Spotting Weather Stations in SFO

San Francisco’s official weather stations, new and old locations are in this photo – can you find them?

Last Thursday evening I had the pleasure of meeting up with Steve McIntyre, Steve Mosher, and “jeez” (who lives in San Francisco, and currently wishes to remain anonymous) from Climate Audit. We had dinner at Umbria in downtown SFO and talked shop about “everything under the sun”. Mostly we talked about things we’ve learned over the past year and the reactions to them. It was a great evening that I’ll always remember, and “jeez” was a superb host. My thanks to him not only for dinner but for some special help I’ll discuss later. Steve Mosher is a lot more soft spoken than his online persona would indicate, but very sharp witted, and Steve McIntyre provides great conversation and good humor.

Steve was attending the American Geophysical Union meeting this week and presented a paper on hurricane activity with Roger Pielke Jr. Given that climate was a big portion of the presentations at AGU, it seemed only fitting that I should survey the official weather station for San Francisco. Besides that, my previously intended survey at Santa Cruz was not working out. The next morning at my hotel, I checked the NCDC MMS database for the station (47772) and found it was located in Duboce Park, west of downtown about a mile. The database also said the station was on the roof of the Duboce Park recreation building, seen in the foreground in the picture above. I did a Google Earth aerial recon, then I programmed my automobile GPS and off I went.

I had forgotten how much I dislike driving in downtown San Francisco, with its odd streets, dead ends, one ways, railways, and hills, and after realizing that I was going in circles because some streets cannot be turned onto, I parked my vehicle and hopped onto the MUNI railway, which has a stop at Duboce Park.

Duboce Park Muni stop – the rec building where weather station was located on the roof is in the center of the photo.

The MUNI stop couldn’t have been better. It put me within 200 feet of the station location. I walked around a bit and soon discovered that the rec building was under major construction. It was completely gutted! So there was nobody there I could talk to about the weather station. I found a vantage point at a medical facility that had an outdoor plaza to the south and began to scan the roof. I had a full unobstructed view There was no temperature equipment I could see, but I was able to spot a rain gauge and an empty rain gauge stand on the roof of the larger building.

Rain gauge and empty stand on roof of rec building at Duboce Park

Since I’ve seen instances where the rain gauge was on the roof but the temperature sensing equipment is at ground level I walked all around the building, but the entire grounds and landscaping were torn up for construction, and it became clear to me that the station was out of service or had been moved. So I hopped the next MUNI, retrieved my vehicle and returned home empty handed, or so I thought.

When I returned home, I did some additional research to figure out what happened to the station and I came across a website operated by Jan Null, former lead weather forecaster for the NWS in SFO and now a consulting meteorologist. He had an excellent review of the station history for the downtown San Francisco station. To my surprise there have been a total of 15 moves through its history, the most recent in 2007.


My answer was here, the station had been moved to the US Mint building, probably due to the construction at the Duboce Park rec center. The most interesting thing I learned was that up until the most recent move, the SFO station had always been on a rooftop. The US mint location was the first ground level installation ever.

That tendency for a roof level location was problematic to the weather station and its records during the 1906 earthquake.

picture of san francicso after the 1906 earthquake
photo from The Museum of San Francisco
Three surviving structures in the Financial District can be seen in this dramatic photo. At far left is the Kohl Building on Montgomery Street, the Merchants’ Exchange Building on California and, in the center of the picture is the Mills Building on Montgomery where the weather station and weather records were located.

Doing some web sleuthing, I soon found a likely spot at the US mint from a Microsoft Live Maps aerial view.

New SFO city weather station at US Mint building – click picture for interactive view

But what to do? I’d already returned from SFO, but then I remembered my new friend “jeez” who lives in downtown SFO. I sent him the link to the aerial view, and he quickly spotted the station and commented “lots of barbed wire there” and said he’d give it a go the next day. He came through as promised with ground level photos.

New SFO city weather station at the US Mint building – click for larger image

“jeez” also pointed out that the big tank in the background contained liquid nitrogen, and that the panels visible through the weather station tripod are some sort of radiators for the tank. We’ve seen all sorts of micro-site biases in the study of USHCN station sitings, but I wouldn’t even know where to begin categorizing this sort of influence. It may or may not be significant.

In the meantime, I wanted to see if I could locate a picture of the station as it existed at Duboce Park. After consulting with Jan Null by email, I learned that even though the NCDC MMS database said the equipment was a “hygrothermometer”, implying a strip chart recorder, that it was actually a MMTS with telemetry back to the NWS office in Monterey. Again Microsoft’s Live Maps provided a view of the station as it was:

The station on the rooftop at Duboce Park – click picture for a larger interactive view

Given the way this station has moved around, I wondered what the temperature record might look like. I downloaded the time series from GISS, and here it is below:


At first glance, the record appears erratic, but when reconciled against station moves from the table provided by Jan Null, the offsets take on a meaning. “jeez” also provided some commentary based on his knowledge of San Francisco’s micro-climates.

