WUWT reader BarryW found this on the Huntsville Office of the State Climatologist, operated by our friend, Dr. John Christy and left it in Tips and Notes. First Christy’s article, then the report on the rabbit hole my investigation sent me into. There goes another afternoon chasing a weather station.
I’m glad I don’t live at the airport
Scientists are puzzling over why temperatures at the Huntsville International Airport are routinely warmer than temperatures in surrounding communities.
During the summer of 2010, daily maximum temps at the airport’s automated weather station averaged more than one degree F warmer than other stations in North Alabama. That included some relatively urban stations, such as the one at UAHuntsville. The airport thermometer has been tested and is accurate, so the question now is whether airport expansion has created an isolated “heat island.” That could mean data from the HIA station is no longer representative of the larger area and has reduced value for tracking both local weather and climate change.
So, the first thing I did was look up some history. It seems the station has been moved around a bit.
Stations used to populate the new database for Huntsville
Though observations begin in 1894 at Madison (014976), information from station history files indicate thermometers were mounted on the north side of a residence until probably 1906. In Feb. 1907 the first reference to the use of a cotton region shelter (CRS) is documented, so it was decided that the POR for temperatures should begin at that point. The POR for precipitation will be 1894.
For the most part, all Madison observations were taken in large, rural yards of homes on Church St., with the CRS usually positioned on grass at least 7 to 15 m from any structure. The longest single site was that of the Carter family who observed from 1917 to 1950 from the same location, providing an exceptionally consistent record during the period of significant warm temperature extremes of the 1920’s through the 1940’s. All Madison observations were taken in the evening except for a period in 1911-1914 and 1950-1962.
Observations of temperature and precipitation began in 1937 for the then small town of Huntsville on the property of the electric utility company (Alabama Power Corp., 1937-1940, Tennessee Valley Authority 1940-1941). All daily summaries from this station are based on midnight observations. The station was moved on 21 Feb. 1941 to a rural crossroads just south of the city limits, being less than 2 km from the original utility company. On 21 Nov. 1945 the site was moved to the Huntsville Municipal Airport, about 6 km south of the original site. All sites appear to be open and unobstructed. The airport station was closed 14 Jul 1954, though indications exist that the weather station was indeed operating for aviation puposes.
Huntsville (014064, KHSV)
The Weather Bureau commissioned a station at the Huntsville Municipal Airport in 1958 on the same site as the previous station. It was moved short distances in late 1958 and 1964. On 29 Oct 1967, the station was moved 17 km WSW to the new Huntsville-Decatur International Airport where observations continue to this day. The most significant event since 1967 was the commissioning of the ASOS in 1994 at its new location over 1 km W of the airport offices.
Period of Record
The Madison stations (014976) were all located at a distance of about 6.5 km and within an elevation of 20 m of the current KHSV ASOS. Indeed, the comment made on WS Form B-44 regarding the closure of Madison when the latest observer died was “This station located [near the] WSO/Huntsville. Station no longer needed.” Thus, geographically, the Madison stations would be viewed as compatible and consistent with KHSV.
The early Huntsville stations of 1937-1945 (014068) were located about 20 km NE of the present KHSV ASOS before moving to the Municipal Airport in 1945 at 18.1 km ENE from the ASOS. The entire set of 014068 stations taking observations during 1937-1954 were compatible and consistent as indicated by a single station ID and that their largest separation was less than 7 km. The fact the newly commissioned Weather Bureau station (014064) began operation on the same site as the final station of 014068, certainly makes it compatible with 014068. All 014064 and 014068 stations were within 15 m elevation of the present ASOS.
The 1967 move from the Municipal Airport to the new airport was significant (17 km), however with virtually no change in elevation, latitude or surrounding topography, the 014064 stations could be considered as a set of continuous records.
This provides a combination as follows:
Madison (014976) — 02/01/1894-12/31/1936
Huntsville (014064) — 01/01/1937-07/14/1954
Madison (014976) — 07/15/1954-08/31/1958
Huntsville (014068) — 09/01/1958-present
NWS Huntsville History (click on the images for annotated enlargements)
The history of weather observing in Huntsville dates back to the some of the city’s earliest years of existence. The earliest documented observations began in January of 1831 at an unknown location in the city and continued to be taken until December of 1839. Observations briefly resumed at another unknown location in June of 1871. These lasted only until August 31, 1877.
Steady observations in the Huntsville-Madison County area didn’t begin until 1894, when a cooperative observing site was established in Madison. The thermometer at this site was situated on the north side of the porch, so the readings were probably unreliable. However, precipitation data recorded at this station was considered valid, and it is a part of the climatological record. In 1907, the site was moved to the Klish residence. This station was equipped with a Stevenson Screen enclosure for the thermometer. The station moved again several times – in 1911, three times in 1912, in 1916, and in 1917 – all to locations in the same vicinity. Over this time period L.S. Hagar, R.A. Patton, J.B. Stevenson, Edward Humphrey, S. Fletcher Bradley, and James Landers were listed as observers.
