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. The next morning at my hotel, I checked the NCDC 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.

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 micro-climates 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.