He writes:

There are several station moves which could introduce strong biases, especially in the summer temperatures. San Francisco’s microclimates can vary more than 10 degrees F from one part of town to another. The gist of it is that I would expect a serious cooling bias from 1936 to present given the way the station has been moved.
1851 — not significant
1862 — not significant
7/1864 — slight cooling
1866 — slight warming (back to top region from 1851)
1871 — not significant
1890 — not significant
1892 — not significant
5/1906 — big cooling
10/1906 — big warming
1936 — cooling bias
1983 — hard to say probably a little more cooling bias
1997 — more cooling bias.
2007 — not significant

The 2007 move to ground level may or may not be significant, but I’m betting it will introduce a cooling trend that will be visible as a step in the time series because a rooftop is certainly a warmer place than the current location at street level. Note from the aerial view the station will get shade mornings and afternoons due to buildings.

Now compare the time series of downtown San Francisco to the SFO airport, which has an ASOS station at the middle of the bay side runway:

click picture for a larger interactive view


Here we see what looks like a clear effect of increasing UHI, due to city growth as well as airport growth. This station has been moved nearly as much, but more importantly its been located in an area that doesn’t have pockets of micro-climate.

The question is, what kinds of useful climate trend signals can one recover from stations like these? Neither station is part of USHCN, but both are used by GISS.


  1. jeez
    Posted Dec 16, 2007 at 3:03 AM | Permalink | Reply

    It looks like Mission Dolores was a little warmer as a location than I guessed off the cuff (I was nervous about that one, the Mission District can be sunny), but in general it looks like I got the micrositing bias trends generally correct.

    The big liquid nitrogen tank had big chunks of ice hanging from the pipes. That one definitely seemed unique as far as biases go.

  2. jeez
    Posted Dec 16, 2007 at 4:25 AM | Permalink | Reply

    BTW, as I noted originally, the micro-climate bias is far more pronounced in the summer (ie the famous Mark Twain quote). If you could graph the winter-only mean temperatures, you would likely have a trend that was far more representative of city-wide patterns and not nearly as affected by all the site moves. Of course, there would likely still be UHI and general siting issues, but the city’s weather is far more homogeneous in the winter.

  3. beng
    Posted Dec 16, 2007 at 8:25 AM | Permalink | Reply

    Putting temp sensors on roofs is simply ridiculous. Have you ever stood on a roof during a hot, sunny day? I managed numerous reroofing projects as an engineer, and you can fry there compared to ground level.

  4. VG
    Posted Dec 16, 2007 at 8:47 AM | Permalink | Reply

    looking at all the stations so far how could anyone trust Gisstemp data?

  5. Anthony Watts
    Posted Dec 16, 2007 at 9:04 AM | Permalink | Reply

    VG, the fault with placement lies with the NWS, not GISS, since the NWS is reponsible for siting and maintaining stations. Until I complete the USHCN survey (or at least a significant majority/best effort since we may not be able to get all stations)) and can do a detailed and unrushed analysis, I’m not going to draw conclusions.

  6. steven mosher
    Posted Dec 16, 2007 at 9:14 AM | Permalink | Reply

    re 3. NOAA started a study on the effect of rooftop placements of stations.
    It was not completed to my knowledge.. more unarchived data?

  7. Posted Dec 16, 2007 at 9:43 AM | Permalink | Reply

    You understate the case about SF microclimates. I used to live just up the hill from the current station at the mint and last summer I rode the Muni everyday to work past the former Duboce Park station .

    SF neigborhood temperatures are a function of fog. The mint station is right on the the edge of one of the so-called “fog free” zones. In summer out in the avenues (near the ocean) the children play in overcoats. They may not see the sun for weeks. Realtors don’t even try to sell houses in that season.

    But in the mission district it can be just plain hot. Typically in the summer San Francisco doesn’t have a cloud in the sky. Without a fog cover there is brilliant sunshine and temperatures can soar. The fog quite often forms a stationary front along the ridge of hills that is in the center of San Francisco. Some of the hills split the incoming fog and produce a kind of fog shadow. The mint is right near one of these fog shadows.

    In the East Bay the fog effect can also be drammatic. In August when you go west through the Caldecott tunnel (about 300 yeards) the temperature can drop nearly thirty degrees. In Concord (outside the fog) it can be 105 on the same day that it is 55 inside the fog just a few miles away.

  8. Posted Dec 16, 2007 at 10:09 AM | Permalink | Reply

    RE6 Mosh, I found one, not sure if it’s the one NOAA started or if it was outsourced. It was done by Pielke et al. See page 14.

    Also FYI here is the funding document:

    See the entry near the bottom 99-350W for Adler. But there is no link to a finished product and Adler is not mentioned in the Pielke study.

    here’s one by Griffith that can be had for $8.95 I really hate paying for taxpayer funded papers – its a double tax.

  9. Posted Dec 16, 2007 at 10:33 AM | Permalink | Reply

    What Pat says is true about the fog. Parts of the city, usually those by the Bay, can be warm and balmy, while other parts can be damp, cold and windy. That’s why the new Giants ballpark is nestled up against the Bay.

    When I moved to San Francisco in June,’81, I’d never been to “warm and sunny” California. I moved in with a friend in the Haight Ashbury and went to work for his construction company. Our first job was “out in the Avenues,” i.e. the Sunset District close to the ocean. I didn’t see the sun for two weeks.