On March 19, 1917, Mr. Thomas Carter, who lived on Church Street a quarter mile south of the Madison Post Office, took over official observations. This site continued to operate until observations resumed in the city of Huntsville in 1937. Mr. Carter’s nearly continuous daily evening observations spanned some of the hottest months in the history of the state, including the summer of 1925. In September of that year, the high temperature was 100 or greater on 12 days! The hottest day was the 7th, when the temperature reached a balmy 108 degrees. The Carter family continued taking observations in the Madison area until April of 1950.
Observations Begin in Huntsville
On January 1, 1937, observations resumed in Huntsville at the Alabama Power Company building. This station was located less than a mile southwest of the post office on Canal Street. In 1940, utility operations in Huntsville were bought by the city and contracted to the Tennessee Valley Authority. Observations continued at the same location until February 21, 1941. As a part of a significant road renaming project in Huntsville in 1958, Canal Street became part of Lehman Ferry Road, which was later renamed Leeman Ferry Road. Most of former Canal Street no longer exists, but part of it still does and is now known as Woodson Street. The old TVA building still stands there near the intersection of Clinton Avenue.
At this point, the site was moved to a Texaco Station owned by Mr. Joe E. Cambron. The station was near the intersection of US Highway 241 and state highway 38. (Neither of those highway numbers are used today. US 241 followed what is now Meridian Street north out of Huntsville and what is now US 431 over Monte Sano. State Highway 38 followed what is now Whitesburg Drive and U.S. 231 toward the Tennessee River). According to Alabama State Climatologist John Christy, there is now a Taco Bell where the Texaco station used to be. This would place the station near the present-day intersection of Whitesburg Drive and Longwood Drive. This station took 24 hour readings until November 21, 1945, when observing responsibilities were shifted to the Huntsville Municipal Airport.
In 1941, weather observing equipment was installed at the new Huntsville Municipal Airport (now known by many locals as the “old airport”), which was located on the south side of town. A survey of the placement of the equipment was completed by a local engineer named Carl T. Jones (whose namesakes include “Carl T Jones Drive” and “Jones Field” in Huntsville). It wasn’t until November of 1945 when this site became the official Huntsville observing site. It was classified at the time as a “Synoptic and Aviation Reports” (SA) station. According to a Weather Bureau Station Record document dated April 15, 1946, airways observations were transmitted via P.C.A. teletype to Chattanooga and 6-hourly observations were called long-distance to the Weather Bureau Airport Station (WBAS) in Chattanooga. Some of the observers at the Huntsville Municipal Airport during this time period were Harold Hudson, James Hudson, and Bud Cramer, Sr., father of the future United States Representative for Alabama’s 5th district.
The weather station at the Huntsville Municipal Airport ceased operations on July 15, 1954. At this point, the station became classified as a Supplementary Airways Reporting Station (SAWRS). However, there are many records that indicate the weather equipment was still functional and used for aviation purposes. Also during this “dark period”, some of the observing equipment was moved to a newly-constructed tower cabin at the airport. When this move was made on August 16, 1957, the station was reclassified as a Civil Aeronautics Administration (CAA) station. Because observations from this time period do not exist for Huntsville, data from Mr. Harry R. Taylor’s cooperative weather station in Madison (no more than a couple miles from the stations used in the late 1800s and early 1900s) are used as Huntsville’s official readings during this time.
Huntsville’s First Permanent Office
Prior to the establishment of Redstone Arsenal, Huntsville was only a small textile and farming town. This changed rapidly in the 1940s and 1950s, when the military base came to town. Along with the influx of new jobs came new people and increased air traffic. At this point it was decided that Huntsville would receive its own Weather Bureau office. The office was originally scheduled to open on October 1, 1958, however, the new building had not yet been completed by then. The new office was in a building that was part Weather Bureau office, part hangar. According to a Huntsville Times article from October 1, the office’s new staff used the tower of the airport terminal as temporary quarters, where they began limited operations before the official opening of the office by the end of the month. Hubert Bagley (more notoriously known in the Huntsville area as the late H.D. Bagley) was charged with coordinating the construction of the new office and installation of new equipment, such as teletype machines and communication lines. The office’s first Meteorologist-In-Charge (MIC) was Baker B. Williams, who transferred from WBAS Okalahoma City. He was accompanied by a staff of seven others including Bagley, Wilburn K. Cobb, James J. Corcoran, Alfred Eisgrau, Lacy B. Padgett, Anthony M. Smith, and John W. Taylor. The office was equipped with a 44 foot tall WSR-3 radar, which had a range of up to 200 miles (though it wouldn’t have been very effective at longest distances in that range). The new office’s area of responsibility was “Huntsville and a 25-mile-radius including Redstone Arsenal” when it first opened, according to a Times article dated October 31, 1958. At first, forecasts for the Huntsville area originated from the district forecast center at the U.S. Weather Bureau in New Orleans and were refined by the Weather Bureau office in Birmingham. For a short period thereafter, Alabama fell under the district forecast center in Atlanta, but Birmingham still had the responsibility of touching up the local forecast. Surrounding WBAS offices were located in Birmingham, Nashville, Memphis, Chattanooga, and Atlanta at that time.
