How not to measure temperature, part 69

Two weeks ago I posted about a story from the Orange County Register titled Urbanization Raises The Heat in Orange County. It was front page news that day, on Friday, August 8th.

The article was fairly well written, citing JPL climatologist Dr. Bill Patzert who also was the source on a  previous story we examined looking at the problems associated with the move of Los Angeles official weather station.

The focus of the OC Register article was the temperature record from the Santa Ana Fire Station, which has a COOP-A station # 047888 located there. The record extends back to 1916:

Examining the upwards trend in the Santa Ana record, the article touched on one of the most common reasons for temperature increase in large cities, the Urban Heat Island effect, or “UHI”. Curiously, some scientists, such as Parker in 2006, have gone to great lengths to discredit UHI as being “negligible”, even though it clearly is not. The National Weather Service recognizes it as real as evidenced by this quote in the OC Register article:

“Santa Ana now has a lot more buildings, parking lots and streets, which absorb and hold heat, some of it through the night,” says Ivory Small, science officer at the San Diego office of the National Weather Service.

In fact, the National Weather Service includes the UHI factor in one of it’s training course ( NOAA Professional Competency Unit 6 ) using Reno, NV and Baltimore, MD as examples. The Reno station had to be moved because it was producing an erroneous record, and the Baltimore station has so much bias (because it existed on a rooftop of a downtown building) that they simply closed it in 1999.

Since nothing was mentioned in the OC Register article, apparently Bill Patzert at JPL, Ivory Small at the San Diego NWS office, and reporter Gary Robbins of the Orange County Register simply don’t know how much the Baltimore USHCN station, seen below, has in common with the Santa Ana Fire Station.

Baltimore USHCN station circa 1990’s photo courtesy NOAA, click for more images

Like the now closed Baltimore weather station, the Santa Ana Fire Department weather station also sits on a  rooftop downtown. But there’s more to it than just that. Read on.

As luck would have it, the day after the article came out in the OC Register, I was scheduled to fly to Orange County to attend my sister’s birthday party. The Santa Ana Fire Station was only a couple of miles out of my way, not far from UC Irvine, so I made a detour to survey the station.  Ahead of my visit, I had checked the NCDC MMS Station database to determine what type of equipment was present, and it indicated the old style Stevenson Screen. Some early investigations using Google Earth and Microsoft Live Maps suggested the station might be on the roof of the fire station, and there was a box that could be the screen, but we couldn’t actually tell from the photography. The only way to be sure was to go there.

When I arrived at the fire station Saturday afternoon August 9th, there was no sign of a weather station from ground level:

I rang the buzzer at the front door, once, then several times. No response.

So I started looking around to see if I could get a different vantage point. I walked north to the end of the municipal parking lot across the street, and stood on a low wall, and I saw it:

The Stevenson Screen was visible just above the roofline of the lower roof. I looked around to see if I could get a better vantage point, and saw a stairway to an outdoor restaurant balcony about 50 yards to the east. So I made for that.

To my surprise, when I reached the balcony and focused my camera, I saw someone taking a reading at the Stevenson Screen. This was at 4:15 PM, which is close the the Time of Observation listed for this station at NCDC MSS of 1600 hours (4PM)

Face blurred to protect identity – note the York A/C unit nearby.

So I was in luck. Somebody was at the fire station. I went back to the front door and rang the buzzer again. And waited, and rang, and waited. I knocked on the door and shouted “hello!”. No response. I found this really odd. The front door was locked, and nobody responded to the buzzer. Finally, out of options, I picked up the red phone next to the door buzzer which said “for emergencies”, grimacing as I did so.

The operator answered, and I explained who I was and what I was there for. I asked to speak to the person in charge of the weather station, mentioning that I had just seen the person on the roof at the station. I got put on hold, and after about 5 minutes the operator came back. Another 5 minutes passes, and finally somebody comes to the door. I explained again, and he said “I’m low on the totem pole, and I can’t help you, we’ll have to ask the Captain.”

So he leads me into the equipment bay, where the engines are parked. This is the garage behind the roll up doors in the picture. It’s easily 100 degrees F in there, and I’m working up a sweat just standing there. The Captain comes out of his office and I give him my card, and explain why I’m here yet again. Chain of command requires an explanation at each level.

I mentioned the OC Register article and the Captain noted that he’d heard about it but hadn’t read it. I explained that all I wanted to do was get 4-5 photos on the roof, and it would take 5 minutes or less. He said, “I’ll have to check with the Chief”. So he goes to his office off the equipment bay, and makes a phone call to HQ. Meanwhile me and the “probie” that let me in are standing in the equipment bay outside his office door, sweating like pigs in the heat.

The Captain returns 5 minutes later and says “Chief says the roof is a restricted area, I can’t let you up there”. I understood, since 9/11, lots of fire stations and other government centers are off limits to the public now. But I had an idea, and said “Ok I understand that I’m not allowed up there, how about if you send the “probie” up to get pictures for me?