    I also joined the local pub softball team. We played games at night in every corner of the city. Portrero Hill was usually the warmest. I learned to wear three layers of clothing. You could always take off layers, but you rarely wanted to. You’ve heard the Eric Burdon song, “A Warm San Franciscan Night.” He was celebrating a rare meteorological event.

    And yet, I remember walking in Golden Gate Park around Thanksgiving of that year and, as an East Coaster, being amazed to witness a hardball game in progress. A month later, around Christmas, I looked out the window and saw roses blooming in my neighbors yard.

    For those who haven’t heard it, the Twain quote that jeez alluded to goes something like this: “Coldest winter I ever spent was that summer in San Francisco.”

  10. steven mosher
    Posted Dec 16, 2007 at 10:55 AM | Permalink | Reply

    Anthony.. here was the link to the study

  11. Old Dad
    Posted Dec 16, 2007 at 11:01 AM | Permalink | Reply

    My college aged kids have swallowed the AGW alarmist propaganda hook, line, and sinker. While anecdotal, this scenario may help me talk them back from the brink. To my mind, much of the hysteria rests on unchallenged assumptions. E.g., we sophisticated moderns know how to measure air temperature. Set aside the enormous complexity of selecting sample sites, and focus on the seeming simple task of taking temperature readings. As this post shows, maybe it aint so easy. As anyone knows who has ever managed or maintained even simple mechanical systems, they fail all the time. Training competent operators is hard. They make lots of mistakes. They quit and sometimes force you to use inexperienced people who make even bigger mistakes. Neighbors and kids vandalize your equipment. Contractors lie about the maintenance they’ve supposedly done.

    If you examine the challenge from the perspective of simple logistics, it’s a pretty daunting task to install, and maintain 100 let alone 1000 weather stations. It would be a miracle if we didn’t have a fair amount of bad data.

    Good luck in cleaning up what you can.

  12. steven mosher
    Posted Dec 16, 2007 at 11:02 AM | Permalink | Reply

    you know Anthony, given the data quality act, and given the Siting standards violations,
    I wonder if the class 4 and class 5 data should even be made available to consumers such as GISS.

  13. Not sure
    Posted Dec 16, 2007 at 11:08 AM | Permalink | Reply

    I’ve driven by the mint so many times… Jeez, how did you get behind the concertina wire? That place looks like a prison from the outside. I live near the Cliff House, and we’ve experienced the 30-degree shift many times when we visited a friend that lived in Clayton, CA. The wife and I made it a game of guessing how large the temperature difference was going to be on thermometer in the car.

    We had our standard freezing-cold summer this year, but we were on the beach the Saturday after Thanksgiving. We spent this brilliant sunny day wading in the tide pools left by an unusually low tide. You could actually walk in the sandy beach under the cliffs where the Cliff House stands. I waded out and touched Seal Rock. The water was a couple of inches above my knees.

    Here’s a more typical low tide:

    The rock I walked out to is not in this picture. It’s straight offshore from the small building with the round turret.

  14. Not sure
    Posted Dec 16, 2007 at 11:12 AM | Permalink | Reply

    The link didn’t work last time, sorry:

    The little building with the turret is called the “Camera Oscura” BTW.

    WordPress torches the link if you don’t put text between the tags, I guess.

  15. steven mosher
    Posted Dec 16, 2007 at 11:15 AM | Permalink | Reply

    RE 14 I see sadlov in that photo getting ready to paddle out.

  16. Anthony Watts
    Posted Dec 16, 2007 at 11:23 AM | Permalink | Reply

    RE12, Not sure

    “jeez” didn’t get over the concertina wire, but when you shoot closeup through a chainlink fence with a hi-res digital camera as he did, it’s quite easy to crop a photos so that the outside diamond pattern of fence wire doesn’t show, which is what I did.

    But the photo sure looks like he made a “break in”, doesn’t it?

  17. jeez
    Posted Dec 16, 2007 at 12:06 PM | Permalink | Reply

    Given that I was walking around taking photographs of the grounds of an active US Mint, I can pretty much assume that photos of me have been forwarded to the FBI and probably already run through a facial recognition database. I don’t really have anything to hide, so it’s not a big deal. The reason that I want to remain anonymous is that I actually have an online stalker. I don’t want to lead him to this site and pollute it with his bile.

    I haven’t lived on that side of town for 25 years and was unsure of the fog line. I couldn’t remember how often it encroached on Mission Dolores, thus my missing the 1983 positive bias of moving to the Mission from the Civic Center. Mission Dolores is only 4 blocks from the Mint, but it is a different climate.

  18. Dennis Wingo
    Posted Dec 16, 2007 at 12:28 PM | Permalink | Reply


    I know what you mean about an online stalker. I have one that has made it his life’s work to follow me around and call me a crackpot for doubting the church of anthropogenic global warming. I am just glad that Steve keeps a firm hand on the wheel here.

  19. DocMartyn
    Posted Dec 16, 2007 at 1:08 PM | Permalink | Reply

    That is a liquid nitrogen heat exchange unit, as the nitrogen passes from the take it is used to heat the lipid so that some of it is converted to gas.

    what happens is that when you have a high flow rate, it gets covered with ice. Then as the flow stops, the ice melts and water forms and you get a puddle. I often look at the heat exchangers at MSU when I go for a smoke. They are covered with ice in the high of summer if there is a run on the N2.

