise to explain your affection for Watts other than you're taking his claims at face value, imagining that he's amenable to persuasion by facts.

Do a deep dive into Watts blog, look at what's been written there over the years, then ask yourself again if you're in good company.

If nothing else, be sure to check Watts' claims against the literature. Make a serious effort.

Please.

Tom Curtis said...

Having seen examples of Watt's surface station work, I am less than impressed:
http://wattsupwiththat.com/2012/08/23/antarctic-peninsula-was-1-3c-warmer-than-today-11000-years-ago/

Cliff Mass Weather Blog said...

Doug Bostrom and Tom Curtis,
Both of you are strong GW "advocates." I understand that. But you paint people...like Anthony Watts in black and white terms...and you are in error to do so. Some of what he says I disagree with (e.g., the potential future impact of increases in greenhouse gases), but in some areas he is very much correct...like the impact of urbanization and poor sensor siting. I have read his work and it is compelling. I have also looked at the data myself and confirm his concerns.
Folks like yourselves undoubtedly mean well, but your approach to demonizing the "other side" is corrosive to society finding a middle road. You can complain about Watts not having credentials, but surely that extends to you folks as well...cliff