He hesitated, and then I said “This is a public facility, and aerial photographs already exist of the roof, you can see them on Google Earth. How can this be any different?” He relented and said, “I’ll call the Chief again and ask.” So me and the “probie” are standing again in the equipment bay. I’m sweating profusely, so is he. He apologizes about the heat and says, “only the office and barracks have a/c”. Meanwhile I start humming the Jeopardy 10 second tune in my head, hoping the Chief down at HQ isn’t too irritated by now.

The Captain comes out of the office and says, good news, “Chief says I can have one of my men take the photos… ” and just at the moment, the alarm rings. Guys start sliding down the pole, and the Captain yells, “I’ve got to go on this run, come back later!” and points at the door.

Great.

I walk out the roll-up garage door, the trucks roll, and I’m left standing on the sidewalk back where I was 30 minutes ago. I figured my chances were shot now. Time was running short, I had a surprise birthday party to attend in about an hour. So I got in my car, and prepared to leave. I drove to the rear (south side) of the fire station, hoping that I could get another angle of the rooftop station at least, and I was lucky to find a gap between buildings where I took this picture below:

See a corresponding aerial view from the South here

I got the photo, packed up my camera gear, and got in the car heading South on Main Street towards my destination. As I was driving, two fire trucks passed me headed north, with no lights or siren. I thought to myself “maybe it was a false alarm, could I be lucky?”

So I headed back to the station, and sure enough the engines were backing in. The Captain was on the sidewalk looking around for me. I waved, parked the car and headed in. He produced the “probie” again, and I showed him how to work the camera explaining the kind of shots I needed. He headed off up the stairs, and I spent some time explaining the www.surfacestations.org project to the Captain. When I asked about the station history, he mentioned that “nothing much has changed up there since the station was built in early 1950’s”.

“Probie” came back with the camera, I checked out the photos, thanked them both profusely, and headed off to the surprise party.

Here is one of the photos taken on the rooftop. This is looking North towards downtown Santa Ana:

Click for a larger image

For seasoned readers of this blog, it is immediately obvious that the station is surrounded by at least 3 air conditioner units, all of which produce warm exhaust air. So adding those potential effects to the rooftop effect, it hardly seems like an ideal environment for measuring temperature accurately.

But there is something else, and this is something that is clearly out of specifications for Stevenson Screen placement at NOAA Weather Stations: The screen access door is pointed west, instead of north. Which is the specification that has been in place since the Stevenson Screen has been put into use by the U. S. Weather bureau in the 1890s. The orientation of the screen, north to south, is important so as to prevent direct sunlight entering when the door is opened while the observer takes a reading or does maintenance.

And as we see from this photo, direct sunlight does indeed enter the screen when the door is opened:

Click for a larger image

Depending on the time of the day, and the time of the year, sunlight may in fact hit the thermometers themselves. We have no way of knowing how much positive bias to the Tmax thermometer this orientation error may introduce for several reasons:

• We don’t know how long the door stays open, this may change with observer
• We don’t know how long the screen orientation has been wrong or when it started
• We don’t know the magnitude of sunlight on given days at this location. They don’t have a sunlight recorder nor do they make records of cloud cover.

So add these uncertainties in the measurement, to the rooftop location, the air conditioner units, changes to the roofing surface or building over time, and it becomes clear that we have an uncertain temperature record that is not only affected by nearby land use change, such as the addition/removal of buildings, streets, and nearby parking lots, but we also have all these microsite effects which are unaccounted for.

Clearly the land around the station has changed. Here is a photo of the original Santa Ana Fire Station around the turn of the Century. I snapped this photo in the lobby of the current fire station on my way out:

Click for a larger image

See all images from the Santa Ana Fire Station here

Notice the orange trees behind the station then.

I wonder if any of the people involved in the original OC Register article know of the issues surrounding this station? Surely if the NWS knew, they’d change the screen orientation to be compliant. It appears that the current equipment has been here for a long time, because the placard on the top of the Stevenson Screen says “U.S. Weather Bureau” and it has last been called that in 1967. So clearly the screen predates that.

Click for the source image

Or maybe they just don’t care there at the NWS San Diego office, after all they have other temperature measurement stations on the rooftops of fire stations. Like this one in Coronado:

Photo from NWS San Diego, showing MMTS sensor click photo for larger image – full story here

Sure there will be those that argue that these sorts of nuances in thermometer exposure “don’t matter” or can be adjusted for. But as we’ve seen time and again the adjustments, such as those done by NASA GISS use a broad brush, and don’t take these sorts of microsite exposure issues into account on any level.

To get an idea of the potential problems involved, here is a paper that goes into minute details about exposure biases in the Australian BoM surface station network

http://www.geocities.com/CapeCanaveral/Hangar/6021/paper.html

Clearly, Santa Ana is warming. But how much does the record reflect all of the various problems highlighted above and how much of it is the true climate signal?. The answer is by no means certain.