  20. brian
    Posted Dec 16, 2007 at 1:08 PM | Permalink | Reply

    SFO is the name of the airport, not the city of San Francisco, they are separate … to say “spotting stations in downtown SFO” doesn’t make sense. The airport doesn’t have a downtown. When you say “i returned from SFO”, are you talking about the airport or the city? I don’t know of anybody who refers to the city as SFO.

  21. Anthony Watts
    Posted Dec 16, 2007 at 1:44 PM | Permalink | Reply

    Re 19 “I don’t know of anybody who refers to the city as SFO” Well I do, sorry if that is confusing. In the meteorology world we tend to exchange airport ID’s and city names in casual conversation, since airport ID’s are also used to designate weather stations on surface charts.

    For example, I often say LAX for Los Angeles or PDX for Portland.

    People call San Luis Obispo “SLO” and it’s also the airport ID. They also refer to “slo” as a lifestyle pace there.

    I added the SFO airport for comparison, the article is about the two locations for the downtown weather station. But you’re right, the airport doesn’t have a downtown. And as George Carlin once lamented about TV weather reports “Why do they always give the temperature at the airport? Nobody lives there!”

  22. Smokey
    Posted Dec 16, 2007 at 2:13 PM | Permalink | Reply

    For what it’s worth:

    Prior to my retirement, a big part of my job was calibrating temp/humidity chart recorders in a big environmental/metrology lab. The temps were recorded off a type-j thermocouple, usually onto a circular paper chart. They were pretty inaccurate. All of them. Thermocouples can be accurate, but a good 48-inch mercury thermometer with magnifier beats them handily as far as accuracy goes.

    And whereas the mercury thermometers only needed to be checked for accuracy every 3 years [and were always right on the money], thermocouple based recorders had to be re-calibrated every ninety days. Usually, they required minor adjustments to bring them back up to the manufacturer’s tolerance.

    It might be worthwhile to ask the station operators when their last calibration was performed.

  23. Larry
    Posted Dec 16, 2007 at 2:21 PM | Permalink | Reply

    21 J-type??? Who’s the Einstein who decided that J-type TCs were a good choice for ambient temperature measurement? Damn things rust. They’re good for furnaces, not ambient.

  24. Posted Dec 16, 2007 at 2:56 PM | Permalink | Reply

    How far is it to the street, stone wall with driveway and nitrogen tank?
    It should be possible to estimate these distances from Google
    Earth etc. The record should include these numbers.

  25. _Jim
    Posted Dec 16, 2007 at 3:09 PM | Permalink | Reply

    Good work guys, as always.

    On the fine details in the chart depicting the station history for the downtown San Francisco
    station I think I caught what looks to be a small typo that in no way materially affects the posting or anything else for that matter, but to be specific, Line 5 under the “Began” column -

    - the date: 7/1874 should quite likely be: 7/1864.

    Small detail but the chronology is “monotonic” with that change.

  26. steven mosher
    Posted Dec 16, 2007 at 3:22 PM | Permalink | Reply

    RE 24. you can estimate from the photo.

    Look at the fence to left. 8-9ft fence

    The railing prolly 3 foot.

    The traffic cone. 2 -2.5 ft.

    The MMTS sheild ( beehive thingy ) what is it Anthont 8 inches?

    The pipe diameters.. say 2-3 inches

    You have that tank.. 6+ foot diameter. easily.

    you got some cars parked on the street.

    Jeez what was the Focal length ( check the metadata) when you took the shot?

    That’s some forensic fun.

  27. Smokey
    Posted Dec 16, 2007 at 3:29 PM | Permalink | Reply

    #22: Certain thermocouples are designed for specific temperature ranges. Type-J’s were usually used in our dataloggers for ambient temps; sometimes type-K [which is becoming the standard for ambient]. But we used every type. For high temps [~2,000 deg F] we usually used type-R. The problem isn’t usually the thermocouple itself, it’s the fact that you need an extremely accurate voltmeter/indicator in your datalogger or chart recorder, because a one-degree change in temps only changes the thermocouple output by a matter of microvolts. My point was that the people taking the temp measurements at the stations probably lack the technical training to even understand what’s going on with their measurements. That’s why asking the guy in charge if he can show you the calibration record; and who performed the calibration; and if they’re N.I.S.T. certified would be worthwhile. My guess is they’re winging it.

  28. steven mosher
    Posted Dec 16, 2007 at 3:29 PM | Permalink | Reply

    RE 25. Jim thank you for your circumspect observation.

    Funny story. After gaining a reputation for finding other people’s mistakes, I got tasked
    with doing my own work. Of course, being semi divine, I made bone headed mistakes

    So i received this advice. “You should learn two three word sentences.”

    1. I was wrong.
    2. I don’t know.

    It will also help you if you get married.

  29. steven mosher
    Posted Dec 16, 2007 at 3:37 PM | Permalink | Reply

    Anthony.. with nearly 100% of the california stations sampled I think
    Something interesting can be done. Along the lines of Ross’ work.


  30. Larry
    Posted Dec 16, 2007 at 3:41 PM | Permalink | Reply

    26, there’s no really good reason to use a TC at all for ambient. RTDs are better, and cost the same. I think it’s just habit.