The Weather Bureau office continued operations in the 1960s at the Huntsville Municipal Airport, which was renamed the Huntsville-Madison County Airport. On July 13, 1965 Congress passed President Lyndon B. Johnson’s “Reorganization Plan No. 2 of 1965,” which combined the Weather Bureau, the Coast and Geodetic Survey, and the Central Radio Propagation Laboratory to form the new Environmental Science Services Administration (ESSA). The ESSA was still under the Department of Commerce, and the purpose of the U.S. Weather Bureau was not changed.
Same Office, New Location; Then, New Name
As Huntsville continued to grow, so did the need for a larger airport to faciliate the increased amount of air traffic in and out of the city. In 1967, a new Huntsville-Madison County Airport was opened in far southwest Madison County. The Weather Bureau moved along with the airport, and began operations at the new location on October 29, 1967 – almost exactly nine years to the day it began operations in Huntsville. Mr. Williams was still in charge of the office at the time of the move.
In 1969, the Weather Bureau transitioned to the concept of there being a forecasting office for each state, rather than one district office forecasting for several states. Birmingham became the state forecast office for Alabama and portions of the western Florida Panhandle. While the Huntsville office did not produce any forecasts from scratch, the local office did have authorization to make adjustments to the first period of the local forecast as needed.
The article on the state climo office website says they checked out the sensors, and that they were OK but wondered ‘…so the question now is whether airport expansion has created an isolated “heat island.”‘
I figured this should be easy to figure out looking at timeline imagery in Google Earth, which would show the change in the airport surroundings. So, I set out to locate the ASOS station. My first visit is to NCDC’s metadatabase (MMS).
(logon as guest)
The lat/lon is what I needed, but I also found this description interesting:
Gently rolling farmland at an airport?
When I pulled up the imagery in Google Earth, it was right where it said it should be:
I pulled up the birdseye view in Bing Maps using the lat/lon also:
I thought it was curious that the Google Earth map and the Bing Map images both showed a brown field surrounding the ASOS little sea of grass. This was farmland according to the NCDC metadata, so surely it must be in use?
I figured I’d see seasonal differences in the farmland once I used the Google Earth timeline feature to look at older aerial photos. Surprisingly, I didn’t find this to be the case, here’s a couple others:
I noticed that most of the new airport development in the last ten years was on the east side of the airport, over a mile away from the ASOS. The area around the ASOS seems to have had little developmental change.
But, I thought it odd that every photo I looked at had that tiny little island of green surrounded by the sea of brown. I was beginning to wonder if the field was fallow. Even it it was, we should see some weeds turning green in the spring like we see on the right side of the photo. It was also possible these images caught the field just before planting (freshly tilled) and after harvest, in which case both would be brown.
So I decided to look at zoomed in view to determine if the field was being worked.
I found evidence of change from 2007 to 2010, looking at the till or mow lines (I couldn’t tell which) but I also got the distinct impression that in the 9-05-2010 image, the field was fallow, due to the incursion of what looks like bushes in the right side of the image, along with what looks like a flat area, with till line erasure, likely due to mud settling in a low area that collected spring rains. My impression is that the field was fallow in the summer of 2010, with the brown albedo surrounding the Huntsville ASOS station throughout the entire summer.
I had one other place to look, Google Street view:
I was surprised to find that the area around the ASOS station was brown as well. Unfortunately, I have no way to tell what the date of the image is, since Google does not provide image dating for street view (that I can find). But it sure looks to me like a plowed field left fallow. I know that the Google Earth Street View feature was launched on May 25, 2007, and didn’t get full coverage for a couple of years after that…so I know the image is somewhere less than 5 years old. Given the color of the grass along the roadway, I’m guessing wintertime.
But, it seems clear that this field is not being worked, and the settled area and bush incursion in the late summer 2010 closeup image above suggest it was fallow during the summer of 2010…when the discrepancy with other nearby stations was noticed.
I think the discrepancy was due to soil albedo. As any glider pilot can tell you, a freshly plowed field generates a lot of heat (and a big updraft).
This table of soil albedo tells the story.
In the table above, lower values absorb more incoming solar energy, and thus release more LWIR at night as well.
This image from 2010, suggests a moist, wetter, darker soil, one of the lowest albedo values in the table above. The green grass suggests summer.
The Google Earth view shows the ASOS behind the airport fence, so I’m guess that in order to till and plant the field, some notice of access is required to the airport authority. I’m thinking that all Dr. John Christy has to do now to confirm my theory is to ask the airport authority if they can provide status of mowing/weed control/tilling or other activity in that filed and we’ll have our answer about why the summer of 2010 was so different at the airport, even though the sensors check out.
We may have a case of a “Farming Heat Island” – FHI.
Dr. Roger Pielke Sr. has been suggesting that land cover/land use change has a big of an impact as CO2 driven change if not more, I think here we have a prime example of this.
If anyone lives in/near Huntsville, a photo from that location on the road west of the runway (County Line Road) to tell us if the field is being worked would be helpful, but be mindful of airport security when taking photos.