  31. steven mosher
    Posted Dec 16, 2007 at 3:56 PM | Permalink | Reply

    RE 30.. you meant #23 not #26 to make a brianesque type nit pickering.

  32. Posted Dec 16, 2007 at 4:10 PM | Permalink | Reply

    Eyeballing from the MS Virtual Earth photo Anthony linked to the mint aerial shot, it looks like the street is about 3.4m, the wall supporting the driveway 4.6m, and the tank 10.3 m, assuming I’m looking at the correct object.

    By the CRN ratings Anthony gives at, the stuff within 10m would automatically flunk it for CRN3 and put it in CRN4, where it would remain since it’s not actually on top of the offensive surfaces.

    Leroy’s Meteo France criteria are generally more tolerant than the simplified CRN criteria, in that they allow objectionable stuff near the sensor, as long as they don’t occupy too big a percentage of certain radius circles. Thus, MF category 3 tolerates up to 10% of the area of a 10m circle to be artificial heat sources such as buildings, concrete, or pavements. MF4 tolerates up to 50% of the 10m circle to be offensive surfaces, but over 50% puts it into MF5.

    Within 10m, the street occupies about 29% of the area, and the wall+driveway about 22% of the area, for a total of 51%. If I’ve eyeballed the distances correctly, that just makes it an MF5. So this is a rare case where the MF rating would be worse than CRN. The nitrogen tank is outside 10m, but surely would deserve some special recognition!

    Anthony — I sent you (and Steve) my translation a while back, but still haven’t heard from Leroy if it’s ok to put it online. Did you get it?

  33. George M
    Posted Dec 16, 2007 at 4:45 PM | Permalink | Reply

    That terrain is nowhere near flat in the vicinity of the sensors, and the auto parked adjacent probably gets run at least twice a day. And it leaves one wondering, what exactly are they trying to hide under the traffic cone? Shouldn’t anyone be driving around inside the support structure. If there is a hazard in there, yellow tape is the appropriate marking. Oh, well, it should still be accurate enough for +/- 0.01 degree data, right?

  34. Larry Shdldon
    Posted Dec 16, 2007 at 4:59 PM | Permalink | Reply

    Fly Specks in the Pepper….

    SFO is in San Mateo County.

    Frisco is in Texas, I think. (I don’t recall you committing that one, I’m just sayin’….)

    Duboce Park is in San Francisco.

    And the part of the SFO airport where the ASOS is is in a very different kind of climate from anything in the City and County of San Francisco. That end of that runway is often in Severe Clear, relatively warm weather when the other end of it is in close to zero-zero conditions and seriously cold.

  35. steven mosher
    Posted Dec 16, 2007 at 5:50 PM | Permalink | Reply

    RE 32. I’d put the tank at 24- 32 ft. as well.. looking at the fence and the distance between posts
    more toward the 10 meter end of things.. corresponding with your estimate..

  36. steven mosher
    Posted Dec 16, 2007 at 6:40 PM | Permalink | Reply

    re 34.. zero zero. could be worse, could also be crosswinds, a pitching deck and bingo fuel.

  37. Posted Dec 16, 2007 at 6:48 PM | Permalink | Reply

    According to CA’s CRU list at, SFO (San Francisco, CA, CRU # 72494000 at 37.6, -122.4) and San Francisco/Mission (CRU # 72003300 at 37.8, -122.4) are both CRU stations. The SFO station itself (at the airport, that is) juts out into the bay as shown in Anthony’s photo, but is still downwind from the increasingly urbanized San Mateo area, not to mention the busy airport itself.

    CRU’s inclusion of SFO is consistent with its proclivity for urban airports. In Ohio, for example, 7 of the 9 CRU stations are urban airports (8 of 10 if you count Cincinnati/No. KY as Ohio).

    Somehow Steve’s quick initial concordance of the CRU list identified the SF/Mission CRU listing with San Luis Obispo Poly, and the “Pine Bluff” CRU listing at 34.2, -92 (in Ark.) with SF/Dolores.

    I’d agree with Brian (#19) that SFO must be the airport itself, and/or its weather station, while the city itself would be SF.

  38. Posted Dec 16, 2007 at 7:08 PM | Permalink | Reply

    Re the mint: Cars are about 6′ wide. So scaling roughly, I’d guess the sidewalk is about 15′wide, the street about 36′wide, the tank about 35′ from the unit. The unit appears to be about 9′ from the fence at the sidewalk, 15′ in the other direction.

  39. Geoff Sherrington
    Posted Dec 16, 2007 at 7:12 PM | Permalink | Reply

    Re liquid nitrogen tank.

    I doubt if the tank has much more than sarcasm potential. The exterior would not feel particularly cold if touched. What is more serious is the subsequent use of the LN2, unstated above. Obviously it is used to cool objects and it is their distance and teleconnection with the thermocouple that matters. It’s in the economic interests of the LN2 users to minimise equipment cooling since that equates with LN2 loss and replacement bills. However, when you pump LN2 from a tank, you get cooling from expansion and often an electric or gas heater is used to keep the ice on the external pipes to a minimum, depending on the detailed design. The proximity of this device to the thermocouple is also of interest.

    I’m not defending the installation, just saying that the tank itself is fairly benign. Maybe it is used for monthly calibrations of the thermocouple. We used to use LN2 to cool beer cans, as well as cooling lithium/germanium semiconductor radiation detectors. I also managed a project where we used tonnes of LN2 a week in a process using chlorine gas at 1050 dec C to strip the iron from ilmenite to make synthetic rutile. It was used to control temperature in a fluidised bed reactor.

    I have a far greater worry about accuracy and drift of the thermocouple and the validity and frequency of its calibration. I join with Anthony’s concerns about the overall geography of the site and wish that you USA people did not vest your bad habits in the thinking in other countries. I’d be against a sub-study using California weather sites because much of the ROW thinks CA is one giant Disneyland where the improbable is possible daily.

  40. Posted Dec 16, 2007 at 7:14 PM | Permalink | Reply

    Make that 18-20′ to the sidewalk in the other direction.

  41. _Jim
    Posted Dec 16, 2007 at 7:34 PM | Permalink | Reply

    RE: LN, Nitrogen use:

    Obviously it is used to cool objects

    If I may interject for just a moment, there are other manufacturing uses for Nitrogen, at a printing facility perhaps it is used to ‘bathe’ product for a certain critical part of the inking or serial number process, perhaps it is used to preserve raw material stock (ink or raw, unprinted paper), used to replace the Oxygen and water-vapor containing atmosphere.

    Confessing now, we make use of such a Nitrogen ‘bath’ in an automated “selective solder” process to insure little to no atmosphere interferes with the solder processing on product that has just a few legacy thru-hole components.

  42. Posted Dec 16, 2007 at 7:57 PM | Permalink | Reply

    The 1983 move from the Federal Office Bldg at 50 Fulton to Mission Dolores at 16th and Dolores seems to have increased SF temperatures by a good degree or 2 C. Any idea why?

  43. steven mosher
    Posted Dec 16, 2007 at 8:12 PM | Permalink | Reply

    RE 40 Geoff, the spread between county population densities is pretty steep.
    People forget that Yosemite is here. So just google california county population density
    and you see huge spreads. THAT SAID, the ROW does view us as disneyland and they forget
    the wide uninhabited expanses up north… Nothing like you mates got however..

  44. Posted Dec 16, 2007 at 8:24 PM | Permalink | Reply

    Using the Ruler tool on Google Earth, the airport ASOS station is about 20 meters from the roadway. Since the road therefore fills about 11% of a 30m circle about the sensor (and the buildings encroach some as well), it would just fail MF category #2 (at most 10% objectionable surfaces within 30m), and fall in MF Class 3.

    However, the MF classes, like the CRN classes, take no account of the larger UHI environment.

  45. Posted Dec 16, 2007 at 8:25 PM | Permalink | Reply

    Hu, #42: an uneducated guess: Fulton is north of Market, and 16th and Dolores is South of Market. Generally speaking, the further south and east you get in S.F. the warmer it is. Additionally, the Federal Building, if I’m guessing correctly, was downtown and in an area of taller buildings than the Dolores site and therefore more prone to bias from shade.

  46. Posted Dec 16, 2007 at 8:47 PM | Permalink | Reply

    Interesting link on SF’s topography, climate and station history.

  47. Anthony Watts
    Posted Dec 16, 2007 at 8:48 PM | Permalink | Reply

    RE44 Hu I get word from former NWS SFO met Jan Null that I may have not correctly ID’d the ASOS station. The lat/lon given in the NCDC MMS Database is useless, and puts in in South San Francisco. I made my ID by eyeball.

    Null says the station is more midfield, but I’m having a hard time spotting it. Maybe we’ll send “jeez” out to walk a taxiway ;-)

    This may be it, more eyes the better:

  48. Geoff Sherrington
    Posted Dec 16, 2007 at 9:28 PM | Permalink | Reply

    Re $ 41 _Jim

    Of course you are correct, I was generalising the uses of LN2. The heater is also used to convert liquid nitrogen to cold gas, because many uses are for gas rather than liquid, which does bad things to the mechanical strength of many materials.

    For Anthony

    Two further concerns arise and they relate to Australia, where a number of High Quality sites have been selected. In the main they are at lighthouses or at small airstrips inland. I have a niggling feeling that neither choice is representative.

    Airports. Seeing the SF airport site photo (and noting it might not be the actual one now) I am worried about hot jet wash. Just how far away do you have to be to avoid it? Is the asphalt:grass ration atypical in any case, of a truly rural site? Here we have fewer jets and more small piston a/c, but the same worries apply.

    Lighthouses. So many of the Aust HQ stations are at lighthouses that if, in time, a bias effect is discovered, we are vulnerable and more “adjustments” would be needed.

    I’ve seen the fog roll over the coastal range at San Francisco and I’ve felt sudden temperature changes in the city. There is a rather active sea/land interface in SF just as there is at lighthouses in general. It’s hard to think of two classes of location so far apart in properties, for an Australian High Quality network, as isolated inland small town airports with tarmac, on one hand, and coast-hugging lighthouses, some on long peninsulas, on the other. The contrast seems to invite complications. One is moderated by a fairly constant sea temp, the other is roughed around by hot and cold winds. Anyone have experience with similar site comparisons elsewhere?

  49. Posted Dec 16, 2007 at 9:30 PM | Permalink | Reply

    In 45, I said: “I’m guessing correctly, was downtown and in an area of taller buildings than the Dolores site and therefore more prone to bias from shade.”

    This may be a stupid statement since the UHI effect of heated buildings would predominate. All I can say is that whenever I was downtown in SF, it always felt colder than other parts of the city because of the shade from tall buildings and the wind.

    The Dolores and 16th St. site was the only station in SF history that was south of Market. It also had 900′ peaks to the west which sheltered it from prevailing winds. Mt. Davidson, Mount Sutro and the Twin Peaks were all to the west. The remainder of the stations which were North of Market did not have the same topographical advantage.

    When I was living in S.F., a friend who had lived there for a very long time made the observation that San Francisco would not exist as a major city if it snowed there more than once in a decade on average. Anyone who has ever driven the streets there will understand why he said that.

  50. jeez
    Posted Dec 16, 2007 at 10:07 PM | Permalink | Reply

    RE:26 I sent Anthony multiple photos including ones from across the street with cars from which you could estimate distance to the tank, but in my opinion, microclimate and siting issues swamp any bias it may induce.

  51. Brooks Hurd
    Posted Dec 16, 2007 at 11:29 PM | Permalink | Reply

    Re: 21
    Not exactly on topic, but SLO is not the aiport ID for San Luis Obispo. Is is SBP.

    DocMartyn is correct about the aluminum vaporizers on the LIN tank. Regardless of the amount of ice buildup, these vaporizers will reduce the temperature of the air around them. In this case, the photo shows the vaporizers to be somewhat downhill of the temperature station. Since cool air falls, the effect on recorded temperature would be minimal unless the prevailing wind direction were from the direction of the LIN tank.

  52. TomSF
    Posted Dec 16, 2007 at 11:34 PM | Permalink | Reply

    Re: 42/45/49

    From my location in Noe on Dolores and 25th I can regularly see the fog roll in and blanket various areas of the city, including downtown. I am in one of the last areas to get fogged in, and 16th and Dolores is almost as well protected from the fog by Twin Peaks to the West.

    50 fulton is in the civic center/tenderloin area, which isn’t protected by Twin Peaks to the west and thus gets fogged in sooner from fog that basically rolls through Golden Gate park, up over the slight rise around Masonic and then pours downtown. A topographical map and mental visualization of fog piling up from the west and then spilling over successive hills is probably the best way to explain the SF micro-climates.

  53. Dan White
    Posted Dec 16, 2007 at 11:55 PM | Permalink | Reply

    Well, nobody has done it yet, so I’ll give it a shot. Here’s a graph of the Mission Dolores temp trend with station move dates overlaid:

    Looks like some funny stuff there.

  54. Dan White
    Posted Dec 17, 2007 at 12:04 AM | Permalink | Reply

    OK, so I uploaded a jpg image to my website and used the Img Quicktag to dump the image into my post above, but it didn’t work. Can anyone tell me what I’m doing wrong?

    You can go here in the meantime to see the graphic:


  55. Posted Dec 17, 2007 at 7:26 AM | Permalink | Reply

    RE 53, 54, the link in #54 works OK. It looks like the SF heat wave of ’83 was essentially reversed in ’97 when the site moved to Duboce Park. Is this back in the Fog Zone?

    Another possibility is that when they moved it they either used a new MMTS unit, replaced the housing, or at least cleaned the old one. Here (I hope) is a picture of an otherwise well-maintained MMTS that has been in the field at Circleville OH since 1984:

    If it doesn’t appear, here’s the link:
    A little Fantastic and a rag would probably lower temperatures there by 2 dC as well! In California, eg Marysville, the MMTS soil buildup tends to have a tan clayey color rather than this black mildewey color, but either should affect measured temperatures.

    Apparently both Dolores and Duboce Park were rooftop sites. Does anyone know where at Dolores Mission the sensor was? Google Earth shows a nice old mission at Dolores and 16th, but with modern tar roof buildings behind it that appear to be part of the complex, and that might have held the sensor.

    I don’t see anything wrong with the source code for your post when I select VIEW>VIEW SOURCE, so I don’t know why your image didn’t come up.

  56. Posted Dec 17, 2007 at 7:39 AM | Permalink | Reply

    Howzit the “airport” has readings back to 1880? Was there a hot air balloon launchpad at the same site before airplanes??

  57. Posted Dec 17, 2007 at 9:22 AM | Permalink | Reply

    Perhaps there was an amateur meteorologist in the Mills Familiy?

  58. Posted Dec 17, 2007 at 9:27 AM | Permalink | Reply

    Btw, in case you missed it, there’s an excellent map of historic SF station locations at the very bottom of the link in #46. It’s down below the footnotes.

  59. George M
    Posted Dec 17, 2007 at 3:06 PM | Permalink | Reply

    Anthony – 47
    I don’t think that is it. Unless it was recently relocated. If you step around the other 3 directions of view, it is not present in some other photos, indicating a new structure. My suggestion is to look near the FAA radio antennas on the little bulge of land near the intersection of the taxiways for 19L and for 28R.

  60. Anthony Watts
    Posted Dec 17, 2007 at 4:09 PM | Permalink | Reply

    RE59 George M

    Thanks for the help, here is the true location of the SFO ASOS station…just north of the original location I mentioned.

  61. George M
    Posted Dec 17, 2007 at 5:05 PM | Permalink | Reply


    Yep, that’s the location I was attempting to describe.

  62. Russ
    Posted Dec 17, 2007 at 6:25 PM | Permalink | Reply


    The link takes me to sign in search page. Tried pasting in the link, same result.


  63. Posted Dec 17, 2007 at 6:49 PM | Permalink | Reply

    Russ: works for me. Are you sure you’re giving it enough time to load?

  64. Russ
    Posted Dec 17, 2007 at 9:45 PM | Permalink | Reply


    Interesting, it will not work in Safari, but will in Firefox. I got the picture.


  65. Smokey
    Posted Dec 18, 2007 at 1:24 PM | Permalink | Reply

    64: I got the pic in Safari. The reason may be that Safari just had another update.

  66. Posted Dec 18, 2007 at 2:34 PM | Permalink | Reply

    Anthony’s SFO picture (#60) has a scale on it, but is taken at an angle so there is a lot of parallax. I found the same site taken vertically on Google Earth at 37deg 37′ 10.58″N,
    122deg 21′ 56.16″W (to the central structure), elevation 1 ft. I hope that’s above high tide!

    It looks like the ground cover is barren landfill with no pretense of grass, which makes the site a Class 5 on either the simplified CRN or more complicated Meteo France scales. But just in case all that gray stuff is natural sage brush, it’s worth taking some measurements. Using the Google Earth ruler tool, it’s about 26m to the paved service road, and 32m to its far side. The runway begins at 49m, at it is at least 129m to the far side. The little dead end road is at 36 m, the corner of the 16X4m building is 51m away, the bay is at 93m, and the riprap (stone shore cover) is 78m. (Water surfaces are as bad as concrete or asphalt in Leroy’s MF system.)

  67. SteveSadlov
    Posted Dec 18, 2007 at 5:30 PM | Permalink | Reply

    RE: #15 – Yar dude!

  68. SteveSadlov
    Posted Dec 18, 2007 at 5:35 PM | Permalink | Reply

    RE: #66 – The grey is native adobe (the whitish portions are caliche). The dul green is a mixture of (human attenuated) sage, tumble weeds, gamma grass, Spanish non native oat grass and plain old weeds. Climate along many areas along the west shore of the bay is semi tropical semi arid to arid – due to the double whammy of subsidence down the leee slope of the Santa Cruz Mtns / foothills and the bay itself.

  69. George M
    Posted Dec 18, 2007 at 10:08 PM | Permalink | Reply

    Here is another good example of a unpredictable moving target. Google, Live Local, and Mapquest all have different satellite photos, and those 3 and the four Live Local “Bird’s Eye” views all show ground cover of slightly different color and extent. This indicates to me that the albedo changes with season, and who knows what else. How do you “adjust” for that?

  70. SteveSadlov
    Posted Dec 18, 2007 at 10:42 PM | Permalink | Reply

    RE: #69 – This climate (Southern half of NorCal) has extreme seasonality of precip. It is a rare example of a wet dry climate outside the tropics. Unlike the tropical wet dry climates we get our rain during the colder half of the year. Once those rains hit, even the most desolate looking caliche will start to grow short bunch grasses and weeds. We have two seasons green and brown (it’s green now).

  71. Posted Dec 19, 2007 at 10:21 AM | Permalink | Reply

    George M (#69) wrote,

    Here is another good example of a unpredictable moving target. Google, Live Local, and Mapquest all have different satellite photos, and those 3 and the four Live Local “Bird’s Eye” views all show ground cover of slightly different color and extent. This indicates to me that the albedo changes with season, and who knows what else. How do you “adjust” for that?

    The spaces between most of the runways look very different than the little peninsula with the ASOS, in that they appear to have at least some semblance of grass. Leroy’s Meteo France memo requires stations to be in a cleared area covered with either grass less than 10cm high, or else low natural vegetation. It’s understood that this vegetation will vary in albedo with the season.

    Although a pad of concrete or gravel (or even this adobe) directly under the sensor would flunk the station by CRN standards, it is OK for the MF classes, as long as it doesn’t exceed a certain small area. This sea of adobe clearly is too much. If the sensor were instead between the runways and 100m from the nearest runway, it would actually be MF Class 1, but only because these classes don’t take into account the larger UHI setting.

    It would be interesting for someone (not me) to take say the US portion of the CRU list that Steve posted at, which includes both these SF stations along with many other urban airports, and compare the average of all stations to the small subset that are known to be reasonably situated. Ideally this should be done for the whole world, but for now we know a little more about US stations.

  72. SteveSadlov
    Posted Dec 19, 2007 at 1:24 PM | Permalink | Reply

    RE: #71 – Watts has a post on his blog about UHI in Cal urban areas, based on a state run study. Might be able to leverage some of that. The study clearly demonstrates the impact of the massive UHI dome / plume due to the 7M people and their stuff associated with the Greater Bay Area sprawlurban zone.

  73. Posted Jan 18, 2010 at 5:54 PM | Permalink | Reply

    I say get the kids involved in learning about climate change. One way to do it is via fun, educational experiments that you can do at home. Here’s a nifty list with directions

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